THE 1930 LONDON TREATY AND ITS CRUISERS
Cruiser Policy in the Wake of the Geneva Conference
With the collapse of the Geneva Conference, the British government pressed the Admiralty to develop a new policy which might be acceptable to the Americans. The Admiralty now proposed a split into categories A and B (8,000 tons), each capable of mounting 8in guns, of which the A type would still be limited.1 C-in-C Mediterranean (Admiral Sir Frederick Field) and others argued that for fleet work 6in cruisers were preferable to 8in for pressing home torpedo attacks and for breaking up enemy torpedo attacks, due to their greater volume and rate of fire and their greater handiness. They were also better adapted to night screening and to shadowing, because they had much smaller silhouettes. He envisaged the A and B types as a way of meeting enemy 8in cruisers in a fleet action, as a striking force, and as a way of controlling the Fleet Area (in the First World War, the North Sea). The Staff College proposed a fleet of twenty A, fourteen B, and thirty-six G, of which the G cruiser would be armed with eight 6in guns, steam at 33.5kts (with 30kts written in pencil), and cost £1.2 million (First Sea Lord thought, correctly, that this was a lot to hope for on the tonnage and cost). For the Staff College, the large force of G cruisers was a way of holding down costs, justified by the claim that some could be used on the safer trade routes and to protect convoys against armed merchant ships. To First Sea Lord, this independent investigation demonstrated the wisdom of the British policy at Geneva. Madden also pointed out that new conditions would make surface raiding more difficult.
In October 1928 the Head of the Tactical Section (Captain Bruce Fraser) circulated a paper on the use of a small 8in cruiser, in effect a test of possible post-Geneva policy. A modern fire-control system needed at least four guns to produce adequate salvoes.2 At one end of the scale was the minimum 8in cruiser with the facilities of an A or B Cruiser (Type I). At the lower end (Type II) was a ship equivalent to a small 6in cruiser but armed with four 8in guns, which were considered superior to six 6in. At this time the requirements of the small 6in cruiser (Leander class) were being developed (see below). They amounted to a minimum displacement of 6,000 tons, endurance 7,000nm at 16kts, speed 30.5kts deep and magazine protection against 6in fire. Type I would have the same role as A and B Cruisers, with the fleet and on trade routes, ‘but naturally with a lower standard of performance’. Type II would operate with the fleet, but would be handicapped by the poorer performance of her 8in guns against enemy destroyers. On trade routes, her 8in guns would give her a considerable advantage, it seemed, over enemy 6in cruisers, despite her light protection. Director of Plans (Captain R M Bellairs) was less than enthusiastic: the point of the small cruiser was to be less conspicuous, handier and able to develop a rapid yet sufficient fire, but neither Type I nor II seemed to offer these qualities as well as a 6in cruiser. Bellairs concentrated on the role of the cruiser within the fleet; any virtue these ships might have in trade protection was secondary. For DGD, because a 6in cruiser would be considerably overmatched by a ship with four 8in guns, ‘it is therefore essential to ensure by legislation or otherwise that we shall not find our 6in cruisers pitted against small 8in cruisers’. If that could be done, 6in cruisers would enjoy clear advantages because they could be built in greater numbers.
HMAS Sydney in Melbourne, 9 November 1936, with her long catapult installed, and with four single 4in guns. (Photo by Allan C Green via State Library of Victoria)
Ajax as fitted, April 1935. When the 46ft catapult was fitted, one Fairey Seafox was stowed atop it and a second athwartships (nose to port) on the after deckhouse between the boat skids. The ship was originally to have carried two Hawker Osprey floatplanes, spare floats for which could be stowed forward of the funnels. The two 27ft whaleboats were carried on light portable davits outboard of the 4in guns when the ship was in port. The forecastle deck plating was extended aft when the ship was rearmed with twin 4in guns in 1938, and the masts were later replaced by light tripods. (A D Baker III)
In theory, the design of the 6in gun Leander class left open the problem of trade protection, for which it seemed 8in guns were needed. The Admiralty reviewed the issue at length in 1928.3 The big cruisers were clearly unaffordable. The Staff College suggested building less expensive 6in cruisers to protect trade in less dangerous areas, while Controller (Chatfield) objected that 6in cruisers should be used with the battle fleet, because they could fall back on supporting heavy ships and because their gun was the best anti-destroyer weapon. However, they would have little chance against the 8in cruisers an enemy would most likely use against British trade. He therefore favoured a convoy escort cruiser protected like the new Y Cruiser (Surrey) but with a speed of 21kts rather than 30kts. Chatfield thought the ship would cost £1.6 million, compared to £2.25 million for Surrey or £1.25 million for a 6in cruiser. First Sea Lord was interested enough to ask for details: displacement of about 7,500 tons, with six rather than eight 8in guns (as in York), plus a good anti-aircraft battery, and one or two aircraft. First Sea Lord added in pen that cruiser units might be multiplied by attaching cruising destroyers or light cruisers of destroyer type to an 8in cruiser.
The slow cruiser idea collapsed because, in addition to escorts, there had to be fast cruisers to hunt down enemy raiders. ACNS (Pound) and DCNS (Fisher) asked whether convoy was the best protection against surface raiders, particularly since at best the Royal Navy would ultimately have no more than seventy cruisers, of which forty-five could be assigned to trade protection. With very few escorts, convoys would have to be large, hence tempting, targets. Convoy tactics against raiders were not the same as the anti-submarine campaign of the First World War, DCNS in particular pointing out that the slow cruiser could drive a raider off, but the raider could survive to attack again.
Leander
Formal work on a 6in cruiser began in 1928, although feasibility studies of such a ship had been going on for several years, sometimes in connection with attempts to reshape the treaty limit. The Royal Navy rather suddenly discovered that the policy of using the same cruisers with the fleet and for trade protection was impractical. The main fleets reported that the big Hawkins class was proving less effective for major fleet roles (supporting and repelling destroyer attacks, night attacks and shadowing) than the C’ and D’ classes (the ‘Counties’ had not been in service with the Atlantic and Mediterranean Fleets, hence they did not figure in the reports). The Staff argued that the fleet cruiser should be armed with the most powerful gun which could be mounted on the displacement (elsewhere set at 6,000 tons), and the broadside should not be not fewer than six guns.4 If six were the maximum they should be in single shields, but if four twin 6in mounts could be provided, that would be better. The guns should elevate sufficiently to range 18,000yds.
Above and below: HMS Leander in her initial configuration, 1933. She represented an austere approach to cruiser design, with only a single main battery director (forward). Later ships of the class also had a much-simplified fire-control computer based on destroyer rather than battleship practice. Essential equipment was slow to materialise. Leander was completed without her HA director or her quadruple 0.5in machine guns, which were still missing in 1933. The aircraft is a Hawker Osprey.
In December 1928 First Sea Lord asked for five sketch designs, differing mainly in armament: (1) five or six 6in guns in single mounts; (2) five or six 5.5in guns in single mounts, and endurance of 6,000nm at 15kts, with catapult; (3) four twin 6in, 6,000nm at 15kts, with catapult; (4) three twin 6in, 6,000nm at 15kts, with catapult; and (5) two twin and two single 6in, 6,000nm at 15kts, with catapult. The Staff later studied and rejected 5.5in rather than 6in guns for the ship. Open mounts were attractive because they were lighter, were easier to maintain, offered small individual targets and made firepower less vulnerable by being spread out. They could not sustain the rate of fire of power-operated mounts, but it seemed unlikely that sustained fire would be needed. As DNO had argued in 1920, centreline space limited the number of such mounts, and it seemed that the new twin mount could fire as fast as two open single mounts. If four twins could be mounted on the same hull as six or fewer singles, they were more attractive. Even without a catapult, a ship could not mount more than seven single centreline guns, if that. With twins, she could have eight, plus the increasingly important catapult. Controller recalled that wartime experience much favoured weatherproof mountings. Single open mounts were, moreover, impracticable if anything beyond 30° elevation was wanted. DNO used the short-trunk arrangement he had first described in 1920. The only problem was protection of the ammunition lobby. DNO was content with the 1in already provided around the hoists, but this seemed so inadequate to DNC’s representative that he wanted DNO’s statement put on record. DNO’s solution was to pass cordite up the hoists in metal cans, which were removed only at the gun.
The cruiser also needed a powerful anti-aircraft armament, because she might be used both to screen aircraft carriers and probably to operate ahead of the main fleet, and hence be in a position to attack enemy aircraft approaching the fleet. The Staff therefore suggested four 4in HA guns and two quadruple 0.5in machine guns (but no pompoms).5 Although torpedoes were not the cruiser’s primary armament, she might well find herself in position to attack when supporting destroyers, so the Staff therefore suggested one quintuple or quadruple destroyer-type torpedo tube on each side.6 The Staff also pointed out that both the Japanese 5,500-ton cruisers and the American Omahas, broadly equivalent to what was being planned, carried aircraft, and the British must do the same to remain equivalent.
The Staff Requirement demanded that shell rooms and magazines be immune from 6in shell (at 10,000 to 16,000yds, setting side and crown thicknesses, respectively, at 3in and 2in). They also had to be immune to destroyer fire (4.7in shell) beyond 7,000yds.7 The minimum acceptable displacement (to hold down unit cost) was 6,000 tons. That choice was based on the relationship between displacement and sustained speed in a seaway: ‘Visualise a seaway of 4 to 5, steady monsoon conditions, and a fleet proceeding at 17kts.’ Cruisers needed enough additional speed to change position within that fleet. Experience with the Arethusa, Birmingham and Durban classes suggested that 6,000 tons was a minimum to provide adequate high-speed seaworthiness in average weather. Analysis suggested a minimum speed of 30.5kts (at deep load). The ship might gain from higher speed (to escape large enemy cruisers), but she would be working with larger cruisers, which would support her. Plans Division wanted an endurance of 7,000nm at 16kts because the fleet was to be capable of carrying out a complete operation in the Far East without refuelling (it was considered difficult to fuel cruisers at sea).8
As completed (1930), Leander shows one of two tactical rangefinders (one each side) atop her bridge and two of her four 4in HA guns, but not (as yet) their director.
Neptune as in 1941. Note quad 0.5in on ‘B’ turret roof. (John R Dominy)
Orion in 1943, after completion of outstanding ‘As and As’ in the UK after her US refit. (John R Dominy)
DNC found that he had to provide four-shaft machinery (rather than lighter-weight three shafts) to provide centreline space aft for magazines and shell rooms under the turrets. The usual oil stowage spaces (below the machinery and below the lower deck forward and aft) would accommodate about 1,600 tons; any more oil would be stowed in some lower deck spaces aft normally occupied by provisions and storerooms, and the ship would therefore become somewhat congested. DNC expected endurance at 16kts to be 6,000nm with 1,600 tons of oil and 7,000nm with 2,000 tons, based on the recent steaming trials of HMS Berwick. These were unusually large amounts for so small a ship. The new cruiser had Asdic. Communications capabilities should approximate those of the large cruisers.
DNC submitted the five desired sketch designs, with their different armaments, on 23 January 1929. He estimated that 60,000shp machinery would provide 31.25kts at 6,000 tons and 29.75kts at deep displacement if the ship carried 2,000 tons of oil (30kts if she carried 1,600 tons). The ship’s length was set by her desired speed, and DNC pointed out that the relatively long hull required stronger plating (1in) amidships over the machinery. This plating would also provide some protection, but unlike other protection it could not be traded off against other weights in the ship. Overall, the new cruiser had the same type of box plus belt and deck protection as the earlier 8in cruisers. In addition to the 1in of structural plating, she had 2in of armour over her machinery (total 3in, but because it was in two thicknesses, it was not as effective as the single 3in thickness over the magazine sides). From directly abeam (the worst case) the side was proof against 6in shell beyond 16,500yds and against 4.7in beyond 9,000yds; the deck would protect inside 13,000yds (against 6in) and would keep out destroyer shell at all ranges. In the twin mount designs turrets were close together, adjacent mounts sharing one ammunition lobby. A single hit below the turrets could knock out their entirely unprotected hoists and put two turrets out of action at once. The battleship design then being considered reduced this threat by covering the hoists with 1in protection, and the cruisers were given similar protection, despite its 100-ton price.
Designs 1 and 2 (five or six single guns) met the 6,000-ton requirement; Design 3 (four twins) would displace 6,400 tons standard, and Designs 4 and 5 (three twins or two singles and two twins), 6,200 tons. The extra displacement in Design 3 would cost 9in in draft and slightly more than 0.5kt in speed. The heavier ships could be brought down to 6,000 tons by cutting protection, but except for Design 5 there was not enough weight left for adequate magazine protection (without machinery protection beyond the 1in hull sides). In Design 3, for example, only 245 tons were available for protection, but 375 tons were needed for the magazines and other items beyond machinery protection. In this case magazine protection would have to be cut to 2in side and 1¼in crown.
Above and below: As an early beneficiary of the anti-aircraft rearmament programme, in 1937 Leander showed four twin 4in guns and the planned quadruple 0.5in guns abaft the searchlight platform aft. The aircraft is a Supermarine Walrus, newly introduced into British service.
The alternatives were discussed at a conference on 30 January 1929 chaired by First Sea Lord. The sketch designs convinced Controller that 6,000 tons was too small; better to add another 400 or 500 tons. E-in-C was already complaining that the proposed machinery arrangement crammed the power of the recently-designed Surrey into a much smaller space, but DNC answered that he needed the full 60,000shp, and that some cramping was inescapable in the smaller hull. Given the difficulty of stowing the full 2,000 tons of fuel, the conference decided to have DNC consider stowing 200 tons rather than 400 tons in addition to the 1,600 tons he could easily stow, and therefore an endurance of 6,500nm at 16kts on 1,800 tons of fuel was tentatively adopted. The conference was unhappy with DNC’s 30kts deeply loaded, but could not see any way to get more. To ACNS, rapid acceleration was more important than high speed for ships working with destroyers.
Above and below: Orion is shown at a southern US port in 1937. Note the windbreak, probably for the new air defence (control) position, and the new searchlight platform above the lower level of the bridge. At this time the ship had only two of her four twin 4in guns aboard. Of the five ships, only Achilles, assigned to the Royal New Zealand Navy, did not have twin 4in guns when war broke out.
Orion is shown escorting Convoy OA-196 in the North Atlantic, 10 August 1940. War modifications to date have been minimal: air-warning radar (vertical topmasts on both masts) atop new tripod masts and splinter shields for the bases of the twin 4in guns. Ships were soon fitted with Oerlikons, including single guns atop ‘B’ and ‘X’ turrets. Other standard positions were the signal deck (at shelter deck level alongside the bridge, in place of quadruple 0.5in machine guns), two abeam the mainmast, and one or two on the stern.
The Conference chose Design 3, with its four twin mounts. In May 1929 DNC submitted a sketch design for a 6,500-tonner (510ft between perpendiculars, 535ft on the waterline x 55ft); the Board approved it on 3 June 1929. Perhaps surprisingly, given the interest in anti-aircraft fire, it showed only a single HADT, aft on the centreline, with an LA DCT atop the bridge structure and an auxiliary LA director tower abaft the HADT. The bridge was the new angle-sided structure planned for Exeter and Surrey. As in those ships, masts and funnel were vertical. However, in this design the uptakes were all trunked into one massive streamlined structure intended particularly to limit objectionable smoke eddies abaft it. Gun armament was eight 6in Mk XXIII guns (200 rounds each) in Mk XXI turrets, four 4in HA Mk V or XIV (150 rounds each), and four quadruple 0.5in machine guns (2,500 rounds each). Tests of the new 6in gun showed that more armour was wanted to achieve the desired level of protection. As the design was developed, the magazines were enlarged (and hence also their protection), among other things to provide a separate handing room for each turret, instead of one for each pair of turrets, fore and aft. In 1932 the armament of these and later 6in cruisers was modified, the two quadruple 0.5in guns on the upper bridge being eliminated but one more added, for a total of three. Ships were also assigned a five-charge depth-charge rail (total stowage seven depth charges).9
DNC continued to consider alternatives. In July he assigned Lillicrap, who was estimating the effect of triple turrets on a heavy cruiser, to sketch a 6in cruiser with such weapons. The 6in mount had a much smaller below-decks footprint, hence did not interfere with shaft lines even in a smaller hull. As in the heavy cruiser, three triples would probably weigh about as much as four twin mounts, protection weights roughly balancing; additional ammunition (for one more gun) would weigh 15 tons. The ’tween decks working spaces would take up valuable mess deck space, to the point that Lillicrap doubted satisfactory arrangements could be made, and 50 tons of oil stowage would be lost. For this study he used the 80,000shp powerplant of the heavy cruiser London, giving 33.25kts at standard displacement and 31.75kts deep. With the same protection over machinery as in the larger cruiser, the ship would displace about 6,890 tons. If the ship had to be cut back to 6,500 tons, to retain magazine protection would require that all machinery protection be given up. To combine extra power and protection over the machinery he had to adopt destroyer-leader machinery, in which case displacement would be 6,640 tons. The overweight of 140 tons could be eliminated by cutting the belt and deck over the machinery by ½in. Lillicrap ended estimating that 100 tons of oil stowage would be lost, for a total of 1,700 tons rather than 1,800 tons, and an endurance of 6,100nm rather than 6,500nm at 16kts.
This study confirmed DNC’s view that on 6,500 tons he could not go beyond four twin turrets and 60,000shp. On 26 July he or Lillicrap decided that the ship needed better subdivision. Instead of two boiler rooms (one with two and one with four boilers, 28ft and 44ft long) the ship should have three 28ft rooms, adding 12ft to machinery length (later E-in-C made the increase 19ft over the original 160ft). Some of the extra length could be gained by rearranging spaces at the ends of the ship, but the ship had to be lengthened by 13ft. Given added displacement, the beam had to be increased to maintain stability, and greater depth was needed to maintain hull strength. To maintain speed, another 3,000shp was needed (which seemed to present no great problems). As in the heavy cruisers, the machinery offered a kind of unit operation (originally the four boilers in the after boiler room and the two sets of turbines in the forward engine room formed a central unit).
A sketch dated 25 August 1929 showed dimensions of 547ft (waterline) x 54ft, and a displacement of 7,000 tons. Magazine protection was increased by another half-inch on the sides and ends. The main engine-space bulkheads were substantially thickened. Shell rooms and transmitting station were given 1in crowns and sides. The design was criticised: the side armour did not extend far enough below the waterline. In standard condition the lower edge was 2ft 6in below the waterline (5ft 9in below at full load). CNS wanted it simply lowered, arguing that the upper 3ft of armour was not very useful. Controller wanted the depth increased to 3ft in standard condition, so that in average condition it would be 4½–5ft below water. The extra armour added about 10 tons, which was acceptable. For the first time in a postwar British cruiser, the boiler room and engine room fans were protected. Without them, a cruiser probably could not exceed 10kts.
This design was submitted in October 1929, receiving the Board Stamp on 20 November 1929. DNC pointed out that although the new power-worked turrets needed many more men per gun than simple open single 6in mounts, the hull offered no more volume than that of HMS Emerald. More space was taken up by larger wireless offices, workshops and storerooms. Thus the standard of accommodation could not match that of the large cruisers, even though the ships were expected to operate in the tropics. The detailed design went to the Board in December 1929. Estimated speed was 31.5kts, and tank tests were being conducted to see whether a small bow bulb would help (they showed it would add about an eighth of a knot at 25–32kts, and would have no effect at all at cruising speed). DNC estimated that the 1,800 tons of oil fuel would give an endurance of 7,000nm at 16kts and 8,000nm at 12kts, an improvement over previous estimates. This design received the Board Stamp on 9 January 1930.
Meanwhile the Board laid out a 1929/30 programme. On 29 November 1928 it decided that if the US building programme (for fourteen cruisers) was approved, the Admiralty should recommend laying down three 10,000-ton cruisers (Surrey class) in 1929. However, by March 1929 it was clear that although the US programme had been authorised, it was possible that a new naval arms conference might be held before the last five US heavy cruisers were begun. The British already hoped to limit 8in gun cruisers to a total of 200,000 tons. On 7 March 1929 the Board therefore proposed that the programme consist of one Surrey (called the Y Cruiser, of 10,000 tons) and two of the new 6,500-ton 6in cruisers (O Type). This programme would maintain the 5:3 ratio of heavy cruisers against Japan (assuming that the four Hawkins class were equivalent to two Furutakas), maintain parity with the United States in 8in cruisers up to 1933, and begin replacement of the old 6in gun cruisers. It would also leave Britain free to resume building 8in cruisers if necessary. In fact the 1929/30 programme was cut to a single 6in cruiser, HMS Leander, as the 1930 London Naval Treaty finally stopped construction of 8in cruisers. Four sisters and three half-sisters (Amphion class) were later built.
Orion is shown on 6 March 1942, after a major post-damage refit at Mare Island Navy Yard (5 September 1941 – 15 February 1942). She had been damaged on 29 May 1941, then received temporary repairs at Simonstown (14 July 1941 – 5 August 1941). There her catapult was removed. Mare Island removed her quadruple 0.5in machine guns and installed two quadruple pompoms (one visible aft, abeam the boat on the centreline) and seven single Oerlikons (including one each atop ‘B’ and ‘X’ turrets and three in zarebas on the after superstructure). The yard also installed new radars (Types 284 and 285 on her directors, and Type 279 on her masts [the mainmast aerial is not easily seen in this photograph, but others show it]; note that there was no antenna on the mainmast). The US yard lacked some of the desired material, so the ship went to Devonport (30 March – 24 April 1942) to complete outstanding approved alterations and to be fitted with a Type 273 surface-search radar. Orion was unique in having this radar aft, forward of the mainmast. In the other ships it replaced the HA director on the centreline; instead ships had two HA directors, one each side of the bridge. The only unit of the class which did not receive extensive improvement was HMS Neptune, sunk on 19 December 1941. She had only a single refit, at Chatham, 12 February – 1 May 1941, during which she received her allotted three quadruple 0.5in machine guns, three single pompoms, and radar (Types 281, 284 and 285).
Ajax is shown after a refit at Chatham (27 May – 24 October 1942) during which she was fitted with two quadruple pompoms (in zarebas abeam her after superstructure). A single Type 272 surface-search radar replaced the centreline HA director, and to replace it two such directors were installed lower down on each side abeam the bridge. The Type 279 air-warning radar was fitted during an earlier Chatham refit (December 1939 – July 1940) to make good damage after the battle of the River Plate. At that time she received a larger catapult. It was, in effect, replaced by the pair of quadruple pompoms. Early in 1942 she had six single Oerlikons, and during the 1942 Chatham refit another three were added, the quadruple 0.5in machine guns being landed.
During detailed design the new cruiser’s power was boosted to 72,000shp to achieve 32.5kts. The two outer shafts carried 48,000shp, the two inner ones 24,000shp. The change in machinery arrangement had already cost 24 tons, but the cost of this further change was limited to 50 tons by increasing boiler pressure from 250 to 300psi, by increasing revolutions at maximum power from 280 to 300 per minute, and by using higher-quality materials. To extend range, in addition to the usual measures used to increase economy at cruising speed, the two forward sets of turbines could be disconnected from their shafts, the inner shafts alone providing enough power for up to 21kts. That was expected to reduce fuel consumption by 10 per cent at 15kts (20 per cent at 10kts). Also, skilled mechanics and ratings could be released from watchkeeping duties and assigned instead to maintenance. These changes were apparently first proposed for the 1931 ships (Board Stamp 6 November 1930) and then retroactively applied to Leander (second Board Stamp, 4 June 1931).10
Ajax is shown during a refit at New York Navy Yard (4 March – about 15 October 1943). The new object visible forward of the bridge was a barrage director with Type 283 radar. It was also installed on board Achilles and Leander. The two quadruple pompoms fitted at Chatham were replaced in New York by two quadruple Bofors guns, and four single Oerlikons were replaced by US-type twins (hand-worked). This refit counted, in the official list of British warships, as modernisation (no other Leander counted as modernised).
Above and below: Photographs of HMNZS Leander taken from the destroyer Nicholas show the ship with a surface-search ‘lantern’ aft in addition to the New Zealand fire-control and air-warning radars. By this time she had an Oerlikon atop ‘X’ turret as well as ‘B’ turret, but she had not yet had a major refit to provide her with multiple pompoms. Probably four single Oerlikons in all were added at this time (the date of the refit is uncertain). Her catapult was removed during this refit. These photographs were officially dated 25 July 1943, but they were clearly taken earlier, since Leander was damaged by a Japanese torpedo on 13 July.
The revised Leander design approved in June 1931 was rated at 7,154 tons rather than 7,000 tons standard; the 1931 design approved in November 1930 was rated at 7,140 tons, and in revised form (on 4 June 1931) at 7,184 tons.11 The 1930 London Naval Treaty made weight-saving absolutely vital. Unfortunately the new twin 6in mounting was grossly overweight, much as the twin 8in had been.12 Leander came out heavy, but DNC managed to cut weights on other ships. As inclined shortly before commissioning, Ajax (the last Leander) displaced only 6,837 tons standard. She was the lightest of the lot. Standard displacement deduced from weights was Leander 7,178 tons (7,140 tons reported); Achilles 7,018 tons (7,030 tons reported); Neptune 7,110 tons (7,030 tons reported) and Orion 7,128 tons (7,070 tons reported). For treaty purposes the ships were described as 7,000-tonners.13
In the three 1930 Leanders, the separate bomb room (forward in the hold between the 4in magazine and ‘B’ shell room) was eliminated. Bombs were stowed instead in the torpedo warhead magazine. That cleared space below the platform deck for a protected HA calculating position. This new space was placed between the transmitting station (6in calculating space) and the 4in HA magazine, the latter being moved forward. Reducing the plating over the new HA calculating position to the protection already provided to the transmitting station would save about 8 tons. Space formerly occupied by the HA calculating position would be used for a relocated auxiliary W/T office. This change was so attractive that it was applied retroactively to the two large 1931 cruisers. More weight was saved by adopting a light catapult and limiting the cruiser to lightweight (fighter-reconnaissance) aircraft. Given the limited total cruiser tonnage, every ton counted. This change was applied to the two large 1931 cruisers. All of these ships also had their forecastles extended, adding some more accommodation space.
Leander is shown on 16 October 1942, having been refitted in New Zealand, with New Zealand radars, late in 1941. This outfit comprised a fire-control set, its antenna atop the director, and an air-warning set whose antenna was mounted atop the lattice tower forward of the funnel. Five single Oerlikons were mounted (one atop ‘B’ turret – but, unusually, none atop ‘X’), two on the forecastle abeam the bridge, and two right aft. These Oerlikons do not appear in a February 1942 photograph taken at Suva, Fiji, from USS Curtiss, but the two radars were already clearly in place. The centreline quadruple 0.5in machine gun was clearly present in the earlier photograph. She still retained her catapult at this time. Leander and the other New Zealand cruiser Achilles seem to have been unique at this time in retaining their pole masts.
After her torpedo damage Leander went to Auckland for temporary repairs (in hand August 1943, completed December 1943), then to Boston for permanent repairs (3 January 1944 – 27 August 1945), and then to Rosyth to add additional work. She is shown at Boston on 24 August 1945. Note her new radars (single-antenna Type 281B, clearing foremast space for Type 293, and Type 277 on a stub mast replacing the earlier Type 273). ‘X’ turret was landed. At the end of the Boston refit she had two quadruple Bofors guns and three twin and four single Oerlikons. The additional refit at Rosyth replaced the quadruple Bofors with twin Mk V, and eliminated all single and one twin Oerlikons in favour of three single Bofors Mk III. Achilles also served with the RNZN. She was refitted at Portsmouth between 1 April 1943 and 20 May 1944. ‘X’ turret was landed (as in Leander), and the single 4in finally replaced by twin mounts. Her catapult was landed. She was fitted with four quadruple pompoms (two replacing ‘X’ turret), seven twin power Oerlikons, and four single Oerlikons. In October 1945 Achilles was credited with an additional five single Bofors (reduced to four by April 1946). One of the Bofors was apparently atop ‘X’ turret.
Leander was generally well-liked at sea; her captain described her as ‘an excellent ship with the handiness of a destroyer, but possessing a battleship bridge, Kent class stowage, and “C” class accommodation’. However, in his interim report (of December 1932) her Captain attacked her bridge for its poor look-out facilities. Earlier cruisers had wide bridges but limited depth, so personnel lined up along their fronts could easily look forward. The new type of bridge was narrow but deep. The captain and officer of the watch could see ahead over the narrow flat of the bridge, but the view for all others – admiral, signal officer, signalmen, lookouts – was poor. Looking forward through angled glass gave a distorted view. The windows had to be lowered if there was rain or spray, which would break so fiercely against them as to block the view – but which would also blow into the faces of anyone looking out without a window. This problem was experienced when the ship left harbour at night in rain. Also, the chart tables on the angled sides of the bridge cut out much of the available frontage where personnel could stand (matters would have been worse had one of the chart tables been replaced by a plotting table, as had been proposed). Finally, there was no sheltered position for lookouts. These were serious matters, as the same bridge design was being used in many other cruisers. For some reason the comments were not repeated in the formal report on the ship, so DNC did not have to answer them.
Cruiser Alternatives
With the Leander class design well underway, in July 1929 Controller proposed a study of a smaller ship. If the United States demanded parity at the next conference, the only way for the Royal Navy to get the numbers it wanted might be to reduce ship size. Numerous ‘C’ class ships of about 3,000 tons were approaching the end of their lives, and on a tonnage basis the Royal Navy would get only about one-and-one-quarter of the new ships for every two ‘C’ class cruisers it discarded. Cruiser size kept veering up and down; the ‘Cs’ were almost certainly too small, but the 4,800-ton ‘Ds’ were good ships, so a 4,500-ton design might be useful. First Sea Lord (Madden) asked ACNS to look into Controller’s suggestion on the basis of two three-gun turrets, no vertical side armour and, say, 30kts. This idea in turn led to analysis by Tactical Division of the requirements which had led to the 6,000-tonner (which became the 6,500-tonner and then the Leander) in the first place. It took 6,000 tons to insure a sea speed of 26–27kts; a 4,500-tonner might be limited to 24kts, giving a margin of 7kts over the battle fleet at cruising speed. Any reduction in endurance would risk denuding the fleet of cruisers at a critical time, and hence was not acceptable. For deep speed, 30.5kts seemed to be a bare minimum. Tactical Division disliked mounting the whole 6in armament in two triple turrets; it preferred single mounts (it thought the ship might be too lively for a power-operated twin mount). Probably the ship would mount five such guns. The bare minimum HA battery was three guns and the bare minimum of protection was magazine cover against destroyer 4.7in guns.
Given these studies, at the end of September 1929 the Sea Lords asked for a range of alternatives, to be used as a basis for a British position at the naval conference due in January 1930. The most suitable might be something like the French super-destroyers of about 3,000 tons, which were then credited (incorrectly) with six (rather than five) 5.5in guns and a speed of 35kts. Japan had a similar ship in the 3,100-ton Yubari. Another possibility was something like the Italian Bande Nere (5,000 tons, eight 6in, 37kts, using destroyer machinery), while yet another was a ship with machinery and scantlings of destroyer-leader type, the speed of a British heavy cruiser, a 6in battery and magazine protection only. The fast ship would be a link between heavy cruiser and destroyer, which the slower Leander was not.
DNC assigned Lillicrap to develop the alternatives, beginning with a 4,000-tonner (5,500 tons deep), in effect a large, lightly-protected destroyer. She would be armed with five or six 6in guns.14 Lillicrap soon settled on three twin 6in guns, two 4in HA, two single pompoms, and two triple torpedo tubes, but he found that even with destroyer machinery, 4,000 tons left nothing at all for protection. DNC had wanted at least a little protection for the magazines, a 1in crown, but by November he wanted a lot more: 2in box protection (sides, roof, ends) and 1in over the shell rooms and transmitting station and a 1in turtle-back over the steering gear. With bullet-proof bridge plating, that added up to 125 tons, hardly an insignificant amount in a small ship. Lillicrap estimated that he could work in about 750 tons of oil, enough for 5,000nm at 12kts. Instead of twin mounts, the final version of the ship had five single 6in guns, but it was also protected as desired. On the displacement, which by now was 4,200 tons, there was no possibility of protecting the machinery.15
The next study was a ship with three twin 6in and lower speed (32kts, but 33kts was desired). Lillicrap scaled her hull up from the 4,000-tonner and her armament down from the 7,000-tonner (Leander) and again destroyer machinery would be used to cut weight. As in the 4,000-tonner, protection was limited to the armament. The result displaced about 5,600 tons. Then Lillicrap produced a 6,000-tonner with four twin 6in, again with unprotected destroyer machinery but with the same magazine and other armament protection as the 5,600-tonner.16
At the other end of the scale, Lillicrap scaled down his 4,000-ton ship to 3,000 tons to produce a super-destroyer (‘fleet scout’), broadly equivalent to contemporary French ships. He armed the ship with six single 5.5in guns (200 rounds each), two 3in HA guns, two pompoms and eight torpedo tubes, and sought a speed of at least 36kts. As in the 4,000-tonner, there was no space for a catapult or aircraft and no protection.17
These studies were reported to DNC on 22 January 1930. A set of small-scale sketches showed Leander-style single funnels and other features in the 6,000-ton and 5,600-ton cruisers. However, the 4,200-tonner had two raked funnels, a set of centreline torpedo tubes and five single gun mounts, one just abaft the second funnel. Leander was described as a 6,800-tonner. Estimated unit costs were: £1.6 million for the 6,800-tonner, £1.4 million for the 6,000-tonner, £1.3 million for the 5,600-tonner, £1 million for the 4,200-tonner and £750,000 for the fleet scout.
Controller (Rear Admiral Roger Backhouse) seems to have found the fleet scout particularly interesting. He was told that adding magazine protection (2in side, 1in crown) would cost about 75 tons and half a knot. He wanted to know whether some of the guns in the 4,200-tonner and 3,000-tonner could be paired. This was impossible in the 3,000-tonner, but on 4,500 tons the 4,200-tonner could have two twin 6in forward and two singles aft, which would make space for a catapult.18 During the First World War Controller had commanded the light cruiser Conquest and he recalled the value of a waterline belt, which kept the waterline intact – ‘we cannot hope to keep out all hits, but it is a great thing to keep out some’. He therefore asked for belt armour on the 4,500-tonner. That added 300 tons, including 80 tons for a 1in deck (only half of it for protection) and 40 tons for 1in end bulkheads.
The battleship-building ‘holiday’, the centrepiece of the Washington Treaty, was due to expire on 31 December 1931. By 1929 governments, at least in London and in Washington, had every reason to want to extend it, so they sought some sort of naval agreement. Mindful of the way that the 1927 conference had collapsed, both governments agreed not to allow naval officers to be delegates, although there were certainly naval advisors. The US Navy had reason not to resist, because a bill authorising fifteen cruisers, introduced in Congress in February 1928, passed in February 1929. This bill met the nominal US requirement for twenty-three 10,000-ton cruisers. Admiral Pratt, the US Navy’s arms-control expert, was now Chief of Naval Operations. The feeling in the US Navy against any sort of treaty was so intense that some officers asked him to resign when he returned from the 1930 conference – despite his attempts to show that the United States had actually gained. For the British, there was increasing awareness that continuing to build large cruisers would be ruinous.19 The financial crisis which began with the Wall Street Crash on 29 October 1929 helped convince both the US and British governments that it was time to make some sort of deal.
Much of the basis for an agreement between Britain and the United States seems to have been in place as early as July 1929. Meeting with American representatives, Prime Minister MacDonald and First Lord A V Alexander accepted the main US points – leaving the 5:5:3 ratio in place; parity should be enforced in overall combatant strength in each of five warship categories (cruisers, destroyers and submarines in addition to capital ships and aircraft carriers, with submarines to be abolished if possible); that the battleship-building ‘holiday’ of the Washington Treaty would be extended to 31 December 1936; and that relative levels of strength would be equalised by the same date. The United States offered to scrap sufficient destroyers and submarines to bring it down to the level of the Royal Navy. MacDonald repeated the British requirement for forty-five trade-protection cruisers, but not for the twenty-five to operate with the fleet. He felt compelled to offer to cut total British cruiser strength to fifty. The Admiralty considered this sacrifice acceptable only if it was temporary.20 MacDonald also suggested freezing 8in cruiser construction at the fifteen already built for the Royal Navy and at eighteen for the United States, which could have another ten 10,000-ton cruisers armed with 6in guns (the Admiralty seems not to have realised this was a real possibility). There was some question as to whether the Hawkins class should be considered heavy cruisers or more akin to light ones of First World War design, and also of how the smaller ‘C’ and ‘D’ class should compare to the US Omahas.21 The US government was less than enthusiastic, because the British proposal amounted to demanding a considerable superiority in cruiser strength, assuming that the US Navy built no further small cruisers (which it regarded as useless for Pacific warfare). The British saw their idea as a kind of parity, in which the US Navy would have superiority in large cruisers compared to a larger British number of smaller ones
In October 1929 MacDonald met US President Herbert Hoover in Virginia to settle as many of these issues as possible. On 7 October invitations were sent to all five major sea powers for a conference to convene in London in January 1930. In order to avoid problems, the organisers tried to exclude naval officers, although they had to accept admirals in the Italian and Japanese delegations. New Zealand sent her Governor-General, Admiral Jellicoe, who pointed out that to cut British cruiser strength to fifty would be to risk the security of the Empire. First Sea Lord similarly reiterated the requirement for seventy, which could be cut only if other powers drastically cut their own cruiser forces. The fifty-cruiser deal had already been made, however. For the Japanese, the main object was to raise their tonnage ratio, as they considered the one enforced at Washington humiliating. The ultimate Japanese objective was parity with the two Western sea powers, which would have made any Pacific naval campaign impossible for them individually.
The London Naval Treaty which emerged from the conference distinguished cruisers by main armament rather than by tonnage: heavy cruisers had guns of up to 8in calibre, and light cruisers guns of up to 6.1in calibre. The Royal Navy would build no more such ships; total Empire strength, including Australia, was fifteen. The US Navy was allowed a total of eighteen, despite its desire for twenty-three. The Japanese had to be satisfied with twelve. Total underage cruiser tonnage was also limited, the British being permitted a total of 192,200 tons of completed 6in cruisers as of 31 December 1936. Total replacement tonnage laid down after April 1930 and completed by 31 December 1936 was not to exceed 91,000 tons. Ships to be retained on 31 December 1936 could total 101,480 tons, which limited new construction to 90,720 tons. In effect the British government accepted an upper limit of fifty cruisers – which it did not have. To meet the fifty-cruiser goal by 1936 required a building programme of fourteen cruisers within the available tonnage, including HMS Leander of the 1929 programme. Since cruisers normally took three years to complete, the fourteen-cruiser programme spanned the four programme years through to 1933. The Admiralty planned three cruisers in each of 1930/1, 1931/2 and 1932/3, hoping that Australia would provide the fourteenth ship in the form of a replacement for HMAS Brisbane. Failing that (which happened) the Royal Navy would buy another ship in one of the years between 1931 and 1933.
Given the block obsolescence of British cruisers built during the First World War, the treaty set a sixteen-year age for ships laid down before 1 January 1920, a twenty-year age after that. As of 31 December 1936 the British Empire would have only eight underage 6in cruisers (as the situation stood in February 1932). By that time thirty-two light (6in) cruisers would be overage, and the four Hawkins class would have to be discarded. The Admiralty planned to retain fourteen of the seventeen ships which would be between sixteen and twenty years old in 1936, after which date a higher rate of construction would be needed. The Admiralty position was therefore that the 1930 treaty should be a short-term agreement, to be reviewed when it expired. The expectation seems to have been that the prospect of a renewed building race after 1936 would deter other sea powers from building too many cruisers during the life of the treaty.
With their large super-destroyers and small light cruisers, neither the French nor the Italians could accept separate limitation of destroyers and cruisers. Although both refused to ratify, they did agree to cease building 8in cruisers (in theory, both retained the right to resume doing so). As an incentive for them not to ignite a naval arms race, the treaty included an escalator clause: a signatory which considered itself endangered could announce that it was enlarging its fleet. That gained importance as the international situation darkened in the mid-1930s.
The Intermediate Cruiser: the Arethusa class
The fourteen new cruisers could be any combination of the designs on hand. Controller (Backhouse) considered the 3,000-tonner to be too spe-cialised,22 so he decided to mix the maximum number of 7,000-tonners with a new 5,000-ton design intermediate between a Leander and a fleet scout, which DNC could develop by scaling up from the 4,200-tonner previously offered. Once the 5,000-ton intermediate design was well in hand, in December 1930, Controller laid out a programme of ten Leanders and four intermediates. Three repeat Leanders were included in the 1930/1 programme, during which the 5,000-tonner would be designed.
Arethusa as fitted, March 1941, with two quadruple pompoms added. Note the UP projector on the quarterdeck. She soon had a second atop ‘B’ turret (both UP projectors were apparently landed during a refit in 1942). The space above the torpedo tubes was later decked over. Arethusa was fitted with a Type 286 radar during a refit in July 1941, and had that set until Type 281 was fitted during a Chatham refit (6 February – 9 April 1942). At that time she received four twin 4in guns. (A D Baker III)
C-in-C Mediterranean particularly liked the intermediate as a fleet cruiser.23 However, given sharply curtailed numbers, such specialisation was impossible; the 5,000-tonner seemed to be the smallest cruiser which could fulfill both fleet and trade-protection roles.24 Controller saw the 4,200-tonner as a cross between an updated version of the well-liked ‘D’ class cruiser and the new French 2,600-ton super-destroyers armed with 5.5in guns. Later First Sea Lord described the new cruiser as an updated ‘D’. Apparently it was easier to work up from the 4,200-tonner than down from the 5,600-tonner, the idea being to stay below 5.000 tons. Before that design was further developed, in June 1930 Rear Admiral Henderson, who headed the British Naval Commission to Romania, asked for a cruiser design. Lillicrap showed that if armour over the machinery was eliminated, a 5,700-ton ship could carry roughly a Leander armament.25 That must have encouraged DNC to think that a viable six-gun ship could be designed on less than 5,000 tons. Work on a 4,200-ton design upgraded to three twin 6in guns began early in August 1930. It had the armament of the 5,600-tonner, except that there were two rather than four 4in guns (Controller wanted three), and, it was hoped, two triple rather than one quadruple torpedo tube. On the other hand, it had a seaplane and catapult.26
Controller asked for an endurance of 5,500nm at 16kts, for a good sea boat with a raised bow (but with height between decks minimised, to minimise the target). Magazines should be protected against 6in fire, with whatever machinery protection could be provided on the available displacement. This meant magazines with 3in sides, 2in crowns, and 2in ends where they met the machinery box, and by this time it was standard practice to provide an inch over the shell rooms and the transmitting station. A 1in splinter deck over the machinery was desirable, and structural strength demanded half-inch side and deck plating over the machinery. The desired endurance speed was higher than in the earlier design, which required extra length (10ft) for the same distance at 15kts rather than 12kts. Now the 940 tons of the earlier ship would have to increase to 1,140 tons (another 10ft longer than the original design).
It seemed impossible to hold down the size of the ship. The oil fuel requirement stretched her length to 500ft, which suggested a displacement of 5,200 tons, and size would spiral further because of the additional armament (compared to the 4,200-tonner) and protection. A 5,000-ton ship could be driven at 33kts on 60,000shp. Lillicrap provided machinery protection (3in side, 1½in deck). DNC understood that displacement had to be held down, so he suggested cutting power to 48,000shp in the hope that machinery weight could be dramatically reduced. A shorter machinery box required less protection. Lillicrap was to estimate what armament and protection could be had on the remaining tonnage. Not enough was left, but on about 4,500 tons Lillicrap could offer two twin and two single 6in guns on a 480-foot hull with nearly the same level of protection (machinery would be protected by 2in sides, a 1in deck, and 1½in end bulkheads).
Controller still wanted three twin mounts, and by mid-September a sketch design had been completed.27 DNC became interested in alternating engine and boiler rooms to make the ship more survivable. Initially it appeared that the ship would need six boilers like those of the earlier heavy cruisers, and E-in-C suggested placing the forward engine room abaft the forward boiler room, with two more boiler rooms forward of the after engine room. Alternatively, four larger boilers could occupy two boiler rooms. They were taller than earlier ones, so the armoured deck over the machinery had to step up to cover them. The belt alongside had to extend higher to meet it. DNC put these ideas aside to develop a conventional 4,800-ton design with three boiler rooms forward of two engine rooms, as in a Leander, giving an endurance of 5,000nm at 15kts. Lillicrap provided DNC with rough particulars in mid-September 1930. He offered full magazine protection, but 2in over the machinery sides. On 60,000shp the ship would probably make 32kts. Only destroyer machinery would give more speed; E-in-C rejected it. Lillicrap calculated what would be needed to achieve 33 or 34kts.28
Aurora as completed in 1938, as yet without her HA director forward. Note the deckhouse which replaced her catapult, as she was completed as RA(D) flagship.
Lillicrap’s alternatives were presented at a Sea Lords meeting on 23 October. The Staff wanted 33kts in standard condition, corresponding to a seagoing speed of 32kts, which Lillicrap’s estimates suggested required 68,000shp in a 490ft hull. E-in-C wanted 8ft more of machinery box, which would also boost protection weight. The conference agreed that E-in-C could decide whether he could provide enough power to drive a 5,000-ton ship at 33kts. Displacement should not exceed 4,950 tons, Legend speed being 33kts and endurance 5.500nm at 15kts, with cruiser-type machinery with three boiler rooms. Controller felt strongly that effective subdivision of engine and boiler rooms had been neglected and should now be emphasised, as other navies were increasing the subdivision of their ships. DNC argued that extra subdivision made a ship much more complicated; with three boiler rooms instead of two, she had to be 8ft longer, with heavier machinery. The conference agreed that eliminating the mainmast was a virtual increase in the ship’s protection, because it made the ship’s course much more difficult to estimate. DNC’s choice of triple tubes was accepted.
Machinery weight kept growing (it was 42lbs/shp rather than 40lbs/shp); Lillicrap doubted that everything the Sea Lords wanted could be provided within a 5,000-ton limit. Reductions in protection and armament would probably not be acceptable, so speed had to be cut. He suggested a 480ft ship developing 60,000shp to make 32kts, which could probably make the desired 5,500nm at 15kts. DNC accepted this idea, and Controller agreed. On 30 October DNC formally instructed Lillicrap to continue on this basis, with displacement absolutely not to exceed 5,000 tons. Initial feasibility studies were over; lines would be prepared and detailed calculations begun.29 Protection was increased to roughly Leander levels: 3in side and 2in magazine crown, 3in side over machinery with a 1in deck. DNC produced a sketch design of the 480-footer in mid-January 1931, somewhat beamier than had been planned (49ft), displacing 5,000 tons. It had the three boiler rooms and single trunked funnel of a Leander. Two separate engine rooms were abaft the boilers. This cruiser had DCTs fore and aft and an HADT on a stalk abaft the forward DCT, atop the new-style bridge. E-in-C provided 64,000shp, despite the machinery arrangement having been a considerable problem. E-in-C and DNC had agreed on a four-shaft powerplant, as it had proven impossible to produce an adequate two-shaft arrangement. DNC expected a speed of 32.5kts (possibly slightly more) at standard displacement (31kts deeply loaded). There were three rather than the earlier two 4in anti-aircraft guns, one of them on the centreline.
Aurora shows some early-war modifications in a November 1940 photograph. She has no radars on board (the device at the foretop is a DF coil), but she has her quadruple pompoms and a UP projector on her quarterdeck (but no UP projector on a turret top). She had been refitted at Portsmouth, 30 May – 28 June 1940 after action damage. She was fitted with radars during a refit on the Tyne, 15 April – 7 May 1941 (Types 290 and 284).
Controller asked for some detail improvements, such as raising the after 4in HA gun on a platform so that it would interfere less with the two other guns on forward arcs. He wanted to reduce belt armour to 2¾in so as to protect 6in turrets, redoubts (rings above deck), and lobbies with uniform 1in, or at least ⅞in, plating. The bulkhead between the engine rooms should be strengthened to 1in because the spaces involved were so large (there were 1in bulkheads at the fore end of the boiler rooms, at the aft end of the boiler rooms, and at the after end of the engine room). The reduction in belt armour sufficed to strengthen protection over the armament to ¾in. DNC was able to thicken the bulkhead between the engine rooms to ¾in (‘a very stout bulkhead’) by reducing the end bulkheads from 1½ to 1in. The after HA gun was raised on a 3ft platform. This revised design was submitted to DNC on 27 January.
The catapult was immediately abaft the funnel, its stowed length being quite limited. It was unlikely that a second aircraft could be stowed. To remain within the 5,000-ton limit, DNC proposed providing space for 200 rounds per 6in gun, but to include only 150 per gun in the weights. Standard displacement would be 4,980 tons.
ACNS pointed out that for trade protection the ship should have a heavy catapult sufficient to launch a spotter/reconnaissance aircraft. Controller suggested that replacing the centreline gun with one on each side (roughly abreast the aircraft crane) would free more centreline space – but it would add 40 tons, and the ship was already at the stipulated 5,000-ton limit. Controller then ruled that the standard displacement need include only enough ammunition for the three 4in guns previously planned (100 rather than 150 rounds per 4in gun). After further consultation with E-in-C, a six-boiler powerplant using three equal boiler rooms was adopted. The revised sketch design received the Board Stamp on 31 March 1931. Standard displacement was given as 5,000 tons.
Penelope shows her full early-war radar outfit in this undated photograph taken in Malta. She was refitted on the Tyne (26 August 1940 – 2 July 1941) to make permanent repairs after grounding in Norway, 11 April 1940. She received her quadruple pompoms and Type 281, 284 and 285 radars, antennas for all of which are visible here. The ship’s catapult was removed. Note the quadruple 0.5in machine gun visible just below the searchlight abeam the forefunnel, and the Oerlikons atop ‘X’ turret and on the quarterdeck. Penelope was mined off Tripoli on 19 December 1941, and then repaired in Malta, emerging with a total of four single Oerlikons were fitted (two of them replaced the quadruple machine guns).
Above and below: Arethusa is shown after a major refit at Chatham (6 February – 9 April 1942); she shows the standard appearance of this class after Type 272 surface-search radars were installed forward of the bridge. Arethusa was refitted at Chatham (17 August 1940 – 30 September 1940) and by August 1941 she had had her catapult removed so that two quadruple pompoms could be fitted abeam its former position, and she had Type 286 radar. By July 1941 she had UP projectors atop ‘B’ and ‘X’ turrets, and four Oerlikons. The UP projectors were removed at Chatham, and it was only then that she was fitted with twin rather than single 4in guns. She emerged from the refit with four more single Oerlikons (eight are visible here, including ones atop ‘X’ turret and on the quarterdeck), and three more were added by October 1942. She was torpedoed on 18 November 1942 while escorting a Malta convoy, and was refitted in the United States (Charleston Navy Yard, 30 March – 15 December 1943). Her quadruple pompoms were replaced by US-type quadruple Bofors guns, and she exchanged four twin US-type Oerlikons for three singles.
The design was badly cramped, with fuel stowage squeezing magazine stowage in the hold, below the waterline. The transmitting station was protected there, but not the low power room necessary to transmit fire-control data, and the 4in handing room was on the platform deck. DNO was anxious to get both spaces under protection and to do that he suggested placing aircraft bombs in the 6in shell rooms, and 0.5in ammunition and the torpedo warhead stowage outside protection. Although the sketches showed DCTs fore and aft, it was soon decided not to provide the 5,000-ton cruiser with facilities for divided fire control (as were being provided in the 1930 Leanders). Fire-control semaphores were also omitted; these ships would not be master ships for concentration firing.
Controller submitted a detailed design on 30 September 1931. Given the financial crisis, tenders could not be invited for some months. Controller therefore asked DNC and E-in-C to reconsider the machinery arrangement, with its two large engine rooms adjacent to each other. Rearrangement seemed important given recent experience in shellfire trials against the battleship Empress of India. DNC proposed placing one of the three boiler rooms between the two engine rooms. He wanted the two engine rooms at least 40ft apart, so that explosion damage to the compartment between them would not disable them. So that the two outer shafts could pass through the after boiler room (between the engine rooms), it had its boilers in tandem rather than side by side, as in the two forward boiler rooms, hence was longer (44ft rather than 24ft). That further separated the two engine rooms. Longitudinal bulkheads enclosed the boilers, adding protection but also adding an off-centre flooding problem if the outer part of the room flooded. In action the machinery would operate in two units, the combination of forward boiler room and forward engine room being self-contained, as were the after boiler room and after engine room, cross-connections being provided. The forward engine room was shortened by moving its generators to the wing spaces abeam the after boiler room, making it less likely that both generators would be put out of action by one hit.
The change cost 20ft in length and 500 tons in standard and full load displacement; total power increased from 64,000shp to 66,000shp. It was claimed that there was no reasonable chance that the ship could be put completely out of action by one underwater hit, and that generators would be better protected. Accommodation would be improved, and DNC expected that the longer hull would be a better sea-keeper.30 Against that, the ship would cost more (about an additional £80,000), it would be somewhat slower (by half a knot), and it could not accommodate the long catapult. Endurance would not be affected. In the previous design, the belt had to extend to the upper deck over the boiler rooms, because the big boilers were so tall. Now the two boiler rooms were no long contiguous, but it seemed unwise to drop the belt back down between them. The high part of the belt was 140ft rather than 76ft long, adding considerable weight. The second funnel crowded the centreline, so that the heavy 53ft catapult could not be accommodated. The 4in guns had to be relocated: now they were all grouped where the after pair had been. Greater length did alleviate overcrowding. DNC strongly advocated the change. So did Controller, who had asked for the redesign in the first place.
Unfortunately the change raised displacement to 5,500 tons. On 24 October DNC passed the word that Plans Division would not accept anything over 5,180 tons, based on total available cruiser tonnage. If the ship were squeezed down to 480ft, she might be cut to about 5,100 tons, which seemed to be about the maximum available. The situation was so bad that a member of the Naval Staff suggested giving up one boiler room, cutting power to 44,000shp and thus speed to 29.5–30kts (at about 5,000 tons). That inspired Controller to suggest using four more powerful boilers. The machinery box would be somewhat longer, but not so long as to break the tonnage limit. To do that, E-in-C accepted higher pressure and temperature than previously.31 About this time the test tank (Haslar) estimated that the ship would need 63,000shp to reach 32kts. E-in-C offered 15,000shp and then 16,000shp boilers.
Lillicrap drafted a DNC memorandum for Controller: he now proposed a 5,180-ton design with the improved subdivision of the 5,500-tonner, reducing its 500ft length down to the 480ft of the original 5,000-tonner, using a four-boiler scheme proposed by E-in-C to Controller on 18 November. Estimated displacement was now the required 5,180 tons (480ft x 49ft 6in x 14ft 3in). The ship was badly cramped because the machinery box was so long. In the original 5,000-tonner it was 178ft long, which was bad enough (in a ‘D’ class cruiser of comparable size it was 146ft long). Moreover, the new ship was intended to have a larger complement than a ‘D’ (initially 550, compared to 470 in a ‘D’ used as a flagship, but now reduced to 500, or to 520 as a flagship). To cram all those men in, accommodation standards had to be reduced. In the 5,500-ton design, the machinery box was 188ft long, but that extra length was more than balanced by the 20ft greater length of the ship. Now the ship was squeezed back to her original length, but the machinery box was 185ft long, meaning even less crew space was available. Lillicrap told DNC that he could cut machinery box length to 185ft if he used six boilers, with four in the forward boiler room (and no bulkhead between the pairs). Perhaps they were trying to do too much on too small a tonnage. For a time it seemed the ship would revert to 500ft length and to six boilers (64,000shp). In the end the planners relented, and on 4 January 1932 Lillicrap was told to go ahead with a 5,500-tonner. Extra weight came from all sorts of sources as the design developed in detail. For example, each of the four boilers was so massive that it was pointless to keep it running in harbour. The ship therefore needed an auxiliary boiler, which was placed in the forward boiler room (this became a standard fixture in later British cruiser designs). One turbo-generator was placed in each engine room, and one diesel generator on each side of the after boiler room.
Subsequent British cruisers all adopted the new machinery arrangement alternating boiler and engine rooms, including the tandem boilers in the after boiler room, and the auxiliary boiler in the forward boiler room, but unfortunately it proved flawed. The spaces outside the two tandem boilers in the after boiler room had enough volume that, when an adjacent machinery space flooded, the ship could quickly capsize. This was entirely unsuspected, because the necessary calculation was too intricate for manual procedures.32 As a result, several cruisers were lost during the Second World War to single torpedo hits. This problem helps explain why the final (unbuilt) British Second World War cruiser designs showed such widely-separated machinery units.
DNC and E-in-C wanted one ship with divided machinery spaces built for initial tests. The first ship therefore replaced one of the three repeat Leanders planned for the 1931/2 programme. The new design received the Board Stamp (as the 5,500-tonner) on 14 January 1932, the idea having been approved by First Sea Lord on 1 January. The Board formally approved the new sketch design on 18 February 1932. The building programme was provisionally cut to nine Leanders, with the understanding that the actual decision on programmes after 1932 would be subject to reconsideration by the Board at that time. HMS Arethusa was included in the 1931/2 programme alongside two Leanders. The Board approved the Legend and drawings on 23 June 1932.33
Arethusa was designed to displace 5,419 tons (standard), but was completed at 5,223 tons. Weight was saved by, among other things, welding, by omitting magazine cooling, and by substituting steel for iron cable. This saving made it easier to add weight after completion. By late 1941 approved additions amounted to 362 tons: splinter protection, protection to vital communications, bottle-rack stowage for 4in shells, 4in twins instead of singles, permanent degaussing, Oerlikons, Asdics, SA gear (self-protection against acoustic mines), radar (including tripod masts), pompoms in place of the catapult and aircraft, a second HACS Mk III, increased complement, etc. Another 375 tons were resisted or compensated for, including steam heating for the Arctic.
Roughly parallel to the intermediate cruiser study was a study of a new version of the slow trade-protection cruiser proposed in 1928, only this time armed with eight 6in guns. In January 1931 DNC asked Lillicrap to sketch a 21kt cruiser protected against 8in fire, to be based on the 5,000-tonner.34 He expected to save so much length on machinery that the fourth 6in turret could be fitted in.35 The ship might be shortened, but that would cost the catapult and considerable fuel oil. Lillicrap sketched 5,000-ton and 6,000-ton ships, both 480ft long (with 49 vs 52ft beam and 14 vs 16ft draft) with single funnels, short machinery boxes amidships, and a catapult between bridge and funnel; HA guns were abaft the funnel. Total magazine length (160ft) considerably exceeded machinery length (about 80ft). Lillicrap submitted his report on 14 January 1931. DNC asked about confining the belt to the machinery spaces but providing the magazines with belt rather than box protection, i.e. extending their protective decks out to the ship’s sides. The belt and deck over the machinery weighed only 465 tons at this point, but that over the magazines would weigh another 930 tons, with another 300 tons for turret supports and another 150 tons for turret roofs, a total of 1,845 tons. To that it would probably be necessary to add protection to the magazine sides against plunging fire – say 100 tons for the lower sides of the magazines (3in thick) and more over the steering gear, and the bullet-proof plating now wanted for bridges – another 100 tons, for a total of 2,050 tons. As with the earlier slow trade-protection cruiser, nothing came of this idea.
Arethusa at Malta, 3 October 1945. Although official records continued to show a Type 272 surface-search radar, by this time clearly it had been removed in favour of a small ‘cheese’ at the head of the foremast. The quadruple Bofors seem to be gone, the ship’s close-range anti-aircraft armament reduced to Oerlikons, with twin power Oerlikons atop ‘B’ and probably ‘X’ turrets. Two single hand-worked Oerlikons are also visible. These numbers do not jibe with the officially-listed armament, which in October 1945 was two quadruple pompoms, four twin power Oerlikons, and three single Oerlikons. (Jack Blumfield, US Naval Institute Collection)
The Improved Leander (Amphion) class
On 2 March 1932 DNC assigned Lillicrap to investigate the desired Improved Leander, to be built under the 1932/3 programme.36 He wanted to know the effect on a Leander of (a) making ‘B’ and ‘X’ triple turrets, and (b) of adopting three triple turrets, and also the effect on these versions of increasing belt armour to 4in, of improving machinery space subdivision, and of improving magazine protection. Existing sketch designs of triple mounts showed that they would weigh 50 per cent more than twins, so in weight terms, (a) was like adding another twin turret. However, there would be subtler increases in the size of ammunition lobbies, magazines, shell rooms and the turret ring on the deck. Lillicrap thought that these increases might be very large, and that it might be necessary to have separate ammunition lobbies for cordite and shell. He had already discovered as much during the 1929 studies of triple turrets. Increased complement, probably fifteen men per triple turret, would be a real problem, since the Leander was already badly crowded, and enlarged magazine and other spaces would consume yet more internal volume. Probably the ship would have to be lengthened, perhaps from the current 547ft to 555ft. With three triples, the added weight and volume would not be as large, so the hull did not have to be lengthened as much (Lillicrap suggested 3ft, to 550ft). Oil capacity would be reduced, because the tankage lost forward (to enlarged magazine spaces) would be less than what was gained aft (the forward tanks were much larger, the after ones being constricted by the propeller shafts). Lillicrap estimated that the four-turret ship would displace 7,500 tons (555ft x 56ft x 16ft 3in), or 7,600 tons with the extra belt armour. On the 72,000shp of a Leander, these ships would make 32.5kts and 32.25kts respectively. The three-turret ship would displace 7,325 tons (550ft x 55½ft x 16ft 3in), the same ship with more belt armour 7,425 tons. As with the four-turret ships, speeds would be 32.5kts and 32.25kts.
The improved machinery subdivision was the alternating arrangement already applied to the Arethusa class. To avoid gross overweight, Lillicrap suggested reducing power to the 64,000shp of the Arethusa, in which case the four-turret ten-gun ship would displace 7,520 tons, the three-turret ship 7,325 tons, and the up-armoured versions 7,640 and 7,445 tons. To accommodate the longer machinery box, the four-turret ship would have grown to 565ft, the three-turret ship to 560ft. Speed would fall below 31kts.
Leander offered magazine protection below 11,000yds and between 14,000 and 21,000yds (as set by the 2in magazine crown) to shells hitting right abeam; below 11,000yds the target would be immune because it was under water. They were altogether immune to 60° attack, and Lillicrap commented that this was ‘very good indeed’. Arethusa was immune below 10,000yds and from 15,000 to 21,000yds. Lillicrap seems not to have estimated the effect of adding magazine protection. A ship with enough oil would probably displace 6,700 tons (545ft [wl] x 55ft x 15ft), which was not too much less than a Leander, or 6,800 tons with a 1¼in deck.
First Sea Lord also wanted to know what could be done with three turrets, with a twin in ‘A’ position, so Lillicrap scaled up the Arethusa to find out and also increased belt armour to 4in, as in the up-armoured Improved Leanders. He thought the combination would displace 6,200 tons (520ft x 53½ft x 14½ft) and would make 31.75kts. This data was passed to DNC on 17 March, who asked what would be required to boost endurance to the 7,000nm (at 16kts) of a Leander. Arethusa managed 5,500nm at 15kts on 1,200 tons of oil (Leander carried 1,800 tons). It would take about 1,800 tons to drive Arethusa at 15kts for 7,000nm. Lillicrap estimated displacement at 6,750 tons. Later (in 1933) Controller wanted to know what could be done if only one of the three turrets was a triple, increasing Arethusa firepower to seven 6in guns.37 The 7,100-ton figure given presumably included much more protection, as in the 1932 studies. Late in 1932 there was also apparently interest in gaining protection by reducing to Arethusa armament.38
HMAS Hobart (ex-HMS Apollo) as fitted, 1939. She was completed with a short catapult fixed amidships for Ospreys and with single 4in HA guns. She was altered to the configuration shown in 1938 for transfer to Australia, at which time the formerly open boat-stowage skids had been decked over. The catapult was removed when she arrived in the Mediterranean in 1941 and replaced by a single quadruple pompom; two Italian Breda guns were mounted side by side on the quarterdeck and four single 20mm Oerlikons were reportedly added. (A D Baker III)
Below and above: HMS Amphion is shown before her transfer to Australia as HMAS Perth. She carries two aircraft, but the catapult had not yet been fitted. HMS Phaeton was completed in this form as HMAS Sydney, without a catapult. Her two sisters were given twin 4in guns before being transferred, and their original 46ft catapults were landed, for later replacement.
The 1932 studies seem to have convinced the Sea Lords that little could be done immediately, apart from adopting the new machinery arrangement. To do that, E-in-C proposed using four 18,000shp boilers instead of the six 12,000shp of a Leander39 As in an Arethusa, the belt had to be raised to cover the higher boilers, and the upper part had to be lengthened to cover both boiler rooms and the space between them. The new machinery space was 9ft longer than in a Leander, but machinery was lighter (1,445 tons rather than 1,504 tons). The longer side protection, with its long upper strake, added topweight which had to be balanced by additional beam (there was apparently no hope of making the belt thicker), so the ship needed more beam. Unfortunately the Leander was already cramped, and a longer machinery box would worsen the situation, particularly since machinery occupied the middle part of the ship, which provided the greatest volume for personnel. The same problem had forced up the size of the smaller Arethusa class.
One of the methods used to ease crowding in Leander was to be abandoned. The Leander design allowed for only half the anti-aircraft guns and half the torpedo tubes to be manned in action. Providing crews for only two of the four anti-aircraft guns saved sixteen ratings; providing for one rather than two sets of torpedo tubes saved another five, and not providing ammunition-supply parties for the 0.5in guns saved another eight. In addition, 25 per cent of the stokers had been assigned to alternative roles (the rules allowed for 15 per cent), saving another seven ratings. The total of thirty-six ratings was more than 5 per cent of the planned number. As the new ship was being designed demands were heard that she be able to fight her whole battery with her designed complement. To shave the demand to a more practicable figure, DNO was willing to keep allowing the 25 per cent of stokers in alternative roles, and to use the Fleet Air Arm ground crew (about seven men) to supply ammunition to the machine guns. DNC had about the same deck space in the new design as in Leander. To squeeze in the additional twenty-three ratings eventually wanted he needed another 3 tons and took other measures: he relocated the auxiliary and second W/T offices and the central stores from the lower to the platform deck. Elimination of a separate bomb room had allowed him to move the HA calculating position from the platform deck (as in a Leander) to the hold, where it was protected.
The heavy catapult of the Leander class had to be sacrificed (this decision was later reversed). The Board had accepted growth to obtain both more survivable machinery and better accommodation, but it had also promised not to reduce the number of cruisers to be built under the London Naval Treaty. Moreover, space was very tight. The forward engine room (above which the catapult was placed) was 4ft shorter in an Arethusa. There was just no space for a heavy catapult, although the ship could accommodate two catapult aircraft, either one fighter/reconnaissance and one spotter/reconnaissance, or two fighter/reconnaissance, or two light reconnaissance seaplanes (the spare was stowed on the superstructure).
HMAS Hobart in December 1944 as repaired following torpedo damage. As refitted, she had RPC 50 for her two quadruple pompoms. Reportedly they had survived the torpedoing, but they were relocated when the ship was refitted. When ‘X’ turret was removed in June 1946, its replacement by a quadruple Bofors was approved, but it is not clear whether this was done. Arrangement drawings for 1945 show a single or twin Bofors on the quarterdeck (the ship had three twin and five single Bofors). Radar at this stage was Type 281B air search, Type 277, Type 276, SG (US-supplied), Type 285 (two sets), Type 282 (two sets), Type 283 (three sets), IFF, Type 251M beacon, FV1 and a jammer. (Paul Webb)
HMAS Sydney was apparently little modified during the Second World War, apart from the provision of splinter shields for her 4in and quadruple 0.5in guns. She was delivered to Australia before her single 4in guns could be replaced by twins. In Australia Sydney (and the other two ships) received a 53ft catapult.
On 28 July 1932 the Board approved the modified Leander, accepting an increase to 7,350 tons (soon corrected to 7,250 tons). This was the Amphion class, all three of which were later bought by the Royal Australian Navy. Ships would be built under the 1932/3 and 1933/4 programmes, the latter being the last likely to be completed under the 1930 treaty. Total tonnage, including the 5,450-tonners, would be 91,300 tons, 580 tons more than the treaty allowed. Controller expected sufficient savings in actually building the ships to make up for this overage. At this point the planned 1932/3 programme comprised two 7,000-ton cruisers (one contract, one Royal Dockyard) and one 5,450-ton cruiser. On laying down HMS Amphion the British government notified foreign powers that she would displace 7,000 tons.
While detail design was proceeding, Controller and ACNS asked for further simplification, to cut both cost and complexity. DNO and DTSD were willing to cut what might be considered important gunnery equipment, accepting elimination of the after DCT, halving the number of director positions. They hoped to gain back some measure of alternative fire control by fitting a small fixed control position aft. With the after DCT went one of the ship’s two duplex rangefinders as well as the ability to split the armament to engage two targets (this applied only to the 7,000-ton cruisers, as the smaller cruisers never had this capability). Costs could be cut further by substituting a destroyer-type fire control clock for the Admiralty Fire Control Table Mk V (a somewhat more complicated Admiralty Fire Control Table Mk VI was adopted). Automatic functions were reduced, increasing the chance of human error, and the fire-control personnel would have to be more highly trained. Recent tests of destroyer fire control clocks (in the shop and at the gunnery school, not at sea) suggested that the approximations involved would not unduly reduce accuracy. CNS concurred with this. The proposal received the Board Stamp on 10 November 1932. These changes were applied to the Leander class cruisers already building (but not to Leander herself).
Above and below: HMAS Perth was practically unique in being fitted with First World War-style anti-rangefinder baffles on her funnels, though she did not have the spiral wires used in the First World War to break up the images of masts in coincidence rangefinders. She was refitted at Sydney, 31 March to 15 April 1940 (when the baffles were fitted). Perth arrived at Alexandria on 24 December to relieve Sydney, and was painted in a camouflage pattern. Perth was repaired at Alexandria between January 1941 and 22 February 1941, when the Type 286 radar on her mainmast was fitted. At that time her catapult was removed and replaced by the two light anti-aircraft guns seen in the camouflage photograph between the funnels. These 20mm Breda guns captured from the Italians (and much liked in the Mediterranean Fleet) were crossdecked from HMAS Sydney to Perth when Sydney left the Mediterranean on 12 January 1941. A third was mounted on the quarterdeck, at least during the Crete evacuation (June 1941). A quadruple pompom (ex HMS Liverpool) was mounted on the catapult deck, probably in May 1941 (presumably for Crete), but possibly during the early 1941 refit (note that it is not visible in the camouflage photograph). The Bredas and the pompom were cross-decked to Hobart when she relieved Perth. Perth left the Mediterranean (relieved by HMAS Hobart) on 18 July 1941, after a short refit at Port Said. At that time she was fitted with a new catapult (from HMS Ajax). When she arrived home, she was further refitted at Sydney (11 August – 30 October 1941). The photograph in gray paint shows the ship after this refit, with Oerlikons on the tops of ‘B’ and ‘X’ turrets. Oerlikons probably replaced the two quadruple 0.5in machine guns in the zarebas on the shelter deck near the bridge, and these guns were remounted right aft, on her quarterdeck, the original third gun remaining in its position abaft the searchlight platform just forward of the after two turrets. A fifth was mounted in a tub abaft the after funnel. At this time the ship was provided with a Walrus aircraft. She was sunk in this form on 1 March 1942. (RAN Historical Branch)
By the time HMS Amphion was delivered to the Royal Australian Navy as HMAS Perth, she had twin 4in guns. Note the absence of a catapult. She was photographed in New York City en route to Australia by Ted Silberstein. (US Naval Institute)
In the spring of 1933 DNO proposed to use long-trunk mountings, which would save personnel by eliminating the ammunition lobby halfway up from the magazine. In an Arethusa class they would save eight men per mounting, and also reduce mess deck congestion (by up to 300ft2). Against that, the 6in magazines and shell rooms had to be lengthened, and magazine armour extended over the shell room. In an Arethusa, that would probably cost 50 tons in protection and about 20 tons of oil fuel stowage would be lost. The idea therefore died.
The detailed design received the Board Stamp on 10 November. E-in-C had shaved a foot from the after boiler room, so the ship was a foot shorter than the design previously submitted, but 8ft longer than a Leander, with 1ft more beam, 6in more depth, and drawing 3in more. Displacement had grown by 250 tons; DNC had managed 100 tons less than initially reported. The situation was actually better, because the standard displacement ultimately approved for the Leanders (Board Stamp 4 June 1931) was 7,154 tons. The modified ship was expected to be less than 100 tons heavier. Beardmore, the machinery contractor for the 1931/2 cruiser (Amphion) being built at Portsmouth, accepted the new machinery design so that this ship was built to the new design. The two large cruisers of the 1932/3 programme (Apollo and Phaeton) were built to the new design. This programme included the second Arethusa, HMS Galatea.
A New Look at Air Defence
While the Arethusa class was being designed, a new naval anti-aircraft gunnery committee was appointed in November 1931 and it reported in April 1932.40 As in 1921, the committee had to rely largely on theory and on exercise experience.41 The threat had certainly grown.42 Compared to the situation in 1921, this Committee had to deal with faster and more numerous attackers, which might fly at higher altitudes. The 1932 report emphasised the threats of precision level bombing and torpedo bombing. It included a kind of dive bombing, but with dives beginning at low altitude (about 800ft) to achieve a good percentage of hits. The report also described (and discounted) US work on higher-altitude dive bombing, of the sort which was to prove so effective during the Second World War.43 Gas attacks were also considered, as was the possibility that enemy aircraft might control unmanned explosive boats (the British actively considered such a weapon in the 1920s, but had abandoned the idea by 1931–2). Yet another possibility was the use of explosive gliders controlled by aircraft.44
Fleet experience suggested that individual aircraft would probably be spotted at a range of about 6–8nm; formations might be seen at slightly greater ranges. The longer the range of the anti-aircraft guns, the longer they could keep attackers under fire, and therefore the better the chance that they would achieve results. As aircraft speed increased, time under fire would decrease. The bursts of long-range AA shells might also be used to indicate to fleet fighters where enemy aircraft were. In theory, two 6in Mk XXII guns (as on new light cruisers) were equivalent to three or four 4.7in or five or six of the new experimental 4in Mk XIV anti-aircraft gun or to eight or nine of the older lower-velocity 4in Mk V. The larger shell reached further, retained its velocity longer, had a flatter trajectory, and had a greater effect when it burst. On the other hand, heavier guns fired more slowly and took up more space and weight. Taking rate of fire into account, one 6in gun was equivalent to 2.3 4in guns (one 4.7in was equivalent to two 4in). A new 5.1in gun being proposed as a dual-purpose battleship weapon was considered far better, equivalent to three 4in guns. The report advocated six 4.7in guns on each side as a minimum; ‘An increase in the number of 4in guns in existing ships can, at best, only be considered a partial remedy.’ The executive summary of the report simplified this conclusion: where the 1921 AA committee wanted four guns able to fire anywhere in the sky, this one wanted six.
The number of AA guns bearing on each broadside was insufficient, and ships were likely to be ineffective because they had only a single HA fire-control position, so could not cover multiple simultaneous attacks. Given available air room no more than eighteen torpedo bombers could attack the head of a line simultaneously. Since typical bases could support several times as many bombers, the fleet might well find itself attacked by several groups independently and in close succession. Succeeding waves had to be countered before the first wave attacked: a ship should be able to engage at least two air targets at the same time. To do that she needed two independent control systems, including director towers aloft and computing positions below decks.
The maximum usable gun elevation was 70°, because much above that the roll and pitch of the ship rendered effective control nearly impossible. Twin mountings were much preferred to single because they took up far less space and thus could have better arcs, were easier to keep clear of main battery gun blast, needed fewer personnel, and they were easier to control. Except for elaborate (between decks: BD) mountings, a twin did not weigh much more than two singles. However, BD mountings offered better protection to crews and their rate of fire seemed to be independent of gun elevation (because the gun could be served from a position well below the deck). They did weigh more and cost more, and they required more structure around them, because they cut substantial holes in the strength deck through which they projected.
HMAS Hobart was torpedoed by a Japanese submarine on 20 July 1943, returning to Sydney on 26 August for a refit which lasted into January 1945. She is shown at its completion. She gained quadruple pompoms with directors abeam the after funnel. The forward pair of twin 4in guns was moved forward. As in other British-designed cruisers, her centreline HA director was replaced by two directors, one to either side of her bridge, carrying standard British Type 285 radars. Note, however, that the face of the 6in director carries the antenna of a US Mk 3 surface fire-control radar. The Oerlikons forward of her bridge were replaced by single Bofors. A third is visible atop ‘X’ turret, and two more are visible at the foot of the forward leg of the tripod mainmast. On the shelter deck abeam the bridge and in the zareba fight aft on the quarterdeck are three Hazemeyer twin Bofors guns. Single Oerlikons are on the shelter deck near ‘B’ turret. Tubs on the face of the bridge and side by side on the mainmast carry Mk 3 barrage directors with their Type 283 radars. The foremast carries an unusual combination of radar antennas: a US SG surface-search antenna at the peak, with a Type 276 surface-search radar below it, two ‘hayrake’ IFF interrogators, and then the dish of a Type 277 (pointed skyward). The mainmast carries the single antenna of a Type 281B radar, with its interrogator above it. The starfish at the top of the tripod carries the four sensing/jamming antennas of the FV1 system. Barely visible forward of the mast is a structure supporting two canted ‘hourglass’ antennas, which serve the associated Type 91 jammer by providing accurate frequency data on the radar being jammed. Hobart was refitted again in 1946, her ‘X’ turret removed, before being placed in reserve in 1947. There may have been further improvements, since later editions of the Commonwealth ships’ characteristics books showed the new Type 274 main battery fire-control radar and two Simple Tachymetric Directors (STDs, equivalent to the US Mk 51). By that time her close-range anti-aircraft armament had been slightly reduced, the five single Bofors and two single Oerlikons being replaced by two power and one hand-worked Bofors and two twin power Oerlikons. However, later editions of the ships’ data book credited her with six STAAG Bofors and four single Bofors Mk 7. This may have been a planned armament. (Photo by Allan C Green via State Library of Victoria)
HMAS Hobart survived the war. She is shown off Wellington, New Zealand, on 22 July 1942, before the Guadalcanal operation. She operated in the Red Sea during the reconquest of British East Africa and Ethiopia, then refitted at Colombo, 19 October through 19 November 1940 en route home. During a further refit in Sydney (June 1941) her catapult and aircraft were landed, so that she could receive further antiaircraft weapons during her coming Mediterranean deployment. Thus she received the cross-decked quadruple pompom and some Breda 20mm guns when she reached the Mediterranean to relieve HMAS Perth (she berthed alongside at Alexandria on 16 July 1941 for cross-decking). Two photographs taken at about this time (she has a dhow alongside, so they were taken somewhere like Alexandria) show the pompom atop the former catapult platform, and a platform for a light anti-aircraft gun on the fore side of her bridge structure. According to a file in the RAN Historical Branch, she and Perth were both given four single 0.303in Vickers guns late in 1941, two forward (side by side on the platform forward of the bridge) and two aft, all of which were to be replaced by Oerlikons, one for one (Perth was lost before receiving the four Oerlikons allocated to her). Other early war modifications were degaussing, protective plating (total about 35 tons) for the bridge and vital communications, and machine gun shields. Ships also had additional depth charge stowage. The ship still had quadruple 0.5in machine guns on the saluting gun deck roughly abeam her HA director forward, and on the centreline abaft and below her after searchlight. At this time she had no radar, as her foretop was still occupied by her circular DF loop. She operated in the Mediterranean between July and December 1941. The catapult support structure itself survived until the major post-damage refit (August 1943 – December 1944). Hobart was ordered back to Australia when Japan entered the Second World War, arriving in Fremantle on 11 January 1942, having experienced a Japanese air raid the previous 3 January at Singapore. Her captain disobeyed an order to land the pompom, and she retained it as she steamed east. Hobart was refitted in Australia some time between early March and late April 1942, at which time a second quadruple pompom (shown in the July photograph here) was mounted on her quarterdeck. The origin of this weapon is unclear, since pompoms were in short supply at the time. Two were shipped from the UK to refit Canberra, but they arrived too late for that ship (one went to HMAS Platypus, and the Admiralty asked in 1943 that both be returned). Canberra was not lost until August 1942, but this July photograph seems to show both pompoms in place. On 22 April 1942 the admiral commanding Anzac Squadron wrote to the Australian Chief of Naval Board that ‘it is considered that the 4-barrelled pompom fitted on the quarterdeck of Hobart together with the six Oerlikons will provide adequate close-range fire power’ which can be read either to mean that the ship had only the pompom there or, more likely, that the addition of these weapons would finally provide adequate close-range firepower. This refit gave the ship two Oerlikons abreast on the platforms forward of her bridge and four more aft, near the quadruple 0.5in machine gun abaft the searchlight (the 0.5in guns were retained). The photograph shows three splinter-shielded positions around the base of the superstructure carrying her after searchlight and her after quadruple 0.5in machine gun; the middle and forward ones clearly show Oerlikons (what appears to be a third, after, one on the starboard side is apparently a control position). She was given 175 tons of pig iron ballast, increasing her estimated deep load displacement to 9,908 tons (compared to 9,130 tons as delivered). At this time she seems to have been fitted with a Yagi-type radar, presumably the New Zealand air-warning type, at her foretop. The ship suffered slight damage in a collision on 6 September 1942 with a US ship. She was repaired and again refitted, this time at Devonport (New Zealand), and after the completion of this refit late in October she spent two weeks in Sydney. According to a note dated 6 October 1942, proposed upgrades included a Type 271 (sic) surface-search radar and replacement of the three quadruple 0.5in machine guns by Oerlikons, for a total of nine. The two navigational rangefinders were removed (they were not needed once the ship had a good surface-search radar). Hobart was fitted with a Type 273 surface-warning set in a ‘lantern’ on the centerline midway between her 4in mounts (Leander, serving with the Royal New Zealand Navy, received a similar ‘lantern’ at about the same time). Either in Devonport or (more likely) in Sydney she was fitted with a US-supplied SC air-search radar on her foremast (using a square reflector, with a characteristic X-shaped brace behind it, rather than the rectangular reflector of the later SC-2 on board many US destroyers) and a US-supplied Mk 3 surface gunnery radar (antenna on the lower part of her DCT). Other Australian warships received these radars, which suggests that they were fitted in Sydney rather than in Devonport. For example, HMAS Australia had Mk 3. Many smaller Australian ships later had SC antennas, examples being HMAS Warrego and the ‘River’ class frigates. The SC antenna is visible in photographs taken after the ship was torpedoed in July 1943, and the Mk 3 is visible in silhouette in a photograph taken just before she was torpedoed. During this refit the Oerlikons were rearranged. Two of the six were moved from the after searchlight structure onto a zareba atop ‘X’ turret. Instead of being mounted on the saluting gun deck, as the forward 0.5in guns had been, it seems that two new Oerlikons were placed atop ‘B’ turret. Two unfortunately unclear 8 June 1943 photographs appear to show some kind of gun in the former saluting deck 0.5in positions, but the usual Oerlikon shield is not visible. Perhaps they were Bredas left over from the Mediterranean, and never carried on official lists. Atop both turrets the Oerlikons were placed side by side. A US Navy recognition silhouette produced at this time clearly shows the turret-top zarebas and the guns on the fore end of the bridge, but unfortunately it is blacked in, hence does not show the structure near the searchlight platform. Both pompoms survived the torpedoing, but during the big 1943–4 modernisation they were replaced by fresh RPC pompoms (with pompom directors) shipped from the United Kingdom.
Small-calibre anti-aircraft weapons presented greater problems, because as aircraft speed increased the available firing time was drastically reduced. The higher the bomber, the shorter the available time, and it was unlikely that level bombers would attack from below 4,000ft (9 seconds firing time). The range at which a torpedo bomber would likely launch its weapon determined how long it could be held under fire. Outside 1,200yds (17 seconds firing time) the target ship could evade (1,650yds for a 40kt torpedo). Future torpedoes might be dropped at 4,000yds, in which case small-calibre guns would be altogether useless. The Mk M pompom was not quite enough, as last-ditch defence envisaged required not its 720 rounds per minute, but at least 1,250. Because there was no associated predictor form of fire control, the gun was fired over simple sights and had to overcome range errors. Performance could be improved, and keep-out range increased (from the currently estimated 1,500yds) by increasing muzzle velocity (ideally, from 1,920ft/sec to 2,500ft/sec) and by streamlining the bullets. The Committee doubted that the quadruple cruiser pompom would meet requirements, preferring some smaller-calibre alternative. It might be time to begin a shift towards a smaller-calibre weapon which could be fired more rapidly. The result was an abortive attempt to develop a multiple 0.661in gun, which featured in many designs in the late 1930s, but never entered service.
Although the value of large-calibre (essentially LA, whatever their maximum elevation) guns for long-range anti-aircraft fire was questionable, the Committee pointed out that barrages by these weapons – firing at preset ranges – could usefully back up the short-range machine guns and machine cannon. Guns would fire at a spread of preset ranges. For example, a heavy cruiser would fire salvoes of at least four rounds. Cruisers armed with 6in guns presented more possibilities, because their shells could be man-handled, hence the guns could quickly switch between anti-ship and anti-aircraft shells. Cruisers prior to the Caledon class had 20° elevation; the later First World War cruisers had 30°, which already offered useful height performance. Only their age and limited space and weight made it unwise to provide them with a modern HACS to engage aircraft at long range. The Leanders had space reserved for a 6in HACP.45 The 6in guns could also be used for close-range barrage fire.
In August 1952 Hobart was taken in hand for conversion to a training cruiser in Newcastle, New South Wales, but the project was cancelled and she was towed back to Sydney incomplete in 1955. She was sold for scrap in 1962; here she awaits the tow to Japan. The most visible modification was replacement of the tripod foremast with a lattice mast like that on board modernised British cruisers. Reportedly she would have been fitted with two sided Mk 6 directors in place of her British-type HA control towers (she would have been training men who would use those directors on board newer Australian ships). Reportedly the directors made for Hobart were installed instead on the Indian cruiser Mysore. (RAN Historical Branch)
Cruisers probably could not accommodate the Committee’s favoured 5.1in gun, so for the future 10,000-ton cruiser the Committee proposed six twin 4.7in on each side (four 5.1in as an alternative). For smaller cruisers, there was no alternative to hand-worked 4in in the lightest possible mountings. Ideally HA mountings should be bunched together to limit complication in control. All 6in guns should be usable against aircraft at long range, and two HA/LA control positions placed on the centreline, plus one or two 4in HADT, depending on gun arrangement.46 If size allowed, the ship should also have two Mk M pompoms and four quadruple 0.5in machine guns.
Like the 1921 committee, the 1931–2 committee devoted considerable effort to long-range anti-aircraft fire control. It proposed two alternative forms of rate-measuring (tachymetric) control. The simpler one measured target angular velocity, vertical and horizontal, directly, and fed those values into a computer. The more complex ‘Flyplane’ adopted after the Second World War translated data into the plane in which the target was flying (it had just been proposed by an assistant to DNO). Both methods were more complicated than the existing HACS, in which an officer estimated target speed directly as an input into the fire-control computer. Both systems entailed complex calculations, not least to translate between data taken relative to a rolling, pitching ship and the aircraft following a more or less consistent path through the sky. None of these systems could be put into service very quickly. In addition to proposing new methods of calculation, the committee pressed for introduction of longer-base anti-aircraft rangefinders (15ft rather than 12ft).
Firing at bombers flying level, ships whose guns could elevate even to 40° might contribute significantly to the fleet’s defence. Thus the committee strongly recommended development of a dual-purpose fire-control system for destroyers and, by extension, for cruisers. It estimated that the combination of mechanical computing and a mechanically-set time fuse (set on the basis of computed aircraft motion) offered a threefold improvement in anti-aircraft effectiveness. Overall, the committee considered improved long-range defence more important than short-range, because long-range fire provided the fleet with collective defence. However, it accepted that a proportion of enemy aircraft would survive long-range fire, and that pompoms were an essential back-up. Smaller-calibre guns (quadruple 0.5in and Lewis guns) could not shoot down torpedo bombers before they attacked, but they could deal with strafers and with aircraft which had to get closer to bomb, such as those dropping the new ‘B’ bombs (buoyant bombs which could rise to explode under a ship’s keel). They could also destroy aircraft and thus prevent them from reloading and reattacking. The Southamptons were the first ships affected by the new recommendations.
The Triple Turret
Once the London Naval Treaty had been ratified, the question was how to fit more guns into a ship of limited displacement. Reviewing attempts to develop a 4,500-ton design on 9 August 1930, Controller wrote that the greatest gain possible in the next few years would be a 7,000-ton ship (a follow-on Leander) with better protection. Triple turrets might provide that weight, so Controller requested a turret design.47 The gunnery school (HMS Excellent) approved the idea of a triple 6in mount in 1932. Triple mounts featured in 1932 discussions of an Improved Leander, which became the Amphion class, but the technology was not yet mature enough to figure in the design adopted. Vickers-Armstrong drawings of a triple 6in turret with cordite hand-up (rather than full hoist) were circulated in April 1933. Like the twin, this was a short-trunk design with lobby or handing room not too far below the gun mounting. DNO estimated a revolving weight of 130 tons, compared to 93 tons for a twin mounting.
Calculations for a sketch design of an Arethusa with a twin turret in ‘A’ and triple mounts in ‘B’ and ‘X’ positions (dated 18 March 1932) are in the Constructor’s Notebook for W G John (Vol 6). Belt armour was increased from 2½in to 4in. Revolving weight of the mounting was taken as 150 tons. John tried various lengths; standard displacement was about 6,200 to 6,500 tons. For example, a ship 520ft (pp) 540ft (wl) x 55ft x 30½ft x 15ft would displace 6,550 tons standard and 8,470 tons deep. A summary sheet dated 31 March 1932 shows two alternatives, both using the 64,000shp Arethusa class powerplant, but with endurance of 5,500nm at 15kts (as in Arethusa) or 7,000nm at 15kts; standard displacement would be, respectively, 6,200 tons and 6,550 tons (deep displacement 7,720 tons and 8,470 tons). Dimensions would be, respectively, 520ft (wl) x 53ft x 29ft 6in (depth) x 15ft and 540ft (520ft pp) x 55ft x 30ft 6in x 15ft. Speeds would have been 31.75kts at standard displacement and 30.25kts deep; and 32kts and 30.5kts for the larger ship, whose length would have more than compensated for her extra displacement.
Compared to foreign contemporaries, the one unusual feature of the Mk XXII triple mount was that the centre gun was set further back than the other two. This was described as a way of saving space.48 Maximum elevation was reduced from the 60° of the twin mount to 45°, presumably indicating a loss of interest in anti-aircraft fire (no heavy-calibre anti-aircraft fire-control system had been introduced). The Mk XXIII, introduced in the Belfast class, was a long-trunk mounting, i.e. it eliminated the ammunition lobby (and its personnel). It equipped the Fiji class and its modified versions.
Surprises
Although British proposals at the London Conference included allowing the US Navy 10,000-ton cruisers with 6in guns, the Admiralty seems not to have taken such ships seriously, since Leander could stand up to any 6in gun cruiser, and she was a far more economical proposition. Surely foreign navies would see this logic. Unfortunately that was not the case. Both the US Navy and more ominously the Japanese Imperial Navy ordered large 6in gun cruisers, of the Brooklyn and Mogami classes.49 Controller added that the newest French cruisers, most clearly comparable to the Leanders, displaced 7,500 tons, and that the additional 500 tons would have been most useful. It would be better to abandon hopes of getting fourteen ships within the Treaty limit in order not to accept gross inferiority. DTD favoured reducing the number to thirteen to ensure that ships more fully met requirements, but did not want to imitate the new foreign ships. Director of Plans pointed out that 6in cruisers were under the same 10,000-ton limit as 8in ships. It might therefore be possible to postpone building large cruisers until the 1934/5 programme in hopes that a competition in cruiser size might be avoided and some agreement reached at the next arms-control conference, expected in 1935. DCNS wanted to wait until late in 1932 to decide the 1933/4 programme, because an arms-control conference was beginning at Geneva in 1932. It might be possible to point out at that conference that cruiser size, hence cost, was being pushed up, and perhaps some action might be taken to cap cruiser size. ACNS agreed. Fourth Sea Lord wanted to concentrate on cruiser quality rather than quantity; numbers could be made up in some other way. Second Sea Lord considered British cruisers deficient in ahead fire, but it would be unwise to follow the foreign navies towards larger, more expensive ships.
A meeting of the Sea Lords and ACNS concluded that it was essential that British cruisers be able to stand up to foreign 6in fire. Protection had to be increased despite the cost in displacement, and gun power had to be increased also, as Second Sea Lord had pointed out. However, it was also important to avoid precipitate action either by an announcement at the Geneva conference or by altering British policy during the conference, which might cause foreign powers to continue building their large treaty-busting cruisers. The agreed policy was therefore to push at Geneva to limit cruisers to 7,000 tons, in the expectation that an 8,000-ton limit could be achieved (7,000 tons would be better from a British point of view). Controller should immediately begin sketch designs for a 7,500-ton improved Leander with improved protection and either ten guns in four mounts (‘B’ and ‘Y’ turrets triples) or nine guns in three triple mounts, two forward. Work should be pressed so that a ship of this type could be included in the 1932/3 programme. Controller should instruct DNO to proceed with the design of a triple 6in turret. First Lord added that if the Board decided to abandon the fourteen-cruiser plan it would have to provide the public with a convincing explanation.
All of this mattered because the international situation was worsening. Japan invaded Manchuria in September 1931 and attacked Shanghai early the next year. The Japanese made unpleasantly clear their determination to expel Westerners from Asia, which directly threatened the vital British economic interest in China. There were already rumblings in Europe, which a Board memorandum said reflected ‘prewar’ thinking. On 15 July 1931, before the invasion of Manchuria, the Cabinet decided that the Ten Year Rule should be reviewed the next year. By March 1932, it was clear that the Geneva disarmament conference was deadlocked, and the Cabinet accepted Chiefs of Staff and Committee of Imperial Defence (CID) papers recommending that the rule be abandoned. The Ministerial Disarmament Committee (set up to develop a British position for the 1932 conference) was converted into the Defence Requirements Committee (DRC) which reported on what was most urgently needed to make up deficiencies largely traceable to the Ten Year Rule – which was scrapped without any formal statement to that effect. With Hitler openly rearming Germany, in 1934 Sir Robert Vansittart of the Foreign Office sought to reverse previous thinking by declaring 1939, five years away, ‘the year of maximum danger’. To make matters worse, in August 1934 the Japanese government announced that it was renouncing the Washington Treaty, effective in two years. Although Japanese delegates attended the 1935 London conference intended to replace the 1930 treaty, their demands could not be met.
Britain already faced an increasingly aggressive Mussolini in the Mediterranean. That sea was an essential Empire line of communication to the East, and the Far Eastern War Plan assumed that the Mediterranean Fleet would be sent East upon the outbreak of war. Any threat in the Mediterranean was therefore to be taken very seriously. Italy attacked Abyssinia in 1935, and the British announced economic sanctions. For a time in 1935-6 it seemed the two countries would go to war. The crisis highlighted inadequate fleet anti-aircraft armament, and the need to counter the large number of Italian motor torpedo boats.
It became clear that Hitler was determined to build a navy grossly violating the terms of the Versailles Treaty. All the British could do was to negotiate a treaty which somewhat limited what the Germans might build. As this agreement was outside the scope of the 1930 treaty, it enraged the French, who felt limited by their own treaty obligations (under the Washington Treaty and under some agreements made after the 1930 treaty). The combination of Japanese withdrawal from the treaty system and the deal the British felt compelled to make with the Germans and also Italian aggressiveness in the Mediterranean all showed that the assumptions made in 1930 were no longer at all realistic.
On 15 July 1936 the British government invoked the escalator clause of the 1930 treaty in time to stop scrapping overage cruisers built during the First World War, and to provide additional tonnage for new construction. By this time the United Kingdom had already agreed to the new London Naval Treaty, which did not include any limits on overall cruiser tonnage, just qualitative limits. There was clearly little point in such scrapping. The British declaration was widely described simply as a decision to retain 150,000 tons of overage destroyers, but it covered ‘C’ and ‘D’ class cruisers as well.
The Southampton class
Given foreign construction of far more powerful 6in cruisers, Director of Plans (H R Moore) considered it very desirable to keep building Modified Leanders in the 1933/4 programme. The official statement of plans to buy ‘probably one Leander and three Arethusas’, was vague enough to allow for the preferable pair of Modified Leanders and two Arethusas. Unfortunately their total of 25,400 tons was 2,330 tons over the allowance (the alternative with three Arethusas would be only 530 tons over, which could be dealt with). There was no real hope of absorbing 2,330 tons. Any weight saved on the Arethusas would probably best go into improving belt protection on the 1933 ships. This programme was sent to the Cabinet.50
The Royal Navy could not continue to build small cruisers which would be outclassed by the new foreign ships. As First Sea Lord (Admiral Chatfield) wrote, ‘We ought to build ships for the defence of our trade similar to those of Japan, but to build the number of ships we require of the size being adopted by other Powers would … be financially ruinous.’ Moreover, under the treaty the four Hawkins class, which were well-adapted to trade protection, had to be discarded. Given the large number of existing (if old) small cruisers suited to fleet work, Chatfield decided to defer such construction for a year while building the sort of large cruisers the Americans and, more importantly, the Japanese, were building.
Some time in mid-1933 DNC was asked to stretch the ten-gun ship to four triple turrets, trading speed (reduced to 30kts) for firepower.51 Apparently a satisfactory combination could be achieved on 7,800 tons, which seems to have been the maximum available. It is not clear how that figure was reached, because the available tonnage would have supported an 8,600-tonner. First Sea Lord proposed to switch from the two Leanders and two Arethusas planned to three such ships. The 30kt speed recalled that chosen for the Surrey class; Chatfield had been Controller when those ships were designed.52
The Staff Requirement for the 1933 cruiser pointed out that the ship was conceived primarily for trade protection.53 It called for twelve 6in guns in triple turrets with elevation for maximum LA range (40-45°) controlled by a DCT forward and by an after control position as in Amphion, with no provision for divided control. The long-range antiaircraft battery would be twin 4in guns in hand-worked weather deck mountings (in the design stage) arranged so that two guns could fire on any bearing, and four guns on the widest possible arc, e.g. 25-165° each side. That could mean two sided mountings plus one on the centreline. All the HA mountings should be grouped together to avoid displacement errors and complications in ammunition supply and would be controlled by a single HACS forward. The close-range AA battery would be three quadruple 0.5in machine guns arranged as in Leander. For trade protection a torpedo armament was not essential; but the ships might have to work with the fleet, so torpedoes were desirable if they did not interfere with the main trade-protection function. If torpedo tubes were not fitted to the ships as built, they should have provision for quick installation of one triple mounting on each side, firing 21in torpedoes capable of 10,500yds at 35kts or 14,000yds at 30kts. As in Amphion, the Staff Requirement called for sufficient complement to operate the entire armament simultaneously ‘but a lesser standard of comfort must be accepted’.
Southampton as fitted on completion, March 1937. Note the DF loop on her foremast and the Asdic dome (a feature of many British cruisers) under her bow. The plating at the sides of the forecastle deck was extended aft about 15ft after completion. Covered crew shelters with blast shielding were added to Southampton and Newcastle after completion; the others were completed with the structures. Sheffield, Glasgow and Birmingham all had a third HA director (Mk III) on the centreline forward of the after control station, and also more rounded bridge fronts. Dotted lines in the plan view indicate the extension of the telescoping fixed athwartships catapult; note that no deckrails for the launching trolley were fitted and that the trolley itself rotated instead of having two rotating sections of the catapult railing, as on the later Fiji class. The 36ft motor and sailing pinnace and the 35ft motor pinnace (fast type) were stowed on skids above the two 35ft motor boats, which were accessed through two large openings in the forecastle deck by the two aircraft and boat cranes. (A D Baker III)
The ship should have a heavy-type catapult capable of launching the heaviest aircraft (the TSR, Swordfish), of which it should stow and operate a minimum of five (two hangared). The TSR offered a cruiser operating on trade routes the ability to sink a raider at considerable range, the ship being supplied with a torpedo for each aircraft, as well as a considerable bomb load.54 There was also still interest in the use of cruiser aircraft to strike and fix an elusive enemy. DNAD proposed a fixed athwartships catapult instead of the usual rotating catapult, whose upper surface would be about 8ft above the upper deck. The hangar floors would be at the same level, with a deck or platform at this level on either side between the after end of the hangar and the catapult. Aircraft could simply be wheeled onto the catapult. The additional 50 tons of structure could be compensated for by reducing 6in and 4in stowage in standard condition by fifty rounds per gun (space would suffice for the full 200 rounds). DNAD’s new catapult had not yet been designed, however, and the dimensions and weight of the TSR had not yet been fixed.
The ships should be protected against the Leander-class 6in shells. Magazines and shell rooms should be immune at all ranges up to 21,000yds, and machinery at ranges up to 16,000yds. Turret trunks should be adequately protected. Other protection should follow that of Leander. Requirements for gas protection were laid out. Speed should be 30kts at standard displacement, and endurance 7,000nm at 16kts (as in Leander). Communications would be as in Leander.
DNC ordered alternative sketch designs KVIII through KX, which were presented to the Board in September 1933.55 All had the previous combination of magazine box protection and belt and deck over their machinery. A comparison with Leander suggested that the armoured part of the ship should be considerably extended to preserve stability in riddled condition (magazine box protection remained). All of these designs had the new alternating boiler and engine room arrangement.56 Length was set mainly by aircraft arrangements and the need for accommodation. KVIII was lengthened (600ft x 62ft x 16½ft, 8,625 tons). Given greater length, it might be possible to achieve higher speed. Thus KIX (600ft x 61ft x 16½ft, 8,740 tons) had 65,000shp rather than 50,000shp and could make 31.75kts.
KX (610ft x 62ft x 16/tft) was conceived to carry five aircraft and to make 32kts (on 70,000shp), and to displace if possible 9,600 tons. The belt armour was extended to cover the bases of the barbettes. It was 5in amidships, tapering to 3in at the ends, with 3in bulkheads angled around the end barbettes. The entire belt was covered by a deck (30lb armour over 20lb structure, total 1¼in). As before, fitting the complement into a relatively small hull was difficult, but this time the Permanent Complement Committee noted ‘with satisfaction’ that the complement of this ship (unlike certain former classes) was receiving due consideration as an integral part of the design. At this early stage, DNC expected less difficulty with officers’ accommodation than with that of the men.57 KIX (presented as Design D) was adopted. A four-shaft 72,000shp plant replaced the previous two-shaft one.
Above and below: The Southamptons marked a dramatic change in British cruiser design, to counter large foreign types such as the Japanese Mogamis. HMS Gloucester is shown, newly completed, in 1939. Earlier ships in the class could be distinguished by the absence of a third HA director, on the after superstructure just forward of the after 6in director. Southampton and Sheffield, for example, were completed without any directors aft.
Sheffield is shown as she appeared from late July 1943 to the beginning of her early 1944 refit, i.e., as when she participated in the Battle of North Cape against the German Scharnhorst. Her aircraft arrangements had been removed, four single Oerlikons (two to port, two to starboard) being mounted on the former flight (catapult) deck. The rest positions of the cranes were moved to clear these guns (they were originally at the deck edge, and had to be moved inboard, almost touching on the centreline. That gave just enough clearance. She also had ten other Oerlikons. (Alan Raven)
A Legend constructed in October 1933 showed a displacement of 8,835 tons (standard). Before submission to the Board on 25 October waterline length was reduced from 600ft to 584ft, so that the ship could dock more widely.58 Because shaft horsepower was not increased, speed at standard displacement fell from 32kts to 31.75kts. The length of protected waterline was extended at the cost of reduced thickness.59 Two of the three 0.5in machine guns were replaced by two quadruple pompoms (1,400 rounds per barrel), the remaining machine gun being mounted on the after control positions.60
Controller submitted this 9,000-tonner to the Board on 25 October. Controller wanted the pompoms relocated to better positions for dealing with dive bombers. The most obvious change in the design was a reduction from five to three aircraft, suggested by DNC because there was not enough space.61 Controller doubted that the fixed catapult envisaged by DNAD was worth the extra 50 tons, but First Sea Lord (Chatfield) overruled him; aircraft were very much what a cruiser needed. It was always possible, moreover, that larger amounts would be saved during construction. DNAD’s fixed catapult characterised later British cruisers. The ship could carry three TSR, one on the catapult and one in each of the two hangars, with their three torpedoes. The Board approved the 9,050-ton sketch design on 9 November 1933. By this time the ships were called the ‘M’ class, the first ship being Minotaur. With their greater tonnage, there was no longer room for three of them in the 1933/4 programme, so an Arethusa (Penelope) was substituted for the third ship. Later HMS Minotaur was renamed Southampton, that becoming the class name.
Photographed in November 1942, Glasgow displays typical wartime modifications: zarebas atop ‘B’ and ‘X’ turrets for Oerlikons and Type 273 surface-search radar atop her bridge (installed in August 1942). During her first wartime refit (Liverpool, 14 May – 7 July 1940) Glasgow was fitted with UP mountings atop ‘B’ and ‘X’ turrets and with Type 286 radar. She was torpedoed at Suda Bay on 3 December 1940 and travelled nearly around the world for repairs: first to Alexandria for temporary repairs, which enabled her to reach Singapore for more temporary repairs (29 June – 29 August 1941, including removal of the UP launchers), then to New York Navy Yard for permanent repairs and a refit (6 May – 25 August 1942). Her Type 286 radar and her quadruple 0.5in machine guns were removed, and nine single Oerlikons, which are visible here, were fitted. She also received standard large-cruiser radars: Types 281, 282, 284, 285 and 273. Further work was done at Portsmouth (4 September – 1 2 October 1942) and on the Clyde (6-23 December 1942); during the latter availability she exchanged five single Oerlikons for eight twins. Two more single Oerlikons were added during a Devonport refit the following year (26 August – 6 October 1943). She was damaged by German shellfire when bombarding Cherbourg (25 June 1944), and was further refitted and repaired at Portsmouth (June 1944 – May 1945). By this time ships had no further reserve topweight to allow installation of more close-range antiaircraft weapons, so ‘X’ turret and the ship’s aircraft arrangements (catapult and one crane) were removed. Now there was space and weight for two more quadruple pompoms and for four single power-operated pompoms. Two twin and four single Oerlikons (including those on turret tops) were landed. The ship’s radars were modernised: she was fitted with the single-antenna Type 281B, which cleared the foremast for the Type 293 target-indication radar. Her Type 284 fire-control radar was replaced by a centimetric Type 274.
DNC submitted the Legend and drawings on 28 February 1934.62 To better support the heavier belt and to stiffen the hull, the ship reverted to 4ft rather than 6ft frame spacing over the main part of hull, at some expense in weight.63 Turrets were lowered by sinking their roller paths below the weather deck, the ring bulkheads being structurally independent of decks near them. The trawler bow of the Leanders was retained. The HADT was on the bridge, immediately abaft the DCT, controlling three twin 4in between the after funnel and the mainmast (one on either side on forecastle deck level, one centreline on superstructure level). The pompoms were on either side atop the hangars, with directors on either side of the foremast. DTM’s proposal for quadruple torpedo tubes was rejected. Space sufficed for 790 officers and men (as a wartime flagship). The hangars created a blind arc for the waist 4in guns on forward bearings at low angles, so they were sponsoned out. Waterline length remained at 584ft, but shaft horsepower increased to 75,000, to give 32kts at standard displacement and 30.5kts at deep load. Main machinery was arranged as in Amphion and Arethusa. Endurance was as in Leander, 7,000nm at 16kts. The Legend and drawings were approved on 8 March 1934. Further work showed that 200 tons more fuel could be carried at the cost of 5 tons of standard displacement, giving an endurance of 8,900nm at 16kts. The Board approved this change on 15 March 1934.
In September 1934 D of TD suggested withdrawing the 1932 orders to simplify cruiser fire control, as they were inappropriate for a ship the size of the new 9,000-ton cruiser. The 10,000-ton cruisers were already getting a second HACS each, so that they could engage aircraft on both sides simultaneously, so surely a 9,000-ton cruiser needed the same capability. The single centreline HADT was replaced by two, one on each side of the bridge atop the hangars, the bridge being narrowed to clear arcs for them.64 Hold space was found for a second calculating position (computer space). Leander had experienced DCT interference from the cordite smoke from the fore turrets, so the DCT in the new ship was raised by raising the upper bridge so that its screens were just above the tops of the HADTs on either side, with a clear view all around except right aft, and overhead. The roof atop the compass platform was omitted. It proved possible to move the HADTs slightly outboard so that wind deflectors could be fitted around the entire compass platform. DNC proposed raising the forefunnel 10ft to minimise smoke interference with the raised bridge. The searchlights could move to positions alongside the funnel.
HMS Glasgow off New York Navy Yard on 11 August 1942.
At the same time a fourth twin 4in was added. That had been considered impossible (hence the centreline mount), but space was freed by eliminating the torpedo parting (assembly) space. The magazine could not be enlarged, so only 150 rounds could be provided for each 4in gun, despite recent policy favouring more rather than fewer rounds per antiaircraft gun. Adoption of bottle-rack stowage solved the problem. There was interest in replacing the 4in hoists with duplex hoists, which could more easily supply two pairs of guns on each side (the existing hoists provided thirty-six rounds per minute, sufficient for one pair of twin mounts). Adding the fourth twin 4in reduced boat stowage on the after superstructure deck, but some boats were stowed instead on the upper deck in a well in the superstructure deck.
D of TD wanted a second LA director or an HA/LA director aft (although there was not enough space for a third HA calculating position below decks), the single existing LA director being wooded on bearings from about 136 Red to about 135 to 156 Green. The two 1933 ships received the fixed control position of the previous classes, but 1934 ships had an HA/LA director. The centreline position for the one quadruple 0.5in machine gun was eliminated when the mainmast was moved to clear arcs for the new after director; it was replaced by two such guns, one on either side. The existing after 36in searchlight and two displaced from forward were grouped around the mainmast, one being immediately abaft the after funnel. The central part of the after searchlight platform became an alternative conning position for the ship.
A review of the building drawings suggested to DNC that the ships would come out at 8,947 tons rather than the planned 9,060 tons. His suggested use of the small difference for more armour was approved by the Board on 4 October 1934.65 New drawings were approved on 9 May 1935, and new building drawings issued accordingly in July. Displacement increased to 9,060 tons. Slightly later the Board decided to rake the masts and funnels at a slope of 1:6.6.66 This seems to have been considered preferable to moving the forefunnel abaft the bridge. The bridge front was curved to improve air flow around it.
Designed for 8,947 tons standard, Southampton was competed at 9,083 tons; approved additions between design and completion were small additions to armament and to protection, bridge modifications, additions to hangar structure, ring main modifications, etc. By late 1941 approved additions without compensation amounted to 324 tons. They included splinter protection, protection to vital communications, additional 4in bottle-rack stowage, permanent degaussing, Oerlikons, SA gear, radar, cutters as sea boats, hangar spraying, additional bridge stiffening etc. Proposals resisted or compensated for included Type 271 radar and steam heating for the Arctic.
Repeat Southamptons
Under the London Naval Treaty of 1930, additional cruisers could be laid down in 1934 to replace the fifteen ships which would become overage on 31 December 1937 (67,350 tons) and in 1935 the four which would become overage on 31 December 1938 (19,000 tons). No further tonnage would become available for replacement in 1936. However, the Royal Navy was reluctant to keep scrapping its overage cruisers. Thus the 1934/5 programme amounted to three more big cruisers (Glasgow, Sheffield and Birmingham) and the last Arethusa, totalling about 32,500 tons. The only important change was continuously flared bow lines in Birmingham, apparently for comparison with the trawler bows in the others.67
By May 1935 it had been decided to order three repeat Southamptons (Gloucester class) in the 1935/6 programme. Initially the only planned change was to accept E-in-C’s proposed higher rate of forcing, giving 82,500shp at a cost of 70 tons. In November, DNO proposed additional protection to the turrets, to provide a 4in face, 2in roof and sides, and 1¾in floor, at a cost of 35 tons per turret; previously the gunhouses had been 1in with ½in floors. The additional armour would help protect the 6in magazine from bombs. The magazine crown was open for the ammunition hoists directly under the turret. To compensate for the added topweight, the ships needed 8in more beam. DNO (Fraser) suggested that protection to the ammunition supply should also be increased. Controller (Henderson) approved 2in over the ammunition supply below the turret, pointing out that the hoists from magazine to handing room were not protected and that they too should receive 2in protection. The weight involved was small, and would not require more beam (which would have required that ships’ lines be relofted).
DNO pointed out that in the past boilers were protected not only by the armour above them but also by the unarmoured decks higher in the ship. In these ships (and, for that matter, in the Amphions and Arethusas) the boilers were so tall that the decks over them were the upper decks. He suggested adding another quarter-inch to the 1½in deck already present, balancing the extra weight by removing the torpedo tubes. ACNS rejected the idea. Torpedo tubes had been removed in the Kents, and would probably be removed when the Londons were modernised, but other cruisers should retain them; torpedoes were a potent weapon for night and low visibility. First Sea Lord agreed. The added weight (195 tons in all) and slight additional increase in beam were accepted. The modified design received the Board Stamp on 13 February 1936.
In service the thicker deck caused an unexpected problem. In rough weather with the Home Fleet in 1940, the abrupt change in thickness at the ends of the thick upper deck caused structural problems due to stress concentration in HMS Manchester. In the Gloucesters the change was abaft the forecastle rather than in a space covered by the forecastle (as in Belfasts and Fijis), which was a strength deck. The cure, to be applied to future classes, was to make the transition between thicker and thinner decks smoother – at a significant cost in topweight. In 1940 the ships involved, the Fijis, were already so badly overweight that DNC was fighting every proposed addition, threatening that the after two 4in mountings, catapult and aircraft would have to be surrendered if extensive splinter protection was added. Fortunately the Dido class structural design, similar to that of the Arethusas, showed no such problems.
Belfast and Edinburgh
There was plenty of weight left for new cruisers, particularly after the United Kingdom invoked the escalator clause in the 1930 treaty. The 1936/7 programme included seven cruisers, two follow-ons to the Southamptons and five Didos (see below). These were the last ships to be laid down before the 1936 London Naval Treaty, which restricted new cruisers to 8,000 tons, came into force on 31 December 1936. The Royal Navy was therefore free to use all 10,000 tons available in HMS Belfast and Edinburgh.
Initially the basis of the design was a new quadruple 6in turret. It was not expected to be much heavier than the triple, but additional protection would be needed. Later, when the quadruple design had been worked out, it was expected to weigh 188 tons, with 3in shield and 2in roof. The mount had a long trunk, i.e. no ammunition lobby to isolate magazines from turret (hence fewer personnel). On 8 October 1935 DNC asked for a cost estimate for a 10,000-ton cruiser with four such turrets, speed 32.5kts, and other features similar to those of the Southampton class.68 The hull had to be lengthened (by about 20ft) to allow wider turret spacing. Scaling the 9,100-ton Southampton to 10,000 tons gave a similar length, about 602ft (say 605ft) based on the 584ft of the smaller ship.
Belfast as fitted, November 1942, after her major reconstruction, when she was bulged. She had been mined in the Firth of Forth on 21 November 1939. The post-reconstruction beam reported in Admiralty documents varies between 66ft 4in and 69ft, the latter seeming more accurate when scaled off surviving drawings. Note the long railed system on the upper deck to supply ammunition from the magazine, forward of the machinery, to the 4in guns (this arrangement was adopted to minimise propeller shaft length, hence vulnerability to exactly the kind of under-the-bottom attack which put the ship out of action for three years). Aviation facilities were removed, but the catapult, which was inoperative, remained until the 1944-5 refit; one boat/aircraft crane was removed and the other relocated to the centreline just abaft the former aircraft hangars to handle the relocated boats. The 27ft whaleboats in the ‘pockets’ amidships were launched and recovered via an extended overhead rail system. The sliding doors that could cover the torpedo tube area are shown in their open position behind the vertically-stowed Carley life rafts. Ship’s boats in November 1942 included one 36ft motor pinnace, three 35ft fast motor boats (one of Vosper design), two 32ft cutters, one 25ft fast motor boat, one 16ft motor dinghy, and two 14ft dinghies. Belfast was refitted between 4 August 1944 and May 1945, in part to prepare her for intense air attacks to be expected when she deployed to the Pacific. The two after twin 4in were removed and she emerged with two octuple, four quadruple, and two single power pompoms, three single handworked Bofors Mk III, two Boffins (single powered Bofors), two twin power Oerlikons and one single Oerlikon. Boat stowage was moved forward to the former aircraft-handling deck, but the 32ft oared cutters were still stowed beneath individual gantries on the main deck abreast the after funnel. Belfast was further refitted to prepare her for Korean War service, and then modernised in the late 1950s. At that time her tripods were replaced by lattice masts and her bridge superstructure completely rebuilt and enclosed. (A D Baker III)
On 5 April 1936 Controller (Henderson) reported to the Board two studies of modified Southamptons: one with three turrets forward, arranged as in the battleship Nelson, and one with five triple turrets.69 The ship with turrets forward had the same aircraft arrangements as in Southampton, but she was longer, so belt armour had to be trimmed (by not more than ½in) to stay within the 10,000-ton limit, and the Southampton machinery would drive her at a slightly slower speed. The five-turret design required about 450 tons more, but in that form it did not trim properly, and it would be difficult to fit in the required complement. Controller added that he expected to hold the Southamptons to 9,000 tons rather than 9,100 tons, so he could devote 10,000 tons to each of the 1936 ships without exceeding the planned total of 95,000 tons for the entire ten-ship Southampton class.70 The 1936 ships became the Belfast class.
On 24 October DNC asked for two new sketch designs: KXIV and KXV.71 KXIV would have three triple 6in turrets (if possible, all superimposed) forward and two aft. He hoped that space could be found for more twin 4in anti-aircraft guns. Power would be 82,500shp. All of this should be done within a 10,000-ton limit – which was not impossible, given that the US Brooklyn class had five triple 6in mounts on under 10,000 tons. KXV had four quadruple 6in turrets. Protection, aircraft arrangements and other features were as in the Southampton class. To add the extra turret, KXIV needed another 36ft between ‘B’ turret and the foremast (23ft magazine and 13ft shell room). This length would also provide accommodation for the sixty-seven extra personnel needed. Stability could probably be maintained by adding a foot of beam. That would give 620ft (wl) x 62ft 8in x 17ft, and a displacement of 9,720 tons based on the Southampton hull form (but not the necessary weights). If necessary, a bit more could be added for stability (say, a beam of 63ft 8in) and the bilge could be filled out. This was not bad; a preliminary check of weights based on the Southampton class expanded to the new dimensions, with the new ‘C’ turret, suggested a standard displacement of 10,005 tons, which could easily be shaved to the desired 10,000 tons. Estimated speed was 32.5kts. This design did not allow for any additional anti-aircraft armament, because it lacked both space and weight. Weight could be clawed back by shortening the ship slightly, but her topsides were already congested. However, the weight gained that way would buy a fifth twin 4in mount. As that would not offer a symmetrical layout; the torpedo tubes could be traded for a sixth 4in mount. The longer ship would not, however, be able to use three graving docks open to the Southampton class: Hong Kong No. 1, Gibraltar No. 2, and Malta No. 5.
Above and below: HMS Belfast and Edinburgh were the largest pre-war cruisers. Edinburgh was lost in 1942, and Belfast was almost lost in 1939 when a magnetic mine broke her back. The blisters used to regain her hull girder strength also provided enough reserve buoyancy that, unlike contemporary British cruisers, she never had to lose one 6in turret (although two of her six 4in mounts were removed). HMS Edinburgh is shown newly completed.
Edinburgh is shown en route back to Scapa Flow, as seen from USS Wasp, April 1942. Her escort is a US destroyer. She received her Type 279 radar (antennas on both masts) during a refit at South Shields (20 March – 28 October 1940). Six single Oerlikons were fitted when she docked at Gibraltar in July 1941. When this photograph was taken, she had only recently emerged from a refit on the Tyne (17 January – 4 March 1942). She was fitted with a Type 273 surface-search radar atop her bridge plus gunnery radars (Types 284 and 285). Note that she retained her HF/DF coil on her mainmast, below the radar antenna. Her Oerlikons were unshielded: one is visible atop ‘B’ turret, one is on the shelter deck level below the bridge and abaft ‘B’ turret, and two more are visible on her quarterdeck; presumably the sixth was atop ‘X’ turret, hidden by the after director. She was sunk on 2 May 1942.
DNC asked for six twin 4in in KXV. The 4in gun deck had to be lengthened at least 28ft (which might be managed on a ship 21ft longer). The ship could be shortened by making the 6in magazines and shell rooms wider (18ft instead of 14ft) to make them 10ft shorter. All of that might be possible on a 605ft hull, which scaled up to 9,900 tons. Tentative weights showed another 92 tons for the quadruple mounts with heavier shields, a relatively small increase. It might make sense to abandon the earlier box protection for the magazines and shell rooms, relying on the external belt (180lbs, or 4½in) and deck armour, with 100lb (2½in) bulkheads.
In slightly modified form (614ft, six twin 4in) KXIV was presented to the Board as alternative A. KXV was presented as Design B. After a Sea Lords meeting on 7 November 1935, DNC ordered a third alternative (C, KXVI): four triple 6in turrets, six twin 4in anti-aircraft guns, two quadruple pompoms, and two 0.5in machine guns. Protection improvements were a 3in rather than a 2in magazine roof, 2in rather than 1¾in over machinery, turret roofs as in the projected quadruple mounts, and long trunks as in the quadruple mounts (with 3½in protection). The Staff wanted a speed of at least 31kts. The triple-mount designs had long trunks like the quadruple 6in. Eliminating their handing rooms made it possible to bunch turrets more closely, their centres 32ft rather than 36ft apart.
A quick estimate suggested that this KXVI would come out to 10,203 tons and would make 32.25kts on 70,000shp (31.5kts using Arethusa machinery). In view of the excess displacement, DNC ordered a fourth study, using the Southampton hull (584ft long) and the same power (82,500shp) with the same armament but with improved protection: 2in rather than 1¼in deck over machinery; 3in instead of 2in over magazines; turret shields thickened (but not quite as in Gloucester: 4½in face, 2in roof, 3in sides); and turret trunks and hoists covered by 3½in sides and 2in ends. The belt was the same 4½in thickness, but it was extended aft. Estimated total protection weight was 2,010 tons, compared to 1,478 tons for the 1935 version of the Southampton class. The increase of about 600 tons could be divided into 300 tons to improve turret protection against shellfire and 300 tons to improve deck protection against dive bombing. A 3in deck was considered proof against 500lb bombs dropped from 8,000ft or below, a 2in deck proof against 250lb bombs dropped from that altitude. Standard displacement would probably rise to at least 9,700 tons (increased protection weight would also increase hull weight, to avoid extra stresses). Speed would be about 32kts. Draft would be a foot more (18ft), so freeboard would be a foot less. The ship would lose a quarter-foot of metacentric height, making that about 2.9ft.
The next step (KXVII, Design D) was a Southampton with a new machinery layout, requested by Controller on 13 November. Shafting length was reduced to make the ship less vulnerable to shock (which could bend a propeller shaft) from ‘B’ bombing and to torpedoes (presumably particularly those with non-contact, i.e. magnetic, fuses). The alternating engine and boiler room arrangement adopted in the Arethusa class and continued in later cruises made for particularly long shafts from the forward engine room. Controller wanted revert to the earlier arrangement of two boiler rooms forward of two engine rooms, both boiler rooms being short, and with the 4in magazine moved from aft to forward. He envisaged a 10,000-tonner, but DNC decided to apply the idea to a Southampton. The existing alternating arrangement was 187ft long; the earlier type of machinery arrangement would be 168ft long, but would have an extra generator room on the centreline forward of the forward boiler room. The boilers in the after room would not be in tandem. The older arrangement would entail only a single funnel, and 18 tons might be saved, plus another 18 tons due to the reduction of shaft length and the shift in position of the 4in magazine. The ship would not be shorter overall (due to the length of the generator compartment outside the engine and boiler rooms), but the side armour would be reduced, saving another 84 tons. The new arrangement would raise a few other problems, such as difficulty in arranging the wireless office aft under protection, and the fact that one or two more cranes would be needed (25 or 50 tons more) because the boats would be separated from the aircraft. Another study made at this time showed that eliminating the torpedo tubes would save about 40 tons. Design C was favoured, but it was too stiff, so in a revised version (K18) beam was reduced slightly to reduce metacentric height to the desired 3ft in standard condition.
Belfast as refitted, 1942, with a very visible blister. The refit seems to have entailed about as much effort as building a new cruiser; but Belfast gained so much reserve stability that she had more capacity for improvement than any other modern British cruiser, and hence survived longer. She was mined on 21 November 1939, repaired temporarily at Rosyth (21 November 1939 – 27 June 1940), and then rebuilt at Devonport (3 July 1940 – 8 December 1942). While work was proceeding, requirements and technology (particularly radar) were changing, which must have complicated the project very considerably. Unlike smaller British cruisers, she had what was considered a nearly adequate close-range battery, so the main change was exchange of the previous quartet of quadruple 0.5in machine guns for five twin and four single Oerlikons. Note the twin power Oerlikon atop ‘B’ turret and the two right aft on the quarterdeck. Modern radars were fitted: Type 281 on the masts, Type 273 in a ‘lantern’ on the bridge, Type 284 for main battery control, Type 285 for heavy HA control, Type 282 for pompom control, and Type 283 for barrage directors. The FV1/Type 91 radar intercept/jamming combination was installed on her mainmast. Four single Oerlikons were added at Rosyth during a docking (18-29 June 1943). In this form she helped sink the German battlecruiser Scharnhorst. When docked afterwards at Rosyth (5 April – 8 May 1944) she had one twin Oerlikon removed and six more singles added.
On 17 February DNC asked what protection the big cruiser could have if speed was set at 32.5kts. The ship would revert to Southampton class protection except for 1¾in decks over machinery spaces and main W/T; 1½in deck over transmitting station etc; 3in decks over magazines and shell rooms; and 4½in turret face, with 2in sides and roof. This and designs since the Amphion had added considerable armour weight by having a belt of uniform height (up to the upper deck) over the forward engine room as well as the boiler rooms. How much could be saved if the belt and deck over that engine room were dropped to lower deck level? In that case a large part of the upper deck amidships would provide only strength; how thin could it be? It turned out that even if it were not considered protection, the upper deck had to be fairly thick (45 to 50lbs, i.e. 1⅛–1¼in instead of 2in, 80lbs).
The Board chose triple rather than quadruple turrets. This decision was later attributed to uncertainty about the necessary distance between turrets. The weight saved went into deck protection. Magazine spaces were shortened, so the ship was shortened by 10ft. To save weight, the belt and the deck over it were shortened at the fore ends, the 6in magazines and shell rooms receiving the earlier kind of box protection. That left all important control positions under the remaining extension of the belt and deck forward of the machinery spaces. Added weight made it possible to thicken the deck from 1¼in D to 2in NC armour. The 4in HA mountings were rearranged to minimise mutual blast interference, and the pompoms moved forward to be clear of the blast of the after 6in guns (they were still vulnerable to blast from the midships 4in guns, which was unavoidable). Design was slightly simplified because reduced clear 6in arcs were accepted, 140° each side rather than 145° in Southampton (135° had been accepted in the quadruple-turret design). DNC was instructed to go ahead with detail design (on 13 May 1936). At this stage ACNS asked that octuple pompoms be substituted for the quadruples, at a likely cost of 50 tons (this was done). He also wanted better steering-gear protection. For greater propulsive efficiency, propeller revs were reduced from 350rpm to 300rpm, so on the same size and weight the machinery produced 80,000shp rather than 82,500shp. This revised sketch design received the Board Stamp on 29 May 1936.72 Legend and drawings received the Board Stamp on 21 July 1936. Armour was again somewhat revised.73
Belfast is shown after her last wartime UK refit, on the Tyne between 4 August 1944 and May 1945. Note the elimination of the twin power Oerlikon atop ‘B’ turret, but the retention of the two guns (with blast screen) on the quarterdeck. Two of the six 4in mountings and the aircraft arrangements were removed, as the ship was finally stability-critical. Four quadruple pompoms and four single pompoms were fitted, and eight single Oerlikons were landed. The ship’s radars were modernised, her foremast cleared by replacing Type 281 with Type 281B. That left space for the Type 293 target-indication radar at the foretop and the Type 277 surface-search/height-finding radar (its dish is turned horizontally). A Type 268 navigational radar was installed, and the earlier Type 284 main battery set replaced by a Type 274. When the ship reached Sydney she was docked (August 1945) and additional close-range weapons added: three single hand-operated Bofors (one atop ‘B’ turret, one each side atop the former hangar); two Boffins (power Bofors on the mountings developed for twin Oerlikons) replaced two twin power Oerlikons.
As in previous cruisers the engine and boiler rooms alternated, but the machinery box was moved aft, presumably to shorten propeller shafts as a defence against ‘B’ bombing. That in turn squeezed the after 6in turrets, which were moved up a deck. The result was a somewhat odd appearance, the funnels being moved well aft of the bridge structure, leaving a conspicuous gap amidships. To make space for the machinery, the 4in magazine was moved forward, making for an awkward arrangement of ammunition supply along the deck. Belfast, one of two ships so redesigned, was the only British cruiser to fall victim to a non-contact explosion, when her back was broken by a German magnetic mine in November 1939.
The 6in turrets were the long-trunk type, served by DCTs fore and aft, and there were three HACS, one each side forward above the hangar, and one on the after superstructure. The 0.5in machine guns were placed one each side of the hangar top forward, the pompoms being moved back to platforms aft platforms above and inboard of the middle 4in mounting, their directors on either side of the after superstructure.
When she fought in Korea, Belfast was in much the configuration she had when she emerged from the Sydney refit in 1945. She is shown on 5 August 1952. All Oerlikons had been eliminated. She had the wartime pompoms (two octuple and four quadruple), five single hand-operated Bofors guns, two Bofors Boffins, and two single power-worked Bofors of post-war design. By way of contrast, in April 1946 she had three single Bofors and two Boffins plus four twin power-worked Oerlikons and four singles. Her four single power-operated pompoms had already been landed. (USN photo courtesy of Rick E Davis)
The ship was now very close to 10,000 tons – on paper. On 3 October, in connection with a proposal to make the 2in deck continuous over belt and forward magazines, Controller decided to apply a margin above the treaty limit (in this case 10,000 tons) in the expectation that, as in the past, DNC would find it possible to shave weight during construction. In the new cruiser, that made it possible to provide a continuous 2in deck from forward to after magazines, at an estimated cost of 135 tons. The same policy was applied to other ships, such as the next class of large cruisers (the Fijis). At one time British designs had all included a Board Margin allowing for growth up (not down) into their nominal displacements. Once the treaties were signed, such margins had been eliminated.
The two Belfasts were the largest British cruisers built since the ‘Counties’, with the heaviest anti-aircraft batteries of all. During construction Edinburgh had gained 302 tons in approved additions: bridge extension, pompom platforms, blast screens to 4in guns, protection to lower decks, bullet-proof screens, extra armament, increased complement, electric ammunition hoists, etc. By late 1941 another 145 tons had been added without compensation: strengthening for her upper and forecastle decks, additional stiffening and pillars, permanent degaussing, Type 279 radar, paravane clump and chains, hangar spray pump, side scuttles, SA gear; etc. DNC resisted or compensated for another 260 tons, including 75 tons of splinter protection successfully resisted: 42 tons for items including Types 271, 282, 284 and 285 radars, Oerlikons, steam heating, and increased complement for which compensation was demanded.
When Belfast broke her back after triggering a German magnetic mine in 1939, she was considered worth rebuilding despite the effort involved. She did not emerge until late in 1942, by which time her sister-ship Edinburgh had been sunk. The most prominent changes was blistering, to regain stability due to topweight growth.74 Nearly all other British cruisers had ‘X’ turret removed during or immediately after the Second World War to regain stability so that radars and additional light anti-aircraft weapons could be added. Given her blisters, Belfast had sufficient stability, so she retained all four 6in turrets to the end. As inclined in October 1942 her light displacement was 11,400 tons. She had the full radar suite, Remote Power Control (RPC) for her two octuple pompoms, and ten Oerlikons plus ten twin Lewis guns in place of her two quadruple 0.5in machine guns. By September 1944 she had two twin power Oerlikons and fourteen single mounts. During a spring 1945 refit an Action Information Organisation (AIO) was fitted and aircraft facilities removed, close-range anti-aircraft armament being upgraded by adding four quadruple pompoms and four single power-worked pompoms, for a total of thirty-six pompom barrels. She now had four twin Oerlikons and six singles, a total of fourteen Oerlikons. As inclined on 2 May 1945 her light displacement was 11,919 tons (against an estimated 11,758 tons taking account of known additions). These additions included the Type 274 fire-control radar and fittings to fuel at sea. The unknown 161 tons was considered reasonable growth over 2½ years in a ship which had not been asked for compensation. She was refitted again at Sydney (completing in August 1945) for Pacific Fleet service. Two twin 4in were landed, two of the twin power Oerlikons were converted into Boffins (single powered Bofors guns) and three single Bofors were added, one atop ‘B’ turret in a zareba. Two of the single Oerlikons were also landed. By this time all the multiple pompoms had RPC.
In 1933 the Royal Navy was on the verge of building the big Southamptons, but many cruiser duties, such as supporting fleet destroyers, demanded much smaller ships. On 16 August 1933, at First Sea Lord’s direction, Captain Tom Philips, Director of the Tactical Division, sent a letter to the two main fleet commanders asking them whether they were interested in a 4,000-ton cruiser, or whether the Arethusa was the minimum acceptable. The ship would replace the ageing ‘C’ and ‘D’ class cruisers. Fleet duties were reconnaissance, flotilla support, day and night screening, and detached operations.75 Replies seem not to have been recorded, but they must have been positive. In August 1934 First Sea Lord (Chatfield) asked for designs for a small cruiser in hopes that something smaller and less expensive than an Arethusa could be produced, and also to counter the large leaders being built by the United States and Japan (the latter were the Fubukis, which the Japanese considered their new standard destroyers).
DNC produced Scout Cruiser sketch designs designated P through U, the tonnage limit having been relaxed to 4,500–5,000 tons.76 As in the 1930 cruiser designs, DNC tried to cut tonnage by reverting to single 6in guns. Design P had six such guns plus the now-standard four 4in HA guns with Southampton-class protection. Speed was 30kts, but to increase that to a more desirable 33kts (Q), displacement was increased to 5,000 tons and one gun mount given up. To get 33kts on 4,500 tons (R), protection had to be cut drastically.77 Alternatively, the level of protection could be maintained and the gun battery halved (Design S). Design T had two triple turrets and full protection (5,600 tons). Instead of scaling down from a cruiser, the ship could be scaled up from a destroyer leader. On this basis a 3,500-ton ship (Design U) could mount five single 6in guns and achieve 38kts, albeit with no magazine protection and limited machinery protection (1in side, ⅜in deck). She was the largest unprotected ship considered, the smallest of high speed which could mount 6in guns satisfactorily, and she offered good sea-keeping. Although she was largely unarmoured, her size in itself offered some protection. She seemed expensive for production in numbers, but destroyers or conventional leaders might not offer enough individual gun power. That led to the next step down, a real destroyer leader, called the ‘V Leader’. She would cost about half as much as Design U. A new twin 4.7in gun offered her considerable firepower. The Naval Staff liked this ship, which did not impinge on available cruiser tonnage, and she became the ‘Tribal’ class. Design discussions of this ship show that she was envisaged very much as a substitute for cruisers in roles such as reconnaissance. The ‘Tribals’, rather than small cruisers, were included in the 1935/6 programme.
Of the cruisers, Design Q was best liked. The design worked only because it employed single open 6in mounts, but ‘a strong body of opinion’ held that turrets offered marked fighting advantages with regard to morale, arcs of fire (which would otherwise be limited by blast), ammunition supply and weather, and that open mounts occupied more space than turrets. Design U was the most powerful against light craft, but could not stand up to destroyer fire, was too expensive and offered too large a target. Against all of these alternatives, C-in-C Mediterranean (Admiral Sir William W Fisher) called for a different kind of ‘small fleet cruiser’ intended specifically to strengthen fleet anti-aircraft defences; such a ship would be of great value for other cruiser duties. To gain anti-aircraft firepower he would accept much lower speed.78 Much this idea had been raised and rejected in about 1925, the counter-argument being that it would be better to provide all ships in the fleet with better anti-aircraft armament. In 1934 Tactical Duties argued that the ship would be too specialised and too vulnerable to conventional cruisers. Moreover, measures were being taken to strengthen fleet anti-aircraft armament.
HMS Euryalus is shown in much her original configuration, probably in the Suez Canal in 1943. She did not yet have a surface-search radar, and she had a Type 285 on only her after HA director. That suggests a relatively low emphasis on anti-aircraft fire: these ships were by no means anti-aircraft cruisers (she did have a surface fire-control set, Type 284, on her LA director). She was also unusual in retaining the HF/DF coil on her mainmast. Her two quadruple 0.5in machine guns were removed about September 1941, not long after she was completed, and five single Oerlikons mounted; another two were added by September 1942, and two singles were exchanged for five twin Oerlikons by mid-1943. At that time, too, her Type 279 radar (visible here) was replaced by Type 281, and she received a Type 272 surface-search set in a small ‘lantern’ on her foremast. She also received Type 282 radar for her pompom directors.
Argonaut as fitted on completion, September 1942. In the elevation drawings, the yards are shown in direct profile. Six aerial wires ran from the upper yard to the after yard. The circular objects with a smaller internal circle in a rack parallel to the depth charge rack, at the fore end of the forecastle, and on the platform with the after pair of 20mm guns, are smoke floats. The main deck and forecastle deck abaft the breakwater were planked with ‘Borneo White’ hardwood; the other decks were covered with a ‘latex’ compound. Asdic was fitted, and six paravanes were carried for protection against mines. On return to the UK in June 1944 after battle damage repairs at Philadelphia Navy Yard (begun March 1943), ‘Q’ turret was replaced by a quadruple pompom and the close-range armament was further augmented by five twin power Oerlikons and four single Oerlikons. The depth-charge rack was removed. (A D Baker III)
A sketch of the small fleet cruiser (3,500 tons) showed her forward guns in ‘A’ and ‘B’ positions, two guns aft in ‘X’ and ‘Y’, the fifth gun on the superstructure deck aft, forward of ‘X’ gun, and four sets of torpedo tubes. The sketch of the ‘V Leader’, however, showed a new kind of arrangement, three of her five twin 4.7in guns being arranged to superfire forward of the bridge, the third mount above ‘B’ mount, to achieve the sort of concentrated ahead fire which was wanted. The 4.7in guns, moreover, were considered a contribution to fleet anti-aircraft protection, despite their limited elevation (40°). They could open fire on a relatively distant enemy formation flying at medium altitude, hopefully breaking it up and making conventional bombing difficult. C-in-C Home Fleet approved the ‘V Leader’ idea, but wanted more close-range armament, while C-in-C Mediterranean thought the ‘V Leader’ was a bad destroyer and an even worse cruiser. He wanted a fast-firing dualpurpose gun with a calibre of about 4.7in, or the usual combination of a main armament of fast-firing guns (4.7in to 5.5in) and 4in antiaircraft guns; cruisers would usually fire rapid bursts of short-range fire, for which 6in guns were not suitable. In a Japanese war, the main threats to a British fleet would be air and submarine attacks, plus a lesser threat from destroyers at night. To deal with such threats he liked the Design U cruiser, but wanted better protection to her vitals, perhaps at a cost in speed. Although battle fleet anti-aircraft weapons were being improved, any new cruiser should contribute to overall fleet anti-aircraft defence.79
HMS Argonaut.
Rear Admiral, Destroyers (RA(D)), the Mediterranean destroyer commander (Rear Admiral Andrew B Cunningham) considered it unwise to concentrate on large cruisers (i.e. Southamptons) because smaller ones were likely to be far more effective in support of destroyers, given their higher rates of fire. It was argued that aircraft could take over the reconnaissance and shadowing roles, but Cunningham noted that there were still too many occasions when weather would not allow a C-in-C to rely fully on aircraft. RA(D) also needed a new flagship to replace the small old cruiser he currently used.80 Small cruisers were needed in general because the ‘C’ and ‘D’ class cruisers were approaching retirement age, and while the ‘E’ class and the new Southamptons were fast enough to work with destroyers, they were too big. RA(D) wanted something no larger than the ‘C’ class cruiser he had formerly used, but extra requirements might boost that to 4,500 tons.
RA(D)’s flagship was the rallying point for a torpedo attack. It required firepower mainly to enable him to exercise command and leadership freely, providing moral support and clearing up obscure or difficult situations personally. The ship therefore needed a reasonable ability to press forward despite enemy destroyer gunfire, i.e. the minimum required to menace destroyers (and protection against destroyer fire). It had to be about as fast as the new destroyers (the ‘Cs’ and ‘Ds’ certainly were not), with sufficient command spaces (including plotting spaces), with maximum handiness, and with a small silhouette, as they would probably lead night attacks. In 1935 it appeared that such fleet operations would be common in a Japanese war but not in any other, so the ship had to be adaptable to other roles. Independent missions, such as those of the old Harwich Force, would probably be the rule in anything but a Japanese war.
Late in January 1935 Director of Plans rejected D of TD’s idea that the 1,830-ton destroyer (which became the ‘Tribal’) would suffice, because the RA(D) ship had to accommodate a rear admiral, seven officers and two warrant officers in addition to the usual ship’s company. First Sea Lord sought to separate the small cruiser and large destroyer issues, approving the ‘V Leader’ but leaving the cruiser issue open. He suspected that C-in-C Mediterranean and RA(D) rejected the ‘V Leader’ only because they feared that approving it would let the Board out of building any small cruisers at all. Director of Plans suggested that the single remaining 1936 ship (as the programme was then understood) be the RA(D) flagship, because only one such ship was needed.
When the Dido class was being built, twin 5.25in dual-purpose guns and mounts were in short supply. HMS Phoebe was completed with a 4in QF starshell gun in ‘Q’ position (Dido was similar); Bonaventure had her 4in gun in ‘X’ position. Note the quadruple 0.5in machine gun on shelter deck level below the bridge, as in earlier cruisers. This photograph was censored to eliminate radars, but the antenna on the mainmast was missed.
Given the shortage of 5.25in gun mounts, two ships were completed instead with 4.5in anti-aircraft guns: they were the only Didos which could be characterised as true anti-aircraft cruisers. Scylla is shown in June 1942. Her sister Charybdis lacked the pair of Oerlikons forward of the bridge.
Director of Tactical Division laid out tentative Staff Requirements in a memo dated 11 April 1935. He suggested two alternative designs, one (A) with six guns, a second (B) with twin mounts of smaller calibre. Design A would be based on the Q design, but with five rather than six 6in single mounts, protection to be reduced to hold displacement within 4,500 tons, but as close as possible to that of Design Q. The ship would have maximum anti-aircraft armament consistent with these conditions. It was not certain that Design B would be steady enough to handle the large fixed ammunition of the 4.5in gun (55lb projectile) then planned as the dual-purpose secondary armament of the new battleships so, since HA fire was important, the choice might lie between the new 4.7in gun (62lb projectile) and the new 5.1in (80lb projectile), the latter ‘showing promise in loading trials’.81 As neither the new 4.7in nor the new 5.1in would be developed for a time, the initial B design should employ the twin 4.7in gun planned for the ‘V Leader’, plus two quadruple pompoms. Design B should be protected against the new 4.7in shell at 5,000yds. The flagship’s contribution to flotilla torpedo fire would be so small that torpedoes were not necessary.82
The ship required good plotting arrangements, so that RA(D) could disentangle a complicated night battle situation, ‘more room being required in the plotting house than normally fitted in a cruiser’ and good communications facilities were essential. Wireless would be as in Arethusa plus a set for use in the Attacking Force frequency. Ships would make 33kts. For each design, DNC should show the effect of fitting the new type of subdivided cruiser powerplant, and also the effect on displacement and protection of reducing speed to 31.5kts. ACNS approved the Staff Requirement on 16 May.
HMS Argonaut is shown after her major refit at Philadelphia Navy Yard, March 1943 – November 1944, after she had been torpedoed on 14 February 1943 in the Western Mediterranean. The big refit, which eliminated ‘Q’ turret, was roughly analogous to contemporary attempts to gain topweight in larger cruisers by landing ‘X’ turret. A quadruple pompom and its director replaced ‘Q’ turret, four single Oerlikons were landed, and five twin Oerlikons installed. The ship’s radars were modernised: adoption of the single-antenna Type 281B cleared the foremast for installation of a Type 293 target-indication set, and she was given a Type 277 surface-search set (its dish is horizontal in this picture). When the ship returned to the United Kingdom, another six single Oerlikons were mounted. By August 1945 the ship had been refitted to better enable her to beat off Kamikazes: she had been given five Boffins (power Bofors on twin power Oerlikon mountings, hence replacing twin Oerlikons) and two single hand-worked Bofors Mk III. In October 1945 she had three quadruple pompoms (the two original mounts plus the one which replaced ‘Q’ turret), five Boffins, four single Bofors, and four single Oerlikons. Cleopatra, Euryalus and Phoebe had all been reduced to four twin 5.25in guns, but Dido and Sirius retained all five mounts. Euryalus was rebuilt on the Clyde, 20 October 1942 – 19 July 1944, emerging with six twin power Oerlikons and five singles, plus her pompoms. Phoebe was rebuilt at New York Navy Yard, 15 January – 14 June 1943, having been torpedoed off Pointe Noire on 23 October 1942. She was given three quadruple Bofors. At the end of the war she also had six power twin Oerlikons and four singles. She had already been torpedoed on 27 August 1941 and repaired at New York Navy Yard between 21 November 1941 and 21 April 1942; at this time her 4in star shell gun was replaced by ‘Q’ twin 5.25in turret.
Submitting sketch designs in September, DNC pointed out that B had a heavier armament and slightly heavier protection, hence displaced 200 tons more. He tried the requested variations in the 6in ship; their effects on Design B would be similar.83 Controller saw no point in spending 4,700 tons to mount five twin 4.7in on a cruiser hull, when a ‘V Leader’ offered the same battery on 1,830 tons. He was far more interested in five twin 5.1in guns, with their much more powerful shells. Their 80lb shells represented the upper limit for man-handling in a lively ship. This weapon would not be available for a 1936 ship, but it was worth asking whether the delay in building such a ship would be worthwhile. The 5.1in gun morphed into a 5.25in dual-purpose gun. ACNS agreed with Controller that the 5.25in dual-purpose armament was best, because it covered both HA and LA requirements.84 In November 1935 the Sea Lords decided to defer construction until the gun was ready.
About January 1936 it was decided that the RA(D) flagship should become the basis of a more general-purpose small fleet cruiser. Although the first of class, RA(D)’s flagship, need have no torpedo tubes, follow-on general-purpose light cruisers should have adequate torpedo armament, which might mean two quadruple tubes. ACNS rejected Staff arguments demanding an aircraft, because that would make the ship too large. By February 1936 plans called for three such cruisers.85
DNC produced two alternative designs, each with five twin 5.25in, with the old and new machinery arrangements; in February 1936 ACNS preferred the new subdivided machinery spaces.86 At a meeting on 8 April 1936 First Sea Lord, Controller and ACNS decided to proceed with the ship, which was expected to displace 5,100 tons, be armed with five twin 5.25in guns and cost about £1.3 million. Of the guns, the second and third pairs would not normally be used for HA fire due to the blast of the foremost pair of guns, which at this point were envisaged as open upper-deck mountings. Machinery spaces would alternate, and speed was held at the 32kts of the earlier design studies. Magazines were given 3in crowns and sides, and the machinery a 3in belt and 1in deck. A BD version of the twin 5.25in was in development which was preferable to the open upper-deck mounting because mountings would not suffer from the blast of adjacent guns. On 8 May Controller noted that the design of the BD mounting was much more advanced than had been imagined; as long as ships were not laid down before February 1937 they could be armed with it. On 13 May First Sea Lord (Chatfield) chose the alternating-machinery option.
It was immediately obvious that the ships would be badly cramped, but there was apparently no interest in making them much larger. For example, to hold down displacement when the BD mountings were adopted, ammunition per gun was cut from 300 rounds to 250. ACNS later pointed out that the ships would have an unusually high proportion of HE shell, due to their dual-purpose role, and that would make them more vulnerable than usual to explosions near their shell rooms. He therefore wanted the heavier magazine (cordite) protection extended to the shell rooms, at a cost of about 35 tons. The design was so tight that Controller rejected even this addition, the improvement to be explored after tenders had been invited. Protection as described in the final Legend for Board approval was somewhat lighter than in the earlier design studies.87 This was the Dido class. The Legend and drawings received the Board Stamp on 14 December 1936. Five were ultimately included in the 1936/7 programme alongside the two Belfasts.
In February 1937 heavier long-trunk 5.25in mountings were adopted.88 The magazines could be pushed under water, where they would not need side protection (but would retain their ends, since shells could pass through the structure of the ship). The ammunition lobbies of earlier designs were eliminated. That made it possible to bring the mounts closer together, so ‘Q’ mounting was 6ft further from the bridge (and less likely to cause blast problems at high angles) and the quarterdeck became 22ft longer. Fewer men were needed to serve the guns (complement was cut from 558 to about 485), so some of the congestion was relieved (similar long trunks were adopted in larger cruisers for similar reasons). Now 360 rounds per gun could be stowed for the forward mountings, 320 rounds for ‘X’ mount, and 300 rounds for ‘Y’. Magazine crowns were reduced to 2in, but the same armour could cover the shell rooms (the ammunition spaces were larger than before). Displacement increased to 5,450 tons. Boilers were re-rated to 62,000shp under temperate conditions (which bought a quarter-knot) by increasing their forcing rate (output in the tropics continued to be 58,000shp; much the same re-rating was being done in the contemporary Fiji class). That added 20 tons, which DNC considered acceptable, but at the very limit the ship could accept. At the same time tripod masts were substituted for poles. A memo indicated that beam had to be increased half a foot, but the ships ended up with the same 50ft 6in beam chosen earlier. Not surprisingly, estimated cost rose throughout the design process.89
The ships had an unavoidably high silhouette due to the three superimposed 5.25in guns forward. Attempts to cut it down, both by sinking the turrets into the deck, and by eliminating the wheelhouse under the bridge, failed.90 The bridge had to be high enough to provide clear vision over the upper guns.
Given their ancestry, these were hardly single-purpose anti-aircraft cruisers. Low-angle fire was far too important in their conception. The 5.25in calibre was chosen not because it made for good anti-aircraft fire, but because it was good for stopping destroyers and lightly-armoured cruisers. The Royal Navy considered the 4.5in gun, with its lighter and handier shell, a more ideal heavy anti-aircraft weapon – which is why it armed British aircraft carriers. The ships had a LA DCT atop the bridge, with a HADT abaft and above it, and a dual-purpose (H/LA) DCT aft.91 There was a single combined transmitting station (for surface fire) and HA control position (HA computer room) below decks, containing an Admiralty Fire Control Table Mk VI* and a High-Angle Calculating Table Mk IV*. At the outset, DNO pointed out that without dedicated anti-aircraft guns, the ships had no way to fire star shell (the principal means of night illumination) other than their main batteries. The Royal Navy was increasingly interested in night combat, so DNO proposed a separate 4in star shell gun, which would not be an anti-aircraft weapon (development of a separate star shell thrower was considered and rejected). The idea died because too much – perhaps both pompoms – would have been sacrificed. The design allowed for two of the new quadruple 0.661in machine guns in place of the usual quadruple 0.5in guns, but the new weapons never entered service.
Three repeat Didos were included in the 1937/8 programme, and two more repeat ships in the 1938/9 programme. No Didos were included in the regular 1939/40 programme. However, by mid-1939 the projected Emergency War Plan included four ships. At this time (see below) the ‘D’ class cruisers were to be rearmed with standard twin 4.5in mounts, but this rearmament was to be cancelled in the event war broke out before it could begin (as was the case). The projected emergency programme was set partly by the expected production of twin 5.25in guns. DNC pointed out that if two cruisers could be armed instead with 4.5in mounts freed by cancellation of the ‘D’ class reconstruction, it might be possible to build five rather than four emergency Didos. That was done: in September 1939 Charybdis and Scylla were ordered armed with four twin 4.5in mountings each.92 They were fitted as RA(D) flagships.
Scylla as fitted on completion, June 1942. Although the plan view shows provision for a 4in gun to fire star shell mounted between the aftermost pair of single Oerlikons, no such gun was ever fitted, and the surrounding splinter shielding and ready-service ammunition lockers seem to have been removed before commissioning. Shortly after completion, two more Carley floats were added to each side beneath the forward pair of 44in searchlights. In 1944 the single Oerlikon mountings were replaced by three twin power mountings. Note that the 20mm mounts did not have on-mount shields for the gunners as of June 1942. (A D Baker III)
Cleopatra (shown on 3 April 1945) was modified similar to Argonaut, but had US-type quadruple Bofors instead of pompoms. She was modified at Philadelphia Navy Yard, 24 November 1943 – November 1944, having been torpedoed off Sicily on 16 July 1943, and having been given temporary repairs at Malta. In her case other close-range armament comprised, by the end of the war, six twin power Oerlikons and four singles.
Dido, Bonaventure and Phoebe were each completed with four rather than five twin 5.25in guns, with a single 4in LA gun in ‘C’ position. Only Dido eventually had her proper ‘C’ mount fitted. Like their contemporaries the Fijis, these ships came out badly overweight. Designed for 5,450 tons, Naiad was completed at 5,677 tons. The 220 tons of approved additions included extra light armament, heavier main machinery, electrical increases, and larger complement. By the end of 1941 another 72 tons had been added without compensation: radar, RPC for pompoms, internal degaussing, SA gear, Asdic, etc. Another 92 tons of proposed additions, including a UP (‘Unrotated Projectile’ – anti-aircraft rockets) mounting, had been rejected or, in some cases, compensated for.
The original close-range battery was the standard two quadruple pompoms and two quadruple 0.5in, but by January 1942 all 0.5in guns had been removed from Dido, Hermione, Naiad and Euryalus and replaced by five Oerlikons. Cleopatra had three Oerlikons. Argonaut was completed with two single power-driven 2pdr Mk VII and four single Oerlikons (Oerlikons temporarily replaced the single 2pdrs). By 1944 her ‘C’ mount had been replaced by a third quadruple pompom, and in addition she had six twin power and five single Oerlikons. Sirius was similarly armed, but by 1944 had seven Oerlikons. In July 1942 Cleopatra had two single 2pdr Mk VII, three single Oerlikons and two quadruple 0.5in machine guns, the latter to be replaced by Oerlikons or by 2pdr Mk XVI. With less topweight, in January 1942 Phoebe had eleven Oerlikons. When she was refitted in the United States, the 4in gun was replaced by a US-type quad Bofors, two replacing her pompoms, plus six twin power and four single Oerlikons. Cleopatra was similarly rearmed. Euryalus had ‘C’ mounting replaced by a third quadruple pompom, and by 1944 she had six twin power and four single Oerlikons. The Emergency War Programme ships completed to a modified design as the Black Prince class are described in a later chapter.
Vickers-Armstrong’s light cruiser for Portugal (June 1930, Design 1005) would have been armed with six 6in guns, four 4in HA, one machine gun, four triple torpedo tubes and two depth-charge throwers. The latter appeared on nearly all Vickers cruiser designs of the inter-war period. This ship would have displaced 5,000 tons (450ft pp, 476ft loa x 46ft 6in x 27ft x 14ft 6in). Power would have been 40,000shp (29kts), and endurance would have been 5,000nm at 12kts. This design seems to have been offered to Romania in August 1930. The Portuguese Navy suffered from ambitious but grossly-underfunded plans, and Vickers offered designs to match. The Navy Law of 1907-8 called for six 5,000-ton protected cruisers (which come before the period covered by this book). The monarchy was dissolved in 1910, and a new 1912 Navy Law called for three battleships and three 2,500-ton scout cruisers, among other ships. There was insufficient money, so in 1913 new plans called for a smaller programme including two small cruisers (2,500 tons, 20kts, two 6in and six 4in guns). The cruiser contract was provisionally awarded to a British consortium (John Brown, Cammell Laird, Fairfield, Palmer’s, Thornycroft), but there was no money. No new programme was announced until 1930, and it included no cruisers. However, it is clear from Vickers’ record that numerous designs were offered. The Vickers version of the slow protected cruiser was Design 614 (20kts, 305ft x 37ft 6½in x 22ft 6in) of 7 January 1913. During the First World War, when Portugal was a British ally, Vickers offered an enlarged Cassandra design (Design 817A of 22 August 1916, described as having 12 per cent more power: 450ft pp, 480ft oa x 44ft x 25ft x 14ft 9in, 4,820 tons, armed with six 6in/50, two 3in, two 3in HA and two twin 21in torpedo tubes). Slightly later it offered slightly larger Designs 750 and 751 (460ft x 44in x 25ft 4in x 14ft 6in, 4,930 tons) with the same armament. There was also a related ‘fast cruiser’ (Design 819 of 18 September 1916). These seem to have been the last export cruiser designs Vickers offered before the First World War ended. Note that Vickers’ design numbers were apparently anything but consecutive. The Cassandra design itself was later offered to Uruguay (about 1921) and to Romania (as Design 805). Vickers continued to offer the country warship designs, including several aircraft carriers. Portuguese desires (and, presumably, resources) waxed and waned. In November 1921 Vickers offered a 2,000-ton, 310ft scout cruiser (Design 933) armed with four 6in guns in single upper deck mounts, two 3in HA and two twin 21in torpedo tubes. The Vickers design book gives no other dimensions, so these data may indicate what the Portuguese wanted rather than what Vickers could provide in a realistic design. Vickers later offered a 3,300-ton (normal displacement), 400ft cruiser armed with six 6in guns, two 3in HA and two triple torpedo tubes, which may have been an outgrowth of this project. In August 1925 Vickers offered Portugal Designs 1010 and 1013, which had previously (1923) been developed for Brazil (7,000 tons, seven 6in guns, and 6,000 tons, six 6in guns). At the same time Portugal was offered Design 1187, in which the eight 6in guns were all in twin mounts. There were also four 4in HA and four triple 21in torpedo tubes. The design showed a 3in belt over its machinery. It was described as similar to the Spanish F design (Principe Alfonso), but lengthened by 10ft, displacing 8,000 tons (555ft pp, 585ft loa x 54ft 6in x 30ft 6in x 16ft 6in). Estimated power was 80,000shp for 33kts. There was no conning tower. The Design F powerplant (82,000shp) would drive the ship at 33kts. In effect this was much the design to which two of the Spanish ships were later rebuilt. By February 1926 Portugal was clearly shopping for something more impressive. Vickers offered Design 1228, 8,250 tons (555ft pp, 585ft lwl, 589ft loa x 56ft x 37ft 6in x 16ft 6in), designed for 33kts on 80,000shp and for a radius of action of 5,000nm at 15kts. Armament was three twin 8in/50, four single 4in HA and two triple torpedo tubes. Configuration was very unusual, all three turrets being forward, arranged as in the later USS Brooklyn, leaving the after part of the ship open. All armament was on the forecastle, the triple torpedo tubes being forward of the antiaircraft guns. Vickers records also show an un-numbered design for Portugal dated 12 July 1926, for a 5,000-ton cruiser (450ft x 46ft 6in x 27ft x 14ft 6in) armed with six 6in/50, four 4in AA and four triple torpedo tubes. She would have made 29kts on 40,000shp, and she had wartime-type side protection. No drawing has survived, but she seems to have been a precursor to Design 1005. The Portuguese soon abandoned these projects, and in 1927 they asked for a gunboat, although they called it a cruiser: Vickers offered Design 918 (3 March 1927), displacing 2,500 tons on trial (330ft x 39ft 6in x 28ft 9in x 13ft trial) powered by 3,000ihp reciprocating engines (17kts). Armament would have been two 6in, two 4in HA and four pompoms. This ship might be considered the ancestor of the big gunboats Portugal ordered a few years later. In 1930 the country moved back to something more impressive, in the form of Design 1005. Somewhat later Vickers offered Design 1070. (National Maritime Museum)
Vickers’ Design 1070 for Portugal was armed with six 6in/50 in two twin mounts superfiring over two singles. It is undated, but it is included in a list of designs of the early 1930s. Note the resemblance to contemporary British destroyers. (National Maritime Museum)
Design 1071 was the larger alternative to Design 1070. It would have displaced 4,550 tons rather than 3,350 tons, and would have been 450ft rather than 400ft long. Note the gun arrangement, in which one twin mount is forward and two are aft. (National Maritime Museum)
Design 1002 was a light cruiser for the Royal Netherlands Navy. It appears to have been Vickers-Armstrong’s bid for what became the cruiser De Ruyter, as a paper in the file, dated October 1932, is a sketch of the latter (which was now to be built) forwarded by Vickers’ Dutch agent. Vickers notes on Design 1002 were dated 1 May 1930. The Vickers plans archive at the National Maritime Museum includes Design 1002A, which has just the sort of tower bridge/foremast the Dutch adopted; perhaps it was what the Dutch built. There were, after all, few firms capable of producing such a design at the time. Armament was three twin 15cm (one forward, two superfiring aft), four 10.5cm anti-aircraft guns, four 40mm AA and two depth-charge throwers. Unusually, there were no torpedo tubes. The ship would have displaced 6,300 tons normal and 6,900 tons fully loaded (500ft pp, 530ft lwl, 534ft loa x 50ft 5in ext x 35ft 6in to forecastle deck, 28ft to upper deck x 15ft 6in). She was expected to make 32kts on 60,000shp (six Yarrow water-tube boilers), with a radius of action of 5,000nm at 12kts. Total complement was 450. She would have had one catapult and two seaplanes; the Royal Netherlands Navy placed considerable stock on the use of such aircraft in the East Indies, and even carried them on board its destroyers. From the Dutch point of view, this project was an attempt to revive an expansion programme rejected by the Dutch parliament in the early 1920s. In September 1920 Vickers offered the Dutch its Design 767: five twin 6in/50, two 4in HA and four triple tubes on 5,150 tons (455ft x 47ft 6in x 27ft x 14ft 6in, 29kts on 40,000shp [all-oil]). Protection followed wartime British practice (side but not deck). The ship’s power and armament suggest that she was an enlarged version of the Vickers-built Cassandra with twin 6in guns replacing the single mounts on board that ship. The design developed for the Netherlands was later offered to Romania (as Design 808) and to Turkey (in May 1923, as Design 836X). Design 834X (sent to Turkey 5 October 1923) was larger than the earlier Dutch design but had the same five twin 6in/50 (plus four 105mm/50 HA, two 3pdr QF, two single pompoms and four triple torpedo tubes) on 7,000 tons (520ft x 53ft x 30ft 3in x 16ft, 31kts on 60,000shp using six Yarrow oil-fired boilers). Protection followed British wartime practice (side but not deck). Vickers continued to court Portugal, Romania, and Turkey between wars. Despite evident interest in cruisers, the first post-First World War Romanian naval programme (1927) amounted to four destroyers (two of which were bought). The next programme (1937) called for a cruiser and lesser warships. Unfortunately Vickers’ design files for this period are too incomplete to show whether the company offered anything to Romania at that time. Before that, other designs offered to Romania included Design 1290 of February 1927, with eight 6in/50 in three twin and two single (‘A’ and ‘Y’) mountings; two 3in HA, four twin torpedo tubes and two depth-charge throwers. The arrangement was as in the Spanish Principe Alfonso, with the amidships twin mount between the two funnels and the after controls. The bridge resembled that of the British ‘County’ class with its tower surmounted by a director. A second director was abaft the pole mainmast. Displacement was 6,100 tons (normal), 7,105 tons (deep) (500ft pp, 527ft lwl x 50ft 5in x 28ft 6in x 15ft 3in). The ship would have made 33kts on 70,000shp, and endurance would have been 3,500nm at 15kts. Design 927 (18 March 1927) was similar, and the difference in designation may indicate mainly that it was developed by a different designer, possibly George Thurston. The ship would have been faster (34kts, 87,000shp) and slightly smaller (6,000 tons, 500ft x 48ft x 28ft 6in x 15ft 8in). In August 1930 Romania was offered Design 1008, 5,750 tons normal and 6,600 tons fully loaded (480ft pp, 500ft wl x 49ft 7in x 27ft 6in x 15ft), armed with four twin 6in/50, two 105mm/40 HA, two twin 40mm HA, two quadruple torpedo tubes and two depth-charge throwers. She would have made 30kts on 50,000shp, and endurance would have been 7,000nm at 15kts. Complement would have been twenty officers and 480 ratings. Vickers offered a minelaying cruiser to Turkey (see the Appendix). It also offered the Design 881 light cruiser (estimate dated 20 January 1925) displacing 4,100 tons (430ft x 43ft x 24ft 3in x 13ft 9in) armed with six 6in/50, two 105mm HA, two pompoms and two triple torpedo tubes. Machinery would have been similar to that of HMS Curlew (40,000shp, 29kts). It is not clear to what extent this design answered a formal request for proposals connected with a programme; the largest surface ships Turkey actually bought between wars were destroyers. In 1938 the Turkish government sought large cruisers from Germany and from the United Kingdom, but it is not clear whether any designs were prepared (Vickers’ material, which is very incomplete this period, does not mention any). Vickers’ records also show a cruiser offered to Cuba (18 December 1929, not numbered): 4,878 tons (455ft x 46ft x 26ft 1in x 14ft 3in), six 6in, four 3in AA, two triple torpedo tubes and two depth-charge throwers; 40,000shp, 29kts. (National Maritime Museum)
Vickers offered this Design 1054 to Norway in the early 1930s. The ship would have displaced 3,000 tons in trial condition (384ft pp, 407ft lwl x 38ft 6in x 22ft 6in x 12ft 6in). She would have made 30kts on 34,000shp. These data were undated, but the adjacent page (in a Vickers design notebook) of design data for an Estonian coast defence ship is marked ‘to Thornycrofts 13-10-33’. The cruiser was part of a programme which included coast-defence ships (Design 1053, data dated 16 September 1933). Vickers archives also show an un-numbered small cruiser offered to Estonia, probably in the late 1920s, to be based on Design 925 (which, unfortunately, does not appear in surviving Vickers material): 3,250 tons (405ft pp, 429ft loa x 40ft x 12.5ft), 27kts (endurance 4,500nm at 15kts). Armament would have been four 6in, two 4in HA, four single pompoms and two triple torpedo tubes. The comparable Design 887 was a light cruiser for Yugoslavia (offered in conjunction with 888, a flotilla leader): two twin 6in/50, two 4in/45 HA, two single pompoms and two triple torpedo tubes on 3,000 tons (390ft x 37ft 6in mld x 22ft 6in x 12ft 6in, 27kts on 22,500shp with six Yarrow oil-burning boilers). Vickers’ most interesting inter-war small-cruiser design was probably Design 776, for Japan (estimate dated 7 February 1921). The competition involved seems to have been used to obtain British ideas for what became the small Yubari. The central requirement was high speed on a limited displacement, so Design 776 was 4,080 tons (440ft x 44ft 6in x 25ft 6in [hull depth] x 14ft), designed to make 33kts on 59,000shp (six boilers burning only oil, three burning coal and oil). She would have been armed with Japanese weapons: four 14cm/50, one 8cm/40 HA, two single pompoms and four twin 53cm (21in) torpedo tubes. Protection would have followed wartime British practice (2½in side over machinery, 1in to the upper deck, and 1in bulkheads at the ends of the machinery spaces). The smallest alternative in the series was 776C (3,700 tons, 430ft x 43ft x 25ft 6in x 14ft, 31kts on 45,000shp with four alloil and three oil and coal boilers). In May 1921 Vickers sketched an (unnumbered) cruiser armed with only two 6in/50, one 3in HA and four twin torpedo tubes: 4,100 tons (425ft pp x 42ft 3in x 24ft 7in x 14ft), with 40,000shp engines (six Yarrow boilers) for 29kts. The estimate sheet does not explain why the ship was so lightly armed. (National Maritime Museum)
Design 1087 was offered to Siam; it presumably competed unsuccessfully with an Italian design, some time in the late 1930s (the Walrus amphibian also suggests this period). The ship would have displaced about 4,000 tons and would have made 30kts (no horsepower is given in Vickers papers). Note that she would have had fully-enclosed turrets for her six 150mm/50 guns. Other armament was six 75mm/50 HA, four twin 40mm, and two sets of triple 45cm (18in) torpedo tubes. Protection was 70–75mm amidships, 40–50mm fore and aft, and 35–40mm on deck. Dimensions: 450ft pp, 475ft wl, 478ft oa x 47ft 6in x 26ft 3in x 14ft 3in, 4,550 tons standard displacement. This seems to have been one of a series offered to the Siamese government, the others being a nominal 2,000-tonner (350ft pp x 37ft 6in x 21ft x 10ft 9in, 2,320 tons fully loaded) and a 3,000-tonner (3,400 tons: 400ft pp, 420ft wl x 42ft x 12ft 6in). Armstrong having won a Thai contract for the coast-defence ship Ratanakosindra in 1924, Vickers-Armstrong sold another such ship to Siam in 1928, but Kawasaki built the follow-on Sri Ayuthia class in 1937–8. Other Vickers papers identify the 2,000-tonner as Design 1056, armed with two 4.7in guns, two 3in HA, and two 21in torpedo tubes (2,160 tons). No armament details of the 3,000-tonner seem to have survived. Vickers also negotiated with China. A 6,000-ton (500ft x 52ft x 28ft 6in x 14ft 6in) light cruiser (Design 970, 7 September 1929) would have been armed with two twin 8in, four 4in HA, four twin pompoms, and two depth-charge throwers. She would have made 30kts on 46,000shp. The two considerably more modest Japanese-designed Ning Hai class seem to have been bought instead. (National Maritime Museum)
Vickers-Armstrong’s Design 1089 was the late-1930s version of its small cruiser with six 6in guns, two twin and two single. Secondary armament was two twin 40mm (Bofors guns) at the break of the forecastle and four 76mm HA guns abaft the second funnel. Unfortunately Vickers-Armstrong records of designs for foreign customers in this period seem not to have survived. (National Maritime Museum)
Design 1094 was a larger-cruiser counterpart to Design 1089, with three twin 6in mounts and a Walrus aircraft amidships (served by a crane, without a catapult). The Walrus was a Vickers Supermarine product, hence worth advertising as part of the design. It could operate without a catapult because it was designed to survive in ocean swells. Abreast the torpedo tubes are the rangefinder and height-finder (abaft it) for the AA battery, with a larger rangefinder (for the 6in battery) further aft. The 6in in this ship are still in open twin mounts; presumably Vickers also offered larger designs with enclosed mounts. Design 1094 or something similar may have been offered to Chile, which chose an Italian Ansaldo design instead in about 1937. The Chileans then decided to have something larger, touching off a diplomatic crisis as the British tried to ensure that they could not buy a treaty-busting 8in cruiser. When the crisis subsided, it turned out that Chile could not have afforded anything so expensive, and just before the outbreak of war Vickers-Armstrong was offering Design 1111, armed with four twin 5.25in guns. This design had alternating engine and boiler rooms (all four boilers in tandem, with oil fuel outboard). One of several unusual features was that the HA director forward was stacked atop the LA director, with a rangefinder forward of both. The identity of Design 1111 is clear because it figured in 1939 discussions between Vickers-Armstrong and the Admiralty.