WARTIME CRUISER DESIGN
The outbreak of war ended the treaty limits, but the initial war programme, which was actually an extension of the planned 1939/40 programme, included no new designs. Anything new would come in the 1940/1 or later programmes. Throughout early 1942 work proceeded on designs for large heavy cruisers. These have often been attributed to Churchill’s personal interest, expressed once he returned to the Admiralty in September 1939, but from Constructors’ Notebooks it is now clear (see the earlier chapter) that the idea considerably predated his arrival, and that the really large British cruiser designs seem to parallel the US Alaska project. The main cruiser design reflecting Churchill’s personal ideas was an abortive torpedo cruiser (recalling his enthusiasm for a torpedo cruiser in 1913-15), which did not survive his move from the Admiralty to 10 Downing Street in May 1940.1
The ‘Russian’ Cruiser
In 1939 eight sets of cruiser machinery were being built in Britain under Soviet contract, two already being complete. Since machinery was a bottleneck in warship construction, naturally there was interest in incorporating it in new ships, as the Germans had done with Russian cruiser machinery in 1914. They were rated at 48,000shp on two shafts, running at 430rpm (overload rating was 54,000shp with 449rpm). Overall arrangements were similar to those in an ‘L’ class destroyer rather than in a larger cruiser, although the machinery required 16ft more length than in the ‘L’ class; presumably the machinery was intended for Soviet super-destroyers. The proposal was to use them in anti-aircraft cruisers with heavy (3in) armoured decks.2 Such ships were badly needed, so in May 1940 Controller ordered the project to go ahead, even though it had not yet received Board approval. A Legend (Design C) showed a standard displacement of 5,800 tons (470ft [pp] x 54ft x 17ft 3in deep) and a speed of 29/28kts on 48,000shp, which was hardly impressive. Armament was four twin upper-deck 4.5in (as in Scylla and Charybdis), two rocket projectors (UPs), two octuple pompoms and two triple torpedo tubes. Dimensions were determined largely by the need for stability.
Diadem is shown at about the end of the Second World War. The short vertical dipoles at the yardarms forward and on one side of the light yard on the mainmast may be for Type 650/651 missile jammers.
The project to use the Soviet machinery died because the sets did not include boilers, hence using them would not make for quicker construction. Moreover, it was British policy not to antagonise the Soviet Union, so on 22 May 1940 Metropolitan Vickers was told to deliver the machinery. However, Controller continued to be interested in an antiaircraft cruiser using ‘L’ class machinery, and in June 1940 he asked for a design for a fast minelayer using ‘L’ class machinery. The Legend prepared has, however, been lost.
The Large 1941 Cruiser
For the 1940 programme the only large cruiser whose design was ready was Belfast, so the design was revised. Beam at the waterline was increased by 2ft (soon increased again to 2ft 6in), the shape of the upper deck being unchanged. ‘X’ and ‘Y’ turrets would be lowered (‘X’ to the level of ‘A’ turret, and ‘Y’ below that), presumably to make it possible to add new topweight. The machinery had to be moved forward, and propeller shafts lengthened (adding 29 tons). More extensive splinter-proof plating would be provided for the 4in gun crews and other topside personnel.3 The forecastle deck from the catapult back to abaft the 4in guns would be lowered 6in and new (heavier) Mk V HADTs would replace the Mk IVs. Structural design would be improved by making the break from 60lb armour more gradual. Aluminium alloys used in prewar ships were now unavailable, which added weight. Estimated standard displacement with all these changes was 10,866 tons.4
In December 1939 work was also proceeding on a large cruiser armed with three triple 8in guns, descended from the studies begun that June, in an alternative to the repeat Belfast. Because no cruisers were included in the 1940/1 programme, enough time elapsed for this design to become mature enough to be offered in the spring of 1941 for the 1941/2 programme. On 8 January 1940 DNC asked for a three-turret 8in ship based on the earlier 21,500-ton design, although he hoped to reduce tonnage to about 15,000 tons by cutting protection to that effective against 6in fire, on the grounds that it would resist 8in fire at the large inclination angles at which cruisers normally fought. Thus it would have a 6in belt covered by a 2½in deck (3in over magazines), and the turrets would have 6in face, 3in roof and 2in sides. DNC hoped the machinery could be more extensively subdivided than in earlier ships.5 The ship should also have six twin 4in and two octuple pompoms (as in Belfast), as well as a fixed catapult and two aircraft. No torpedo tubes were specified, but provision should be made for them. Speed should be 33kts standard, 31.5kts deeply loaded. Boilers should all be below the lower deck, where they would be fully protected. The ship’s GM should be 4 to 6ft. An alternative ship, which DNC hoped might displace about 10,000 tons, would differ in having four twin 4in guns, a 5in belt, and a speed of 32.5kts at standard displacement and 31kts deeply loaded. GM would be 3 to 6ft.
The 15,500-ton (670ft x 77ft x 20ft mean) heavy cruiser as sketched 20 January 1940; a 12,500-ton version was broadly similar. Armament was three triple 8in, six twin 4in HA and four octuple pompoms. Note the two HA directors sided aft, just forward of the after 8in director. There were no torpedo tubes, although later versions of the heavy cruiser had them. Machinery spaces would have been covered by a 2¾in deck, increased to 3in over the magazines and the 4in HA magazine and then the control space forward of the forward boiler room. (Norman Friedman)
To keep boilers below the lower deck (for better protection), lower output per boiler had to be accepted. For the kind of power needed (96,000shp or 112,000shp or more) a ship needed more boilers, so W G John sketched eight-boiler arrangements based on the four-boiler layout in existing cruisers, ultimately with boilers paired side by side, their uptakes trunked together to form a funnel from each machinery unit. It might be possible truly to isolate the two machinery units by inserting an air space between them (i.e. abaft the forward engine room and thus forward of the after boiler rooms). Beam was so great that there was no point in putting the after boilers in tandem. E-in-C offered up to 25,000shp per boiler (John thought they could be pushed higher), but the individual boilers would be too tall, so the eight-boiler plant (14,000shp boilers) was preferable.
Visiting the designers at Bath on 8 January 1940, DNC clearly wanted the 8in ships to be built. DNO was to be asked when triple 8in mounts would be ready for the ship. If that was (as apparently expected) June 1944, the ships would be laid down in June 1941, under the 1941/2 programme. The desired pair of Legends were dated 22 January 1940. The 15,000-tonner (670ft x 77ft 6in x 20ft, with 18ft 6in freeboard) required 125,000shp and was credited with 9,000nm endurance at 16kts. The 10,000-tonner (610ft x 72ft x 18in 6in with 17ft freeboard) required 96,000shp and was expected to have the same endurance. These sketches became the basis for further design development. DNC had earlier asked whether the 10,000-tonner would actually displace about 12,000 tons. He could hold down standard displacement by limiting standard ammunition stowage to 100 rounds per gun, providing space for 150. Tonnage was also being held down by adopting a higher forcing rate. The result was a paper speed equal to that of the Germans, ‘but experience shows that they don’t over-state their speed so that actually would be slower than the Germans’.6
Early in August 1940 DNC became interested in the better-protected nine-gun 6in cruiser he preferred to a modified Fiji, with Fiji side armour but the upper deck increased to 2in – 1½in armour throughout, worked structurally, rather than upper deck armour over only the boilers and the engine room between them. If possible another inch would be added to the deck, and ¼in to splinter protection. Fiji machinery would be used and the ship would be armed with four twin 4in and four (rather than two) quadruple pompoms. After an initial design was completed DNC ordered it modified with a 3in upper deck over boiler and engine rooms, the 6in turrets to have Belfast protection (by making barbettes 120/60lb instead of 80/40lb), and HA armament increased to six twin 4in and four quadruple pompoms. Splinter protection would be increased. DNC also wanted a twelve-gun version prepared.7 The nine-gun ship was expected to displace 10,790 tons, although another estimate gave 11,016 tons for an updated Belfast with nine guns. Additions included the more powerful D.IV.H catapult of a Fiji (30 tons), additional splinter protection (65 tons), weight due to the non-availability of light alloys (100 tons), radar (15 tons), UP (rocket) mountings (15 tons), new Mk 4 HADTs (6 tons), and modified machinery (30 tons). Beam would have been increased by 2ft 6in to maintain stability despite considerably more topweight. A nine-gun updated Belfast, again with increased beam, would displace about 10,510 tons. A Legend was prepared for a nine-gun ship with Fiji side armour (3¼in and 3½in) but with 3in decks and Fiji machinery (10,500 tons). E-in-C disliked forcing boilers to the extent resorted to in the Fiji class, so an 80,000shp plant in any new ship needed larger, heavier boilers, as in Belfast. The desired ship had Belfast machinery and side armour (4½in). At the beginning of September 1940 DNC was instructed to proceed with the nine-gun improved Belfast with increased protection, and to work out the tonnage of a comparable ship armed with twelve 6in guns. Legends were prepared in October 1940: the nine-gun ship would displace 11,450 tons, the twelve-gun ship 12,980 tons.8
Once estimates had been completed, the two 8in designs were updated to reflect war experience. E-in-C no longer wanted to accept the rate of forcing which had provided the Fijis with their nominal 80,000shp, so machinery would have to be heavier. More electric power was needed, and requirements for reserve power were becoming more stringent. Fire control, including radar, was becoming more and more complex, demanding more power rooms and more men. Late in 1940 DNO wanted RPC for 4in and pompom mountings, which added more weight and internal space. The structural problems revealed by the Fijis demanded more armour in way of previously abrupt changes in thickness and more splinter protection was wanted. On this basis the nine-gun ship was expected to displace 11,945 tons rather than the 10,500 tons estimated in October 1939, and to make 30.75kts rather than 32kts in standard condition. The eight-gun version displaced 12,500 tons.9
Attention then shifted back to 6in cruisers, estimates being ordered for nine-gun Fijis with more deck armour: either (a) 3in over magazines and 2in over machinery or (b) 3in over magazines and 60lbs with 2in armour on top, on the upper deck. On 16 October DNC asked for quick studies of ‘Mr. Lillicrap’s proposal’, i.e. twelve 6in, Fiji speed, 2in rather than 3in over magazines and 1in bulkheads, and a ship with Fiji speed (or less, if that could not be achieved on four boilers) with Belfast protection (4½in side, 2in deck over magazines, 1in over DCT, bridges, and wiring, and 1in bulkheads to machinery spaces). DNC became unhappy with even the deck protection he advocated, which would suffice against a 500lb bomb dropped from 5,000ft. A re-estimate showed that a dive-bombing drop from 3,000ft at 300 mph would be nearly equivalent to a level-bombing drop from 11,000ft, against which the ship should have 3½–4in deck armour.
Four quick studies were produced: a modified Fiji with twelve guns (Design X); Design X with nine guns; a twelve-gun ship with Belfast protection (Design Y); and a nine-gun version of Y As might be imagined, these were not small ships; Design Y would have displaced 14,050 tons.10 On 16 November Controller asked for a further twelve-gun design (Z) modified from Design Y, with a 4in rather than 4½in belt and 2in deck (3in rather than 4in over magazines), to save, respectively, 110 tons and 230 tons. This ship had a speed of 30.5kts in deep condition. Required machinery and magazine spaces did not allow much reduction in length; the designers cut 10ft (to 625ft) to save 200 tons on the hull (6,400 tons rather than 6,600 tons). Standard displacement would be about 13,500 tons, and the ship would need about 97,000shp rather than 100,000shp. Controller also wanted to know what thickness was needed to resist 112lb 6in shell at 45° inclination at 8,000-9,000yds (the answer was 3½in NC).11 Design Z was carried forward, DNC asking in mid-January for the effect of carrying belt armour up to the upper deck throughout the citadel, rather than stepping it down at the end of the machinery space. That added about 256 tons; the ship would probably need a foot more of beam to maintain stability, and that would add another 20 tons for the extra strip of deck. Probably the ship would grow by 400 tons, counting extra hull weight, to 13,600 tons, and she would lose a quarter-knot, to make 31.75kts standard and 30kts deep.
Controller held a meeting on future cruiser designs on 5 December 1940. Opinion favoured the 6in cruiser, largely for fear that a post-war naval limitation conference would find the British with four 8in cruisers under construction and the prospect of a new naval building race – i.e. with the problem the Hawkins class had posed in 1922. Any hope to kill off the 8in gun cruiser depended on an agreement with the United States. Unfortunately the US Naval Attaché said unofficially that the US programme included fourteen heavy cruisers (four of them with 12in guns [the Alaska class] and ten with nine 8in each) plus thirty-four cruisers armed with 5in or 6in guns. Corrected figures supplied in January 1941 showed six super-cruisers and eight 8in ships. A few days later Controller decided that the Staff must take cruiser design up again with VCNS, his view being that the Royal Navy could not go beyond 10,000 tons and twelve 6in.
In 1952, in New Zealand service, Bellona had no single Oerlikons, but she had six single Bofors guns. Her sister Black Prince had four single Bofors, four Boffins (power-driven single Bofors on twin Oerlikon mountings), and only three single Oerlikons. Radar modernisation of Bellona was limited to replacement of the old Type 272 by a Type 277 dish.
Photographed post-war in Melbourne, HMNZS Black Prince shows her heavy post-war 40mm battery. Her radar suit had been modernised to the point of converting her Type 281 air-search set to use a single antenna, and replacing her Type 272 with a Type 277 dish (here horizontal, hence not very evident). (Photo by Allan C Green via State Library of Victoria)
In mid-January 1941 First Sea Lord asked the two main fleet commanders (Home and Mediterranean) to comment on three cruisers which might be laid down in the near future: (a) a modified Fiji (nine 6in, 8,650 tons), (b) a heavy 6in cruiser with twelve guns (14,000 tons, 635ft long), and (c) an 8in cruiser (15,000 tons, 650ft long). They could be completed in March 1944, March 1945 and December 1945 respectively. Both of the larger cruisers had the same protection: 4½in belt, 2in deck (4in over magazines); the modified Fiji had a 3½–3¾in side and the same 2in deck over machinery and magazines. It was faster at deep load (clean), 31kts rather than 30.5kts, but endurance at 15kts was 8,000nm rather than the 11,000nm of (b) and the 12,000nm of (c).
Lillicrap, in charge of cruiser design, envisaged a flush-deck design if the large cruiser was chosen. The forecastle deck would be the strength deck, and the deck below it (the upper deck in British parlance) should be the thick armoured deck, over the whole citadel (he cited the loss of HMS Southampton as justification for armour as high as possible in a ship). The upper (armour) deck should also be considered a strength deck, and stresses calculated assuming that the forecastle deck and side plating above the upper deck had been destroyed. Lillicrap added a new idea. Strength should also be calculated with the ship heeled 30°, which would increase stresses at the deck edge.
Bellona in April 1947. (Photo by Allan C Green via State Library of Victoria)
Above and below: Uganda in October 1944, newly transferred to the Royal Canadian Navy. She and her sisters gained only one quadruple pompom in return for ‘X’ turret, a bad bargain given what Fijis often gained. However, she also had a pair of US-type quadruple Bofors, their shields visible behind the bulwark just forward of the break of the forecastle. She also had eight twin power Oerlikons and eight single Oerlikons. She had been damaged by a German guided missile at Salerno on 13 September 1944, and repaired at Charleston Navy Yard (October 1943 – 1 October 1944). In the process her port crane and six twin Oerlikons were landed, and the two quadruple Bofors, eight single Oerlikons, and the barrage director, an important factor in the ship’s redesign (the object forward of the bridge), were installed. Visible atop the former hangar are her HA director and a tower supporting one of her three pompom directors. Her sisters retained their original close-range battery of three quad pompoms, eight twin power Oerlikons (ten in Ceylon) and six single Oerlikons (eight in Ceylon). Uganda was later renamed Quebec. (Canadian Navy Historical Office)
The Board decided to reintroduce 8in cruisers because the US Navy was doing so, because radar made long gun range more usable, and because it was willing to accept the compromise 6in protection (‘8in guns on a 6in hull’) to hold down size. There was some unhappiness that at the battle of the River Plate (December 1939) British 6in shells had not penetrated the belt of the German ‘pocket battleship’ Admiral Graf Spee; the Japanese were rumoured to be building four or five such ships. Also, even the improved 6in cruiser would displace 13,000-14,000 tons.12 Ships would have cruiser speed (32.5kts, corresponding to 29kts in half-oil condition when six months out of dock in the tropics) and the most up-to-date scale of anti-aircraft firepower. Endurance would be 8,000nm ‘deep and dirty’ (six months out of dock) at 16kts or 12,000nm at 16kts in trial condition.13 In October 1941 an endurance speed of 24kts was suggested (this would also be adopted for a new 6in cruiser). Endurance at 24kts would be 6,150nm. Thus the 1941 programme included four 8in cruisers, to be laid down as soon as possible. They would have been given ‘Admiral’ names.14 This was the ‘large cruiser’ which the Future Building Committee (formed in August 1942) rejected in comparison with a Dido follow-on.
Controller’s instructions in March 1941 led to preparation of four alternative designs, all armed with three triple 8in guns.15 All had a 4½in belt and 2in deck (4in over magazines), as well as the same speed, aircraft arrangements, close-range armament and torpedo armament.16 They differed in long-range anti-aircraft armament: (i) four 4.5in BD mountings, (ii) eight 4in twin, (iii) six 4in twin, and (iv) four 4in twin (forward pair omitted). Controller had emphasised the need for a small turning circle, a difficult problem in so massive a ship. Special efforts would be made to improve seakeeping at speed in bad weather.17 DNC observed that reinforcing the strength deck around the 5ft openings for BD mounts entailed an appreciable weight gain. The Staff wanted new higher-velocity close-range weapons (described as 50–60mm twins, i.e. not Bofors guns), but DNC had no information about them. He therefore provided four quadruple pompoms.18 As in the earlier ships, he reduced standard displacement by including 100 rounds per gun of 8in ammunition, but provided space for the usual 150, and 200 rounds per 4in or 4.5in gun (with space for 400). The belt would keep out 6in shells at 5,500yds (60° inclination) and 8in at 11,000yds (40° inclination). The armour deck was the upper deck, offering advantages both in structure and in protection, but heavier than decks in previous cruisers. It might prevent fires started by bombs, which had burned out some British cruisers. The deck would keep out 8in shells below 21,000yds, and 500lb SAP bombs from 2,500ft (level bombing at 200mph). The 4in over the magazines would keep out 500lb SAP bombs from 10,500ft and 1,000lb SAP bombs from 6,000ft, both for level bombing at 200mph. DNC proposed placing thick bulkheads where the 2in and 4in decks met. DNC particularly cautioned that a margin should be provided against the sorts of additions he had faced during less than two years of war. If 100 tons at forecastle level were to be provided, displacements would increase by 250 tons.
Swiftsure was a further development of the modified Fiji class. She is shown on 31 January 1951, little modified. Immediately after the Second World War she had four quadruple pompoms (note the two aft, on the centreline, before and abaft her after superstructure), five single Bofors, and eight Boffins. By April 1950 two of the single Bofors had been replaced by single power-worked guns of a new type, and there were only four Boffins. Not long after this photograph was taken, she was refitted, the pompoms being replaced by twin Bofors. She was left with nine single power-worked Bofors of a new design, and four Boffins. As modernised she retained her old-type directors. In 1953 plans called for modernising the ship to near-Tiger standards, with 3in guns. She collided with the destroyer Diamond south of Iceland on 16 September 1953 and was repaired and then laid up in the Nore through 1955. She was taken in hand at Chatham in February 1956, for completion in December 1959. In 1958 her planned secondary armament comprised four (rather than the original five) twin 4in and two twin Bofors Mk 5, with a total of six MRS 8 fire-control systems (two for 4in guns only, two for dual-control of 4in and 40mm guns, and two for 40mm guns). By this time it was probably obvious that the projected 3in guns could not be accommodated. Costs escalated, and work was stopped in August 1959; at that point she had two lattice masts and a new bridge broadly resembling that of a Daring class destroyer.
Legends were dated 25 March 1941.19 The design as approved was for 15,000 tons (635ft). With deck armour all on one deck, and with eight 4in guns, it would displace 15,500 tons (640ft); with eight 4.5in, 16,100 tons (650ft); with twelve 4.5in, 17,000 tons (670ft); and with sixteen 4in, 16,600 tons (670ft). DTSD liked the 4in gun but wanted it in a BD mounting; he would go to 4.5in if only that calibre could be so mounted. He also thought that with three directors, eight long-range AA guns were enough (as was then being decided for the modified Fijis).
A sketch design (‘XY’) for a 670ft ship dated 30 April 1941 showed eight twin 4in guns and four multiple pompoms, two on the hangar roofs and two on a deck forward of the bridge. There were two 4in magazines, one roughly below the bridge under four forward 4in twins, one further aft, just forward of the after boiler room, under the after group of 4in twins. This design had three 3in internal bulkheads, which were soon cut to 2in to save weight. The belt was closed by 4in bulkheads (extending 3ft below the bottom of the belt, and 2in thick below that), to keep out shells entering the side plating forward of the main belt. Protection rings were 4in, and ring bulkheads varied from 4in to 2in. In September DEE estimated that the ship needed six 400kW generators, half of which should be diesel and half steam, a considerable jump up from the four 400kW units envisaged in January.
Design work continued through 1941, a new draft Staff Requirement being framed that October (the March 1941 papers had gone astray). Now the ship was expected to displace about 17,500 tons and to be 670ft long, about the size of the US Des Moines class conceived two years later, but without the latter’s automated 8in guns, and with a lighter anti-aircraft battery. By this time she was to have had five octuple pompoms (rather than four quadruples, a considerable jump, which brought displacement to 17,500 tons), as many Oerlikons as could be fitted in, and two quadruple torpedo tubes rather than triples. Protection and speed were unchanged. A formal Staff Requirement issued in December 1941 added RPC for the 4in guns, which would be controlled by four directors, two sided forward and two aft, capable of bearing across bow and stern to handle crossing targets. All versions of the Staff Requirement included Asdic, which British cruisers used to evade torpedoes and submarines.
In October 1941, Controller set priorities for new designs: destroyers, a new armoured carrier, 8in cruisers, and then 6in cruisers. DNC thought that with these priorities new 8in cruisers could be laid down by the end of 1942. By November 1941, 8in mountings for the first ship were on order. Design work continued through early February 1942, as indicated by a request that the model tank (Haslar) provide a power estimate for an 18,500-ton ship (690ft x 82ft x 21ft) to make 32.5kts. Controller stopped most design work about 27 February 1942, although some minor work continued, and the four heavy cruisers remained in the official list of projected ships.
This was a very large ship. In October 1941 DNC sketched an alternative 10,000-ton 8in cruiser with endurance about as in the ‘County’ class, with an 80,000shp powerplant. In mid-January 1942 DGD asked for a quick estimate of a ship with two twin 8in turrets, one forward and one aft. Speed and endurance would be as in Southampton, and protection as in a Fiji. Anti-aircraft armament should be on the lines of a Fiji. DNC offered an 11,140-ton ship (615ft x 70ft) using Fiji machinery and lighter armament (four twin 4in, four quadruple pompoms [two superimposed aft], ten Oerlikons, and two triple torpedo tubes). Beam was scaled from the 64ft of the 1941 Supplementary Fijis (Tiger class).
The 1943 Cruiser
Staff Requirements for a 1943 6in cruiser were formulated in mid-1942 as an alternative to more Fijis.20 ACNS(W) began the process in May by asking whether separate LA and HA armaments were required, and also whether a 5.25in gun would be acceptable for LA fire. Could weight be saved by making guns only partly HA, as in the 55° destroyer mounts then being proposed? Could fire control be simplified to save topweight? Could aircraft be omitted? Displacement should not exceed 10,000 tons, and ten LA guns might be desirable. DTSD thought that aircraft could be omitted, given the future availability of carriers not only with the fleet but on the trade routes (a paper written not long afterwards for the Future Building Committee envisaged trade protection units consisting of a cruiser plus a carrier). DTSD wanted at least four torpedo tubes on each side, although ACNS(W) considered torpedoes ‘a bit of a luxury’. The key issue turned out to be endurance, now that the war had spread to the Far East. Even the improved Fiji lacked it; DTSD wanted something more like a ‘County’, rated at 4,140nm at 25kts (7,600nm at 15kts), compared to about 3,550nm for the improved Fiji.
Proximity fuses having been developed, large-calibre anti-aircraft guns were once more attractive. DGD considered anything smaller than a 6in gun insufficient LA armament for a 10,000-ton cruiser, and wanted a fully dual-purpose main armament. That would simplify fire control. It would be further simplified if the self-contained close-range guns (‘Busters’) under development proved satisfactory (it was not yet apparent how heavy they would be). It might be impossible to mount more than three triple turrets in a 10,000-ton ship, particularly as DGD wanted them well separated from the superstructure for maximum firing arcs. The four-cornered close-range armament should be well clear of heavy gun blast. To DNO, the rationale for separate LA and HA armaments was the pre-war idea that ships engaging other ships might have to engage aircraft at the same time, but that had never happened. A unified main battery was a risk worth taking, particularly if the ship could use divided control to engage a surface and an air target at the same time.
Any dual-purpose weapon had to use cartridge cases rather than bagged charges.21 DNO doubted that a 6in cartridge case could stand up to ramming at high angles under a 112lb shell; perhaps 55° elevation might be acceptable. In any case, it was unlikely that a dual-purpose 6in gun would be available in time for the 1943 cruiser. DNC pointed out that the shipyards could not lay down such a ship until 1944, for completion in 1946, so the Staff chose nine 6in guns in three triple turrets, with 80° elevation. It was hopeless to attempt to provide deck protection against heavy bombs.
Director of Plans concluded that the cruiser should be able to neutralise ships of similar class and to destroy inferior ships (destroyers, raiders) and also to provide anti-aircraft cover on the most ample possible scale. She should therefore be armed with 6in guns, and should have carrier endurance and slightly greater speed. That was taken as 32kts and 6,000nm at 24kts. Endurance forced displacement up to 12,000 tons despite a 10,000-ton limit laid down by ACNS(W).
The resulting Staff Requirement called for nine 6in HA/LA guns in three triple turrets (400 rounds per gun), ten twin Hazemeyer Bofors, twelve twin power-worked Oerlikons, and two quadruple torpedo tubes. Speed should be 31.75kts in standard condition, 30kts deep. Endurance should be 6,000nm at 24kts when six months out of dock in home waters. Protection should be 3½in side abreast magazines and 3¾in abreast machinery, with 2in decks and 1in main bulkheads bounding the machinery spaces. DNC had already produced the corresponding Legend and sketch design.22
DGD was unhappy that this was Fiji protection and pretty much a Fiji armament on 3,000-4,000 more tons, but DTSD considered the displacement reasonable given the increased close-range armament, fully HA main battery and much-improved endurance. The Staff Requirement defined Design A in a new series. It was still being developed as late as October 1942, but by that time alternatives armed with 5.25in guns were also under consideration. The main new development was a proposed triple 5.25in mount.23 In September 1942 the Staff Requirement was passed to the new Future Building Committee.
The Future Building Committee
In August 1942 a Future Building Committee was formed to develop building programmes in view of the desired balance of the future fleet. Deputy First Sea Lord was chairman, ACNS(W) acting as Deputy Chairman. Controller was represented by his Naval Assistant, and membership included representatives of DTSD, DOD (Director of Dockyards), DNC and DNAD. Although it considered all types of ships, the Committee seems to have concentrated on the carrier programme and on carrier aircraft; presumably it was formed largely to change the orientation of the Royal Navy towards a more carrier-based force.24
The Committee discussed the 1943 programme at its meeting on 2 November 1942. Naval Assistant to Controller wanted three cruisers so that design work could be divided among three firms. However, to order them in 1943 would perpetuate the existing Tiger design, which the Committee did not want to do, so it decided to defer any new cruisers to 1944. Meeting on 16 November 1942, the Committee compared two alternative 5.25in guns cruiser designs, one with three twin and one with three triple mountings, Designs K and L in the ongoing series.25 Design L was a step down from some four-turret designs. The 6in HA/LA design was moot, the only available truly dual-purpose cruiser gun being the 5.25in.26 The six-gun design was approved for further development, on the grounds that it was a better carrier escort, and that in front-line cruiser fighting it was desirable because it could be built in greater numbers. DNC developed designs with four twin 5.25in as alternatives.
DTSD demanded that any future cruiser be designed to survive two torpedo hits; Didos had sunk too easily from one hit in the machinery spaces.27 That would spread out the ship’s machinery spaces. Against increased machinery volume, DTSD proposed trading off speed to get better protection. If, as the Future Building Committee asserted, the carrier was the core of the future fleet, then a cruiser, primarily a carrier escort, need not be much faster than a cruising carrier (the carrier needed higher speed for air operations) – as slow as 26kts. A Dido used nearly half her power to go from 28kts to 32kts. The Sea Lords agreed, and in December they asked DNC to sketch 28kt cruisers armed with three or four twin 5.25in mounts. Endurance should be 6,000nm at 18kts, a considerable step down from the 24kt endurance speed of the big 6in cruiser and even the 20kt endurance speed of the 5.25in ship proposed a month earlier.
DAWT and Chief Advisor on Operations Research (CAOR) set the case of the small cruiser armed with six or eight 5.25in guns and numerous close-range weapons (7,000-8,000 tons) against the large cruiser (a 15,000-ton ship armed with eight 8in guns and 4in HA guns). Nearly twice as many small cruisers could be built in place of large ones. The large cruiser would enjoy greater endurance and slightly better sea-keeping, and it would be somewhat better protected, but the smaller cruiser was a smaller target, and was more manoeuvrable (hence better able to evade bombs and torpedoes). Large cruisers were nearly always intended to counter the threat of large foreign cruisers – if a future enemy built large cruisers, would the best counter be large British cruisers or carriers? Looking forward eight or ten years, ‘the only war we can reasonably foresee is an extension of the war against Japan, let us say after a pause while each side has recovered from the effects of the present world war. Any such war will be a mixture of oceanic operations in the Pacific and Eastern Indian Oceans, and Combined Operations in the Indonesian Archipelago’. Cruisers would generally operate with carriers, whose aircraft would be the primary anti-ship weapons. There was therefore no point in building larger cruisers.
DTSD and Director of Plans (D of P) disagreed, however. The future carrier screening role would be filled by 5.25in and 6in cruisers, but a larger and more heavily-armed type was needed for the future balanced fleet. In their view a small cruiser design became unbalanced when required to make more than 28kts – hence the 5.25in cruisers in the design stage were given that speed. However, future aircraft would require higher carrier speed. The 33kt Ark Royal would have a 5kt margin of speed over her escorts. It was undesirable for the carrier to have to conform to the movements of her supporting force, since the strategic mobility of carrier forces would likely become ‘one of the most potent factors’ of a future war; at times high transit speed might materially alter the entire situation. At night or in bad visibility, the carrier escort had to be able to deal with a chance encounter by enemy heavy cruisers and a small 5.25in cruiser would not be enough. Something more powerful than 6in guns was needed. ACNS(W) came down on the size of the small cruiser, agreeing that in the past the Royal Navy had generally preferred smaller ships (he imagined that the Hawkins class, the exception, had been an answer to foreign designs). Cruisers were built to work with the battle fleet and to protect commerce. The former now meant screening carriers; and with the growth in size and sea-keeping capability of destroyers, it seemed less vital. Carriers were now taking over the commerce-protection role, although cruisers were still vital for this role in some waters. Balanced cruiser design had never been very practical, and now large cruisers were almost as vulnerable to bombs as smaller ones. After reviewing historical experience, DTSD was compelled to admit that the carrier escort justification for a heavy cruiser was questionable.
On 8 March 1943 the Committee reviewed DNC’s designs (K4, M1, N1 and P1), of which K4, M1 and P1 were three-turret ships.28 K4 offered the greatest speed and endurance (30kts, 7,000nm), and M1 was the smallest (7,150 tons standard, compared to 7,600 tons and 7,250 tons for the others). P1 offered the best subdivision. N1 was the four-turret ship. The Sea Lords chose the four-turret ship because it offered four-corner anti-aircraft fire and increased LA fire. DGD argued that each of three turrets could have its own HA control, but each of four could not. Although it was impractical to demand sufficient speed (36kts) to keep up with a 33kt carrier, there was interest in higher speed, and DNC was asked to consider an increase to 30kts, with after boilers arranged as in P1 (which suggests that in its case they were not in tandem), as well as increased endurance and the effect of bringing the funnels closer together to give better director arcs. This design had somewhat heavier close-range armament. The revised N2 design (still not capable of 30kts) was discussed at the meeting on 12 April.29
At a meeting in July 1943 the Sea Lords agreed to drop the 8in cruiser. They also authorised preliminary work on a 6in dual-purpose gun mount, while recognising that little could be done for some time, given the press of other work. That left the 5.25in gun as the only available dual-purpose weapon for the next cruiser. The N2 design received the Board Stamp on 16 July 1943, a Staff Requirement being written around it. DNC was later asked to provide more torpedoes, up to eight on each side, the recommended broadside against a fast modern ship. The ship should be able to divide LA fire against two targets. Machinery should be in well-separated units, with two turbo-generators in each unit. Each turbo-generator would be paired with a diesel generator of equal power, as far as possible from the main machinery spaces, and as high as possible (consistent with reasonable splinter protection).
First Sea Lord Admiral Sir Dudley Pound resigned as of 9 October 1943, dying shortly thereafter. He was succeeded by Admiral Sir Andrew B Cunningham, who had been Mediterranean Fleet commander. At its meeting on 17 January 1944, the Future Building Committee was told that First Sea Lord disliked the 5.25in cruiser, preferring a 6in battery, presumably reflecting Cunningham’s experience with Dido class cruisers in the Mediterranean. It was suggested that the 5.25in cruiser be dropped in favour of an improved Belfast, but a paper was written comparing that ship, in nine- and twelve-gun versions, with the 5.25in cruiser the Committee still favoured. The 6in gun was clearly superior (on a shell by shell basis) in surface (LA) fire, since it could penetrate 3in side armour (at 30° to the normal) at 12,500yds, compared to the 5.25in shell at 9,500yds. It could penetrate a 2in deck (which was proof against the 5.25in) at 22,000yds, or a 1in deck at 14,500yds (above 16,000yds for the 5.25in). Both guns had much the same maximum effective range (i.e. the range above which a target could successfully evade fire), but 6in splashes could be spotted at longer ranges (about 20,000yds vs 17,000yds). The 6in burster was somewhat heavier (3.75lbs vs 3.25lbs), so the effect of hits was in the ratio of 8 to 7. On the other hand, the 5.25in fired faster, twelve rounds per gun per minute compared to five for the new 6in Mk 24 turret. Given radar control, both guns would obtain about the same hitting rate per shell fired, so if nine 6in were taken as a rate of 1.0, the eight 5.25in offered 1.9 and the twelve 6in, 1.5. Overall, therefore, the 5.25in ship offered better LA fire. To achieve equivalent long-range HA fire, the improved Belfast would need six twin 4.5in guns of the new type then under development. It seemed to follow that the 5.25in ship was better until a new rapid-fire 6in mounting became available. DGD pointed out that no such mounting could become available for any 1944 ships, so the comparison was between a fully up-to-date 5.25in mounting and a fifteen-year-old 6in mounting. In June, DGD circulated a comparison of possible alternative 6in gun mounts for next-generation cruisers, in effect beginning work on the dual-purpose mounts which eventually armed the Tiger class.30
HMS Superb was the ultimate development of the Fiji design. The most obvious change was substitution of the heavy Mk 6 director, carrying the two antennas of a Type 275 blind-fire radar, for the earlier HA director with its Type 285. However, she was not fitted with the Flyplane computer associated with this combination in later ships; instead she had a derivative of the Fuse-Keeping Clock (FKC) which often equipped destroyers. She was also distinguishable by the two barrage directors forward of her bridge. In this post-war photograph they have been mothballed (their Yagi antennas are not visible) and the pompom directors are missing from the side of the bridge. As completed she had only three quadruple pompoms, three single Bofors guns, and eight Boffins.
A Sea Lords’ meeting on 6 February favoured the twelve-gun improved Belfast, with a secondary armament of six twin 4.5in guns (explicitly mirroring the US Cleveland class). Five such cruisers were included in the 1944 programme. The comment on equivalent HA fire may have been reflected in a decision to provide these ships with six twin 4.5in guns. The close-range armament proposed for all three options was eight ‘Busters’ (self-contained twin Bofors). An Outline Staff Requirement dated 29 February 1944 called for nine ‘Busters,’ as many 20mm as possible, and eight torpedo tubes on each side, with protection similar to that in Belfast. Low speed was abandoned: the ship should make 32.5kts fully loaded and 29.5kts when six months out of dock (presumably in the tropics). Endurance should be 4,500nm at 20kts when six months out of dock. Continuing the series of cruiser designs, this one was designated R.
Wartime cruiser construction had been deliberately deferred in favour of light aircraft carriers. Now new cruiser construction seemed urgent, as the existing fleet was ageing, and it was no longer possible to add much to existing cruisers of the ‘County’, Leander and Arethusa classes. Including the five Tigers, the Royal Navy had fifty cruisers (other than First World War types), whose average age in 1950 would be 12.5 years (fifteen would be at least fifteen years old).
There was still some interest in smaller cruisers. In March 1944 ACNS(W) asked whether they would be wanted in the post-war fleet. There were three choices: the four-turret 5.25in cruiser already sketched, a small 6in cruiser with 4in HA armament comparable to the new Japanese Agano, and a 4.5in gun cruiser comparable to the US San Diego. That August DTSD and Director of Plans framed the case for a small future cruiser, which they envisaged as a 6,000-7,000-tonner armed with three twin 5.25in (two forward) and two quintuple torpedo tubes, plus close-range weapons, capable of 32kts, with an endurance of 5,000nm at 20kts, good protection, and a low silhouette. This was much the previous year’s argument, an additional point being that the small cruiser could operate in mineable waters where a larger and more valuable ship would not be risked, e.g., the British East Coast in 1940. First Sea Lord raised this question in August 1944. At the meeting on 8 August 1944 DTSD noted a tendency for a cruiser – necessarily a small one – to be assigned to lead groups of destroyers. Compared to emerging large destroyers, such a ship would offer better sea-keeping, better armament and better equipment (including, though not mentioned, better command and control). In the past this had been the argument for small destroyer-leading cruisers such as the pre-1914 Arethusas. Others in the Committee noted that such a ship need not have great endurance; it would be used for escort and inshore work. Such ships (presumably mainly the Didos) had proved their value in the Mediterranean and off the French coast. It also might be very difficult to gain political approval of many of the very large cruisers now contemplated. This ship would displace 6,000-7,000 tons, have a speed of at least 30kts, and endurance of about 5,000nm at 20kts. DNC should prepare sketches of such a ship armed with two triple 6in and 4.5in anti-aircraft guns for comparison with the two earlier 5.25in gun designs. It was soon clear that any ship armed with 6in guns would displace at least 8,500 tons, and with secondary armament that would rise to at least 9,000 tons; 6in guns were ‘out of the question’ below 7,000 tons.31 On the other hand, the small cruiser would be needed as leader of a destroyer striking force. This was becoming more important given the complexity of radar and fighter direction. On this basis it was agreed that if a small cruiser was eventually approved displacement should be limited to 7,000 tons and main armament to three twin 5.25in with as many torpedo tubes and Bofors as possible. Protection should be by subdivision rather than armour, as armour offered no real protection against air attack. Endurance should be that of the ‘Battle’ class destroyers, with amenities on a similar scale. Speed should be 30/32kts. In effect the committee was accepting that the separate categories of small cruiser and large destroyer were merging.
The 1944 Cruiser
Work on a new 6in cruiser began with a note from DNC on 9 February 1944: the 5.25in cruiser was dead. The preferred alternative was a 6in ship (improved Belfast) with four triple Mk 24 mountings, displacing about 12,000 tons. A flush deck hull (or a forecastle extending two-thirds the length of the ship) would avoid weakness at the break of the forecastle. Bridge height should be a minimum, and splinter protection should be reduced. Secondary armament should be six (at least four) twin 4.5in guns. Since the twin 4.5in Mk VI was comparable to the US 5in/38, these requirements were about those of the US Cleveland class. By April 1944 DNO was pressing for a dual-purpose 6in mounting heavier than the Mk 24, but not as well protected as the guns in Belfast (a required level of protection). DGD considered the high rate of fire the only way to exploit fully the latest radar and fire-control developments; the US Navy already had a fast-firing 6in turret. The Mk 24 was a further development of the existing turret, now ‘decidedly old fashioned’, limited to six to eight rounds per gun per minute. DGD would ‘feel the utmost concern’ if another programme slipped by without some of its ships being armed with a modern turret. If some could not have the new gun, then two designs should be prepared, one with Mk 24s and one with new ones (which became the Mk 25). Because a modern cruiser should contribute to the air defence of a heavy unit, such as a carrier, which she might be supporting, he fully agreed with the battery of six twin 4.5in guns.
The first of the new design series was Design Q (March 1944), superseded in May by the very similar Design R, with four Mk 24 mounts. The ship was not large enough to take DNO’s projected new mounts.32 As specified, the secondary battery was six twin 4.5in Mk VI guns, as in the new Daring class destroyers, with two Mk VI directors sided forward and one aft. Close-range armament was ten ‘Busters’ and twenty-eight Oerlikons (powered and hand-operated twin mounts in roughly equal proportions). The ship would also have four quadruple torpedo tubes. For anti-submarine self-defence she would have Asdic and fifteen depth charges, the usual cruiser load. Protection was similar to that of Belfast, but the gap between the main belt and the steering gear was filled. The belt would be proof against 6in fire outside 8,000yds or against German 5.9in fire outside 11,000yds (and a Japanese 5.5in shell outside 7,500yds). Deck protection was proof against 6in fire inside 22,000yds, against German 5.9in inside 27,000yds, and against Japanese 5.5in inside 22,500yds.33 Unlike earlier British cruisers, this one had both of her two pairs of boilers abreast. The two units were separated by a block of compartments for magazines and for oil fuel. Boilers were at the after end of the forward unit and at the forward end of the after unit, to reduce total machinery length and to put the funnels closer together, for better gun and director arcs. DNC provided eight 500kW generators, twice the power in the Tiger class. Ships would maintain themselves in half-oil condition by flooding oil tanks after half the fuel had been burned, a settling and sullage tank system ensuring against contamination by sea water. Maintaining this liquid load reduced the risk that the ship would list badly after underwater damage. Design R was chosen in preference to Design Q (of the same size) developed in March 1944.
The 4.5in gun was expected to fire so rapidly that it could add to close-range fire, so DGD asked that the two waist mounts each have their own local director (an MRS), at the cost of Oerlikons (which turned out to be two twin mounts). He also had the DCT atop the compass platform moved back to provide more space for the compass platform, battle bridge and ADP. He also wanted a small closed bridge at the fore end of the structure. All of this could be done, but some clear arcs might have to be reduced. Director of Radio Equipment (DRE) was unhappy that the mainmast was only 8ft abaft the after funnel; funnel gas was already causing considerable problems. He suggested that mast and funnel be interchanged, or that a ‘Weapon’ class solution be adopted, a lattice mast being built around the after uptake. None of this was a problem, as long as shorter radio aerials (strung between the masts) were acceptable.
Alternatives V and W were developed to scale down Design R mainly by changing the secondary battery.34 Apparently these changes were not considered worthwhile. Deputy First Sea Lord asked DGD to review the type of 6in gun mount the ship would carry, for consideration by the Future Building Committee. That practically guaranteed adoption of the dual-purpose mount. Design Y was effectively Design R with Mk 25 dual-purpose triple 6in mounts instead of the earlier Mk 24s.35 That cost about a thousand more tons. There would be two separate long-range LA control systems and three separate HA systems. The design was formally submitted on 12 September 1944. The most obvious difference from the previous design was that the engines were designed to develop 108,000shp so that they could be relied upon for 100,000shp in the tropics. Close-range armament was ten twin Bofors and thirty-two Oerlikons in twin powered and hand-worked mountings.
Writing late in October 1944, ACNS was not altogether pleased by Design Y, because on a much larger displacement it carried what seemed to be little more than the armament of a Cleveland class cruiser, with a total of twenty-one directors. If, as DNO offered, the 6in mounts could have 80° elevation, why bother with the 4.5in? The US Navy had done as much in its J design (the Worcester class). He did not really like a 6in HA gun, and suspected that much of the growth of the ship could be traced directly to the high angle of elevation. Cutting that to 40-45° might make for a smaller 6in turret and thus for a smaller ship. Armour, in this case comparable to that in Belfast, also contributed to sheer size. Should the Royal Navy continue to armour against shells of the sort the ship fired, or should it concentrate on bombs, or should it cease to armour against shells and instead strengthen bulkheads to localise damage?
DNC took this occasion to point out why he had preferred the LA Mk 24in the first place: the growth of Design Y over Design R could be attributed completely to the heavy new gun. For the rest, it was for the Staff to rethink its requirements. He pointed out that from the start he had predicted that carrying the heavy secondary armament would make for a big ship, and had proposed that the ship be armed only with dualpurpose 6in guns and with close-range weapons – which was just what the US Navy was doing. Now ACNS said that he disliked the dualpurpose 6in gun. ‘I am constrained to ask “what does the Staff want?”.’
In mid-November the Staff met to discuss cruiser armour. No affordable cruiser armour could keep out large bombs; the only defence against them (and torpedoes) was subdivision by strong bulkheads. Underwater weapons already did the worst damage, and future weapons would probably exploit that fact. Even so, a cruiser needed some protection against shellfire ‘as the occasions on which a ship is subjected to shell fire are just those in which it may be important for her to be able to continue in action and perform [her] functions’. Perhaps a good compromise would be to reduce the standard of such protection from 6in to 4.5in fire, i.e. against destroyer fire. The minimum range for such protection should be that at which the destroyer torpedo became a greater threat than the destroyer gun, tentatively 5,000yds at a bearing of about 60° to bow and stern. It was agreed that a 2in deck offered no real advantage over a 1½in one, since neither would protect against a 500lb bomb. The loss of protection against 6in fire at long range was accepted. Even so, it would be vital to continue to protect magazines. Early in December, therefore, DNC had his cruiser designer look at modified protection. The belt would be limited to the machinery spaces, its thickness reduced to what was needed to keep out 4.5in shells (4in C armour). As in earlier cruisers, the magazines would revert to box protection against bomb, shell and torpedo attack, their deck area minimised. The number and thickness of protective bulkheads would increase.
As a first cut, Scheme 1 provided 4in C on belt and bulkheads (reduced to 100lb NC below certain level) and 60lb NC on deck. The belt was closed by 4in bulkheads. The magazines had 4in sides and bulkheads and 6in crowns. Turret roofs were 6in NC, to cover the openings in the magazines through which ammunition was passed up to the turrets. An alternative Scheme 2 was the original armour scheme with thicknesses reduced to keep out 4.5in shell. It was rejected as impracticable, because the ship would have been lengthened about 25ft to carry the increased weight (due to the greater area protected). To cut weights, DNC decided that deck protection against 4.5in shellfire could be reduced (where not needed for strength) from 60lb NC to 25lb DW (on the lower deck over the machinery). On the other hand, provision had to be made against diving shells. Thus 4in armour might have to extend for the full depth of the 6in magazines at the ends, and also over the sides of the 4.5in magazines amidships. The ends of the midships 4.5in magazines should have 100lb (2½in) NC to protect against splinters. Some reduction in steering gear protection was possible. These changes gave a standard displacement of 15,694 tons.
A third possibility was to minimise the magazines’ deck area by working them on two levels (hold and platform deck), with shell rooms in the space saved. However, the upper part of the magazine would be above water, and the usual flash-tight arrangements could not be fitted. To protect the engine rooms against plunging 4.5in fire between lower and upper deck, the 4in belt could be extended up between those decks over the length of the forward engine room.
A fourth possibility was to put the magazines down on the inner bottom, working two magazine flats, thus shortening the length of the magazines. This idea took advantage of the considerable space below the magazines devoted to watertight compartments (this space amounted to 7.5 per cent of the displacement). The ship could be shortened about 15 per cent and perhaps the beam reduced as well.
Overall, Design Y had 2,344 tons of armour, about 15 per cent of her standard displacement (as rearmed, Belfast devoted 17 per cent of her displacement to protection). That included a 984-ton belt (4½in) and 862 tons of deck armour. The 4.5in standard proposed by the Staff could be met by a 4in belt (saving 176 tons) and making the deck thinner would save another 312 tons. Even more could be saved by reverting to box protection for the magazines (468 tons on the belt, 779 tons on decks). The weight saved could improve protection with priority (a) underwater, (b) bomb, and (c) shell.
DNC pointed out that tighter subdivision would not improve survivability, because what counted was the length over which a given weapon would tear up a ship’s hull. The longest compartment in the ship was 36ft long, but a modern torpedo would disrupt a ship over a length of about 70ft. Maximum floodable length would be 110-140ft. Something could be achieved by increasing the number of thick bulkheads from four to six, and increasing their thickness to 60lbs below the platform deck, and to 40lbs between platform and lower decks. The weight involved would be modest (68 tons). The magazines were not adequately protected against diving 4.5in shells or from such shells penetrating below the side armour at a 10° heel. To solve that problem would take 370 tons: 4in C on magazine sides and 100lb NC on longitudinal bulkheads. That would consume almost all the saving achieved by reducing armour thickness. Reducing the extent of armour and boxing the magazines could make another 800 tons available. To make the magazines safe, DNC wanted 6in on the deck over them and 4in and 100lbs on their sides and ends, and also to increase turret roofs to 6in. Including 60lb on the steering compartment, that came to 1,493 tons, well beyond the saving envisaged, adding 250 tons to the ship. ACNS also wanted magazine vulnerability reduced by reducing their deck area. For example the magazines could be enclosed entirely within turret ring bulkheads extending down into the ship’s hold, on two levels. The circular shape offered problems, however. DNC offered an alternative which preserved the rectangular shapes of the magazines. The combination involved added 1,372 tons of armour.
Design Y was to have been built as the Neptune class. Note the unit machinery, separated by a 4.5in magazine. Displacement would have been 15,350 tons standard (18,740 tons fully loaded); dimensions would have been 655ft (waterline) 662ft (overall) x 76ft x 24ft 9in (full load). Four Admiralty boilers would have produced 108,000shp for 33kts. Endurance would have been 7,500nm at 20kts (2,850 tons fuel oil). As a flagship she would have accommodated 1,351 men. Armament was twelve 6in Mk 25 using two DCT for surface fire; six twin 4.5in dual-purpose guns, ten ‘Busters’ (selfcontained twin Bofors), and fourteen twin power Oerlikons, plus four quadruple torpedo tubes. Anti-aircraft control for both 6in and 4.5in guns would have been exerted by three LRS I directors with a new radar (apparently Type 901 in its initial incarnation), plus six MRS (two for 6in, four for 4.5in). ‘Buster’ mountings had on-mount radars. Armour would have been a 4in belt amidships with 4in bulkheads and 1.5in extensions fore and aft and 2.5in on 1in in machinery spaces. The upper deck would have been 1.5in over machinery and steering gear, and 1in elsewhere. The lower deck would have been 1in. Turrets would have had 4in faces and 2in sides, rear, and crowns. Note the effort to separate the forward and after machinery units. (A D Baker III)
DNC preferred the scheme using the space in the hold but did not like reducing general splinter protection to communications and important services to buy 6in NC over magazines. He decided to keep protection over the area in the original design but to reduce thicknesses to keep out 4.5in shell: 4½in C side reduced to 4in, 80lb NC on upper and lower decks reduced to 60lb and 100lb NC on transverse bulkheads. Weight saved would be devoted to thickening bulkheads and to fitting additional side protection below the main belt in way of magazines. Side armour would be continued to a depth of 1ft below the waterline at 10° heel in half-oil condition. The lower edge of the side armour below the waterline in way of the various magazines was then 4ft 9in for the forward block, 5ft 9in amidships, and 4ft 3in aft. Underwater protection was improved by increasing the number of thick bulkheads and increasing their thickness from 40lb to 60lb DW (cost 70 tons). Weight freed by reducing magazine length provided additional splinter protection to magazine boundaries: 60lb DW sides and ends, 40lb DW roofs and flats. To preserve trim, the citadel was moved about 6ft aft.
Overall, the hope that rearranging protection would cut the size, hence the cost, of the ship was not fulfilled. Ship size was governed mainly by the weight and space required for the main and secondary armament. In this ship armament weight was about 50 per cent more than in Belfast as rearmed. The length of the citadel was governed by the layout of the upper works, which was already cramped. There was no hope that the ship could displace less than about 15,000 tons.
The design was modestly revised in January 1945, its displacement increased slightly.36 In February 1945 DNC assembled building drawings and specifications for Board approval. At the end of December 1944 Director of Plans pointed out that, as the end of the war approached, national shipbuilding capacity should be shifted towards replacing the merchant fleet. The naval programme would be cut back, ships expected to complete after 1946 being reduced to slow building rate. The suspended Tiger class cruiser of the 1941 supplemental programme, which had been suspended, should be built to the new design, making a total of six such ships. They should be completed no later than 1950.37 By this time the 1944 Cruiser was being called the Neptune class.
Apparently it took time for DNC’s comment about 70ft damage length to sink in, because only in mid-June 1945 did he point out that the boiler rooms were not far enough apart. A single properly-placed hit would knock out all power. He could increase separation from the original 52ft to 62ft, by placing the forward boiler room on the fore side of the forward engine and gearing room, reducing the midships block to that required for the 4.5in magazine. To straighten uptake lines and to keep the foot of the foremast from passing through the fore uptake, he had to rake that funnel and mast, and therefore the after pair as well. Thick bulkheads would be rearranged. E-in-C wanted the boilers at the fore end of the forward boiler room (to simplify the run of main steam pipes), so the uptakes had to be brought even further forward. DNC observed that earlier arguments for and against raking masts etc, because of range-finding and inclinometry were surely no longer valid with the advent of radar. At about the same time, detailed design of the Mk 25 mounting showed that the original roller path diameter was inadequate.38
The Neptune project survived the end of the war. In November 1945 First Lord decided that two ships should be laid down as soon as possible (Controller suggested waiving tender rules so that information could be forwarded to firms by April 1946). The required crew grew, and improved habitability standards (soon to be ‘25 per cent increased amenities’) demanded a larger ship, perhaps with a flush deck. DGD now proposed for future cruiser armament a combination of dualpurpose 6in and 3in guns as in the US cruiser Worcester. His proposed 6in mount became the Mk 26 of the post-war Tiger class.
At a Deputy First Sea Lord’s meeting on 29 January 1946 DNC reported that Design Y was well advanced; he was ordered to redesign it with the desired improved habitability. DGD’s new design should also be considered (as Design Z). Proposed armament was five twin dualpurpose 6in guns and eight or ten twin 3in. The ship should displace about 12,000 tons, with a complement of 800–900. Elimination of the 4.5in battery would, it was hoped, greatly reduce the number of directors needed. DNC’s instructions of 8 February were to retain the flush upper deck of the earlier design, but try to reduce its length by about 30ft. Alternative arrangements should include three turrets forward and two aft, and two forward, one amidships, and two aft. To reduce weight, side protection should be cut from 4in to 3½in if that sufficed against 4.5in shells at 8,000yds range. If possible the 60lb deck of the earlier design should be retained, but bulkhead protection could be reduced from 60lbs to 50lbs. The separation between machinery units would be retained. DNC doubted that the complement goal could be met. Eliminating the 4.5in secondary battery could help, but only if the 3in mounts were self-contained, like Bofors guns, not if they were on the lines of 4.5in guns and mounts. DNO thought the twin 6in would weigh about 160 tons, but when Vickers supplied three designs in March, he considered only the largest and heaviest (184 tons) plausible.39
Design ZA (Minotaur) was the final development of the wartime cruiser design series, introducing the twin 6in DP and twin 3in mounts employed in the Tiger class. (A D Baker III)
DNC pointed out that for LA fire the heaviest shell was best, whereas for high angles the smallest shell which could accommodate a proximity fuse and enough explosive to be effective at the range of the fuse (20yds) was best, meaning a 3in shell. The lower limit for a LA shell was 5.25in. The US Navy was beginning work on a twin 3in/70, which might be equivalent to the existing British 4.5in.40 DNO eventually decided to adopt the same calibre, apparently on the theory that in wartime the Royal Navy would have to depend on the United States for supplies of spare barrels and ammunition. DNO’s initial estimates were based on the sextuple Bofors guns being installed on board the battleship Vanguard.41
As an initial estimate, total armament weight (five twin 6in, ten twin 3in and four quadruple torpedo tubes) was 2,193 tons. Based on past designs, that suggested a standard displacement of 15,960 tons rather than the 12,000 tons imagined in January. DNC developed a series of designs with three, four or five Mk 26 mounts, all designated as different versions of Design Z.42
A Sea Lords’ meeting on 5 June 1946 compared Neptune with three versions of Design Z: B, with five twin 6in, C with four, and D with five and a revised machinery arrangement for better survivability. First Sea Lord considered only D acceptable. It was armed with five twin Mk 26 and with eight twin 3in (not yet 3in/70) plus four quadruple torpedo tubes. Three superfiring twin 6in mounts were forward (as in a Dido, for example) and two aft.43 The project was designated Minotaur, to distinguish it from the series of Neptune designs. It replaced Neptune in the building programme, but only limited design work was ever done. Minotaur would displace 15,280 tons in standard condition.44
DNO was scrambling to produce higher and higher rates of fire, because fast new aircraft (and missiles even more so) had to be destroyed so quickly. Thus in 1947 he proposed a quadruple 3in gun, and previously a sixteen-barrel Bofors had been considered as an alternative to the 3in. All of these weapons were massive, and they pushed up ship size. DNC produced a new series of designs, P, Q, R and S, with five, four, or three twin 6in, with varying numbers of 3in, and with and without torpedoes.45 The designs suggested that two quadruple 3in were about equal to one twin 6in in both weight and the volume required below decks. Given a series of unpalatable alternatives, DNC suggested that a future cruiser should be able to engage two surface targets, hence should have either two or four twin 6in, plus six or four medium range antiaircraft (twin 3in), plus the desired torpedoes. That led him to consider a Fiji-size cruiser with a twin 6in at either end. An attempt to design such a ship with three quadruple 3in and with the widely-separated unit machinery developed for the recent designs produced an unacceptable 15,500-tonner, 570ft long. DNC was just about to work out plans to modernise the fleet using twin 6in guns and twin (not quadruple) 3in, the only fruit of which was the Fiji-sized Tiger. She displaced about 12,000 tons deeply loaded. The key difference with the 1947 study was probably not so much the use of twin 3in (which were a good deal heavier than expected) but the omission of the unitised machinery.
In 1947 DNC compared the Minotaur design with USS Worcester, details of which had just become available. Despite having an extra 6in turret, Worcesters armament weighed only 74 tons more. The US twin turret was 36 tons heavier than the British Mk 26 due to its heavier armour, but less ammunition was carried. Mk 26 also allowed greater depression (15° rather than 5°). Over 30° arcs to each side of the centreline the US Nos 2 and 5 turrets had to elevate to at least 15° to clear the adjacent main deck turret – reducing silhouette and top hamper. The board margin in Minotaur was equivalent to one 6in turret in Worcester. The open US single and twin 3in/50s were not comparable to the British twin 3in gun envisaged for Minotaur, which offered twice the rate of fire and completely mechanised loading to cut the reloading period to a minimum. Magazines had to be in the same fore and aft position as the guns they served. The estimated weight of the British mounting was 35 tons, compared with 14 tons for the US twin. On a weight for weight basis, the lack of torpedoes in Worcester was comparable to the lack of aircraft in Minotaur.
Both ships devoted about the same amount of weight to armour and to hull. The lower structural weight of the US ship was consistent with the higher stresses accepted in the design. Some weight was also saved by welding, which was more extensive in the US ship, which also devoted only about half as much weight to general fittings.
DNC noted that the total space above the lower deck in Minotaur was about the same as in Worcester, although the latter had a larger complement. Space taken up by boilers in Minotaur had to be compensated for in the superstructure, adding weight and reducing stability. The British design could be made substantially smaller by reducing space requirements, but the smaller Neptune had been rejected precisely because she was too small to meet the space requirements.
Although Worcester had far higher power (120,000shp plus provision for 10 per cent overload), her powerplant was only 50 tons heavier than Minotaur’s. DNC attributed this disparity to fewer electric generators and to the omission of propeller disconnecting couplings. He noted that the more compact American boilers lay entirely below the lower deck, whereas in Minotaur, as in previous British cruisers, the boilers extended up to the main deck. The Worcester arrangement reduced armour extent and weight, which freed valuable lower deck space. However, the Worcester machinery spaces were much longer, making her more vulnerable to torpedo hits. One major hit between the after boiler rooms could flood both engine rooms and immobilise the ship; Minotaur would do better. Both ships used the same type of machinery, but Worcester was rated at 8.0 rather than 8.8 tons per hour at 20kts.
The comparison file includes a drawing of alternative Z4C, modified as in July 1947, with combined engine and boiler rooms. DNC developed two smaller alternatives to Minotaur, designs ZA and ZB, which offered the same armament, speed, etc. but not the estimated required space (ZA did not provide a Board margin). In effect these sketches showed the effect of wartime space demands. ZA was the smaller version, ZB being enlarged to include the 2 per cent Board margin of standard displacement.
By 1947 Royal Navy planning was based on a ten-year period before war might once again be imminent.46 Construction of six Minotaurs was justified because in 1956/7 so many cruisers would be overage. Thus the proposal called for laying down two ships in each of 1951, 1952 and 1953, for completion in 1954, 1955 and 1956 respectively. This plan collapsed both because it was utterly unaffordable, and because priority went to carriers and to anti-submarine craft.
Vickers Design 1122 was the wartime Admiralty Black Prince design offered for export post-war (Design 1123 was HMS Swiftsure). Neither sold, and Vickers developed a new Design 1124 embodying systems it hoped to manufacture. The plan of the hold shows the characteristic machinery spaces of British wartime and late pre-war cruisers, with the unfortunate longitudinal bulkheads surrounding the after boiler room, the boilers being in tandem. (National Maritime Museum)
Vickers developed the Dido into this small cruiser, which it offered to post-war customers. Only the South American governments were likely to be able to buy such ships, and the likely target customer was Venezuela, which in the late 1940s tried to buy a Dido. Note that the earlier boiler arrangement (two side by side, two in tandem) was retained. The twin mounts are 5.25in, the smaller weapons are twin Bofors guns. There was also a three-turret version with twelve single Bofors, six of which occupied roughly the same space as ‘X’ turret here. This version also had a seaplane amidships, but not a catapult, where the four-turret version carried no aircraft. Unfortunately no details of the design have survived, apart from a sketch of planned protection. (National Maritime Museum)
Above and below: Vickers designed a new large cruiser as Design 1124A. In this sketch the heavy guns are triple 6in, and the smaller turrets are 120mm (4.7in, presumably Bofors twin) anti-aircraft guns. The search radars are British, but the directors are not. For example, the director immediately atop the bridge, for the main battery, seems to resemble the US Mk 34. The 120 mm director seems to use the British Type 275 radar, but it is shaped more like a US Mk 37 (it certainly is not the usual British Mk 6). The absence of helicopter facilities dates the design to the late 1940s or early 1950s. This design was also described as the Vickers ‘stock cruiser’, i.e., as the basic design it offered potential clients before developing follow-ons to suit their tastes. It had an 81mm belt (over 12.5mm side plating) raised to cover the boilers, extending between the outer parts of the end barbettes. It was covered by a 50mm deck and closed by 50mm bulkheads (including bulkheads closing off the raised section). The end bulkheads below the belt were 37.5mm thick. Barbette armour thickness varied around each barbette, from 19mm at the ends to 25mm at the sides. The steering gear was protected by 37.5mm sides and 31mm deck and inboard end. A cross-section at the after boiler room shows the same longitudinal bulkheads that had caused trouble in the Second World War, but with voids between them and the oil tanks outboard, to limit flooding in the event of underwater damage. A list of Vickers drawings identified Design 1124 as an Argentine cruiser. Hopes that British builders could sell to the three large South American navies must have been damaged when the US government gave each two Brooklyn class cruisers. Even so, in 1952 (after the US deal had been arranged) the Brazilian naval attaché approached the British to build his country a small fleet, including two cruisers and one or two escort carriers. The British refused because the programme would have disrupted their ongoing rearmament – and because Brazil planned to pay in sterling that it had accumulated during the Second World War, rather than in the dollars the British wanted. Overall, in the wake of the American deal Venezuela, oil-rich and ambitious, seems to have been the likeliest customer for new cruisers. (A D Baker III)
A follow-on large Vickers cruiser might be compared to the Admiralty’s Neptune, with 4.5in secondary guns plus twin Bofors and twin power Oerlikons. This drawing is undated, but the helicopter hangar suggests it was drawn in the mid-1950s, when Vickers hoped to sell a cruiser to Venezuela in the face of US official opposition. (National Maritime Museum)
The modernised Sheffield, seen in July 1957.