DESTROYER-KILLERS
The Arethusa class
In about 1907 the Germans became interested in taking destroyers to sea to support their battle fleet, but by this time the Royal Navy considered destroyers operating in direct support of the battle fleet a danger both to themselves and to the capital ships. This departure from what had become standard practice in the Mediterranean Fleet can probably be traced to increasing gunnery range, which made it far more difficult to insure against friendly-fire accidents. As Mediterranean Fleet commander, Admiral Sir John Fisher had in effect invented tactics in which British destroyers worked directly with the fleet, but as First Sea Lord he abandoned them in favour of distant blockade of German destroyer bases coupled with the use of destroyer flotillas for home defence. He became less and less convinced that the battle fleet could operate effectively in the North Sea, to the extent that he preferred to buy battlecruisers, which had an important trade-protection role in distant waters. This was by no means a widely-held view. When Fisher’s successor as Mediterranean commander, Admiral Sir Charles Beresford, took over the Channel Fleet, he objected to Fisher’s centralisation of torpedo craft command, arguing that he had to have destroyers as part of his fleet. Beresford went so far as to conduct exercises in 1908 to demonstrate that without them he could not fight a fleet with its own integral destroyer force. The Admiralty staff (i.e. Fisher) dismissed his account of the exercises with the bald statement that the Germans, like the British, would be operating their destroyers separately from the fleet. This claim may have been mirror-imaging, or part of Fisher’s ongoing war with Beresford. To some extent, also, Fisher’s belief that neither battle fleet could survive in a narrow sea in the face of masses of torpedo craft, including submarines, rendered such exercises pointless.
HMS Galatea is shown in 1919, with typical First World War modifications. She, Aurora, Inconstant, Phaeton and Royalist were all fitted with two 3in guns in 1917, replacing the former single gun (mounted in 1915). However, Penelope and Undaunted both had a single 4in anti-aircraft gun forward of the after 6in gun. (Perkins)
Once Fisher left the Admiralty in January 1910, battle fleet operations in the North Sea were taken far more seriously. Admiral William H May conducted exercises to examine the consequences of the newly-perceived German practice of operating destroyers with their fleet. Having completed the experiments early in 1911, May concluded that light cruisers were the appropriate counter to German fleet destroyers. In the blockade role destroyers were necessary, because they needed the speed to run down German destroyers as they appeared. They were poor gun platforms, but they would have time to sink the German ships as they ran with them, but when trying to deal with German destroyers rushing the British battle line, they would not have enough time to make up for their poor gun platform characteristics. This conclusion seems not to have had an immediate impact. First Sea Lord Sir Arthur K Wilson apparently planned to attack the German destroyers and submarines in their ports (later tacticians would call this ‘attack at source’) because he doubted that any form of blockade would succeed. He seems not to have accepted the new view of how the Germans would use their destroyer force. Wilson described his war plan at an informal meeting in 1911 in Whitehall Gardens, called because war seemed imminent due to the Agadir crisis. A horrified Prime Minister Asquith decided that Wilson was a fool (he had failed adequately to explain his reasoning), and appointed Winston Churchill First Lord of the Admiralty (roughly equivalent to a US Secretary of the Navy) to push the Royal Navy towards saner operating concepts.
HMS Arethusa as in March 1914. The forecastle and upper (main) deck were planked, as was the bridge, but the deckhouse amidships (in effect the boiler casing) had steel decking. A reload torpedo magazine was located on the first platform deck, the reloading hatch being just abaft the aftermost deckhouse (six reloads could be carried). Torpedoes were reloaded via overhead travelling lift gear fitted between the centreline deckhouse sides and the officers’ and warrant officers’ washroom deckhouse. Folding platforms outboard the 4in mounts were removed during 1915. Surviving ships had two more twin torpedo tubes added during 1917. In 1918 conning towers were removed and a third 6in gun replaced the two after 4in guns. The foremast was given tripod legs to support a fire-control top, and a flying-off platform mounted forward of the bridge. Four of the surviving ships (Galatea, Phaeton, Royalist and Undaunted) could tow kite balloons. In 1918 all were fitted to lay mines. (A D Baker III)
Churchill had no naval experience whatever, but he was nominally responsible for the main features of the ships of the 1912/13 programme, including the Queen Elizabeth class battleships and the Arethusa class cruisers. It is not clear who advised Churchill, but he was close to the former First Sea Lord Admiral Sir John Fisher. Both classes (and also the destroyers of this programme) emphasised speed. The new ‘Town’ class cruisers were not fast enough to deal with German destroyers, and so early in 1912 Churchill verbally instructed DNC Philip Watts to develop a new fast light cruiser to deal with German destroyers. The DNC Department First World War cruiser history, dated October 1918, attributes the new ship to the considerable interest aroused in the autumn of 1911 by the new Italian cruiser Quarto, which achieved 28kts although she was about the same size as the earlier British Boadicea (25kts). In effect Quarto demonstrated that a small ship could combine the performance of new seagoing destroyers with cruiser protection and firepower, something not previous achieved. It was also reported that the newest German cruisers (the Breslau class) were faster than British light cruisers, and better protected, though not as well armed. It appeared that these fast new cruisers achieved their speed by using oil fuel and by adopting faster-running machinery closer to destroyer standards. The Arethusa Cover does not mention any of this.
The Cover is marked ‘New Fearless’, so presumably it was conceived as an upgraded version of that ship, which in turn had been (in effect) a destroyer leader. An initial sketch submitted on 10 January 1912 showed a 3,500-tonner (30kts) protected with 2in side armour over the machinery spaces, 410ft x 42ft, carrying 300/800 tons of fuel. She was about the size of the earlier cruiser Active. Armament was two 6in guns, four 12pdrs, four machine guns (Maxims) and two 21in torpedo tubes, whose total weight was the same as the armament weight of the Active. DNO preferred 4in guns to 12pdrs (the same shift was occurring in contemporary British destroyers), and wanted two more torpedo tubes. DNC submitted the resulting revised design on 16 January, commenting that no modification would have been required had the after 6in gun been replaced by a 4in. At this stage the ship was called a Third Class Cruiser. An earlier but undated design (which survives in the Cover) had an all-4in gun armament, including two guns side by side on the forecastle and the quarterdeck (and four single 4in on each side in the waist). This sketch may merely be an updated version of HMS Active, which was armed with ten single 4in guns (although the sketch is not marked as such). Note that Active lacked the side armour of the new design. The new cruiser would be longer than Active (410ft rather than 385ft between perpendiculars) and much faster (30kts rather than 25.3kts, on 40,000shp rather than 18,000shp).
Above and below: Nearly all British First World War light cruisers were derived from the pre-war Arethusa class. HMS Aurora is shown newly completed (the towers aft were presumably temporary trials fittings). The reduction to one mast reduced radio range but it also made it more difficult for enemy ships to estimate the cruiser’s course.
There may have been some interest in a cruiser based on the big destroyer Swift; the Cover includes estimates of steaming radius for both the Super-Active and the Super-Swift. However, that comparison is the only reference to the Super-Swift in the Cover, and it is difficult to see a Super-Swift as a heavily-gunned destroyer killer. The new cruiser had far more endurance, making her much better suited to operating as an integral part of a battle fleet (4,400nm at 15kts compared to 2,400nm at 16kts). Because direct-drive turbines offered poor efficiency at low speeds, the ships had cruising turbines. Turbines were rated at 7,500shp each, with 10,000shp overload rating for a short time (at 650rpm). Boiler pressure was 235psi. The engines were in two engine rooms, and the eight boilers in two boiler rooms. All had Parsons Impulse-Reaction turbines except for Arethusa and Undaunted, which had Brown-Curtis. As in a destroyer, the uptakes from the after boilers in the forward room and from the forward boilers in the after room were trunked together to form a fatter second funnel between two narrower ones. Late in the design process it was decided to rake the mast and funnels because the mast did not support a boat derrick, hence did not have to be vertical. While the ships were being built, it was pointed out that the high power (10,000shp per shaft) would probably necessitate experiments with alternative propellers, but that proved impossible due to the outbreak of war, and the ships actually made 18.5 to 29kts.1
An internal DNC memo dated 29 February 1912 instructed the DNC staff to push the ‘New Active’ design as quickly as possible, with an armament, if possible, of twelve 4in guns – which might be difficult to fit in. Submerged torpedo tubes should be adopted to leave more space (for the guns) on the upper deck. Space was a problem because, DNC wrote, ‘it is inexpedient to lengthen ship’. A sketch design for the all-4in ship was submitted in March 1912. In March the First Sea Lord asked for alternative ten- and eight-gun arrangements. DNC pointed out that weight saved that way could go into side armour over the machinery: an extra quarter-inch with ten guns, an extra ½in with eight guns. One of the ten-gun arrangement showed the two after guns en echelon, well separated lengthwise, to give a six-rather than five-gun broadside (as in the twelve-gun ship). One of the eight-gun arrangements showed single centreline 4in guns at the ends, to give the same broadside as a ten-gun ship with paired guns fore and aft. The result might seem comparable to Active, but a March 1912 note on complement observed that the earlier ship provided enough crews only to man one broadside or the other, whereas the new cruiser would have enough to man all her guns simultaneously – which would make sense, as she would be engaging German destroyers rushing past her to attack the British battle line. In addition, it appeared that she would be armed with faster-firing QF (quick-firing, i.e. fixed ammunition) rather than breech-loading (BL, i.e. separate ammunition) 4in guns (but ammunition allowance per gun, 250 rounds, would not change).
HMS Royalist shows typical First World War modifications: a flying-off platform, the conning tower removed, a tripod foremast with a spotting top (but no heavy director; these ships had limited reserves of stability), a 3in anti-aircraft gun aft (actually one of two, to either side). One pair of 4in guns was replaced by a 6in gun on the centreline, forward of the after conning tower (barely visible here). The two pairs of deck torpedo tubes are not visible. (E Hopkins of Southsea courtesy of Josef Straczek)
To save hull weight, the armour was incorporated into the hull strength, a 2in outer layer covering the 1in hull plates, which had not been done in the ‘Town’ class. To this end strakes were worked longitudinally rather than vertically; there was later some fear that hits would break up the sandwich of armour involved. Total thickness was 3in over the machinery (and fuel tanks) amidships. That was quite respectable. After her action with Emden, the Captain of HMAS Sydney wrote that his 2in side armour had proven very valuable, since it defeated the standard German cruiser gun (4.1in) at 8,000yds, and probably at much shorter ranges. Fortunately the German shells rarely burst (had they done so, the ship’s fore and aft controls would have been put out of action in the first few minutes). They also fell steeply enough not to ricochet. The Captain concluded that at least one control position should be behind armour. He rejected the existing conning tower.
DNC planned to extend side armour to the ends (1¼in thick); Churchill preferred protective decks at the ends. However, the extended side plating was important for structural strength; more structure would be needed to make up for the discontinuities at the ends of the belt. The weight saving was vital if the ship was to make the desired speed. Also, First Lord’s preferred armour decks would complicate internal arrangements in a ship in which space was at a premium. DNC suggested a compromise, extending the belt armour about 60ft fore and aft of the machinery spaces (but to reduced height). That would provide 2in sides instead of the earlier 1½in sides, and a 1in arched deck over the steering flat instead of the previous quarter-inch deck. The extended belt would cover the lower conning tower, magazines, and shell rooms. The original 1½in plating was extended all the way to the bow, but 2in plating was extended only 30ft further aft and to a reduced height. All of that would cost about 40 tons, but about 20 tons would be gained back by eliminating the 1½in side over the steering compartment. Other detail cuts might save another 10 tons (for example, the lower conning tower side could be cut by an inch since it would be behind thicker armour). The new arrangement had the additional virtue of improving internal arrangements. Churchill approved. Ultimately ships had 1in to 1½in additional armour forward of their machinery, extending from 3ft below the upper deck to 2ft 6in below the load waterline. Aft of the machinery spaces they had 1½in extra armour back to the rudder head, from 3ft below the upper deck (cut down to 5ft 6in aft) down to 2ft 6in below load waterline. Hull plating itself was 1in to ½in thick. The machinery was protected from aft by a 1in after bulkhead, presumably to resist the fire of a pursuing enemy cruiser. Arethusa had a 6in conning tower with a 4in tube, ultimately replaced by a 3in conning tower with a 2in tube in these ships. The Legend showed no protective deck other than plating over the steering gear (side and deck were considered equivalent to 1½in). The continuous part of the upper deck was 1in thick for strength rather than for protection. Its role was made clear when the Captain of Arethusa (lead ship of the 1912/13 cruiser class) complained after the Heligoland Bight battle (28 August 1914) that parts of the superstructure acted as a shell trap, and that therefore the forecastle should have 1in armour to protect spaces below from fragments, but that would have added too much weight. Much of the lower deck had to be cut away to accommodate the large boilers. Because the ships burned oil to achieve their desired high speed, they lacked the coal bunkers whose bulkheads transversely stiffened earlier ships. It therefore became important to stiffen the ships transversely around their boiler rooms, by continuing the deep web frames in the machinery spaces above the lower deck. The structural arrangement incidentally doomed the idea of lower-deck torpedo tubes, because they entailed cutting the ship’s side just where the heavy plating was. Moreover, there would be insufficient deck height to handle torpedoes freely, and tubes set low in the ship’s side would fire their weapons directly into the waves created by the ship at high speed. The combined structural and protective arrangements became standard for the First World War British light cruisers derived from the Arethusa class.
Estimates of the required complement showed that the ship was not large enough to accommodate it; manning the guns and the submerged torpedo tubes was apparently the problem. In April, Churchill proposed to solve the problem by cutting to ten guns, with crews for seven of them (saving thirty men) and by adopting deck torpedo tubes, which saved another three men. However, the twelve-gun alternative was chosen by the Board, with QF guns of higher velocity than those being adopted for destroyers (45 calibres rather than 40 calibres). In May 1912 the Board sought to solve the weight problem by limiting each gun to 140 rounds, rather than the 250 earlier envisaged. That still left the space problem.
The Board approved the design on 7 July 1912 (DNC submitted it on 1 July). This version showed ten 4in QF guns and two upper-deck single 21in torpedo tubes; it is not clear when the Board reversed itself and approved a ten-gun armament. The Legend showed 200 rounds per gun.
Endurance was clearly considered important, because in the submission to the Board Watts pointed out that the ship could make 5,000-5,500nm by running on two shafts and trailing the other two. Estimated radius with four shafts on line was 4,000nm. In Legend or trial condition, ships carried 300 tons of oil fuel. Deeply loaded they carried 800 tons, including 140 tons in peace tanks (so called because, being above the waterline, they could not be filled in wartime). Later the total was given as 810 tons, a great deal for a 3,500-ton ship. As more and more topweight was added in wartime, stability in the light condition became less and less satisfactory – but it was possible to remedy that by flooding empty fuel tanks with sea water. Arrangements to this end were ordered in August 1916. DNC considered this modification a prerequisite for many newly-required improvements, including a tripod mast for fire control. The 1912/13 programme included eight ships of this Arethusa class.2
About November 1912 the First Lord (Churchill) decided to substitute single 6in guns for the paired (abreast) 4in guns at the ends of the ship, despite the considerable modifications involved; for example, the conning tower and bridges had to be raised about 3½ft to avoid gun smoke interference with the rangefinder on the bridge roof, and the funnels had to be raised similarly. The ships were given additional flare (to reduce wetness on the forecastle) and high spray shields fitted to reduce spray over the forward guns. The ships had already been ordered, so this change was hardly inexpensive. The rapidly-fired 4in gun was considered ideal as a destroyer-killer, but the 6in was wanted to deal with enemy cruisers which might support destroyer attacks.3 The change left the ships with two 6in and six 4in, the latter in the waist at upper deck level.
There was, however, a problem: the ships were lively, and the 6in gun, which was manually trained and laid, was heavy. In 1913 trials on board HMS Falmouth, which was larger and hence not as lively as an Arethusa, showed that the existing 6in mounting could not be laid and trained quickly enough to deal with the motion of the ship. The meta-centric height (in deep condition) in the new ships was therefore deliberately reduced. (and a squarer-section hull and deep bilge keels also adopted, to reduce motion). Goodall wrote that these changes could be made without detriment to stability because of the shift from coal and oil to oil fuel only, since in the deep condition the centre of gravity of the fuel was low rather than high. Much the same thing was done at this time in the design of the ‘R’ class battleships.4 Coventry Ordnance Works (COW) proposed a power-worked solution. The alternatives were the Vickers experimental N mount and the existing P.VI pedestal mounting. The Vickers mount seemed most promising.
Ships had little or no centralised fire control, which made sense for a ship expected to engage several destroyers more or less simultaneously. The anti-destroyer guns were grouped for a degree of control, and the ship had two standard 9ft rangefinders. After she destroyed the German raider Emden in 1914, HMAS Sydney turned in a report that the rangefinders became useless once fire was opened, hence that the new technique of ‘rangefinder control’ was out of the question.
In March 1913 DNC was told to work out how to replace the two single deck torpedo tubes with twin tubes.5 It would not be very expensive, but the ships had already expended their Board margins (for growth during construction), and the 5 tons involved might turn out to be the last straw. If it could not be accepted for the Arethusas, surely it should be accepted for the 1913/14 ships. The First Sea Lord accepted the loss of speed. He could imagine occasions when ‘these very fast ships could make night torpedo attacks on a battle squadron or division, which could not be avoided or resisted and which probably would not mean much risk to the smaller vessels’. The new cruisers were in effect super-destroyers, intended both to kill destroyers and to conduct their own torpedo attacks. The Royal Navy seems to have been unique at this time in seeing its light cruisers as torpedo craft. The idea apparently lapsed for a time, but it certainly returned strongly during the First World War.
Finally, in 1913 installation of single 3in HA (high angle, i.e. antiaircraft) guns was proposed for light cruisers. It was not approved until 1916. Galatea was completed with one 6pdr, Inconstant and Phaeton with one 3pdr, and Undaunted with one 1½pdr. The ships were completed with a single 0.303in Maxim (Vickers) machine gun, which was also standard in contemporary destroyers.
The first three ships entered service soon after war broke out in 1914. The broadside positions of the 4in guns were so wet that, at least in HMS Aurora, they were nearly useless. The ship’s captain interpreted his experience to mean that 4in guns were useless compared to 6in, but it seems fairer to say that low-lying guns necessarily nearly at the edge of the deck were much wetter than guns on the centreline. The position nearly at the deck-edge had other unfortunate consequences. Layers and trainers had to be strapped into their seats, because on some bearings they were actually over the sea. Shells striking the belt armour created splinters which, on one occasion on board HMS Arethusa in 1914, killed a gunlayer.6 DNO suggested building a light sponson under the guns. Although DNC protested that it would create more spray, it was added.
The Caroline or Calliope class
Eight more ships, slightly modified, were ordered under the 1913/14 programme as the Calliope class (later called the Caroline class). Compared to the Arethusa class, these ships had two more 4in guns. Two 4in were abreast forward of the bridge instead of a 6in gun; the two 6in were superimposed aft in ‘X’ and ‘Y’ positions. This unusual arrangement seems to have reflected the destroyer-killer logic: the ships would chase destroyers, against which their rapidly-firing (actually QF) 4in guns were their main weapons. Having four of them on the forecastle would provide more fire in the desired direction, and these guns would be dry in almost any weather. The 6in guns were intended to be used against enemy cruisers chasing the destroyer-killer. The ships were designed at about the same time that trials showed that existing 6in guns were unlikely to be very effective from such lively platforms.7 According to the DNC First World War cruiser history, an alternative armament of five (later six) 6in guns was proposed and rejected, but it does not appear in the Cover. Both versions showed 3,700-ton displacement (200 tons more than Arethusa) and 3in side protection carried 28ft further. Peace tanks were omitted, but it was expected (according to the DNC history) that more economical machinery would give a radius of action of 7,000nm on 900 tons of oil. This was wildly unrealistic.
HMS Caroline as completed in 1914, with four single 4in guns forward and two 6in aft, plus deck torpedo tubes as in Arethusa. (John R Dominy)
Caroline and Carysfort. Caroline is shown as in May 1917. Carysfort is shown as partially re-armed in 1918, with additional torpedo tubes in place of one of her waist 4in guns. Note her covered fire-control top, with (empty) searchlight platform below it, and the semaphore on the signal platform on her bridge structure. (John R Dominy)
Cordelia (1918) and Cleopatra (1919). Cordelia is as rearmed with four 6in guns, one 4in HA and eight deck torpedo tubes. Note the derrick for handling boats. Cleopatra shows new large gun shields for her 6in mountings. She is shown as she appeared in the Baltic fighting the Bolsheviks. (John R Dominy)
HMS Calliope is shown in 1916 (top) and in 1918. In the upper drawing the main difference from a Caroline is the absence of deck torpedo tubes. Note also the stowage of the motor cutter. The lower drawing shows her as rearmed with four single 6in guns, two 4in HA guns and two twin deck torpedo tubes in addition to her submerged tubes. (John R Dominy)
HMS Calliope is shown in 1925. She was refitted from November 1919 to March 1920 after a serious oil fuel fire. Her above-water torpedo tubes were removed, the after control simplified and two 2pdr (single pompoms) were added. The two 4in HA were replaced by 3in HA.
HMS Champion is shown in 1919, with a short ‘H’ mainmast to take her wireless antennas. Wartime and early post-war modifications include the deck torpedo tubes, the large shields for the 6in guns and the single 4in HA gun. Later she was given two single pompoms and a short pole mainmast. She retained the after control position shown.
Comus (1927) and Conquest (1928). Comus has had her after controls and extra torpedo tubes removed, a hood added to her rangefinder and some boats repositioned. Conquest is shown as leader of the 1st Submarine Flotilla. Surface ships were used to lead groups of submarines attached to the fleet because they could maintain communications and could scout for the submarines, much as light cruisers had been envisaged as the ‘eyes’ of pre-1914 destroyer flotillas. In 1925 the amidships 6in gun in Conquest was replaced by a deckhouse as shown. (John R Dominy)
Castor as completed in 1915, with her original gun battery of four 4in forward and two 6in on the centreline aft. She had no deck torpedo tubes. (John R Dominy)
Cambrian (1916) and Canterbury (1917). Cambrian is shown as she appeared on joining the Grand Fleet. Canterbury shows initial modifications: her after waist 4in guns have been replaced with torpedo tubes and she has a prominent searchlight platform aft. (John R Dominy)
The forecastle was carried further aft and the two forward waist guns moved up to the forecastle. Two ships, one building at Chatham (Calliope) and one at Hawthorn Leslie (Champion) were built with geared turbines and six small-tube boilers rather than the eight of the other ships. They had reduced power because their slower-turning screws were more efficient (37,500shp rather than 40,000shp in Calliope).8 The eight-boiler ships all had Parsons Impulse Reaction turbines except for Carysfort, which had Brown-Curtis. Champion had two rather than four shafts. They therefore needed no narrow forward funnel. Machinery spaces were materially shorter, and it was possible to enlarge the compartment between boiler rooms and engine rooms for submerged (rather than deck) torpedo tubes. Controller (Rear Admiral Archibald G H W Moore) much favoured this change, the only disadvantage being the existing problem (which he was sure would soon be solved) of discharge at high speed. The First Lord (Churchill) welcomed this development, which he had long espoused, and wanted it extended to the rest of the class – which was impossible. The change was particularly attractive because the twin deck tubes limited the firing arcs of the aftermost 4in guns. However, the chief advantage was better protection. It was accepted that in peacetime the upper deck tubes would enjoy a higher rate of fire, and that in wartime the upper deck tube might be better placed to take advantage of a fleeting opportunity because a submerged tube would require more preparation time and in view of the difficulty of communication between the firing officer and the tube. Also, although the tube itself might be better protected, it still depended on a vulnerable firing position on deck. The decision for below-deck tubes was firm by October 1913. Below-deck installations had seven torpedoes, upper deck ones ten.
The Carolines were essentially repeat Arethusas with a new main battery arrangement, including four 4in on the forecastle. HMS Cleopatra is shown, completing.
The changes added weight. The Board approved a 3,750-ton ship with an expected speed of 30kts. Raising two 4in guns and extending the forecastle added 17 tons, submerged tubes added 36 tons, oil fuel heating added 20 tons, an increase in galley coal added another 20 tons, and the Board decided that the margin in future ships should be 1 per cent rather than 20 tons (another 20 tons) – a total of 113 tons. Machinery changes added another 19 tons, and the 132 tons added since design would add 2in of draft and cost half a knot. The only way to get back to the Legend figures initially approved would be a drastic cut in fuel oil, which was unacceptable.
The 1914/15 programme was reduced to four light cruisers (Cambrian class), repeat versions of Calliope herself with two funnels and submerged torpedo tubes. All had six boilers but not the geared turbines of the Calliopes. It is not clear why the annual programme was cut, because when war broke out in 1914 the planned 1915/16 programme was eight cruisers.9 In fact only two ships were ordered during the autumn of 1914, initially as repeat Calliopes (Centaur and Concord).
For machinery, E-in-C asked for independent Parsons or Brown-Curtis turbines on four shafts with geared cruising turbines and small-tube boilers. Most firms offered alternatives. One was combined turbines, high-pressure (HP) turbines on the outer shafts exhausting to low-pressure (LP) on the inner shafts (which also had the geared cruising turbines). It offered about 6.5 per cent better economy, but each set of main engines would require a separate astern turbine, which would tend to cramp the restricted engine rooms. Another was all-geared Parsons turbines on two or four shafts. It was rejected pending experience with the geared turbines of HMS Calliope and HMS Champion and with destroyers. The third alternative, the German Fottinger hydraulic coupling (between turbines and shafts), was rejected on the grounds that its claimed efficiency was overstated, particularly at low power. The ships had Parsons Impulse Reaction turbines except for Canterbury (Brown-Curtis).
By this time it was clear that generator capacity (two 500-amp) was inadequate due to the introduction of 36in searchlights and installation of twenty-two electric radiators. The two generators in a Calliope could barely power two such searchlights, without the radiators or workshop pumps or 12½in ventilator fans. In April 1914 DEE wanted enough power for four such searchlights and for two 12½in fans in any new cruiser. His plea was rejected because no additional weight could be added.10 However, in 1915 it was decided that future light cruisers would have more powerful generators (two of 800 amps working at 105 volts), and provision of a third 500-amp generator was being considered for existing light cruisers and for ships under construction, for which provision of the larger generators would involve delay.
The Centaur class
Once war broke out, the two vital issues were gun and torpedo armament. Experience at Heligoland Bight convinced Captain Nicholson of HMS Aurora that his 4in guns were useless, hence that future light cruisers should be armed only with 6in guns.11 In November 1914 he sent a paper to this effect via an enthusiastic Commodore (T) Tyrwhitt of the Harwich Force (at that time the First Fleet Flotilla). He sketched an arrangement offering a total of five, all on the centreline, one gun firing forward and one right aft. The Controller (Rear Admiral F C T Tudor), who had lived through the Calliope design, was less than enthusiastic. These were special-purpose ships, intended to operate with and against destroyers and other light craft, and likely to have to fight several ships at the same time. They needed heavy ahead fire from several guns and the heavy astern fire provided in the design. Tudor was undoubtedly aware that his preference for a mixed armament might make it appear that he opposed single-calibre battleships (dreadnoughts) – Fisher had recently returned as First Sea Lord, and would hate to be reminded of the opposition to his great innovation of less than a decade earlier. Thus Tudor pointed out that he personally favoured one-calibre armament for ships intended to fight either single-ship or fleet actions, as that simplified both fire control and ammunition supply. Tudor saw Nicholson’s proposal as one of a series of cycles in cruiser design in which single large-calibre armament superseded mixed armament, the latest being the shift from the Bristol to the Birmingham classes. Each time design reverted back to mixed armament because it became obvious that a heavier gun could not shoot effectively from a lively cruiser. The 1913 tests of 6in gunnery aboard HMS Falmouth seemed to prove exactly that. Tudor felt that a 4in gun could be manoeuvred rapidly enough to make up for the ship’s motion, but a 6in could not. He suspected that the dividing line between effective and ineffective was half-way between, meaning a 5in or 60pdr gun. HMS Aurora had fought in fine weather, which was deceptive, with two of her six 4in out of action before the battle began, and the rest more or less quickly jammed. He had also observed the motions of such guns in bad weather but not in action. Tudor particularly disliked cutting the number of guns, hence the number of targets the ship could engage, and also halving her astern fire (it was necessary to cut down the deckhouse aft to accommodate the guns on the centreline).
HMS Centaur as flagship of Commodore (D) of the Atlantic Fleet. She was given an enlarged bridge structure to house the necessary staff, and No. 2 6in gun was landed. She and Concord could be distinguished from the very similar Caledon class by their clipper bows.
Centaur is shown in March 1925 after her 1924-5 refit at Rosyth to serve as flagship of the Commodore (D) commanding Atlantic Fleet destroyers (she recommissioned in April 1925). The 6in gun abaft the bridge structure was replaced by a ‘recreation’ deckhouse, and the bridge was greatly modified and enlarged, with the signal flag lockers enlarged and moved to the forecastle deck forward of the new deckhouse (which had a single semaphore atop it; note also the semaphore atop the bridge). The conning tower seems to have been removed during the same refit. The Centaurs were the first Royal Navy cruisers to have director control for their 6in guns; the secondary control position with two 36in searchlights atop it was added during the 1924-5 refit, and at the same time the lattice searchlight support structure just forward of the forward funnel was removed. Note the ‘elevation rails’ to prevent the 3in HA guns from firing into the ship’s structure. The ship retained her paravane fitting in her forefoot, but not the paravane gear. The torpedo spaces were located just abaft the after funnel on the lower deck. Centaur and her sister were sometimes incorrectly described as ex-Turkish. In fact light cruisers were included in the Turkish Vickers naval programme which produced the battleship Reshadieh (which became HMS Erin); Vickers built the two Centaurs. The company’s records show two designs for fast protected scouts (No. 771 of 27 January 1914 and No. 771A/B of 19 February 1914). Design 771B was relatively small at 3,558 tons (400ft pp, 423ft loa x 39ft 6in x 23ft 6in x 13ft 6in), and was expected to make 27kts on 22,000shp – which means that the Turkish ships, if they were ordered, did not provide the turbines used in the Centaurs. Armament would have been eight 4in/50 without shields, six 3pdr with light shields and two 21in deck tubes (probably singles). (A D Baker III)
What Tudor did not say was that, if the guns could be manoeuvred quickly enough, the new method of director firing would go a long way towards counteracting the ship’s motion, particularly when she was firing broadsides. Director firing in turn was most effective for a singlecalibre main armament – engaging a single target. The question, which was not raised again, was whether Tudor’s vision (doubtless not his alone) of a single cruiser fighting many destroyers at once was particularly realistic.
There was no question of altering ships under construction, but the two repeat Calliopes just ordered could be modified. As a compromise, Tudor offered to substitute a 6in gun for the pair of 4in on the forecastle forward of the bridge, to give an armament of three 6in and six 4in, with an ahead fire of one 6in and two 4in. The three 6in would give a powerful broadside for use against light cruisers in bad weather, when only broadside fire would be effective, and a large volume of fire against destroyers under favourable conditions.
Fisher and Churchill both strongly favoured the all-big-gun armament, and it was adopted for the two repeat Calliopes, HMS Centaur and HMS Concord.12 They retained the superimposed arrangement aft. The bridge was moved forward so that a second 6in could be inserted between it and the forefunnel, and a third 6in was inserted abaft the after funnel.13 As Nicholson had suggested, the heavy conning tower was eliminated to reduce weight in the bow due to the 6in gun. The 6in guns were modified to increase their elevation to 30° and hence their range. Beam was increased 6in, to 42ft. The new arrangement became the basis for the next class of light cruisers. Tudor’s comment that a 60pdr might be ideal (the 6in was a 100pdr) aroused Churchill’s interest. It seemed that six such guns could be accommodated. Nothing could be done for the moment because no such gun existed, and because a prototype would have to be built and tested. The prototype was ordered, emerging later as the 4.7in mounted in flotilla leaders.14 Both ships had six boilers and four shafts driven directly by Parsons Impulse Reaction turbines.
The issues for torpedo armament were means of control and loading arrangements. The torpedo directors in conning towers could rarely be used because of spray, so an alternative position was provided; by June 1915 this modification had already been approved for the ‘Towns’ and was about to be extended to the new light cruisers. Torpedo tactics were moving towards the use of ‘browning’ shots at longer ranges, and that in turn required dedicated rangefinders (typically a third rangefinder in a cruiser). It was placed on the same platform as the torpedo director.
It became obvious that upper deck torpedo tubes could not be reloaded at sea from below, hence that reloads were useless in battle. At a conference on board HMS Lion in June 1915, two alternatives were raised for the new light cruisers: either a second set of twin tubes could be added, or a box for reloads could be built on deck in line with each set of tubes. Either could be provided in an Arethusa, but the Calliopes lacked space for additional tubes.
The Calypso class
The war programme assembled in June 1915 included no light cruisers, although an appended note did call for ships for overseas service, which eventually became the Hawkins class (see below). All available slips may have been occupied by the six ships ordered in 1914. In November, however, a new six-ship programme was adopted. In December the Admiralty offered immediate contracts to four builders (Beardmore, Hawthorn Leslie, Scott and Vickers) provided they submitted firm fixed-price bids, and were prepared to accept a final Admiralty decision as to the amount to be paid. Cammell Laird built the ship planned initially for Beardmore. These ships were named Caledon, Calypso, Caradoc and Cassandra. In March 1916 it was decided to order another ship (Curacoa) from Pembroke Dockyard and a sixth (Ceres) by contract (ultimately to John Brown). Three more were soon ordered, from Fairfield, Swan Hunter, and Vickers (Caprice, later renamed Cardiff, Corsair, later renamed Coventry, and Curlew respectively).15
This Calypso class (1915/16 programme) was conceived as a slightly modified repeat Centaur with new geared-turbine machinery. Controller resisted changes, but a few crept in. The 6in guns were raised a foot above the deck, presumably for easier loading at higher elevation, and thirty rounds of ready-use ammunition per gun was provided on the upper deck or forecastle. These ships were also provided with two 3in HA guns each (250 rounds per gun plus fifty rounds of practice ammunition). Beam was increased 9in and the hull form slightly altered, the stem being modified to match that in the much larger Ocean-Going Cruiser (Hawkins class) then being designed, in hopes of reducing spray over the bow gun. Initially the anti-aircraft armament would have matched that of the earlier cruisers: two 3pdr Vickers QF guns with 300 rounds per gun and one 0.303in Maxim machine gun with both ship and field mountings. However, in February 1916 DNO proposed replacing the 3pdrs with 3in 20cwt HA guns (some of the additional weight would be saved by eliminating the usual pair of 3pdr saluting guns). The guns were characterised as both anti-aircraft and antisubmarine. The change (and others proposed by DNO) was rejected by Controller in the interest of speeding completion.
Above and below: HMS Calypso (Caledon class) as completed. Note the director below the spotting top, an improvement not made in earlier classes, and the two sets of twin deck torpedo tubes visible on this side.
Caledon as completed. (Henry R Dominy)
Caledon is shown in 1917 (top) and in 1923 (bottom). The 1917 view is as she appeared after a May 1917 refit. The 1923 view shows a rotating flying-off platform forward of No. 4 gun, the conning tower removed, the bridge enlarged (the compass platform, from which the ship would be conned following late wartime practice, was built up), and the after control and searchlight positions modified. She now had two rangefinders (fore and aft). The lines extending into the 6in shields carried director data to the dials on the mounts, which gunners matched to lay and train their guns. (John R Dominy)
Curacoa as in February 1918. This drawing was based on a detailed model plan prepared by the late Norman Ough in 1953 using original Admiralty as-fitted drawings. This version omits the ready-use racks for the 6in guns. The 15ft rangefinder at the fore end of the second superstructure platform was removed during the 1920s and the position plated in. Capetown and Carlisle initially had aircraft hangars built into their bridges, like that of Dauntless and Dragon. The name Curacoa recalls the capture of that Dutch island (now spelled Curaçao) in 1806. (A D Baker III)
HMS Caradoc in 1941 with limited initial war modifications. She has a Type 286 air-search radar atop her foremast and a Type 271 surface-search set aft. She has a 3in anti-aircraft gun abeam the gap between her two funnels, and the shields of two Oerlikons are visible abaft the shield of No. 4 6in gun. Another Oerlikon is visible on the bridge wing, behind a bulwark. In 1938 the ship had two 3in anti-aircraft guns and two single pompoms. The date written on the photograph (by the US Office of Naval Intelligence) is something of a puzzle, as it appears that the Oerlikons and radars were all installed during a refit at the New York Navy Yard, 21 October 1941 – 3 March 1942 (the ship received a total of five Oerlikons). Calypso was converted into a gunnery training ship in mid-1943.
The problem of firing submerged torpedo tubes at high speed had not, it turned out, been resolved; at a conference, representatives of HMS Vernon said that good running could not be guaranteed above 24.5kts, so the new Improved Centaur had to have above-water tubes with their centres not less than 10ft above water. Tubes on deck should be strong enough or roomy enough to resist splinters. Ideally they should be placed behind some form of armour, but that was impossible on weight grounds. It seemed best to fit two sets of double revolving ‘slack fit’ improved Arethusa-type tubes, ideally not exactly opposite each other.
Admiral Jellicoe, the Grand Fleet commander, had been pressing for two twin above-water tubes on each side as early as December 1915. He had little faith in any attempt to reload at sea, and with two sets of tubes on each side all torpedoes would be ready for immediate firing. Jellicoe pointed out that his Grand Fleet Battle Orders placed particular stress on the duty of light cruisers to attack the enemy battle line with torpedoes. ‘In attacking enemy torpedo craft or supporting our own torpedo boat destroyers, light cruisers are very likely to pass through positions from which torpedoes can be successfully fired at the enemy’s battle line.’ Once again, the line between light cruisers and destroyers (as torpedo craft) was clearly very thin. ‘The attack with torpedoes on the enemy’s battle line by light cruisers is the more important because many of our destroyers may be absent from the general action owing to shortage of fuel or bad weather encountered off the Northern Base, and the destroyer duties must then be performed by the light cruisers.’ Conversely, Jellicoe often demanded more destroyers on the grounds that he did not have enough light cruisers, and the demand for destroyers (which could be built much more quickly) presumably reduced building resources available for these destroyer-like light cruisers. By this time the Royal Navy accepted that long-range shots aimed at individual ships were unlikely to hit, given the long running time of the torpedoes and various inaccuracies. It also accepted that neither destroyers nor light cruisers were likely to get close enough to fire short-range aimed shots. Instead the Royal Navy emphasised ‘browning’ shots at groups of enemy ships. The more torpedoes fired, the better the chance of hitting. Just as British destroyers had pairs of twin tubes, Jellicoe wanted two twin tubes on each side for his cruisers. By March 1916 Controller had acceded; the operational Commander-in-Chief (C-in-C) should get what he needed, despite the effect of any changes. First Sea Lord (Admiral Jackson) approved the pair of twin tubes on each side. They added about 3 tons to the weight of a pair of tubes plus reloads. A proposed alternative using fixed tubes was rejected because they entailed too much additional structural weight, including extra length.
The Ceres class set the pattern for later British First World War cruisers, with their superfiring main battery providing more ahead fire. HMS Ceres is shown upon completion.
The ‘D’ (Danae) class
In about March 1916 DNC was asked to develop a new light cruiser for the programme planned for that May. The starting point seems to have been reports of new German light cruisers armed with ten or eleven 5.9in guns. DNC pointed out that the Germans were still following orthodox cruiser design practice, with guns on each broadside, so that the battery reported would give them a broadside of no more than six guns.16 That would outclass the new British cruisers. DNC added that it was almost impossible to produce a light cruiser combining a displacement much greater than that of a Centaur with the same speed without going to something like the new overseas cruiser Effingham. He presented his solution on 17 March 1916, adding another 6in gun.17 He could do so at minimum cost in additional length (and displacement) by making No. 2 gun superfiring and moving the bridge back towards the funnels. Two more centreline guns were mounted, as in the latest ‘C’ class, before and abaft the two funnels. In his view, the ‘C’ class, designed for 30kts, had reached the limiting speed of 29.5kts for such small ships. He had to accept much greater displacement in the Effingham to regain that speed, and for so large a ship the 6in gun was too small. The new sketch design traded about half a knot of speed for an additional gun. Moreover, superfiring meant that two guns could fire dead ahead. DNC thought the change would cost a few months of building time. On 20 March the Sea Lords approved the new design in principle for some of the cruisers of the May 1916 programme. In addition to the sixth 6in gun, the new design showed two 3pdr HA and one Maxim machine gun. As the design developed, No. 2 gun and bridge were moved 14ft further from the bow, and the bridge and conning tower (4in with 3in tube) raised. Although horsepower would match that of the Calypso class, revolutions would be reduced from 300rpm to 275rpm at a cost in weight and engine-room length (about 2ft). Some 2in armour was worked in aft. The design was approved in June 1916 (Board Stamp 30 June) with slightly more protection: magazine crowns were thickened to 1in, and gun shields were to provide protection from splinters as well as from spray.18 By this time, the design also showed triple rather than twin torpedo tubes.
Above and below: HMS Dauntless is shown in April 1930, little modified since the First World War. Note the considerable difference between her bridge and that of the ‘C’ class cruisers; hers is much closer to the ideal bridge developed late in the First World War, which provided officers on the compass platform the maximum view on the basis of which to conn the ship.
Dauntless as completed in February 1919, with a hangar built into her bridge structure (it was never used). Dragon had an identical hangar. The section of the flying-off platform which would normally lie atop ‘B’ gun could be folded back over the fixed portion. It was removed in 1920, and the fixed part used to mount two 24in searchlights (the starboard light was about 4ft abaft the port). The hangar face could be closed by doors, but the sides were open. The aircraft was stowed ready for take-off, its tail resting on a railed support within the narrower extension of the hangar. An aircraft loading (and wreck recovery) boom could be stepped on the forward port corner of the hangar. The captain’s sea cabin was to starboard and the charthouse to port on the open bridge. The X-crossed panels on the sides of the open bridge and the weapons control station aft represent splinter protection mats, which were removed during the 1920 refit. Note that there was a steering wheel and engine order station on the bridge, to starboard of the compass platform. By 1930 Dauntless and her sisters Danae and Dragon had three 4in HA in place of the two 3in mounts, while the two single pompoms were moved to new platforms abreast the bridge structure. The ‘D’ class was the only Royal Navy steam-turbine light cruiser class designed with two rather than four shafts (Undaunted also had two shafts). (A D Baker III)
A slightly later attempt to cut weight by reducing ammunition from 200 to 150 rounds per gun was rejected on the grounds that ‘the new method of ranging will lead to increased expenditure by the main armament. These ships will also be able to open fire at very long ranges as they will have 30° mountings and Director firing; and more opportunities occur for firing when using Director.’ DNO offered only that the usual sixteen practice rounds could be included in the 200 rounds per gun.
By May 1916 the new ships were designated the ‘D’ class, three being ordered in September 1916. Three more were ordered in July 1917, and another five in March 1918 (four were cancelled at the end of the war). Of this class, Dauntless and Dragon were fitted to carry an aircraft.
It was decided not to modify the six ‘C’ class ships ordered in December and March 1916, so DNC asked whether the last three ships (ordered in April 1916) should be modified. Proposed modifications were substitution of 3in HA for 3pdrs (12 tons), substitution of armour for spray shields on 6in guns (23 ¾ tons plus increased beam and hull weight), and modified ammunition supply to the 6in guns.
The Improved Calypso class
With the ‘D’ class design proceeding in April 1916, Controller planned that they should embody all improvements, and that the new ‘C’ class cruisers just ordered should be repeat Calypsos. However, he was well aware of the value of superfiring mounts, which had just been arranged for in new destroyer leaders. Could the same thing be done in a ‘C’ class hull, moving bridges further aft? On 4 May DNC submitted just such a plan – ‘the improvement is so marked that it is thought to be well worth carrying out.’ The space between boiler room and engine room was reduced by 18ft, the boilers being moved aft this distance. Beam was increased by 9in, at a cost in weight and thus in speed. The other proposed changes were not adopted. Controller agreed that the improvement in bow fire and in the position of bridge and conning tower were so great that they were well worth a slight loss of smooth-water speed. The First Sea Lord and the First Lord of the Admiralty (now Arthur J Balfour) initialled the change on 6 May 1916. The one change that was carried out was substitution of 3in HA for 2pdrs, which was justified by the need for more powerful anti-aircraft weapons. It was urgently requested by the Grand Fleet, and had already been approved for Centaur and Concord on that basis.
The question was now which of the Calypso class under construction could be modified with minimum delay. A naval constructor was assigned to visit the yards to see what could be done. He concluded that the first four were all too far along, even the least advanced Calypso. That left the five most recently ordered ships, all of which were completed with superfiring guns forward. They were described as the Improved Calypso class. They had two-shaft geared Brown-Curtis turbines. According to the report of gun trials by Ceres, the first of this modified ‘C’ class, the absence of vibration in way of the bridge was noticeable, appreciably less than in Champion with similar machinery. It was attributed to the position further aft and to the absence of bridge wings, ‘which readily take up any vibration in the remainder of the structure; and to the solidity of the bridge structure to which special attention was paid in this ship’. The director control tower (DCT) vibrated worse than the control top immediately above it, probably because the former was overhung forward of the mast. The thick side plating and the shell plating were both faired into the skin of the ship to leave a smooth surface, spray being due almost entirely to the paravane chains.
Another eight light cruisers were ordered in June–July 1917. Plans may initially have called for three repeat ‘C’ class and three repeat ‘D’ class. At one point six of the eight were to have been ‘D’ class modified with greater endurance for overseas service, but instead the order was split between three ‘D’ class and five ‘C’ class. Both groups were given raised (‘trawler’) bows for better sea-keeping. All of the repeat ‘C’ class had geared Brown-Curtis turbines except for Curlew, which had Parsons. Five more ‘D’ class cruisers were ordered in March 1918, identical to the 1917 ships except for 6in more beam.
In the autumn of 1916 the Board decided that six of the eight light cruisers of the November 1916 programme should have a 7,000nm radius of action (compared to 5,000nm for a ‘D’ at 13.5–14.5kts) for use on foreign stations (unlike the Hawkins class, however, they were not to burn coal for convenience in foreign ports).19 The Controller issued instructions in a Minute dated 27 September 1916. On 24 November DNC submitted a design differing from a standard ‘D’ class cruiser only in having greater displacement to carry more oil. Two weeks later the Controller (Rear Admiral Tudor) directed DNC to develop full working drawings as soon as possible, so that orders could be placed. DNC increased length from 445ft to 460ft, buying 16ft more (for fuel) between engines and boilers, but limiting increased length by shortening the part of the ship forward of the foremost fuel tanks. He also provided peace tanks between the platform and lower decks (capacity 100 tons), for a total capacity of 1,325 tons to give the required radius at 13–14kts. The design showed the recently-adopted triple torpedo tubes. Machinery was 10 tons heavier than in a ‘D’, presumably mainly due to longer propeller shafts. Deep displacement was given as 5,250 tons, about 600 tons more than that of a ‘D’ class cruiser as completed. The loss of speed was not indicated. Jellicoe, now First Sea Lord, approved the design on 20 December (it received the Board Stamp on 3 January), but no orders were given, and the design died.
As recently-appointed First Sea Lord, Admiral Jellicoe was very much concerned with the wetness of British cruisers and destroyers, having operated with them in rough weather. On 9 December 1916 he asked Controller to look into a design with the bridge moved further back by interchanging bridge and mast with No. 3 gun, leaving a gap between forecastle and bridge (he was interested in a similar scheme for destroyers). He was probably unaware of how far back the bridges of the ships with superfiring guns were: 136ft in a modified ‘C’ and 132ft in a ‘D’, compared to 92ft in a Calypso. DNC pointed out that he would have to add 7ft more length, because it was undesirable to move Nos. 1 and 2 guns closer to the bow. That would entail greater beam and hull depth (for strength) and displacement, and more length might be needed because the space between the end of the extended forecastle (carrying the bridge) might be too limited to accommodate boats, four triple torpedo tubes, and two 3in HA as then to be carried by a ‘D’ class cruiser. No. 2 gun would need an additional blast screen to protect it from No. 3, and the screen in turn would limit the elevation of No. 3 gun on extreme forward bearings. Raising No. 2 gun would enlarge the target represented by the ship. The idea died.
Bridge Design
In March 1917 a special committee under Commodore C F Lambert was convened on board HMS Southampton at Rosyth to decide future cruiser bridge policy on the basis of wartime experience. The discussion helped shape the bridges of post-war British cruisers. All present agreed that it was not necessary for the bridge wings to extend all the way from side to side. However, in that case the view of signal lights might be blanked off by the ship’s broad forefunnel. There was strong interest (as in destroyer bridges) in streamlining the superstructure and also in shaping it to resist the impact of heavy waves. The bridge should be as far aft as possible, limited only by the position of the tripod mast, which had to be forward of the boiler room. The captain, navigator and officer of the watch would occupy a navigational platform incorporating the compass platform, with the best possible view, with the captain on the compass platform. By this time standard British practice was for officers on an open compass platform to pass steering orders to a helmsman below them. Ideally the chart house would be directly below the navigational platform, with a steering position built onto its fore end, with only wheel fittings and room for a helmsman to stand. To keep the navigational platform as clear as possible, gunnery and torpedo controls and signalling should be moved away. Ideally the bridge should incorporate a weather-proof and splinter-proof compass platform and a weatherproof position for the chart house, signal house and officers’ and captain’s sea cabins. Weight could be made available by eliminating the more-or-less useless existing conning tower. The space below the chart house would be divided into a signal house and a captain’s cabin. It should be possible to enter the bridge from the main deck in foul weather. The latest ‘C’ class bridge embodied most of these ideas, but it had proven impossible to find other locations for fire controls.20 The ‘C’ class bridge was being fitted to all light cruisers under construction.
Existing steering positions were protected by 3in HT plating, but to avoid disturbing the magnetic compass, the upper bridge (and compass platform) was protected by wire mattresses. Weight saved by eliminating the conning tower would go into these mattresses.
In this 1930 view, Calypso shows her new block bridge structure, similar in concept to the bridges then being built for new cruisers. The helmsman on the level below the compass platform has only a few deadlights rather than the previous row of windows, because the ship was conned from the compass platform. These ships were excluded from early plans for anti-aircraft conversion because they would have required extra design and construction work due to their lack of superfiring guns forward.
Bridge details of HMS Caradoc (Caledon class), probably in the 1930s.
Wartime Rearmament
The changes in policy which produced the succession of classes affected the existing ships. Because they were so small, standard additions of weight had large consequences. From the Centaur class on, ships were completed with tripod foremasts supporting spotting tops and directors. Similar facilities were proposed for the ‘Towns’ and the earlier light cruisers, but the ships were badly needed, and it was considered unwise to withdraw them for such extensive work. As a stopgap they received lightweight directors or even had one gun designated the directing gun. By August 1916 tripods had been tentatively approved for the Arethusas (they were fitted to all ships after a successful inclining experiment in HMS Penelope in 1917). Ships were also fitted to carry and drop Leon drifting oscillating mines (it was believed that the Germans planned to drop such drifting mines in the path of the British fleet).
In September 1916 a simplified system, not involving a tripod, was approved for HMS Cleopatra. A simple director was installed in her fore top. It was described as a complete director sight as far as training was concerned; the guns would be laid for elevation by a pointer from the sights, and fired from the sights. In this way advantage could be taken of the roll to gain range for the guns. When the tripod issue was revived in 1916, it was pointed out that in light condition the ships would have to have water ballast. The first ship so fitted, HMS Caroline, was inclined in March 1917. Weights proved somewhat greater than expected. More generally, by mid-1917 the weight situation was so bad that nothing could be added unless compensating weight was landed. That issue was raised when DTM asked for remote searchlight control (rangefinders could not be used when searchlights were on because they would blind the operators).
In March 1916 Admiral Jellicoe proposed adding two more twin tubes at the expense of the after 4in on each side (and eliminating the deck reloads). In the two modified ships (Calliope and Champion) stability problems might preclude the twin tubes, but Jellicoe hoped that single deck tubes could be fitted. Alternatively, the addition of twin tubes might be compensated for by reducing coal stowage (culinary, on the upper deck) and landing some fittings. DNC agreed (in October) that the additional weight would be limited, but in view of the many additions already made to the ships, he wanted a constructor to visit Scapa Flow to discuss what could be done. Unfortunately most of the weights added since commissioning had been high in the ship.21 Director of Naval Equipment (DNE) suggested approving C-in-C’s proposal for the Arethusa and Calliope classes (except for the up-gunned Centaur and Concord). By this time the proposal was to add the tubes to the Arethusa class and to add them to the ‘C’ class in place of the after 4in gun on each side. DNC agreed to these changes except for ships with submerged tubes, in which other weights might have to be surrendered. For the two up-gunned ships with submerged tubes, extensive blast screens would be needed if deck tubes were fitted.
HMS Conquest shows typical war modifications; by the time this photograph was taken, she no longer had a flying-off platform. The forecastle 4in guns was replaced by a single 6in on the centreline in 1916–17. When the conning tower was removed and the tripod stepped, the remaining pair of 4in guns in the waist gave way to a fourth 6in, abaft the funnel. Note that by this time she had reverted to a single pair of deck torpedo tubes on each side. Ships were initially fitted with a single 13pdr Royal Horse Artillery anti-aircraft gun. Later it was replaced. Conquest had one 4in anti-aircraft gun and two single 2pdr pompoms. Others in the class varied. Caroline, Carysfort and Comus each had two 3in/20 cwt; Cleopatra had two 4in and two single pompoms; and Cordelia had one 4in and no pompoms. This photograph shows the ship without No. 2 6in gun, which was replaced by a deckhouse in 1924.
HMS Cambrian post-war, showing her all-6in main battery and her tripod foremast.
HMS Caroline with wartime changes, including the shift to an all-6in main battery. (Josef Straczek)
In connection with the proposal to replace 4in guns with additional deck tubes, Jellicoe asked for proposals to save topweight. The list was headed by the comment that it was pointless to leave two 4in guns on each side, whose value would be negligible compared to 6in guns. Better to replace them with another 6in gun. Jellicoe rejected the idea on the grounds that even if adequate gun support could be arranged it would be impossible to find sufficient compensating weight.
In May 1916 Admiral Jellicoe asked that the two foremost 4in guns be replaced by a third 6in gun on board the mixed-battery ‘C’ class cruisers. Conquest and Cambrian were modified in advance of Board approval (June 1916), and work was done on a not-to-delay basis. The Board also ordered that a 4in HA gun replace the existing 3pdr Vickers gun; ultimately two 4in HA guns would be installed. The Board rejected Jellicoe’s proposal to save weight by removing the conning tower and its tube (in Conquest the 6in gun had been added without interfering with the conning tower). Deck reloads would be carried, the ships retaining their original pair of twin deck torpedo tubes (except for those with submerged tubes). At about the same time deck reloads and 4in HA guns were authorised for the Arethusas.
Before a decision was made, Commodore (T) (Tyrwhitt of the Harwich Force) was asked his views on these ships under his command, as their role was rather different from that of similar cruisers in other Light Cruiser Squadrons. In November he heartily agreed with the idea of adding 6in guns; in his view, the ships were lamentably underarmed with torpedoes. He also repeated his earlier argument for more 6in guns. Jellicoe agreed with Tyrwhitt (and said that he had opposed the mixed batteries when the ships were being designed) but feared that the work involved in rearmament would take the ships out of action for too long. Nothing was done. However, the additional pair of twin tubes on each side was ordered installed in place of the after 4in gun in all mixedbattery ‘C’ class cruisers, including those with underwater torpedo tubes. Manufacture of the tubes was approved late in 1916, with first deliveries in December. By this time it was accepted that underwater tubes were unsuited to fast light cruisers, but they could not be surrendered from a stability point of view.
The Board later reversed itself regarding the Caroline and Cambrian classes, probably at the instance of Tyrwhitt. In a note dated 2 September 1917 he summarised wartime lessons of his force, which often fought German light forces in the North Sea. In most cases he felt a need for more ahead fire; minor actions ‘invariably resulted in a chase’. The new Ceres class (two superimposed guns forward) were an improvement, but surely more could be done. Surely a ship could have two guns on the beam in addition to one on the centreline. The resulting ship could have a five-gun broadside and could fire four guns ahead and astern on most bearings. Tyrwhitt also rejected submerged torpedo tubes (which had been dropped in light cruisers).
Tyrwhitt’s letter revived the earlier idea of replacing 4in guns with a pair of 6in guns on the sides of the ship. In about September 1917 DNC approved the idea. The C-in-C of the Grand Fleet, Admiral Beatty, had already endorsed the idea of adding 6in guns to the light cruisers at a 15 August 1917 conference with the Third Sea Lord. The work was justified by the heavy armament of new German light cruisers, the same issue which had led to the design of the ‘D’ class. As initially proposed, the guns could be mounted in an Arethusa at the expense of the two forward pairs of 4in guns, and in ‘C’ class cruisers at the expense of these guns plus moving the 4in HA gun to a lower position (the quarterdeck) plus elimination of the conning tower. DNO pointed out that 6in guns on the sides would create considerable blast on some bearings. He was also less than enthusiastic about available numbers of spare guns for rearmament. Further complicating the issue was a decision by the Grand Fleet Operations Committee that all light cruisers should carry fighter aircraft. Normally they were stowed on one side of the forecastle, fouling the position in which Tyrwhitt hoped to put a 6in gun. Several of those commenting on Tyrwhitt’s proposals suggested that they really applied to new construction. The outcome (see below) was the design of the ‘E’ class.
In December 1917 DNO proposed rearming the Arethusas as Tyrwhitt proposed, with five 6in (two on the forecastle abaft the existing gun, one superfiring over the existing after gun, the 4in HA gun being moved to the forecastle deck above the torpedo tubes), giving a broadside of four guns. Compared to DNC’s recent proposal, DNO offered an additional centreline 6in gun aft instead of the two 4in DNC would have retained. DNO offered only one additional 6in firing right aft, and to provide it he would have to land or relocate the after torpedo tubes. It also turned out that blast from No. 3 gun would affect the crews in any position further forward (although crew shelters could be provided, as in the Caledon and Danae [‘D’] Classes). They were too important to eliminate. DNC was asked to submit further designs after a conference in January 1918. In one version, the three forward 6in were retained and an additional 6in gun was mounted on the centreline aft, just forward of the original after 6in gun, the after sets of twin torpedo tubes and all 4in guns being landed. The alternative was a superfiring gun forward, the after guns being as in the first alternative. As weight compensation, the conning tower and tube would be removed altogether (in mid-December 1917 C-in-C Grand Fleet agreed to the removal of all light cruiser conning towers). There was very little space between the forward 6in gun and the tripod foremast. The mast could be moved aft a few feet (otherwise its fore leg would pass through the charthouse). Even so, there was very little space between No. 2 gun and the chart-house. A drawing of the proposed bridge structure shows the compass platform built out over the forward end of the chart house, its own forward end supported by a strut extending up from No. 2 shield. Controller preferred this arrangement, even though it precluded the desired flying-off platform for a fighter. Before agreeing to rearmament, C-in-C Grand Fleet wanted to know the earliest date a ship could be taken in hand and whether rearmament could be done at the ships’ normal refit ports. He also wanted to know how long rearmament would take. Of the seven ships in the class, HMS Undaunted was refitting as a minelayer. The others were due for refits which would begin from 27 April up to about July 1918. Work would probably take five weeks, once material had been received. However, discussion of arrangement (for example, the position of HA guns, and whether the ships would have one 4in or two 3in HA) continued through the summer of 1918.
In July, HMS Penelope received an interim refit in which an additional 6in gun was mounted aft (making three 6in in all), but the superfiring structure was not built. She surrendered two (of six) 4in low-angle (LA) guns and her 4in HA gun and added two 3in HA guns. The rest of the 4in would go when she received her fourth 6in gun. She conducted gunnery trials on 16 August 1918 (and again, defects having been made good, on 19 October). Inconstant was next, and in September 1918 Phaeton was ordered modified in the same way during her upcoming refit. Work continued after the Armistice, Galatea being modified during a December 1918 refit. Royalist may also have been refitted.
Initially the Board favoured a four-gun armament for the mixed-battery ‘C’ class, of which two would be mounted forward, one superfiring. ‘C’ class stability was sufficiently tender that not even the lightweight conning tower could be added in this case. A new position was settled at an August 1917 conference: a fourth 6in gun replaced the 4in HA gun previously mounted on a bandstand (to clear an engine-room ventilator) atop the casing. The two remaining 4in guns on the forecastle were converted to HA. After arguments were raised against this arrangement (initially by the Captain of HMS Constance), it was reconsidered (in April 1918) and changed to retaining the existing single 4in HA gun and mounting the fourth 6in gun further aft, just forward of the after control position. Cleopatra, the first ship rearmed, was apparently the only one to have the two 4in HA guns. The conning tower was removed (a 1in splinter-proof tube was substituted). The big refit also involved replacing the earlier 15° elevation mounts with 20° mounts, and there was some difficulty over the supply of the modified gun mounts, fourteen of which had been ordered from Coventry Ordnance Works. Given the problem, DNO proposed simply to replace the three 6in on board the first four ships during their ordinary refits, on the theory that they could not be spared for long refits in any case, and this work would have to be done as part of the larger refit planned. All ships, including those with submerged tubes, would be armed with a total of eight 21in torpedo tubes. Topweight was a problem; a telegram to HMS Calliope (dated 2 April 1918) approved retention of the two forecastle 4in guns (as HA) only if the planned amidships 6in gun was not fitted and if the 4in HA gun and its bandstand were landed. The two 4in guns were to be removed as soon as the fourth 6in mounting was fitted. At this time C-in-C Grand Fleet was unwilling to surrender ships for the five-week refit involved, but Tyrwhitt (now Rear Admiral Harwich Force) was anxious to have the extra gun.
Also in November 1917 it was decided to provide ships of the Dover Patrol (except destroyers) with two single 2pdr pompoms to defend against German motor attack boats (CMBs and DCBs, the latter Distance Controlled [i.e. remote-controlled] Boats used off the Belgian coast). Cruisers involved were Centaur, Cleopatra, Concord, Carysfort, Conquest, Canterbury, Penelope, Aurora and Undaunted; this addition was also planned for the leaders Shakespeare and Valkyrie.
In July 1918 the Captain of HMS Conquest raised another point. As rearmed the ships would have no guns suited to engaging surfaced U-boats, other than the bow 6in, which he considered too slow-firing (no gun would have much time to fire before a U-boat surprised on the surface dove). The two 4in on the forecastle would have been ideal, but under the revised rearmament scheme they were gone. Rear Admiral Harwich Force proposed 3in guns on the forecastle as anti-submarine weapons in addition to the 4in HA gun aft. DNO much liked the idea, suggesting simply substituting the 3in guns forward (where they could bear on submarines) for the 4in HA aft. For all-round fire the ends of the bridge would be clipped off (as in HMS Cleopatra, the only ship with 4in guns in these positions). The deck would be stiffened for anti-aircraft fire. Vice Admiral Light Cruiser Force (of the Grand Fleet) recalled that in May the idea of substituting two 3in for one 4in HA had been accepted in capital ships; it was time to extend it to the cruisers. The single 4in was clearly superior for attacking aircraft at considerable altitude (interpreted as offensive anti-aircraft fire). However, fighters operating with the fleet now dominated the offensive anti-aircraft role. At long range the 6in gun (20° elevation) could be effective against aircraft. When attacking a ship aircraft had to descend to altitudes at which 3in guns would be an effective defence. Also, only HA guns could fire star shell, essential for night fighting. As such they needed good ahead bearings – which the amidships 4in lacked. He therefore agreed with Tyrwhitt, but he wanted the 3in guns on the forecastle to have HA mountings. They should replace the 4in amidships. C-in-C Grand Fleet added that the recent experience of HMS Galatea under air attack showed that ahead fire was essential for engaging aircraft. HMS Caroline seems to have been the first ship rearmed with 3in rather than 4in anti-aircraft guns (in November 1918).
Some ships became minelayers. In January 1917 the First Sea Lord asked that the ‘C’ class be considered for conversion, but the Auroras were actually better: Penelope could carry 100 mines. Of the ‘C’ class, removing a 6in gun from a Caledon would allow her to carry fifty mines, and a Curacoa could carry eighty. Aurora was the first to be converted (while under refit, completed May 1917). Ultimately all seven surviving ships were fitted for minelaying. Ships could carry seventy or seventy-four mines. Mines were laid by Aurora (212), Galatea (220), Inconstant (370), Penelope (210), Phaeton (358) and Royalist (1,183), but not by Undaunted. On 31 December 1918 removal of minelaying fittings was ordered; when queried by the Naval Staff in November 1919 the responsible Constructor did not know whether that had actually been done.
At the end of the war ships were so overweight that when refrigerating machinery (for magazines) was wanted for service in the tropics, DNC said they had to surrender either a 6in gun or a pair of twin torpedo tubes. The choice was No. 2 gun (in 1923). Probably this was done only in HMS Conquest.
Aircraft
Interest in flying-off platforms carrying fleet fighters dated from at least 1916, when Director Air Service (DAS) proposed fitting a landing and taking-off platform to ‘C’ class cruisers.22 DNC rejected what he called ‘a forecastle deck above the forecastle deck’, but suggested a temporary platform which could be unshipped; he preferred the hydroplane lighter then being designed for destroyers. The idea survived because fleet guns were unlikely to destroy German reconnaissance Zeppelins quickly enough, or at sufficient range. The British were almost certainly aware that the Germans had escaped from what amount to a trap in August 1916 because their Zeppelins spotted British warships (actually not the Grand Fleet itself). At a 15 August 1917 conference, C-in-C Grand Fleet asked that one light cruiser in each squadron have a flying-off deck for an anti-Zeppelin machine. He selected Caledon (1st LCS), Dublin (2nd LCS), Yarmouth (3rd LCS) and Cassandra (6th LCS), Yarmouth being the prototype. Additional light cruisers would be converted if the idea proved successful. Because it was not in the ‘A-K line’ in the van of the fleet, 4th Light Cruiser Squadron would not have any of its ships fitted. Late in October 1917 the Third Sea Lord’s Committee on flying-off platforms chose a pair of troughs (with a platform between them) along which the aircraft’s wheels could run. Further ships were also fitted.23 Separate drawings were prepared for the light cruisers (Caroline, Cambrian, Aurora, Chatham and Weymouth classes); for Birmingham and Lowestoft; and for Birkenhead and Chester. Except for Birmingham, Birkenhead and Chester, the forward end of the platform had to be held up by a support fixed to the forward 6in gun shield (as already fitted in Yarmouth and Cordelia). Bristol and earlier light cruiser classes were not to be fitted. Given the critical weight situation, the captain of HMS Constance (scheduled to receive a flying-off platform) suggested that the aircraft would have to be landed before a fourth 6in gun was mounted.24 The Grand Fleet would lose aircraft from five of its twenty-four light cruisers. A conference in April 1918 between the Third Sea Lord and representatives of the departments agreed that it was most unwise for these ships to have flying-off arrangements plus the extra gun, and that the C-in-C Grand Fleet had to be asked about the problem. Erroneous references in correspondence about Constance to a revolving platform indicate that it was considered a solution to the problem of a platform built out above No. 1 gun.
Yarmouth had the prototype cruiser flying-off platform. Other major wartime modifications included the tripod foremast carrying an enlarged spotting top with a director above it (fitted in 1917 to all but Falmouth, lost on 19 August 1916 after being torpedoed by two different U-boats), a 3in anti-aircraft gun between the second and third funnels, and searchlight control platforms aft. Note also the splinter mattresses on the bridge. Additional structure was added abaft the original bridgework. After the First World War Yarmouth had her after 6in gun removed and replaced by quarterdeck deckhouses.
Ships with superfiring guns forward required something far more elaborate, because the platform had to clear both guns and the hangar was built under a raised bridge. HMS Carlisle was the first ship so fitted. Rear Admiral Harwich Force commented in October 1918 that ‘these magnificent ships are completely ruined by their present form of bridge, which completely disorganises the control of the ship and renders the life of the personnel one of misery’. This was despite the great advantage of her ‘trawler’ bow; in December 1918 she ran into a strong SSW gale at 16-24kts for eleven hours. Despite the short steep sea running, she shipped no water, and her mess decks were dry except for a few minor leaks. However, because the hangar raised it so high, the fore bridge was close under the fore top, hence extremely drafty and cold. ‘Everything was blown about in a most distressing fashion. The noise of the wind round the mast and rigging makes the efficient use of voice-pipes and telephones in the Fore Control position most difficult.’ Capetown was similarly fitted, as were Dragon and Dauntless. By this time removal of the awkward hangar had already been approved (for the three Carlisle class and ‘D’ class cruisers under construction), the fixed flying-off platform to be replaced by a revolving one on the fore side of the after control position (which had to be moved about 9ft aft). A new bridge would be installed, similar to that in non-platform ‘D’ class cruisers. Unfortunately for Carlisle, she was urgently needed on the China Station, and there was no time to rebuild her bridge before she left (there was hope that it could be done at Hong Kong). Ironically, she was not expected to carry any aircraft while on the China Station. Caledon, Delhi, Despatch, Dunedin and Durban were all fitted with a revolving flying-off platform aft in 1919. By 1928 only Caledon retained the platform.
Flying-off ended with the end of the First World War, although the unwieldy hangar-platform arrangements survived into the 1920s (but were not used). When it was revived about 1926, only the two new ‘E’ class cruisers and Caledon had revolving flying-off platforms, those on board the two larger ships surviving to 1935–6. In all, thirty-two light cruisers had some type of flying-off platform.25
The Emerald class
The final wartime light cruiser, the ‘E’ class, apparently began as a result of the comments on existing light cruisers by Commodore (T) Tyrwhitt of the Harwich Force. At about the same time (the week of 20 October 1917) Controller initiated a study of increasing the speed of light cruisers. In November 1917 Controller (Rear Admiral Lionel Halsey) asked DNC and E-in-C for a completely new cruiser design, with greater speed combined with gun power and if possible three guns capable of firing ahead: ‘It appears to me that it would be possible to retain the foremost superimposed gun and to take away the foremost forecastle gun.’26 Two sketch designs were completed in December 1917.27 The first was Tyrwhitt’s ship, with four 6in guns (presumably three on the forecastle), using 60,000shp to reach 31kts deeply loaded on 4,500 tons. As DNC had written in connection with the ‘D’ class, the alternative was a much larger ship, a 510-footer (six 6in guns) using 80,000shp to make 32.75kts deeply loaded (34kts light). Both designs used lightweight (destroyer leader) machinery (note that a ‘D’ class cruiser needed almost as much weight as Design A for two-thirds the power). The larger ship offered the standard ammunition stowage (200 rounds per gun) rather than the 150 rounds of the smaller design, and it also offered better protection. It became the basis for further development. Although the design was incomplete, three ships were ordered in March 1918, at the same time as the improved repeat ‘D’ class. One, Euphrates, was cancelled after the end of the war.
Unfortunately no drawing of either alternative has survived, but it seems likely that, like Design A, Design B included two beam guns. Even if they were well abaft the bridge, the ship would have three guns firing over nearly all forward arcs, except for dead ahead. The fleet wanted more space between the machinery spaces, presumably to reduce vulnerability to single hits, and it also wanted better ammunition arrangements. A design was circulated in March 1918. The armament was considered satisfactory, but not the protection. Diagrams of new German light cruisers in the intelligence handbook showed a protective deck over their vitals, but the new British light cruisers had only a protective upper deck (i.e. the deck below forecastle deck level) and in the new ship even that did not extend over the boilers. A British shell hitting the side armour of a German light cruiser would burst, its fragments kept out of the vitals by the deck. Fragments from a German shell hitting the high side armour of the new cruiser would encounter no deck at all, or else would likely pass under the protective upper deck. In 1918 the British were finding it difficult to design a 6in shell which would defeat German-style protection. Why couldn’t the new cruiser be as well protected? It seemed that the existing arrangement actually increased the chance that a shell would burst in the ship’s vitals.
Naval Intelligence was forced to admit that deck thickness was the most difficult of all data to obtain. Its best hope was that the survivors of the German cruiser Breslau, recently sunk in the Mediterranean, would provide information, but their passage (by convoy) to England had been delayed, and there was no hope of obtaining information in time. Intelligence was sure that the Germans had rearmed some cruisers with seven 5.9in guns each, which made the new more heavily-armed British cruiser more important.28
DNC could do nothing about protection, because it was really incidental to the structural designs of all the existing fast light oil-burning cruisers. High speed demanded great length, and to minimise structural weight he had integrated armour into the hull – conversely, where there was no hull steel there was no protection. A German-style deck lower in the ship would contribute almost nothing to strength (girder strength depended mainly on the uppermost continuous deck and on the keel, with contributions from the ship’s side plating). He could provide vertical armour over their boilers, but the boilers were so large that it was impossible to cover them with an effective armour deck. For that matter, eliminating side armour was unwise because in that case the waterline could be riddled and stability lost in battle. He considered the cruisers virtually large destroyers, which had to depend on speed for protection. He soon repeated this view during discussions of what became the ‘County’ class heavy cruisers. Moreover, very little could be changed, because in hopes of getting ships rapidly DNC had promised the builders information as early as possible, probably well before the design had formally been approved. Some information had already been supplied, and any basic change would require an entirely new design. DNC’s comments were dated 30 March 1918. First Sea Lord accepted these arguments (about 10 April), but wanted the issue kept in mind for future ships.
Emerald in March 1926, as completed, with a rotating flying-off platform and triple torpedo tubes. The triples were replaced by quadruple tubes during a 1928–9 refit, with maintenance sponsons added outboard, and with ‘torpedo shelter’ decks added over the mounts. A ‘native hut’ was added abaft the second funnel (atop the engine room ventilation trunk). During a refit at Chatham in 1934 the funnels were raised, the flying-off platform replaced by a 44ft catapult, the mainmast moved to forward of the second funnel, an aircraft and boat crane added abaft the catapult, the 15ft rangefinder amidships replaced on a larger platform by a Mk I HA director for the 4in guns, and the 30ft gig to starboard aft moved to the port side (replacing a 30ft cutter) and replaced by a 36ft motor cutter. A depth-charge rack was added to port at the stern, but no Asdic was fitted. The elevation drawing omits the ready-use stowage racks for 6in ammunition (they appear as small rectangles in the plan view). Each rack held one projectile and was tilted slightly so that the projectile point was higher. (A D Baker III)
The ‘E’ class was the ultimate development of the wartime British light cruiser, reverting to side-mounted single 6in guns to gain ahead fire. HMS Emerald is shown as completed, with a rotating flying-off platform aft and with triple torpedo tubes (although the decision had already been made to fit quadruple tubes).
By 1931, Emerald had her planned quadruple torpedo tubes, but she (and her sister) retained the old rotating flying-off platform.
Emerald shows her new catapult and crane in this 1933 photograph. She and her sister retained their catapults longer than other British cruisers.
The design presented to the Board on 2 May 1918 was stretched to add a seventh 6in gun, on the centreline.29 Protection broadly matched that of earlier light cruisers, the side plating (3in over machinery) being integrated with the hull, covering the machinery and the midships magazines from upper deck to 2ft 6in below the load waterline. The belt extended fore and aft, 2½in thick over end magazines and oil fuel tanks and 1½in to the bow and 2in to the stern beyond. Amidships, the belt extended from the upper deck (weather deck level aft) down to the platform deck. It sloped down fore and aft of the machinery spaces, more sharply aft than forward. In contrast to earlier designs, DNC added 1in decks (at platform deck level, i.e. at the lower edge of the belt) over the magazines and 1in over the machinery at lower deck level (below the upper deck). Because the magazine sides were entirely below the belt, ¾in was added to their sides and ends to a depth of 3ft. The 1in deck over the engines, but not the boilers, was described as an improvement on previous ships. Unlike previous cruisers, this one lacked an armour bulkhead over the after end of the machinery.
The machinery arrangement was unusual, spaces being separated for survivability. There were four boiler rooms (two boilers each), the forward engine room being abaft the three forward engine rooms, with No. 4 boiler room abaft that and then the after engine room. The midships 6in magazine and shell room (and a crew space above them) separated the three forward (contiguous) boiler rooms from the forward engine room. The after boiler room was immediately abaft this engine room, but the magazine and shell room for No. 5 gun separated it from the after engine room further aft. The forward engine room drove the two outer shafts. Boilers in Nos. 1 and 4 (end) boiler rooms were in tandem, with oil bunkers alongside, an arrangement revived in the 1930s. The boilers in each room fed a funnel. The boilers arranged side by side in Nos. 2 and 3 boiler rooms all fed the same fatter funnel. The ship used two sets of Shakespeare-class (destroyer leader) machinery. As in other light cruisers, the foremast and bridge were right up against the tripod. With so much power on a relatively light hull, they enjoyed high speed; even in June 1944 HMS Enterprise could outpace much newer US cruisers (USS Tuscaloosa and Quincy) off Normandy. DNC could not provide a bulge as in the Hawkins class without sacrificing speed, but he argued that the unusual machinery arrangement provided much the same survivability against underwater damage. On this much length, it was not difficult to provide length for a revolving aircraft take-off platform, which both ships carried until 1935-6, when catapults were fitted.
The Board Stamp was applied on 9 May 1918. In August 1918 two versions of the ‘E’ class were sketched with 7.5in (as in Hawkins) rather than 6in guns as responses to a reported German cruiser armed with 8.2in guns (this information was considered dubious).30
The Emerald class became the basis for initial post-war cruiser thinking. In 1920 replacement of the triple tubes with quadruple ones was approved, although the change was not carried out until 1929, when the ships had their first major post-construction refits. Emerald was completed to the original design, but Enterprise had the prototype twin 6in turret and DCT.31
Construction was drastically slowed by the 1918 Armistice. In the 1923/4 Estimates Controller argued for completion of these two ships rather than the beginning of work on the new Kents on the grounds that they reflected advances which might be incorporated in the later ships (presumably referring to the turret and DCT).
The Hawkins class
The only other First World War cruiser design was DNC’s favourite large overseas design, which became the Hawkins class. He repeated his proposal for these ships in a memo dated 12 October 1914 to the Admiralty Board. This time his argument was that for commerce protection something like a Birmingham was needed, but larger and faster, with a good steaming radius, and adapted to burn coal and/or oil, so that they could obtain fuel easily abroad. In his view it was an open question whether they needed sufficient protection to resist 6in fire, in which case they would have to be considerably larger than a Birmingham.32 Design work was ordered after a Sea Lords meeting on 9 June 1915.33 The ships were described as improved Birminghams capable of 30kts, with ten or more 6in guns mounted as far as possible on the centreline. Their machinery should be arranged so that one-fifth power could be achieved with coal, ‘a great convenience, if it is not an absolute necessity, in ships intended for use abroad which may have to pick up supplies in all sorts of inaccessible places.’ The new 5.5in gun had been discussed as an alternative to the 6in, but it had been rejected in view of reports that new German light cruisers would have 5.9in guns (however, given its lighter shell and therefore faster rate of fire, 5.5in might be the ideal gun for future capital ship secondary batteries – as it was in HMS Hood). In a Minute for the Board (and, presumably, the Cabinet) on the new construction programme for 1915/16, the First Lord (Balfour) repeated DNC’s argument: ‘The rapid deterioration of our older cruisers will necessitate before very long a replacement of cruisers suitable for foreign service; and the Board consider that preparation should be made for six such vessels later in the year.’34 Alternative designs were already being prepared. Current knowledge of the German shipbuilding programme made it unnecessary to order any more North Sea light cruisers. Once a design had been chosen and orders placed, ships might be delivered in eighteen months.
HMS Hawkins is shown dressed overall for a naval review, possibly in 1935. At this time she retained all seven of her 7.5in guns.
Raleigh as completed in September 1920. The sides amidships had considerable flare above the bulges. Except for the two guns abreast the after funnel, the 7.5in guns were mounted in pits and had a circular working area that revolved with the mounting. The amidships pair had folding semi-circular working deck platforms inboard and outboard of the mountings. Wooden decking was not shown on the as-fitted drawings, but it may have been fitted. Annotations on the plan indicate that the bridge was modified as on later units of the class prior to the ship’s loss. She ran aground at high speed at Point Amour, Foreteau Bay, Labrador, on 8 August 1921. She was stripped of useful equipment and used as a gunnery target until blown up by a party from HMS Calcutta during September 1920. (A D Baker III)
Frobisher as rearmed in February 1942. She had served pre-war as a cadet training ship, and she reverted to that role in May 1945. As shown she had Type 281 air-warning radar (two antennas at her mastheads), a Type 273 surface-search radar in a ‘lantern,’ and two Type 285 radars atop her 4in directors. She had passive acoustic intercept gear near her bow. The pompom directors lacked radars. The 7.5in guns were controlled by a single foremast director, without any associated radar. In May 1944 at Lyness she was fitted with eight additional Oerlikons: two Mk IIIA mounts slightly staggered abaft the existing centreline mount on the forward director, and six lightweight Mk VIIA (four atop the flag officer deckhouse forward of the break of the forecastle, two abreast the 4in gun on the quarterdeck). At the same time her four fixed torpedo tubes were apparently removed. As a cadet training ship (conversion completed 1938) she retained a single 7.5in gun (the aftermost mount on the quarterdeck) but retained the forward pair of 4in HA mounts. On the platform formerly occupied by ‘B’ 7.5in gun a two-level deckhouse was erected, and the other 7.5in on the quarterdeck was replaced by a crane to handle a floatplane stowed at the after end of the forecastle deck. Annotations on the 1942 plan show that it was intended to remove the foremost 7.5in mount on the quarterdeck and to add two more Oerlikons. However, the ship emerged in May 1945 with only three 7.5in guns (‘A’ gun, the superfiring gun aft, and the foremost quarterdeck mount). An open 6in mount replaced ‘B’ gun. Of the 4in guns, only the quarterdeck mount was retained. The ship also had eleven Oerlikons, including two in the circular tubs high in the superstructure formerly occupied by pompom directors. The depth-charge rack was removed, and the aftermost 7.5in gun replaced by a 21in torpedo tube (probably a twin). All splinter shielding around the 7.5in and 4in guns was removed, and the Type 281 radars replaced by a single antenna at the top of the foremast (probably Type 291). (A D Baker III)
Effingham as rebuilt and rearmed, 1939. (John R Dominy)
Vindictive as a repair ship, 30 March 1940. She was armed with six 4in HA guns, two quadruple pompoms and two single depth-charge release gear (total of six depth charges). The upper masting and rigging arrangement is estimated from the one available photograph, and is incomplete. Note the unusual height of the boot topping, shown as the ship was painted in 1943. By that time she had received six single Oerlikons, three on each side atop the large workshop structure abaft the funnel. Also by that time the forward-most of the two large Carley floats had been replaced by a smaller one. She did not carry any radar early in 1943. However, she seems to have been fitted with Type 286 by August 1943 and with Type 291 January 1944. By August 1943 she also had Type 285 for 4in control. As a demilitarised training ship she had already been reduced to six operational boilers, and the inboard turbines had been removed; but the inboard shafts, minus propellers, were retained, as was the hull armour.
DNC looked at five alternative batteries: eight, twelve and fourteen 6in; two 9.2in and eight 6in; and eight 7.5in QF. The chosen design was armed with seven 7.5in plus ten 3in (four of them HA). In the proposals for HMAS Adelaide, the 7.5in guns were in gunhouses (at least as sketched), but in the ship finally chosen they were in central-pivot mounts like those of 6in guns. Five were mounted on the centreline (two were superimposed forward and two aft, with another after gun on the same level as the lower of the superimposed pair), and two on the sides amidships, roughly abeam the second funnel. It is not clear in retrospect why the ships had a secondary 3in (12pdr) armament, but these guns may have been wanted to beat off attacks by small fast craft, the 7.5in firing too slowly for that. Two were mounted in embrasures in the forward superstructure which supported ‘B’ 7.5in gun, two on the bridge wings, two on a platform abaft the forefunnel, and two abaft (and to either side of) the superfiring 7.5in gun aft. All were subject to blast from the 7.5in guns. The four 3in HA guns were concentrated on a platform just forward of the after superfiring 7.5in gun. While the ships were being designed, underwater torpedo tubes were rejected for the light cruisers in favour of deck tubes. The same reasoning ultimately led to the addition of four above-deck tubes just forward of the superfiring 7.5in gun aft.
The most unusual feature of the design was the combination of inward-sloping sides and bulge similar to that chosen a few months earlier for the ‘large light cruiser’ (or light battlecruiser) HMS Furious, recently designed (a similar form was chosen for HMS Hood). DNC claimed later that subdivision provided a two-compartment standard of protection against underwater damage, and that the sloping sides contributed substantially to the ship’s girder strength. The slope (10°) was chosen so that the beam at the waterline matched that of the outward-flaring forecastle deck. The limited draft and high freeboard provided the ship with great reserve buoyancy. Belt armour extended from the forecastle deck down to the platform deck. Machinery occupied three adjacent boiler rooms separated from the two engine rooms by a 7.5in magazine and shell room which served both the two wing 7.5in guns and the foremost of the after centreline mounts. The coal bunker was at the after end of the midships boiler room. Uptakes from the forward boilers and from the forward boilers in the midships boiler room were trunked into the forefunnel, and from the after boiler room and the after boilers of the midships boiler room into the after funnel. Four boilers occupied each engine room, with four coal-burners in the amidships room and four oil burners in each of the others. As a measure of the lower efficiency of a coal-burning boiler, it took four coal-burning boilers to produce a sixth of the total machinery output.
Above and below: HMS Frobisher is shown in June 1930, the after superfiring gun having been removed to provide space for a floatplane. It was served by a mobile crane, but the ship had no catapult, at least at this time. Neither crane nor floatplane is present here.
At a naval review on 15 July 1935, Frobisher displays her aircraft arrangements. By this time both the after superfiring gun and one of the two quarterdeck guns had been landed.
Under the terms of the 1930 London Naval Treaty, the Royal Navy disarmed its Hawkins class cruisers in return for ending construction of heavy cruisers by other navies. HMS Frobisher is shown as a nearly disarmed training ship.
By this time the existing 3in and 4in anti-aircraft guns no longer seemed adequate. First Sea Lord asked whether the ‘E’ class could have two of its 6in guns on dual-purpose mountings. This seems to have been the first proposal for such weapons.35
Although six ships were planned, four (Raleigh, Effingham, Frobisher and Hawkins) were ordered in December 1915. A fifth (Cavendish) was ordered in April 1916. In 1917 Cavendish was ordered converted into a carrier (and her construction expedited), and in 1918 she was renamed Vindictive to commemorate the ship which had served heroically as a blockship at Zeebrugge. In November 1917 the Board ordered the three least advanced (Raleigh, Effingham and Frobisher) converted to burn only oil fuel, their rated power increasing to 70,000shp. Their four amidships coal-burning boilers were replaced by Yarrow small-tube boilers like the eight in the other two boiler rooms. Frobisher and Effingham received only two new oil-burning boilers, and were rated at 65,000shp.36 When Hawkins was converted in 1929, the coal-burning boilers were removed without replacement, but the remaining boilers were boosted to give an output of 55,000shp.
The ships were criticised for their gun arrangement, the captain of HMS Hawkins pointing out that the two guns aft on the quarterdeck were very wet with any sea running, or with the ships steaming at high speed, and that because the berthing rails were taken down when the guns were cleared for action, their crews, particularly at the after gun, were uncomfortably close to the ship’s side. Controller asked the captain of the other ship of the class in service, HMS Raleigh, whether he agreed. He pointed out that after guns in all light cruisers were wet (and not from speed alone), but that No. 1 gun was worse. Also, the after gun suffered from extreme vibration at high speed; ‘this is so bad that I consider it would adversely affect the nerves of the men stationed at the gun for any length of time under these conditions.’
He considered the 7.5in gun unsuitable for light cruisers due to its low rate of fire (two-thirds that of a 6in under favourable conditions, offering 30 per cent more weight of metal but worse control due to more time between shots); and the large gun crews required to supply four rounds per minute (‘absurdly out of proportion to those required in, say, a 15in turret’). They amounted to twenty-five men for No. 1 gun, but to forty-three for the superfiring No. 2, and to thirty-nine and forty-four for the two waist guns, which shared one magazine and one shell room. Ammunition for No. 2 gun had to be passed along the deck between dredger hoist and hand-up to the gun. It would be a vast improvement if magazine and shell room could share a single enlarged dredger hoist (which had to be large enough to take the protective cases over the bagged powder). DNO saw proof that any new heavily-armed cruisers should have power-worked shell and cordite hoists directly under the guns.37 He was looking forward to the 8in cruisers then being discussed (see below). Although the point generally was not made, a cruiser had relatively few potential magazine positions. If 8in guns had to be directly above each such position, and if more than three or four were desired, they had to be in multiple turrets or gunhouses – as was done in the next class of large cruisers, the Kents (whose earliest stages coincided with this discussion). DGD defended the 7.5in gun as far more formidable than a 6in, given its much heavier shell (200lbs) and greater stopping power (as demonstrated in trials with the ex-German cruiser Nürnberg). It offered longer range, and it could be controlled at much longer range because the splashes from its shells were much more visible. DGD noted that Raleigh had carried out relatively little firing, hence these virtues had not become evident (she would soon be wrecked). These were important arguments for DGD, who strongly espoused 8in guns for future cruisers.
Above and below: HMS Effingham, the third Hawkins class cruiser, was rearmed with 6in guns, preserving her as a combatant ship under the 1930 and 1936 treaties. Had war not come in 1939, the other two ships would also have been rearmed, though possibly not with single open 6in guns. Presumably single 6in guns became available as ‘C’ class cruisers were converted into anti-aircraft ships. Effingham was lost when she struck a rock during the 1940 Norwegian campaign.
Above and below: HMS Frobisher is shown in April 1942, newly rearmed, just before joining the Eastern Fleet. She had been laid up at the outbreak of war for rearmament, to follow Hawkins, but work was slowed, presumably by the press of more urgent projects. She was to have had the same armament as Hawkins, but two more multiple pompoms replaced the two waist 7.5in guns. The rearmament refit, at Plymouth, lasted from 5 January 1940 through March 1942. Frobisher commissioned on 10 February 1942, ran trials, and sailed for the Clyde (where these photographs were probably taken) on 4 March. Note that the two waist 7.5in guns were not remounted; she was reduced to five such guns. Other armament at this time was five 4in HA, four quadruple pompoms, seven Oerlikons, and two Lewis guns. She also had four single fixed above-water torpedo tubes. Note the Oerlikon just forward of No. 2 gun, and the 4in gun just abaft one of the quarterdeck 7.5in guns.
A preferable armament would be six 6in guns (in positions now occupied by Nos. 1, 2, 4, 5, 6 and 7 guns), the two waist guns being replaced by one on the centreline. A 6in gun should replace the after control position on the centreline, at the same height (on the forecastle) as No. 4 gun. Two 4in HA guns could replace the waist 7.5in. The HA guns were poorly placed, blocked by rigging (including wireless aerials).38
Although in 1922 it seemed impossible to imagine rebuilding the Hawkins class, exactly that idea was raised in 1925. The advent of the 8in cruisers led to interest in rearming the four surviving ships with three 8in turrets each. In March 1925 DNC produced a sketch design for Frobisher showing two turrets forward and one aft, using the same turrets which had been selected for the Kent class. This design would also apply to Effingham, and to Hawkins if the ship were converted to all-oil fuel (Vindictive was a more complicated proposition because of the catapult in ‘B’ position). DNO pointed out that although there was sufficient space forward, the side bulkheads of the magazines and shell rooms aft, which were also the sides of the shaft passages, could not be moved to provide sufficient space, and the vertical height was also insuf-ficient.39 A new twin 8in design would be required, and it was not clear that it could provide a sufficient rate of fire. Ammunition capacity would be about 120 rounds per gun, rather than the 150 in a Kent. Worse, rearmament would add weight, and the Hawkins class was already close to the 10,000-ton limit. Not only would the new armament weigh more (although crew would be cut somewhat), but they would need an additional generator. Even with only 100 rounds per gun, the ship would gain 170 tons; she was already only 150 tons below the limit, and, DNO wrote, ‘great importance was attached by the last Cabinet and Foreign Office to keeping within [the 10,000-ton] limit’. Rearmament would slightly reduce metacentric height (by an acceptable 6in), and the ship would trim slightly by the bow (which could be offset by using oil fuel tanks in the correct sequence). About 100 tons of oil would be sacrificed (300nm at 12kts). The arrangement of HA guns would improve. The cost would be high: £517,500 for guns, mountings, and ammunition and about £170,000 for the reconstruction; converting three ships would buy a new ship of about the same size. Moreover, the Hawkins class had poor magazine protection compared to a Kent. It would take about nine months to prepare a design for the after mounting and another eighteen months to deliver the first such mounting, plus nine to twelve months to rebuild the ship and run trials. Against all of this, the six 8in power-operated guns offered considerable advantages both in rate of fire and in weight of broadside (6,144lbs vs 3,500lbs per minute); and the 8in shell offered more explosive, weight for weight, than a 7.5in shell. Turrets themselves offered considerable advantages, including blast protection from neighbouring guns. Controller noted all the disadvantages cited by DNO and cited another: other powers would notice what was being done, and might accelerate their own cruiser programmes accordingly. The improvement was not worth the money. ACNS agreed, pointing out that the armour protection of the Hawkins class was outdated, their magazines unprotected against long-range plunging fire from 8in guns.
Above and below: As rearmed, HMS Hawkins differed from Frobisher in having all seven 7.5in guns (as refitted at Portsmouth, 4 December 1941 – 7 May 1942 she had two rather than four quadruple pompoms). Hawkins also had two single pompoms, seven Oerlikons and two Lewis guns, plus four fixed above-water torpedo tubes. Radar was installed (Types 281, 273 and 285). These photographs were taken in June 1942. Hawkins had been brought back into service in 1940. At that time she had four 4in HA guns, four single pompoms and two machine guns. The quadruple pompoms were replaced by octuple pompoms during a further Portsmouth refit, 8–23 August 1944, and two single Oerlikons were added.
HMS Hawkins late in the Second World War, presumably after the 1944 refit. Note the Oerlikon atop the shield of No. 2 7.5in gun.
Above and below: Frobisher is shown on 1 May 1945 in the Firth of Forth, having been converted into a training ship with a wide variety of weapons. Note that her air-search radars, but not her other radars, have been removed.
ACNS had another way to look at the issue. The four Hawkins could be seen as individual counters to four Japanese 33-knot cruisers armed with 5.5in guns, superior to them in everything but speed. Laying the four British ships up for eighteen months to three years to become counters to the four Furutakas would leave the British with the problem of commissioning four 6in cruisers from reserve – ships of which the Royal Navy was short. Four such cruisers would have to be built, their cost added to the cost of rearming the Hawkins class. ACNS assumed a modern 6in cruiser would cost £1.3 million, compared to £2 million for a Kent, the difference of £700,000 being about what it would cost to rearm a Hawkins. On this basis rearming the Hawkins class and building the required new cruisers would cost as much as simply building four Kent-class cruisers. Against this, DGD suggested that the Royal Navy risked entering the next arms control negotiation with fewer 8in cruisers than the Japanese. DCNS agreed with ACNS that rearmament was not worthwhile. The Sea Lords decided not to pursue the idea. ACNS also asked DGD about simply modifying Hawkins class magazines.
Since the London Naval Treaty of 1930 limited the number of British cruisers with guns of more than 6.1in calibre (see below), DNC was asked whether the four large Hawkins class cruisers could be rebuilt with the standard light cruiser battery of four twin 6in guns.40 They would be somewhat large for this battery, but they had reasonably modern hulls. Turrets and ammunition (200 rounds per gun) would weigh 466 tons, compared to 460 tons for the 7.5in guns (150 rounds per gun), so main armament weights would balance out. The only major addition would be protection to the ammunition lobbies and gun supports. Frobisher was rated at 9,860 tons standard and Effingham at 9,770 tons, so both offered sufficient weight. Existing magazines and shell rooms were large enough, and could be adapted; the ammunition lobbies would displace some living space, but on the other hand complement would be reduced. Adding 3in to the magazine crowns would cost another 250 tons (1½in would cost 125 tons). Adding a catapult crane, and seaplane would add another 50 tons, and with extra magazine armour would bring displacement somewhat above 10,000 tons. DNC attached an outline profile to his report to Controller on 1 April 1930; it has been lost.
Above and below: The last ship of the class, HMS Cavendish, was renamed Vindictive to honor the cruiser used as a blockship at Zeebrugge in 1918, and was completed as a carrier. she is shown soon after the First World War. In this guise she retained four of her seven 7.5in guns: one right forward, one right aft, and the two waist guns. she operated in the Baltic during the war of intervention against the Bolsheviks, ran aground, and was severely damaged. Repairs at Portsmouth continued into 1921, and she was then laid up (used at times for trooping). She was converted back into a cruiser in Chatham in 1923–5. (View from aft from RAN Historical Branch)
Nothing was done. The treaty required that navies reduce their cruiser forces to the allowed numbers by 31 December 1936. By that time the British had invoked an escalator clause, which allowed them to retain some smaller cruisers which would have been scrapped. However, they much valued the limit on cruisers with larger guns, and it was retained in the 1936 treaty which superseded that ratified in 1930. Something had to be done with the four Hawkins class. Frobisher and Vindictive were reduced to training ships in 1932, Frobisher being reduced to five 7.5in than then to one 4.7in in 1936. As a training ship Vindictive was reduced to two 4.7in guns and her original pair of submerged torpedo tubes. She also lost half her boilers. Hawkins was disarmed and laid up in 1937.
In 1937–9 Effingham was rebuilt with nine 6in guns in single rather than twin mounts, plus the usual four twin 4in HA guns, two octuple pompoms, and the usual pair of quadruple 0.5in machine guns. She was given an E.IV.H catapult. Her ten boilers were reduced to eight, the after boiler room being converted into oil fuel tankage. That made it possible to trunk the remaining uptakes into one large funnel. Power was reduced from the original 66,000shp to 61,000shp. About June 1938 it was proposed that the other two ships be rearmed with six twin 5.25in guns and fitted with heavy catapults as in current cruisers and the rebuilt ‘Counties’.41
Instead, Hawkins and Frobisher were rearmed with 7.5in guns after war broke out. Hawkins emerged in 1940 with seven 7.5in, four 4in HA, two quadruple pompoms and seven Oerlikons, plus four fixed abovewater torpedo tubes. For Frobisher, a planning conference was held on 27 August 1939, the ship to be taken in hand in September. At this time she was to be fitted with four single pompoms, two of which would later be replaced by quads. The submerged torpedo tubes would be removed. The ship was completed in 1942, with five 7.5in (seven were originally intended; the two waist guns were not re-installed), five 4in HA, two quadruple pompoms (increased to four in 1941), two single pompoms (removed in 1941), three Oerlikons (seven in 1941), and four upper deck torpedo tubes. The support for No. 5 7.5in gun had to be replaced (all the other gun supports remained in the ship), the above-water tubes had to be replaced, the crane and seaplane gear had to be removed, and 4in guns and magazines re-installed.
Above and below: Vindictive is shown as a cruiser in 1927. She had the first Royal Navy catapult, mounted athwartships atop the hangar retained from her service as a carrier. The prototype Carey catapult was driven by compressed air via a system of pulleys, the air piston travelling 20ft to move the catapult cradle 60ft. Capacity was 7,000lbs at 45kts. This catapult first launched aircraft (Fairey Flycatcher and IIID) at sea in October 1925.
In August 1944 a conference was held to decide how to convert Frobisher into a training ship for 150 cadets. She was then being repaired at Chatham after battle damage, and was to be taken to Rosyth for conversion beginning in September. The 7.5in main armament was not required, nor was a speed over 15kts (for which two shafts would suffice; the after boiler room, with its two boilers, would be shut down). The pompoms would be removed, the Oerlikons retained. It was decided to replace No. 2 gun with a 6in or 4.5in gun, and No. 5 gun with, if possible, an above-water torpedo tube; if possible No. 4 gun would be removed to add clear space on the quarterdeck. All of the 4in guns would be landed. As a cadet training ship in 1945, Frobisher had three 7.5in guns, one single 4in HA gun (in ‘B’ position), thirteen single Oerlikons, a set of quadruple torpedo tubes, and two light machine guns. She was ultimately replaced in this role by the newer heavy cruiser Devonshire.
Like her two sisters, Vindictive was largely disarmed and reduced to training duties under the 1930 London Naval Treaty. However, she also had her after boilers removed, permanently reducing her speed and making it unprofitable to rearm her like her sisters.
Once war broke out Vindictive was taken in hand at Devonport for a conversion similar to that of HMS Effingham. This work had low priority, so little had been done by early October. Given her reduced speed, a simpler proposal was made to use equipment like that in an armed merchant cruiser.42 The minimum conversion would provide four 6in on her centreline; another two could be added, one on each side of the old 7.5in platforms. In addition, she could have three single 4in HA guns (with a HA computer position containing a destroyer-type Fuse-Keeping Clock[FKC]), and four single pompoms. The computer position would be placed on the centreline in the existing superstructure. E-in-C was to consider converting the after boiler room (now a laundry) to oil fuel stowage, giving a total of 2,640 tons rather than 1,000 tons, and a radius at full speed of 3,470nm rather than 2,240nm. Added weight would decrease the ship’s maximum speed from 24kts to 23kts. The earlier above-water torpedo tubes would not be replaced. Instead, Vindictive was converted into a repair ship.
Vindictive was converted into a repair ship in 1939–40, completing on 30 March 1940, in time to serve during the Norwegian campaign. She was assigned to the South Atlantic in 1940–2 and to the Mediterranean in 1943–4. She is shown entering Mers-el-Kebir in 1943. At that time she was armed with six 4in HA guns and two quadruple pompoms; by April 1944 she was also credited with six Oerlikons (at least two of which are visible here).