THE central British destroyer tactical concept of the interwar period was still the long-range browning shot. It became, if anything, more significant as the Royal Navy failed to extend effective battleship firing range much beyond 15,000 yards (one 1939 manual called this the range ‘best suited to our national characteristics’). British naval intelligence knew that the US Navy thought it could fight at 30,000 yards by about 1930, and probably the British assumed that the Japanese could do about the same. The annual Progress in Tactics reported attempts to close the range gap. One was to use torpedo fire, necessarily by destroyers, to force an enemy commander into gun range. Unless he could be forced, he could destroy much or all of the British battle line as it slowly closed the range. This sort of complex battle plan was practicable because the Royal Navy had been developing plotting as a means of providing a fleet commander with a kind of synthetic situational awareness, HMS Vernon, the torpedo school, was responsible for developing and testing the early automatic plotters (dead-reckoning tracers in US parlance) which made the plot – and therefore the tactics – a practicable proposition. The idea of the tactical plot had first arisen in 1914, but it took until the late ‘twenties for it to become effective.
The A class leader Codrington set a pattern for leaders during the interwar period. She was essentially an A Class destroyer with an extra 4.7in gun between her funnels. The broad (four-foot) black band at the top of her forefunnel indicated her leader status. The three bands on the second funnel indicated the flotilla. These markings were adopted in 1922. The forefunnel carried the band for either a leader or a divisional leader (two feet wide, three feet below the funnel top, black for the Mediterranean and white for the Atlantic (later Home) fleet. At this time there were six flotillas in the two main fleets: 1st (Mediterranean, one black), 2nd (Mediterranean, two black), 3rd (Mediterranean, three black), 4th (Mediterranean, no band), 5th (Atlantic, one white), and 6th (Atlantic, two white). By 1935, the 2nd Flotilla had changed to one red band (changed to two red bands in 1937), and the eighth (China) flotilla had one black band over one white. In 1938, the three Home Fleet flotillas had one (4th), two (5th), and three (6th) white bands. The system was greatly expanded in 1939 to accommodate many new flotillas. Two-funnel leaders had deep red (Mediterranean) or black (China) or white (Home Fleet) bands. The E class (12th Flotilla, Rosyth) had one white band over two red, the F class (8th Flotilla, Home) had three white bands, the G class (1st Flotilla, Mediterranean) had one red band, the H class (2nd Flotilla, Mediterranean) two red bands, and the I class (3rd Flotilla, Mediterranean) had no bands. There were six flotillas of V & W class destroyers: 9th (Home) with one black over two white bands; 10th (Home) with no bands; 11th (Western Approaches) with one black over two red; 13th (Gibraltar) with one white over two red; 14th (Home) with one red over one black; 15th (Rosyth) with one red over two black; and 16th (Portsmouth) with one red over one white. The new single-funnel destroyers not described in this book had other band patterns.
(FAHEY COLLECTION, US NAVAL INSTITUTE)
In 1937, the Tactical School reported a further twist: in several of its simulated fleet actions, one side managed to manoeuvre the other so that one or more of its flotillas could reach firing positions without having suffered much gun opposition. These flotillas could therefore reach really close ranges before having to fire, enjoying a much greater probability of hitting. Under such circumstances individual shots or shots from sub-flotillas suddenly became effective, as ranges might be as short as 1500 yards. In effect this brought thinking back full circle to that current before and during the First World War.1
Destroyer replacement began with the leader Codrington and the eight Acasta or A class destroyers of the 1927–8 Programme, policy calling for a new flotilla (leader and eight destroyers) each year. Later destroyers, through to the I class, were essentially updated versions. Formulation of a Staff Requirement began with an ACNS minute dated 1 June 1926. The Staff Requirement was due by November, so that invitations to tender could be issued in time for contracts to be let early in the 1927–8 fiscal year. As with the two experimental ships, a conference was called to develop the requirements.
The first item to be settled was endurance, because it effectively set the ship’s displacement. At a 6 July meeting, the Director of Plans asked for more: 2000nm at sixteen knots (with steam for eighteen knots) and twenty-four hours at two-thirds power. When the proposal was repeated at an 11 August meeting, the DNC pointed out that Ambuscade would need another 200 tons of fuel to satisfy it; she would displace 2200 tons rather than 1600 tons. She would no longer be acceptable as a destroyer. The Director of Plans asked what Ambuscade could actually do: 1500nm at sixteen knots plus only eight hours at two-thirds power. He settled for 1500nm at sixteen knots plus twelve hours at two-thirds power. These figures probably all reflected the needs of a fleet steaming from Singapore (at relatively high speed) to fight a Japanese fleet, allowing for twelve hours of combat. The 5000nm of the earlier requirement reflected more the need to escort the fleet all the way from, say, Trincomalee to Singapore.2 The need for endurance would justify the expense and weight of cruise turbines. When the two prototype destroyers ran endurance trials, it turned out that they burned less fuel than expected, so in March 1927 the planned fuel capacity of the 1927 destroyer was reduced from 400 to 350 tons (it seemed that 325 tons would suffice, the other twenty-five tons being a safety margin). Requirements finally approved in January 1927 stated that it was essential that destroyers and leaders be capable of fuelling at sea while under way or in exposed anchorages where they could not lie alongside a tanker.
There was some question as to how endurance should be calculated. The usual practice was to use trials figures for the horsepower at endurance speed, together with the measured fuel consumption per mile at that speed. These figures were used for comparison with foreign ships, and also for comparison with existing designs. However, they were not useful for staff purposes (ie, for planning), as they were somewhat unrealistic. As an alternative, figures were taken from the fleet. The DNC was not sure the figures were entirely reliable. For the new destroyers, the DNC used trial figures (tons per hour and pounds per shp per hour) for up to 5000shp, correcting these for fouling (ship out of dock six months). Endurance was somewhat reduced and, for example, Acasta was credited with 3570nm at fifteen knots instead of the usual 3500nm.
The destroyer was seen primarily as a fleet torpedo boat, so she would have two quadruple 21in tubes, a type recently developed for the cruisers Emerald and Enterprise. A quintuple launching frame was already being developed and which, it was hoped, would weigh less than a quadruple tube including torpedoes, but it would not be ready for destroyers completing by April 1931.
HMS Anthony shows the new standard block bridge containing a fire control computer and supporting a director and a separate nine-foot rangefinder (the director was not installed when the ship was completed, but was added later). The rangefinder was the same FQ2 fitted on board First World War leaders and V & W class destroyers. In this designation, F indicated a low-angle rangefinder and Q indicated a sub-type. Mountings were designated in a separate M series. FQ2 was built in both nine-foot and twelve-foot versions, and was considered effective between 500 and 40,000 yards. The projection and davits aft were for TSDS (two-speed destroyer sweep). Because the ship was conned from the open bridge on top, the platforms at helmsman level were used mainly for signalling (they were called the signal deck). On trials, HMS Anthony made 36.31 knots on 34,415shp (366.4rpm) at 1430 tons.
As before, the ship would have four 4.7in guns, but in the new design they would elevate to forty degrees rather than thirty degrees. One gun, preferably No 2, would elevate to sixty degrees for anti-aircraft fire, the extra weight being accepted.3 The Staff Requirement finally adopted had the elevation reduced back to thirty degrees, but the requirement for the sixty-degrees gun (with ‘single gun unit system of fire control’) survived. Moreover, this gun would have one hundred high-angle rounds in addition to the 190 rounds the other guns had. The ship would have two pompoms (2-pounder machine cannon) and Lewis guns. Providing pompoms amidships somewhat complicated the ship’s design, since two broad gangways had to be provided from the forward magazine to them. In the approved design, quadruple 0.5in guns were offered as alternatives to the two single pompoms, in the same positions, and the ship had four Lewis guns.4 The final armament statement also showed only one type of 4.7in gun, the sixty-degree high-angle mount not being installed.
The single high-angle gun required a control system, which in turn required a height-finding rangefinder (it was impossible to spot in range for anti-aircraft fire). The report of the Ambuscade trials argued that the rangefinder should not be mounted on the director tower, leaving very little space on the bridge. Fortunately it seemed unlikely that the ship would fire against air and surface targets at the same time. The DGD therefore suggested placing a heightfinder (rangefinder type UB) on the forebridge.
Through the design stage, it was assumed that the 1927 destroyers would have sophisticated fire control systems, including below-decks computers, like the two experimental destroyers; in fact rather late in the design process, the DNO asked that the below-decks transmitting station be enlarged. In August 1928, however, it was decided that instead the ships would have much the same fire control arrangements as the Repeat W class, with nothing more than a Vickers Clock below decks. This seems to have been a reaction to the undue complication of the Barr & Stroud computers in the two experimental destroyers. It turned out to be a temporary reversal, because the Admiralty adopted a somewhat simpler computer in the C class.
All destroyers would be built so that they could be fitted with Asdic, but not all would have it installed. The standard depth charge armament (two throwers, four chutes, and eight charges) would be carried, with provision for more charges (in the final version of the Staff Requirement, ‘say an increase of four’) for anti-submarine work. Because the first few flotillas would replace earlier ships intended for torpedo attack, the first flotilla would not be fitted for minelaying (but later flotillas might be so fitted). The final version of the Staff Requirement (January 1927) added that the ship was to be fitted to take the new ‘high-speed minesweep’ (by late 1926 the two-speed destroyer sweep or TSDS) now under development by Vernon. Later it would be decided whether the whole flotilla or only one division was to be so fitted. The TSDS was tested on board the old destroyer Skate. Combining TSDS with depth charges congested the stern, so in September 1927, the DTM suggested that ships with TSDS have four hydraulic depth charge chutes, those without (but with Asdic) having depth charge rails. The final armament statement showed eight depth charges, all stowed on deck. In the end the A class had TSDS but no Asdic, the idea being to fit alternative flotillas with TSDS and Asdic. The arrangement of depth charges was designed to support a five-charge attack (two from the throwers, three from rail or releases). On this basis, in August 1928, with ships under construction, it was decided that the A class would have three depth charge chutes (two to starboard) and six charges, but no throwers.
Full speed at full load (a stiffer requirement than previously) would be at least thirty-three knots. In effect this was reversion to the pre-1912 standard. The conference observed that service speed was often at least five knots less than nominal speed, hence that the usual figures obscured actual performance. For example, to drive the Amazon at thirty-three knots fully loaded (1810 tons) would require 44,500shp. The corresponding figure for Ambuscade (1600 tons) was 39,000shp.
The design of the ships’ bridges would take experience with the two prototypes into account. Visiting Ambuscade in March 1927, the Controller was struck by the sheer size of her bridge, which he considered suited more to a light cruiser than to a destroyer (the ship’s captain agreed). It would cause considerable wind resistance. A large bridge would also cause problems when the ship rolled heavily, and provided a large unneeded charthouse beneath the open bridge. The CO of Ambuscade suggested streamlining the bridge of future destroyers. If that were done, the CO of Amazon suggested placing searchlight and torpedo sights on the centreline to reduce the width of the bridge. The Read Admiral (D) reported that V and W class destroyers and leaders suffered significant wind resistance. In the new destroyers, plans to give No 2 gun sixty-degrees elevation pushed the bridge further aft and made for a longer forecastle.
The DNC (W J Berry) offered in July 1927 to streamline the upper bridge to reduce wind resistance, and also to modify the gun shields. Since the streamlined bridge would not have sufficient space for Asdic controls and the necessary plotting table, he proposed relocating both to the lower bridge level. Since available information was limited, he proposed wind tunnel tests. A model of the proposed redesigned bridge was made. The Controller and the Director of Naval Equipment (DNE) were inclined to keep the existing bridge, both because so much space was needed and to provide space for signalmen. The Controller’s committee reported data but reached no conclusions, and it turned out that the bridge in Ambuscade was three inches shorter than in some Repeat Ws, and 2ft 6in further aft. The Controller formally agreed in early September 1927.
After the First World War, the Standard Royal Navy light anti-aircraft gun was the 2-pounder, shown aboard HMS Kempenfelt. In appearance it was a more massive version of the standard Vickers 0.303 water-cooled machine gun. This was the same 40mm/40 gun used in the later multiple (quadruple and octuple) mounts, firing a 1.684lb round at 2400ft/sec. The mount was handworked; during the Second World War, the Royal Navy adapted this gun to a powered mounting based on one designed for the Oerlikon. The gun fired rounds from a twenty-five-round cloth belt at 200 rounds per minute. The famous Bofors gun was also a 2-pounder, but it was longer (60 calibre) and hence had a much higher velocity (2890ft/sec); its shell was also somewhat heavier (1.97lbs).
(CANADIAN NAVY)
The DNC replied by listing all the instruments now placed on the ships’ bridges, commenting that officers had found the bridges of the V and W classes inadequate (and that extensions had been approved). The instruments most responsible for expanding the bridge were the gyro pelorus, the director (gun) control platform, signal projectors (lights), and space for hydrophone (Asdic) control, all essential tactically. Even with the large bridge, it was impossible to place the standard (magnetic) compass far enough from moving steel masses. Charthouses were large because experiments in HMS Winchester clearly showed that the bridge required continuous structural support – a house extending directly down from it. The DNC commented further that visions of small austere bridges were unrealistic. Those on board early wartime destroyers were fitted almost entirely for navigating, but wartime tactical requirements – for example, for effective longer-range fire – made fire control instruments essential. War-built destroyers also needed remote searchlight controls. Although such equipment was initially simple, by the 1920s it had matured into massive devices, needed to achieve effective control. As for centreline torpedo control, in 1916 it was fitted to the K, L, M, and R classes – and reported as ineffective. Devices on both sides of the bridge were then chosen for all leaders and V and later classes. As for a proposal to eliminate remote torpedo control in favour of voice pipes or telephone, Admiral Jellicoe specifically asked for something better in spring 1916. The current Chadburn mechanical control gear was selected over alternative electric and hydraulic devices. Since the ships were to be fitted with Asdic (Type 114 or 115), those on the bridge needed a means of ordering depth charges dropped. Again, that required more bridge space. The great problem was that all the main instruments on the bridge needed unrestricted views; there was simply no space on the centreline.
The DNC estimated that all of the new features would add about 170–200 tons to the displacement of Ambuscade, that is, something like the 1800 tons fully loaded of Amazon. The increase came mainly from the need for more oil, the extra weight of the torpedo battery (four tons for both quadruple tubes plus a ton of deck stiffening, but this increase at or above the weather deck would be multiplied through the ship), and weight required for stiffening due to the greater elevation of the 4.7in guns. The DNC observed that it might be possible to cut oil stowage: about three tons in displacement would be saved for each ton saved on oil stowage.
Ardent
HMS Ardent was a unit of the first post-First World War destroyer class, which set a pattern for subsequent ships through to the I class. In general arrangement she followed the two prototypes, but she had the new 4.7in gun shield (covering the new 4.7in QF gun), w-ich offered the gun crew better protection, and quadruple torpedo tubes. The CP Mk VI** mounting elevated to thirty degrees. British destroyer guns of the interwar period appear particularly long because their trunnions were so close to their breech, to minimise the size of the gun shield and also to keep the breech clear of the deck at high elevation without requiring very high trunnions. The guns therefore had massive counterweights, above their breeches, to balance the weights and moments of their long barrels. Inside the gun shield were the gunlayer and trainer, on seats attached to the shield. The shield also had a platform for the breech operator, but the tray worker (who placed shell and cartridge on the loading tray for ramming) stood on deck, following the mount around. The bridge supported a nine-foot surface rangefinder (MQ1) and a First World War-type destroyer director in a streamlined shield. The A class was fitted to stream the two-speed destroyer sweep (TSDS), the paravanes of which are shown stowed on her quarterdeck, with their davits and the streaming fitting projecting over the ship’s stern. Note how much lighter the davits are than those associated with earlier wartime sweeps. Alongside the paravanes are her three depth-charge chutes (two to starboard). Forward of the after deckhouse are the two sweep winches, one on either side. British destroyer officers later complained that the bridge and guns had been pushed too close to bow and stern, presumably to limit the ships’ size and cost; they were too subject to sea damage. Ardent had three 275psi (600° F) Yarrow boilers, as did Anthony; Acheron had experimental high-pressure boilers (Thornycroft special, 500psi, 750° F); the other ships had the new standard Admiralty 300psi (600° F) three-drum boilers. The contract for Acheron was awarded to Parsons Marine Steam Turbine Co. Ltd specifically to test such machinery, for which the company claimed about 7 per cent improvement in fuel consumption and 10 per cent improvement in steam consumption. Continued problems with Acheron helped convince E-in-C not to accept higher steam conditions, which Yarrow in particular strongly advocated, and which the US Navy successfully adopted in the late 1930s. On trials, Ardent made 35.905 knots on 34,376shp (366.7rpm) at 1383 tons. The Admiralty three-drum boilers were considered a great advance on previous ones because they used superheaters and because they had larger oil sprayers (1200lb/hr against 900lb/hr), which increased the rate of heat release in the combustion space. The usual two nests of tubes, which rose from the two combustion drums to meet in the steam drum at the top, were more widely spread than in earlier boilers. Using superheated steam greatly increased boiler output, but this type of boiler introduced new problems, both with the superheater and with water circulation, which were not overcome until the early years of the Second World War. For example, there had to be a flow back to the heating drums from the steam drum, but there was no distinction between up and down tubes, so until the boilers were modified the water in some tubes simply stagnated. In 1937, HMS Ilex was fitted with the La Mont forced-circulation boiler, the first of its type to be used in the Royal Navy; this type of boiler was also used in wartime steam gunboats. It was slightly lighter than the Admiralty boiler, but less efficient, and its additional pump required more maintenance effort. The US view was that adopting high steam conditions offered better efficiency and hence the sort of endurance needed for Pacific warfare. After the Second World War, the Royal Navy adopted similar boilers, in effect agreeing. It also adopted the lightweight (eg, double-reduction) machinery which the US Navy had pioneered. Ardent is shown in April 1930, newly completed.
(DRAWING BY A D BAKER III)
Half-way through the D class the 2-pounder was superseded by the quadruple 0.5in machine gun, shown here aboard the Canadian destroyer leader Assiniboine. Guns used 200-round linked belts and fired at up to 650–700 rounds per minute (450 with a delay pawl). Muzzle velocity was 2520ft/sec, and the bullet weighed 1.326 ounces. These guns were replaced by single Oerlikons (20mm/70: 0.2721b bullet fired at 2750ft/sec at 200 rounds/minute), but they survived on board many destroyers as late as 1943.
(CANADIAN NAVY)
There was also interest both in better habitability and in making the ships more independent, so that they could be used for detached service – and for the longer runs implied by a Far East strategy. For example, they were fitted with bakeries. They were electrically heated. Both changes implied greater electric generating power; in March 1927, it was recommended that they have two seventy-kilowatt steam generators and one thirty-kilowatt diesel generator, the latter for the load (light, heat, etc.) in harbour (but later the question was raised of whether any existing diesel was reliable enough for such continuous service). Each steam generator would suffice for the usual load at sea – both required for maximum load. The diesel was to be used only in harbour, because its vibration might upset gunnery instruments. There was no mention of a diesel generator to be used in an emergency, as in the US Navy. The E-in-C pointed out that the use of electrically driven equipment to make the ships more self-sufficient would mean that they always had to have generators running, and that the usual engine room personnel were not enough to provide diesel watch-standers in harbour. That had already been provided for. Ambuscade already used much more electrical equipment than her captain considered justified (eg, depth charge control was electric). The DNC pointed out that most of the new electric gear in Ambuscade was used to improve her steaming performance (eg, forced draught fans). Habitability, incidentally, included provision for electric lighting in harbour (with boilers cold). In the end the ships had the same two forty kilowatt steam generators as the two prototypes.
These points were all settled by 5 October 1926. A comparison sheet assembled soon afterwards showed what the Staff Requirement entailed: a ship slightly longer than Amazon (325 feet long rather than 319 feet on the waterline), with the same 31ft 6in beam, requiring 39,000shp to make thirty-three knots fully loaded (and thirty-seven knots at standard displacement), with endurance more or less compatible with the 3400nm at fifteen knots of Amazon. Standard displacement would be 1353 tons, compared with 1352 tons for Amazon (1173 tons for Ambuscade, and 1112 tons for a Repeat W); deep load displacement would be 1740 tons, compared with 1812 tons for Amazon, 1585 tons for Ambuscade, and 1504.5 tons for the Repeat W.
On a similar basis, it seemed that the 1927 leader would be 375 feet long on the waterline, with a beam of thirty-six feet, and requiring four boilers to produce 52,000shp to match the speed of the 1927 destroyer. Instead of pompoms, she would have a 3in anti-aircraft gun. This was enormous growth compared with the previous leader Scott (330 feet on the waterline; 40,000shp; 31.5 knots fully loaded), but foreign large destroyers (the French Tigre and the Italian Leone) were much larger. Displacement would be 1900 tons standard and 2450 tons fully loaded, compared with 1530 tons and 2050 tons for Scott.
The Controller (Admiral Chatfield) was not pleased. The 1927 destroyer would be about the size of Amazon, nearly 300 tons larger than a W; ‘when the W class were built they were considered to be not only as large as was desirable for a destroyer but also they would be suitable for Divisional Leaders’. He focused on the increased speed, increased ammunition load, and increased torpedo armament: ‘in fact everything is steadily going up, including the price’. He expected that each flotilla would cost about £650,000 more than the amount approved in the White Paper that authorised the programme, so that a four-year programme would cost £2½ million more than that reported to the Cabinet. It was true that the leader was smaller than French and Italian ships ‘but it is presumed that these countries can afford vessels of this size for the reason that they do not build many of them, whereas we shall have to have a considerable number’. The Controller had to save £86,000 out of the estimated £501,450 cost of the leader. More than a third of that could be saved by buying six rather than eight torpedoes and 150 rather than 190 rounds per gun (but retaining stowage for 190), and by reducing the reserve from 210 to 150 rounds per gun. The rest would have to come out of machinery. Similar figures applied to the destroyers. A slight further reduction could be achieved by taking torpedoes from stock rather than making them for the new ships.
In July 1927, in connection with questions of bridge size and ship’s equipment, Atlantic Fleet commander Admiral Sir Henry F Oliver declared the new destroyers far too large; numbers were far more important, particularly for torpedo attack since ‘the more targets which are presented, the smaller will be the percentage of losses’. Oliver repeated the point that high smooth-water speed was pointless. These expensive ships were ‘unarmoured cruisers without the main essentials of efficient signal and W/T communication and endurance to keep the sea’. Oliver appointed a three-man committee to investigate further. Commodore (D) W de M Edgerton and two Atlantic destroyer captains produced a list of detailed changes, including moving the bridge aft so that it could be reduced in height, and combining the director tower and the rangefinder to save bridge space. Controller Chatfield replied that ‘however desirable it may be … to reduce the size of destroyers, regard must be had to the vessels building for Foreign Service, and the British efforts to reduce the size were definitely rejected at [the disarmament conference in] Geneva.’ A single type had to fill a wide variety of roles. ‘The vessel therefore instead of being a Torpedo Carrier (as she is referred to by the C-in-C) is literally a small cruiser with a powerful armament, expensive fire control, great speed and endurance, high-angle guns and comfortable accommodation.’ He agreed with the DNC that displacement could not be reduced. The First Sea Lord agreed on 1 November.
The B class destroyers introduced a forward extension of their bridges (topped by a windshield in this 1939 view of HMS Bulldog). The extension carried a magnetic compass on a raised platform, the pelorus being about four feet further aft. It offered a superior view for the conning officer. The port side of the raised platform carried a chart table, and the starboard side a hooded table for the signalman. In later classes the compass was moved to the after part of the bridge and the extension was eliminated. The B class lost the bridge extensions early in the Second World War, but many destroyers retained theirs. On trials, HMS Bulldog made 35.452 knots on 34, 110shp (357.1rpm) at 1477 tons.
The C class finally had the full destroyer fire control system, including a director tower. It occupied a separate structure abaft the box-like bridge, as shown on board HMCS Restigouche (ex Comet). Note the exposed barbette of the director tower. The rangefinder in the C and D classes was a new three-man type (nine-foot UF 1) suited to high-angle as well as to low-angle targets. That meant that the line of sight could be elevated, but the main problem to be solved was that targets moved so rapidly that the rangetaker could not obtain accurate ‘cuts’. The rangefinder was therefore rate-aided: its prisms, set to an estimated aircraft speed and inclination, moved so that the rangekeeper could keep taking his ‘cuts’. This kind of adjustment was necessary because, unlike the US Navy, the Royal Navy did not adopt stereo rangefinders which could range more quickly on a target which was less precisely defined. Successful rangefinding (which was needed as an input into an antiaircraft system) thus required successful estimation of target speed and course; the system as a whole could not handle serious errors of estimation. In the ‘three man rangefinders’ introduced when destroyers were given some limited anti-aircraft capability, the three operators were rangetaker, layer (elevation operator), and trainer; a low-angle rangefinder required only a trainer and rangetaker. Visually, the three-man rangefinder had a thicker barrel because it needed the target speed and inclination adjustment elements. The open bridge sat atop the steering and signal house, the director atop the hut containing the chart house to port and the captain’s sea cabin to starboard. The open bridge carried a standard (magnetic) compass on a raised platform running down its centreline, with a chart table to port and an Asdic and signal table to starboard. At the fore end of the platform was a reflector showing the compass heading to others on the bridge. There were two torpedo sights (so the two sets of tubes could engage two targets) on either beam. In addition to the ship’s wheel, the level below carried the navigational plot (visible on the bridge via a view plot on the port rear side of the open bridge) and the remote control office from which the searchlight and torpedo tubes were controlled, following commands from the bridge. At the back of the structure were depth charge releases on either side. On trials, HMS Comet made 36.795 knots (mean) on 36,057shp (365.9rpm) at 1575 tons. Restigouche was photographed passing through the Panama Canal, 15 February 1939.
Displacement had already been shaved somewhat. The DNC and the E-in-C pointed out in mid-November 1926 that a 1280-ton (rather than 1350-ton) standard displacement destroyer could make 34.5 knots in standard condition (31.5 knots in deep condition) on 33,000shp, at a cost of £310,000, slightly above the Controller’s target of £308,000, but not taking into account the saving on ammunition. By late 1926, it seemed that more than enough money had been saved, the key change being a reduction of 1.5 knots in the destroyer and 1.25 knots in the leader; enough money was now left to make it possible to gain back one-quarter knot in the destroyer, so that all ships of the flotilla would have the same speed. Ultimately, the ships were given 34,000shp, which increased displacement about thirty tons.
With the sketch design settled in March 1927, Stanley V Goodall, later DNC, became the DNC destroyer section chief. He saw the design as little more than a warmed-over Repeat W; ‘it is submitted that EinC be again asked to do something better’. A hostile critic could say that nearly 200 tons had bought practically no advance in speed and no advance in armament except two extra torpedo tubes. When asked to tender, the private firms might well offer designs far better than that developed by the Admiralty, using more efficient higher-powered machinery. With three boilers, Amazon developed an average of 41,446shp during a six-hour trial and 42,193shp on the measured mile, despite a mishap to No 1 boiler. Surely two slightly improved boilers could produce 32,000shp. Goodall estimated that he could save ten feet on waterline length (to 310 feet), and make the same speed and endurance on 1560 tons rather than 1685 tons deep load, at an estimated cost of £304,000 rather than £326,000. He offered better watertight subdivision (the largest boiler room was smaller than in the existing design). Goodall’s sketch was dated 14 April 1927. It showed a single funnel, the uptakes from the two boiler rooms being trunked together.
The E-in-C rejected the two-boiler arrangement. When much the same idea was raised for the J class a decade later, he pointed out that larger boilers, with greater heating surfaces, took longer to gain power, hence the ship would accelerate more slowly. The cycle of boiler cleaning (necessary every twenty-one days of steaming or once each quarter) would be compromised, because ships would have only half-power while one boiler was being cleaned.
Looking forward to the beginning of new series construction in the 1927–8 Programme, in July 1926 Yarrow proposed building two ships in anticipation of Admiralty requirements.5 The firm wanted to test its proposed 400psi boilers. The Royal Navy would not have to agree to buy the ships until they were wanted, but Yarrow argued that they could supply valuable information for the projected 1928 Programme. Both the E-in-C and the DNC favoured the idea. The Controller considered it comparable in theory to the 1912 Programme of ‘speculative’ destroyers to speed construction. Responding to the Controller, the E-in-C and the DNC took Yarrow’s proposal to mean that its new experimental destroyer should help shape the 1928–9 ships (ie, those to be laid down about 1 November 1928). On that basis the experimental destroyer had to be ordered by 1 August 1926, assuming no work stoppages and a twenty-one-month building time.6 The idea was referred to the Board. Yarrow admitted that the higher pressure it had in mind would not reduce machinery weights, but it hoped to achieve 10 per cent better economy at cruising speeds. Later, Yarrow claimed that an Ambuscade with the new machinery would make 6500nm rather than 5000nm at eleven knots, with an endurance of 4500nm at fifteen knots or 4150nm at sixteen knots, all considerably better than existing ships. Such a ship would cost £277,500 compared with £274,000 for Ambuscade. The primary objective was to gain, reasonably economically, information as to the practicality and possible advantages of higher steam pressures and temperatures. The firm noted that in specifying the fuel-less state for standard displacement, the Washington Treaty had considerably (but not entirely) devalued fuel economy for larger ships. However, because ships would not have to carry so much fuel, they might achieve higher speeds (or make current speeds with less power). The E-in-C therefore considered the experiment worthwhile.
Codrington INBOARD
HMS Codrington was the first postwar British destroyer leader, intended to lead the A class. Like the destroyers, she had three boilers in two boiler rooms. Periodically there were calls to adopt larger boilers so that the number could be cut to two and their uptakes trunked into a single funnel. One counter-argument was that ships often had to shut one boiler down for maintenance; a ship could operate much better on two-thirds power than on half power. Codrington operated at the usual interwar Admiralty steam conditions: 300psi. The Admiralty experimented with higher steam conditions in HMS Acheron, but she seems not to have been very succesful. Codrington was designed to make 31.25 knots deeply loaded (2012 tons); on trials she made 37.739 knots at 39,257shp at a starting displacement of 1674 tons (standard displacement was 1520 tons). Like the A class, Codrington did not have the planned automated fire control system intended to give British destroyers long-range gun capability (it was introduced in the C class). However, Codrington was provided with a transmitting station (20), to house her gunnery calculating instruments, and eventually her fire control computer (an Admiralty Fire Control Clock Mk I – AFCC). However, she did not receive the DCT which usually complemented it; instead, as late as 1938, she had a Repeat W type director Mk V. Plans called for a high-angle (sixty degree) gun in the B position, as shown, and the ship was given a somewhat higher bridge to clear it). On trials, however, the gun could not retain its high elevation, presumably because there was not enough counterweight. Codrington was the only post-First World War five-gun leader not to have a blast shield to starboard of No 3 gun. The usual 2-pounder pompom (two, side by side) is shown abaft No 2 funnel. The ship also had four 0.303in Lewis guns, but they are not shown. She had a hydrophone room (19) rather than an Asdic room, although she was designed to have Asdic rather than a passive hydrophone. She was designed with a single depth-charge rack, but was completed with a typical First World War battery of four depth-charge chutes and two throwers. The two main turbogenerators (forty kilowatts) were in the boiler rooms. An additional paraffin-powered twenty-kilowatts generator provided harbour service power. There was no interest in a US-style diesel emergency generator. The crow’s-nest shown here was not fitted. On trials, Codrington made 37.739 knots on 39,257shp (362.4rpm) at 1674 tons.
(DRAWING BY A D BAKER III)
Delayed by an internal Admiralty debate over whether the project was barred by the Washington Treaty (it was not), the planned ordering date slipped by. Yarrow was testing high-temperature high-pressure machinery in its own experimental ship (King George V, with 575psi boilers), and in mid-October the Controller suggested that any decision should await their outcome. He would defer to May 1927 any decision as to whether one or more of the 1927 destroyers should have high-pressure high-temperature boilers. New Staff Requirements would make it impossible for Yarrow simply to duplicate Ambuscade except with new boilers. The Chief of Naval Staff suggested further that to lay down ships outside the declared building programme ‘would create natural suspicion in the hearts of foreign naval powers’. By this time (November 1926) the League of Nations was already preparing for its abortive 1927 (Geneva) disarmament conference. Late in November 1926 Yarrow’s proposal was rejected, but the Admiralty was willing to consider ordering destroyers with the company’s new machinery once its own steamer trials were complete. In June 1927, the E-in-C suggested that, when tenders were invited for the 1927–8 destroyers, Yarrow be asked to submit alternative high-pressure (and air preheated) designs. The DNC agreed. For its part, Yarrow reported some important orders for liners with high-temperature high-pressure boilers.7
The DNC presented the sketch design to the Board on 31 October 1927. Thornycroft asked to submit its own design. The DNC pointed out that the hull and equipment of HMS Amazon offered nothing particularly new, and that forcing all builders to use the same Admiralty design would make for considerable savings. If Thornycroft were allowed to offer its own design, surely other builders would follow suit. The E-in-C pointed out that firms already had considerable latitude in machinery design. Yarrow had already been told that they could submit an alternative design. The Director of Contracts suggested that, if need be, a case could be made out for treating Yarrow and Thornycroft differently from other firms because they had built the two experimental destroyers. The Controller called a conference with the DNC, the E-in-C and the Director of Contracts.
Prewar, the practice was usually, it was said, to allow Yarrow and Thornycroft to submit their own designs as well as tender for Admiralty designs. That made sense when speed was steadily increasing, but as a consequence the Royal Navy never had really standard types. Given war experience, the Admiralty now felt confident to define Staff Requirements, and there was less scope for experimentation. Thornycroft’s offer was rejected on the ground that experimental cruises by Amazon and Ambuscade were still in progress. No further experimental destroyers were needed until they were completed and the results examined. As nearly as possible, all ships of the A class would be sister ships.
Invitations to bid were due to go out to fifteen firms on 1 November 1927. The design actually received the Board stamp on 3 November. Thornycroft and Yarrow were invited to offer alternative high-pressure (400psi; 200° F of superheat) machinery designs. Parsons (with hull and boilers by Thornycroft) offered more (500psi; 750° F). The E-in-C wanted three to four years of sea experience before trying such conditions, but in the end this proposal was adopted (the ship was HMS Acheron). Yarrow and White were both rejected as too expensive. The other orders were distributed so as to avoid excessive concentration on the Clyde.
Despite the Staff Requirement, the ships had thirty-degree mountings for their 4.7in QF guns. A sixty-degree CP XIII mounting was designed for the A class. By November 1928, it was being used for proof firing at Shoeburyness, presumably prior to a planned sea test on board the leader Mackay. It developed a fatal defect: it ran down in elevation on firing. Eighteen months of an attempted cure failed, but by mid-1930 it seemed that a cure was in sight (reduced-speed elevation gear). Thus this gun slipped from the A class to the B class.
The corresponding leader entailed similar requirements, except that she would have an additional 4.7in gun, a larger bridge, and increased accommodation (as estimated in March 1927, complement was 190 compared to 145 for the new destroyer). The ship was not fitted with the TSDS. Work on a sketch design began in January 1927. Development roughly parellelled that of the destroyer, including the important discovery that not nearly as much oil fuel was needed (as little as 350 tons instead of the 530 tons originally expected). Like the destroyer design, the leader design was presented to the Board on 31 October 1927. The leader was HMS Codrington.
The US government convened a new naval arms conference at Geneva in 1927, the object being to stop the developing race in cruiser construction. This conference was also the outcome of a League of Nations disarmament initiative begun no later than 1926. The British hoped to limit both cruisers and destroyers, and also to bar submarines – although that was recognised as unlikely. The Admiralty position guaranteed a sufficient destroyer force, while limiting the size (hence cost) of individual destroyers. The proposal aimed at displacements near those of existing British destroyers: 1750 tons for leaders and 1400 tons for destroyers, with a maximum gun calibre of 5in. The Admiralty particularly wanted to curb what it saw as the tendency of destroyers and leaders to develop into small (hence expensive) cruisers, limiting destroyer construction so as to leave money for vital trade protection cruisers. Unfortunately different navies had radically different requirements. Focused on the Far East, the British saw destroyers primarily as elements of an integrated battle fleet. They did not expect any repetition of the fights in the Channel, in which destroyer gun power had been so important – and for which Germany had built oversize destroyers which were nearly light cruisers. France and Italy, however, envisaged exactly such combat in the Mediterranean, hence had every interest in building oversize destroyers or undersize cruisers. The British also hoped that the number of destroyers needed by each power could be reduced if submarines could be limited or eliminated altogether. To the British it was perfectly logical to limit submarines (the antidotes to capital ships) if capital ships themselves could be limited.8
The conference collapsed, but hopes of extending arms control survived. The next effort was the 1930 London Conference.
On 9 November 1927, Canada informed the British government that it planned to build two destroyers in the United Kingdom. Two Canadian officers examined the plans of the Acasta class on 27 February 1928, requesting minor changes, including a streamlined bridge and oil heating. The Canadian High Commission requested tenders on 4 June 1928. Thornycroft replied on 31 July, but on 24 September offered its own design.9 It offered a maximum speed of thirty-five knots, endurance of 5000nm at twelve knots, heavier scantlings, and a deep displacement of 1600–1700 tons. Thornycroft wrote Stanley Goodall, then Deputy DNC in charge of destroyers, that the design closely followed the A class except that it was four feet shorter (because machinery was more compact) and power was reduced to 32,000shp. The bridge was streamlined, as Canada wanted, and all cabin entrances were inside the deckhouse, a valuable feature in cold weather. Machinery would not incorporate any superheaters. Thornycroft’s designer K C Barnaby was ‘afraid we shall have our work cut out to approach [A class performance] with less power on a shorter and relatively heavier ship’. Contract speed was thirty-five knots at 1450 tons; designed deep displacement was 1750 tons.
The DNC was responsible for testing and approving the ships. At a February 1929 DNC department meeting, Barnaby explained that his estimate was based on the middle of a six-hour trial beginning at the contract displacement. At mid-trial the ship would probably displace 1380 tons, so she would exceed thirty-five knots. A quick calculation showed that the ship would need 17,600ehp to reach thirty-five knots at 1380 tons, and the necessary propulsive coefficient of 0.55 seemed reasonable. However, Goodall pointed out at the meeting, that Barnaby’s displacement was based on the 170 tons load specified in the contract for HMS Amazon; for this ship the equivalent would be 190 tons – and Barnaby doubted he could make the speed with the extra twenty tons. He ended up accepting 180 tons. On trials (1 August 1930), Saguenay made 35.364 knots on 36,417shp at 1405 tons; her sister made 36.08 knots on 35,447shp at 1406 tons.
The ships, hmcs Saguenay and Skeena, had the usual British destroyer armament of the time, four 4.7in, two 2-pounder pompoms, four Lewis guns, and two quadruple torpedo tubes. They could be distinguished visually mainly by their streamlined upper bridge fronts.
The 1928–9 destroyer (B class) was a modified repeat version of the 1927–8 Acasta class. Changes were worked out at the Controller’s meetings in July 1928. Future destroyers would have four 4.7in QF guns and, if successful, quintuple torpedo frames (not tubes). The quintuple frame was a new departure in torpedo launching design, trials of one element of which began at Horsea about November 1928. The question of fitting fire control tables (ie, computers), as in the experimental destroyers, would be further examined. The question of fitting a high-angle gun would be deferred until further investigated by the Staff, but the ships would be stiffened to take it. However, no additional ammunition would be stowed. The ACNS would decide whether to fit a proportion of destroyers to make smoke. Endurance would not be changed, but stores capacity would be ten weeks rather than four months. Radio requirements would be further studied.
The Canadian Saguenay and Skeena were in effect equivalent to the A class. These embodied the modest streamlining which was then being proposed for (but not adopted for) Royal Navy destroyers. Note the bulkhead extending all the way to the side of the ship, with the door for internal access; these ships had entirely internal access for their superstructures, HMCS Saguenay is shown. The sequence of early war modifications was different in the RCN from the RN; these two ships had their after torpedo tubes replaced by 12-pounder high-angle guns before their after funnels were cut down.
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The Beagle design was presumably associated with a long Naval Staff memorandum on destroyer requirements produced during summer 1928.10 Looking at fleet requirements, the Staff pressed for the smallest possible ship, because smaller size offered better manoeuvrability, less vulnerability to gun fire, a greater chance of surprise in a night attack, and greater overall numbers. In any case it was undesirable to exceed the 1500 tons the British government was trying to make a treaty limit. The Staff concluded that smaller size would be helpful in all other destroyer functions. The outcome of the summer conference was a series of accepted destroyer Staff Requirements. Further conferences presided over by the CNS (ie, First Sea Lord) were held in July or early August 1928. The C-in-Cs were asked whether the Staff Requirements were too high, and, overall, opinions indicated that ships should not be allowed to grow, and two called for smaller ships.
In August, the Controller (Rear Admiral Pound) asked Goodall if the after 4.7in gun could be replaced by a third quadruple tube, and what the effect of eliminating it would be on displacement, speed, cost, and maintenance load. Goodall estimated that twenty tons would be saved. It was roughly equivalent to a quarter knot, but the ship would trim by the bow, and that increase would be lost. The gun could be replaced by a third set of tubes, but in that case it would be difficult to work TSDS, and sweep winches would block transport of torpedoes along the deck to the tubes. There would also be blast problems from the X gun.
This possibility having been abandoned, by late August the ships were expected roughly to match the A class, with four thirty-degrees guns (but with motorised bollards for ammunition supply). Number 2 mount was given supports sufficient for a sixty-degree mount if desired. However, the earlier provision for stowage for extra rounds for this mounting was omitted. By this time, the fire control system in the Amazons had been approved for future construction. The Acastas had had no such provision. The earlier ships’ TSDS was omitted in favour of Asdic (Type 119) and a full depth charge battery for five-charge patterns: a depth charge rail, two throwers, and three ready-use charges in a rail (total capacity was fifteen charges). Initial lists of armament (so that complement could be estimated) showed quintuple torpedo tubes. However, on 31 August, the DTM pointed out that even if trials scheduled to begin in two to three months were successful, drawings would take another four to five months, and manufacture another fifteen to eighteen. This tight schedule allowed for no sea trials, but so new a concept absolutely required them. He therefore recommended that the 1928 destroyers have the same quadruple tubes as their predecessors.
When it was decided to eliminate the fire control computer and DCT in the A class, the question arose of fire control in the B class. The DNO proposed to fit a DCT given the ‘generally satisfactory results obtained’ in the two prototype destroyers. Fire control would generally be on the lines of the repeat W class ‘but embodying such refinements which will improve the automaticity of the gear … it will probably be necessary to accommodate a Director Sight Setter in the DCT, which may entail a slight increase in diameter of the DCT over that fitted in Amazon’. The DGD now suggested that space might be available in the Transmitting Station below decks for a fire control table ‘of similar size to that in Amazon and Ambuscade’. The DNC pointed out helpfully that the tendering drawings could show a DCT of the same size as that in Amazon. The W/T comprised a main office (Type 38), a second office (Type 44), and a fire control W/T office (Type 31), the latter needed to maintain concentration firing. The DNE pointed out that the Acastas would probably need both their forty-kilowatt generators in action, so the new design was given two fifty-kilowatt steam units.
The DNC presented the new design (for very nearly a repeat A class, with the same displacement, dimensions, and form) to the Board on 11 October 1928. The main difference was that the DNC proposed to use the same hull for the leader, substituting the necessary offices for X 4.7in gun. Accommodation was provided for the officers and men of a leader except for four officers and one rating, who would be accommodated on board other destroyers of the flotilla. The idea was to make the leader tactically identical to the destroyers of her flotilla. The Board approved the legend and drawings on 18 October.
Boreas
The B class destroyers were essentially a repeat A with Asdic rather than TSDS. HMS Boreas is shown in March 1931. She had a short depth-charge track but was later fitted with two throwers, to produce a five-charge pattern (two from the throwers, three from the track). By 1939, the standard was a total of thirty charges, for six patterns. The ship’s bridge shows her rangefinder and her simple First World War-type destroyer gun director, but before these ships were designed plans called for an elaborate (‘automatic’) fire control system employing a computer in a transmitting room in the bridge structure and a director control tower (DCT) atop the bridge. Progress was slowed by the failure of the Barr & Stroud system installed on board the two prototypes. In addition to the weapons visible here, the ship had five 0.303in machine guns. D and later classes had quadruple 0.5in machine guns instead of the single 2-pounder pompoms. Note also the semaphore on the bridge wing (signal deck) and the signal light atop the bridge structure. On trials, Boreas made 35.78 knots at 35,398shp (357.8rpm) at 1450 tons, HMS Boreas was transferred to the Royal Hellenic Navy in April 1944 as RHS Salamis, returned in September 1951 and broken up at Rosyth in 1952.
(drawing by a d baker iii)
The Asdic in the Beagle class was effectively the first British production installation. Earlier experimental installations were controlled from below, the Asdic bearing being provided to the bridge by voice pipe. One of the two operators trained the oscillator, the other listening for pings. Range was taken either by stopwatch or by an automatic recorder and transmitter with a bridge repeater. Given the automatic readout of bearing on the bridge, it was suggested that the oscillator might also be trained (electrically) from the bridge. In any case it was understood that individual readings were not enough: Asdic detections had to be plotted so that the course of the submarine could be worked out. The test ship Torrid used an automatic plotting board, but initially the Beagles would use manual boards.
On 22 October, before invitations to tender went out, Yarrow asked that, for the next destroyers (the 1928–9 series) it be allowed to offer a two-boiler design. This was much what Goodall had proposed for the previous class. The E-in-C commented that the advantages Yarrow offered would probably be offset by unacceptable disadvantages from a machinery point of view. Yet that firm’s special expertise would justify special treatment, so he proposed to inform them that the Admiralty would be glad to see their alternative design. The DNC was more positive: Yarrow might save about twenty tons in machinery weight and fourteen feet in machinery length, giving badly needed additional space, particularly for accommodation forward of the forward boiler room bulkhead. When they tendered, Thornycroft and Yarrow both offered two-boiler leader designs, the space freed being used to add a fourth 4.7in gun. The DNC commented that Yarrow’s fourth gun was badly placed, and it added fuel whose weight would reduce speed. Thornycroft offered five guns (one badly placed), substandard accommodation, insufficient stability, and insufficient speed. However, the DNC concluded that it would be possible to design a two-boiler leader with the same tactical properties as the destroyers, but also with the standard of accommodation provided in Codrington (but with some personnel distributed among the flotilla). He suggested sending his sketch to Thornycroft and Yarrow and asking them for revised designs. The DNC pointed out that destroyers usually cruised on one of their three boilers, offering them sufficient steam for about eighteen knots; with the larger boiler, they would have steam for up to 24–25 knots, albeit less efficiently.
The E-in-C was less enthusiastic about two-boiler designs, and for technical reasons doubted that either design offered was suitable for adoption. The Royal Navy was about to test a larger boiler itself, with considerable implications for future construction.
A January 1929 programme put forward by the DNO for development of a destroyer fire control system, showed design beginning in March, tenders for a trial table (computer) issued in March 1930, and the trial table completed in July 1931, the first production table being delivered in July 1932. Production could not begin before thorough trials at HMS Excellent. The Controller (Admiral Backhouse) fully supported the project, but cautioned that the equipment had to be kept simple. He backed the proposed Admiralty table over any privately designed one which might cost more than twice as much (£10,000 compared with £4000). The ACNS, Dudley Pound, commented that the Repeat W gear planned for the A class ‘does not meet requirements for the efficient control of the powerful gun armament carried by a modern destroyer’. However, the planned Admiralty Fire Control Clock (AFCC) would not be ready until the next (1930) class. The alternatives for the B class were the Barr & Stroud table (computer) of the two prototypes and the Repeat W system. At a 2 July 1928 conference, the Sea Lords decided that, if further trials of the prototypes were successful, Barr & Stroud tables should be supplied to a complete flotilla for further trials. In the meantime, the DNO should explore a simpler alternative. As of January 1929, no report of the prototype trials had been received.
In July 1930, it was proposed to fit the prototype sixty-degree gun to HMS Keith in No 2 position, with the extra one hundred rounds of high-angle ammunition previously planned for the A class. Then HMS Bulldog, the last of the flotilla, was chosen (Blanche was chosen but rejected). Tests were unsuccessful. The DNO concluded that the best he could do was a forty degrees mounting (CP Mk XVII), which was adopted in the E class (1931–2 Estimates).11
The 1929 leader Keith was conceived as a three-gun version of the B class. At a Board meeting, the First Sea Lord explained that seagoing officers considered existing leaders too large, and that during exercises the additional speed of the leaders had not been necessary; moreover, the ships’ larger turning circles were proving inconvenient. At his behest in July 1928, ACNS Dudley Pound asked the DNC if leader facilities could be provided on Acasta displacement, without any loss of habitability or speed. He suggested eliminating Y 4.7in gun, as was done. The Captain (D), the flotilla commander, had a staff of six officers and twenty-one ratings, but some did not have to be accommodated on board the leader. In addition, the ship needed a taller mast for W/T aerials, a second W/T office, a slightly enlarged main W/T office, a remote control W/T office on the open bridge, slightly more office space, a slightly larger bridge for plotting and for the Captain (D)’s staff, and a faster motor boat. The DNC’s destroyer chief (Goodall) considered the project entirely feasible, the ship gaining about eight tons. The idea was soon approved. The sacrifice of two 4.7in guns (compared to earlier leaders) seemed acceptable, and £30,000 would be saved (not to mention personnel costs).
In June 1930, the question arose of mounting a fourth gun in Y position, presumably after changes to the 1929 leader made that possible in that ship. The DNC pointed out that in that case she would have no space for the desired Staff Office, as the after superstructure was of minimum dimensions and space on lower deck aft was fully taken up for accommodation. That seems not to have mattered. The Board approved the change on 11 July 1930. Vickers was instructed to make the modifications, the change payment amounting to £5230. The ship gained twenty-eight tons.
The design process began with an August 1928 round-robin addressed to the two main fleet C-in-Cs, Rear Admiral (D), C-in-C Portsmouth for Director of Senior Officers’ Technical Course, and Director of the Royal Naval College elicited no great proposals to change the 1928 design (B class), and even reaffirmation of the four-gun policy. One question was whether one gun should be provided with forty (not sixty) degrees elevation for high-angle fire. The addressees were in favour only if nothing else was sacrificed. The Naval Staff pointed out that higher elevation angle entailed extra weight and might impair low-angle fire (trunnions had to be higher, so gun crews had to raise their ammunition higher at low angles). For fleet work, low-angle fire was primary. However, destroyers had other roles. Those escorting convoys or conducting subsidiary operations would surely have to supply long-range anti-aircraft support. ‘Even as long ago as the Dardanelles operation destroyers were forced to reverse their 12-pounder mountings in order to obtain as much high angle elevation as possible and development in the air is still proceeding rapidly.’ The C-in-C Atlantic Fleet rejected leaders whose armament was inferior to the destroyers they led. Some flotilla commanders doubted that a standard destroyer was large enough to administer a flotilla when in harbour and to lead it in battle.
HMS Crescent (later HMCS Fraser) is shown as completed. The two tall masts in these ships were needed for their long-wire (flat-top) radio antennas. Between the funnels is the standard pair of single 2-pounder anti-aircraft guns. Note the galley uptakes on either side of the B gun deck. On trials, HMS Crescent made 36.345 knots on 36,450shp (376rpm) at 1518 tons.
The C class destroyers were TSDS ships, HMCS Ottawa (ex-Crusader) shows her standard TSDS gear and her limited depth-charge battery (as built). Barely visible is the massive starboard winch, roughly abeam her after deckhouse, used to handle the paravanes. The big vertical cylinders are standard smoke floats.
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The split between Asdic-equipped destroyers with fifteen charges and TSDS ships with six was affirmed, the Staff commenting that fifteen was the most a fleet destroyer could carry. ‘Special submarine killers may be necessary for convoy escort work to carry 40 charges, and this could be arranged for.’ The question of providing smoke equipment was controversial; existing policy was to fit two destroyers per flotilla.
The C-in-C Mediterranean thought that destroyer guns need not range beyond 12,000 yards, which required seventeen degrees elevation. The Staff wanted a ten degrees margin against roll, so the mounting had to allow for at least twenty-seven degrees. The existing thirty-degree mounting seemed suitable, so it was retained. Against suggestions to reduce ammunition supply, the Staff pointed out that during the war destroyers found themselves carrying more ammunition after some destroyers exhausted their magazines in prolonged fights (eg, at Heligoland, at the beginning of the war). With the introduction of concentration firing, ships were opening fire at longer ranges and sustaining it longer. In a Far East war, too, it would be best for ships to carry as much as possible with them.
A report from the Mediterranean showed that the Barr & Stroud fire control table was too complicated and delicate and had proved unreliable. The C class introduced a Vickers-developed Admiralty Fire Control Clock (AFCC) and director control tower (DCT) combination. To accommodate it, the bridge structure was split lengthwise, the forward element being the steering and signal house, with the open bridge on top. A separate structure slightly abaft this house contained, among other things, the chart house. Atop this were the DCT and the separate rangefinder, the DCT rising from a prominent barbette. This arrangement seems to have been set in a November 1930 sketch (the 1929 sketch design showed no such separation, nor did it show the DCT). The AFCC proving successful, it was installed in modified form on board A and B class destroyers (as AFCC II), but they could not accommodate a director control tower, with its automatic feedback to the AFCC. Instead they retained modified W class directors.
This sketch seems to have been prepared initially for the 1929 leader Kempenfelt and for the 1930 leader then being designed. In the course of detailed design, the bridge was lowered about 2ft 6in. It embodied some new requirements, such as a view plot (a glass through which the main plot below could be seen and in effect reproduced) on the upper bridge, Lewis guns on the lower bridge, and better signalling arrangements on the lower bridge, including more flag lockers and more space for signalmen. The same revised bridge was planned for the 1930 leader, so it incorporated an antisubmarine plot on its starboard side (not needed in Kempenfelt, which had no Asdic). In Kempenfelt, space was made on the port side of the upper bridge for a remote control W/T hut near a separate central signalling station (in Keith the remote control hut was on the level below the upper bridge). The chart table was placed protruding from the fore side of the bridge specifically to clear space for the remote control hut and for other functions such as Asdic control. Originally plans had called for placing the remote control hut on the level below the open bridge, but the Controller forced reconsideration, because the hut might have blocked one of the best lookout positions on the bridge; he wanted it at an after corner or between the ladders aft amidships.
Kempenfeit was leader of the C class. In 1939 she became HMCS Assiniboine. She had four rather than five guns, and was comparable to a destroyer rather than to a large leader.
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The Tactical School suggested a common hull which could carry alternative armaments, a theme which would be revived during the Second World War. It seemed that had already been done in the wartime V class, built as a fleet destroyer but suited to conversion for minelaying when the Y gun was landed. Destroyer officers disliked this idea on the ground that ships could not efficiently be designed for alternative batteries. Admiralty policy held that ships should be designed and built with the armament required for work with the fleet. Any changes would come when ships were relegated to subsidiary roles – and they would be permanent. The Royal Navy would continue building a single type of destroyer. Late in February 1929, ACNS Dudley Pound concluded that the Acasta class should be repeated; he saw no point in the sort of improvements the Sea Lords had recommended a few months earlier.
The Controller came back to guns, commenting that ‘it might be said with practical certainty that in any war the gun will be the most used part of their armament’. The three-gun leader made no sense; ‘it has been recently agreed in regard to Cruiser design that the number of guns is of predominating importance’. The Controller (Admiral Backhouse) was most concerned with endurance, which had to be enough to keep the destroyers with the battlefleet.
They would doubtless have sufficient endurance for normal Mediterranean operations or for employment from Home Bases, but take them further afield and endurance will then become a vital factor. Destroyers are an almost indispensable adjunct to any battlefleet now, and will remain so whilst Submarines continue to exist. For a Fleet action, a fleet without destroyers would be at a serious disadvantage if the enemy fleet possessed them.
For Backhouse, the replies to the round-robin stressed the tactical side of the question, but the strategic side (eg, endurance) was far more important. No one set a figure for endurance. Backhouse suggested 4000nm at fifteen knots, but would prefer more. All liked higher speed, but Backhouse wanted that justified by a definite margin over the battlefleet, say 50 or 60 per cent. The other justification for speed was that needed for subsidiary operations in areas such as the Channel or the Mediterranean, having regard to the speed of possible enemy ships. This speed would exceed that set by the fleet, ‘but it is well known that no destroyer has ever yet had too high a speed for exceptional occasions, which actually are those which occur in action – Fleet action or Destroyer action’. So the tendency should be to increase speed.
As to building multiple types, Backhouse recalled that in wartime the Royal Navy ‘could quite well build convoy destroyers, anti-submarine destroyers, or fleet destroyers or any other type as we need them’. He accepted that the Acastas, which he considered large expensive ships, were needed to meet the requirements, but ‘if large numbers are required, we should have to build some of smaller type with simpler equipment’ – like the Second World War Hunt class.
Given this desire for extra endurance, on 7 February 1929, the Controller asked the DNC to estimate the effects of increasing endurance to 4000nm or 4500nm at fifteen knots, increases of one or two sevenths over the earlier 3500nm. He hoped to place orders in mid-1930. The DNC wanted general features of these designs settled six weeks before tenders were invited, that is, about the end of 1929. Increasing endurance of an Acasta to 4000nm would require about fifty more tons (ten feet longer; £6500 more); another 500nm would cost another ten feet (sixty tons) and total increase would be £20,000. The DNC did not submit this report, because he disliked lengthening such ships, as that would cost manoeuvrability. The alternative was to provide deeper tanks. The ship could reach 4000nm if the lower deck was raised about a foot and peace tanks were added in No 1 boiler room. The overall depth of the ship would increase one foot, and beam would have to increase three to six inches to maintain stability. Standard displacement would increase forty tons, and speed would fall by 0.3 knot at standard and by 0.65 knot at full load displacement. In April, the DNC destroyer designers calculated speeds for a variety of 326-footers (beam 32ft 9in) with 36,000shp plants. The existing design (1330 tons standard, 1800 tons deep) could make thirty-two knots at deep load and 36.5 knots at standard. A 333-footer (1350 tons standard and 1850 tons deep) could make as much as 37.2 knots at standard displacement and 32.6 knots deep (depending on propeller efficiency).
In defence of the proposal to ask for private designs, the Controller cited Yarrow’s design for Dutch destroyers, two of which had attained thirty-six knots on trials (1503 tons);12 endurance was 5000nm at fifteen knots. These ships displaced 1600 tons with 330 tons of fuel on board, and had 33,500shp (three-boiler) power plants. The Controller was impressed by the high speed the Dutch ships attained with less power than an Acasta, and with their great endurance on a moderate displacement. Yarrow claimed that these virtues were ‘obtained by careful design and construction, which in their opinion justifies some weight saving, and by more economical machinery installation’. Although probably they did not meet British standards, and their endurance might be optimistic, it seemed very much in the Admiralty’s interest to keep abreast of the progress they seemed to represent.
Staff Requirements had to be settled by the end of April in order to prepare the necessary sketch design for tendeing. On 19 April 1929, the Sea Lords, the DNC, the E-in-C, and various staff officers met to discuss destroyer policy. Hopefully the new Admiralty design would be ready for the 1930 ships. The other questions were endurance, speed, and whether private firms should be asked to submit tenders.
The DNC thought ten feet a reasonable price for 500 extra miles’ endurance, and the DCNS considered it well worth the additional price. The Controller and the First Sea Lord both agreed; the Staff Requirement endurance was increased to 4000nm at fifteen knots (in another context, Goodall later wrote that this figure was based on very conservative assumptions, and that trials with the prototypes suggested that actual endurance might be 5000nm at fifteen knots). The Controller made the further point that although destroyers could increase their effective endurance by fuelling at sea, it would be better to have fewer, longer-legged, destroyers and not to invest in fleet tankers. The question of speed was linked with that of allowing private firms to offer alternative high-speed designs. The First Sea Lord saw little point in having two fast destroyers built by private firms; better to get a half-flotilla which could work together. The Controller wanted to produce a sketch design, and then ask the specialist firms for their own designs. Size should not be allowed to increase. The Controller was authorised to approach Thornycroft and Yarrow for their own designs.
The D class destroyers were essentially repeat Cs with the space between director and bridge structure plated in. HMS Daring is shown in 1933. The small projection from the bridge face is a chart table. On trials, HMS Daring made 37.852 knots on 35,788shp (364rpm) at 1460 tons.
The E class destroyers were essentially repeat Ds, distinguishable, if at all, by the more massive supports for their chart tables. The galley chimney on the forefunnel was for the main galley, that aft (alongside X gun) for the officers’ galley in the after deckhouse. Eclipse is shown in dark Home Fleet grey. Note her TSDS fittings aft. On trials, Eclipse made 37.561 knots on 36,093shp (361.2rpm).
Both the DNC and the E-in-C ‘were prepared to increase the horsepower considerably without adding to the displacement’. They concluded that adding 5000shp would give a speed of thirty-three knots at deep displacement. Greater efficiency (without more horsepower) would not add speed in the near future. For the ACNS, destroyer speed was set by the speeds of the cruisers and carriers with which they operated; they needed a one-knot margin (these ships were rated at 30.5 knots). This reasoning had justified the existing 31.5 knots requirement. Gaining another two knots would cost £45,000 per ship, about half a million pounds in a flotilla currently costing about £2¾ million. For First Sea Lord, that was too much. The DNC ended up promising 4000nm and thirty-two knots for a ship ten feet longer than an Acasta. These figures were accepted.
The conference seemed to accept the three-gun choice reflected in Keith; destroyer officers were willing to dispense with one of their four guns. The DNC pointed out that in a ship lengthened by ten feet it might be possible to fit in a fourth gun in a leader. The characteristics of the big foreign leaders seemed irrelevant, as they were practically light cruisers. The conference asked the DNC to try to gain back the fourth gun in a leader of the same length as the destroyers. The Controller remarked that destroyers needed strong gun armament; was the 4.7in powerful enough, when foreign navies were using heavier weapons? The ACNS was assigned to have the staff compare 5in and 4.7in guns.
A 2 May 1929 legend (Board-stamped on 3 June) showed a 318-footer (compared with 312 feet for an Acasta or a Beagle, ie, lengthened six feet rather than the planned ten feet; later this was cut to 317ft 9in) with slightly more beam (32ft 9in rather than 32ft 6in), displacing 1370 tons (later 1375 tons) rather than 1330 tons, with 36,000shp engines rather than the earlier 34,000shp. Total oil capacity was 470 tons, compared to 380 tons in the earlier ships. Because the new flotilla followed the Asdic-equipped B class, it would have TSDS and three depth charge chutes (this decision seems to have been reached specifically for the 1929 ships, and it would be reviewed for each later flotilla).
The DNC pointed out that in addition to Thornycroft and Yarrow, White had recently built successful ships for foreign buyers (presumably meaning the Argentine Mendoza class). Substantial savings in the ships freed as much as £20,000 each for four privately designed ships. This initiative was abandoned some time before 9 November 1929.
The associated leader was HMS Kempenfelt. Answering the round-robin on destroyer characteristics, the C-in-Cs Mediterranean and Atlantic fleets both wanted leaders to be faster than destroyers and no less well armed. In March 1929, the Controller asked the DNC and the E-in-C whether they could offer about two knots more on roughly Acasta dimensions. The DNC’s destroyer expert Goodall produced a table showing that a 325-foot ship producing 39,000shp (as in Codrington) could make thirty-seven knots at standard displacement and thirty-three knots at deep load. Stretching the ship to 330 feet would gain half a knot at deep load (but nothing at standard displacement). The same results could be achieved with 41,500shp on a length of 325 feet or with 40,000shp at 328 feet. The 325-footer would displace 1353 tons standard and 1790 tons fully loaded; the 330-footer, 1450 tons and 1895 tons, respectively. Goodall commented that extra leader features such as additional wireless and accommodation would generally add twenty tons to the ship’s load. It would be easiest to retain the stretched after deckhouse and insert the fourth gun between the funnels, as in Codrington (which had a fifth gun in Y position). The DNC approved this rather awkward arrangement and asked for a sketch design using the same machinery as the destroyer. Although the Controller wanted at least destroyer speed, the ship would either need slightly more power or would suffer a slight loss of speed. Meanwhile the destroyer herself was being stretched by six feet, offering just the extra length that might accommodate a fourth gun in a leader. Some weight was saved by not fitting TSDS (as in Codrington). The DNC offered the Board destroyer dimensions but more crowded accommodation, but that had been accepted in Codrington.
As presented to the Board (and as built) the 1929 leader had her four guns in the conventional A, B, X, and Y positions, without any gun between the funnels. As designed the leader would draw slightly more water than the destroyer, and would displace more (1390 tons rather than 1375 tons, in a legend dated November 1929), so she would be slightly slower. The sketch design was approved the same day as that for the destroyer, 3 June 1929. At this stage, displacement was given as 1390 tons; speed would be 35.5 knots in standard condition (half a knot slower than the destroyer), thirty-two knots deep load (as in the destroyer). In July 1929, the E-in-C proposed to substitute a diesel generator for the gasoline set used in earlier destroyers. A Benz diesel (made by McLaren in the UK) was finally reliable enough, and it was coupled with a thirty-five kilowatt generator (somewhat larger than needed, but the only available engine produced 60bhp, equivalent to forty-five kilowatt). It was fitted in the forward boiler room in place of the usual twenty-kilowatt gasoline unit on the upper deck.
Such ships could hardly match foreign super-destroyers. The DNC asked for designs of larger leaders, which give some idea of what could have been done. Goodall tried power plants with four (56,000shp) or five (65,000shp) Codrington boilers. A ship with Codrington armament but with the first power plant would make thirty-four knots deep and thirty-eight knots in standard condition. She would compare in speed and armament to the Italian Vivaldi, but would be larger and more expensive because she would be carrying much more fuel. That was not too impressive, so Goodall offered three alternatives armed more like the French super-destroyer Guepard, which had 5.5in guns. All were the same size and speed (32.5 knots deep, 36.5 knots standard). In Goodall’s view, arming such a ship with four 6in guns was impractical. If they were superimposed fore and aft, they would require too high a bridge, but placing a single gun forward would make it difficult to arrange the others. In an alternative design (four 5.5in) one 5.5in gun was placed over the machinery spaces (as in Codrington), but ammunition supply would be difficult and arcs too restricted (problems which would presumably also have applied to Codrington, but that was not mentioned). Goodall’s preferred alternative used destroyer armament. Goodall pointed out that five Codrington type boilers would entail undesirable machinery length, so he offered another version with six smaller boilers, placed two abreast as in cruisers. The most interesting feature of the simple sketch Goodall prepared was that the funnels (of the same height) were all vertical, rather than, as usual, raked. The British were adopting vertical funnels in contemporary cruisers specifically to confuse an observer as to the course of the ship. This project, on the DNC’s own initiative, was undated but was probably undertaken about June 1929. Nothing came of it, and work proceeded on the basis of the destroyer-size hull with four 4.7in guns.
The Board approved the legend and drawings of the 1929 destroyers and leader on 13 November 1929. At that stage, the programme called for eight destroyers and a leader.
Meanwhile, preparatory work for the 1930 London Naval Conference went ahead. The conference was called to consider what should be done after the battleship-building ‘holiday’ decreed at Washington in 1921 expired on 31 December 1931. Beset by the Great Depression, the British government hoped not only to extend the ‘holiday’ (it did) but also to limit other classes of ships. To demonstrate its sincerity, it cut the draft 1929–30 Programme. Thus, a 20 January 1930 Admiralty circular announced a revised programme, including only half a flotilla (four destroyers, one leader). ‘Steps may now be taken to place orders.’
The cut to half a flotilla seems to have killed the proposal to seek private designs. Two ships were assigned to Portsmouth Dockyard, the first destroyers built in a Royal Dockyard. White built the leader Kempenfelt, but to the Admiralty design. The Fighting Services Committee agreed that this was below the acceptable minimum, and the programme was never this thin again. Because the half-flotilla (C class) did not form a cohesive tactical unit, the ships were eventually sold to Canada.13
The British 1927 Geneva negotiating position was revived when the treaty system was reviewed at London in 1930. The resulting treaty shaped destroyers designed over the next six years. Once more, the British goal was to rein in cruiser construction.
HMS Foxhound is shown in 1935 in Home Fleet grey. The antiaircraft gun on the platform between her funnels is a quadruple 0.5in machine gun, which replaced the earlier single 2-pounder. On trials, Foxhound made 35.883 knots on 36,015shp (349.3rpm) at 1550 tons. The E through to H classes had nine-foot UK 1 rangefinders. During the Second World War, some ships were refitted with anti-aircraft fire control systems (FKCs, or fuze-keeping clocks) and UK 4 or UR 2 rangefinders on three-man mountings. Here U indicated a high-angle rangefinder.
The British believed that they needed a total of seventy cruisers, many of them to protect global British trade against the likely threat of surface raiders. They could not possibly afford seventy of the new heavy cruisers built to the 10,000-ton, 8in gun limit agreed at Washington. The British hoped that once the heavy cruiser had been scotched, navies would revert to building reasonably sized ships of about 6000 to 8000 tons. This hope affected their wider strategy. There was always a danger that navies would evade limits on any one category of warship by building oversized versions of the next version down. The French were already building super-destroyers (contre-torpilleurs) and claiming that three of them would be more than a match for an 8000-ton cruiser. Thus, the British attempt to limit cruisers was linked to an attempt to limit destroyers.
To gain US agreement to limit construction of the big cruisers the US Navy favoured, the British had to accept a limit of fifty under-age cruisers of their own. Trade protection was an irreducible requirement, so the fleet would have fewer cruisers. Destroyers would have to make up for some cruiser roles. This recalled the situation in 1914, when Jellicoe emphasised the defensive role of his destroyers because he did not have enough fast light cruisers. Fleet reconnaissance (without aircraft, because in some seas and in some weather conditions aircraft could not operate) particularly demanded numbers that could not be provided. When the Tribals, which were, in effect, intermediate between destroyers (as then understood) and cruisers, were being considered in 1935, it was argued that destroyers were already being used inefficiently as fleet scouts. The need for small cruisers, it was said, was closely tied to the numbers and gun power of the destroyer force, because cruisers were needed to stiffen that force as it tried either to break through or to defeat enemy destroyers.14 Even existing leaders did not fulfil this condition when compared with the heavy Japanese six-gun destroyers.
The treaty, which expired on 31 December 1936, assigned destroyers a nominal lifetime of sixteen (rather than twelve) years; except for a limited number of flotilla leaders (1850 tons), they could not displace more than 1500 tons each. The Royal Navy (including Dominion navies, considered part of the Royal Navy) was allowed up to 150,000 tons of under-age ships. The British signed the treaty even though France and Italy refused to, because Japan, their most likely future naval enemy, did accept it. In hopes of encouraging France and Italy to come to terms, the 1930 treaty included an ‘escalator clause’, under which any signatory could announce that it was retaining over-age tonnage or changing its limit to meet an emergency. This clause would be invoked by Britain in 1936, to preserve over-age cruisers and destroyers.
In the Board’s view, it was most unlikely that an agreement to abolish submarines would be reached. In that event its 200,000-ton figure could be cut to 150,000. The Board was shocked to discover that, having failed to secure abolition, the British government put forward the 150,000-ton figure anyway. The margin of older destroyers earmarked for convoy and other anti-submarine roles was eliminated. The Admiralty’s response was to shift the role of the sloop, which was then being built mainly for wartime minesweeping, to anti-submarine escort.15 In 1932, looking forward to the 1933–4 Programme, the First Sea Lord commented that the French position had, if anything, hardened; the Royal Navy needed more destroyers. However, in view of the economic crisis and an impending (but abortive) arms control conference in Geneva, the Royal Navy had to hold to its policy of one flotilla per year.
Looking ahead in May 1930, the Controller pointed out that given the sixteen-year destroyer lifetime, it would be necessary to build 9375 tons of destroyers each year to maintain an under-age force of 150,000 tons. That in turn would equate to about seven ships, rather than the desired full flotilla, each year. He proposed building a full flotilla in 1930 (1930–1 Programme; D class), followed by a leader and only six destroyers in each of 1931 and 1932, then eight (without a leader) in 1933. This programme made sense only if destroyer design remained stable enough that ships of different classes could easily work together, and even then it would not provide enough modern ships quickly enough.
In the aftermath of the treaty, in January 1933 the Board polled officers on what new steps the Royal Navy should take.16 In effect the replies were a critique of the existing standard design. The Captain (D) commanding 3rd Destroyer Flotilla pointed out that, given the tonnage limit, no prospective destroyer could protect British shipping against super-destroyers such as those the French were building. The only possible counter would be plenty of the heavily armed sloops the treaty allowed the Royal Navy to have in unlimited numbers. At this time, the Royal Navy was already applying much this solution to the lack of ASW escorts; it never did build sloops designed to deal with super-destroyers.
For existing destroyers, the main problem was ahead fire, particularly as A gun was often swept by seas breaking over the bow. In another context, officers complained that the emphasis on torpedoes pushed the guns to the wet ends of ships whose overall length was severely limited. The Captain (D) 3 wanted three guns forward, with a twin in B position. The Captain (D) 4 wanted a service speed of thirty-five knots (his 4th Flotilla made thirty-one). He considered the forward arcs of his guns deficient, as he had to manoeuvre his ship for a closing action. He wanted six 5in guns, an impossibility on limited tonnage. The Rear Admiral of the Mediterranean destroyer force also thought that sloops (or cruisers) were the only antidotes to the big foreign destroyer leaders. He accepted small destroyer tonnage (1350–1400 tons) and 4.7in guns, but he wanted armament rearranged to emphasise ahead fire. He did not particularly favour twin mountings, but did like the 60lb, 5in shell. Given twin mountings, his favoured arrangement was a single mount in A position, a twin in B, and a single (preferably capable of anti-aircraft fire) between bridge and funnel. He was already acutely aware of the air threat, and wanted a large volume of anti-aircraft fire quickly available to counter what he considered the main threats, low-level bombing and strafing by fighters (his reference to fighter attack may have included dive bombing). The rear admiral commanding the screening ships in HMS Coventry recommended four 4.7in guns and multiple pompoms, a speed of thirty-five knots, and an endurance of 5000nm at twelve knots. Vice Admiral commanding the 1st Battle Squadron stressed endurance, noting that on-paper figures for destroyers were deceptive. Current destroyer silhouettes were too high; bridges should be lower. The current eight torpedo tubes were enough, and he wanted the 62½lb, 5in shell then under consideration. Ahead fire should be improved. He also wanted two separate engine rooms for survivability. Fast minelayers (converted destroyers) would be most desirable in wartime.
The DTSD concluded that twin mountings were worthwhile. Their design led to that of the Tribal class, because they offered near-cruiser firepower on a destroyer displacement. The DTSD also favoured the multiple pompom (in place of the 3in anti-aircraft gun) both for short-range anti-aircraft fire and as a low-angle weapon for melees. Unfortunately existing modern destroyers could not accommodate it, and there was never much chance of installing it on board the surviving First World War leaders; it was in too great demand. He rejected the third gun position abaft the bridge because it would impose too much blast on the bridge, and a hit forward would put three guns out of action.
The DNC did not like rearranging the ship so radically, but pointed out that the X gun already had a forward arc as good as that offered by a third gun abaft the bridge. Y was ten degrees worse, and difficult to improve, but he was working on it. He was also considering interchanging the Y gun and the after tor- pedo tubes, perhaps in the G class design (this was not done). The silhouette could be lowered 2ft 6in if the helmsman was given a periscope rather than a direct ahead view, as he would no longer have to clear B mounting. A one-funnel design (ie, reduced silhouette) had been prepared but not approved.
HMS Falknor was the F class leader; HMS Exmouth (E class) was similar. On trials, Faulknor made 36.527 knots at 35,800shp (360.1rpm) at 1651 tons.
The resulting draft letter to the C-in-C Mediterranean summarised what had been learned: the existing eight torpedo tubes were enough. Twin mounting and improved X and Y arcs would be investigated. Ships should have high-angle control systems (introduced in the Tribal class). All main armament guns should have forty degrees elevation (soon introduced). The largest possible mutiple machine gun should be installed. Since the four-barrel 2-pounder was probably too heavy, this left the quadruple 0.50in, but this discussion probably also inspired development of the abortive quadruple 0.661in gun. No 3in anti-aircraft guns would be fitted. Future leaders would all have the extra gun. All destroyers would have Asdic.
With the 1930–1 Programme construction reverted to the earlier pattern of a leader and eight destroyers. Work on the new design began in autumn 1929, before the London Treaty was complete. The first question was whether to adopt a 5in gun in place of the existing 4.7. The staff discussion the Sea Lords requested in April 1929 was held early in May.17 The advance to a 5in gun was presented as a possible provocation to the Japanese. The British counted the big Fubukis, with their twin 5in guns, as leaders (not to be compared directly with destroyers). Thus they thought that to the Japanese the 4.7in guns of their earlier ships were standard weapons. Similarly, the US Navy, which already had five ‘flush deckers’ armed with 5in/51s, was described as only a potential adopter of the heavier calibre. At the end of May, the Controller argued that if the two other main powers adopted 5in guns in new destroyers ‘we should do so too, or our destroyers will be out gunned by those of all foreign fleets’. The numerous French ships with 5.1in and 5.5in guns apparently did not count. The Controller expected a 5in shell to weigh 60lbs, compared to 50lbs for the 4.7in. Remembering the steady increase in battleship gun calibre, the Controller (Admiral Backhouse) told detractors of the new gun that it was foolish to hold back simply because the existing gun was satisfactory. It would be much easier to increase firepower by increasing calibre, because it would be simpler to mount four 5in than to mount five 4.7in. Moreover, ‘because we have now relatively few cruisers, it seems more than probable that in a future war (if there is one) destroyers will have to do some of the cruiser work’. Although the heavier gun should not be adopted at once, it would be well to produce a design, so that a mounting could also be designed. Another officer (not identified) added that a 5in gun and mounting should be designed ‘in case it is necessary to build light cruisers of 2500 to 3000 tons’. The DNO initiated design of a 5in QF gun on 24 June 1929. The DNC claimed in late May that such a gun would require a ship 5 per cent larger, to provide larger magazines and shell rooms, larger working spacer, heavier blast screens, wider deck houses, and more beam for stability. The ship would probably be about nine feet longer. Sceptics pointed out that the C class was being enlarged anyway.
As for the high-angle gun proposed for earlier classes, the DNO pointed out that any dual-purpose gun larger than four inches would require power training which ‘appears to put this requirement out of court for destroyers’.
HMS Griffin is shown, newly completed, in 1936. Note the tripod mainmast, adopted to reduce the need for stays which would interfere with anti-aircraft fire, and the paravanes stowed aft, plus the TSDS winch visible just forward of the after deckhouse. On trials, Griffin made 35.88 knots at 33,916shp (349.9rpm) at 1511 tons.
The 5in soon evolved into a 5.1in gun (a standard French destroyer calibre).18 Kempenfelt was chosen to test it. In March 1930, the two test guns had completed proof tests and were about to be shipped to Shoeburyness for test firing (thirty rounds), one then going to Barrow to be installed on board a standard CP XIV mounting. The gun went into No 2 position.
These studies came to nothing. The design submitted to the Board in September 1930 was a slightly modified C, the most obvious change being replacement of the two 2-pounders (considered not satisfactory) by a single high-angle 3in gun. The 3in gun was added after a discussion between the Controller (Backhouse) and Admiral Dreyer (later DCNS).19 It was added retroactively to the C class, then building. An armament statement showed one hundred anti-aircraft rounds for this gun (plus fifty rounds of star shell). The ship would also have two of the new quadruple 0.5ins on the forecastle deck (Defender, Diamond, Daring and Diana initially had the old 2-pounders due to slow 0.5in production). In addition to the 3in star shell, the ship would have sixteen rounds of 4.7in star shell. Extensive use of star shell seems to have been a new departure, connected with increasing Royal Navy interest in night action. When he approved this change in September 1930, the Controller wanted it applied retroactively to the C class.
Compared with Crusader, machinery was somewhat lighter, and the diesel generator adopted in Kempenfelt was to replace the earlier gasoline generator. The sides and front of the bridge were given bullet-proof plating.
The rhythm of alternating flotillas equipped with TSDS and Asdic continued, this class having Asdic (as decided in July 1930). These ships had twenty depth charges rather than the fifteen of the Beagles. They also had provision to stow another ten charges in the torpedo warhead magazine in wartime, when warheads would be carried permanently on their torpedoes.
As initially described to the Board, one ship had accommodation for a Captain (D), but apparently not for his staff. Later, however, the Controller was told that the 1930 leader (HMS Duncan) would be a repeat Keith or Kempenfelt, with destroyer dimensions but twenty-five tons heavier. When the design was approved, it was agreed that the leader might be lengthened by seven feet to increase accommodation. The DNC found that he could provide the necessary cabins on the original length. He admitted that accommodation, particularly for ratings, would be somewhat crowded.
The D class design was presented to the Admiralty Board in a 30 September 1930 memo. The Board approved the legend on 7 October 1930.
The C and D class designs seem to have been well liked, because at a 9 April 1931 Controller’s conference to define the 1931 ships, they were described as repeat Cs or Ds. With the sixty-degree gun under test aboard HMS Bulldog, the idea of mounting such a weapon in No 2 position was revived (to be decided in December, when trials would be complete). The engine room would be one frame space longer, the boiler rooms one frame space shorter, but machinery weight would not change. Like the Cs and Ds, the new ships would have bullet-proof plating on their bridges. The Controller asked if stores endurance could be extended to twelve weeks. The previous class having been given Asdic, this one would have TSDS instead. Two ships would be fitted to lay mines.
By early June, it was clear that, despite similarity to the Cs and Ds, none of the three designs (destroyer, minelayer or leader) would be quite a repeat. A sketch design was submitted on 18 June 1931. Oil stowage was slightly reduced (to 446 tons), giving estimated endurance of 5500nm at fifteen knots, comparable to that then credited to the Crusader class (470 tons); the Acastas were credited with 4800nm at fifteen knots (390 tons). These figures considerably exceeded those previously used. Stowage for twelve weeks of provisions was provided. The forward magazine was large enough to accommodate an extra one hundred rounds of high-angle ammunition if the sixty-degrees mounting were adopted.
There was clearly interest in a three boiler room arrangement, because DNC A W Johns added in pen that such an arrangement would require six feet more length and would add about twenty-five tons. The Controller (Backhouse) approved the sketch design but with the three boiler room arrangement and, if possible, with 200 rounds per 4.7in gun, or at least for the two forward guns. If the sixty-degree gun was used, it would occupy X rather than B position. Thus in December 1931 the approved armament of the 1931 destroyer was three low-angle 4.7in guns, one sixty-degree 4.7in gun, one 3in anti-aircraft gun, two quadruple 0.50s, four Lewis guns, and six depth charges with one chute, plus TSDS.
In October, the DNC reported an alternative sketch design showing one rather than the usual two funnels. The necessary trunking would add about three tons. Johns suggested that there might be operational advantages, ‘but on this point DNC can express no opinion’. Goodall’s two-boiler destroyer of 1927 had had a single funnel. When the US Navy adopted single funnels a few years later, the argument usually cited was that they reduced the destroyer’s silhouette and thus improved her chances of approaching a target undetected. Also, it was much more difficult to gauge the course of a single-funnel ship for fire control reasons (presumably why Orion class cruisers had single funnels amidships). The cruiser designers had to revert to two funnels so that they could subdivide their machinery, but that did not apply to a destroyer.20 The idea seems to have died when the Director of Operations Division (DOD), Dudley North, denied any real difference in overall silhouette. The Controller (Backhouse) pointed out that the two-funnel ship had a smaller silhouette because she had a shorter forecastle; it was also simpler and lighter. He did want the 3in gun moved further from the after funnel.
In 1932, the Naval Anti-Aircraft Gunnery Committee produced proposals for fleet anti-aircraft modernisation. It recommended omitting the 3in gun, leaving only the 0.50s. The Committee considered it more effective to increase the elevation of all the 4.7in guns to forty degrees, which it was thought would give destroyers the ability to cover heavy ships against the air threats then considered most important, level and torpedo bombers. The Committee wanted all destroyers to have high-angle fire controls to match their supposedly dual-purpose main batteries, and anti-aircraft ammunition. Admiral Frederic C Dreyer (DCNS) argued that the 3in should be retained until the forty-degree mountings, controls, and ammunition materialised.
Increasing gun elevation to forty degrees was hardly a trivial proposition. Trunnions had to be raised so that the breech would not hit the deck when recoiling at maximum elevation. That in turn made it more difficult for loaders, who had to lift ammunition higher. The solution was to provide a shallow well under the gun. British destroyer guns of this era used loading trays, which in effect considerably lengthened them. In June 1933, in connection with later ships, the DNO pointed out that, without a loading tray, no well would have been needed, and indeed it would not be difficult to get fifty-degree elevation. The extra length also made it difficult to mount higher-velocity guns. The Royal Navy therefore used a 4.7in/45, but without the tray it could adopt a 4.7in/50. Loading trays were introduced for destroyer 4in guns, eliminated because they slowed the rate of fire, then re-introduced in the 4.7in anti-aircraft gun (for battleships) to make it possible to load at high elevation. Trays were used because shell and cartridge case were separate. At high elevation angles, mechanical ramming was necessary to ensure that the shell seated properly and did not fall back while the cartridge was being loaded. It in turn required the tray. Given a loading tray which could be swung into place to load, the next round was always ready as one was fired.
The issue was what destroyers were intended to do. On the one hand they were torpedo attack or defence ships. On the other hand, they were intended to screen the fleet on passage against submarines (hence Asdic) and mines (TSDS). By 1932, it seemed that a fleet on passage also needed an anti-aircraft screen, hence the Committee’s recommendation. The Controller (Rear Admiral Charles Forbes) was unhappy; a lively destroyer might well be a poor anti-aircraft platform. Cruisers being strictly limited under the London Treaty, nothing else might be available. The 3in gun, with a makeshift fire control system and poor arcs of fire, was hardly impressive. To make the forty-degree guns effective would require an expensive control system. A forty-degree gun could hardly be called dual-purpose (the Controller characterised it as meeting only 4/9 of the requirement).
The Sea Lords and ACNS thrashed out the question at a 22 June 1932 meeting, concluding that future destroyers needed forty-degree guns, even though no high-angle control system might be available for some years. The ships also needed more ammunition: 200 rounds of high-angle ammunition per ship in addition to low-angle ammunition. Since the 1931 destroyer already had provision for an extra one hundred rounds for the abortive sixty-degrees mounting, this meant adding another one hundred rounds to the ship. The DNC now standardised on 200 rounds of low-angle ammunition per gun, instead of 200 per gun forward and 190 per gun aft. The design added the fifty star shell, which were associated with the 3in gun, and these replaced the fifteen formerly carried for 4.7in guns. The design thus provided for 200 rounds of high-angle ammunition, but while the ships were being built this requirement was cancelled. Thus the ships had larger magazines than required, which in turn meant that their crowns protruded above the waterline – an unfortunate and potentially dangerous feature. This problem became evident only when the next (G) class was being discussed in 1933. To achieve forty-degree elevation, each gun was surrounded by a shallow pit covered by portable plates, which were removed for high-angle firing. Fire control was unchanged, so the ships could use their guns only for barrages against aircraft. All of the later A through I class destroyers were similarly limited. The three-man director (adding height-finding against aircraft) and the associated fuze-keeping clock (FKC) appeared only in the Tribal class.21
Given the failure of the London Conference, the fleet still needed an Asdic screen. In September 1931 the Admiralty decided in principle that all new destroyers would be fitted so that Asdic could be installed (this did not apply to the C class, the construction of which was already well advanced).22 Probably by late 1931 the prospect of war also seemed closer, given the Japanese seizure of Manchuria and vital British economic interests in China, from which Manchuria had been wrested. At the beginning of 1932, the Controller (Backhouse) explained that otherwise simply providing for Asdic installation would take considerable time, even if the Asdics required already existed. The clinching argument was that, given the reduction in overall force due to the treaty, all destroyers should have Asdic. The Royal Navy could no longer afford the luxury of dividing its force into those which could and could not prosecute submarines. Destroyers fitted with TSDS should have thrower positions prepared so that they could be mounted quickly as needed. The Es were the first class affected by the new policy, because the C class was too far along to be modified. In order to make room for the Asdic trunk, their boiler rooms were shortened.23 Finally, in June 1932, it was decided that all future destroyers and leaders should be built with Asdic and fitted so that they could operate either with TSDS or as minelayers, being converted quickly from one role to the other. The 1932, 1933, and 1934 ships would all have Asdic and TSDS.24 The 1931 destroyers were to displace 1405 tons (standard). Installing Asdic and depth charges would bring that to 1415 tons in a TSDS destroyer and to 1425 tons in a minelayer (1415 tons with TSDS and without Asdic and depth charges).
From the outset, two of the 1931 destroyers, Esk and Express, were intended as minelayers, convertible at short notice to TSDS destroyers. As minelayers, they would surrender the torpedo tubes and the A and Y guns (with ammunition), plus their TSDS gear and their twenty-seven-foot whalers and davits. Mining stores would be stowed in the torpedo warhead magazine. This arrangement would entail a load of about fifteen tons more than for a TSDS ship not convertible into a minelayer. As no further ships could be fitted for minelaying until the 1931 minelayers had run trials, no ships fitted for these two roles would be ordered until the 1935 (ie, 1935–6) Programme.
Drawings and a legend were submitted to the Board in February 1932 and approved on 18 February.
This time the leader would be a larger ship, similar to Codrington, but with more fuel to match the endurance of the destroyers. Her speed was to be at least half a knot greater than that of the destroyers she led. The DNC offered the Board two alternative leader designs, one with two rather than one engine rooms. Each had the same three boiler rooms as the destroyer (originally he offered an alternative with two boiler rooms). The Board initially approved the version with three boiler rooms and one engine room, with certain changes proposed by the Controller (11 July 1931; 1495 tons). The Controller then suggested dividing the engine room in two, and a new design was compared both with Codrington and with the design originally approved. Adopting a single engine room added two feet and ten tons. Rearranging the engine rooms saved 4½ feet in machinery spaces. Another two feet of length gave space for a housing dome if Asdic was later fitted, for improved accommodation including cabins for sixteen officers, and for greater endurance (5800nm compared with 5700nm at fifteen knots). Dimensions roughly matched those of Codrington. Adopting two engine rooms added twenty feet to length and 1½ feet to beam; the ship would need 39,000 rather than 38,000shp to make the desired thirty-six knots, and her displacement would rise from 1505 tons to 1615 tons. The cost of having two engine rooms would be from £15,000 to £16,000. The DNC pointed out that a ship with a single engine room could lose both turbines to a single waterline hit by a light shell; the ship would likely be lost if immobilised. Replacing her would cost £350,000, so the two engine rooms could be considered a bargain. With one of the two flooded, the ship could still make 25–26 knots.
The E-in-C argued that it would be more difficult to control a divided power plant, making it less responsive to crucial demands for rapid speed changes. More complex machinery would be less reliable. Any claim of additional survivability in an unarmoured ship was illusory.25 Ultimately, the Controller agreed: the larger ship would be too much less manoeuvrable than the flotilla she led, she would not be as flexible, she would be more expensive to maintain (and flotillas were already too costly), partly because she would need six more engine room ratings. The ACNS agreed with the Controller.
The design initially showed two 3in gun abaft the after funnel (plus four 4.7in low-angle guns), but rearrangement of the boiler rooms required that these be placed between the funnels. On 11 July 1931, the Controller decided to have one dual-purpose 4.7in gun or one 3in anti-aircraft gun. The approved armament was changed to four 4.7in low angle, one 4.7in dual-purpose, and two quadruple 0.5in machine guns. If the dual-purpose mount was not available, the ships would have five 4.7in and one 3in anti-aircraft gun. Two quadruple 0.5in machine guns were placed on sponsons on the signal platform, from where they could fire fore and aft and across the bow. The new design had an enlarged staff office.26
The new leader design, for HMS Exmouth, was finally approved in April 1932.
The 1932 destroyers were repeat versions of the 1931 class, with their forty-degree guns, with TSDS and Asdic. The most important change was that they introduced a new Mk IX torpedo (3510lbs) to replace the earlier Mk IV (3510lbs). However, the DTM envisaged a much larger future torpedo, for which he wanted space and weight provision: 4209lbs and 335 inches rather than 291 inches long. The DNC protested that to accommodate it would require either five feet greater length (and ten tons more standard displacement) or rearrangement including reduction of the after deckhouse (with the officers’ quarters) and probably rearrangement of the after part of the ship (TSDS and depth charges). The DTM admitted that the new torpedo was not yet ready, but he ‘confidently expected’ it in the near future – and destroyer and cruiser torpedoes were very important to the interwar Royal Navy. In effect the issue was deferred.
The I class were essentially repeats of Hero and Hereward with pentad rather than quadruple torpedo tubes (but the middle tube was removed soon after the outbreak of war, reducing them to quadruples). They were completed with high-angle fire control computers (FKCs) and with nine-foot UK 4 or UR 2 rangefinders on MK 1 AV three-man mountings. This is HMS Ivanhoe. In the view from aft, note the range dial (to pass range to other ships) on the mainmast, facing aft, and the davit for reloading the depth charge thrower, just forward of her TSDS winch. The TSDS fish are visible on her quarterdeck. On trials, Ivanhoe made 34.013 knots on 34,306shp (344rpm) at 1718 tons; she had the deepest trial displacement of the class. Thus Icarus made 35.104 knots on 33,880shp (348.4rpm) at 1504 tons.
Somewhat lighter boilers helped reduce machinery weight by twenty tons. Presumably the combination of lighter machinery and heavier guns (and other equipment) caused the beginning of the serious topweight problems that would plague the G, H, and I classes.
The leader Faulknor repeated the previous year’s ship.
With the London Treaty of 1930 still in force, it was vital to save tonnage on each ship. The key to doing that was a dramatic reduction in engine and boiler room length achieved by the E-in-C, reported in July 1933. On that basis, the DNC was able to cut the length of the ship to that of an Acasta (six feet and fifty-five tons saved); he could thus reduce power to the 34,000shp of the earlier ship. Average frame spacing was reduced from two feet to 1ft 9in. Oil fuel was reduced from 470 to 455 tons. Complement was the same (137 with space for 146).
The 1933 destroyers began as repeat 1932 ships with forty-degree 4.7in guns. The 5.1in gun was being tested, but on a thirty-degree mounting. If it proved successful (it did not), it would have to be placed on a new forty-degrees mounting, and that would take too long to incorporate it into the 1933 design. For that matter, the C-in-C Home Fleet and his Commodore (D) both recommended the 4.7in over the 5.1in The Director of Tactical Division (DTD) argued that rate of fire was more important than shell weight, hence that the 4.7in was to be preferred.
As in the F class, magazines provided 200 rounds per 4.7in gun. Space was provided for one hundred rounds of high-angle ammunition (in addition to low-angle) if needed. An attempt to bring magazine crowns back under water failed, and there was not enough weight to provide them with any sort of horizontal protection.
In October 1932, the ACNS and the Controller both suggested replacing the existing quadruple tubes with quintuple tubes (later called pentads). Earlier efforts to develop a quintuple torpedo frame had come to nothing, but the desire for more torpedoes in each destroyer survived. In May 1933, the DTM reported some preliminary results: a loaded quintuple would weigh 19 tons 15cwt, compared to 16 tons 4cwt for the current quadruple unit. The DTM pointed out that it was thought that eight torpedoes was the maximum a destroyer could fire in one attack, but that the quintuple would provide two more for later use. They might be of great value when a striking force was formed after a day action, or if an enemy capital ship was forced to fall out of line. The DTD agreed, asking only what the effect of the small extra weight would be on a destroyer. The DNC guessed that the cost would be no more than ten tons overall.
Torpedo batteries gained more prominence because new methods of firing torpedoes, proposed in October 1931, were just being tested. In May 1932, the 3rd Destroyer Flotilla (Mediterranean Fleet) completed the last in a series of exercises designed to find the best way to fire full salvos to cover a freely manoeuvring ship. Four destroyers fired full eight-torpedo salvos at an enemy line represented by two cruisers and two destroyers. On a very dark night, they made contact just as the leading enemy ship altered course. Firing range varied between one thousand and six hundred yards. This was thought to be the first full divisional night destroyer torpedo attack using all torpedoes. The Rear Admiral (D) considered it vital for destroyers to fire full salvos in such trials to avoid false conclusions. Alternate destroyers staggered their shots to avoid collisions between them. They succeeded even though all were firing at the same ship. Because the night was so dark, and because the target line happened to be altering course when sighted, all the destroyers fired at the same ship. Of thirty-one torpedoes fired, fifteen hit the leading ship and one the next in line. Despite the powder charges used, the torpedo discharges were practically flashless, although they could be heard plainly. The commander of the target cruisers thought he could have steered for the destroyers upon sighting them, running them down before they had a chance to fire. Tactical doctrine called for each destroyer to select a separate target when attacking at short range. That did not happen because the target ships were attacked as they turned. However, a tendency for attacking destroyers to concentrate on the nearest target had been seen during somewhat similar exercises carried out as early as 1923.
HMS Inglefield, leader of the I Class, shows the extended open bridge of British leaders, required to accommodate both ship command and flotilla command. Note also the semaphore on the extended bridge. Earlier ships had nine-foot rangefinders, but Inglefield and Faulknor had twelve-foot units (UK 1 and UK 4, respectively). Since the 4.7in gun between the funnels precluded mounting light antiaircraft guns there, the signal deck was enlarged and the quadruple 0.5in guns (not very visible here) were mounted on it. Note the range dial on the tripod mainmast, intended to pass the range to other ships in the flotilla. On trials, Inglefield made 36.69 knots on 38,081shp (363.5rpm) at 1611 tons.
The DTD was impressed by how difficult it was to carry out an unobserved torpedo attack in the Mediterranean – the cruisers spotted the destroyers on a very dark night. He also noticed that destroyer torpedo officers tended to bias their torpedoes forward (hence to hit only the leading ship). For some time, tables of ‘best director angles’ were available on board ships, but these were usually not used in the heat of action. The maximum number of torpedoes which could be fired together was set by the sensitivity of the torpedo pistol. The more torpedoes were fired, the closer together they would run, and the greater the chance that the explosion of one would set off another’s pistol. Torpedoes, too, did not run quite straight, and running them closer together made it more likely that they would collide (as happened too often in exercises). Was eight the maximum?
In June 1933, the Torpedo Tube Design Committee met under the chairmanship of the DTM. The DTD much wanted the fifth torpedo. The representative of HMS Vernon pointed out that adopting a less sensitive torpedo pistol would make five-torpedo salvos practicable. The DTD reminded the Committee of the collision problem. The Board referred the question to the C-in-C Mediterranean. As that would take time, the DTM suggested in July that the question be deferred to the next (1934) class. Space and weight would be provided to install quintuple tubes if desired. In October, the C-in-C Mediterranean supported the quintuple mount because it would provide spare torpedoes in a night action following a day action, and for the ‘increased general operational value of the destroyer due to the increase in armaments’. The DTD agreed; all the 1933 destroyers and the leader should have quintuple tubes. The ACNS disagreed: if ten-torpedo salvos could not be fired, why spend the extra money? First Sea Lord Chatfield agreed.
The main machinery change was elimination of cruising turbines. In June 1933, the E-in-C pointed to great efforts made since the First World War to bring destroyer endurance closer to that of the capital ships they would accompany. That had entailed complication and greater machinery space and weight, for example, for cruising turbines. However, in wartime destroyers would rarely cruise at speeds below fifteen knots, hence would not benefit from the cruising turbines. Their nominally great endurance reflected unrealistic trial and peacetime conditions. Given continuing pressure to cut destroyer size, it was time to rethink machinery design. A meeting among the DCNS, the ACNS, Director of Plans, and the DTD agreed with the E-in-C, who expected that a redesigned plant (without cruising turbines) would easily achieve 4000nm at fifteen knots.
As in the First World War, the Royal Navy took over destroyers building in Britain when war broke out in 1939. HMS Havant was one of six Brazilian ships being built to essentially the H class design (with the new-style bridge). She and her sisters were completed with heavy depth-charge batteries, Y gun being omitted as compensation. Like other export destroyers, they had a commercial (probably Vickers) fire control system in which the rangefinder was integrated with the director control tower, rather than being separate. The ship’s mainmast carries the earliest form of HF/DF antenna, a simple diamond coil. The ship had to turn to find the direction of the signal. The ship’s quarterdeck shows the eight throwers (indicated by depth charge loading davits) needed for a fourteen-charge pattern, and one of the two depth charge tracks. The US naval attaché to Brazil claimed that the Brazilians would have preferred US ships, but they were too expensive. The Brazilian compromise was to build three US Draytons locally (these became the Marcilio Dias class) while building six H class destroyers in the United Kingdom. When the six ships were taken over, the Brazilians decided to build six more under license. During September 1939, the Brazilians decided that machinery and armament would have to come from the United States, and the Philadelphia Navy Yard became design agent. These ships became the Acre class.
The E-in-C provided a table (reproduced here at Table 9.1) comparing endurances of various postwar destroyers, all with 470 tons of oil, and the V & W classes (340 tons). Figures for the D and V & W classes were actual performance and the E/F and G figures were estimates.
Table 9.1:
Comparison of endurance of various postwar destroyers
| Speed (knots) | D | E/F | G | V & W |
| Full | 1250 | 1285 | 1240 | 600 |
| 30 | 1600 | 1550 | 1580 | 760 |
| 25 | 2500 | 2240 | 2400 | 1220 |
| 20 | 4000 | 4390 | 3800 | 1800 |
| 15 | 5870 | 6350 | 5530 | 2600 |
| 12 | 6350 | 6840 | 6000 | 3120 |
The G class (1933–4 Programme) design was presented to the Board on 26 October 1933. The Board approved the legend and drawings on 1 November.
The G class enjoyed export success: Yarrow built two for Greece (Vasilefs Giorgios class; laid down 1937) and several British builders built seven for Argentina (Buenos Aires class; laid down 1937). The Greek ships were armed with German 5in guns. Building in Britain during the Munich crisis of 1938, they were listed among ships to be taken over if war broke out. They were delivered before that happened in 1939.
The G class leader, HMS Grenville, was similarly cut down (by forty tons) from the previous year’s Faulknor. She had two (rather than six) side tanks in her boiler rooms to carry emergency oil fuel (normally one carried extra reserve feed water and the other fresh water). Armament was five forty-degrees guns (4.7in), two single pompoms, four Lewis guns, and two quadruple torpedo tubes (quintuples could be substituted at a cost of ten tons), plus the now-standard two depth charge throwers and one rail (twenty charges). Another ten charges could be carried in wartime, and there was provision for the two-speed sweep.
In its tender, Yarrow offered side- rather than the usual end-fired boilers. In that case the space usually provided for vents at the fore end of the forward boiler room would become available for other purposes, such as a staff office. The ship was shortened by seven feet, and some spaces, such as the galley, moved (in its case, under the forecastle deck, where it encroached on the upper deck messes).
On 13 July 1934, the Board approved simply repeating the G class as the H class (this had been proposed as early as November 1933).27 Welding was employed extensively. The only real question was whether the ships would be designed for easy conversion to TSDS or to minelaying, as had been suggested in 1931. Minelaying required sponsons, conveyor belt machinery in the steering gear compartment aft, a larger torpedo davit (to embark mines as well), a narrower after superstructure, space on the bridge for mining instruments (to place the mines precisely), and alternate positions for depth-charge throwers. When the decision to adapt these ships to this purpose had to be taken (December 1933), the two E class minelayers were still under construction, due for completion during autumn 1934. Trials would occur about November 1934. Minelaying features were deferred to the 1935 flotilla, and none of the 1934 ships laid mines in her career. Compared to the G class, the H lost stability due the topweight of the new CP XVIII mounting, in which the counterweight was rearranged so that the gun well with its portable plates could be eliminated. The cost was 1.7 tons per gun.
Faulknor
HMS Faulknor was the F class leader; the leaders of later classes were virtually identical. She is shown, newly completed, in July 1935. She was not fitted for TSDS, and she had both Asdic and a five-charge pattern depth- charge battery: a three-charge track on the stern with nine reloads and two throwers with three reloads each (plus one on the thrower). The main guns were 4.7in Mk IX on the forty-degree Mk XVII mounting, which was expected to provide a measure of anti-aircraft capability (to deal with bombers approaching the fleet). Opinions varied as to how valuable such guns could be, and they were useless against the dive bombers which did the most damage to British warships during the Second World War. Supporting the anti-aircraft function was a new three-man rangefinder which provided target elevation as well as range. However, the planned antiaircraft fire control calculator (fuze-keeping clock) was never installed prewar; like other interwar destroyers prior to the Tribals, she had the surface-only AFCC Mk I computer. It was complemented by the usual turret-like destroyer DCT (director control tower) with gyro sights. The most obvious difference from the destroyers Faulknor led was the additional 4.7in gun between her funnels, but she also had enlarged signal deck wings supporting her two quadruple 0.5in machine guns (clear in the plan view). In the destroyers these weapons would have gone on the platform which in Faulknor supported the midships 4.7in gun. As in F class destroyers, all the 4.7in guns could elevate to forty degrees, for limited anti-aircraft use.
(DRAWING BY A D BAKER III)
HMS Griffin is shown, newly completed, in 1936. Note the tripod mainmast, adopted to reduce the need for stays which would interfere with anti-aircraft fire, and the paravanes stowed aft, plus the TSDS winch visible just forward of the after deckhouse. On trials, Griffin made 35.88 knots at 33,916shp (349.9rpm) at 1511 tons.
One of the 1934 ships, Glowworm, was fitted with prototype quintuple tubes for tests. She would be completed in March 1936. The CNS was not willing to reverse his opposition from the previous year, so the question of fitting more ships with these tubes was deferred to 1935.
Meanwhile, a twin 4.7in power-driven mount was being developed for the big Tribal class destroyers already in the concept stage, HMS Hereward was chosen as trials ship, the mount being in B position. There it would block the view of the helmsman over so wide an arc that the bridge structure had to be redesigned. The form already developed for the Tribals was chosen: the helmsman was raised half a deck. Since the usual square structure could not accommodate him, he was moved forward into a structure built into the face of the usual one, with angled sides and an angled top. This new kind of vee-front bridge became characteristic of British destroyers, beginning with the Tribals. Hero, the other destroyer being built by Parsons (with hulls by Vickers Armstrongs), had the same bridge, although she did not test the new gun mount.
Hero was completed first. Trials showed that the new bridge was a great improvement. The structure forward of the open bridge, plus the six-inch vertical extension of the fore bulkhead of the bridge, deflected the air up, giving wind protection: at full speed a person on the compass platform (the open bridge) felt no wind. With the glass screens removed, it was possible to stand on the deck and look ahead in comfort. At the same time, at the fore end of the signal deck, which had the usual wind deflectors, it was difficult to look over the top of the screen due to the wind. There was a strong forward current of air along the sides of the bridge and outside the bridge structure, presumably because air was sucked into the vertical movement. The wind was calm on the day of these trials, so it was impossible to test the new structure in a cross wind, but the DNC’s representative suggested that the reverse current might neutralise side winds. The new type of bridge was therefore adopted for the next class of destroyer (I class). Overall, the bridge layout in Hero was praised as simpler and more efficient than in previous ships.
Like the G class, the H class enjoyed export success: six were built for Brazil (Juruena class) and four for Turkey (Gayret class). All of the Brazilian and two of the Turkish ships were taken over by the Royal Navy in 1939. Brazil ordered components for six more H class destroyers to be built locally; they were completed, armed with US weapons, in 1949–51, and had much the appearance of the US single-stack destroyers.
The H class leader, HMS Hardy, was a repeat Grenville with three inches more beam.
By 1934, the international situation was much bleaker. The Royal Navy focused on an increasingly aggressive Japan, which in April 1934 announced that it was withdrawing from the naval arms limitation treaties. Even before the rise of Hitler, an Admiralty survey of the world situation saw Europe moving towards a prewar situation. In 1932, the Ten-Year Rule, which had been used to limit defence spending, was abandoned. A Defence Requirements Committee was formed, and this concentrated on the expendables, including Asdic transducers, which had not been bought due to the Rule.28
In the run-up to the 1935 London conference, which was to review the 1930 treaty, the Royal Navy aim was twelve underage and four over-age flotillas, one of which would be formed of Dominion (Australian and Canadian) ships. At the end of 1934, the Royal Navy would have 7¾ under-age flotillas, the three-quarters being the two prototypes plus the four Cs. War-built ships were proving increasingly difficult to maintain. Given the shortage of cruisers (due to the 1930 Treaty) and the construction of large destroyers (Fubuki and later types) by Japan, the Royal Navy was interested in much larger destroyers or scouts, which soon emerged as the Tribal class.29 They were the first break from the standard series of torpedo-heavy destroyers, and as such began a new kind of destroyer story, not told in this book.
The Turkish destroyer Sultanhisar was an I class destroyer built for Turkey. Unlike the Brazilian H class, she had British equipment, including a standard destroyer fire control installation (apparently including Asdic). According to the October 1942 British register of foreign war vessels, at the time these ships had six 1.57in (40mm) anti-aircraft guns, presumably British single 2-pounders. During the run-up to the Second World War, the British government sought to strengthen Turkey as a bulwark against Russian and German expansion towards the Mediterranean. In connection with a potential Turkish order, on 4 January 1938 the Foreign Office wrote the Admiralty that ‘Turkey is one of the few countries upon whose co-operation His Majesty’s Government may be able to count with reasonable certainty in the event of a general deterioration in the international situation’ – which was exactly what was happening. In December 1937, the Turkish naval attaché proposed orders for ten submarines, four modern destroyers, four convoy sloops (corvettes), twelve Blenheim bombers, and nine large guns for the Dardanelles. The Foreign Office proposed special credits, not least to forestall an attempt by the Germans to secure some or all of these orders (ultimately the Germans and the British split the order for eight submarines). Ultimately, the Turks wanted to build a fleet to secure their coastal waters: two groups, each comprising a heavy cruiser, four destroyers, and twelve submarines. Counting ships refitting, they wanted a total of twelve destroyers and thirty submarines. The four existing modern Italian-built destroyers had given considerable trouble, but were now serviceable, so they wanted to buy another eight modern ships, all to be built in the United Kingdom. A special bill was put through Parliament to provide the necessary credit to Turkey. Orders were placed for four destroyers and four submarines, plus smaller ships. Given the strategic significance of Turkey, two of the four destroyers and two of the four submarines were delivered to that country despite the dire need for destroyers in British service: Sultanhisar (shown) and Demirhisar. Presumably the Turks remembered the seizure of battleships and destroyers in 1914, which had helped justify the First World War alliance with Germany. The other two, Muavenet and Gayret, were taken over by the Royal Navy, although the official Royal Navy ship data publication referred to these as Turkish ships on loan (no such designation was applied to the Brazilian ships). As HMS Ithuriel, Gayret became a constructive total loss, and was replaced postwar by the newer destroyer Oribi. HMS Inconstant was refitted at Devon port for return to Turkey (18 September 1945–27 January 1946), and was returned (as Muavenet) on 9 March 1946 at Istanbul.
Plans for the 1935–6 Programme were initially limited to the Tribals. However, as an emergency measure due to the outbreak of the Italo-Ethiopian War (which led to a confrontation with Italy), a flotilla of ordinary destroyers was added, with the understanding that it might end up in the 1936–7 Programme. As the situation worsened, the I class was brought forward to the 1935–6 Programme. These ships ended the series of destroyers begun with Amazon and Ambuscade. There was considerable interest in reviving the earlier standard type after the Tribals had been built, but the need for gun power generally won out. The wartime emergency destroyers did fall back on much the armament as the A through I series, but that was more a matter of expediency, to produce desired numbers, than of tactical thinking favouring torpedoes over guns. The Tribals and the later larger destroyers are all described in another book.
At about the same time the British government exercised the escalator clause of the 1930 treaty to retain ships about to be discarded as over age, including thirty-six V & Ws. Plans called for them to be rebuilt for escort duty, as described in Chapter 10.
The treaty structure was not abandoned altogether. The 1936 London Naval Treaty retained limitations on individual ships, such as 5.1in guns for destroyers, but it abandoned any attempt to limit total fleet tonnage. Instead, governments agreed to publish details of new ships far enough in advance that other governments might (hopefully) realise that they were not such threats as to touch off building races. For the Royal Navy, the main effect of prior publication was to freeze building programmes as announced and to make post-ordering changes difficult or impossible. Even without the fleet limits, Japan refused to sign. As in 1930, escalator clauses were included to give her an incentive to join the treaty regime. Signatories reserved the right to raise the individual-ship limits if the Japanese refused to state that they were abiding by the existing limits. On this basis, for example, the 14in gun limit for battleships was raised to 16in. On the other hand, the cruiser limit (8000 tons) stood until the entire treaty system collapsed at the outbreak of the Second World War.
The smaller destroyers of the 1935 Programme began simply as the Repeat H class, modifications being laid out at an 18 October 1935 Controller’s meeting. The main change was quintuple torpedo tubes.30 Each ship would have a high-angle control system and would carry 200 rounds of high-angle ammunition for her forty-degree guns. In fact the ships had the same AFCC Mk I as their predecessors, and no high-angle system. A proposal to stow the new heavy (62lb) 4.7in shells was disapproved. The Controller wanted the DNC to look into the possibility of a single funnel design, to move the main mast forward, and to look into the possibility of placing machine guns aft on the centreline, where the Tribals had their pompoms. The ships would be arranged at the stern for minelaying.
The combination of the new heavier gun mounting and the quintuple tubes cost stability as compared to the E, F, and G classes. The Acastas had been designed on the theory that a ship’s centre of gravity typically rose 0.04 foot each year, a destroyer had a fifteen-year life, and the light condition was the worst for stability. The ship should float when bilged (engine room and adjacent boiler room open to the sea) in light condition, that is, at the end of her life she should have zero metacentric height in that condition. For the Acastas that gave a requirement for 0.6 foot (allowing fifteen years of declining stability) when bilged. Stability had been declining on a class to class basis ever since. Thus, in light condition the Acastas were credited with a metacentric height (GM) of 2.63 feet, and the C class was even better at 2.97 feet, but Glowworm was credited with only 2.24 feet, and the I class with 2.21 feet. The stability range had declined from sixty-seven degrees in light condition in Acasta to only fifty-seven degrees in the I class (both when in light condition). Light condition included ammunition. The situation was so bad that the G and H class destroyers could not accept any added topweight without compensating reductions. Proposals had been made to improve I class stability, the best being to revert to quadruple tubes. If that was not done (as was the case), the next best thing was to reduce the bullet-proof plating on the bridge (saving 1½ tons high in the ship) and to make the flats of the magazines and shell rooms and torpedo head room watertight, arranging to flood the compartments below (which would be difficult but practicable). The alternative was about fifty tons of permanent ballast, with consequent loss of speed. The leader, Duncan, was even worse; the DNC estimated that she would have a negative metacentric height if bilged in the light condition.
These ships were designed for easy conversion for TSDS or minelaying, and Impulsive and Intrepid both served as minelayers for portions of their careers. The flotilla leader HMS Inglefield was a repeat Hardy.
Hurricane ex Japarua
As in the First World War, at the outbreak of the Second World War, the Royal Navy took over ships building for foreign navies, which meant mainly the six modified H class destroyers intended for Brazil. HMS Hurricane (ex Japarua) is shown as completed (May 1940), just before the emergency programme that replaced one set of torpedo tubes with an anti-aircraft gun. The main change was elimination of No 4 gun to compensate for the weight of a much heavier depth-charge battery: three depth-charge tracks and eight throwers (fourteen-charge pattern, total of 110 depth charges, many of them on deck). As part of her ASW-oriented configuration, she had an early HF/DF array (the diamond-shaped coil on her tripod mainmast). Unlike destroyers laid down for the Royal Navy, she had a Vickers fire control system, which included a combined rangefinder-director. Power was provided by three Admiralty three-drum boilers (300psi, 620° F). As a measure of the effect of wartime changes and of more realistic trial standards, Hurricane ran her trials at 1930 tons (speed was not recorded). Hurricane had the new bridge tested in HMS Hero and adopted for the I class. She was torpedoed and sunk by the German submarine U 415 on 24 December 1943.
(DRAWING BY A D BAKER III)
The US redesign of the Brazilian H class (as the Acre class) gives some idea both of the potential of the H class hull and of the effect of different US and British standard practices in machinery and in weapons. When the Royal Navy took over the six ships building in Britain at the outbreak of war, the Brazilians decided to build six more at home, to the same design, importing machinery and weapons from the United Kingdom. When that became impossible, they turned to the United States, which by 1940 was interested in encouraging other Western Hemisphere countries to improve their defences. Philadelphia Navy Yard became design authority for redesign using US machinery and weapons. The formal Brazilian request to the US Naval Mission in Brazil was dated 3 March 1940. Philadelphia Navy Yard began work that month, receiving Brazilian plans late in March 1940. By that time, Brazil had somewhat redesigned the British-designed hull, and it appears to have expected the US yard to concentrate on designing a new machinery arrangement. Throughout, the Brazilian navy and its yard (llha des Cobras) were responsible for strength, stability, and seaworthiness of the redesigned ships. Philadelphia asked whether it should proceed on a new-design basis (adjusting hull and machinery as necessary) or on a modernisation basis (new machinery fitted to an existing hull); clearly it preferred the former. New main machinery was ordered from Westinghouse (two ships) and from General Electric (four ships); boilers were supplied by Babcock & Wilcox (contracts were later reallocated, each builder producing turbines for three ships, and General Electric double-reduction gears for all six). As redesigned by the Navy Yard in 1940, the power plant was expected to weigh 559.3 tons (34,600shp), compared to 688.89 tons (42,800shp) for USS Cassin, a ship of the first US destroyer class (Manan) to use high-pressure high-temperature steam (General Electric quoted for double-reduction turbines operating at 370psi and 665° F, that is, at relatively low pressure). Weight per shp was close to that of the US plant. The Brazilian Navy was then building three Marcilio Dias class destroyers based on the USS Cassin, with much the same steam plants. By way of comparison, the British H class power plant originally planned for these ships would have weighed about 490 tons (but that may omit the weight of some equipment included in US weights). The ships were given US-type AC electric outfits (the Dias class had DC installations, but their armament required AC power, particularly for on-mount motors). The boiler arrangement was redesigned, the fire rooms being made of equal length (two bulkheads were relocated; there were still three boilers) and the uptakes trunked together into a single funnel. By September 1940, Brazil had ordered fifteen 5in/38 guns (for the three Diaz class destroyers, which ended up with four each) from the National Forge & Ordnance Company, and was planning to buy another thirty for the A class destroyers – five per ship (orders were later reallocated). These were open or shielded guns, not the fully-enclosed single mounts of later US destroyers. Plans also called for three quadruple torpedo tubes, arranged as in USS Cassin (one on the centreline, two in the waist). In December 1941, Brazil was having a new director, similar in outline to the US Mk 37 (but presumably without a below-decks computer) designed for these ships; the Bureau of Ordnance (BuOrd) wondered whether the pilot house structure of the ships could take the added weight (the three US-designed ships had the lighter Mk 33). Philadelphia soon confirmed that BuOrd was right: Brazil should stay with the lighter Mk 33 originally proposed. By June 1942, Philadelphia was reviewing the ships’ armament to provide them with the sort of light anti-aircraft battery contemporary US destroyers were receiving. The first step was to trade a 5in gun for four Oerlikons. As envisaged in mid-June 1943, the ships would have two twin Bofors (40mm) and four Oerlikons, with two 40mm directors (Mk 51; plus the Mk 33 for the 5in battery). Like British A through to I class destroyers, they had two quadruple sets of torpedo tubes, but in their case they were on either beam (the centreline set was suppressed to provide space for the 40mm guns). That dramatically reduced their torpedo broadside, but by this time most British destroyers of comparable design had only one set of torpedo tubes – and none had 40mm anti-aircraft guns. The depth charge battery was somewhat light by British standards, comprising four throwers and two depth-charge tracks. However, by this time the ships were also to have a pair of Mk 20 (Mousetrap) projectors in the bows (theoretically equivalent to a Hedgehog), as in some US Atlantic Fleet destroyers. The Brazilians approved the design, but asked for six Oerlikons. The final design (1946) showed one twin 40mm gun plus six Oerlikons, two quadruple torpedo tubes, six depth-charge throwers, and two depth-charge tracks (total of forty-four depth charges) with no Mousetraps. The US Navy supplied sonar (QC series) and radars (surface (SF) but apparently not air search). Ships were completed with the 1946 armament, but only No 1 gun was shielded, which suggests that they had topweight problems. About 1956, the ships were modernised with tripod masts supporting the antennas of US SPS-6B air search radars (they may not have had any air search radar prior to this). Number 2 gun was replaced by a second twin Bofors. The ships had two Oerlikons and four depth charge throwers. Construction was slow. The first two ships, Amazonas and Araguari, were launched in November 1943. Completion was badly delayed throughout the war because they used US components needed by the US Navy. Matters were so bad in April 1943 that the Brazilian Minister of Marine considered completing the three Marcilio Dias class as convoy escorts armed with 4.7in guns already available in Brazil (this was not done, and the ships had their armament fitted in the United States). The chief of the US Navy mission to Brazil suggested that the only way to complete the A class in time to fight was to equip them with destroyer escort power plants. The proposal was passed to Philadelphia Navy Yard, which concluded that this rather desperate measure would have saved no time at all, given the radical redesign involved. At the end of the war, work at llha des Cobras slowed dramatically. For example, a third of the workers received twenty-five days of leave because they had had none during the war. In March 1946, the lead ship (Amazonas) was expected to be complete that June, but in September completion date was listed as indefinite (she was 87.88 percent complete, having advanced only 0.67 percent that month). She was actually completed on 11 June 1949. By October 1944, it was clear that the A class was too small, so the Brazilian Navy asked for release of Fletcher class plans on the same basis that it had obtained Cassin plans to build the Marcilio Dias class. In a way, this was much the same conclusion the Royal Navy had reached in the late 1930s, when it had to choose between repeating the A through to I class or building much larger hulls. The US Navy decided to release the plans except for the CIC in its entirety, and the Mk 37 fire control system (the ships would have Mk 33s instead). Philadelphia would again act as contact with the US Navy, a close relationship between it and the Brazilians having been formed during the construction of the Marcilio Dias (M class) and A class destroyers. The Brazilians designated their three planned Fletchers their D class. As of July 1945, the Brazilians hoped to lay down all three ships about 1 January 1946, and to complete them at three-month intervals between 1 January 1949 and 1 January 1950. The Fletcher project was abandoned in March 1946. Overall, the Brazilian A class project gives some idea of how US and British systems compared. It suggests that an A through to I class destroyer could have had a much more formidable anti-aircraft battery, which might have saved the numerous destroyers lost to German dive-bombers in places like the Mediterranean. It is sobering to realise that the British 4.7in gun did not have a much better muzzle velocity than the US 5in/38, so that the Brazilian ships did not sacrifice much in the way of ship-against-ship firepower in order to gain enormously in air defence potential. Araguari is shown, as modified with SPS-6B radar in the 1950s.
(MARINHA DO BRASIL)
