Читать книгу The British Battleship - Norman Friedman - Страница 10

CHAPTER 1

TECHNOLOGY

Command: The Bridge

In 1906, when HMS Dreadnought was completed, the standard British bridge structure was an enclosed charthouse (with bridge wings) topped by an open compass platform, which took its name from the presence of a standard compass with pelorus, later supplemented by a gyro-compass. The ship was normally navigated from the compass platform, from whose compasses sights could be taken. Steering orders were passed to a helmsman below in the charthouse. In the period up to the First World War, compass platforms increasingly were built out forward of the charthouse. The bridge wings below the charthouse were generally designated the signal bridge. Flagships had an admiral’s bridge below them. When director control for secondary batteries was adopted, the directors (at least in newer ships) were generally placed in the wings of the signal bridge. The compass platform was sometimes called the navigation platform, particularly if this bridge level was split into a navigating position and a ship weapon-control position.

The 1909–10 ships (Lion and Orion classes) were completed with single tripod masts whose vertical legs were abaft the forefunnel, as in Dreadnought. Their simple bridge structures included compass platforms projecting forward over their conning towers. This arrangement proved particularly useless in HMS Lion and she and her sister Princess Royal were rebuilt with new bridge structures completely abaft the conning tower and forward of the forefunnel. For the first time the compass platform was placed directly above a substantial structure housing the charthouse, captain’s sea cabin, navigating officer’s sea cabin and other spaces. They were built of non-magnetic brass so as not to disturb the magnetic compass above them. This arrangement was repeated in ships built up to the Queen Elizabeth class.

The Royal Sovereigns were an attempt once more to prune back the bridge structure. Their small compass platform, supported by the foremast, was above a signal bridge carrying searchlights. Below it was an Admiral’s bridge and below it a larger bridge extending around the conning tower. The 6in directors were on an aft extension of the compass platform. Searchlights were on the signal bridge, below the directors. The new type of bridge structure was tested on board HMS Canada, whose bridge structure had originally been built for HMS Royal Sovereign. Early in 1916 Controller asked her CO Captain Nicholson for comments.¹

Nicholson much preferred the lower bridge to the compass platform. Because it was close to the conning tower, officers on it became accustomed to manoeuvring the ship from the level they would occupy in battle, the conning tower. It, but not the narrow compass platform, offered a view aft on both sides. An officer on the lower bridge was ‘more in the ship’, with a better feel for the ship’s motion. Particularly at night, the view was better. The CO in his sea cabin (in the structure below the bridges) was closer to this bridge. However, the lower bridge was practically untenable in even fairly bad weather. Nicholson wrote ‘please God if we meet an enemy at night, I shall be on the lower bridge and I leave you to imagine what I must suffer during winter in the North Sea to obtain that object’. DNC’s battleship designer S V Goodall pointed out that much effort had been made to keep structure away from conning towers specifically to avoid the shell splinters hits on it would create. During the Russo-Japanese War some of Admiral Togo’s staff were killed by a shell which burst on striking a bridge stanchion.

Laid up in Australian waters in about 1923, HMAS Australia shows her bridge and foremast as modified during the First World War. Wartime additions included the long-base rangefinder atop the spotting top at the masthead and the main-battery director on the small platform immediately below it (with the flat face). The bridge structure consists mainly of the compass platform atop the large (extended and enclosed) charthouse. A small platform above the compass platform carries a semaphore and an even smaller platform above that carries a signal light. The bridge wings extend from the sides of the platform just below the compass platform, rather than, as was usual, from the charthouse. The ridge of a 9ft rangefinder is visible on the roof of ‘A’ turret. Note that the turret appears to have additional roof armour, which would have been added after Jutland.

For Nicholson the great question was how well the bridge would function at night, when a ship might have to evade torpedo attack. Searchlights, night lookouts and the command on the bridge all had to be co-ordinated. Searchlights at or near the bridge would blind those on it. Lights above the bridge were far better. However, the higher the searchlight, the smaller the spot it made on the water, hence the more difficult to pick up and hold an object on the water so that guns could engage it. Therefore the manoeuvring or compass platform should be no higher than necessary for bad weather. Nicholson doubted that the forward searchlights would make for good gunnery by the secondary battery, which would try to beat off night torpedo attacks. Directors above the searchlights would be useless, so guns would have to be individually laid, gunners trying to stay on the upper edge of the beam to avoid being blinded. The night defence control positions were relatively low and without a view across the bow. A control officer well below the searchlight would find its beam useless. The 6in directors should move down a deck and the searchlights up. The platform with the 6in directors should become the upper bridge. The two upper bridge searchlights in Canada had ‘very much brought home to me’ these points.

The war-built capital ships (Renown and Courageous classes and Furious) had minimal bridge structures similar to those on Canada and the Royal Sovereigns. CO of Repulse found that except in a fleet or squadron action, it was risky to handle so large and fast a ship from anywhere other than the compass platform. Her squadron and fleet commanders strongly agreed. Given the submarine threat, high-speed steaming was now the rule rather than the exception. DNE made the Compass Platform the recognised navigating position in these ships except when in action. The part of the compass platform occupied by captain and navigator was raised slightly above the rest of the platform. The after part carried gunnery and other control instruments, near enough for immediate control.

The ships of the 1909–10 programme had foremasts but no mainmasts. As a consequence, their only masts were stepped with the vertical leg abaft the funnel and the bridge protruding ahead of the funnel. HMS Orion shows her extremely cramped compass platform and the small charthouse below it. The protrusion from the enlarged conning tower was a fire-control tower.

The principal change in Hood was to restore the cabin structure under the compass platform in conformity with a review of bridge policy in 1917. At the rear of the compass platform were a weather-proof position for the charthouse, signal house and officers’ and captain’s sea cabins. The space below the charthouse would be divided into a signal house and a captain’s cabin. The multiple bridge levels were plated in to form a tower structure with the compass platform on top. Hood may have been the first ship in which the secondary directors were placed at compass-platform level, which entailed considerably increased strain on the legs of the tripod foremast.

With the increasing importance of long-range torpedo fire after Jutland, many ships were given small enclosed torpedo lookout positions either bracketed to the foremast or atop the foretop. Another wartime requirement was a plotting space near the charthouse and the compass platform. Ships maintained plots so that they could report to a master plot on board the fleet flagship, the master plot providing the fleet commander with a tactical picture he could use to make tactical decisions. Plotting meant indicating where various ships were in terms of both range and bearing, hence a dedicated rangefinder.

Modernisation of the Queen Elizabeth class in the 1920s replaced the 15in director atop the foretop with a high-angle control system, the director being relocated to a new platform below the top (some ships had an interim high-angle system in the position atop the foremast). The forepart of the foretop was for main-battery control (spotting); the high-angle position was flanked by 6in control positions. A new level built atop the bridge structure carried a principal torpedo-control position topped, at its fore end, by a 9ft or 12ft torpedo-control rangefinder. A new structure at the after end of the compass platform below this level carried plotting spaces abaft the charthouse. The level below (searchlight and charthouse platform) carried the admiral’s charthouse and the W/T office abaft it, in some cases with a 9ft rangefinder for secondary-battery control and to serve the plot. The level below (lower searchlight platform) carried the captain’s sea cabin and below that, on the shelter deck level (conning tower platform), were the chief of staff’s sea cabin and the admiral’s sea cabin.

The minimal bridges of the Royal Sovereigns seem to have attracted little attention until the Royal Navy began to embrace night action (as opposed to defence against night torpedo attacks) in the 1930s. Night action required remote searchlight control, so that searchlights could be trained on targets whose position was indicated by the ship’s tactical plot (alternatively, they could be illuminated by starshell controlled on the basis of the plot or by other ships’ searchlights controlled on the basis of a flagship’s plot). Ideally plot and remote control should be adjacent and both should be adjacent to the compass platform so that the CO could use the tactical plot.

As the Mediterranean Fleet began to practice night combat from about 1932 on, ships’ COs found their bridges less than perfect.² After various experiments, an arrangement adopted in the cruiser Suffolk was pronounced ideal.³ At night targets had to be found and tracked despite limited illumination. The Principal (Fire) Control Officer (PCO) moved from the director to the compass platform. During a day action his main function was to get the ship’s guns onto an indicated target. At night everything changed: the great problem was merely finding and tracking the target. When both were on the compass platform at night, CO could easily communicate the bearing of a target to PCO, who could pass it to the Evershed Bearing Indicators (EBIs). This simplicity was disrupted by the sheer number of individuals who together might occupy the small compass platform.

The compass platform was particularly inadequate and it was soon extended forward, as in HMS Conqueror, shown here.

The new arrangement was barely adequate for low-powered battleships, but it was impossible in a high-powered battlecruiser. HMS Lion was completed with the new type of bridge, as shown here, but the fire-control platform aloft was so badly smoked on trial that she had to be rebuilt and her sister-ship HMS Princess Royal altered before completion. Note the bulge at the after end of ‘B’ turret, covering the standard 9ft rangefinder. Another rangefinder was installed in the foretop.

Lion’s bridge structure was completely rebuilt. Her heavy tripod was replaced by the pole foremast and her conning tower enlarged, with a revolving armoured hood on top carrying a standard 9ft rangefinder in a stabilised Argo mounting. The new foretop was hardly rigid nor capacious enough to take a rangefinder. Two bridge levels were provided, a charthouse and searchlight platform and, below it, a lower searchlight platform. Note the double 24in searchlights on both. The new bridge structure provided facilities such as sea cabins. Note the additional rangefinder (9ft, later 12ft) atop the much-enlarged compass platform. Note the rangefinder hood atop ‘B’ turret, carrying a 9ft rangefinder. Note, too, that the shelter deck 4in gun, originally an open mount, has been protected by a casemate. In wartime longer-base rangefinders were needed because ranges were greater than had been envisaged. A separate 15ft instrument was mounted atop the conning tower, forward of the armoured hood, in an unstabilised mounting, and a second one was mounted atop the torpedo-control tower, not visible here.

In 1934 CO of Royal Sovereign reported that her bridge was unsatisfactory both for night cruising and night fighting.⁴ At night he wanted a good all-round view, easy and sure means of communication between CO and PCO, comfort (space to move freely and protection from wind and rain), quiet and no glare from within.

Due to these reports Ramillies had her bridge modified. Instead of matching that of Royal Sovereign as intended, it was enlarged by moving the plotting office down a deck to space formerly occupied by the remote control office, which in turn was moved another deck down. The wings of the upper bridge were extended. Ramillies’ CO found the result much superior to that of Royal Sovereign. However, the Vice Admiral of the Battle Squadron considered that the bridge still lacked the essential features of a navigational and fighting position: a good all-round and overhead view (it had a bulletproof roof over its central part and canvas wings to the roof). The view aft was too limited, the severe draft caused fatigue and the limited open space was too crowded.

Princess Royal is shown in wartime, with anti-range finding baffles set up to frustrate any attempt to ‘cut’ her foremast using a coincidence rangefinder (which was futile, since the Germans used stereo instruments). Once she was fitted for director control, it became essential to stiffen her foremast, in this case with a substantial reinforcing leg. In contrast to many other ships, she had her main-battery director on a platform well below her spotting top. Her compass platform was protected with splinter mattresses. Atop it was a 12ft rangefinder. Like Lion, she had a steel casting protecting the 9ft rangefinder atop her conning tower. She also had a 9ft rangefinder in her foretop. Aft she had a 15ft rangefinder on her torpedo-control tower and a 2m (6.56ft) high-angle rangefinder, neither of which is visible here. This photograph seems to have been taken before the range dial was installed on the fore face of the foretop and also before deflection scales were painted on the forward turrets. Note the ‘PR’ recognition letters painted on ‘A’ turret and the 4in high-angle gun visible between the first and second funnels.

During her last large repair, Royal Oak received an entirely new ‘citadel style’ bridge. The new compass platform was much larger and squarer, with two somewhat lower squared-off lower wings, all with prominent wind baffles to keep them reasonably dry without roofs. Below this level was an upper bridge with two more large and more or less rectangular wings. Installation of this ‘citadel’ bridge in other ships of the class was precluded by the outbreak of the Second World War. In a wind off Portland in 1936, Royal Oak showed just how much of an improvement the new bridge was.⁵ In a Force 4 wind, the nearby HMS Ramillies had her funnel smoke ‘as usual’ drawn into her control top before blowing aft, but that of Royal Oak blew aft without rising into the control top. The only important criticism was that a roofless bridge offered no weather, blast or strafing protection. A communications lobby at the after end of the compass platform offered what was really wanted, which was a temporary refuge from a brief strafing attack.

After the First World War the Royal Navy debated whether the compass platform should be enclosed to protect the command from weather. An entirely open bridge was ideal for night action, particularly since glass windows reflected the glow of instruments. However, it was far too drafty and it could be too wet. Considerable effort went into designing wind deflectors which would cause updrafts (or prevent downdrafts) and thus keep a bridge habitable. There was also the threat of strafing, which was re-emphasised by bombing trials against the ex-battleship Centurion (1933). Bridges had to be protected without ruining visibility. By 1933 the compass platforms in Royal Sovereign and Barham had been completely enclosed. Ramillies was being given similar treatment, except that the wings of her compass platform had no overhead protection. This arrangement was planned for Repulse and would probably be followed in Warspite, Malaya and Royal Oak (it was not). Charthouses, remote control houses and plotting offices were protected with bulletproof plating as ships came in for large repairs. However, a CO fighting his ship against air attack should be able to see the whole sky, for example to be able to order prompt evasive manoeuvres.⁶ The Royal Navy’s solution was to keep most of the compass platform open, but also to provide a protected shelter.

The Lion bridge structure became the prototype for other British battleship bridges up to the Queen Elizabeth class. This is Centurion, which was built with a simple pole foremast like that in Lion. Like Lion, she had a rangefinder in an armoured hood atop her conning tower. During the First World War the small armoured hood atop the conning tower (with a 9ft rangefinder on an Argo mounting inside the tower) was supplemented by a steel box carrying a 15ft rangefinder.

Once it was clear that a rangefinder should be mounted in the foretop, the foremast had to be stiffened. King George V shows the flanges initially used. The circular foretop housed a 9ft rangefinder. Later another such rangefinder was mounted on the compass platform. During the war the flanges were replaced by tripod legs.

The Royal Navy seems to have been unique in seeing an analogy between surface and anti-aircraft fire: in each case targets had to be chosen and designated to directors and to weapons. A Home Fleet air defence committee organised in the latter part of 1934 pointed out that although a modern battleship might be able to engage as many as six air targets at the same time, her CO would see little of the air situation from his roofed bridge. Air attack would develop suddenly. A dedicated Air Defence Officer (ADO) had to prioritise threats and keep the CO informed. He should be in direct contact with both the principal air lookouts and the CO. The proposed organisation was tested on board Nelson and Rodney. By mid-1936 the ADO idea had been accepted throughout the fleet. Ships under refit were being given suitable open bridges.⁷ Thus in 1936–7 Royal Sovereign and Resolution had air-defence positions occupied by six special lookouts. The ADO had a bearing/elevation transmitter with which he could designate observed targets to the two high-angle directors and also to the pom-poms. The CO or another officer could indicate a target to the ADO position using bearing and elevation transmitters on the compass platform. During the Second World War the ADO office expanded to include a gun direction room (GDR) fed largely by radar, an element of the Action Information Organisation (AIO). The abortive 1920 capital ships and the Nelsons introduced a new type of bridge, a slab-sided tower needed to support the heavy new director control tower (DCT) required for the new fire-control system (see below). In muchmodernised form, this type of bridge appeared both in the new battleships and in the four heavily-rebuilt ships.

The follow-on Iron Duke class had much the same bridge as the King George Vs, but it had a full tripod foremast and also a heavy steel casting atop its conning tower, carrying a 15ft rangefinder (a 9ft rangefinder was inside the conning tower). This is HMS Iron Duke at Constantinople (Istanbul) in 1920, part of an Allied force attempting to enforce the peace settlement with Turkey. She had a main-battery director above her foretop (which was used to control main-battery fire using spotters) in a coaming serving as a screen for lookout positions. A range dial is visible on the fore side of the coaming. One of the two secondary-battery directors is visible on a platform low down one of the legs of the foremast. The superstructure level above it (charthouse/searchlight platform) carried a 9ft rangefinder on each side (in the rest of the class the positions were reversed). The main battery was controlled (using spotting) from the foretop, below the coaming protecting the main-battery director. The structure visible above the compass platform was the ‘primary control position’. It carried a 9ft rangefinder for torpedo control on its roof (one of its arms is barely visible). The steel casting of the 9ft rangefinder is visible above the conning tower, just behind ‘B’ turret and the vertical object to the left is a semaphore. A 9ft rangefinder was carried inside the conning tower. The structure below the foretop was a 6in gun spotting position. The after superstructure carried a 2m (6.56ft) anti-aircraft rangefinder, neither visible here. Each turret also carried a rangefinder: 9ft (as built) in ‘B’ and ‘Q’ turrets, 25ft in ‘Q’ and ‘X’ turrets and 18ft in ‘Y’ turret.

HMS Queen Elizabeth is shown as Grand Fleet flagship in 1918, as photographed from USS New York. She has a main-battery director above her foretop, protected from splinters by a coaming. Inside it is a 12ft rangefinder. The platform immediately below the foretop is for torpedo lookouts. The shelter at the after end of the compass platform carries a 15ft rangefinder for torpedo control and probably also to support tactical plotting. Two 9ft rangefinders on the forebridge or elsewhere in the bridge structure supported the 6in torpedo defence guns. The lower part of the compass platform carried a pair of 6in directors (vertical cylinders, one of which is visible poking above the splinter mattress). The conning tower carried a 15ft rangefinder in a combined director/rangefinder steel casting. A second such rangefinder was aft, for torpedo control (atop the torpedo-control tower). The after superstructure also carried a 2m (6.56ft) high-angle rangefinder. All of the turrets carried 15ft rangefinders, but ships were refitted post-war with 30ft rangefinders for their high turrets, the ends of whose housings projected well beyond the sides of the turrets.

The Royal Sovereigns were conceived with dramatically stripped-down bridge structures. Royal Oak is shown as completed. Note that her main-battery director was mounted below her large oval spotting top (presumably shaped to accommodate a 9ft rangefinder), rather than above it, as was typical. She had 6in directors in the wings of her compass platform. There was no upper steering position; the only helm was inside the conning tower. Revenge and Royal Sovereign had this type of bridge. Resolution and Ramillies, the last to be completed, had something closer to earlier practice, suggesting dissatisfaction with the new type.

Beginning with the rebuilt Queen Elizabeths, the heavy conning tower was eliminated. The heavy-calibre hits it had been conceived to defeat would be relatively few at long range, but at night a ship might be peppered. Without control, she would be a danger in a melee. The tower bridge was therefore provided with a lightly-protected steering position, from which it was hoped the ship would normally be steered, whether or not in action. In Warspite the front and sides were 3in NC, the back 2in NC, the roof 1½in NC and the floor 1in NC. This was intended to resist shells and bombs bursting near the conning position, but not to protect against direct hits.⁸ After C-in-C Home Fleet visited the mock-up of Renown’s bridge at Portsmouth (and then the bridge actually installed on board Warspite) he wrote to DNC that these positions should be protected against close-range attack by destroyers or light cruisers. To keep out 4.7in destroyer shell at 4000 yds would require 4½in C armour, to keep out 6in shell at that range would require 6½in C armour and to keep out 8in shell at 4000 yds would require 9¾in C armour. The shape of the protected position was such that normal impact (i.e., at right angles) was unlikely except over a small area, so the need for additional armour was limited. DNC considered the extra weight acceptable in the rebuilt ships – but not in the new King George Vs. DTD saw little point in protecting the conning position against a direct hit, as it was almost certain that such a hit would put all the enclosed personnel out of action. The King George V class conning position was protected against a direct 6in hit at 12,000 yds. Nothing was done about the other ships.

Similar stripped-down bridge structures were installed in the ‘large light cruisers’. HMS Courageous is shown. As in the Royal Sovereigns as built, the ship was always steered from inside the conning tower, which made the conning tower platform (protected by splinter mattresses) an important conning position, the alternative being the compass platform further aloft. Note the extra protection applied to her lower bridge level and to her stabilised rangefinder (atop the conning tower) and the splinter mattresses around the compass platform and the conning tower (steel splinter protection to the front of the conning tower is less visible). Both directors were on the centreline, the main-battery director above the secondary-battery director. The foretop supported a 12ft rangefinder (added well after completion), visible here and the steel casting atop the conning tower (director/rangefinder) housed the standard 15ft instrument. The turrets had 15ft rangefinders, which were due for replacement by 30ft instruments after the war. The forebridge carried two 12ft rangefinders for secondary battery control, which are not visible here. A separate torpedo control top carried another rangefinder and the ship also had a 2m high-angle rangefinder, probably aft.

Viewed from aft in March 1918, HMS Glorious shows the 9ft rangefinder (later replaced by 15ft) atop her torpedo-control tower (visible just forward of her after triple 4in gun) and her after secondary-battery director. The framework atop ‘X’ turret is for a flying-off platform. The objects visible on deck near ‘X’ turret are fixed torpedo tubes.

On 6 September 1938 the new First Sea Lord Admiral Backhouse, who had supported elimination of conning towers during the run-up to the 1935 battleship designs, reviewed the King George V and Lion class designs. He wanted enough protection to keep out a 5in destroyer shell at short range (both the Japanese and the Germans were using this calibre). King George V was too far along to change, but he wanted Lion modified. Her steering position already had 4½in C on its sides, 3in on front and rear and 2in floor and roof, to meet the 1935 requirement against 6in fire at 12,000 yds. Now sides had to be thickened to 5in, the front to 3½in and the rear to 2½in, at a total cost of 6 tons. The overall shape of the bridge structure was unaltered from that of King George V. CNS also wanted 2in rather than 1in protection for cable trunking.

Initially the bridge planned for Vanguard would have duplicated that of Lion. Controller wanted the protected steering position moved up a deck, incorporating the Admiral’s bridge. DNC had already said that the conning tower should be nearer the compass platform. In March 1940, Assistant Controller proposed reducing the compass platform to a walkway around the conning tower, the latter slightly above the level of ‘B’ turret – something like the old lower bridge in Canada and Royal Sovereign (DNC asked for papers explaining why that earlier idea had failed). In an echo of Captain Nicholson a quarter-century before, Assistant Controller claimed that this arrangement gave a better view at night. Bridge arrangements in French and German capital ships were similar. In October 1940 Home Fleet wanted the opposite; it thought the compass platform too low and too drafty, as it would have the vertical wall of the conning tower immediately abaft it. C-in-C Home Fleet wanted two independent conning positions and two steering positions forward. DNC asked whether adjacent compass platform and conning tower would be considered as two independent conning positions.

Completing at John Brown in 1916, HMS Repulse shows her simplified bridge structure, with only the after part of the compass platform in place. The central part was extended forward and upward. The foremast shows a main-battery director above a secondary-battery director and she has the usual director/rangefinder in a steel casting above her conning tower. The turrets show ridges housing 15ft rangefinders (after the war Repulse had a 30ft rangefinder in ‘A’ turret and both had 30ft instruments in ‘Y’ turret).

In 1943 Vanguard’s superstructure was redesigned to provide a large open bridge above the admiral’s bridge. Behind it would be an armoured bridge looking out over it. Wind tunnel experiments showed that the open bridge had to be at least partly roofed to protect personnel against downwinds and that the entire structure should be square in planform. C-in-C Home Fleet wanted the signal bridge raised to the top platform of the superstructure, the separate armoured bridge eliminated and the entire structure armoured. By this time internal requirements had changed, as radar plotting (Action Information Organisation) evolved. A small open bridge (called first a manoeuvring bridge and then a compass platform) was placed atop the armoured bridge. Its after end was the ADO position with the air lookouts in its wings. The armoured bridge (later called the conning tower) was the alternative conn. The compass platform had a viewing glass through which the plot on the Admiral’s bridge could be seen. The clifflike bridge structure was intended to direct air up past the compass platform, keeping it draft-free.

Photographed by the US Navy while passing through the Gatun Locks of the Panama Canal on 25 January 1927, the newly-modernised HMS Renown shows much of her wartime bridge arrangement, the most prominent change being the roof and windows over the fore part of the compass platform. Note the bulges on either side for chart tables. The ship has a 30ft rangefinder supplementing the earlier 15ft one on the director/rangefinder atop her conning tower and a 9ft rangefinder (for secondary battery control) is visible in an open position on the bridge wing below the compass platform. Atop the foretop is a 12ft rangefinder. The unusually massive foretop was characteristic of this class. Note the extensive wiring connecting the director platforms to the transmitting station below via the legs of the foremast and also the wiring coming down from the foretop. Both forward turrets still have 15ft rangefinders.

HMS Hood was photographed by the US Navy in Gatun Lake (Panama Canal Zone) during her 1924 round-the-world cruise. Her design reflected wartime experience in fleet operations under North Sea conditions. Consistent with the 30° elevation of her 15in guns, she had 30ft rangefinders in her turrets and in the cast steel director/rangefinder atop her conning tower. Her large foretop carried a similar director/rangefinder, in this case equipped with a 15ft rangefinder. Unlike the foretops of earlier ships, it included control positions for the 5.5in battery, in its rear port and starboard areas. Each such position included the 9ft rangefinder which in earlier ships was lower in the bridge structure. The enclosed level below the foretop was for torpedo lookouts. It was flanked by range (concentration) dials, one of which is visible (it was sometimes designated a concentration control position). Below that was a searchlight platform. It carried a torpedo rangefinder (removed during the ship’s 1927 refit) on its forward part, with two searchlights on the parts visible between the tripod legs. The bridge structure below that was similar in principle to earlier ones, but it was plated in to form a simpler structure. As in the past, the upper level, which was roofed over, was the compass platform, from which the ship was conned. Barely visible at the after end of the roof is a 9ft rangefinder. At its after end was the charthouse, which had to be adjacent to the compass platform because it housed the tactical plot. The level below, with bridge wings, was the admiral’s bridge and signal bridge – Hood was conceived as a flagship. The windowed level below that contained the captain’s sea cabin. Visible protruding through the awning at the bottom of this level (next to the leg of the tripod mast) is the starboard 5.5in director. The cylinder alongside the searchlights between the two funnels is one of three torpedo-control towers, with a 15ft rangefinder (a third tower was aft). The planking atop ‘B’ turret was for the flying-off platform there.

Guns

British (and foreign) pre-1914 thinking about capital ship tactics was based on the perception that guns were cumulative weapons: it would take considerable time and considerable battering to destroy or neutralise a ship. British officers had ‘knock-down’ tables showing how many minutes of fire it would take to disable particular ships. Required time was set partly by the hitting rate, so as range increased it was assumed that knock-down time would increase considerably. Success in protracted battle was expected to depend not so much on armour penetration as on smashing effect. The British also hoped that their high explosive Lyddite would create disabling toxic effects.

Hood as completed in 1920, her compass platform not yet roofed over.

Thus the destruction of the three British battlecruisers at Jutland by a few hits (possibly one each) was a shocking surprise. Afterwards the Germans claimed that their superior shells had penetrated British armour with devastating effect. However, it seems clear in retrospect that these penetrations would not have been fatal had the British not adopted what amounted to suicidal turret practices. The British were also surprised that German commander Admiral Scheer was concerned mainly with disengaging once as he spotted the main British fleet. The British needed a different kind of shellfire which could quickly immobilise an enemy so that he could be pounded to pieces or sunk by torpedoes. That was the significance of the new generation of armour-piercing shells introduced at the end of the war.

The battlecruisers blew up at Jutland not because the Germans had magic shells, but because the British had adopted extremely dangerous magazine practices because German shellfire had been so ineffective in the previous Dogger Bank battle. Moreover, British shells did penetrate German magazines (for example in the battlecruiser Seydlitz) in both battles, causing devastating fires. The Germans never took special anti-flash precautions because their powder, always contained in metal cases, could not generate the kind of flash which detonated British bagged powder. However, had the British followed the accepted precautions at Jutland, ships would have lost individual turrets without blowing up. The evidence is that HMS Lion lost ‘Q’ turret from a hit probably much like that which blew up her near-sister HMS Queen Mary; Lion’s captain and gunnery officer refused to relax the rules in order to fire more rapidly. After the First World War, the Royal Navy reverted to its earlier view that shell damage would be cumulative. Once the magazine problems revealed at Jutland had been cured, it sought to fight at a range (about 15,000 yds) at which it expected to achieve a high hitting rate. It doubted that the long range fire practised by the US and Imperial Japanese Navies was practical in this sense.

Hood is shown after her 1931 refit, with her foretop considerably extended to provide 5.5in director towers (note the rangefinder) and, abaft them, positions for pom-pom directors (at this time only the starboard one was occupied). During the 1934 refit these directors were moved to the positions occupied by the 5.5in directors, then moved again during the 1936 refit. An octuple pom-pom, which is barely visible, was mounted on the shelter deck abaft the 5.5in gun visible there. The two wings built out from the torpedo lookout position under the foretop were used to control the searchlights on the platform below. The new level added atop the compass platform was for torpedo control, with a 9ft rangefinder (not visible in this photograph). Note the vertical screen, abaft the conning tower, intended to protect the 5.5in battery from 15in gun blast. The object atop the after searchlight structure is a high-angle director, added at this time.

Nelson is shown newly completed in 1927. The angle of the ship made both torpedo-control towers visible and both signal lights on this side of the signal deck can be seen. The objects atop the stub mast above the tower bridge are intended for an interim high-angle control system (Nelson received the full system during a May to June 1930 refit). Note that at this point the flag bridge did not yet extend over the compass platform. One of the two 9ft rangefinders on the roof of the tower bridge is visible.

British capital ship main-battery guns consisted of an inner (A) tube surrounded by reinforcing tubes and hoops, their letters indicating how far they were from the A tube. A liner inside the main A tube carried the gun’s rifling. It could be replaced relatively easily. The main-battery guns of ships described in this book up to the 16in on board the Nelsons were wire-wound. In this technique, invented by an American in 1855, the wire was wound, under great tension, around the A tube; further reinforcing tubes surrounded it. Areas over which wire had been wound were subject to uniform stress, but only in the radial (outward-pointing) direction. Opponents of wire-winding claimed that these guns had lengthwise weaknesses and tended to droop and even to whip when fired. The British claimed that wire-wound guns were inherently lighter than built-up ones (using only tubes and hoops). That seems to have been true about 1905, but not by 1914. British guns of the Second World War era were built-up of multiple tubes, the prototype being the 12in Mk XIV developed in hopes (which proved abortive) that this calibre would be adopted as the maximum under the 1930 London Naval Treaty.

Shells were propelled by nitroglycerine-based ‘smokeless’ powders introduced from the late 1880s, the British version, adopted about 1890, being cordite. These powders and particularly their improved descendants (such as the British Modified cordite [MD]) burned relatively slowly, making it possible for longer guns to reach high muzzle velocities, The muzzle velocities of heavy guns increased from about 2200ft/sec in the late nineteenth century to about 2500ft/sec in 1900 and up to as much as 2800ft/sec in about 1903. Unfortunately nitroglycerine could make powders quite unstable. They could, for example, deteriorate badly when warm. British ships destroyed by spontaneous powder explosions included the battleships Bulwark (26 November 1914) and Vanguard (9 July 1917) and the armoured cruiser Natal (30/31 December 1916). Claims that unstable powder had been responsible for the disasters at Jutland seem to have been part of a larger evasion of the reality that it was due to suicidal magazine practices.

HMS Nelson is shown in the Panama Canal in 1931. She was a radical departure from previous practice, hence the subject of enormous interest to the US Navy, whose officers and enlisted men visited her and wrote voluminous reports (which survive in the SecNav/CNO correspondence in the US National Archives). Not only did she not have an open-topped compass platform, it was not even the highest level of her bridge structure. The upper level of the tower was the flag (admiral’s) bridge, with an adjacent flag plot. The compass platform was the level below it (note the bulges for the chart tables). US visitors found the view aft from the compass platform (navigating bridge) decidedly restricted, but were told that the pivoting point of the ship was about at ‘B’ turret and that anything which came abreast the bridge could be passed clear unless the rudder was put hard over towards it (one officer said that manoeuvring was confusing because the pivoting point was well forward of the bridge). The level below the compass platform was the signal bridge, carrying four signal lights (visible behind the sailors) but not controlling halyards for flags. This level also contained cabins, including the captain’s sea cabin. In contrast with previous practice, the director atop the conning tower did not have an integrated rangefinder. The new fire-control system on board the ship employed DCTs combining the functions of director, rangefinder and control (spotting and correction of fire), the forward 16in DCT being mounted at the fore end of the bridge tower. The tower structure was adopted specifically to support the heavy DCTs rigidly enough. The other two DCTs atop that tower were for 6in control. In addition to DCTs, this open platform carried a 9ft rangefinder on each side (the starboard one is just visible). A short mast in the centre of the tower was intended for the high-angle control system, not visible here. The short control tower abaft the tower bridge, carrying a rangefinder, was for torpedo control; the ship was armed with the long-range 24.5in torpedo.

Nelson is shown on 23 May 1944, prior to her big refit in the United States. During her last pre-war refit (June 1937–January 1938) she was fitted with a second high-angle director atop an enlarged stub mast, evident here (because she was never heavily refitted before 1939, her sister-ship Rodney spent the war with a narrower mast carrying only a single high-angle director). The high-angle and main-battery directors, but not the 6in directors, are equipped with radar: Types 285 and 284, respectively. By this time the torpedo directors (and tubes) were gone and the ship had considerable additional light anti-aircraft firepower in the form of Oerlikon guns. The 4.7in anti-aircraft guns, replacement of which was often discussed before and during the war, had been given splinter shields (note the gun visible in front of the pom-pom abreast the funnel). The ship’s foremast carried the receiving antenna of a Type 281 air-search radar.

Gun accuracy was affected by dispersion: how well a gun could continue to put its shots into a particular place. By 1905 there was evidence that at the highest muzzle velocities guns sometimes whipped on firing, ruining their accuracy. For example, the 12in/50 Mk XII was disliked for excessive dispersion. On the other hand, the flatter a gun’s trajectory, the greater the fire-control error it could tolerate. This quality was measured by the danger space, the range error in which the target would still be hit.⁹ Higher velocity meant a flatter trajectory – but it could also mean much greater wear. When the Royal Navy returned to building capital ships with the King George V class, the question was whether to seek high muzzle velocity, for example using a lighter shell.

The powder charge in the gun produced, roughly, a fixed muzzle energy which could be divided between shell weight and velocity. A lighter shell would be fired at higher velocity, but it would lose velocity (energy) more quickly. The lighter shell would go further faster and would descend at a shallower angle (wider danger space). The slower, heavier shell would retain more of its velocity out to greater ranges, hence would penetrate armour better at greater ranges, it would have greater bursting effect and gun wear would be considerably less.¹⁰ This combination was the logic of the 13.5in and 15in guns in British service. The Germans opted for a much lighter shell (1653lbs) and higher velocity in their First World War 15in gun.

Photographed in Hampton Roads after a US refit on 2 June 1943, HMS Queen Elizabeth shows the next stage in British capital-ship bridge development. Like Nelson, she has a tower bridge intended to provide rigid support to her directors, in this case a main-battery DCT and two dual-purpose directors on the platform above the bridge structure. The compass platform has been brought back to the upper bridge level. Visible abreast the barbette of the main-battery director are two target designators of the air-defence position, which had to be located adjacent to the command on the fore end of this level. The level below is the admiral’s bridge. The object at the after end of the flag bridge is a pom-pom director (with Type 282 radar) controlling the octuple pom-pom visible abaft the tower bridge. At the fore end of the bridge is a barrage director with a Type 283 radar. The slits below indicate the protected steering position, a subject of considerable controversy later on. All of the directors have related radars with ‘fishbone’ antennas: Type 285 on the two dual-purpose directors, Type 284 on the main-battery director. The ‘lantern’ above the dual-purpose directors is for a Type 273 surface-search radar; the antenna for the ship’s air-search radar is not visible in this photograph. Oerlikons populate the signal bridge at the same level as the steering position.

HMS King George V is shown in the Severn River, Maryland, while delivering Lord Halifax to the United States as ambassador, January 1941. She has the open compass platform British naval officers wanted; sometimes it was covered over against weather, but the open top was wanted for anti-air actions. A shelter was provided at the after end of the platform. The wing visible jutting out from the after part of the compass platform held air lookouts, each of which could indicate a target using the devices visible here. Below the compass platform is the admiral’s bridge, with a rangefinder (for tactical plotting) visible in the bridge wing. Below that, slits indicate the protected steering position, with charthouse adjacent to it. The level below housed the admiral’s sea cabin. The two objects in tubs are pom-pom directors, as yet without their range-only Type 282 radars. The two octuple pom-poms they controlled are visible abaft the bridge structure. On the signal bridge below the admiral’s bridge can be seen two signal lights and a 44in searchlight for night action. The director visible above the compass platform controlled the ship’s main battery (two dual-purpose directors, for the 5.25in guns, were mounted on the pedestal emerging from the rear end of the tower bridge structure). It carries the two aerials (only the upper one is visible) of a Type 284 range-only main battery radar; as yet the dual-purpose directors lack any radar. Visible atop ‘B’ turret is a UP (unrotated projectile, i.e., rocket) launcher in its blast shield. (Naval Institute Collection)

The British solution was to accept limited muzzle velocities (typically about 2500ft/sec), usually with heavy shells. In 1918 DNO pointed out that the Germans seemed to be achieving at least the same accuracy with little wear at 2800ft/sec, using built-up guns. Generally the British chose a combination of shell weight and velocity offering accuracy, good performance against armour at fighting ranges and reasonable gun lifetime (usually measured in equivalent full charge shots or EFCs). Gun size and weight had to be such that it could be mounted in a turret of reasonable size.¹¹ DNC’s account of the design of the Queen Elizabeth class, for example, stressed the considerable effort required to provide enough structure to support their unusually massive twin 15in turrets. Other navies did not always make the same choices; for example, the Italians chose very high velocity and short gun lifetime in their Second World War 15in gun.

DNO pointed out in 1935 that the extra velocity associated with a 50- rather than 45-calibre gun mattered for armour penetration only at and beyond 20,000 yds, as below that range both 45- and 50-calibre guns could defeat plates up to 13½in thick. As for danger space, the longer higher-velocity gun enjoyed an appreciable advantage only below 10,000 yds – where the danger spaces of both 45- and 50-calibre guns exceeded 100 yds. On the other hand, the extra 5 calibres would impact turret design. Lengthening the barrel would move the gun’s centre of gravity further from the breech face. In that case the gun would have to be supported further from the breech and the roller path considerably enlarged (and turret weight considerably increased). Hence the choice of 45 calibres for the 14in gun arming the 1936 battleships. What DNO did not say about the virtues of lower-velocity heavy shells is interesting. At very long ranges, such shells would hit deck armour with extra force.¹² That is why the US Navy adopted them.

The builder’s model of HMS Vanguard, formerly in the Science Museum, London, shows the ship’s bridge, in effect the culmination of British thinking about battleship command. Arrangements were extensively revised both to improve command and control and to improve performance in wind (using wind-tunnel experiments). The side of the compass platform was the air defence lookout position, which in earlier ships was located abaft the compass platform. Abaft and inboard was the ADO’s position, with a target designator. Another target designator is visible at the rear of the compass platform proper, in the centre of the forward upper bridge. Slits indicated the protected steering position directly under the compass platform. Abaft it was the charthouse, with the captain’s sea cabin on the port side. Below was the admiral’s compass platform, with the bridge plotting room behind it. (Author)

HMS New Zealand shows a standard turret configuration of around 1914, with three sighting ports and a protected 9ft rangefinder occupying the ridge at the rear of the turret. This and all other British battleship turrets prior to Hood had three sighting hoods: two for the gunlayers and one containing two sights in the middle for the trainer who pointed the turret. At least in theory, the gunlayers were expected to maintain continuous aim on the target, using increasingly responsive hydraulic controls. The use of sighting ports just above the face of the turret made it impossible to superimpose turrets. However, once periscopic sights were introduced in HMS Neptune, the guns of an upper turret could be fired close to the axis of the lower one without disabling the turret operators. In Hood the sights were at the front of the turret with ports in the turret face plate. In Nelson the periscopes were eliminated altogether, but a local director sight was let into the side of the turret. (Dr David Stevens, RAN Seapower Centre)

During the decade leading up to the First World War, standard armour-piercing (AP) shells employed caps as antidotes to the new lightweight armours, to the extent that they seemed to revive the prospects of medium-calibre rapid-fire secondary guns. About 1905 it seemed that at the assumed battle range (4000 to 6000 yds) all practicable armour was useless against heavy capped AP shells. Armour was retained mainly against high explosive (HE) shells fired by smaller weapons. On this basis armoured cruisers and battleships were on much the same footing. As heavier guns entered service, this logic reversed: thin armour was penetrable, but heavy armour was once more worthwhile.

Shell development continued after the war. In 1935, in connection with the design of the new King George V class, DNO provided graphs of current shell performance as well as of the performance of projected 15in guns (which several other navies planned to use, despite the attempt to fix maximum calibre at 14in as part of the new London Treaty). It appeared that the figures for the projected 15in gun represented an advance in striking power over that of Hood equivalent to about 6000 yds greater range against a 13½in belt. Another 250ft/sec in muzzle velocity might buy 5000 more yards, with extremely bad consequences for a ship designed against current 15in guns. DTD and DTSD both saw these data as a reason to consider a new gun (not to mention much more armour). DNO pointed out that of the 6000 yds, only about 1100 yds was due to increased muzzle velocity; the rest was due to improvements in shape of head and in piercing qualities of more modern shells – which could of course be fired by existing ships with 15in guns.

HMS Emperor of India shows her rangefinder covers and her periscope hoods. She is hoisting out a paravane, developed during the First World War to protect against moored mines. This is presumably a post-war photograph, since neither turret appears to show deflection markings.

Once guns ‘overmatched’ armour (which generally meant that armour was thinner than one calibre), they could penetrate at increasing range. For example, in 1912 retired Admiral Fisher likened the new 15in gun to the 12in guns firing capped ammunition which had justified the thinly armoured battlecruiser in 1905.

Fire Control

Gun performance in action was determined by fire control.¹³ Between 1904 and 1914 the Royal Navy made a greater effort in this area than any other navy. From about 1904 onwards, it developed a method of firing effectively at what were then considered long ranges. Its system combined spotters aloft (to estimate how far off target the current solution was) with calculators in a transmitting station under armour. The transmitting station computed the range and train angle to be used by the gunners. In Dreadnought and her immediate successors the spotting position was a fire-control top at the masthead, containing a rangefinder and instruments (Dumaresqs) used to estimate the rate of change of range.

The first stage of fire-control improvement was the simplest: cancelling out the firing ship’s roll and later its pitch and yaw.¹⁴ In 1899 Captain Percy Scott discovered that the best gunners compensated for a ship’s roll by elevating and depressing their guns to point continuously at the target. That was not too difficult for secondary guns, but for heavy guns it required delicately-controlled machinery. Guns were elevated and depressed by hydraulic rams or pistons and trained by six-or seven-cylinder hydraulic engines or swashplate engines. Six-cylinder training engines were fitted in 12in dreadnought mountings except aboard Colossus, Hercules and Agincourt. The 13.5in Coventry Ordnance Works (COW) mountings had COW-designed seven-cylinder engines. All other dreadnoughts and super-dreadnoughts had swashplate engines, which offered smoother motion. They could be controlled either by a valve, which regulated hydraulic pressure or by a hand control which moved the swashplate itself (its angle to the pistons of the engine determined how rapidly the shaft revolved).

HMS Neptune shows her prototype director, the cylinder on the platform under her foretop, about 1912, when she was fleet flagship.

The Royal Navy found hydraulic machinery better than electric for such delicate work (the US Navy preferred electric turret machinery). Unsatisfactory electric turret machinery in HMS Invincible was replaced by hydraulics in 1912. Hydraulics were liked because they were simple and reliable; their movements were noiseless and steady and completely under control even with the heaviest loads. Pressure was always available once the pumps were started. The system was cold, hence could be used in magazines and in shell rooms. However, it was also inefficient, requiring the same power whether fully loaded or not; and it was cumbersome, as it required large pressure pipes and even larger exhaust pipes leading back to the tanks. Water in it could freeze in cold weather; joints had to be kept watertight; valves could score.

The director, also invented by Scott, was an alternative way to cancel out roll and pitch. Scott came to doubt heavy guns could be continuously aimed, so he turned the problem inside out. A single sight aloft would be continuously-aimed. Its single key could fire a salvo when guns at fixed elevation came ‘onto’ the target. Instead of calculating elevation and bearing for each turret, the transmitting station would pass its orders through the director, which would incorporate corrections (depending on turret position and target range and bearing) for each turret. Crews would apply these orders. Since all of the guns would be firing at the same target using the same fire-control solution, the director could apply spotting corrections to all of them. This was a brilliant invention. Its only major flaw was demonstrated at Jutland: the director might not be focussed on the target the ship’s spotter was observing. The post-war British fire-control system solved that by placing the spotter (control) in the director, which became a director control tower (DCT). It first appeared in the Nelson class.

The prototype director was installed on board HMS Neptune, which was fleet flagship at the time, in 1911. Although initial trials were somewhat disappointing, they showed that the director was worthwhile and an improved version was tested on board HMS Thunderer in 1912. It had three operators: sight-setter, layer and trainer. The layer fired the ship’s guns, just as a gunlayer in a turret fired his. Trials against Thunderer’s sister-ship Orion were spectacularly successful and during 1913 the Admiralty placed two large orders with Vickers, to be spread over the next two fiscal years, one for twelve ships (King George V and Iron Duke classes plus the battlecruisers Queen Mary and Tiger and the earlier battleships Monarch and Thunderer) and one for seventeen ships (all remaining dreadnoughts except Conqueror and Australia).¹⁵ The production prototype was installed on board HMS Ajax in 1913. On the outbreak of war in 1914 directors equipped the three prototype ships (Neptune, Thunderer and Ajax) and five others (Iron Duke, Marlborough, King George V, Centurion and Monarch). Installations were then suspended for three months, probably because they seemed to require extended time in a dockyard. Scott helped develop an installation which could be made largely by a ship’s own crew and the programme resumed. By the time of Jutland only the two battleships bought at the outbreak of war, HMS Erin and Agincourt, had not yet been equipped.

All of these directors were encased in small vertical cylinders pierced for their sights. During the First World War some directors were modified with small shields (looking like eyelids) over the opening. They were probably splinter protection (masthead directors had coamings around their bases for the same reason). Initially main-battery directors were typically placed at the head of the foremast, above the spotting top. Later they were often bracketed to the foremast below the spotting top. Ships with their masts abaft their forefunnels were a special case. Hercules was unique in having her director atop her bridges, above and abaft her compass platform. Dreadnought had hers atop her foretop. The Orions had theirs on conventional brackets just below the foretop, in at least two cases with large coamings to protect against rising funnel smoke (the director was almost directly over the forefunnel). Beginning with the Queen Elizabeth class, ships had a second director in a cast-steel armoured hood atop the conning tower. The hood also carried a rangefinder (in the King George V and Iron Duke classes and Tiger it was just an armoured rangefinder). This rangefinder was gyro-stabilised using a mounting made by Argo.

The main visible wartime development was director control for secondary batteries, first proposed for the two latest battlecruisers Queen Mary and Tiger. In January 1915 director control was ordered for all ships with 6in secondaries. Like main-battery directors, these were small vertical cylinders; ships typically had one on each side.

Another important wartime director development was gyro-controlled fire, work on which began in February 1915. A prototype was fitted to Centurion in September 1915 and an improved version to Iron Duke in March 1916. That month C-in-C Grand Fleet asked that all director-controlled ships be fitted with gyros as soon as possible. Production began in April 1916, before the first formal orders were let (22 August 1916).

The spotting position was separate from the director. When ships were fitted for director control of their secondary batteries, that entailed both installation of additional directors and also a new control (spotting) position, typically much lower than the spotting top, because the secondary guns fired at a shorter range.

In January 1915 Admiral Jellicoe (who as DNO had strongly advocated the director) pointed out that experience had shown that director fire was significantly slower than independent fire when conditions were favourable, particularly in ships with quick-acting elevating valves and (hydraulic) presses. The director waited until all guns were ready and then waited for the right moment to fire. It offered advantages only under some difficult conditions – in half light, at night, in thick weather and in rough weather when gunlayers suffered spray interference. A ship could fire more rapidly if guns were independently aimed, compensating for the ship’s roll by continuous aim. The greater the range, the greater the importance of the director. Conversely, a Royal Navy fighting at shorter ranges could exploit its greater ability to maintain continuous gun aim to get a higher firing and hitting rate. Ships with directors had to be prepared to use independently-aimed fire.

On the other hand, the director could help solve the problem of target designation. The captain on the bridge or in the conning tower chose the target. He had to get that information to the guns and to the separate fire-control party aloft – not to mention to the transmitting station below. Once firing began, the numerous enemy ships would be shrouded in gunsmoke. What if guns and controllers were concentrating on different targets? The control party would try to correct fire against one target on the basis of splashes from shots fired at the other. The ship would never hit anything. Jutland showed that the director was only a partial solution. Ships were provided with Evershed Bearing Indicators (EBIs) so that the CO could designate a target to the director by passing its bearing.

Fire control required accurate range data. Dreadnought and her immediate successors had 9ft rangefinders in their spotting tops (typically they are not visible in photographs). This type of rangefinder was installed on board all ships up to the 1911–12 programme (Tiger and Iron Dukes). Additional rangefinders were fitted in turrets for local control in the event that the main rangefinder was knocked out. This installation was approved by mid-1912 for new super-dreadnoughts, beginning with the King George V and Queen Mary classes. In 1913 installation was approved for all battleships, but it began only with the outbreak of war. At that time, Orion and earlier dreadnoughts had only one turret rangefinder and Lion and Princess Royal had only two. Ships of later programmes were completed with a rangefinder in each turret. In 1914 the turret rangefinder programme was incomplete, HMS Lion having the greatest number. Director control helped ensure that all turret rangefinders were pointing at the same target. Once ships had multiple rangefinders, their data had to be averaged to improve accuracy.

The rangefinder atop the conning tower was introduced in the 1909–10 ships (Lion and Orion classes). It later ships it was an armoured stabilised rangefinder (Argo mounting, Barr & Stroud coincidence instrument). Beginning with the Queen Elizabeth class, the armoured hooded rangefinder was converted into an armoured director.

The Queen Elizabeth and Royal Sovereign classes were completed with the improved 15ft rangefinder. It was installed on board other ships after the outbreak of war. These classes had 15ft rangefinders in each turret and in the armoured control tower and two 9ft rangefinders (foretop and torpedo-control tower).

In October 1915 Admiral Jellicoe asked that new capital ship designs incorporate longer-base rangefinders than the current 15ft: a longer base translated into reduced range error.¹⁶ At this time ships typically had 15ft rangefinders in their turrets, 9ft rangefinders in the armoured hoods atop their conning towers and 12ft rangefinders aloft in their spotting tops. The aloft rangefinder was considered the largest which could occupy that position. It appeared that in existing ships the 9ft in the armoured hood could not be replaced by a 15ft instrument as in the 15in battleships. The largest rangefinder then in prospect was a 22ft type which could be built out of tubes similar to those used for the 15ft. A 28ft instrument did not enter production because it would have to be made in three pieces. On 11 December 1915 DNO asked that new capital ship designs incorporate a long-base rangefinder outside the control tower, the rangefinder in the tower being omitted. On 7 February 1916 Controller approved one 22ft rangefinder for any new capital ship design.

As redesigned in 1916–17 Hood introduced a 30ft rangefinder to deal with much greater ranges. She had 30ft rangefinders in each turret and in the armoured hood above the conning tower, a 15ft rangefinder in the foretop and two 15ft rangefinders for torpedo control (on two directors between the funnels and on one torpedo-control tower aft). In October 1917 further orders were given so that each capital ship would have two long-base rangefinders (orders totalled seventy-one 30ft and twenty-four 25ft), but none of the new rangefinders had been delivered by the end of the war.

A major visible wartime development was equipment to assist in concentration firing, in which some ships might be firing at a target they could not see. Ships were fitted with range dials, to indicate their firing ranges and their turrets were marked so that others in a group could see the bearings at which they were firing. The range dials recalled pre-war range drums which similarly displayed ranges at mastheads.¹⁷ In addition to the visible fittings, ships had Type 31 gunnery radios intended to pass range and other data.

The post-war solution to ensuring co-ordination of rangefinding, control and the director, first employed in the abortive 1920 capital ships and then in the Nelsons, was to combine the two functions in a director control tower (DCT) carrying both director and rangefinder. The DCT was associated with a new-generation analogue computer, the Admiralty Fire Control Table (AFCT). The DCT could not be supported adequately by a tripod mast. Instead, it had to be mounted atop a tower bridge. The tower foremast/DCT combination appeared in all of the abortive capital ship designs of the 1920s, in the new battleships and in the massively rebuilt Queen Elizabeths and Renown. However, in 1940 Hood had her foremast director converted into a lightweight DCT in its original position atop her tripod mast. Capital ships which did not get new bridge structures had neither the new type of DCT nor its accompanying AFCT.

Guns were aimed on the basis of assumed enemy current range, course and speed. A miss showed that the original estimates were incorrect. The observed error had to be fed back to correct the original estimates of enemy course and speed. What the spotter saw – how far off the shots were – depended on both enemy speed and course, neither of which was measured directly. The fire-control system had to predict target position both to aim the guns (i.e., to lead the moving target) and to evaluate the results of each shot or salvo based on incomplete current information. The only measurable data were current range and bearing. Range rate could be estimated based on estimated enemy course and speed.

Before 1914 navies typically estimated future range by applying an estimated range rate to a clock (the widely-used type was the Vickers Clock).¹⁸ The Royal Navy’s Dreyer Table was a sophisticated version of this practice. Ranges provided by rangefinder operators were automatically indicated (by pricking) on a moving paper. The corresponding range rate was the slope of a line drawn through the range plot. It could be set on a range clock, the outputs of which were indicated by an automatically drawn line of estimated ranges, which could be compared to measured ranges indicated on the plot. The comparison made it possible to apply corrections, which were necessary because actual range rates were almost never constant. A Dreyer Table generally also incorporated a bearing plot, but range and bearing data were not combined in any way. The Dreyer Table was conceived as a means of assisting a fire-control officer observing fire, indicating how he might correct range.¹⁹ Unfortunately the line on the plot could not really be straight, because range rate varied with range, so a Dreyer Table solution would eventually fail.

The range plot had an unexpected virtue. British capital ships had multiple rangefinders, which gave differing data. When their outputs were all indicated on the same range plot, an operator could visually average rangefinder data and he could see at a glance if one set of data were clearly in error. The plot was valued as a quick indication of the gunnery situation: ranges, estimated firing range and spots.

The Germans seem to have been aware that the British were relying on a plot-based clock; their tactical countermeasure was to zig-zag. That created sudden changes in range rate, which the Dreyer Table could not follow. The Germans’ own clock-based system, which did not employ a plot of any kind, seems to have been better adapted to such manoeuvres. At the end of the First World War the Grand Fleet Dreyer Table Committee concluded that it was pointless to rely on range rates. The most valuable feature of the Table turned out to be its bearing plot, which could detect sudden changes of target course.

While the Dreyer Table was being developed, the Royal Navy pursued a much more sophisticated concept: to create a model (an analogue) of the engagement, separate elements representing shooter and target. Once set with target course, speed and initial range, the model generated (computed) current and future target position, hence range and bearing. Current data could be compared against observed reality and target course and speed adjusted until they matched. The resulting solution remained valid until the enemy manoeuvred. Then it could recover faster than a rate-based device. All major navies used this approach during the Second World War.

It was invented by Anthony H Pollen, who developed his Argo Clock computer under a monopoly agreement with the Admiralty. In 1912 the Admiralty planned competitive trials between the Argo Clock and the Dreyer Table, but abruptly cancelled them. Five ships equipped with Argo Clocks for the trials retained them throughout the First World War: Queen Mary and the four King George V class battleships. First Lord Winston Churchill told the Commons that the navy had found a less expensive and superior alternative to Pollen’s expensive device, but it appears that the Dreyer Table was bought as an inexpensive interim device while an alternative analogue computer was developed by Barr & Stroud.

Money was very tight. Barr & Stroud depended heavily on Admiralty business for its main product, rangefinders, so would have been more amenable than Pollen to cutting the price of its computer. That the British Government did not think that war loomed would have made purchase of the less effective Dreyer Table perfectly acceptable at the time. War intervened before Barr & Stroud could complete development. The monopoly agreement with Pollen made the Admiralty’s manoeuvre embarrassing at the least.

Given war experience, the Admiralty chose to develop its own computer (AFCT) based on Pollen’s ideas and some of his technology.²⁰ Associated with the new AFCT was an aloft DCT slaved to the computer, providing the feedback necessary to obtain a good fire control solution. The Royal Navy adopted massive tower bridge structures after the First World War specifically to accommodate the heavy new DCTs. It also developed means of moving DCTs and turrets under the control of the AFCT, a major achievement.

Because the war had slowed development, Barr & Stroud could not offer the Admiralty an alternative to the AFCT. It had to be content with the export market. Its system became the basis of post-war Italian and Japanese fire control and, it appears, German fire control based on an Italian prototype. In this sense Bismarck sank HMS Hood using a more sophisticated British system against a less sophisticated one – a horrible own-goal.

The new analogue technique was far more automated than the system in which the Dreyer Table had been embedded. That, much more than the technicalities of the new computer, may have been its greatest virtue. It required far less training and it got onto a target much more quickly. As one of the five test ships equipped with Pollen’s computer, HMS Queen Mary reportedly made the best shooting among the battlecruisers at Jutland. Since the battlecruisers’ problem seems to have been very few opportunities to practise, her superiority may reflect the difference between the heavily human element in a Dreyer Table system and the far more automated approach represented by Pollen’s computer.

This automation probably explains why the new battleship HMS Prince of Wales, with a nearly untrained fire-control crew, performed so well when she faced the Bismarck (and, for that matter, why the raw fire-control crew on board Bismarck did so well in her initial battle). At least in theory, an automated system made it possible to hit on the first or second salvo. Using the much less automated Dreyer Table, the gunnery officer of HMS Hood remarked to a US officer that he could imagine not getting onto the target until he had fired several salvoes. Hood’s gunnery officer assumed that he could absorb damage while his higher rate of fire and superior shells destroyed his enemy. Hood was just getting onto her target when she was destroyed. The surprise was not that Bismarck hit Hood so quickly, but that one salvo destroyed her.

Armour

British designers indicated armour and other steel thicknesses not in inches but in pounds, on the basis that a square foot of 1in steel weighs about 40lbs. Thus a 320lb plate was nominally 8in thick. In fact steel is slightly heavier (40.8lbs per square foot of 1in steel), so a 240lb plate is actually 5.88in rather than 6in thick and a 360lb plate 8.82 rather than 9in thick. During the 1930s, when adherence to strict Treaty limits was particularly important, constructors sometimes referred to ‘light rolled’ plates – presumably plates rolled to a specified weight rather than to the thickness implied by the nominal weights.

The British capital ships described in this book used Krupp Cemented (KC) or face-hardened side armour, which had displaced earlier types because it was so much lighter for a given degree of resistance. As an indication of how much difference KC made, the Admiralty Gunnery Manual (Vol I: CB 142) of 1915 equated 5¾in of standard Krupp armour to 12in of all-steel armour and to 15in of wrought iron armour when resisting uncapped projectiles. By 1919 the British called cemented armour simply C armour, their version being superior to the original Krupp type. Because it produced a layered plate, cementing could not be applied below a particular thickness, which was 4in in 1928.²¹ At that time the standard for 15in C armour was to resist a 16in shell at a striking angle of 30° and a velocity of 1530ft/sec, corresponding to a range of 13,200 yds. The 13in and 14in plates were to resist 15in shell at, respectively, 1480 and 1560ft/sec (striking angle 30°), corresponding to ranges of 17,500 and 15,200 yds, respectively.

The cementing (carburising) process produced an extremely hard surface layer, a relatively deep hardened layer and a tough rear layer which absorbed the shock of impact and protects the plate as a whole from being punched through by the broken face. The hardened face was intended to so damage the attacking shell that it was no longer effective. It was most effective when the shell struck nearly at right angles (‘normal’) to the plate.²² During the run-up to the First World War the British and others improved KC steel by ‘normalising’ it, somewhat reducing surface hardness to toughen the plate. Krupp had concentrated on hardening the face of the armour at a cost in toughness. Normalisation improved resistance to capped shells. Krupp did not test its own armour against such shells and it did not discover the value of ‘normalisation’. Hence British (and other) armours produced before and during the First World War were superior to German ones (Krupp normalised its plates after the war). Immediately before the Second World War the British were producing plates with a deeper hardened layer using molybdenum. At that time they thought they were merely keeping step with increasingly effective projectiles. Others considered their Second World War face-hardened armour the best of any.²³

Capped shells were introduced about 1900. The soft steel caps originally used were intended to flatten so as to protect the shell so that it would not shatter on impact. They were most effective below 15° striking angle, the practical limit being 20°. Later hard caps were effective over a much wider range of striking angles, corresponding to longer ranges. Also, as they were destroyed they dug a pit in the armour, damaging it and also making it less likely that the shell would either ricochet or turn away as it struck. Caps were effective against face-hardened armour, but usually reduced performance against homogeneous armour.

Unlike side armour, deck armour had to be ductile, shells and other projectiles (such as splinters and fragments) typically hitting very obliquely. The British initially used Krupp Non-Cemented (KNC) steel for their thin deck armour, but by 1915 it had been superseded by HT (High-Tensile [Strength]) steel containing a percentage of silicon. HT (or HTS) was considered superior and it was considerably less expensive.²⁴ It was the first of a series of homogeneous armours suited to thin plates and to deck armour. After the First World War this type of armour was called NC (non-cemented). Post-1918 thicker NC armour was developed specifically to resist long-range shellfire. A 4¼in NC plate (170lbs) was expected to resist a 12in APC shell striking at a 60° angle and at 1175ft/sec, corresponding to extreme range (the corresponding standard for 5¼in plate [250lbs] was a 16in shell at 1230ft/sec). At some point the British began to refer to NCD (Non-Cemented Ductile) armour.

The British also considered coal bunkers a form of protection. In the 1880s 2ft of coal was considered equivalent to about an inch of mild steel. About a decade late DNC Sir William White resisted calls for side armour in cruisers on the grounds that a belt of coal bunkers offered better protection (he changed his mind when lightweight armours such as KC became available).

Torpedoes

Battleships as well as smaller craft were armed with torpedoes. One of Admiral Fisher’s key arguments in favour of dreadnought battleships was that their heavy guns could hit beyond the range of enemy battleship torpedoes.

By 1904 torpedo range and effectiveness were growing due to two related developments. The gyro could keep a torpedo on course beyond a few hundred yards. The heater added the energy of internal combustion to the compressed air which had previously powered torpedoes. The first RN heater torpedoes were ordered in 1907. Later the ‘wet heater’ further extended range by introducing steam into the compressed air fed into the torpedo’s engine.

A battle fleet (or squadron) in close order was an enormous target which could be hit at long range, assuming the torpedo got that far. In 1904 British battleships typically steamed 2 cables (400 yds) apart bow to bow. Battleships averaging 400ft in length would occupy a third of the length of the battle line. Attacks on such mass targets were called ‘browning’ shots, by analogy to firing at groups of troops (‘into the brown’) rather than individuals. In this case ‘browning’ shots would have a one in three chance of hitting.²⁵ ‘Browning’ shots made long-range torpedo fire worthwhile. Torpedo attack from ahead would be particularly effective, since the battleships would run towards the torpedo and increase its effective range (the total run thus available was called the ‘virtual range’). In 1912 First Sea Lord Admiral Prince Louis Battenberg told his First Lord (Winston Churchill) that massed torpedo fire by the German battle line would likely cost the British as many as 35 per cent of their own battle line, based on the percentage of the total length of the line filled by ships

Heaters turned torpedoes into long-range ‘browning-shot’ weapons with range similar to those of heavy guns, hence attractive as capital-ship weapons. Range depended on the length of the torpedo, since that determined the volume of the air flask and also of the fuel tank. That in turn affected the design of a ship, because torpedo tubes were typically at right angles to the keel and space had to be found both to stow the torpedoes and to load them into the tubes. The experimental torpedo (17ft 10½in long) offered a range of 7500 yds at 30 knots, but if it were lengthened to 23ft it would reach 12,000 yds.²⁶ On 7 June 1909 First Sea Lord approved a 10,800 yds (at 30 knots) setting for the new long 21in torpedo, to be carried on board battleships as well as destroyers.

UNDERWATER PROTECTION. BATTLESHIPS.

“DREADNOUGHT.”

“STVINCENT” CLASS.

“ORION” CLASS.

“KING GEORGE V.”

“IRON DUKE.”

“QUEEN ELIZABETH.”

The shift to a uniform main battery was motivated largely by the threat of torpedoes fired by enemy battleships; the object was to make it possible for British battleships to fight outside their torpedo range. That did not solve the problem of torpedoes fired by destroyers or seagoing torpedo boats, so British dreadnoughts were designed with the first underwater protection in British capital ships. This chart compares underwater protection for classes of battleships up through the Queen Elizabeths. In earlier ships it was assumed that coal would absorb some of the effect of an underwater hit, but when oil fuel was introduced it was feared that a hit might ignite it (only later did it become clear that oil fuel could help absorb the explosion).

Torpedoes were an important but largely invisible part of dreadnought armament. After Jutland, when British shells failed to prevent the German fleet from escaping, Admiral Jellicoe, who had long advocated longer-range torpedoes, saw his battleships’ torpedoes as a more important part of their armament. HMS Collingwood shows the muzzle of her stern torpedo tube in this pre-launch photograph.

DNO (Captain Reginald Bacon) pointed out that since torpedo range now matched gun range, battleships could profitably fire their torpedoes during a gun action. Although it was impractical to add more tubes, Bacon wanted more torpedoes per tube and also a heavier warhead consistent with the new range capability. Unfortunately neither that year’s battlecruiser (Indefatigable) nor its battleship (Neptune) could be rearranged for 23ft torpedoes. An additional factor was that destroyers or other torpedo craft could fire such weapons at ranges beyond those of anti-torpedo batteries. DNC proposed that the next year’s battleships be fitted for 23ft 21in torpedoes, with twelve for broadside tubes and six for stern tubes, all side-loading (as there would not be enough athwartships space to load through a breech). These weapons were first adopted in the 1909–10 programme ships: the Colossus and Orion class battleships and the Lion class battlecruisers. They had fewer submerged tubes than their predecessors (two rather than five in a battlecruiser, three in a battleship, in each case including a stern tube), partly because tubes could be reloaded faster.

Stern tubes were eliminated because of the advent of gyro angling, which was about to be introduced in 1909. Now it would be possible to fire torpedoes at 10°, 20°, 30° or 40° before or abaft the beam, rather than only dead abeam. Assistant DNO for Torpedoes (ADT) recommended that stern tubes be removed from ships with four submerged tubes. Torpedoes intended for stern tubes had required side lugs, hence could not be fired from any other tubes.

ADT wanted more tubes because limited space in a submerged torpedo room made it nearly impossible to provide more than two or three quick reloads. After that no more could be fired for some time, yet the opportunity to fire effectively would not last long. This issue first came up with the 1910–11 ships, Queen Mary and the King George V class. All of these ships had limited internal space. Queen Mary would have to be lengthened by 10ft and displacement increased by 400 tons; in a King George V the extra tubes would cost 5ft and 250 tons. Controller (Rear Admiral Jellicoe) rejected the idea but was willing to reconsider it for the next year’s ships. Meanwhile tactical exercises were examined to see whether increased torpedo fire would be useful and experiments with gyro angling pursued. By September 1910 both the experiments and the exercises showed that two more broadside tubes were worthwhile. Exponents of more tubes also pointed to modern German battleships, which typically had four broadside tubes and a stern tube. DNO supported ADT’s argument and on 13 October Jellicoe agreed (but ADT’s request that slots be cut in side armour for torpedo directors was rejected, ships being given secondary conning towers with directors in armoured hoods instead). The first ships involved were the 1911–12 ships (Tiger and the Iron Duke class battleships). This battery was repeated in the Queen Elizabeth and Royal Sovereign class battleships.

In 1912 Home Fleet C-in-C Admiral Sir George Callaghan considered the long-range 21in torpedo so valuable that he wanted all dreadnoughts prior to HMS Hercules rearmed with 21in broadside tubes (with four such tubes in Dreadnought herself and in the Invincible class). That was impractical. By this time British gunnery was clearly effective at about 8000 yds and HMS Colossus had carried out a trial shoot (apparently against a fixed target) at 14,000 to 15,000 yds. Callaghan did not want torpedoes which could not reach an enemy battle line 10,000 yds away. Any great improvement in speed should be accompanied by greater range, the torpedo running time remaining constant at 10–11 minutes. Callaghan therefore wanted 10,000 yds at a speed of at least 22 knots. In his view anything slower would miss. In April 1912 there was interest in adjusting 18in Royal Gun Factory (RGF) heater torpedoes fired by battleships to run 10,000 or 12,000 yds at 22 knots instead of the current 6000 yds at 29 knots – to what was later called an ER setting. A July 1912 War College study concluded that long-range torpedoes fired from before the enemy’s beam could always hit from longer ranges than faster shorter-range torpedoes. Commander Second Battle Squadron (Admiral Jellicoe) seems to have been unusual in rejecting such slow torpedoes; in 1912 he considered 30 knots/10,000 yds and 44 knots/4500 yds the ideal.

The British were well aware that torpedoes produced tell-tale wakes: ships would evade if they were seen in time. The interaction of torpedoes and guns during a day action could be devastating. To keep hitting with their guns, ships needed to maintain a steady course and speed. If they saw massed ‘browning’ torpedo shots coming, they could either evade and stop hitting or they could accept underwater hits. The British made successful efforts to make torpedo wakes less visible, as attested to by Germans at Jutland. That the Germans did not (or failed when they tried) is evident in Admiral Jellicoe’s successful evasion of massed German torpedo fire at Jutland. Jellicoe clearly feared underwater damage, so he turned away.

Beginning in 1915, Grand Fleet C-in-C (Jellicoe) pressed for greater and greater torpedo ranges, which were typically called ER (extended or extreme range); he was willing to accept the low speed which had seemed unattractive in 1912. Late in 1915 trials were conducted with Mk II**** torpedoes which, it was hoped, would reach 18,000 yds at 19 to 20 knots. Each capital ship and each light cruiser with submerged tubes was to have had two torpedoes capable of reaching about 17,000 yds at 18 knots, but it is not clear how many such ER3 torpedoes had been provided by the time of Jutland. After Jutland, Jellicoe experimented with tactics emphasising the use of 15,000 yd torpedoes – torpedoes with gun range, as it was now understood. The 21in Mk IV* torpedo had settings of 15,000 yds at 25 knots and 18,000 yds at 21 knots, for submerged torpedo tubes. ER3 conversions were completed during 1917 and the longer-range Mk IV supplied, completing conversion of the fleet to longer-range torpedoes. As the fleet received longer-range torpedoes in 1917–18, ships were fitted with improved controls, supported by longer-base torpedo-control rangefinders.

UNDERWATER PROTECTION. BATTLECRUISERS.

“INVINCIBLE” CLASS

“INDEFATIGABLE”

“LION AND PRINCESS ROYAL”.

“QUEEN MARY”

“TIGER”.

Underwater protection of pre-1914 British battlecruisers.

Despite the pre-war decision to put four tubes in each capital ship, those built during the war reverted to two submerged tubes. By the beginning of 1916, Jellicoe wanted more tubes. Due to their speed, battlecruisers were most likely to gain a position of torpedo advantage. This was well before Jutland made Jellicoe wonder whether he might not have to rely on such shots until his armour-piercing shells were replaced. ADT proposed at least two and at most four fixed tubes per side arranged in pairs. DNO and Chief of Staff (Admiral Oliver) backed ADT. These had to be above-water tubes. There was no more internal space in the ships involved and trials were showing that submerged tubes might not be usable at high speed.²⁷ To DNC, inherent limitations on the height from which torpedoes could be dropped into the water suggested that any new tubes should be on the main deck, which meant that in the new battlecruiser Hood armour had to be cut away to accommodate them (ADT thought they could be outside the main belt at the ends of the ship). In any case, above-water tubes introduced an element of vulnerability. Controller asked whether it was worth risking a £3 million ship ‘for the sake of problematical hits at very long range’. First Sea Lord was told that HE shells hitting a torpedo would destroy it and that fragments would detonate any unprotected warhead within 11 yds.

Hood was given eight above-water tubes with 3in armour mantlets around their warheads. In action this protection would be reduced dramatically, as armour doors would probably be kept open to allow quick shots. The tubes were just over the stringer plates on the upper deck which formed part of the ship’s hull girder. By the autumn of 1918, DNC was pointing out that if the torpedoes did explode, that would probably break the ship in half.²⁸ This point was remembered when HMS Hood was sunk.

In July 1919 removal of four tubes was approved, the rest to be retained for experiments, but not as a war fitting due to the risk In 1923, however, approval was sought not only to make the tubes permanent, but also to add four more on each side. At this point the British were embroiled with the Americans in a dispute about whether increasing turret elevation was legal under the new Washington Treaty and it was decided to defer installation of further tubes until that had been resolved (adding tubes might have come under the same prohibition as changing the characteristics of the gun mountings).²⁹

In 1927 the situation changed again, the Americans having announced that they planned to increase the elevation of the 14in guns in the Nevadas to 30°. In November 1927 Director of Tactical Division strongly supported adding above-water tubes to battlecruisers on much the grounds Jellicoe had cited in 1916 (Repulse already had eight tubes). DNC reported that replacing the four removed tubes and adding protection would cost 110 tons (which was no problem) and would require extra personnel and thus would crowd the ship’s mess decks. The Board decided not to add the tubes so as not to ‘give the USA further reason for abusing us’. However, the four existing tubes were to be considered a war fitting and the box protection originally planned was restored during her large 1929 refit.

After Jutland it was decided to fit all the new battlecruisers, including the ‘large light cruisers’ described below, with above-water torpedo tubes.³⁰ The two battlecruisers were each to be given two sets of three tubes on each side, a total of twelve. The tubes had to be fixed, because allowing them revolve would have entailed too much disruption. DNC suggested dispensing with the submerged tubes. In September 1917 installation (on the Renowns) was approved, to be undertaken whenever opportunity offered. After the war both ships were given eight above-water tubes during their big up-armourings, the submerged tubes being removed when Renown was rebuilt (all above-water tubes being removed) and Repulse given a large refit in 1933–6.

The two ‘large light cruisers’ were also assigned above-water tubes, which were ordered in 1916 for delivery in August and September 1917. Initial proposals called for two single fixed tubes on each side, later reduced to a single tube. In April 1917 CO of Glorious asked for the battery already approved for light cruisers, two triples on each side. In the light cruisers it was justified on the grounds that they might find themselves in an advantageous attack position during a fleet engagement. The much faster ‘large light cruisers’ could do even better. The CO of Furious made a similar proposal and CO of the battlecruiser force (Rear Admiral Pakenham) agreed. Triple tubes would replace the two singles already approved. DTM argued that triple tubes would make for a crowded and vulnerable arrangement. DNC suggested that the tubes be worked into the ship’s side, hence both free of gun blast and widely separated. In June 1917 DTM suggested installing the tubes already on order abreast ‘Y’ barbette and new tubes when delivered fitted in the approved covered space, giving each ship a total of four above-water tubes. As for triple tubes, DNC pointed out that in Glorious and Courageous the after barbette was lower and the gun shorter than in Furious, so that tubes placed outside the sweep of the gun shield (turret) were subject to much greater blast. Meanwhile two triple tubes on each side (plus two single above-water tubes) were approved for Furious largely because of her special role as a carrier and her limited gun armament (later they were given up because they crowded her topsides too badly).

The Vice Admiral commanding the Grand Fleet light cruisers from Courageous wanted torpedo tubes, but he also knew how much work would be involved.³¹ C-in-C (Beatty) was ‘extremely averse to losing the services of the Glorious until the moment is propitious in view of the Light Cruiser situation and the strength of the enemy in this area. . . the end of the year would be suitable’. Material might not be available before then. The project survived because torpedo tubes were considered so important on board a ship leading the light cruisers.

The simplest scheme, to fit triple tubes each side of the after turret, was objectionable only due to the blast of ‘Y’ turret. In November 1917 a single tube was ordered fitted to the upper deck each side abreast of ‘Y’ turret of HMS Glorious for blast trials, which apparently proved successful.³² Plans called for four sets of fixed triple tubes on the upper deck aft and another two on each side in the Marine mess or in other mess places. The twelve fixed tubes were installed on board Glorious but not Courageous, in twins before and abaft ‘Y’ barbette, with another two tubes side by side at the foot of the mainmast, let into the ship’s side. Courageous but not Glorious was fitted with extensive mine rails on her quarterdeck (which she apparently never used). Presumably this installation made torpedo-tube installation less attractive.

In 1918 the British reviewed overall torpedo policy. They decided that 25 knots was too slow for torpedoes fired at targets which might be making 30 knots. For the future, minimum torpedo speed should be 29 knots – with a range of 18,000 yds. A new 21in Mk V was conceived specifically as a browning-shot weapon to be used from above-water tubes, with a range of 15,000 yds at 29 knots. It was intended for capital ships with above-water tubes (Hood, Furious, Glorious class and Renown class), for the carrier Eagle, for the Raleigh class cruisers, to ‘D’ and ‘E’ class cruisers and for flotilla leaders and ‘W’ class destroyers. The Mk VI was a new torpedo intended to provide the desired 18,000 yds at 29 knots. To do that, it had to be 4ft longer than the Mk IV, hence could not fit existing tubes. Whether destroyers should have the much longer tubes needed for very long range torpedoes became a major post-war design issue. Two were tested in 1919 at the Loch Long range and also from a special tube on board HMS Acasta. Mk VI failed its trials and was abandoned. However, there was still interest in exploring the performance of a very long torpedo, so a Mk IV was lengthened.

The initial approach was to lengthen torpedoes to increase air-flask capacity, but the torpedo designers recognised that a fatter torpedo would be more efficient. In 1918 approval was given to produce three experimental torpedoes of the same length (27ft 3in) but of about 26in diameter. The torpedo would have three settings: long range (20,000 yds at 30 knots), medium speed and high speed. The charge would be increased to 750lb. The 1919 Vernon Annual Report listed characteristics for alternative 25in and 26in designs with length (weight) of 324in (5717lb) and 336in (6251.6lb). In 1920 a Mk IV* was covered in a wooden shell to simulate a 26in torpedo.

A 24.5in calibre was chosen; estimated weight was 5340lb and length 26ft 4½in. Proposed innovations included a turbine engine and a tubular air vessel (air and oil in tandem bottles, with water in the space around them). This torpedo was adopted for the projected post-war capital ships; it armed the two Nelsons. The quest for range continued with the adoption of oxygen-enriched air (which the British called ‘enriched air’). Nominal range of the Nelson class torpedoes was 20,000 yds at 30 knots (15,000 yds at 35 knots). Plants to produce ‘enriched air’ were installed on board the Nelsons and the initial ‘County’ class cruisers. In deck installations such torpedoes caused some problems, particularly during lightning storms, but there were no problems on board the Nelsons. These weapons were not retro-fitted to any earlier ships.³³

In 1921 First Sea Lord (Beatty) and C-in-C Atlantic Fleet pointed out that torpedoes offered the battle fleet a massive unseen means of attack. Their threat might force the enemy’s tactical choices. By constantly changing course to avoid torpedoes an enemy would accept a gunnery disadvantage (most fire-control systems demanded that the firing ship maintain a steady course). On the other hand, the rear of the battle fleet would seldom be able to use its torpedoes, the enemy battle fleet still had to contend with the mass of torpedoes aboard British light forces and eliminating battleship torpedoes would save considerable weight and cost. With two fleets running on parallel courses, the existing 16,000 yd 21in torpedo (running time 15 minutes) could not be fired outside 14,000 yds. The 24.5in torpedo in the Nelsons offered greater range (20,000 yds) but also greater running time (5 minutes). Tactical experiments conducted with the Blue side at a torpedo advantage led C-in-C Mediterranean to comment in 1927 that ‘the extent of the Battle Fleet torpedo menace to the Red side can be overestimated’. At this time policy was to avoid night fleet action and opportunities for a surprise encounter declined as screening efficiency improved. British tactical policy was to close the range to achieve decisive results. The fleet might have to go into enemy torpedo water. It would gain an advantage if the enemy fleet were known not to have any torpedoes. If the enemy knew the British had no torpedoes he might be more willing to fight at the shorter ranges the British sought. However, capital ship torpedoes retained some value and obviously more for the inferior fleet. If the Washington agreement were abrogated, the British might find themselves in the inferior position. Tubes were retained.

As bulged and otherwise modernised in the 1920s, battleships retained their four underwater tubes. However, in December 1929 Controller (Admiral Backhouse) proposed that the after torpedo tubes be removed in order to improve watertight subdivision and survivability.³⁴ Backhouse considered the Royal Navy behind others in watertight subdivision. Pre-war ships had inherently poor protection against underwater attack; every opportunity should be taken to improve it. Warspite had just suffered flooding through a torpedo tube. Not only the large torpedo flat but also a large hold compartment below might flood. The impetus for the change seems to have been the US Navy’s decision to remove submerged tubes from its ships upon reconstruction (ACNS’ rebuttal was that ‘they have even less experience of modern battleship action than we have’). DTM agreed that any substantial improvement in underwater protection was more valuable than half their torpedo batteries. The tubes were ordered removed as ships came in for large repairs. That applied to Valiant, which was currently in hand and then to Barham when she came in hand following Valiant. Queen Elizabeth was to be modified during her current large repair. Controller was asked to consider a similar modification to the Royal Sovereign class. First Sea Lord asked that the rate of torpedo fire be increased: any new battleship would be unlikely to have more than two torpedo tubes.

That left ships with two tubes in a forward torpedo room. The perceived value of torpedoes increased in the 1930s as the Royal Navy learned to fight a major fleet action at night. However, so did the cost of the space surrendered for that purpose. When twin 4in high-angle guns replaced the earlier single mountings in the late 1930s, the necessary magazines were provided out of the surviving torpedo rooms.

Early in 1934 removal of all submerged tubes in the older battleships and Renown was proposed, above-water tubes being installed. C-in-C Home Fleet wanted only Renown to retain tubes, in above-water form. C-in-C wanted all the ships to have above-water tubes. At this time plans for DTM’s proposed 22.5in torpedo were dropped. Plans for above-water tubes in capital ships were generally rejected on space and weight grounds.³⁵

Should the new battleship then being planned carry torpedoes? At an October 1934 Sea Lords conference Controller argued if the gun were the primary means of attack, torpedoes could rarely be used. The 250 tons involved could better be spent on anti-aircraft armament or main-battery ammunition (thirty rounds per gun) or both. Eliminating above-water tubes would simplify training, relieve congestion on the bridges (no torpedo controls) and save personnel, making a better fighting ship. ACNS pointed to the new night action capability: four 21in tubes would add only 75 tons. First Sea Lord agreed: now that the fleet had been highly trained (and equipped) for night action, it should be and would be embraced. Even in a day action an enemy might find it much more difficult to counter torpedo salvoes fired by battleships than by destroyers. The weapons would be fired intermittently, unseen, so evasive action would be impossible. Exercises sometimes showed as much. In a night encounter in the Mediterranean in June 1932, HMS Ramillies had hit HMS Revenge three times. C-in-C Mediterranean wrote that in the large-scale strategic exercise ZH conducted in March 1934 by the Home and Mediterranean Fleets, ‘the firing of torpedoes by the battleships of both sides during the final close-range encounter might have had very important results’. According to C-in-C Home Fleet, a 18 October 1936 torpedo exercise by Nelson in low visibility demonstrated the value of torpedo armament under such conditions. Similarly C-in-C Mediterranean considered that a 15 October 1937 firing by Barham (also in low visibility) ‘indicate[s] the value of the torpedo armament to a capital ship in short range encounters’.

Although torpedoes were removed from all the rebuilt ships and also from the plans for a new battleship, when she was rebuilt HMS Royal Oak received four above-water tubes. Similar above-water tubes were approved for Revenge and Resolution at their next large refit, but they were not installed.³⁶ The new tubes were made and placed in storage, but when the ships came in for refit no preparations had been made to install them and installation would considerably delay completion. ACNS wanted the tubes installed in Revenge, particularly since it was now unlikely that the Royal Sovereign class would be scrapped on completion of the King George V class. Controller vetoed the idea (for Resolution) on the grounds of the extensive work involved, including gutting one complete mess deck. He was prepared to reconsider Revenge, but doubted that he would approve her. The dockyards were just too congested and the torpedo tubes too marginal.

During the action with Bismarck, Rodney fired her torpedoes, albeit apparently without hitting. With this experience in mind, C-in-C Home Fleet wanted the tubes retained. His successor did not. Meanwhile the British had been much impressed by the performance of Japanese torpedoes in the South Pacific, to the point where ACNS(W [Weapons]) wrote on 27 September 1943 that he agreed with DTSD that the torpedo was ‘the most effective weapon we have’. However, it was a small-ship weapon. When the status of capital-ship torpedoes was reviewed in 1943, all concerned agreed that the enriched air plant should be removed from Rodney and C-in-C Mediterranean saw no point in retaining the torpedoes without the plant, given their much-reduced performance.³⁷ DTM wanted the tubes retained in case he was able to improve torpedo performance. DNC wanted to remove the tubes to improve sub-division, but he would not pursue that if the torpedo battery could be made more effective.

To Controller, ‘this is one of those problems which gets different answers from sea and from the Sea Lords periodically. It is doubtful if we ever have a “line of battle” again. Should this happen, a proportion of battleships should have torpedoes. This was Lord Chatfield’s view. Under conditions of single ship actions or night action by small groups, torpedo armament of medium range may well prove invaluable. The torpedo, when it hits, is still our best weapon.’ The Sea Lords agreed. As late as 1945 DTM seriously proposed installing torpedo tubes on board the King George V class in the space vacated by their catapults and torpedoes were discussed in connection with the abortive 1945 battleship. Overall, the Royal Navy seems to have retained an interest in capital ship torpedoes far longer than any other.

British interest in long-range torpedoes led to an assumption, particularly before and during the First World War, that their enemies had similar views. By 1912 the British thought that others had caught up with them in torpedo range, so that in his instructions for tactical exercises that year Admiral Jellicoe wrote that the 10,000-yd 30-knot torpedo was a current reality. That presented a major problem. British gunnery had been developed to keep battleships out of enemy battleships’ torpedo range. However, 10,000 yds was average North Sea visibility range and by 1912 the Royal Navy was finding it difficult to achieve high hitting rates at even that range. In fact the Royal Navy had more, and more sophisticated, torpedoes than the Germans; even though the Germans had more torpedo tubes, they were less interested in using their torpedoes in a major fleet action. On the other hand, it was difficult for the British to use their own torpedoes during such an action because the same officers assigned to control torpedoes were often occupied controlling gunfire. British capital ships did fire torpedoes at Jutland, but the range was slightly too great for them to hit (the Germans saw British torpedoes floating to the surface at the end of their runs).

Before 1910 the British assumed that only capital ships would be firing torpedoes during a day action, perhaps because they operated their own destroyers separately from their battleships. They dismissed reports that German destroyers (torpedo boats) were working with their fleet on the grounds that such operation would be suicidal. That year they finally accepted the reports and conducted their own tactical trials. Even if the destroyers made no hits, ships evading their torpedoes would find their fire-control solutions ruined. The immediate conclusion was that 4in anti-torpedo batteries on battleships should be mounted in ships’ superstructures, preferably behind armour, where they could fire even when a ship’s main battery was in action (4in guns atop turrets could survive blast, but probably would not be effective during a main battery action). The advent of long-range torpedoes in the German navy opened a new possibility, that destroyers could fire ‘browning’ shots from a safe range. They had to be engaged at even greater ranges. Hence the protected 6in secondary guns in the 1911–12 ships Tiger and the Iron Duke class.

Underwater Protection³⁸

The Royal Navy began experimenting to determine the effect of underwater explosions as soon as self-propelled torpedoes appeared. Early experiments were conducted on HMS Resistance (1866–7), Belleisle (1903) and the Ridsdale Tank (1905–6). On the basis of these experiments and of reported foreign practice, HMS Dreadnought (1906) introduced a torpedo bulkhead: a thick bulkhead on the sides of the magazines specifically to protect them against mine and torpedo explosions. Other navies had already adopted similar measures. The British seem to have attributed the survival of the Russian Tsarevitch after a torpedo hit to her torpedo bulkhead, although in fact the torpedo hit an unprotected part of the ship. Ships built after Dreadnought had full torpedo bulkheads, but they were reduced to local protection in Colossus and Hercules. The full-length torpedo bulkhead was not revived until the Queen Elizabeth class. In these latter ships torpedo protection received special attention and improved structural arrangements were worked out.

All of these ships also had torpedo nets, which were deployed from booms folded up along the hull. The nets were intended to protect an anchored ship. On 25 May 1915, however, HMS Triumph was torpedoed and sunk during the Dardanelles campaign, even though her nets were deployed. Nets were then abandoned, one argument being that battle damage might put them in the water, where they could foul a ship’s propellers.³⁹

The full bulkhead consumed considerable weight and it was expensive. Queen Elizabeth had an important advantage: because she burned oil rather than coal, her torpedo bulkheads did not have to be pierced by coal bunker doors. DNC proposed full-scale experiments to test the ship’s protection. First Sea Lord approved the test programme on 13 February 1913. The old battleship Hood was modified to represent the structure outboard of the machinery spaces of a Queen Elizabeth. She was ready in November 1913. Two alternative forms of protection, both involving 80lb (2in) bulkheads, were tried. One, over the engine room, had the bulkhead 7ft outboard of a light bulkhead representing the outside of the machinery spaces. The other, over the boiler room, had the heavy bulkhead inboard and the light bulkhead outboard. In each case the two bulkheads were about 120ft long. In addition to the bulkheads, some compartments outboard of the bulkhead could be filled with oil or left empty. Tests employed 280lb guncotton charges against the ship’s side, 12ft below the waterline.

The first shot (9 February 1914) tested the thin bulkhead outboard of the thick one. It was blown back against the thick bulkhead, which bulged badly. The outer skin of the ship disintegrated into fragments, the largest about the size of a man’s head. If the compartments inboard and outboard of the torpedo bulkhead were left empty, they perforated the thin bulkhead. When they were filled, the liquid layers protected the bulkhead from the fragments. The inner thin bulkhead successfully resisted the pressure and there was no flooding that a ship’s pumps could not have handled. In a second shot (7 May) the 80lb bulkhead was immediately next to the boiler room, the wing (double-bottom) and outer compartments being filled and the inner compartment next to the boiler room empty. This time the hull was opened over a smaller area. However, the tamping effect of the water in the wing and outer compartment forced the middle bulkhead inwards and broke up the armour shelf at the top of the wing compartment and the hull plating beyond the bilge keel. The light middle bulkhead was driven in towards the boiler room; it tore away from the deck above. The heavy bulkhead resisted the pressure despite bulging inwards. The boiler room sustained only minor leakage.

These two shots seemed to show that the thick bulkhead should be in the outer position, furthest from the ship’s centreline, to give the innermost bulkhead the best chance of resisting the explosion. It should be strong enough to protect the engine or boiler room from being flooded. The inner (lightweight) bulkhead should be so arranged that any deflection of the heavy bulkhead would not affect it. The question of which, if any, spaces should be filled with oil, water or some solid had not been answered.

A September 1914 conference reviewed the two test shots and compared conclusions to those reached in the three earlier underwater tests and in the 1913 tests of HMS Terpsichore. It concluded that a series of thin bulkheads would be nearly useless, but that a protective plate (bulkhead) behind a series of filled and empty spaces was best. The bulkheads should be spaced so that the watertight bulkhead inboard of the protective bulkhead would not be affected by the latter’s distortion. The compartment next to the explosion should be empty, to avoid a very destructive tamping or hydraulic effect. The filled compartment (layer) should be next to the protective (torpedo) bulkhead, to protect it from fragment damage. In effect the conference affirmed the design already embodied in the Queen Elizabeth class and a similar system was installed in the Royal Sovereigns – presumably once they had been redesigned as all-oil ships. These conclusions were not far from those the US Navy was then reaching to develop its ‘sandwich’ torpedo protection.⁴⁰

The experiments implied that existing ships could gain effective underwater protection in the form of an external torpedo protection system: a ‘bulge’ or ‘blister’. It was an external pair of spaces which could be built onto a ship’s hull.⁴¹ The outer space was watertight. The inner was open at the bottom, so that it could fill with water. Inboard of it was the ship’s skin, with a wing compartment (extension of double bottom) at the top. Inboard of that was a coal bunker, with the boiler room inboard of that. The first ships to be bulged were four old Edgar class cruisers, to be modified for shore bombardment. The first British-built monitors were similarly bulged. Work began well before the British lost pre-dreadnought battleships to mines at Gallipoli, but after the mining and loss of the battleship Audacious.⁴² Bulges having proven effective, in 1917 DNC considered installing them on existing ships. The pre-dreadnought Commonwealth was given a bulge similar to that in the Edgars and the coast defence ships Glatton and Gorgon were completed with similar bulges. Two of the Royal Sovereigns were given a ‘girdling’ which, with their existing structure and oil compartments inside the ship, was considered about equivalent to that of an Edgar.⁴³

The Renowns and the Courageous class ‘large light cruisers’ were designed while the Edgars were being bulged. Their hulls were somewhat bulged out below the waterline to keep a torpedo explosion further from their vitals.⁴⁴ This hull form also reduced draught, which DNC saw as an additional protection (his Minute did not refer to the minimum-draught requirement imposed by Admiral Fisher for his Baltic project). Furious was designed slightly later with a true bulge and a very different structure. Her sloping side above water was carried all the way down to the bottom, the bulge being built outside as a separate compartment. With this outer bulge, the compartments just inside the ship offered total protection which DNC considered equal to that of a bulged Edgar. The same type of protection was incorporated in the Hawkins class cruisers and in the prototype carrier Hermes.

Given the experience of the Dardanelles, in August 1915 Controller argued that the torpedo menace would continue to be more serious than that of the gun until ship designs incorporated better anti-torpedo protection.⁴⁵ Any new capital ship should have minimum draught consistent with being a practicable seaboat – she must be able to stand the hammering she would receive in heavy weather. He guessed that the minimum would be 20–21ft. Thus future ships would have to be much longer and beamier. Their sides should be bulged below the waterline to keep the centre of any explosion outside the ship. An inner longitudinal bulkhead should be placed far enough inboard to take the pressure of the explosion, preferably curved to the corresponding radius. The ship should have as many transverse bulkheads as possible, to limit flooding and she should have adequate pumping power not dependent on the main boilers. Finally, she should have great freeboard, so that she could survive the considerable list due to an underwater hit on one side. DNC remarked that most of these features were already embodied in the new Large Cruisers (Courageous class and Furious), thanks to Admiral Fisher’s insistence on shallow draught for the Baltic.

Full-scale experiments were expensive, so in 1915 DNC sponsored a series of experiments to test a proposed scaling law. Given such a law, he could test designs for full-scale protective systems without duplicating them.⁴⁶ The first priority was to develop a means of protecting a fast ship such as a battlecruiser, which could not be given wide bulges. Some shock-absorber was needed. Experiments began at Portsmouth in April 1915 using charges equivalent to 400lbs of TNT. Timber baulks filling the outer part of a bulge wrecked the target. The next shock absorber to be tested was a nest of 3in steel tubes with sealed ends. It appeared that a layer of tubes so absorbed the shock of explosion that the width of the bulge might be halved. This was so encouraging that a full-scale model was built at Chatham, representing half the midship section of a warship, 80ft long and 31ft 6in wide at its bottom, its sides sloping upward and outward. It carried 6in side armour above a bulge. Built in December 1915, this ‘Chatham Float’ was used for full-scale tests up to about 1921. The shape of the float was much like that of the battlecruiser Hood (not yet designed), but with a much thinner belt.

For many years before the First World War ships carried torpedo nets intended to protect them at anchor. Here the crew of HMS Dreadnought rigs nets prior to a visit from Dominion premiers during a Dominion Conference, probably the one held in 1909. The gauzy effect on the hull is the net, normally carried rolled up against the ledge visible on the side of the ship. Once unrolled, it is spread over the heavy line visible just below the ledge, which in turn runs between the upper ends of the booms lashed diagonally to the hull. The booms could then be lowered to create a curtain around the ship. By 1914 it was not at all clear that nets would be effective in the face of net-cutters normally mounted on torpedoes and there was a real fear that if they were damaged in action they would foul a ship’s propellers. Moreover, the strategic situation left few ships anchored in exposed places. One of the exceptions was HMS Triumph, sunk at anchor in May 1915 despite her nets.

A 400lb charge exploded 15ft below the waterline made a hole about 15ft in diameter in the outer plating of the bulge. Its force was almost completely absorbed by a nest of closely-packed 9in steel tubes forming a layer between an outboard void and a bulkhead representing the outside of the ship’s vitals. The simulated ship’s structure was almost undamaged. This type of protection was incorporated in the monitors Erebus and Terror and in HMS Hood. Also in 1915, the decision was taken to incorporate this type of protection in the battleship Ramillies, then under construction. DNC was proud that careful design had limited the cost (in speed) of this bulge to a quarter-knot. Overall, bulging could allow capital ships to meet torpedo fire in much the same way that they met gunfire with their armour.

The question was whether the Royal Navy was justified in not bulging all its capital ships. On 29 August 1918 the Board referred the question to a committee headed by Admiral Jellicoe, the other members being Controller, Fourth Sea Lord and DNC, with Captain F C Dreyer as secretary. C-in-C Grand Fleet (Admiral Beatty) asked to attend when possible and Jellicoe asked that a torpedo officer (Commander M K Grant) be added as a second secretary. On 4 November 1918, the committee recommended that all new capital ships have bulges about 400ft long, sufficiently strong to resist two 21in torpedoes. It envisaged an area of damage 20 to 30ft long. As an example of what could be done, DNC had reported that under certain conditions and with torpedoes spaced 60ft apart, Hood could continue underway after being hit by eight torpedoes with 600lb charges. All battleships from the King George V class onwards and battlecruisers from the Lion class and the carrier Eagle should be bulged. In the case of the Queen Elizabeths, it should be a matter for the Board as to whether a loss of three-quarters of a knot could be accepted ‘in view of the known speed of the later German battleships’.⁴⁷ The Board had recently approved bulging the two Renown class battlecruisers and that in turn had delayed the planned ‘girdling’ of the last two Royal Sovereigns.⁴⁸

With the war over, in February 1920 DNC pointed to the high cost of bulging the existing obsolescent ships. A major consideration, which DNC and the Board did accept, was that larger floating docks would be needed to accommodate bulged ships.⁴⁹ Ultimately the decision was to bulge the remaining 15in gun battleships – two Royal Sovereigns and the Queen Elizabeths – which would be the core of the post-war fleet.

It proved impossible to repeat DNC’s favoured Hood arrangement in the post-war capital ships. Hood had incorporated sloped armour to provide sufficient protection, but the ships designed in 1920–1 and afterwards had to be protected against more powerful shells at greater ranges. For that their designer adopted more steeply sloping armour, which could not be placed outside the hull.⁵⁰ That in turn required that underwater protection be internal. In line with his criticism of US underwater protection, DNC also was concerned that the internal protection system be designed to vent the gas of any explosion outside the protected citadel. He ended up with a series of steeply-sloping bulkheads reinforced with tubing. The Chatham Float was modified to test it against a 750lb charge.

The same underwater protection was incorporated in the O3 design which became the Nelsons. It was realised that the arrangement of belt armour and the underwater protection system, adapted from the previous design, were too closely related to separate.⁵¹ DNC cited quarter-scale underwater tests which showed that decreasing the slope of the belt would jeopardise underwater protection. These models represented the planned O3 protection, a modified version of O3, the American system of vertical bulkheads in a ‘sandwich’ (as understood from wartime data) and a modified American system. All were tested against the equivalent of a 1000lb torpedo warhead. The O3 design performed best, the modified British system being inferior. To offer the same resistance as the British system, the American system had to be made about a quarter heavier. Even then DNC considered it distinctly inferior. Weight was particularly important for ships designed under the Washington Treaty displacement limit. The tests appeared to show that arrangements to vent the water jacked (and, in future, the air jacket outboard of it), which were embodied in the British but not the American systems, were necessary to limit damage to the ship proper. In the American systems the outer bottom was forced down the equivalent of 3ft in a full-scale ship. DNC pointed out that such damage might make it impossible to dock such a ship promptly for repairs.

DNC felt vindicated and the Board confirmed the O3 design.⁵² However, some changes were made. The belt was brought out to the side of the ship, to reduce any gap into which a shell might pass. Its slope was reduced from 18° to 15° slope for the same reason. The main deck was given a slight slope, as in G3 and the belt slightly reduced in height.

The resulting combination of deeply-sloping side armour and sloping underwater bulkheads was incorporated in the designs for abortive battleships drawn up during the 1920s. However, by the time the British were designing a new battleship in 1933, they had shifted to a US-style sandwich of vertical bulkheads with an outboard air space, a liquid layer and then an inboard air space. At the same time the inclined internal belt of earlier designs was dropped in favour of an external vertical belt. Although quite different in detail, this was broadly the US system of protection which DNC had considered inadequate a decade earlier. Ironically, the US Navy adopted a British-style internal inclined belt for its South Dakota class in 1936, because that was considered the only way to obtain sufficient protection (against 16in shellfire) within treaty-limited displacement.

HMS Thunderer shows the torpedo net booms, pivoted at their lower ends. The net itself, normally stowed along the deck edge, is not present.

Active protection against torpedo boats and destroyers was broadly analogous to later protection against air attack. Until 1910 the British assumed that destroyers would attack at night, so torpedo defence guns could be mounted on turret tops (as well as in superstructures). These 4in/45 guns were photographed on board HMS Invincible when she visited New York City in 1910 for a naval review, after a celebrated maximum-speed dash across the Atlantic.

The new British system was based on small-scale experiments, but adoption was also connected with efforts to protect against diving shells, a threat revealed in firing experiments against the battleship Emperor of India. It was first used in the carrier Ark Royal and then in the King George V class. Having been adopted, the new system was tested successfully against 750lb charges in a new full-scale device called Job 74.⁵³ The Royal Navy thus began the Second World War convinced that it had mastered the torpedo problem. The loss of both Ark Royal and Prince of Wales to torpedoes, in the latter case with considerably smaller charges, was therefore particularly shocking. In both cases a special committee of outside experts (First and Second Bucknill Committees) was formed to review current underwater protection. It turned out that in each case the torpedo protection system had not really been tested. Ark Royal was hit at the turn of her bilge as she turned sharply to evade torpedoes. Even though the hit defeated her side protection, she could have been saved had she been counterflooded properly (it did not help that she lost all power). Prince of Wales suffered an even more unfortunate hit, which caused widespread flooding through her outboard port shaft alley. Nothing in the ship’s side protective system would have solved the problem.

By 1944 the Admiralty Underwater Experimental Works (UNDEX) was testing models of the underwater protection for the large carriers then planned. It was also conducting small-scale tests comparing US and British practice. US ships had sloped bulkheads and the US Navy had adopted an outer liquid layer (the British called it a water-water-air or WWA system). On the basis of small-scale tests, UNDEX doubted that there was even a 10 per cent difference between the British AWA system and the WWA system and it strongly supported a shift to WWA. The inner air compartment should be made somewhat wider and fuel oil would be carried in the liquid compartments, displaced by water as it was burned. Slanting the main torpedo protection bulkheads inwards would widen the side protective system towards the ship’s bottom, increasing resistance with depth to match the greater effect of a deeper-running torpedo and also narrowing the target the ship presented to an under-bottom explosion. It also improved protection against diving shells and rockets.⁵⁴

During the First World War DNC conducted extensive scale model tests of alternative forms of underwater protection, finally building a full-scale model (the ‘Chatham Float’, shown here) for proof tests.

By the end of the war, there was a real question as to whether underwater protection was worth its considerable cost in terms of ship volume. There was no obvious limit to the explosive load torpedoes could carry, particularly if they were filled with new explosives such as Torpex. Internal volume had always been a problem. During the design of the abortive 1945 battleship, it was seriously suggested that conventional underwater protection be abandoned altogether. Carriers were a different matter, since their beam was set by flight deck dimensions, so they were able to accommodate wide side-protection systems.

As work on a new battleship began in 1944, another underwater protection question was raised. Since the Nelsons, the magazines in new battleship designs had been placed below shell rooms to protect them against diving shells. Battleships now faced influence mines and non-contact torpedoes which exploded under them. Was the previous practice still valid? The answer was needed urgently, because the design of the new turrets, the controlling factor in building a battleship, depended on it. DNC considered it unlikely that an under-bottom explosion would ignite a magazine. With the advent of guided bombs such as the German FX-1400 (which had nearly sunk HMS Warspite and had sunk the Italian Roma) the case for keeping magazines below shell rooms seemed stronger than ever. Trials with a mine filled with Amatol had shown that although some cordite might ignite, the inrush of water would quench the fire. However, some escorts seemed to have suffered magazine explosions after having been torpedoed. The Germans used torpedoes with a quarter aluminium filling for greater flash and heat. However, an aluminised explosive such as the Germans used might cause a considerably larger fire. US experience with the cruiser Savannah, which suffered a hit in a magazine by a German guided bomb, was encouraging: there was no serious powder fire or explosion. That suggested a cure other than modifying the location of the magazine.

Small-scale trials, which were continuing, were not considered sufficiently representative of the full-scale situation. In August 1944 the disabled battleship Warspite was proposed for a full-scale trial.⁵⁵ Warspite had her magazine above her shell room, so ‘B’ shell room and ‘B’ magazine would be stripped out, each rebuilt to represent the other function. The ship would be made watertight and her reserve of buoyancy increased to reduce the chance of a total loss which would destroy important evidence of what had happened. Even a total loss would answer the question of whether water would rush in quickly enough to extinguish the fire or the rate of burning (of cordite) would increase so quickly that the magazine would explode. DNO argued that such a trial would have a far-reaching effect, determining capital ship magazine arrangements for many years to come. Plans called for detonating 750–1000lbs of aluminised explosive 3–4ft under the ship’s bottom. Plans for the full-scale trial seem to have died at the end of the war; Warspite was never tested.

The Royal Navy also devised tactics to evade a torpedo salvo, particularly one fired by the enemy battle line. The C-in-C maintained situational awareness using a plot and he could signal a group turn to evade expected torpedoes. That was the basis of the turn-away at Jutland, based on Admiral Jellicoe’s plot. After the battle, there was considerable interest in different torpedo evasion tactics. One observation was that not all of the British battleships might be threatened. Although the C-in-C retained the option of ordering all the ships in the battle line to turn away (or, later, towards) the enemy to comb torpedo tracks, ships’ captains were also given the option of individually evading. To make that practicable, ships were given enclosed torpedo lookout positions, typically on the foremast (in a few cases, on either side of the bridge structure). These boxes are the visible indications of a radical change in Grand Fleet tactics. After the war the much less numerous British battle fleet adopted more widely-spaced formations, which in themselves made ‘browning’ shots by an enemy battle line much less profitable. The enclosed torpedo lookout positions were gradually eliminated.

Fuel

By the time HMS Dreadnought was built, the Royal Navy burned coal but was using oil either as a supplement (to be sprayed on the coal fires in boilers) or as a future single fuel.⁵⁶ From 1904 on, all large new ships were designed to burn some oil as well as coal. The new coastal torpedo boats (‘oily wads’) and ‘Tribal’ class destroyers were designed to burn only oil. Boilers in large ships were designed to develop full power on coal, oil being sprayed on as a means of increasing endurance of fuel and personnel and also as a means of quickly increasing and maintaining maximum power. By 1908 there was some question as to whether the supply of oil could be assured, so the Beagle class destroyers reverted to coal-burning. Their design made the limits of coal so obvious that all subsequent British destroyers burned only oil. The follow-on Acorn had a more powerful armament on 20 per cent less displacement, cost 16 per cent less and was 1.5 knots faster and unlike a coal-burner she could maintain her speed until her fuel ran out.

In Wales the Royal Navy had an excellent supply of the best steaming coal in the world. However, coal had had to be shovelled manually into the boiler face. Each boiler therefore needed an accessible face and human limitations on shovelling limited the size of the boiler. The space in front needed access to coal bunkers. Coal in distant bunkers had to be moved manually (‘trimmed’) into position closer to the furnaces. This was so significant a limitation that when the battle-cruiser Invincible made a celebrated transatlantic run (at an average of 25 knots) in 1909, holes were cut in bulkheads to provide better access. At the very least, the need for access limited a ship’s watertight integrity. No matter how good, coal left ashes and other solid refuse (clinker), which had to be cleaned out periodically, dramatically reducing a ship’s continuously available power and thus slowing her down at what might be a crucial moment. Typically a coal-burning ship could maintain full speed for a distance equivalent to 60 per cent of her fuel capacity. Coal had to be loaded into bunkers by hand, typically from bags delivered to a ship’s deck. Coaling was an all-hands evolution, laborious and filthy. A ship’s company had to move hundreds of tons of coal per hour. Although the Royal Navy (and the US Navy) expended considerable effort to develop mechanical means of coaling at sea, that was never an easy process.

Oil offered 1.3 to 1.4 times the thermal content of the best coal: a given weight of oil would drive a ship further.⁵⁷ Moreover, coal deteriorated in storage (at bases it often had to be stored under water) and its quality varied enormously from place to place. Coal also took up more space per ton, because it was not a solid mass like the oil in a tank: typically 40–43ft³ vs 38ft³ for oil. Oil bunkers could be filled to 95 per cent, whereas space had to be left at the top of coal bunkers for ventilation and for access. During the First World War many ships found that the large amount of coal in their reserve bunkers was effectively unusable. Writing in 1937, a senior British naval engineer particularly cited HMS Agincourt, whose three boiler rooms had, respectively, about 450, 800 and 2000 tons of coal around them. She was converted to burn 600 tons of oil during the first six months of the war. Had this not been done, she would have been unable to keep operating at sea after a few days at high speed, because her endurance would really have been set by the 450 tons in the first boiler room. Advocates of coal pointed to its protective value, but the coal in the upper bunkers, which might offer protection, had to be burned first, to maintain stability and to afford an adequate supply to the boilers. By the time the ship fought, this protection would probably be gone and it might be further compromised by a bunker door jammed open with coal.

An oil-fired boiler did not require an open stoking space in front of it, nor was its size limited by what one stoker could shovel into it. It also did not require very many personnel. These considerations made oil so attractive that before the First World War the Royal Navy shifted to all-oil burning for light cruisers. An incidental advantage was that fuel supply to boilers could be switched on much more rapidly than with coal-fired boilers. At Heligoland Bight in 1914 the Germans found that British destroyers and cruisers accelerated much faster than their coal-fired ships. On the other hand, it was feared that a hit on an oil bunker would start a fire; since oil would float on water, it would be difficult to extinguish. At least before 1914, the Royal Navy therefore stowed its oil fuel only in bottom tanks. Only much later did it accept the idea that oil fuel could function as a liquid load in side (underwater) protection.

Up to the Royal Sovereign class, British capital ships, including the Queen Elizabeths, were designed to burn coal.⁵⁸ Conversion (at the design stage) of the Queen Elizabeths seems not to have bought greater power output. The modification of the Royal Sovereigns seems to have been the first time advantage was taken of the superior efficiency of oil fuel, power output within a fixed volume increasing by a third. The Renowns were designed to use existing boilers modified to burn oil. Hood was designed from the outset to burn oil. That explains why she had twenty-four boilers producing about 50 per cent more power than Renown’s forty-two: the limit on boiler size imposed by coal-burning had been eliminated. The shift to smaller numbers of much larger oil-burning boilers explains why one boiler room in the rebuilt Queen Elizabeths could be eliminated altogether. Adopting oil fuel offered a dramatic reduction in engine-room personnel: Tiger needed 600 for 108,000 SHP (mixed firing), but Hood (144,000 SHP), needed only 300 for her all-oil powerplant.

For the Royal Navy an additional consideration was that oil had to be imported from overseas. That became a real problem during the U-boat offensive of 1917–18. In 1931 a petition was raised to revert to coal fuel, the argument being that mechanical stokers using pulverised coal had changed the situation.⁵⁹ In 1938 retired Captain Bernard Acworth published a book, Britain in Danger, arguing that Britain could regain naval supremacy by, among other things, reverting to coal fuel. DNC was compelled to estimate the cost of reversion.⁶⁰ It included the cost of converting all available spaces abreast the boilers for coal stowage, provision of shovelling flats, sloping chutes and special hatches, as well as supply and exhaust ventilation (coal dust could burn or explode). DNC concluded that Hood would be impossible to convert. The Nelsons, designed for oil fuel, would cost £50,000 each, as would each Royal Sovereign. Queen Elizabeths would cost £60,000 each. Worse, ships would accommodate a smaller tonnage of coal than their current oil supplies, since oil could be stowed over much larger spaces in a ship. Given the greater thermal content of oil, steaming radius would be far shorter.

Gunners relied on searchlights to see their targets at night and considerable effort was devoted to developing the right lights and also into placing them. HMS Neptune shows her double 24in searchlights, the pre-war standard. Note that this photograph was taken before rangefinders were installed in her ‘X’ and ‘Y’ turrets.

During the First World War the controlling factor in the endurance of the Grand Fleet was the endurance of its destroyers. Before the war, it had been expected that destroyers would conserve fuel, steaming out to rendezvous with the fleet when action was expected. That was never really practical. Because British destroyers burned oil, it was possible to fuel them from the capital ships; the British developed the towed-astern technique for this purpose.

Note that, unlike reciprocating engines, turbines could absorb far more than their rated power in terms of steam. Ships were often rated at both normal and overload output, the difference being the extent to which boilers were forced. Note too that until about 1910 it was impossible to measure turbine output directly, as the output of a reciprocating engine could be measured (indicated horsepower, IHP). Naval architects could certainly measure the effective horsepower (EHP) required to move a ship at a given speed and they were well aware that propellers typically translated about half their input power into EHP. Therefore for some time the Legends of British capital ships show a requirement for turbine power equivalent to a given IHP. This is often quoted as SHP, but that is misleading. For example, initially turbines were far less efficient than reciprocating engines because they turned propellers at higher speeds. Moreover, attempts to produce turbines turning at more efficient speeds translated into much larger (longer) turbines. Another problem was that a turbine could not be throttled down efficiently; it had only one (high) efficient speed. The solution to the turbine speed problem, introduced during the First World War, was to gear down a faster-running turbine. The solution to inefficient operation at lower speeds was cruising turbines.