Admiral Class Battlecruiser - Design and Description

Design and Description

In 1915 the Admiralty was considering the next generation of warship to follow the Queen Elizabeth-class battleships. The Director of Naval Construction (DNC), Sir Eustace Tennyson-d'Eyncourt, was given instructions to prepare designs for a new battleship. The design should: "take the armament, armour and engine power of Queen Elizabeth as the standard and build around them a hull which should draw as little water as was considered practicable and safe, and which should embody all the latest protection and improvements against underwater attack." The design ('A') was submitted to the Admiralty on 30 November for consideration. The DNC had been able to reduce the draught in comparison to the Queen Elizabeth by 22% by widening the ship to 104 feet (31.7 m) and lengthening it to 810 feet (246.9 m); this had the consequence of restricting the ships to use only one dock in Rosyth and two in Portsmouth. Large anti-torpedo bulges were fitted, and the secondary armament of twelve 5-inch (127 mm) guns of a new design was mounted on the forecastle deck. The resulting high freeboard gave the design a greater ratio of reserve buoyancy to displacement than in any previous British dreadnought. The design's stretched hull form also gave her an estimated speed of 26.5 knots (49.1 km/h; 30.5 mph), about 2.5 knots (4.6 km/h; 2.9 mph) faster than the Queen Elizabeth had been able to reach in service. The First Sea Lord, Admiral Sir Henry Jackson, responded on 6 December that one danger of such a large ship would be start a new arms race with the Americans that Britain could ill-afford, and that better deck protection was necessary to defeat plunging shells during long-range engagements.

The Admiralty asked for the design to be reworked ('B') with a maximum beam of 90 feet (27.4 m), but this was deemed unsatisfactory as it compromised the ship's underwater protection. A pair of revised designs was requested with the speed reduced to 22 knots (41 km/h; 25 mph) to allow the hull to be shortened to better fit in existing floating docks and the minimum possible draught. The first of the two ('C1') was to have full bulge protection and the second ('C2') to have the best bulge protection possible without exceeding Queen Elizabeth's length. 'C1' was shortened by 100 feet (30.5 m) in comparison with 'B' and 'C2' was only 610 feet (185.9 m) in length, but draught increased by 1 foot 3 inches (0.38 m). In both proposals it had been necessary to reduce the number of guns in the secondary armament and reduce the thickness of the armour. The Admiralty was not pleased with either design and asked for a revised version of 'A' of the same draught, beam, armour and armament, but shortened and with the same speed as the Queen Elizabeth. In addition the new five-inch gun was rejected in favour of the existing 5.5-inch (140 mm) gun.

At least some of the designs were passed to Admiral John Jellicoe, commander of the Grand Fleet, who pointed out that there was no need for new battleships as the British superiority in numbers over the Germans was substantial, but that was not true for battlecruisers. Germany was known to be building three new Mackensen-class battlecruisers with an estimated speed approaching 30 knots (56 km/h; 35 mph) and a reported armament of 15.2-inch (386 mm) guns. These ships would be superior to all existing British battlecruisers, and those then under construction (the two Renown-class and the three Courageous-class 'large light cruisers') were equally fast, but too thinly armoured to compete with them. He also remarked that his experience with the Queen Elizabeths had persuaded him that an intermediate speed between the battleships and the battlecruisers was of little use; he suggested that the design should be for either a 21 knots (39 km/h; 24 mph) battleship or a thirty-knot battlecruiser, preferably the latter.

The DNC prepared two new designs in response to Admiral Jellicoe's comments on 1 February 1916, each for a battlecruiser capable of thirty knots or better and armed with eight 15-inch (381 mm) guns. Design '1' displaced 39,000 long tons (39,626 t) with two less inches in belt armour and a speed of thirty knots. It used the bulky large-tube boilers traditional in British capital ships, which explains why the design was 9,000 long tons (9,144 t) larger than any of the previous battleship designs. Design '2' was essentially a repeat of the first design except that small-tube boilers were substituted. These were considerably smaller than the older type and saved 3,500 long tons (3,556 t) over Design '1' and had one less foot of draught. These savings were substantial enough to overcome the Engineer-in-Chief's objections that they required more frequent and expensive repairs. The DNC was asked to submit four more designs using small-tube boilers which were submitted on 17 February. Design '3' was Design '2' with the machinery power increased to 160,000 shaft horsepower (120,000 kW) to boost the maximum speed to 32 knots (59 km/h; 37 mph) while the other designs had either four, six or eight 18-inch (457 mm) guns. Design '3' was selected as Admiral Jellicoe has specified that the minimum number of guns should be no less than eight as fewer caused problems in accurate fire control, and two alternatives were to be provided, one with a dozen 5.5-inch guns and the other with sixteen such guns. The latter proposal was selected on 7 April and orders were placed on 19 April for three ships (Hood, Howe and Rodney). The order for the fourth ship, Anson, was placed on 13 June.

Hood was laid down on 31 May 1916, the same day as the Battle of Jutland. The loss of three British battlecruisers during that battle caused the work on all three ships to be suspended pending an investigation into possible design flaws. Admiral Jellicoe's investigation blamed the loss of the ships on faulty cordite handling procedures that allowed fires in the turrets or hoists to reach the ships' magazines. It recommended anti-flash equipment be installed in magazines and handling rooms and the improvement of deck armour over the magazines to prevent plunging shells or fragments from reaching the magazines. The DNC and the Third Sea Lord opposed the latter, believing that there was no direct evidence that the magazines had been directly penetrated.

On 5 July the DNC submitted two revised designs for the Admiral-class ships. The first was a modification of the previous design with slight increases to the deck, turret, barbette, and funnel uptake armour, one-inch protection for the 5.5-inch ammunition hatches and hoists, and the number of electrical generators increased from four to eight. These changes increased the displacement by 1,250 long tons (1,270 t) and draught by 9 inches (228.6 mm). The second design drastically improved the protection and converted the ships into fast battleships. The vertical armour was generally increased by 50% and the deck protection was slightly thickened as in the first design. These changes would have added another 4,300 long tons (4,369 t) to the original design and increased the draught by 2 feet (0.6 m), but would have cost half a knot in speed. This design would have been equal to the Queen Elizabeths, but 7 knots (13 km/h; 8.1 mph) faster and with much improved torpedo protection, although it was some 13,000 long tons (13,209 t) larger than the older ships. After the DNC submitted the above designs, he was asked to consider variations with triple fifteen-inch turrets, and these were submitted on 20 July. The Admiralty chose the fast battleship design, and Hood was laid down again on 1 September.

Later that month Hood's armour scheme was slightly revised in light of further analysis of the results of Jutland and the deck armour was modestly increased in order to ensure that a minimum thickness of nine inches of armour would have to be penetrated by shells striking at angles of descent up to 30° from the horizontal. Further alterations were made in 1917 during her construction that increased the thickness of her turret faces and roofs. These changes, plus numerous others, increased her displacement by 600 long tons (610 t), her draught by 3 inches (76.2 mm) and reduced her speed to 31 knots (57 km/h; 36 mph). The changes continued during 1918 when the thickness of her magazine crowns was increased from one inch to two; the armour for the funnel uptakes above the forecastle deck was omitted in compensation. In May 1919 her main deck armour at the side abreast the magazines was increased to three inches (76 mm), and four 5.5-inch guns and their ammunition were deleted in consequence. The next month plans were approved to increase the thickness of the main deck over the forward magazines to 5 inches (127 mm) and to 6 inches (152 mm) over the rear magazines; her four above water torpedo tubes and their protection were to be omitted and the wall of the torpedo control tower were to be reduced to a thickness of 1.5 inches (38.1 mm) to offset the armour's weight. However, the additional deck armour was never fitted and the torpedo tubes (less their protection) were retained.

Earlier in 1917, however, construction of Hood's three sisters had been suspended as the amount of labour and material they required would be better employed in the construction and repair of merchant ships and escorts needed to keep open Britain's lines of communication in the face of the U-boat blockade. Design work continued however, although Hood was too far advanced to incorporate these changes, and ultimately would have been extensive enough for the other three ships to constitute their own class. At the end of 1917 the suspended ships' design was modified to increase the thickness of the turret roofs to six inches (152 mm), and (unspecified) alterations were made to the armoured bulkheads. These cost a total of 267 long tons (271 t) in displacement. Other changes were a redesigned bridge structure and moving the funnels closer together and the exchange in position between the fifteen-inch shellrooms and magazines. This latter change would have caused the hull's form to be filled out somewhat to accommodate the handling room of the rearmost turret at the cost of a slight loss in speed and ammunition storage.

Hood was the closest to completion and her construction was continued in case the Germans managed to complete any of their new battlecruisers. Admiral Beatty continually pressed to have Hood's construction expedited and for her sisters to be restarted, but the War Cabinet refused to approve either measure as nothing could be sacrificed in the shipbuilding programme to this end. After the end of the war the three suspended ships were cancelled as they could not fully incorporate the lessons of the war.