HMS Vanguard (23) - Design and Description

Design and Description

By early 1939 it was clear that the first two Lion-class battleships could not be delivered before 1943 at the earliest and that further battleship construction would be necessary to match the German and Japanese battleships already under construction. The main constraint on the construction of any new battleships was the limited available capacity and the time required to build large-calibre guns and their gun turrets. Using four existing twin 15-inch (380 mm) mountings offered the possibility of bypassing this bottleneck and allowed the construction of a single fast battleship more quickly than building more Lion-class ships. The turrets were originally built for the battlecruisers Courageous and Glorious during World War I and were removed during the conversions of these ships to aircraft carriers in the 1920s. To save time, the Lion design was modified to accommodate the four turrets and preliminary design work began in July 1939. The square or transom stern was retained as it was estimated to improve speed at full power by .33 knots (0.61 km/h; 0.38 mph). This made Vanguard the only British battleship built with a transom stern as the Lions were never finished.

Design work was suspended on 11 September after the start of World War II, but resumed in February 1940 after the First Lord of the Admiralty, Winston Churchill, expressed an interest in the ship. The design was modified to increase protection against shell splinters on the unprotected sides of the ship's hull, the armour of the secondary armament was increased to resist 500-pound (230 kg) semi-armour-piercing bombs and the splinter belt's thickness fore and aft of the main armour belt was reduced by 0.5 inches (12.7 mm) in compensation. A small conning tower was added aft and four Unrotated Projectile mounts were added to supplement the six octuple-barrel 2-pounder anti-aircraft mounts already planned.

More pressing commitments forced the preliminary design work to be suspended again in June and, when it resumed in October, the design was modified again in light of recent war experience. Greater fuel capacity was added and the armour protection improved, but these changes deepened the design's draught so that it exceeded the 34-foot (10.4 m) limit of the Suez Canal. The thickness of the main belt was reduced by 1 inch (25 mm) to save weight, but the primary method chosen to reduce the draught was to increase the beam by 2.5 feet (0.76 m). This exceeded the width of the docks at Rosyth and Plymouth, which severely limited the number of docks that could handle the ship, but these changes were approved by the Board of Admiralty on 17 April 1941. The ship had already been ordered on 14 March under the 1940 Emergency War Programme, although the drawings were not turned over to John Brown & Company until ten days later.

Vanguard's design was revised again, while the ship was under construction in 1942, to reflect lessons learned from the loss of the King George V-class battleship Prince of Wales and operations with the other battleships. The space between the inboard and outboard propeller shafts was increased from 33.5 to 51.5 feet (10.2 to 15.7 m) to prevent a single torpedo from wrecking both shafts and watertight access trunks were added to all spaces below the deep waterline to prevent progressive flooding through open watertight doors and hatches as happened to Prince of Wales. This change and the relocation of some of the 5.25-inch (133 mm) ammunition handling rooms from the lower deck to the middle deck seriously delayed the ship's completion. The design requirement that the guns of 'A' turret be capable of firing straight ahead at 0° of elevation was sacrificed to allow her freeboard forward to be increased and her bow was reshaped to make it less prone to shipping water and throwing sea spray in head seas. The ship's fuel supply was increased from 4,400 long tons (4,500 t) to 4,850 long tons (4,930 t) to prevent the fuel shortage problems suffered by King George V and Rodney during their pursuit of the German battleship Bismarck. The Unrotated Projectile mounts were deleted from the design and the light anti-aircraft armament was increased to a total of 76 two-pounders in one quadruple and nine octuple mounts and 24 Oerlikon 20 mm cannon were also added in 12 twin mounts. Space for these was made available by removing the two floatplanes, the catapult, and their associated facilities.

A proposal was made in 1942 to convert Vanguard to an aircraft carrier and the Director of Naval Construction said that doing so along the lines of the Audacious class would present no major difficulties, but would require six months to redesign the ship. The proposal was formally rejected on 17 July.