Yamato Class Battleship - Design

Design

Preliminary studies for a new class of battleships began after Japan's departure from the League of Nations and its renunciation of the Washington and London naval treaties; from 1934 to 1936, 24 initial designs were put forth. These early plans varied greatly in armament, propulsion, endurance, and armor. Main batteries fluctuated between 460 mm (18.1 in) and 406 mm (16.0 in) guns, while the secondary armaments were composed of differing numbers of 155 mm (6.1 in), 127 mm (5.0 in), and 25 mm (0.98 in) guns. Propulsion in most of the designs was a hybrid diesel-turbine combination, though one relied solely on diesel and another planned for only turbines. Endurance in the designs had, at 18 kn (21 mph; 33 km/h), a low of 6,000 nmi (11,000 km) in design A-140-J₂ to a high of 9,200 nmi (17,000 km) in designs A-140A and A-140-B₂. Armor varied between providing protection from the fire of 406 mm guns to enough protection against 460 mm guns.

After these had been reviewed, two of the original twenty-four were finalized as possibilities, A-140-F₃ and A-140-F₄. Differing primarily in their range (4,900 nmi (9,100 km) versus 7,200 nmi (13,300 km) at 16 kn (18 mph; 30 km/h)), they were used in the formation of the final preliminary study, which was finished on 20 July 1936. Tweaks to that design resulted in the definitive design of March 1937, which was put forth by Rear-Admiral Fukuda Keiji; an endurance of 7,200 nm was finally decided upon, and the hybrid diesel-turbine propulsion was abandoned in favor of just turbines. The diesels were removed from the design because of problems with the engines aboard the Taigei-class submarine tenders. Their engines, which were similar to the ones that were going to be mounted in the new battleships, required a "major repair and maintenance effort" to keep them running due to a "fundamental design defect". In addition, if the engines failed entirely, the 200 mm (7.9 in) armor that protected that area would severely hamper any attempt to replace them.

The final design called for a standard displacement of 64,000 long tons (65,000 t) and a full-load displacement of 69,988 long tons (71,111 t), making the ships of the class the largest battleships yet designed, and the largest battleships ever constructed. The design called for a main armament of nine 460-millimetre (18.1 in) naval guns, mounted in three triple-turrets—each of which weighed more than a 1930s-era destroyer. The designs were quickly approved by Japanese Naval high command, over the objections of naval aviators, who argued for the construction of aircraft carriers rather than battleships. In all, five Yamato-class battleships were planned.