Number 13-class battleship

Design and background

By 1918, the Navy had gained approval for an "eight-six" fleet, all ships under eight years old. However, having four large battleships and four battlecruisers on order put an enormous financial strain on Japan, which was spending about a third of its national budget on the Navy. Despite this, the IJN gained approval of the "eight-eight-eight" plan in 1920 after American President Woodrow Wilson announced plans in 1919 to re-initiate the 1916 plan for ten additional battleships and six battlecruisers. The Japanese response required the construction of eight additional fast battleships in the Kii and the Number 13 classes.

When designing the latter class, the Japanese followed the doctrine that they had used since the First Sino-Japanese War of 1894–1895 of compensating for quantitative inferiority with qualitative superiority. In the words of naval historian Siegfried Breyer, "had [the ships] been completed, they would have been the world's largest and most powerful battleships. Their gun calibre alone would have caused a new and more intensive naval arms race. From an engineering aspect they were more than ten years ahead of their time because they anticipated the characteristics of the fully developed, fast battleship." Naval architects William Garzke and Robert Dulin concur saying, "These ships would have completely outclassed any European battleship".

The Number 13 class was designed by Captain Yuzuru Hiraga, the naval architect responsible for most of the previous Japanese capital ships. The ships were based on his previous Kii-class battleship and Amagi-class battlecruiser designs, enlarged to take 457-millimeter (18 in) guns.

Description

The ships had a length of 259.1 meters (850 ft 1 in) between perpendiculars and 274.4 meters (900 ft 3 in) overall. They had a beam of 30.8 meters (101 ft 1 in) and a draft of 9.8 meters (32 ft 2 in). The normal displacement of the battleships was 47,500 metric tons (46,700 long tons).

The class was intended to be equipped with four Gijutsu-Hombu geared steam turbines, each of which drove one propeller shaft. The turbines were designed to produce a total of 150,000 shaft horsepower (110,000 kW), using steam provided by 22 Kampon oil-fired water-tube boilers, to reach a maximum speed of 30 knots (56 km/h; 35 mph).

The primary armament of the Number 13 class was eight 50-caliber 460-millimeter guns in four twin-gun turrets, two each superfiring fore and aft of the superstructure. No examples of this gun were ever built, but it was planned to fire a 1,550-kilogram (3,420 lb) shell at a muzzle velocity of 800 meters per second (2,600 ft/s). The secondary battery consisted of 16 single 50-caliber 14-centimetre (5.5 in) guns mounted in casemates in the superstructure. The manually operated guns had a maximum range of 19,750 meters (21,600 yd) at an elevation of +35° and fired at a rate up to 10 rounds per minute. The ships' anti-aircraft defenses consisted of either four or eight single 45-caliber 12-centimetre (4.7 in) 10th Year Type anti-aircraft guns mounted around the single funnel. Each of these guns had a maximum elevation of +75° and a maximum rate of fire of 10–11 rounds per minute. They could fire a 20.41-kilogram (45.0 lb) projectile with a muzzle velocity of 825–830 m/s (2,710–2,720 ft/s) to a maximum height of 10,000 meters (32,808 ft). The Number 13 class was also designed with eight 61-centimeter (24 in) above-water torpedo tubes, four on each broadside.

The waterline armor belt was intended have a maximum thickness of 330 millimeters (13 in) and, like the Kii class, it was angled 15° outwards at the top to increase its ability to resist penetration at short range. The deck armor would have had a total thickness of 127 millimeters (5 in).