Name Taiyō class Preceded by None Built 1938–41 | Operators Imperial Japanese Navy Succeeded by Kaiyo In service 1941–44 | |
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The Taiyō-class escort carrier (大鷹型航空母艦, Taiyō-gata Kōkū-bokan) was group of three of escort carriers used by the Imperial Japanese Navy (IJN) during World War II. Two of the ships were built as cargo liners in the late 1930s and subsequently taken over by the IJN and converted into escort carriers, while the third ship was converted while still under construction. They were used as training ships, aircraft transports and as convoy escorts during the war. All three were sunk by American submarines in 1943 and 1944.
Contents
Background and description
These ships were Nitta Maru-class cargo liners built by Mitsubishi at their Nagasaki shipyard for the shipping lines Nippon Yusen Kaisha (NKK) and Osaka Shosen Kaisha (OSK). Nitta Maru and Yawata Maru were ordered for NKK and both were completed before the beginning of the Pacific War in December 1941. Kasuga Maru had been ordered by OSK and was fitting out when she was acquired by the IJN in 1940 and towed to Sasebo Naval Arsenal on 1 May 1941 to finish her conversion into an escort carrier. She was the first ship to be completed as her sister ships were not converted until 1942.
The Nitta Maru-class ships were 17,100-gross register ton (GRT) ocean liners with a speed of 21–22 knots (39–41 km/h; 24–25 mph) and had been subsidized by the IJN for possible conversion into auxiliary carriers. As part of their conversion, their diesels were replaced by two sets of Kampon geared steam turbines, each driving one propeller shaft, using steam produced by four Kampon water-tube boilers in a failed attempt to increase their speed. The turbines were rated at a total of 25,200 shaft horsepower (18,800 kW) and gave the ships a speed of 21 knots. The uptakes for the boilers were trunked together into a downward-curving funnel on the starboard side of the hull amidships. The ships carried 2,290 tonnes (2,250 long tons) of fuel oil that gave them a range of 8,500 nautical miles (15,700 km; 9,800 mi) at a speed of 18 knots (33 km/h; 21 mph). Taiyō's crew numbered 747 officers and ratings while her sisters had 850 officers and crewmen.
The conversion of the Taiyō-class ships, as the former liners were now known, was fairly austere and they were flush-decked carriers that displaced 18,120 tonnes (17,830 long tons) at standard load and 20,321 tonnes (20,000 long tons) at normal load. The ships had an overall length of 180.2 metres (591 ft 4 in), a beam of 22.5 metres (73 ft 10 in) and a draught of 7.7–8.0 metres (25.4–26.25 ft). The flight deck was 172.0 metres (564 ft 3 in) long and 23.5 metres (77 ft) wide. The ships had a single hangar, approximately 91.4 metres (300 ft) long, served by two centreline aircraft lifts, each 12.0 by 13.0 metres (39.4 ft × 42.7 ft). Taiyō could accommodate a total of 27 aircraft, including four spares, and her sisters had a capacity of 30 aircraft.
Armament
Taiyō, as the first ship completed, had an armament of six single 45-calibre 12 cm (4.7 in) 10th Year Type anti-aircraft (AA) guns in sponsons along the sides of the hull. The guns had a maximum elevation of +75° which gave them a range of 16,600 metres (18,200 yd) and a ceiling of 10,000 metres (33,000 ft). They fired 20.41-kilogram (45.0 lb) projectiles at a rate at 10–11 rounds per minute at a muzzle velocity of 825–830 m/s (2,710–2,720 ft/s). Her light AA consisted of eight license-built 25 mm (1.0 in) Type 96 light AA guns in four twin-gun mounts, also in sponsons along the sides of the hull. They fired .25-kilogram (0.55 lb) projectiles at a muzzle velocity of 900 m/s (3,000 ft/s); at 50°, this provided a maximum range of 7,500 meters (8,202 yd), and an effective ceiling of 5,500 meters (18,000 ft). The maximum effective rate of fire was only between 110 and 120 rounds per minute due to the frequent need to change the fifteen-round magazines.
Chūyō and Un'yō were equipped with eight more modern 40-caliber 12.7 cm (5.0 in) Type 89 dual-purpose guns in four twin mounts on sponsons along the sides of the hull. They fired 23.45-kilogram (51.7 lb) projectiles at a rate between 8 and 14 rounds per minute at a muzzle velocity of 700–725 m/s (2,300–2,380 ft/s); at 45°, this provided a maximum range of 14,800 metres (16,200 yd), and a maximum ceiling of 9,400 metres (30,800 ft). They also had eight 25 mm Type 96 AA guns like Taiyō.
In early 1943, the four twin 25 mm mounts were replaced by triple mounts and varying number of additional 25 mm guns were added. Taiyō and Un'yō received a total of 24 guns in eight triple mounts while Chūyō had a total of 22 guns plus 5 license-built 13.2 mm (0.5 in) Type 93 anti-aircraft machineguns. The ships also received a Type 13 air search radar in a retractable installation on the flight deck at that time. The following year, Taiyō's 12 cm guns were replaced by four 12.7 cm Type 89 guns in twin mounts. In addition, Taiyō and Un'yō had their 25 mm guns increased to a total of 64 weapons.
Although larger, faster and having a larger aircraft carrying capacity than their western counterparts, these ships were unsuited to a traditional carrier role as they lacked arresting gear.