Heavy cruiser Furutaka in 1926. Note the turrets are only mounted single gun.
|Operators:||Imperial Japanese Navy|
|Succeeded by:||Aoba class|
|In commission:||25 Feb 1925 - 11 October 1942|
|General characteristics (as per Cruisers of WWII)|
|Displacement:||7,100 tons standard;
9,540 tons full load
|Length:||185.1 m (607 ft) (overall)|
|Beam:||16.55 m (54.3 ft)|
|Draught:||5.56 m (18.2 ft)|
|Propulsion:||2-shaft Parsons geared turbines
12 Kampon boilers
|Speed:||34 1⁄2 knots (63.9 km/h; 39.7 mph)|
|Range:||6,000 nmi (11,000 km; 6,900 mi) at 14 knots (26 km/h; 16 mph)|
6 × 20 cm (7.9 in)/50-cal Mark I guns (6 × 1)
|Aircraft carried:||(initial) 1, (final) 2|
|Aviation facilities:||1 catapult|
The Furutaka class cruisers were the first heavy cruisers in the Imperial Japanese Navy, also referred to as “A class” cruisers in the I.J.N. Like the Yūbari, their design was the work of Constructor Captain Yuzuru Hiraga, assisted by Lt. Cmdr. Fujimoto Kikuo.
Designed to beat the U.S. Omaha-class cruisers and the British Hawkins class cruisers, they were as fast as the Omahas (and nearly 4 knots faster than the Hawkins class), while firing a heavier broadside, and carrying a larger torpedo battery than either one.
Their flush deck resulted in both weight savings and increased strength by allowing the hull's longitudinal members to be continuous. As with the Yūbari, the design featured side and deck armour integrated into the ship's structure, saving additional weight.
Despite the weight-saving efforts, as built the Kako was more than 900 tons heavier than its design weight. As a result, draft was increased by more than 1 metre, subsequently reducing top speed, and the height of the belt armour above the waterline. The portholes of the lowest-level crew quarters were near enough to the waterline that they needed to be closed when the ships were at sea, reducing ventilation and making the living spaces less habitable.
Due to the high freeboard of these ships, mounting the torpedo tubes on the main deck would have caused the torpedoes to enter the water at too steep of an angle. Instead, they were mounted on the middle deck in 3 pairs of fixed tubes on each side. Captain Hiraga argued against this kind of mounting, concerned that during battle either a direct hit or fires could detonate the torpedoes, causing severe damage, as indeed happened with Furutaka of this class during WWII; additionally, the cruisers Mikuma, Suzuya and Chōkai, all of which featured similar arrangements, would all be sunk or severely damaged by their own exploding torpedoes.
Japanese naval strategists since the early 1900s had planned for a defensive war in the Pacific, with the U.S. Navy as their main opponent. To take advantage of their superior long-range torpedoes, and offset the numerical superiority the U.S. Navy enjoyed, they extensively trained their crews in night torpedo tactics. In 1930, the Naval General Staff, further concerned by the limitations on the size of their navy by the London Naval Treaty won approval for an extensive modernization program of the “A class” cruisers. Planned upgrades to the ships included the latest weapons, protection, fire control systems, and communication equipment.
From 1931 to 1933 the two ships had their 4 original anti-aircraft guns replaced by improved 12 cm high-angle electro-hydraulically operated guns, with directors and range finders for them. The original airplane takeoff platform was replaced with a catapult for a reconnaissance seaplane.
They were substantially rebuilt in 1936-1937 (Kako) and 1937-1939 (Furutaka) as follows:
The 6 × 1 20 cm. main battery was replaced by 3 twin turrets housing the 8 in (203 mm)/50-cal guns. Light antiaircraft protection was augmented with 8 25 mm automatic cannons in 4 twin mounts. The 6 pairs (3 per side) of fixed torpedo tubes mounted on the middle deck were replaced with 2 quadruple mounts using the powerful Type 93 torpedo, located on the upper deck, one on each side of the catapult.
The bridge structure was completely rebuilt to accommodate the latest rangefinders and fire control equipment for the main battery, antiaircraft and torpedoes. Platforms were redesigned for aircraft spotters.
The twelve original mixed-fuel boilers were replaced by 10 large oil-fired units, along with a redesign of all the boiler rooms, and replacement of coal bunkers with fuel-oil tanks.
All of the new equipment resulted in increased electrical power requirements, so 3 more generators were added to increase power output from 315 kW to 885 kW.
The above modifications added 560 tons to the ships. To prevent the draft from increasing even more, and to improve stability, bulges were added, simultaneously enhancing antitorpedo protection. As a result, the ships' beam was increased to 16.92 m (55.5 ft).
Ships in class
|Furutaka (古鷹)||Mitsubishi Nagasaki Shipyard||5 December 1922||25 Feb 1925||31 March 1926||Sunk 11 Oct 1942, Battle of Cape Esperance|
|Kako (加古)||Kōbe-Kawasaki Shipbuilding Yard||17 November 1922||4 April 1925||20 July 1926||Sunk 10 Aug 1942 by submarine USS S-44 after Battle of Savo Island|
- Whitley, Cruisers of WWII, pp. 167
- Lacroix, Japanese Cruisers, pp. 58-59
- Lacroix, Japanese Cruisers, pp. 52-53
- Lacroix, Japanese Cruisers, pp. 15-16,52
- Lacroix, Japanese Cruisers, pp. 55-56
- Lacroix, Japanese Cruisers, pp. 58
- Lacroix, Japanese Cruisers, pp. 74
- Lacroix, Japanese Cruisers, pp. 68
- Lacroix, Japanese Cruisers, pp. 64
- Lacroix, Japanese Cruisers, pp. 114-116
- Lacroix, Japanese Cruisers, pp. 219
- Lacroix, Japanese Cruisers, pp. 75
- Lacroix, Japanese Cruisers, pp. 251-257
- Whitley, M J (1995). Cruisers of World War Two: An International Encyclopedia. London: Arms and Armour Press. ISBN 1-85409-225-1.
- Lacroix, Eric; Wells II, Linton (1997). Japanese Cruisers of the Pacific War. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-311-3. OCLC 21079856. Retrieved 23 September 2013.
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