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Oi Class, Japanese Torpedo Cruisers


Photograph of Kitakami, an Oi-class torpedo cruiser

Wikimedia Commons


Specifications:


Tonnage 5832 tons standard displacement
Dimensions 532' by 46'6" by 15'9"
162.15m by 14.17m by 4.80m
Maximum speed       31.7 knots
Complement 439
Aircraft 1 catapult
1 seaplane
Armament 4 5.5"/50 guns
4x2 25mm/60 AA guns
10x4 Long Lance torpedo tubes (no reloads)
Protection
238.3 tons
1.5" (38mm) + 1" (25mm) HT machinery belt
1.1" (28mm) HT deck (machinery)
1.8" (45mm) HT deck (magazines)
0.8" (20mm) gun shields
1.5" (38mm) + 0.5" (12mm) HT conning tower
Machinery
4-shaft Mitsubishi-Parsons-Gihon turbines (90,000 shp)
12 Kampon boilers

Bunkerage

1260 tons fuel oil

Range 4000 nautical miles (7400 km) at 14 knots
Modifications

1942-9-9: Converted to fast transports. 4x4 torpedo tubes removed to make room for two Daihatsu landing craft and two depth charge rails with 9 depth charges each.

1944: Kitakami converted to carry 8 kaiten. Light AA armament increased to 10 25mm and 4 13mm/76 AA guns. Type 13 and Type 21 radar installed.


The Ois were completed in 1920-21 as part of the Kuma class.  They were converted to torpedo cruisers before the start of the war, and carried a massive arsenal of these weapons. Their development was supported by a new doctrine for night fighting tactics in which massive numbers of Long Lance torpedoes would be launched outside battleship gun range at night to ravage the American fleet as it approached Japan. For reasons of secrecy, the conversion was not to take place until the fleet was ordered to transition to a war footing, which took place on 15 August 1941.

The conversion removed the three aft 5.5" guns (leaving only the four forward guns) and added ten sets of quadruple torpedo tubes. The tubes had no reloads, but a rail system was installed to allow torpedoes to be shifted from one side of the ship to the other. The addition of so many torpedoes cost the ships almost five knots of speed and significantly reduced their endurance.

Following the battle of Midway, the ships were converted to fast transports by removing some of their torpedo tubes. Plans to remove additional tubes to make room for additional landing craft were never carried out, but Kitakami was eventually converted into a Kaiten carrier.

Units in the Pacific:

Kitakami      

Hashirajima     

Oi

Hashirajima

Spelled Ooi or Ohi in some references.  Torpedoed 1944-7-19 in the South China Sea by Flasher.


References

Gogin (2010; accessed 2013-3-19)

Lacroix and Wells (1997)
Whitley (1995)

Worth (2001)



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