Kaichu Type

(Imperial War Museum photo, scanned from "Submarines of the Imperial Japanese Navy" by Polmar and Carpenter)

RO-33 showing bow anti-submarine net cutter.

These double-hull medium displacement boats were derived from the Kai-toku-chu (KT) type. They were constructed at four shipyards in two variants, K.5 (RO-33 class) and K.6 (RO-35 class), from 1934 to 1944. The later and more numerous K.6 variant was armed with the 21-inch oxygen-propelled Type 95 submarine torpedo and a 3.25-inch (80-mm) deck gun. Allied ASW measures took a heavy toll of the type. RO-50 was the only ship of the type to survive the war and was surrendered at Sasebo.

Units 20 (1 survived)
Ships RO-33, RO-34, RO-35, RO-36, RO-37, RO-38, RO-39, RO-40, RO-41, RO-42, RO-43, RO-44, RO-45, RO-46, RO-47, RO-48, RO-49, RO-50 , RO-55 and RO-56
Year(s) Completed 1934 - 1944
Displacement (K.6) 960 tons (standard), 1,115 tons (surfaced), 1,447 tons (submerged)
Dimensions 264 ft x 23 ft x 13 ft
Machinery 2 diesels: 2,900 hp

2 electric motors: 1,200 hp

Speed 19.8 knots / 8 knots
Range 5,000 nm @ 16 knots
Armament 4x533mm TT fwd + 1x80mm + 2 25mm (8 Torpedoes)
Crew (K.6) 54 officers and men