The submarines were double-hulled medium-sized submarines of the Imperial Japanese Navy during World War II. The name was derived from the .
Several variants existed. From 1934 to 1944, the K6 type (Ro-33 Class) and the K7 type (Senchū, Ro-35 Class) were built. They were equipped with a 76.2mm L/40 gun and four 53 cm torpedo tubes for ten type 95 Long Lance torpedoes.
Most of these submarines were destroyed in combat, suffering from Allied anti-submarine warfare measures, and only survived the war.
The Kaichū type submarines were divided into seven classes:
Project number S7. In 1910s, the Imperial Japanese Navy (IJN) bought a license of Schneider-Laubeuf design submarine. The IJN used the design as model and built the S Type (Schneider Type) submarine, the and . The Kaichū I is the submarine which jumboized the S Type submarines.
| Boat | Builder | Laid down | Launched | Completed | Fate |
|---|---|---|---|---|---|
| Submarine No. 19 [1] | Kure Naval Arsenal | 25-04-1917 | 25-10-1917 | 31-07-1919 as Submarine No. 19 | Renamed Ro-11 01-11-1924. Decommissioned 01-04-1932. |
| Submarine No. 20 | Kure Naval Arsenal | 25-04-1917 | 01-12-1917 | 18-09-1919 as Submarine No. 20 | Renamed Ro-12 01-11-1924. Decommissioned 01-04-1932. |
Project number S18. The Kaichū II had an increased range compared with the Kaichū I, and the turning torpedo tubes were removed.
| Boat | Builder | Laid down | Launched | Completed | Fate |
|---|---|---|---|---|---|
| Submarine No. 23 | Kure Naval Arsenal | 14-09-1918 | 26-08-1919 | 30-09-1920 as Submarine No. 23 | Renamed Ro-13 01-11-1924. Decommissioned 01-04-1932. |
| Submarine No. 22 | Kure Naval Arsenal | 14-09-1918 | 31-03-1919 | 17-02-1921 as Submarine No. 22 | Renamed Ro-14 01-11-1924. Decommissioned 01-09-1933. |
| Submarine No. 24 | Kure Naval Arsenal | 12-06-1920 | 14-10-1920 | 30-06-1921 as Submarine No. 24 | Renamed Ro-15 01-11-1924. Decommissioned 01-09-1933. |
Project number S18. Their project number was the same as in the Kaichū II type submarine, however their performance was improved.
| Boat | Builder | Laid down | Launched | Completed | Fate |
|---|---|---|---|---|---|
| Submarine No. 37 | Kure Naval Arsenal | 18-11-1920 | 22-04-1921 | 29-04-1922 as Submarine No. 37 | Renamed Ro-16 01-11-1924. Decommissioned 01-09-1933. |
| Submarine No. 34 | Kure Naval Arsenal | 24-09-1920 | 24-02-1921 | 20-10-1921 as Submarine No. 34 | Renamed Ro-17 01-11-1924. Decommissioned 01-04-1936. |
| Submarine No. 35 | Kure Naval Arsenal | 20-10-1920 | 25-03-1921 | 15-12-1921 as Submarine No. 35 | Renamed Ro-18 01-11-1924. Decommissioned 01-04-1936. |
| Submarine No. 36 | Kure Naval Arsenal | 09-09-1920 | 28-12-1920 | 15-03-1922 as Submarine No. 36 | Renamed Ro-19 01-11-1924. Decommissioned 01-04-1936. |
| Submarine No. 38 | Yokosuka Naval Arsenal | 28-07-1919 | 26-10-1920 | 01-02-1922 as Submarine No. 38 | Renamed Ro-20 01-11-1924. Decommissioned 01-04-1934. |
| Submarine No. 39 | Yokosuka Naval Arsenal | 28-07-1919 | 26-10-1920 | 01-02-1922 as Submarine No. 39 | Renamed Ro-21 01-11-1924. Decommissioned 01-04-1934. |
| Submarine No. 40 | Yokosuka Naval Arsenal | 22-01-1921 | 15-10-1921 | 10-10-1922 as Submarine No. 40 | Renamed Ro-22 01-11-1924. Decommissioned 01-04-1934. |
| Submarine No. 41 | Yokosuka Naval Arsenal | 22-01-1921 | 15-10-1921 | 28-04-1923 as Submarine No. 41 | Renamed Ro-23 01-11-1924. Decommissioned 01-04-1935. |
| Submarine No. 42 | Sasebo Naval Arsenal | 21-04-1919 | 08-12-1919 | 30-11-1920 as Submarine No. 42 | Renamed Ro-24 01-11-1924. Decommissioned 01-04-1935. |
| Submarine No. 43 | Sasebo Naval Arsenal | 19-02-1920 | 17-07-1920 | 25-10-1921 as Submarine No. 43 | Renamed Ro-25 01-11-1924. Decommissioned 01-04-1936. |
Project number S18A. Improved model from the Kaichū III type.
| Boat | Builder | Laid down | Launched | Completed | Fate |
|---|---|---|---|---|---|
| Submarine No. 45 | Sasebo Naval Arsenal | 10-03-1921 | 18-10-1921 | 25-01-1923 as Submarine No. 45 | Renamed Ro-26 01-11-1924. Decommissioned 01-04-1940. Scrapped 1948. Her anchor is displaying at Yokosuka Naval Base. |
| Submarine No. 58 | Yokosuka Naval Arsenal | 16-07-1921 | 22-07-1922 | 31-07-1924 as Submarine No. 58 | Renamed Ro-27 01-11-1924. Decommissioned 01-04-1936. Scrapped 1948. |
| Submarine No. 62 | Sasebo Naval Arsenal | 10-11-1921 | 13-04-1922 | 30-11-1923 as Submarine No. 62 | Renamed Ro-28 01-11-1924. Decommissioned 01-04-1940. Scrapped 1948. |
Project number S18B. They were built for the commerce raiding role. The IJN official designation of these boats was .
| Boat | Builder | Laid down | Launched | Completed | Fate |
|---|---|---|---|---|---|
| Submarine No. 68 | Kawasaki-Kōbe Shipyard | 02-06-1921 | 05-12-1922 | 15-09-1923 as Submarine No. 68 | Renamed Ro-29 01-11-1924. Decommissioned 01-04-1936. |
| Submarine No. 69 | Kawasaki-Kōbe Shipyard | 27-06-1921 | 18-01-1923 | 29-04-1924 as Submarine No. 69 | Renamed Ro-30 01-11-1924. Decommissioned 01-04-1942. Scrapped 1945. |
| Submarine No. 70 | Kawasaki-Kōbe Shipyard | 25-09-1921 | 15-02-1923 as Submarine No. 70 | Lost in an accident off Awaji Island 21-08-1923. Salvaged and scrapped October 1923. Her materials were used for Ro-31. | |
| Kawasaki-Kōbe Shipyard | 20-12-1924 | 25-09-1926 | 10-05-1927 | Decommissioned 25-05-1945. Scuttled off Sasebo 05-04-1946. | |
| Submarine No. 71 | Kawasaki-Kōbe Shipyard | 24-10-1921 | 19-03-1923 | 21-05-1924 as Submarine No. 71 | Renamed Ro-32 01-11-1924. Decommissioned 01-04-1942. Scrapped 1945. |
Project number S30. They were planned as a prototype for a mass production submarines in the wartime under the Maru 1 Programme.
| Boat | Builder | Laid down | Launched | Completed | Results | Fate |
|---|---|---|---|---|---|---|
| Kure Naval Arsenal | 08-08-1933 | 10-10-1934 | 07-10-1935 | Sank Australian merchant ship 07-08-1942 | Sunk by and RAF patrol aircraft off Port Moresby 29-08-1942. | |
| Mitsubishi-Kōbe Shipyard | 25-04-1934 | 12-12-1935 | 31-05-1937 | Sunk by and near Russell Islands 06-04-1943. | ||
Project number S44. The final design in the Kaichū series. They were equipped with a Freon air-conditioner, because the IJN took into consideration that they were to be active on the equator area too. The official IJN designation of these boats was, also called for short, or .
The IJN planned to build these boats under the following Naval Armaments Supplement Programmes:
However some of the boats were cancelled and their naval budgets, materials and staffs were transferred to the I-201 class submarines.
| Boat No. | Boat | Builder | Laid down | Launched | Completed | Results | Fate |
|---|---|---|---|---|---|---|---|
| 201 | Mitsubishi-Kōbe Shipyard | 09-10-1941 | 09-06-1942 | 25-03-1943 | Sunk by near of Espiritu Santo 25-08-1943. | ||
| 202 | Mitsubishi-Kōbe Shipyard | 07-03-1942 | 14-10-1942 | 27-05-1943 | Sunk by north of Saipan 13-06-1944. | ||
| 203 | Sasebo Naval Arsenal | 09-10-1941 | 30-06-1942 | 30-06-1943 | Damaged 22-01-1944 | Sunk by near of Santa Cruz Islands -11.7833°N 181°W 22-01-1944. | |
| 204 | Mitsubishi-Kōbe Shipyard | 20-06-1942 | 24-12-1942 | 24-07-1943 | Disappeared after 19-11-1943. | ||
| 205 | Mitsubishi-Kōbe Shipyard | 08-08-1942 | 06-03-1943 | 12-09-1943 | Sunk by and east of Wotje Atoll 6.8°N 176°W 03-02-1944. | ||
| 206 | Mitsubishi-Kōbe Shipyard | 08-08-1942 | 06-03-1943 | 28-09-1943 | Sunk by north of Marshall Islands 9.8333°N 201°W 16-02-1944. | ||
| 207 | Mitsubishi-Kōbe Shipyard | 06-10-1942 | 05-05-1943 | 26-11-1943 | Sank 03-10-1944 | Sunk by south of Okinawa 22.95°N 151°W 23-03-1945. | |
| 208 | Sasebo Naval Arsenal | 27-04-1942 | 25-10-1942 | 31-08-1943 | Sunk by northeast of Marshall Islands 10.0833°N 190°W 10-06-1945. | ||
| 209 | Mitsubishi-Kōbe Shipyard | 06-10-1942 | 05-06-1943 | 16-12-1943 | Damaged 21-02-1945 | Sunk by aircraft from off Iwo Jima 25.1167°N 159°W 27-02-1945. | |
| 385 | Mitsui-Tamano Shipyard | 14-02-1942 | 11-11-1942 | 13-09-1943 | Sunk by near of Enewetak 11.2167°N 179°W 16-06-1944. | ||
| 386 | Mitsubishi-Kōbe Shipyard | 20-10-1942 | 21-07-1943 | 11-01-1944 | Sunk by, and aircraft from south of Truk 6.2167°N 170°W 01-05-1944. | ||
| 387 | Mitsui-Tamano Shipyard | 13-06-1942 | 23-04-1943 | 19-02-1944 | Damaged 29-01-1945 | Sunk by aircraft from near of Oki Daitō 24.25°N 147°W 29-04-1945. | |
| 388 | Mitsubishi-Kōbe Shipyard | 28-12-1942 | 20-08-1943 | 31-01-1944 | Sunk by northeast of Palau 9.3167°N 180°W 26-09-1944. | ||
| 389 | Mitsubishi-Kōbe Shipyard | 17-03-1943 | 15-10-1943 | 31-03-1944 | (1) Sunk by northwest of Saipan 14-07-1944. (2) Sunk by northwest of Saipan 18-07-1944. | ||
| 390 | Mitsui-Tamano Shipyard | 16-11-1942 | 03-08-1943 | 19-05-1944 | Sunk by . | ||
| 391 | Mitsui-Tamano Shipyard | 18-02-1943 | 27-11-1943 | 31-07-1944 | Sank USS LST-577 11-02-1945 | Decommissioned 30-11-1945. Sunk as target off Gotō Islands 01-04-1946. | |
| 392 - 395 | Cancelled in 1943. | ||||||
| 396 | Mitsui-Tamano Shipyard | 05-08-1943 | 23-04-1944 | 30-09-1944 | Sunk by west of Luzon 15.45°N 144°W 07-02-1945. | ||
| 640 - 644 | Cancelled in 1943. | ||||||
| 645 | (ex-Ro-75) | Mitsui-Tamano Shipyard | 02-12-1943 as Ro-75 | 05-07-1944 | 15-11-1944 | Sunk by and near of Oki Daitō 26.15°N 151°W 09-04-1945. | |
| 646 - 654 | Cancelled in 1943. | ||||||
| 5181 - 5223 | Cancelled in 1943. | ||||||
| Type | Kaichū I (Ro-11) | Kaichū II (Ro-13) | Kaichū III (Ro-16) | Kaichū IV (Ro-26) | |
| Displacement | Surfaced | 720LT | 740LT | 740LT | 750LT |
| Submerged | 1000LT | 1003.1LT | 997LT | 1080LT | |
| Length (overall) | 69.19m (227feet) | 70.1m (230feet) | 70.1m (230feet) | 74.22m (243.5feet) | |
| Beam | 6.35m (20.83feet) | 6.1m (20feet) | 6.12m (20.08feet) | 6.12m (20.08feet) | |
| Draft | 3.43m (11.25feet) | 3.68m (12.07feet) | 3.7m (12.1feet) | 3.73m (12.24feet) | |
| Power plant and shaft | 2 × Sulzer Mk.2 diesels 2 shafts | 2 × Sulzer Mk.2 diesels 2 shafts | 2 × Sulzer Mk.2 diesels 2 shafts | 2 × Sulzer Mk.2 diesels 2 shafts | |
| Power | Surfaced | 2,900 bhp | 2,900 bhp | 2,900 bhp | 2,900 bhp |
| Submerged | 1,200 shp | 1,200 shp | 1,200 shp | 1,200 shp | |
| Speed | Surfaced | 18.2kn | 16.5kn | 16.5kn | 16kn |
| Submerged | 9.1kn | 8.5kn | 8.5kn | 8.5kn | |
| Range | Surfaced | 4000abbr=onNaNabbr=on at 10kn | 6000abbr=onNaNabbr=on at 10kn | 6000abbr=onNaNabbr=on at 10kn | 6000abbr=onNaNabbr=on at 10kn |
| Submerged | 85abbr=onNaNabbr=on at 4kn | 85abbr=onNaNabbr=on at 4kn | 85abbr=onNaNabbr=on at 4kn | 85abbr=onNaNabbr=on at 4kn | |
| Test depth | 30m (100feet) | 30m (100feet) | 45.7m (149.9feet) | 45.7m (149.9feet) | |
| Fuel | 58.4 tons | 75 tons | 75 tons | 75 tons | |
| Complement | 43 | 43 | 46 | 46 | |
| Armament (initial) | • 6 × 4500NaN0 TTs (4 × front, 2 × turret) • 10 × Type 44 torpedoes • 1 × 76.2mm L/23.5 5th Year Type AA gun | • 6 × 4500NaN0 TTs (4 × front, 2 × upper deck) • 10 × Type 44 torpedoes • 1 × 76.2mm L/23.5 5th Year Type AA gun | • 6 × 4500NaN0 TTs (4 × front, 2 × upper deck) • 10 × Type 44 torpedoes • 1 × 76.2mm L/23.5 5th Year Type AA gun | • 4 × 5330NaN0 TTs (4 × front) • 8 × 6th Year Type torpedoes • 1 × 76.2mm L/23.5 5th Year Type AA gun | |
| Type | Kaichū V (Ro-29) | Kaichū VI (Ro-33) | Kaichū VII (Ro-35) | |
| Displacement | Surfaced | 852LT | 700LT | 960LT |
| Submerged | 1030LT | 1200LT | 1447LT | |
| Length (overall) | 74.22m (243.5feet) | 73m (240feet) | 80.5m (264.1feet) | |
| Beam | 6.12m (20.08feet) | 6.7m (22feet) | 7.05m (23.13feet) | |
| Draft | 3.73m (12.24feet) | 3.25m (10.66feet) | 4.07m (13.35feet) | |
| Power plant and shaft | 2 × Sulzer Mk.1 diesels 2 shafts | 2 × Kampon Mk.21 Model 8 diesels 2 shafts | 2 × Kampon Mk.22 Model 10 diesels 2 shafts | |
| Power | Surfaced | 1,200 bhp | 3,000 bhp | 4,200 bhp |
| Submerged | 1,200 shp | 1,200 shp | 1,200 shp | |
| Speed | Surfaced | 13kn | 19kn | 19.8kn |
| Submerged | 8.5kn | 8.2kn | 8kn | |
| Range | Surfaced | 6000abbr=onNaNabbr=on at 10kn | 8000abbr=onNaNabbr=on at 12kn | 5000abbr=onNaNabbr=on at 16kn |
| Submerged | 85abbr=onNaNabbr=on at 4kn | 90abbr=onNaNabbr=on at 3.5kn | 45abbr=onNaNabbr=on at 5kn | |
| Test depth | 45.7m (149.9feet) | 75m (246feet) | 80m (260feet) | |
| Fuel | 143 tons | 109 tons | 218 tons | |
| Complement | 44 | 61 | 61 | |
| Armament (initial) | • 4 × 5330NaN0 TTs (4 × front) • 8 × 6th Year Type torpedoes • 1 × 120mm L/45 11th Year Type Naval gun • 1 × 6.5 mm machine gun | • 4 × 5330NaN0 TTs (4 × front) • 8 × Type 89 torpedoes • 1 × 76.2mm L/40 11th Year Type AA gun • 1 × 13.2mm Type 93 AA gun | • 4 × 5330NaN0 TTs (4 × front) • 10 × Type 95 torpedoes • 1 × 76.2mm L/40 11th Year Type AA gun • 2 × Type 96 25mm AA guns | |