Type KD1


(National Archives photo, scanned from Polmar & Carpenter's "Submarines of the Imperial Japanese Navy")

Prototype for the large I-boats (KD2-KD7 types) which followed, this design was based on the German U-139 from the First World War.  Like her successors, I-51 had a double hull and mobility comparable to battleships of the day in order to operate with the battle fleet.  She received new engines in 1932, but never saw combat and was scrapped in 1941.

Units1 (Scrapped pre-war)
Year(s) Completed 1924
Displacement1,500 tons / 2,430 tons
Dimensions300 ft x 29 ft x 15 ft
Machinery 4 diesels: 5,200 hp

electric motors: 2,000 hp

Speed20 knots / 10 knots
Range20,000 nm @ 10 knots
Armament 6x533mm TT fwd + 2x533mm TT aft + 1x12cm/50 cal. (24 Torpedoes)
Max. Depth60 m (200 feet)
Crew60 officers and men