Type B1-class Submarine

Ships in class: 20

The Type B submarines were derived from the earlier KD6 sub-class of the Kaidai class and were equipped with an aircraft to enhance their scouting ability. They displaced 2,631 tonnes (2,589 long tons) surfaced and 3,713 tonnes (3,654 long tons) submerged. The submarines were 108.7 meters long, had a beam of 9.3 meters and a draft of 5.1 meters. They had a diving depth of 100 meters.

The boats were armed with six internal bow 53.3 cm (21.0 in) torpedo tubes and carried a total of 17 torpedoes. They were also armed with a single 14 cm (5.5 in) deck gun and two single mounts for 25 mm (1 in) Type 96 anti-aircraft guns. In the Type B’s, the aircraft hangar was faired into the base of the conning tower. A single catapult was positioned on the forward deck. Late in the war, some of the submarines had their aircraft hangar replaced, to replace it with an additional 14 cm gun.