Ha-101-class submarine

The Ha-101-class submarine (波百一型潜水艦) was a transport submarine built for the Imperial Japanese Navy (IJN) during World War II. The IJN planned to build 12 boats, but only 10 vessels were completed by the end of the war. The IJN called these submarines Sen'yu-Shō type submarine (潜輸小型潜水艦). The type name, was shortened to Yusō Sensuikan Ko-gata (輸送潜水艦小型).

Several boats were converted to tankers or mother ships for the Kō-hyōteki model D "Kōryū" (甲標的丁型 蛟龍) midget submarines.

Design and description
The Ha-101-class submarines were designed as small, cheap transport submarines to resupply isolated island garrisons. They displaced 429 LT surfaced and 493 LT submerged. The submarines were 44.5 m long, had a beam of 6.1 m and a draft of 4.04 m. They were designed to carry 60 t of cargo.

For surface running, the boats were powered by a single 400 bhp diesel engine that drove one propeller shaft. When submerged the propeller was driven by a 140 hp electric motor. They could reach 10 kn on the surface and 5 kn underwater. On the surface, the Ha-101s had a range of 3000 nmi at 10 kn; submerged, they had a range of 46 nmi at 2.3 kn. The boats were armed a single mount for a 25 mm Type 96 anti-aircraft gun.

Planned construction
Project number S57. In February 1944, the IJN planned a small-size transport submarine, the IJA planned the Maru Yu.