Type 3 submergence transport vehicle

Yu 1 in Hitachi Ltd., Kasado Factory (1943)
Class overview
Name:	Type 3 submergence transport vehicle
Builders:	Hitachi Ltd. Japan Steel Works Andō Iron Works Chōsen Machinery
Operators:	Imperial Japanese Army
Subclasses:	Yu I type Yu 1 (Hitachi Ltd.) Yu 1001 (Japan Steel Works) Yu 2001 (Andō Iron Works) Yu 3001 (Chōsen Machinery) Yu II type Ushio (Prototype, Hitachi Ltd.)
Built:	1943–45
In commission:	1943–45
Planned:	400 and more
Completed:	38
Lost:	5
Scrapped:	34
General characteristics Yu I type
Type:	Transport submarine
Displacement:	274 long tons (278 t) surfaced 346 long tons (352 t) submerged
Length:	41.40 m (135 ft 10 in) overall
Beam:	3.90 m (12 ft 10 in)
Draft:	3.00 m (9 ft 10 in)
Propulsion:	2 × Hesselman engines 400 bhp surfaced 75 shp submerged single shaft
Speed:	10 knots (19 km/h) surfaced 4 knots (7.4 km/h) submerged
Range:	1,500 nmi (2,800 km) at 8 knots (15 km/h) surfaced 32 nmi (59 km) at 4 knots (7.4 km/h) submerged
Test depth:	100 m (330 ft)
Capacity:	24 tons freight or 40 troops
Complement:	23
Armament:	Yu 1, Yu 2 and Yu 3 1 × Type 4 37 mm shipboard gun 5 × Type 99 light machine guns Yu 1001 1 × Type 4 37 mm shipboard gun 2 × IJN Type 92 13 mm AA guns Yu 2001 1 × Type 4 37 mm shipboard gun
General characteristics Yu II type
Type:	Transport submarine
Displacement:	430 long tons (437 t) surfaced 540 long tons (549 t) submerged
Length:	55.00 m (180 ft 5 in) overall
Beam:	7.00 m (23 ft 0 in)
Draft:	3.13 m (10 ft 3 in)
Propulsion:	2 × intermediate diesels 700 bhp surfaced, 2 shafts
Speed:	14.5 knots (26.9 km/h; 16.7 mph) surfaced 4.5 knots (8.3 km/h; 5.2 mph) submerged
Test depth:	150 m (492 ft 2 in)
Capacity:	40 tons freight
Armament:	1 × Type 1 47 mm AT gun 5 × Type 98 20 mm AA guns

The Type 3 submergence transport vehicle (三式潜航輸送艇, San-Shiki Senkō Yusōtei^?) was a class of transport submarines built for the Imperial Japanese Army (IJA) during the Second World War. The IJA planned to build over 400 boats, however only 38 boats were completed until the end of war. The IJA called them Maru Yu (マルゆ^?).

In 1943 the IJA decided to build a transport submarine for themselves, because the IJA was soundly beaten in the Solomon Islands campaign and needed a way to supply the isolated garrisons on the Pacific islands.

The class consists of four unofficial subclasses resulting from manufacturing differences among the contracted builders. The manufacturer may be discerned by the appearance of the sail.

Basic model of Yu I type. First boat Yu 1 was prototype of the Yu I type boats. The Hitachi-Kasado Factory built all of the Yu 1-class boats. Their sail was closed.

The Japan Steel Works-Kaita Factory built all of the Yu 1001-class boats. They were equipped with an open-top sail.

The Andō Iron Works-Tsukishima Factory build all of the Yu 2001-class boats. First boat (Yu-2001) was the second prototype of the Yu I type boats. They fitted a deck house root to the sail for improved crew comfort.

The Chōsen Machinery-Jinsen Factory build all of the Yu 3001-class boats.

Improved model of the Yu I type. Yu II was built by Kampon technical guidance. The IJN used the Ha-101-class submarine drawings and designed this.