German Type U 139 submarine

Class overview
Builders:	Germaniawerft, Kiel
Operators:	Kaiserliche Marine
Completed:	3
General characteristics
Displacement:	1,930 t (1,900 long tons) surfaced 2,483 t (2,444 long tons) submerged 3,050 t (3,000 long tons) total
Length:	92.00 m (301 ft 10 in) (o/a) 71.50 m (234 ft 7 in) (pressure hull)
Beam:	9.12 m (29 ft 11 in) (o/a) 5.75 m (18 ft 10 in) (pressure hull)
Height:	11.20 m (36 ft 9 in)
Draught:	5.27 m (17 ft 3 in)
Installed power:	2 × diesel engines, 3,300 PS (2,400 kW; 3,300 shp) (surfaced) 1,780 PS (1,310 kW; 1,760 shp) (submerged)
Propulsion:	2 shafts 2 2.10 m (6 ft 11 in) propellers
Speed:	15.8 knots (29.3 km/h; 18.2 mph) surfaced 7.6 knots (14.1 km/h; 8.7 mph) submerged
Range:	17,750 nautical miles (32,870 km; 20,430 mi) at 8 knots (15 km/h; 9.2 mph) surfaced 53 nautical miles (98 km; 61 mi) at 4.5 knots (8.3 km/h; 5.2 mph) submerged
Test depth:	75 m (246 ft)
Boats & landing craft carried:	1 cutter
Complement:	6 (1) officers, 56 (20) men (prize crew)
Armament:	6 × 53.3 cm (21 in) torpedo tubes (4 bow, 2 stern) 24 G6 torpedoes 2 × 15 cm (5.9 in) deck guns with 980 rounds 2 × 8.8 cm (3.5 in) deck guns with 200 rounds

U-139, originally designated "Project 46", was a class of large, long-range U-boats built during World War I by the Kaiserliche Marine.

Three large U-cruisers, designated Type 139, were ordered from Germaniawerft, Kiel, in August 1916. Displacing nearly 2,000 tons, and with a surface speed of 15 knots (28 km/h; 17 mph), they were armed with 24 torpedoes and two 15 cm deck guns, and had a cruising range of around 17,000 nautical miles (31,000 km; 20,000 mi). They carried a large enough complement to furnish captured vessels with prize crews and their intended purpose was to capture or destroy merchantmen on the surface; their large-calibre deck guns and comparatively high speed allowed them to engage even armed merchant vessels.

Unlike the earlier Type U-151 submarines (originally designed as merchant submarines to evade naval blockades), the Type 139 was designed from the outset for war service. Four bow and two stern torpedo tubes were fitted, but the main armament was the two 15 cm deck guns, which could be laid by a rangefinder on the aft section of the bridge. The conning tower's command centre was protected by 90mm armour against the guns typically carried by enemy merchant ships, while the pressure hull was thicker than usual at 25mm, so as to increase diving depth. The superstructure was also raised by 2m so that a shell hitting it would not penetrate the pressure hull.

A Type 139 U-boat cost 8.7 million Marks at the time, the 15 cm guns accounting for around 7% of the cost. Three submarines of this type, U-139, U-140, and U-141, were ordered.

The later "Project 46(a)" specified even more powerful U-cruisers, of a similar displacement to the Type 139 boats, but with an increased surface speed of 18 knots (33 km/h; 21 mph), and with two 88mm deck guns in addition to the two 150mm guns.

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Wikipedia