German Type U 31 submarine

SM U-38, a Type U 31 U-boat
Class overview
Builders:	Germaniawerft, Kiel
Operators:	Kaiserliche Marine
Preceded by:	Type U 27
Succeeded by:	Type U 43
In commission:	3 September 1914
Completed:	11
Lost:	7
General characteristics
Displacement:	685 t (674 long tons) (surfaced) 878 t (864 long tons) (submerged)
Length:	64.70 m (212 ft 3 in) (o/a) 52.36 m (171 ft 9 in) (pressure hull)
Beam:	6.32 m (20 ft 9 in) (o/a) 4.05 m (13 ft 3 in) (pressure hull)
Draught:	3.56 m (11 ft 8 in)
Installed power:	2 × 1,850 PS (1,361 kW; 1,825 shp) diesel engines 2 × 1,200 PS (883 kW; 1,184 shp) Doppelmodyn
Propulsion:	2 × shafts 2 × 1.60 m (5.2 ft) propellers
Speed:	16.4 knots (30.4 km/h; 18.9 mph) (surfaced) 9.7 knots (18.0 km/h; 11.2 mph) (submerged)
Range:	8,790 nmi (16,280 km; 10,120 mi) at 8 knots (15 km/h; 9.2 mph) (surfaced) 80 nmi (150 km; 92 mi) at 5 knots (9.3 km/h; 5.8 mph) (submerged)
Test depth:	50 m (164 ft 1 in)
Boats & landing craft carried:	1 dinghy
Complement:	4 officers, 31 enlisted
Armament:	four 50 cm (20 in) torpedo tubes (2 each bow and stern) 6 torpedoes one or two 7.5 cm (3.0 in) – 10.5 centimetres (4.1 in) deck guns

U 31 was a class of U-boats built during World War I by the Kaiserliche Marine.

Between 1912 and 1915 eleven were built on Germaniawerft in Kiel, amongst these top-three-scoring U-35 with the famous Lothar von Arnauld de la Perière as commander, U-39 with Walter Forstmann and U-38 with Max Valentiner. Together these U-boats sunk more than 1,244,204 gross register tons (GRT).

Later Admiral and head of the Abwehr from 1935 to 1944 Wilhelm Canaris also served as commander on two different U 31 U-boats. He first took over from Max Valentiner on U-38 and later on U-34.

German Type U 31 submarines were double-hulled ocean-going submarines similar to Type 23 and Type 27 subs in dimensions and differed only slightly in propulsion and speed. They were considered very good high sea boats with average manoeuvrability and good surface steering.

Type U-31's had an overall length of 64.70 m (212 ft 3 in), their pressure hulls were 52.36 m (171 ft 9 in) long. The boats' beam was 6.32 m (20 ft 9 in) (o/a), while the pressure hull measured 4.05 m (13 ft 3 in). Type 31s had a draught of 3.56 m (11 ft 8 in) with a total height of 7.68–8.04 m (25 ft 2 in–26 ft 5 in). The boats displaced a total of 971 tonnes (956 long tons); 685 t (674 long tons) when surfaced and 878 t (864 long tons) when submerged.