SM U-31 (Germany)

History
German Empire
Name:	U-31
Ordered:	29 March 1912
Builder:	Germaniawerft, Kiel ( 191)
Laid down:	12 October 1912
Launched:	7 January 1914
Commissioned:	18 September 1914
Fate:	13 January 1915 – Final fate unknown. Possibly mined off E coast of UK. 31 dead (all hands lost).
General characteristics
Class & type:	German Type U 31 submarine
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
Service record
Part of:	IV Flotilla 18 September 1914 – 13 January 1915
Commanders:	Oblt.z.S. Siegfried Wachendorff 1 August 1914 – 13 January 1915
Operations:	1 patrol
Victories:	None

SM U-31 was one of the 329 submarines serving in the Imperial German Navy in World War I. U-31 was engaged in the naval warfare and took part in the First Battle of the Atlantic.

U-31 sailed from Wilhelmshaven on 13 January 1915, and disappeared shortly thereafter. It was assumed she had struck a mine and sunk with all hands, somewhere in the North Sea. But six months after her supposed sinking, she drifted ashore on the British east coast. The entire crew was dead. Upon inspection, it was determined that, while lying on the sea floor, the crew had been overcome by poisonous fumes, and the sub had floated to the surface after her ballast tanks had blown independently.

Design

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.

U-31 had an overall length of 64.70 m (212 ft 3 in), her pressure hull was 52.36 m (171 ft 9 in) long. The boat's 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.

U-31 was fitted with two Germania 6-cylinder two-stroke diesel engines with a total of 1,850 metric horsepower (1,361 kW; 1,825 bhp) for use on the surface and two Siemens-Schuckert double-acting electric motors with a total of 1,200 PS (883 kW; 1,184 shp) for underwater use. These engines powered two shafts each with a 1.60 m (5.2 ft) propeller, which gave the boat a top surface speed of 16.4 knots (30.4 km/h; 18.9 mph), and 9.7 knots (18.0 km/h; 11.2 mph) when submerged. Cruising range was 8,790 nautical miles (16,280 km; 10,120 mi) at 8 knots (15 km/h; 9.2 mph) on the surface, and 80 nmi (150 km; 92 mi) at 5 knots (9.3 km/h; 5.8 mph) under water. Diving depth was 50 m (164 ft 1 in).

The U-boat was armed with four 50 cm (20 in) torpedo tubes, two fitted in the bow and two in the stern, and carried 6 torpedoes. The boat's complement was 4 officers and 31 enlisted.

September 2015

U-31 was identified on 9 September 2015 by the Dutch Lamlash wreck-diving team on a place about 65 nautical miles west of IJmuiden (NL) a few miles from the Dutch border in British waters .

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