German submarine U-731
|Ordered:||5 June 1941|
|Laid down:||1 October 1941|
|Launched:||25 July 1942|
|Commissioned:||3 October 1942|
|Fate:||Sunk 15 May 1944 near Tangier by British patrol vessels|
|Class and type:||Type VIIC submarine|
|Height:||9.60 m (31 ft 6 in)|
|Draught:||4.74 m (15 ft 7 in)|
|Complement:||4 officers, 40–56 enlisted|
|Identification codes:||M 50 791|
|Operations:||4 war patrols|
|Victories:||no ships sunk|
German submarine U-731 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 1 October 1941 at the Schichau-Werke yard at Danzig, launched on 25 July 1942, and commissioned on 3 October 1942 under the command of Oberleutnant zur See Werner Techand.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-731 had a displacement of 769 tonnes (757 long tons) when at the surface and 871 tonnes (857 long tons) while submerged. She had a total length of 67.10 m (220 ft 2 in), a pressure hull length of 50.50 m (165 ft 8 in), a beam of 6.20 m (20 ft 4 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.74 m (15 ft 7 in). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two AEG GU 460/8–27 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged. She had two shafts and two 1.23 m (4 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 17.7 knots (32.8 km/h; 20.4 mph) and a maximum submerged speed of 7.6 knots (14.1 km/h; 8.7 mph). When submerged, the boat could operate for 80 nautical miles (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 8,500 nautical miles (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph). U-731 was fitted with five 53.3 cm (21 in) torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm (3.46 in) SK C/35 naval gun, 220 rounds, and an anti-aircraft gun. The boat had a complement of between forty-four and sixty.
On the fourth and final war patrol, U-731 was detected on 15 May 1944 by two Catalinas, P-14 and P-1, of VP-63 off Tangiers, when the U-boat tried to force the Strait of Gibraltar. Two British patrol craft, HMS Kilmarnock and HMS Blackfly, received reports of the U-boat and attacked with hedgehogs. U-731 was sunk in position Coordinates: ; all 54 crew members perished in the attack.
- Busch, Rainer; Röll, Hans-Joachim (1999). Deutsche U-Boot-Verluste von September 1939 bis Mai 1945. Der U-Boot-Krieg (in German) IV (Hamburg, Berlin, Bonn: Mittler). ISBN 3-8132-0514-2.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945 2. Translated by Thomas, Keith; Magowan, Rachel (London: Conway Maritime Press). ISBN 0-85177-593-4.
- Helgason, Guðmundur. "The Type VIIC boat U-731". German U-boats of WWII - uboat.net. Retrieved 23 July 2015.