Type U 31 submarine

Type 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 SMU U-35 (Germany) with the famous Lothar von Arnauld de la Perière as commander, SMU U-39 with Walter Forstmann and SMU U-38 with Max Valentiner. Together these U-boats sunk more than.

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

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.

Type U-31s had an overall length of 64.70 m, their pressure hulls were 52.36 m long. The boats' beam was 6.32 m (o/a), while the pressure hull measured 4.05 m. Type 31s had a draught of 3.56 m with a total height of 7.68 - 8.04 m. The boats displaced a total of 971 t; 685 t when surfaced and 878 t when submerged.

Type U-31s were fitted with two Germania 6-cylinder two-stroke diesel engines with a total of 1850 PS for use on the surface and two Siemens-Schuckert double-acting electric motors with a total of 1200 PS for underwater use. These engines powered two shafts each with a 1.60 m propeller, which gave the boats a top surface speed of 16.4 kn, and 9.7 kn when submerged. Cruising range was 8790 nmi at 8 kn on the surface. Diving depth was 50 m.

The U-boats were armed with four 50 cm torpedo tubes, two fitted in the bow and two in the stern, and carried 6 torpedoes. Most boats received one or two 8.8 cm SK L/30 deck guns, which were later replaced with 10.5 cm SK L/45 guns on some. The boats' complement was 4 officers and 31 enlisted.

List of Type U 31 submarines
There were eleven Type U 31 submarines commissioned into the Kaiserliche Marine.