SM U-40 (Germany)

SM U-40 was a German Type U 31 U-boat of the German Imperial Navy (Kaiserliche Marine) during World War I.

Her construction was ordered on 12 June 1912 and her keel was laid down on 3 April 1913 by Germaniawerft of Kiel. She was launched on 22 October 1914 and commissioned on 14 February 1915 under the command of Gerhardt Fürbringer. Second officer was lieutenant Rudolf Jauch (of the Jauch family).

U-40 conducted one patrol, without sinking a ship.

Design
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-40 had an overall length of 64.70 m, her pressure hull was 52.36 m long. The boat's 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.

U-40 was 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 boat 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, and 80 nmi at 5 kn under water. Diving depth was 50 m.

The U-boat was armed with four 50 cm torpedo tubes, two fitted in the bow and two in the stern, and carried 6 torpedoes. Additionally U-40 was equipped in 1915 with one 8.8 cm Uk L/30 deck gun. The boat's complement was 4 officers and 31 enlisted.

Fate
On the morning of 23 June 1915 U-40 stopped the trawler Taranaki in the North Sea. Taranaki was in fact a decoy vessel, or "Q-ship", and was connected to the submerged submarine HMS C24 by a combined tow line and telephone cable. When U-40 stopped the trawler, Taranaki telephoned the situation to C24. When C24 tried to slip the tow line, however, the release mechanism failed, and C24 had to manoeuvre into an attacking position with a hundred fathoms of chain hanging from her bow. Her commander, Lieutenant Frederick Henry Taylor, was able to adjust her trim and avoid fouling the chain in the propellers and fired a single torpedo that struck U-40 amidships. The U-boat sank instantly, only three men in the conning tower surviving to be picked up by Taranaki.

Wreck discovery
The reported location of the sinking varied. According to some sources it was "50 nmi southeast of Aberdeen". Others suggested it was "east of the Firth of Forth".

However, in March 2009 the Scottish company Marine Quest announced that divers from their company had discovered the wreck of U-40 approximately 40 nmi off Eyemouth, Berwickshire, Scotland, "miles from where it was recorded as going down".