SM U-81
SM "U-81" was one of the 329 submarines serving in the Imperial German Navy ("Kaiserliche Marine") in World War I. "U-81" was engaged in naval warfare and took part in the First Battle of the Atlantic. "U-81" had one 10.5 cm gun with 140–240 rounds. On 8 February 1917 she torpedoed the off Fastnet, forcing her crew to abandon her. She then shelled the drifting hulk until being chased away by the sloop . "Laburnum" took the floating hulk under tow, but the line parted in the rough seas, and "Mantola" was left to sink, which she did on  9 February. She was torpedoed and sunk west of Ireland on 1 May 1917 by HMS "E54"; 31 of her crew died, there were seven survivors. Design. German Type U 81 submarines were preceded by the shorter Type UE I submarines. "U-81" had a displacement of when at the surface and while submerged. She had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two engines for use while surfaced, and two engines for use while submerged. She had two propeller shafts. She was capable  of operating at depths of up to . The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . "U-81" was fitted with four torpedo tubes (one at the starboard bow and one starboard stern), twelve to sixteen torpedoes, and one SK L/45 deck gun. She had a complement of thirty-five (thirty-one crew members and four officers).