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.[1]
U-81 had one 10.5 cm gun with 140–240 rounds.[1] On 8 February 1917 she torpedoed off Fastnet, forcing her crew and passengers to abandon her. She then shelled the drifting hulk until being chased away by the sloop . Mantola sank the next day.[2] [3] HMS E54 sank U-81 by torpedo west of Ireland on 1 May 1917. 31 of U-81s crew were killed; seven survived.[1]
Type U 81 submarines were preceded by the shorter Type UE I submarines. U-81 had a displacement of 808t when at the surface and 946t while submerged. She had a total length of 70.06m (229.86feet), a pressure hull length of 55.55m (182.25feet), a beam of 6.3m (20.7feet), a height of 8m (26feet), and a draught of 4.02m (13.19feet). The submarine was powered by two 2400PS engines for use while surfaced, and two 1200PS 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 16.8kn and a maximum submerged speed of . When submerged, she could operate for 56nmi at ; when surfaced, she could travel at . U-81 was fitted with four 50cm (20inches) torpedo tubes (one at the starboard bow and one starboard stern), twelve to sixteen torpedoes, and one 10.5cm (04.1inches) SK L/45 deck gun. She had a complement of thirty-five (thirty-one crew members and four officers).
| Date | Name | Nationality | Tonnage[4] | Fate[5] | |
|---|---|---|---|---|---|
| 1 December 1916 | Douglas |  Sweden | 1,177 | Sunk | |
| 19 December 1916 | Nystrand |  Norway | 1,397 | Sunk | |
| 2 February 1917 | Songdal | Norway | 2,090 | Sunk | |
| 3 February 1917 | Port Adelaide |  United Kingdom | 8,181 | Sunk | |
| 4 February 1917 | Maria | 992 | Sunk | ||
| 5 February 1917 | Wartenfels | United Kingdom | 4,511 | Sunk | |
| 7 February 1917 | Gravina | United Kingdom | 1,242 | Sunk | |
| 8 February 1917 | United Kingdom | 8,253 | Sunk | ||
| 10 February 1917 | Netherlee | United Kingdom | 4,227 | Sunk | |
| 12 February 1917 | Hugo Hamilton | Sweden | 2,577 | Sunk | |
| 10 March 1917 | Algol | Norway | 988 | Sunk | |
| 10 March 1917 | Skreien | Norway | 415 | Sunk | |
| 13 March 1917 | Coronda | United Kingdom | 2,733 | Sunk | |
| 14 March 1917 | Paignton | United Kingdom | 2,017 | Sunk | |
| 18 March 1917 | Pola | United Kingdom | 3,061 | Sunk | |
| 18 March 1917 | Trevose | United Kingdom | 3,112 | Sunk | |
| 19 March 1917 | Alnwick Castle | United Kingdom | 5,900 | Sunk | |
| 19 March 1917 | Frinton | United Kingdom | 4,194 | Sunk | |
| 22 March 1917 | Attika | Norway | 2,306 | Sunk | |
| 25 March 1917 | C. Sundt | Norway | 1,105 | Sunk | |
| 25 March 1917 | Garant | Norway | 735 | Sunk | |
| 25 March 1917 | Laly | Norway | 1,880 | Sunk | |
| 24 April 1917 | Amulree | United Kingdom | 1,145 | Sunk | |
| 25 April 1917 | Glenesk | Norway | 1,369 | Sunk | |
| 25 April 1917 | Heathfield | United Kingdom | 1,643 | Sunk | |
| 25 April 1917 | Invermay | United Kingdom | 1,471 | Sunk | |
| 27 April 1917 | Uranus | 3,978 | Sunk | ||
| 28 April 1917 | Jose De Larrinaga | United Kingdom | 5,017 | Sunk | |
| 28 April 1917 | Terence | United Kingdom | 4,309 | Sunk | |
| 30 April 1917 | Elisabeth |  Denmark | 217 | Damaged | |
| 1 May 1917 | Dorie | United Kingdom | 3,264 | Damaged | |
| 1 May 1917 | San Urbano | United Kingdom | 6,458 | Sunk |