# 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 Mantola 143 nautical miles (265 km; 165 mi) off Fastnet, forcing her crew and passengers to abandon her. She then shelled the drifting hulk until being chased away by the Acacia-class sloop HMS Laburnum. Mantola sank the next day. HMS E54 sank U-81 by torpedo west of Ireland on 1 May 1917. 31 of U-81's crew were killed; seven survived.

## Design

Type U 81 submarines were preceded by the shorter Type UE I submarines. U-81 had a displacement of 808 tonnes (795 long tons) when at the surface and 946 tonnes (931 long tons) while submerged. She had a total length of 70.06 m (229 ft 10 in), a pressure hull length of 55.55 m (182 ft 3 in), a beam of 6.30 m (20 ft 8 in), a height of 8 m (26 ft 3 in), and a draught of 4.02 m (13 ft 2 in). The submarine was powered by two 2,400 metric horsepower (1,800 kW; 2,400 shp) engines for use while surfaced, and two 1,200 metric horsepower (880 kW; 1,200 shp) engines for use while submerged. She had two propeller shafts. She was capable of operating at depths of up to 50 metres (160 ft).
The submarine had a maximum surface speed of 16.8 knots (31.1 km/h; 19.3 mph) and a maximum submerged speed of 9.1 knots (16.9 km/h; 10.5 mph). When submerged, she could operate for 56 nautical miles (104 km; 64 mi) at 5 knots (9.3 km/h; 5.8 mph); when surfaced, she could travel 11,220 nautical miles (20,780 km; 12,910 mi) at 8 knots (15 km/h; 9.2 mph). U-81 was fitted with four 50-centimetre (20 in) torpedo tubes (one at the starboard bow and one starboard stern), twelve to sixteen torpedoes, and one 10.5 cm (4.1 in) SK L/45 deck gun. She had a complement of thirty-five (thirty-one crew members and four officers).

## Summary of raiding history

| Date | Name | Nationality | Tonnage | Fate |
| 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 | Kingdom of Italy | 992 | Sunk |
| 5 February 1917 | Wartenfels | United Kingdom | 4,511 | Sunk |
| 7 February 1917 | Gravina | United Kingdom | 1,242 | Sunk |
| 8 February 1917 | Mantola | 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 | Kingdom of Italy | 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 |