SM U-91

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History
German Empire
Name: U-91
Ordered: 23 June 1915
Builder: Kaiserliche Werft Danzig
Yard number: 35
Laid down: 1 August 1916
Launched: 14 April 1917
Commissioned: 17 September 1917
Fate: Surrendered 26 November 1918
General characteristics [1]
Class and type: German Type U 87 submarine
Displacement:
  • 757 t (745 long tons) surfaced
  • 998 t (982 long tons) submerged
Length:
Beam:
  • 6.20 m (20 ft 4 in) (oa)
  • 4.18 m (13 ft 9 in) (pressure hull)
Height: 9.35 m (30 ft 8 in)
Draught: 3.88 m (12 ft 9 in)
Installed power:
  • 2 × 2,400 PS (1,765 kW; 2,367 shp) surfaced
  • 2 × 1,200 PS (883 kW; 1,184 shp) submerged
Propulsion: 2 shafts, 2 × 1.66 m (5 ft 5 in) propellers
Speed:
  • 16.8 knots (31.1 km/h; 19.3 mph) surfaced
  • 9.1 knots (16.9 km/h; 10.5 mph) submerged
Range:
  • 11,380 nmi (21,080 km; 13,100 mi) at 8 knots (15 km/h; 9.2 mph) surfaced
  • 56 nmi (104 km; 64 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged
Test depth: 50 m (160 ft)
Complement: 4 officers, 32 enlisted
Armament:
Service record
Part of:
Commanders:
  • Kptlt. Alfred von Glasenapp[2]
  • 17 September 1917 – 11 November 1918
Operations: 8 patrols
Victories:

SM U-91[Note 1] was one of the 329 submarines serving in the Imperial German Navy in World War I. U-91 was engaged in the naval warfare and took part in the First Battle of the Atlantic.[3]

Design[edit]

German Type U 87 submarines were preceded by the shorter Type U 81 submarines. U-91 had a displacement of 757 tonnes (745 long tons) when at the surface and 998 tonnes (982 long tons) while submerged.[1] She had a total length of 65.80 m (215 ft 11 in), a pressure hull length of 50.07 m (164 ft 3 in), a beam of 6.20 m (20 ft 4 in), a height of 9.35 m (30 ft 8 in), and a draught of 3.88 m (12 ft 9 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).[1]

The submarine had a maximum surface speed of 15.6 knots (28.9 km/h; 18.0 mph) and a maximum submerged speed of 8.6 knots (15.9 km/h; 9.9 mph).[1] 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 11,380 nautical miles (21,080 km; 13,100 mi) at 8 knots (15 km/h; 9.2 mph). U-91 was fitted with four 50 centimetres (20 in) torpedo tubes (two at the bow and two at the stern), ten to twelve torpedoes, one 10.5 cm (4.1 in) SK L/45 deck gun, and one 8.8 cm (3.5 in) SK L/30 deck gun. She had a complement of thirty-six (thirty-two crew members and four officers).[1]

Summary of raiding history[edit]

Date Name Nationality Tonnage[Note 2] Fate[4]
24 December 1917 Elmleaf  United Kingdom 5,948 Damaged
28 December 1917 Robert Eggleton  United Kingdom 2,274 Sunk
2 January 1918 Boston City  United Kingdom 2,711 Sunk
4 January 1918 Otto  United Kingdom 139 Sunk
5 January 1918 Knightsgarth  United Kingdom 2,889 Sunk
7 January 1918 Premier  United Kingdom 89 Sunk
19 February 1918 Beacon Light  United Kingdom 2,768 Sunk
22 February 1918 Haileybury  United Kingdom 2,888 Sunk
23 February 1918 Birchleaf  United Kingdom 5,873 Damaged
23 February 1918 British Viscount  United Kingdom 3,287 Sunk
24 February 1918 Renfrew  United Kingdom 3,830 Sunk
2 March 1918 Bessy  United Kingdom 60 Sunk
20 April 1918 Florrieston  United Kingdom 3,366 Sunk
20 April 1918 Lowther Range  United Kingdom 3,926 Sunk
21 April 1918 Landonia  United Kingdom 2,504 Sunk
21 April 1918 Normandiet  United Kingdom 1,843 Sunk
22 April 1918 Baron Herries  United Kingdom 1,610 Sunk
26 April 1918 Ethel  United Kingdom 100 Sunk
27 April 1918 Gresham  United Kingdom 3,774 Sunk
27 April 1918 Walpas  Russian Empire 312 Sunk
28 April 1918 Damao  Portugal 5,668 Sunk
28 April 1918 Oronsa  United Kingdom 8,075 Sunk
1 July 1918 Westmoor  United Kingdom 4,329 Sunk
6 July 1918 Port Hardy  United Kingdom 6,533 Sunk
9 July 1918 Silvia  Kingdom of Italy 3,571 Sunk
13 July 1918 Badagri  United Kingdom 2,956 Sunk
16 July 1918 Fisherman  United Kingdom 136 Sunk
25 July 1918 Tippecanoe  United States 6,187 Sunk
1 October 1918 Therese et Marthe  France 32 Sunk
2 October 1918 Maia  France 185 Sunk
2 October 1918 Marie Emmanuel  France 32 Sunk
2 October 1918 Ave Maris Stella  France 22 Sunk
4 October 1918 Mercedes  Spain 2,164 Sunk
5 October 1918 Heathpark  United Kingdom 2,205 Sunk
5 October 1918 Erindring  United Kingdom 1,229 Sunk
8 October 1918 Cazengo  Portugal 3,009 Sunk
9 October 1918 Pierre  France 354 Sunk
11 October 1918 Luksefjell  Norway 2,007 Sunk
14 October 1918 Bayard  France 55 Sunk

References[edit]

Notes[edit]

  1. ^ "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.
  2. ^ Tonnages are in gross register tons

Citations[edit]

  1. ^ a b c d e Gröner 1991, pp. 12-14.
  2. ^ Helgason, Guðmundur. "WWI U-boat commanders: Alfred von Glasenapp (Royal House Order of Hohenzollern)". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 21 January 2015. 
  3. ^ Helgason, Guðmundur. "WWI U-boats: U 91". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 25 January 2010. 
  4. ^ Helgason, Guðmundur. "Ships hit by U 91". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 21 January 2015. 

Bibliography[edit]

  • Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.