SM U-91
Introduction '''SM ''U-91''''' 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.
Design German Type U 87 submarines were preceded by the shorter Type U 81 submarines. ''U-91'' 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-91'' was fitted with four  torpedo tubes (two at the bow and two at the stern), ten to twelve torpedoes, one  SK L/45 deck gun, and one  SK L/30 deck gun. She had a complement of thirty-six (thirty-two crew members and four officers).
Summary of raiding history DateNameNationalityTonnageFate24 December 1917''Elmleaf''5,948Damaged28 December 1917''Robert Eggleton''2,274Sunk2 January 1918''Boston City''2,711Sunk4 January 1918''Otto''139Sunk5 January 1918''Knightsgarth''2,889Sunk7 January 1918''Premier''89Sunk19 February 1918''Beacon Light''2,768Sunk22 February 1918''Haileybury''2,888Sunk23 February 1918''Birchleaf''5,873Damaged23 February 1918''British Viscount''3,287Sunk24 February 1918''Renfrew''3,830Sunk2 March 1918''Bessy''60Sunk20 April 1918''Florrieston''3,366Sunk21 April 1918''Landonia''2,504Sunk21 April 1918''Normandiet''1,843Sunk22 April 1918''Baron Herries''1,610Sunk26 April 1918''Ethel''100Sunk27 April 1918''Gresham''3,774Sunk27 April 1918''Walpas''312Sunk28 April 1918''Damao''5,668Sunk28 April 1918''Oronsa''8,075Sunk28 April 1918''Raymond''109Sunk1 July 1918''Westmoor''4,329Sunk6 July 1918''Port Hardy''6,533Sunk9 July 1918''Silvia''3,571Sunk13 July 1918''Badagri''2,956Sunk16 July 1918''Fisherman''136Sunk25 July 1918''Tippecanoe''6,187Sunk1 October 1918''Therese et Marthe''32Sunk2 October 1918''Maia''185Sunk2 October 1918''Marie Emmanuel''32Sunk2 October 1918''Ave Maris Stella''22Sunk4 October 1918''Mercedes''2,164Sunk5 October 1918''Heathpark''2,205Sunk5 October 1918''Erindring''1,229Sunk8 October 1918''Cazengo''3,009Sunk9 October 1918''Pierre''354Sunk11 October 1918''Luksefjell''2,007Sunk14 October 1918''Bayard''55Sunk
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