SM UB-21 was a German Type UB II submarine or U-boat in the Imperial German Navy () during World War I. The U-boat was ordered on 30 April 1915 and launched on 26 September 1915. She was commissioned into the German Imperial Navy on 20 February 1916 as SM UB-21. The submarine sank 33 ships in 26 patrols for a total of . Surrendered to Britain in accordance with the requirements of the Armistice with Germany, UB-21 was sunk as a target by in the Solent on 30 September 1920; the wreck was sold in 1970 and most had been cleared by 1998, although some remnants survive.
Design A Type UB II submarine, UB-21 had a displacement of when at the surface and while submerged. She had a total length of , a beam of , and a draught of . The submarine was powered by two Körting six-cylinder, four-stroke diesel engines producing a total of , two Siemens-Schuckert electric motors producing , and one propeller shaft. 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 . UB-21 was fitted with two torpedo tubes, four torpedoes, and one SK L/40 deck gun. She had a complement of twenty-one crew members and two officers and a 45-second dive time.
Summary of raiding history DateNameNationalityTonnageTonnages are in gross register tonsFate5 May 1916Harald275Sunk20 October 1916Lekna204Sunk20 October 1916Randi467Sunk20 October 1916Svartvik322Sunk21 October 1916Fritzöe641Captured as prize21 October 1916Grönhaug667Sunk22 October 1916London184Sunk22 October 1916Thor372Sunk3 November 1916Pluto1,148Captured as prize16 February 1917Lady Ann1,016Sunk17 February 1917Excel157Sunk22 February 1917John Miles687Sunk29 March 1917Bywell1,522Sunk31 March 1917Norden776Captured as prize29 April 1917Victoria1,620Sunk2 May 1917Rikard Noordrak1,123Sunk5 May 1917Edith Cavell20Sunk6 May 1917Harold1,679Sunk8 May 1917Batavier II157Captured as prize6 June 1917S.N.A. 22,294Sunk7 June 1917Sir Francis1,991Sunk21 July 1917Trelyon3,099Sunk22 July 1917Glow1,141Sunk23 July 1917Vanland1,285Sunk24 August 1917Springhill1,507Sunk18 October 1917Amsteldam1,233Sunk19 October 1917Gemma1,385Sunk23 November 1917Ocean1,442Sunk29 December 1917Inverness3,734Damaged29 December 1917Patria838Sunk30 December 1917Hercules1,295Sunk25 March 1918Hercules1,095Sunk8 May 1918Constantia772Sunk10 May 1918Anboto Mendi2,114Sunk11 May 1918Gothia1,826Sunk12 May 1918Haslingden1,934Sunk4 July 1918Mentor539Sunk26 September 1918Paul659Sunk
References
Notes
Citations
Bibliography