SM UB-20 was a German Type UB II submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) 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 10 February 1916 as SM UB-20. The submarine sank 13 ships in 15 patrols for a total of 10,230 gross register tons (GRT). UB-20 was mined and sunk on 28 July 1917 at 51°25′N 3°20′W. Thirteen crew members died in the event.
SM UB-45, a u-boat similar to UB-20
|Ordered:||30 April 1915|
|Builder:||Blohm & Voss, Hamburg|
|Launched:||26 September 1915|
|Completed:||8 February 1916|
|Commissioned:||10 February 1916|
|Fate:||sunk by mine, 28 July 1917|
|Class and type:||German Type UB II submarine|
|Draught:||3.70 m (12 ft 2 in)|
|Test depth:||50 m (160 ft)|
|Complement:||2 officers, 21 men|
|Notes:||45-second diving time|
A German Type UB II submarine, UB-20 had a displacement of 263 tonnes (259 long tons) when at the surface and 292 tonnes (287 long tons) while submerged. She had a total length of 36.13 m (118 ft 6 in), a beam of 4.36 m (14 ft 4 in), and a draught of 3.70 m (12 ft 2 in). The submarine was powered by two Körting six-cylinder, four-stroke diesel engines each producing a total 284 metric horsepower (209 kW; 280 shp), a Siemens-Schuckert electric motor producing 280 metric horsepower (210 kW; 280 shp), and one propeller shaft. She was capable of operating at depths of up to 50 metres (160 ft).
The submarine had a maximum surface speed of 9.15 knots (16.95 km/h; 10.53 mph) and a maximum submerged speed of 5.81 knots (10.76 km/h; 6.69 mph). When submerged, she could operate for 45 nautical miles (83 km; 52 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 6,650 nautical miles (12,320 km; 7,650 mi) at 5 knots (9.3 km/h; 5.8 mph). UB-20 was fitted with two 50 centimetres (20 in) torpedo tubes, four torpedoes, and one 5 cm (2.0 in) SK L/40 deck gun. She had a complement of twenty-three crew members and two officers and a 45-second dive time.
Summary of raiding history
|2 August 1916||Bror Oskar||368||Sunk|
|2 August 1916||Commerce||638||Sunk|
|2 August 1916||Themis||1,047||Captured as a prize|
|2 August 1916||Vera||312||Sunk|
|2 August 1916||Vermland||213||Sunk|
|10 April 1917||Pluto||1,266||Sunk|
|7 May 1917||Martha Maria||176||Sunk|
|7 May 1917||Prins Hendrik De Nederlande||182||Sunk|
|16 May 1917||Friso||171||Sunk|
|17 May 1917||Kilmaho||2,155||Sunk|
|18 May 1917||Adventure||50||Sunk|
|18 May 1917||Primrose||62||Sunk|
|19 May 1917||Askild||2,540||Sunk|
|20 May 1917||Normand||2,097||Sunk|
|11 June 1917||Knight Companion||7,241||Damaged|
- "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.
- Tonnages are in gross register tons
- Rössler 1979, p. 64.
- Gröner 1991, pp. 23-25.
- Helgason, Guðmundur. "WWI U-boat commanders: Max Viebeg (Pour le Mérite)". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
- Helgason, Guðmundur. "WWI U-boat commanders: Hermann Glimpf". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
- Bendert 2000, p. 195.
- Helgason, Guðmundur. "Ships hit by UB 20". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
- Bendert, Harald (2000). Die UB-Boote der Kaiserlichen Marine, 1914-1918. Einsätze, Erfolge, Schicksal (in German). Hamburg: Verlag E.S. Mittler & Sohn GmbH. ISBN 3-8132-0713-7.
- 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.
- Rössler, Eberhard (1979). U-Bootbau bis Ende des 1. Weltkrieges, Konstruktionen für das Ausland und die Jahre 1935 – 1945. Die deutschen U-Boote und ihre Werften (in German). I. Munich: Bernard & Graefe. ISBN 3-7637-5213-7.