SM UB-21

SM UB-21[Note 1] 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 20 February 1916 as SM UB-21. The submarine sank 33 ships in 26 patrols for a total of 36,764 gross register tons (GRT).[7] Surrendered to Britain in accordance with the requirements of the Armistice with Germany, UB-21 was sunk as a target by HMS Terror in the Solent on 30 September 1920; the wreck was sold in 1970 and most had been cleared by 1998, although some remnants survive.[8]

For other ships with the same name, see German submarine U-21.
SM UB-45, a U-boat similar to UB-21
History
German Empire
NameUB-21
Ordered30 April 1915[1]
BuilderBlohm & Voss, Hamburg[1]
Yard number251[1]
Launched26 September 1915[1]
Completed18 February 1916[1]
Commissioned20 February 1916
FateSunk as target 30 September 1920
General characteristics [2]
Class and typeGerman Type UB II submarine
Displacement
  • 263 t (259 long tons) surfaced
  • 292 t (287 long tons) submerged
Length
Beam
  • 4.36 m (14 ft 4 in) o/a
  • 3.85 m (13 ft) pressure hull
Draught3.70 m (12 ft 2 in)
Propulsion
Speed
  • 9.15 knots (16.95 km/h; 10.53 mph) surfaced
  • 5.81 knots (10.76 km/h; 6.69 mph) submerged
Range
  • 6,450 nmi (11,950 km; 7,420 mi) at 5 knots (9.3 km/h; 5.8 mph) surfaced
  • 45 nmi (83 km; 52 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth50 m (160 ft)
Complement2 officers, 21 men
Armament
Notes45-second diving time
Service record
Part of:
  • I Flotilla
  • 14 April 1916 – 1 February 1917
  • II Flotilla
  • 1 February – 10 September 1917
  • V Flotilla
  • 10 September 1917 – 29 April 1918
  • I Flotilla
  • 29 April – 7 October 1918
  • Training Flotilla
  • 7 October – 11 November 1918
Commanders:
  • Kptlt. Ernst Hashagen[3]
  • 20 February – 26 November 1916
  • Oblt.z.S. Franz Walther[4]
  • 27 November 1916 – 9 September 1917
  • Oblt.z.S. Walter Scheffler[5]
  • 10 September 1917 – 28 April 1918
  • Oblt.z.S. Bruno Mahn[6]
  • 29 April – 7 October 1918
Operations: 26 patrols
Victories:
  • 33 merchant ships sunk
    (36,764 GRT)
  • 1 merchant ship damaged
    (3,734 GRT)
  • 4 merchant ships taken as prize
    (2,722 GRT)

Design

A German Type UB II submarine, UB-21 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 producing a total of 280 metric horsepower (280 shp; 210 kW), two Siemens-Schuckert electric motors 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).[2]

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-21 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-one crew members and two officers and a 45-second dive time.[2]

Summary of raiding history
Date Name Nationality Tonnage[Note 2] Fate[9]
5 May 1916 Harald  Sweden 275 Sunk
20 October 1916 Lekna  Sweden 204 Sunk
20 October 1916 Randi  Norway 467 Sunk
20 October 1916 Svartvik  Sweden 322 Sunk
21 October 1916 Fritzöe  Norway 641 Captured as prize
21 October 1916 Grönhaug  Norway 667 Sunk
22 October 1916 London  Denmark 184 Sunk
22 October 1916 Thor  Norway 372 Sunk
3 November 1916 Pluto  Norway 1,148 Captured as prize
16 February 1917 Lady Ann  United Kingdom 1,016 Sunk
17 February 1917 Excel  United Kingdom 157 Sunk
22 February 1917 John Miles  United Kingdom 687 Sunk
29 March 1917 Bywell  United Kingdom 1,522 Sunk
31 March 1917 Norden  Norway 776 Captured as prize
29 April 1917 Victoria  United Kingdom 1,620 Sunk
2 May 1917 Rikard Noordrak  Norway 1,123 Sunk
5 May 1917 Edith Cavell  United Kingdom 20 Sunk
6 May 1917 Harold  Sweden 1,679 Sunk
8 May 1917 Batavier II  Netherlands 157 Captured as prize
6 June 1917 S.N.A. 2  France 2,294 Sunk
7 June 1917 Sir Francis  United Kingdom 1,991 Sunk
21 July 1917 Trelyon  United Kingdom 3,099 Sunk
22 July 1917 Glow  United Kingdom 1,141 Sunk
23 July 1917 Vanland  Sweden 1,285 Sunk
24 August 1917 Springhill  United Kingdom 1,507 Sunk
18 October 1917 Amsteldam  United Kingdom 1,233 Sunk
19 October 1917 Gemma  United Kingdom 1,385 Sunk
23 November 1917 Ocean  United Kingdom 1,442 Sunk
29 December 1917 Inverness  United Kingdom 3,734 Damaged
29 December 1917 Patria  Russian Empire 838 Sunk
30 December 1917 Hercules  United Kingdom 1,295 Sunk
25 March 1918 Hercules  United Kingdom 1,095 Sunk
8 May 1918 Constantia  United Kingdom 772 Sunk
10 May 1918 Anboto Mendi  Spain 2,114 Sunk
11 May 1918 Gothia  Sweden 1,826 Sunk
12 May 1918 Haslingden  United Kingdom 1,934 Sunk
4 July 1918 Mentor  Norway 539 Sunk
26 September 1918 Paul  Belgium 659 Sunk

References

Notes
  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
  1. Rössler 1979, p. 64.
  2. Gröner 1991, pp. 23–25.
  3. Helgason, Guðmundur. "WWI U-boat commanders: Ernst Hashagen (Royal House Order of Hohenzollern)". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
  4. Helgason, Guðmundur. "WWI U-boat commanders: Franz Walther". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
  5. Helgason, Guðmundur. "WWI U-boat commanders: Walter Scheffler". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
  6. Helgason, Guðmundur. "WWI U-boat commanders: Bruno Mahn". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.
  7. Bendert 2000, p. 195.
  8. Dodson, Aidan; Cant, Serena (2020). Spoils of War: the fate of enemy fleets after the two World Wars. Barnsley: Seaforth. pp. 49, 129. ISBN 978-1-5267-4198-1.
  9. Helgason, Guðmundur. "Ships hit by UB-21". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 January 2015.

Bibliography
  • 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. Vol. 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. ISBN 3-7637-5213-7. {{cite book}}: |work= ignored (help)

50°44′28″N 1°01′6″W

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