SM UB-21

For other ships with the same name, see German submarine U-21.

History
SM UB-45 a u-boat similar to UB-21
German Empire
Name:	UB-21
Ordered:	30 April 1915^[1]
Builder:	Blohm & Voss, Hamburg^[1]
Yard number:	251^[1]
Launched:	26 September 1915^[1]
Completed:	18 February 1916^[1]
Commissioned:	20 February 1916
Fate:	sunk 1920
General characteristics ^[2]
Class and type:	German Type UB II submarine
Displacement:	263 t (259 long tons) surfaced 292 t (287 long tons) submerged
Length:	36.13 m (118 ft 6 in) o/a 27.13 m (89 ft) pressure hull
Beam:	4.36 m (14 ft 4 in) o/a 3.85 m (13 ft) pressure hull
Draught:	3.70 m (12 ft 2 in)
Propulsion:	1 × propeller shaft 2 × 6-cylinder diesel engine, 284 PS (209 kW; 280 bhp) 2 × electric motor, 280 PS (210 kW; 280 shp)
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 depth:	50 m (160 ft)
Complement:	2 officers, 21 men
Armament:	2 × 50 cm (19.7 in) torpedo tubes 4 × torpedoes (later 6) 1 × 5 cm SK L/40 gun
Notes:	45-second diving time
Service record
Part of:	Imperial German Navy: 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 – 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 – 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 prizes (2,722 GRT)

SM UB-21 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.^{[Note 1]} 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 sank in 1920 in the eastern Solent while en route to be broken up .

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 each producing a total 280 metric horsepower (280 shp; 210 kW), a Siemens-Schuckert electric motor producing 206 kilowatts (276 shp; 280 PS), 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 centimetres (2.0 in) SK L/40 deck machine 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 (GRT)	Fate^[8]
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 a 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 a 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 a 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 a prize
6 June 1917	S.N.A. 2	France	2,294	Sunk
7 June 1917	Sir Francis	United Kingdom	1,991	Sunk
20 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

Notes

↑ "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.

References

1 2 3 4 5 Rössler 1979, p. 64.
1 2 3 Gröner 1991, pp. 23-25.
↑ 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.
↑ 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.
↑ 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.
↑ 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.
↑ Bendert 2000, p. 195.
↑ 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 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.

German Type UB II submarines

UB-18 UB-19 UB-20 UB-21 UB-22 UB-23 UB-24 UB-25 UB-26 UB-27 UB-28 UB-29 UB-30 UB-31 UB-32 UB-33 UB-34 UB-35 UB-36 UB-37 UB-38 UB-39 UB-40 UB-41 UB-42 UB-43 UB-44 UB-45 UB-46 UB-47

Preceded by: Type UB I Followed by: Type UB III List of U-boats of Germany

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