SM UC-21

SM UC-21 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 29 August 1915 and was launched on 1 April 1916. She was commissioned into the German Imperial Navy on 12 September 1916 as SM UC-21.[Note 1]

For other ships with the same name, see German submarine U-21.
March 18, 1917, Imperial German Navy U-boat SM UC-21 sinking American tanker steamer Illinois
History
German Empire
NameUC-21
Ordered29 August 1915[1]
BuilderBlohm & Voss, Hamburg[2]
Yard number271[1]
Launched1 April 1916[1]
Commissioned12 September 1916[1]
FateMissing since September 1917[1]
General characteristics [3]
Class and typeGerman Type UC II submarine
Displacement
  • 417 t (410 long tons), surfaced
  • 493 t (485 long tons), submerged
Length
Beam
  • 5.22 m (17 ft 2 in) o/a
  • 3.65 m (12 ft) pressure hull
Draught3.68 m (12 ft 1 in)
Propulsion
Speed
  • 11.6 knots (21.5 km/h; 13.3 mph), surfaced
  • 7.0 knots (13.0 km/h; 8.1 mph), submerged
Range
  • 9,430 nmi (17,460 km; 10,850 mi) at 7 knots (13 km/h; 8.1 mph), surfaced
  • 55 nmi (102 km; 63 mi) at 4 knots (7.4 km/h; 4.6 mph), submerged
Test depth50 m (160 ft)
Complement26
Armament
Notes35-second diving time
Service record[1]
Part of:
  • Flandern Flotilla
  • 14 November 1916 – 30 September 1917
Commanders:
  • Oblt.z.S. Reinhold Saltzwedel[4]
  • 15 September 1916 – 9 June 1917
  • Oblt.z.S. Werner von Zerboni di Sposetti[5]
  • 10 June – 30 September 1917
Operations: 11 patrols
Victories:
  • 95 merchant ships sunk
    (131,844 GRT)
  • 3 auxiliary warships sunk
    (2,219 GRT)
  • 5 merchant ships damaged
    (11,826 GRT)
  • 1 warship damaged
    (778 tons)
  • 1 merchant ship taken as prize
    (148 GRT)

In eleven patrols UC-21 was credited with sinking 98 ships, either by torpedo or by mines laid. They included the British hospital ship Donegal, which UC-21 torpedoed in the English Channel on 17 April 1917, killing 29 already wounded soldiers and 12 crew.[6]

UC-21 disappeared after departing Zeebrugge for the Bay of Biscay on 13 September 1917.[1]

Design

Like all pre-UC-25 German Type UC II submarines, UC-21 had a displacement of 417 tonnes (410 long tons) when at the surface and 493 tonnes (485 long tons) while submerged. She had a total length of 49.35 m (161 ft 11 in), a beam of 5.22 m (17 ft 2 in), and a draught of 3.65 m (12 ft). The submarine was powered by two six-cylinder four-stroke diesel engines each producing 250 metric horsepower (180 kW; 250 shp) (a total of 500 metric horsepower (370 kW; 490 shp)), two electric motors producing 460 metric horsepower (340 kW; 450 shp), and two propeller shafts. She had a dive time of 35 seconds and was capable of operating at a depth of 50 metres (160 ft).[3]

The submarine had a maximum surface speed of 11.6 knots (21.5 km/h; 13.3 mph) and a submerged speed of 7 knots (13 km/h; 8.1 mph). When submerged, she could operate for 55 nautical miles (102 km; 63 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 9,430 nautical miles (17,460 km; 10,850 mi) at 7 knots (13 km/h; 8.1 mph). UC-21 was fitted with six 100 centimetres (39 in) mine tubes, eighteen UC 200 mines, three 50 centimetres (20 in) torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one 8.8 cm (3.5 in) Uk L/30 deck gun. Her complement was twenty-six crew members.[3]

Summary of raiding history
Date Name Nationality Tonnage[Note 2] Fate[7]
28 November 1916 Clematis  United Kingdom 22 Sunk
28 November 1916 Lady of the Lake  United Kingdom 91 Sunk
28 November 1916 Vulcan  United Kingdom 27 Sunk
28 November 1916 HMD Pelagia  Royal Navy 84 Sunk
30 November 1916 Draupner  Norway 1,126 Sunk
30 November 1916 Eggesford  United Kingdom 4,414 Damaged
30 November 1916 Therese  France 165 Sunk
1 December 1916 King Bleddyn  United Kingdom 4,387 Sunk
2 December 1916 Demetrios Inglesis  Greece 2,088 Sunk
2 December 1916 Robinson  France 186 Sunk
2 December 1916 Uribitarte  Spain 1,756 Sunk
3 December 1916 Aiglon  France 280 Sunk
3 December 1916 Louise  France 155 Sunk
3 December 1916 Verdun  France 184 Sunk
4 December 1916 Pallas  Russian Empire 1,202 Sunk
5 December 1916 Nexos  Denmark 1,013 Sunk
6 December 1916 Gerona  Spain 1,328 Sunk
7 December 1916 Avristan  United Kingdom 3,818 Sunk
8 December 1916 HMT Dagon  Royal Navy 250 Sunk
8 December 1916 Falk  Norway 1,379 Sunk
8 December 1916 Marjolaine  France 163 Sunk
8 December 1916 Modum  Norway 2,937 Sunk
17 December 1916 Margaret  United Kingdom 54 Sunk
18 January 1917 HMS Ferret  Royal Navy 778 Damaged
19 January 1917 Joseph Rosalie  France 138 Sunk
19 January 1917 Marietta Di Giorgio  Norway 988 Sunk
19 January 1917 Tremeadow  United Kingdom 3,653 Sunk
20 January 1917 Kisagata Maru No. 3  Japan 2,588 Sunk
20 January 1917 Jotunfjell  Norway 2,492 Damaged
21 January 1917 Victoire  France 290 Damaged
21 January 1917 Leontine  France 124 Sunk
21 January 1917 Saint Pierre  France 127 Sunk
22 January 1917 Bearnais  France 301 Sunk
22 January 1917 Precurseur  France 364 Sunk
22 January 1917 Steinmachos  Greece 1,175 Sunk
24 January 1917 Dan  Denmark 1,869 Sunk
24 January 1917 Gladiateur  France 23 Sunk
24 January 1917 Loire III  France 27 Sunk
24 January 1917 Marie 3  France 25 Sunk
24 January 1917 Quebec  France 3,346 Sunk
24 January 1917 Vega  Denmark 195 Sunk
25 January 1917 Myrdal  Norway 2,631 Sunk
1 February 1917 Sainte Helene  France 2,128 Sunk
10 February 1917 Beechtree  United Kingdom 1,277 Sunk
11 February 1917 Dernes  Norway 738 Sunk
12 February 1917 Nordcap  Norway 332 Sunk
13 February 1917 Progreso  Norway 1,620 Sunk
14 February 1917 Longscar  United Kingdom 2,777 Sunk
14 February 1917 Mar Adriatico  Spain 2,410 Sunk
15 February 1917 Aline  France 30 Sunk
15 February 1917 Marion Dawson  United Kingdom 2,300 Sunk
16 February 1917 Niobe  France 1,319 Sunk
16 February 1917 Pollcrea  United Kingdom 1,209 Damaged
17 February 1917 Cabo  Norway 1,254 Sunk
17 February 1917 Silene  France 171 Sunk
18 February 1917 Triumph  United Kingdom 52 Sunk
19 February 1917 Rutenfjell  Norway 1,844 Sunk
10 March 1917 Asbjørn  Norway 3,459 Sunk
12 March 1917 Alice Charles  France 41 Sunk
12 March 1917 Arethuse  France 40 Sunk
13 March 1917 Girda  Norway 1,824 Sunk
13 March 1917 Vivina  Spain 3,034 Sunk
14 March 1917 Blaamanden  Norway 954 Sunk
14 March 1917 La Marne  France 133 Sunk
15 March 1917 Eugene Robert  France 98 Sunk
15 March 1917 Fleur D’Esperance  France 24 Sunk
15 March 1917 Frimaire  United Kingdom 1,778 Sunk
15 March 1917 Petit Jean  France 21 Sunk
16 March 1917 Anais  France 130 Sunk
16 March 1917 Madeleine Davoust  France 148 Sunk
16 March 1917 Ronald  Norway 3,021 Sunk
18 March 1917 Illinois  United States 5,225 Sunk
17 April 1917 HMHS Donegal  Royal Navy 1,885 Sunk
19 April 1917 Cilurnum  United Kingdom 3,126 Sunk
20 April 1917 Georgios  Greece 3,124 Sunk
21 April 1917 Emile Et Charlotte  France 41 Sunk
21 April 1917 Ville De Dieppe  Norway 1,254 Sunk
22 April 1917 Capenor  United Kingdom 2,536 Sunk
22 April 1917 Percy Birdsall  United States 1,127 Sunk
22 April 1917 Valerie  Norway 2,140 Sunk
24 April 1917 Barnton  United Kingdom 1,858 Sunk
25 April 1917 Baigorry  France 2,161 Sunk
26 April 1917 Boy Denis  United Kingdom 41 Sunk
22 May 1917 Jeune Albert  France 25 Sunk
23 May 1917 Harwood Palmer  United States 2,885 Sunk
23 May 1917 Lesto  United Kingdom 1,940 Sunk
26 May 1917 Aristides  Greece 2,179 Sunk
26 May 1917 Norhaug  Norway 1,245 Sunk
27 May 1917 Efstathios  Greece 3,847 Sunk
28 May 1917 Hiram  Norway 598 Sunk
28 May 1917 Urna  Norway 2,686 Sunk
28 May 1917 Waldemar  Norway 1,267 Sunk
30 May 1917 Sørland  Norway 2,472 Sunk
2 June 1917 Tonawanda  United Kingdom 3,421 Damaged
7 June 1917 Hafnia  Denmark 1,619 Sunk
29 June 1917 Lauwerzee  Netherlands 47 Sunk
4 July 1917 Bestevaer  Netherlands 1,044 Sunk
4 July 1917 Roelfina  Netherlands 148 Captured as prize
11 July 1917 Coquimbo  France 1,759 Sunk
15 August 1917 Phoebe  France 3,956 Sunk
17 August 1917 Pontoporos  Greece 4,049 Sunk
19 August 1917 Therese & Marie  France 1,615 Sunk
31 August 1917 Marques De Mudela  Spain 1,930 Sunk
16 September 1917 Ann J. Trainer  United States 426 Sunk
23 September 1917 St. Dunstan  United Kingdom 730 Sunk

Notes
  1. "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot translates as His Majesty's Submarine.
  2. Merchant ship tonnages are in gross register tons. Military vessels are listed by tons displacement.

References
  1. Helgason, Guðmundur. "WWI U-boats: UC 21". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 22 February 2009.
  2. Tarrant 1989, p. 173
  3. Gröner 1991, pp. 31–32.
  4. Helgason, Guðmundur. "WWI U-boat commanders: Reinhold Saltzwedel (Pour le Mérite)". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 14 February 2015.
  5. Helgason, Guðmundur. "WWI U-boat commanders: Werner von Zerboni di Sposetti". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 14 February 2015.
  6. The War on Hospital Ships, With Narratives of Eye-Witnesses and British and German Diplomatic Correspondence (Second and Revised ed.). New York and London: Harper and Brothers. 1918. p. 16.
  7. Helgason, Guðmundur. "Ships hit by UC 21". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 12 December 2014.

Bibliography
  • Bendert, Harald (2001). Die UC-Boote der Kaiserlichen Marine 1914-1918. Minenkrieg mit U-Booten (in German). Hamburg, Berlin, Bonn: Mittler. ISBN 3-8132-0758-7.
  • 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.
  • Gardiner, Robert, ed. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, MD: Naval Institute Press. ISBN 978-0-87021-907-8. OCLC 12119866.
  • Tarrant, V. E. (1989). The U-Boat Offensive: 1914–1945. Annapolis, MD: Naval Institute Press. ISBN 978-0-87021-764-7. OCLC 20338385.

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