O 21-class submarine

The O 21 class was a class of seven submarines, built for the Royal Netherlands Navy. The ships were still incomplete at the start of the German invasion of the Netherlands O 21, O 22, O 23 and O 24 were hastily launched and escaped to the United Kingdom. O 25, O 26 and O 27 were not able to escape and were captured by the German forces. The Kriegsmarine ordered the completion of the ships and they entered German service as UD-3, UD-4 and UD-5. The submarines diving depth was 100 metres (330 ft).

HNLMS O 21
Class overview
Name: O 21 class
Builders:
Operators:
Preceded by: O 19 class
Succeeded by: Dolfijn class
Built: 1937–1940
Completed: 7
General characteristics
Type: Submarine
Displacement:
  • 990 tons surfaced
  • 1205 tons submerged
Length: 77.7 m (254 ft 11 in)
Beam: 6.8 m (22 ft 4 in)
Draught: 3.95 m (13 ft 0 in)
Propulsion:
Speed:
  • 19.5 kn (36.1 km/h; 22.4 mph) surfaced
  • 9 kn (17 km/h; 10 mph) submerged
Range:
  • 10,000 nmi (19,000 km; 12,000 mi) at 12 kn (22 km/h; 14 mph) surfaced
  • 28 nmi (52 km; 32 mi) at 8.5 kn (15.7 km/h; 9.8 mph) submerged
Complement: 39
Armament: 8 × 21 in (530 mm) torpedo tubes (4 bow, 2 stern, 2 traversing amidships )

Design

One of the requirements the Royal Netherlands Navy set for the O 21-class was that it had to be able to dive 20 meters deeper than the previous class, which was the O 19-class submarine.[1]

Construction

The ships were built by three different shipyards. O 21 and O 22 were built by the Koninklijke Maatschappij. O 23, O 24, O 26 and O 27 by R.D.M, Rotterdam and O 25 also in Rotterdam at Fijenoord shipyard.

Name Laid down Launched Commissioned Decommissioned
O 21 20 November 1937 21 October 1939 10 May 1940 (uncompleted) 2 November 1957
O 22 20 November 1937 20 January 1940 10 May 1940 (uncompleted) 8 November 1940
O 23 12 October 1937 5 December 1939 13 May 1940 (uncompleted) 1 December 1948
O 24 12 November 1937 18 March 1940 13 May 1940 (uncompleted) 22 February 1954
O 25
Commissioned as:
UD-3		 10 April 1939 1 May 1940 8 June 1941 13 October 1944
3 May 1945 (scuttled)
O 26
Commissioned as:
UD-4		 20 April 1939 23 November 1940 28 January 1941 3 May 1945 (scuttled)
O 27
Commissioned as:
UD-5		 3 August 1939 1941 30 January 1942
13 July 1945 (Dutch navy)		 14 November 1959

References
  1. Gerretse and Wijn, p. 9

Bibliography
  • Jalhay, P.C.; Wijn, J.J.A. (1997). Ik nader ongezien! De onderzeeboten van de Koninklijke Marine. Amsterdam: De Bataafsche Leeuw. ISBN 9067074624.
  • Gerretse, K.H.L.; Wijn, J.J.A. (1993). Drie-cylinders duiken dieper: de onderzeeboten van de dolfijn-klasse van de Koninklijke Marine. Amsterdam: Van Soeren. ISBN 9068810278.
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