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O 21-class submarine

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O 21
Class overview
NameO 21 class
Builders
Operators
Preceded byO 19 class
Succeeded byDolfijn class
Built1937–1942[1]
In commission1940–1959[2]
Completed7
Lost2
Scrapped5
General characteristics [3]
TypeSubmarine
Displacement
  • 990 tons surfaced
  • 1205 tons submerged
Length77.7 m (254 ft 11 in)
Beam6.8 m (22 ft 4 in)
Draught3.95 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
Complement39
Armament

The O 21 class was a class of seven submarines, built for the Royal Netherlands Navy.[2] The boats 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 boats and they entered German service as UD-3, UD-4 and UD-5. The submarines' diving depth was 100 meters (330 ft).

At the start of the Second World War the O 21 class was together with the British U, S and T classes and German Type VII one of the most advanced submarine classes in service at the time.[4]

Design

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The O 21 class submarines were designed by the Dutch engineer G. de Rooy, chief engineer of the Royal Netherlands Navy (RNN) at the time.[5][6] They were similar to the submarines of the O 19 class, except the boats had no minelaying capability.[7] The omission of the minelaying capability resulted in a smaller and more streamlined hull which made it possible to reach a higher surface speed.[8] Visually the boats showed many similarities to the German Type VII submarine.[9] The submarines of the O 21 class had a length of 77.70 metres (254 ft 11 in), a beam of 6.80 metres (22 ft 4 in) and a draught of 3.95 metres (13 ft 0 in).[10] Above water they had a displacement of 990 tons and submerged they had displacement of 1,205 tons.[11] There was enough space aboard for a crew of 39 to 60 persons.[12][13]

One of the requirements the RNN set for the O 21 class was that it had to be able to dive 20 m (66 ft) deeper than the previous class, which was the O 19 class.[14]

Armament

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The primary armament of the O 21-class submarines consisted of eight 53.3-centimetre (21.0 in) torpedo tubes; four were located at the bow, two at the stern and two external amidships.[15] There was room for a total of fourteen torpedoes, with eight being in the torpedo tubes and six for reloads.[16] Besides the eight torpedo tubes the O 21 class was also equipped with an 8.8 cm (3.5 in) deck gun, two single-mounted 40 mm (1.6 in) anti-aircraft guns and a single 12.7 mm (0.50 in) machine gun.[8] The three unfinished boats (O 25, O 26 and O 27) that were captured and later completed by Nazi Germany during the Second World War had besides the eight torpedo tubes, a single 8.8 cm deck gun, and two 20 mm guns.[6]

Propulsion

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The O 21-class submarines were equipped with two seven-cylinder two-stroke Sulzer 7 QD 42/50 diesel engines that each could produce 1,000 shaft horsepower (750 kW) and drive the two screws of the submarine to a maximum surface speed of 19.5 knots (36.1 km/h; 22.4 mph).[17][8] Besides the two diesel engines, the submarines also had two electric motors that each could produce 500 brake horsepower (500 bhp) and two banks of 96 cells batteries with a capacity of 5,350 Ah.[11] This allowed the submarine to operate solely on electric power for five hours.[3] The maximum underwater speed was 9 knots (17 km/h; 10 mph).[13]

Boats

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O 23 returning from patrol in 1946. Dutch newsreel.

The boats were built by three different shipyards. O 21 and O 22 were built by the Koninklijke Maatschappij De Schelde.[18] O 23, O 24, O 26 and O 27 by RDM and O 25 at the Wilton-Fijenoord shipyard.[2]

O 21 class construction data[1]
Name Laid down Launched Commissioned Decommissioned
O 21 13 July 1937 21 October 1939 10 May 1940 (uncompleted) 2 November 1957
O 22 15 September 1938 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 1 March 1942 13 October 1944
3 May 1945 (scuttled)
O 26
Commissioned as:
UD-4 		20 April 1939 23 November 1940 1 March 1941 3 May 1945 (scuttled)
O 27
Commissioned as:
UD-5 		3 August 1939 26 September 1941 1 November 1941
13 July 1945 (Dutch navy) 		14 November 1959

Notes

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Citations

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  1. ^ a b Jalhay (1982), pp. 118-120.
  2. ^ a b c Raven (1988), p. 178.
  3. ^ a b Bosscher and Busssemaker (2007), pp. 86-87.
  4. ^ van den Pol (1989), p. 352.
  5. ^ Jalhay (1982), p. 118.
  6. ^ a b von Münching (1978), p. 38.
  7. ^ van Willigenburg (2010), p. 68.
  8. ^ a b c Gardiner and Chesneau (1980), p. 392.
  9. ^ Bosscher and Busssemaker (2007), p. 26.
  10. ^ Bosscher and Busssemaker (2007), p. 86.
  11. ^ a b Jalhay (1982), p. 127.
  12. ^ Bosscher and Busssemaker (2007), p. 27.
  13. ^ a b von Münching (1978), pp. 37-38.
  14. ^ Gerretse and Wijn (1993), p. 9.
  15. ^ Lenton (1968), p. 43.
  16. ^ van Willigenburg (2010), p. 69.
  17. ^ van den Pol (1990), p. 288.
  18. ^ Mark (1997), pp. 85-86.

References

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  • Bosscher, Ph.M.; Bussemaker, H.O. (2007). Gelouterd door strijd: De Nederlandse Onderzeedienst tot de val van Java, 1942 (in Dutch). Amsterdam: De Bataafsche Leeuw. ISBN 978-90-6707-614-2.
  • Gardiner, Robert; Chesneau, Roger, eds. (1980). Conway's All the World's Fighting Ships 1922–1946. London: Conway Maritime Press. ISBN 0-85177-146-7.
  • 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.
  • Jalhay, P.C. (1982). Nederlandse Onderzeedienst 75 jaar (in Dutch). Bussum: De Boer Maritiem. ISBN 90-228-1864-0.
  • Lenton, H.T. (1968). Royal Netherlands Navy. Navies of the Second World War. London: Macdonald & Co.
  • Mark, Chris (1997). Schepen van de Koninklijke Marine in W.O. II (in Dutch). Alkmaar: De Alk. ISBN 90-6013-522-9.
  • Raven, G.J.A., ed. (1988). De kroon op het anker: 175 jaar Koninklijke Marine (in Dutch). Amsterdam: De Bataafsche Leeuw. ISBN 90-6707-200-1.
  • van den Pol, E. (1989). "Aspects of submarines - Part I: Some notes on development". Schip en Werf. Vol. 56, no. 10. Rotterdam: Wyt & Zonen. pp. 352–358. ISSN 0036-6099.
  • van den Pol, E. (1990). "Aspects of submarines - Part IV: The submarine and the diesel engine". Schip en Werf. Vol. 57, no. 5. Rotterdam: Wyt & Zonen. pp. 285–293. ISSN 0036-6099.
  • van Willigenburg, Henk (2010). Dutch Warships of World War II. Emmen: Lanasta. ISBN 978-90-8616-318-2.
  • von Münching, L.L. (1978). Schepen van de Koninklijke Marine in de Tweede Wereldoorlog (in Dutch). Alkmaar: Alk. ISBN 90-6013-903-8.

Further reading

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  • Jalhay, P.C.; Wijn, J.J.A. (1997). Ik nader ongezien! De onderzeeboten van de Koninklijke Marine. Amsterdam: De Bataafsche Leeuw. ISBN 9067074624.
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