O 21-class submarines

O 21 decommissioning ceremony, Rotterdam. O24 lying alongside. (Collection Jack Sevenich).

Construction details
Name O 21 O 22 O 23 O 24 O 25 O 26 O 27
Dockyard Koninklijke Maatschappij "De Schelde", Vlissingen Koninklijke Maatschappij "De Schelde", Vlissingen Rotterdamsche Droogdok Maatschappij, Rotterdam Rotterdamsche Droogdok Maatschappij, Rotterdam Maatschappij voor Scheeps- en Werktuigbouw "Fijenoord", Rotterdam Maatschappij voor Scheeps- en Werktuigbouw "Fijenoord", Rotterdam Rotterdamsche Droogdok Maatschappij, Rotterdam
Dockyard number 207 208 205 206 667 or 674 209 210
Ordered ? April 12, 1937 June 9, 1937 June 21, 1937 June 28, 1938 June 24, 1938 July 8, 1938
Laid down November 20, 1937 November 20, 1937 October 12, 1937 November 12, 1937 April 10, 1939 April 20, 1939 August 3, 1939
Launched October 21, 1939 January 20, 1940 December 5, 1939 March 18, 1940 May 1, 1940 November 23, 1940 April 26, 1941 or
September 26, 1941
Commissioned May 10, 1940
(uncompleted)		 May 10, 1940
(uncompleted)		 May 13, 1940
(uncompleted)		 May 13, 1940
(uncompleted)		 June 8, 1941
(Kriegsmarine)		 January 28, 1941
(Kriegsmarine)		 January 30, 1942
(Kriegsmarine)

July 13, 1945
(postwar)

Specifications
Displacement 902 tons standard
990 tons surfaced
1205 tons submerged
Crew 39
Dimensions 77.7 m x 6.8 m x 3.95 m
Armament (as designed) 1 x 88 mm / 45 AA Bofors No. 3
2 x 40 mm (2x1) Vickers[1]
1 x 12.7 mm MG
Armament alterations O 21: Also Lewis double (1x2), possibly 7.7 mm. All guns (incl. 1 x 20 mm) removed in the 1950s.
O 22: 1 x 8.8 cm, 1 x 20 mm, possibly 1 x 12.7 mm
O 24 Early 1942 the 40 mm Vickers replaced by 20 mm Oerlikon. But an other source lists that originally 2 x 40mm (1x2) was planned for O 24, but not delivered/installed. One 20 mm was installed instead.
O 25,26,27: While in German hands these boats were fitted with 2 x 20 mm AA (2 x double according to some sources) in place of their intended 40 mm.
O 27: According to other sources O 27 was later during the war fitted with 2 x 20 mm and a 3,7 cm.
Torpedoes 4 x 21" bow
2 x 21" stern
2 x 21" (1x2) external-traversing amidships.[2]
14 torpedoes
Other Equipped with a geruispeiler (listening device) from Atlas Werke (Bremen).
Equipped with snort/schnorchel[3]
Depth 100 m
175 m (crush depth)
[1]: Since I have never seen a photo or drawing that displays the second 40mm (the only one imho is at the aft conning tower deck) the report of 2 x 40mm is probably incorrect. This theory is supported by a source that lists 2 x 40mm (1x2) was planned for O 24, but not delivered/installed. One 20 mm was installed instead.
[2]: After WWII two torpedo tubes (presumably the deck tubes) were removed.
[3]: O 21 and O 22 had their snort systems removed in May 1940. The Royal Navy found the system unnecessary and dangerous.

Propulsion details
Machinery Two 2-stroke 7-cylinder Sulzer reversible diesel engines of 2500 bhp each.
2 x 500 bhp electrical engines
Shafts 2
Bunkerage  
Batteries 2 x 96 cells of each +/- 550 kg. 5350 Ah during 5 hours
Range 10000 nautical miles at 12 knots (surfaced)
28 nautical miles at 8.5 knots (submerged)
Maximum speed 19,5 knots (surfaced)
9 knots (submerged)

Histories
O21 Decommissioned November 2, 1957.
Sold for scrap January 24, 1958.
O22 Mined and sunk November, 1940.
O23 Decommissioned December 1, 1948.
Sold for scrap April, 1949.
O24 Decommissioned February 22, 1954.
Broken up June, 1963.
O25 Decommissioned (Kriegsmarine) October 13, 1944.
Scuttled May 3, 1945.
O26 Scuttled May 3, 1945.
O27 Decommissioned (Kriegsmarine) May, 1945.
Decommissioned (RNLN): November 14, 1959.
Broken up 1961.

This page was first published on the website www.dutchsubmarines.com (no longer existent).

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