![]() O 21 | |
Class overview | |
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Name | O 21 class |
Builders | |
Operators | |
Preceded by | O 19 class |
Succeeded by | Dolfijn class |
Built | 1937–1942 [1] |
In commission | 1940–1959 [2] |
Completed | 7 |
Lost | 2 |
Scrapped | 5 |
General characteristics [3] | |
Type | Submarine |
Displacement |
|
Length | 77.7 m (255 ft) |
Beam | 6.8 m (22 ft) |
Draught | 3.95 m (13 ft) |
Propulsion |
|
Speed |
|
Range | |
Complement | 39 |
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 class and German Type VII class one of the most advanced submarine classes in service at the time. [4]
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 class submarine. [9] The submarines of the O 21 class had a length of 77,70 meters, beam of 6,80 meter and a draught of 3,95 meters. [10] Above water they had a displacement of 990 tons and underwater they had displacement of 1205 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 submarine. [14]
The primary armament of the O 21 class submarines consisted of eight 53.3 cm torpedo tubes; 4 were located at the bow, two at the stern and two external amidships. [15] There was room for a total of fourteen torpedoes, with 8 being in the torpedo tubes and six for reloads. [16] Besides the eight torpedo tubes the O 21 class was also equipped with a 8,8 cm deck gun, two (2x1) 40 mm anti-aircraft guns and a single 12.7 mm 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]
The O 21 class submarines were equipped with two 7-cylinder two-stroke Sulzer 7 QD 42/50 diesel engines that each could produce 1,000 shaft horsepower and drive the two screws of the submarine to a maximum surface speed of 19.5 knots. [17] [8] Besides the two diesel engines, the submarines also had two electric motors that each could produce 500 bhp and two banks of 96 cells batteries with a capacity of 5350 Ah. [11] This allowed the submarine to operate solely on electric power for 5 hours. [3] The maximum underwater speed was 9 knots. [13]
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]
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 |
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