O 21-class submarine

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 (255 ft)
Beam6.8 m (22 ft)
Draught3.95 m (13 ft)
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 class and German Type VII class one of the most advanced submarine classes in service at the time.[4]

  1. ^ Cite error: The named reference Jalhay118120 was invoked but never defined (see the help page).
  2. ^ a b Raven (1988), p. 178.
  3. ^ Bosscher and Busssemaker (2007), pp. 86-87.
  4. ^ van den Pol (1989), p. 352.