The British U-class submarines (officially "War Emergency 1940 and 1941 programmes, short hull") were a class of 49 small submarines built just before and during the Second World War. The class is sometimes known as the Undine class, after the first submarine built. A further development was the British V-class submarine of 1942.
At the start of the Second World War the U class was, with the British S and T-class submarines, the Dutch and German Type VII one of the most advanced submarine classes in service.
The Royal Navy was limited to no more than of submarines by the London Naval Treaty of 1930. The tonnage limit led to proposals for smaller submarines which was also prompted by trials with larger submarines demonstrating that they were easier to find and lacked manoeuvrability. By coincidence the First World War-vintage H-class submarines used for training in anti-submarine warfare were reaching the end of their useful service. The Rear-Admiral Submarines, Noel Laurence, wanted a class of small, inexpensive boats for training, armed with torpedoes for short-range patrols.
In March 1934 he approved a specification for a "Small, Simple, Submarine, for Anti-Submarine Training etc". The three Unity-class boats,, and were ordered on 5 November 1936 from Vickers-Armstrongs, to be built at their Naval Construction Yard in Barrow-in-Furness. According to the recommendation of the Hopwood Committee of 1926 the boats had names beginning with the same letter in the alphabet. The new boats were the smallest built since the First World War.
The U-class boats had a hull of riveted steel, half-an-inch thick for dives to, with the fuel tanks and ballast tanks on the inside. The superstructure and conning tower were built with free-flooding holes and storage for cables, anchors and sundry items. The hull was divided by five bulkheads with access from the conning tower; hatches in the torpedo-stowage compartment and in the engine room had drop-down canvas trunks for emergencies. The boats had an bifocal periscope with high/low magnification for searching and a low magnification periscope for attack.
The periscopes could rise but such a shallow periscope depth could allow the boat to be seen from the air. Hydrophones were fitted, one on each side near the bows facing outwards and one on the conning tower facing aft. Asdic Type 129 was installed forward of the keel from 1937 and two wireless aerials were carried, a jumping aerial on the conning tower for very low frequency signals at periscope depth and a WT mast which could be raised above the water spread the second aerial for conventional wireless signalling.
The boats had six ordinary ballast tanks and a quick-diving, "Q tank", the ballast tanks, hydroplanes and the rudder being hydraulically operated; the forward hydroplanes were mounted high on the hull and folded upwards for docking. The submarines had two Paxman diesel-electric engines generating and electric motors of giving a surface speed of and a submerged speed of . The diesels were linked to the propellers by two generators which kept charged the battery of 112 cells under the control room and crew accommodation. Submarine propellers had been designed to perform best on the surface until the Unity class which was the first submarine design with propellers giving their best performance submerged to reduce propeller noise but "singing propellers" were a constant problem for the class.
The boats had a fuel capacity of giving a range of at on the surface and at submerged; battery recharging required the submarine to surface; in 1944 dummy snorkels were fitted to some boats for anti-submarine warfare training During construction the four internal bow torpedo tubes were supplemented by two external tubes in a bulged housing, four reloads being carried for the internal tubes. Ursula carried a gun but had no hatch for the gun crew, who had to use the conning tower; to compensate for the weight of the gun only eight torpedoes were carried. Just before the war, a second group of twelve vessels were ordered,,, and with the external tubes, the others without, because the bulge at the bow generated a large bow wave. Depth keeping was more difficult at periscope depth, a rather shallow which was more of a disadvantage than the six-torpedo salvo justified. The sudden loss of weight in the bows when the torpedoes were loosed in salvo made the boat porpoise and break the surface.
The three Unity-class boats entered service in the latter half of 1938. Designed as training vessels, they were effective enough to persuade the Admiralty to build more and to improve their offensive capacity. Ursula was launched on 16 February 1938, was loaned to the Soviet Navy from 1944 to 1949 as V 4 and sold in May 1950 and broken up. Unity was launched on 16 February 1938 and sunk on 29 April 1940 in a collision with SS Atle Jarl off the Tyne. Undine was launched on 5 October 1937 and sunk by German minesweepers on 7 January 1940 off Heligoland.
| Name/ No. | Launched | Notes |
|---|---|---|
| 5 October 1937 | Sunk by German minesweepers off Heligoland, 7 January 1940 | |
| 16 February 1938 | Sunk in collision with SS Alte Jarl 29 April 1940 | |
| 16 February 1938 | Loaned to Soviet Navy 1944–1949, sold 1950, broken up | |
In June 1940 the Admiralty had stopped naming submarines and known them by their pennant numbers but on 4 November 1942 the Prime Minister, Winston Churchill, questioned the policy. The First Lord of the Admiralty replied that naming had been dropped to avoid confusion with the big increase in the number of destroyers, which usually had names with the same initial letter. Numbering submarines had been the practise in the First World War but that because of Churchill's views, the Admiralty had decided that it was better to be right than consistent and that naming was to be resumed. After a delay Churchill was told that it was difficult to find sufficient names beginning with U and that the surplus were being named with words beginning with "V" and a list was sent to Churchill on 27 December 1942. Submarines lost before they could receive names kept their pennant number.
The group included submarines that became well-known; Urchin was transferred to the Polish Navy as and sank of Axis shipping. In the 16-month operational career of Upholder (Lieutenant-Commander Malcolm Wanklyn) in the Mediterranean, Upholder carried out 24 patrols and sank around of Axis ships, consisting of three U-boats, a destroyer, 15 merchant ships with possibly a cruiser and another destroyer also sunk before being lost in April 1942. Wanklyn was awarded the Victoria Cross for attacking a well-defended convoy and sinking the Italian liner on 25 May 1941. Losses in this group were high, only three out of the twelve survived the war.
| Name/ No. | Ordered | Notes |
|---|---|---|
| 4 September 1939 | Rammed accidentally and sunk by trawler Peter Hendriks, 17 July 1941, North Sea, 22 killed | |
| 4 September 1939 | Sold 11 April 1949, broken up | |
| 4 September 1939 | Sunk by British bomber, 11 November 1942, Bay of Biscay | |
| 4 September 1939 | Sunk 13 May 1941 off Libyan coast | |
| 4 September 1939 | Sunk 20 July 1941 by Italian torpedo boat and aircraft near Panttellaria | |
| 4 September 1939 | Sunk 24 October 1942 west of Gibraltar | |
| 4 September 1939 | Sunk 14 April 1942 by the Italian torpedo boat Pegaso off Tripoli | |
| 4 September 1939 | Sold 19 December 1945, broken up March 1946 | |
| 4 September 1939 | Loaned to the Polish Navy November 1941–1946 as ; named P97 in 1946, broken up 1949 | |
| 4 September 1939 | Sunk 6 May 1942 by Italian torpedo boat Pegaso | |
| 4 September 1939 | Sunk, thought mined, 3 May 1941 off Cap Bon, Tunisia | |
| 4 September 1939 | Sunk 24 November 1942 by Italian torpedo boat Groppo west of Sicily | |
| Name/ No. | Ordered | Notes |
|---|---|---|
| 11 March 1940 | Renamed Uproar April 1943, sold 13 February 1946, broken up | |
| 11 March 1940 | Mined off Tripoli 18 August 1941 before named | |
| 11 March 1940 | Presumed lost to a mine off Tripoli, 20 August 1941, before named | |
| 11 March 1940 | Sold 23 December 1949 broken up | |
| 11 March 1940 | Sold 9 July 1946, broken up | |
| 11 March 1940 | Delivered agents to France late 1941, transferred to Mediterranean, lost before naming | |
| 11 March 1940 | Sold 23 December 1949, broken up 1950 | |
| 11 March 1940 | Sunk by Italian ships Circe and Usodimare off Tunisia 25 February 1942 before named | |
| 11 March 1940 | Sunk during air attack on Malta 26 March 1942 before named, raised June 1943, broken up 1954 | |
| 11 March 1940 | To Royal Norwegian Navy as ; mined, all 39 men lost, after 5 February 1943. | |
| Name/ No. | Ordered | Notes |
|---|---|---|
| 23 August 1940 | Loaned to Soviet Navy 1944–1949 as V 2, returned 9 May 1950, broken up | |
| 23 August 1940 | Loaned to Soviet Navy as V 3 | |
| 23 August 1940 | Broken up 12 February 1946 | |
| 23 August 1940 | Arrived 22 January 1946 for breaking up | |
| 23 August 1940 | Broken up January 1946 | |
| 23 August 1940 | Loaned to the Royal Netherlands Navy as | |
| 23 August 1940 | Sunk in Gulf of Tunis by Italian ship Ardente 25 December 1942 before named | |
| 23 August 1940 | Arrived February 1946 for breaking up | |
| 23 August 1940 | Arrived 11 May 1949 for breaking up | |
| 23 August 1940 | Loaned to the Polish Navy as and post-war to the Royal Danish Navy as | |
| 23 August 1940 | Sold 22 January 1946, broken up | |
| 23 August 1940 | Broken up March 1946 | |
| Name/ No. | Ordered | Notes |
|---|---|---|
| 12 July 1941 | Sold 14 February 1946, broken up | |
| 12 July 1941 | Sunk 4 October 1943 by German ship UJ2208 or by mine in the Gulf of Genoa | |
| 12 July 1941 | sold February 1946 | |
| 12 July 1941 | Foundered 30 May 1943, raised 5 July, renamed HMS Vitality, sold 1946 for breaking up | |
| 12 July 1941 | Loaned 1945 to 1953 to the Royal Hellenic Navy as, sunk 1957 as an Asdic target | |
| 12 July 1941 | sold June 1949, broken up | |
| 12 July 1941 | Sold February 1950, arrived 20 February 1950 for breaking up | |
| 12 July 1941 | Arrived 10 July 1949 for breaking up | |
| 12 July 1941 | Wrecked 24 February 1943, Firth of Clyde | |
| 12 July 1941 | Loaned post-war to the Royal Hellenic Navy as | |
| 12 July 1941 | Loaned to the Royal Norwegian Navy as | |
| 12 July 1941 | Loaned post-war to the Royal Danish Navy as | |
| 12 July 1941 | Loaned to the Free French Naval Forces as Curie | |
| 12 July 1941 | Loaned post-war to the Royal Danish Navy as | |
The V-class boats were the final refinement of the U-class submarines, 34 were ordered and 21 were built by Vickers for the War Emergency Programmes of 1941 and 1942, the rest being cancelled. The hull was further lengthened to try to eliminate the singing propellers and the bows were more streamlined. Welding of the hull frames was introduced to use thicker steel for the pressure hull, giving a diving depth of . None of the V-class boats were lost and some did not see service. The boats were named,, Vagabond, Variance,,, Viking,, Varne II, Veldt,, Virtue, Visigoth,, Voracious, Votary, Vox II,, Volatile, Vortex and Vulpine.
The Complete Record of all Fighting Ships of the Royal Navy
. 2006 . 1969 . Chatham . London . 2nd rev. . 978-1-86176-281-8.