# British U-class submarine

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 O 21 class and German Type VII one of the most advanced submarine classes in service.

## Background

The Royal Navy was limited to no more than 52,700 long tons (53,500 t) 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, HMS Undine, Unity and Ursula 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.

## Design and development

The U-class boats had a hull of riveted steel, half-an-inch thick for dives to 200 ft (61 m), 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 8 in (200 mm) bifocal periscope with high/low magnification for searching and a 6 in (150 mm) low magnification periscope for attack.
The periscopes could rise 12 ft (3.7 m) 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 400 hp (300 kW) Paxman diesel-electric engines generating 615 bhp (459 kW) and electric motors of 825 shp (615 kW) giving a surface speed of 11.25 kn (20.84 km/h; 12.95 mph) and a submerged speed of 10 kn (19 km/h; 12 mph). 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 38 long tons (39 t) giving a range of 3,800 nmi (7,000 km; 4,400 mi) at 10 kn (19 km/h; 12 mph) on the surface and 120 nmi (220 km; 140 mi) at 2 kn (3.7 km/h; 2.3 mph) 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 3 in (76 mm) 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, HMS Unique, HMS Upholder, HMS Upright and HMS Utmost 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 12 ft (3.7 m) 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.

## Unity-class boats

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.
Unity-class boats [Data from Chesneau (1992), Colledge and Wardlow (2006)] :
| Name/ No. | Launched | Notes |
| HMS Undine | 5 October 1937 | Sunk by German minesweepers off Heligoland, 7 January 1940 |
| HMS Unity | 16 February 1938 | Sunk in collision with SS Alte Jarl 29 April 1940 |
| HMS Ursula | 16 February 1938 | Loaned to Soviet Navy 1944–1949, sold 1950, broken up |

## Group II boats

The experience gained with the U-class boats was incorporated into the Group two boats of the War Supplementary Emergency Programme, consisting of twelve submarines, of a similar design to the original three. The external torpedo tubes were omitted and the boats had a redesigned stern to reduce cavitation and on some of the boats a new bow shape was introduced to reduce the bow wave; the hydroplanes were enlarged for better submerged handling. The First World War-vintage 12-pounder was retained but replaced on Unbeaten and Unique by a 3-inch gun. The boats ordered in 1940 and 1941 carried the 3-inch gun and more fuel. Most of the boats were built by Vickers at Barrow-in-Furness. MI5 investigated the loss of Vandal and Untamed during training operations but the report was kept confidential.
In June 1940, the Admiralty had stopped naming submarines and used their pennant numbers. 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 because the big increase in the number of destroyers, which usually had names with the same initial letter. Numbering submarines had been the practice in the First World War but because of Churchill's views, the Admiralty decided that it was better to be right than consistent and naming was resumed. After a delay, Churchill was told that it was difficult to find sufficient names beginning with U and that the remainder 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 ORP Sokół and sank 55,000 long tons (56,000 t) 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 119,000 long tons (121,000 t) 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 Conte Rosso on 25 May 1941. Losses in this group were high, only three out of the twelve survived the war.

### 4 September 1939 batch

Group II boats [Data from Walters (2004), Colledge and Wardlow (2006)] :
| Name/ No. | Ordered | Notes |
| HMS Umpire | 4 September 1939 | Rammed accidentally and sunk by trawler Peter Hendriks, 17 July 1941, North Sea, 22 killed |
| HMS Una | 4 September 1939 | Sold 11 April 1949, broken up |
| HMS Unbeaten | 4 September 1939 | Sunk by British bomber, 11 November 1942, Bay of Biscay |
| HMS Undaunted | 4 September 1939 | Sunk 13 May 1941 off Libyan coast |
| HMS Union | 4 September 1939 | Sunk 20 July 1941 by Italian torpedo boat and aircraft near Panttellaria |
| HMS Unique | 4 September 1939 | Sunk 24 October 1942 west of Gibraltar |
| HMS Upholder | 4 September 1939 | Sunk 14 April 1942 by the Italian torpedo boat Pegaso off Tripoli |
| HMS Upright | 4 September 1939 | Sold 19 December 1945, broken up March 1946 |
| HMS Urchin | 4 September 1939 | Loaned to the Polish Navy November 1941–1946 as ORP Sokół; named P97 in 1946, broken up 1949 |
| HMS Urge | 4 September 1939 | Sunk 6 May 1942 by Italian torpedo boat Pegaso |
| HMS Usk | 4 September 1939 | Sunk, thought mined, 3 May 1941 off Cap Bon, Tunisia |
| HMS Utmost | 4 September 1939 | Sunk 24 November 1942 by Italian torpedo boat Groppo west of Sicily |

## Group III boats

The third group formed the largest group of U-class submarines, comprising 34 vessels ordered in three batches. Losses continued to be high. In June 1940 the decision was taken, in view of the anticipated high number of submarines to be ordered, to drop the practice of naming submarines and the vessels were called P31 to P39, P41 to P49. At the end of 1942 Winston Churchill ordered that all submarines were to receive names but eight of the U-class boats were lost before they could receive them, whilst on operations with the Royal Navy.

### 11 March 1940 batch

Group III boats [Data from Walters (2004), Colledge and Wardlow (2006)] :
| Name/ No. | Ordered | Notes |
| HMS Ullswater | 11 March 1940 | Renamed Uproar April 1943, sold 13 February 1946, broken up |
| HMS P32 | 11 March 1940 | Mined off Tripoli 18 August 1941 before named |
| HMS P33 | 11 March 1940 | Presumed lost to a mine off Tripoli, 20 August 1941, before named |
| HMS Ultimatum | 11 March 1940 | Sold 23 December 1949 broken up |
| HMS Umbra | 11 March 1940 | Sold 9 July 1946, broken up |
| HMS P36 | 11 March 1940 | Delivered agents to France late 1941, transferred to Mediterranean, lost before naming |
| HMS Unbending | 11 March 1940 | Sold 23 December 1949, broken up 1950 |
| HMS P38 | 11 March 1940 | Sunk by Italian ships Circe and Usodimare off Tunisia 25 February 1942 before named |
| HMS P39 | 11 March 1940 | Sunk during air attack on Malta 26 March 1942 before named, raised June 1943, broken up 1954 |
| HMS P41 | 11 March 1940 | To Royal Norwegian Navy as HNoMS Uredd; mined, all 39 men lost, after 5 February 1943. |

### 23 August 1940 batch

Group III boats [Data from Walters (2004), Colledge and Wardlow (2006)] :
| Name/ No. | Ordered | Notes |
| HMS Unbroken | 23 August 1940 | Loaned to Soviet Navy 1944–1949 as V 2, returned 1949, broken up 9 May 1950 |
| HMS Unison | 23 August 1940 | Loaned to Soviet Navy 1944–1949 as V 3, returned 1949, scrapped in May 1950 |
| HMS United | 23 August 1940 | Broken up 12 February 1946 |
| HMS Unrivalled | 23 August 1940 | Arrived 22 January 1946 for breaking up |
| HMS Unruffled | 23 August 1940 | Broken up January 1946 |
| HMS P47 | 23 August 1940 | Loaned to the Royal Netherlands Navy as HNLMS Dolfijn |
| HMS P48 | 23 August 1940 | Sunk in Gulf of Tunis by Italian ship Ardente 25 December 1942 before named |
| HMS Unruly | 23 August 1940 | Arrived February 1946 for breaking up |
| HMS Unseen | 23 August 1940 | Arrived 11 May 1949 for breaking up |
| HMS P52 | 23 August 1940 | Loaned to the Polish Navy as ORP Dzik and post-war to the Royal Danish Navy as HDMS U 1 Springeren |
| HMS Ultor | 23 August 1940 | Sold 22 January 1946, broken up |
| HMS Unshaken | 23 August 1940 | Broken up March 1946 |

### 12 July 1941 batch

Group III boats [Data from Walters (2004), Colledge and Wardlow (2006)] :
| Name/ No. | Ordered | Notes |
| HMS Unsparing | 12 July 1941 | Sold 14 February 1946, broken up |
| HMS Usurper | 12 July 1941 | Sunk 4 October 1943 by German ship UJ2208 or by mine in the Gulf of Genoa |
| HMS Universal | 12 July 1941 | sold February 1946 |
| HMS Untamed | 12 July 1941 | Foundered 30 May 1943, raised 5 July, renamed HMS Vitality, sold 1946 for breaking up |
| HMS Untiring | 12 July 1941 | Loaned 1945 to 1953 to the Royal Hellenic Navy as HS Xifias, sunk 1957 as an Asdic target |
| HMS Varangian | 12 July 1941 | sold June 1949, broken up |
| HMS Uther | 12 July 1941 | Sold February 1950, arrived 20 February 1950 for breaking up |
| HMS Unswerving | 12 July 1941 | Arrived 10 July 1949 for breaking up |
| HMS Vandal | 12 July 1941 | Wrecked 24 February 1943, Firth of Clyde |
| HMS Upstart | 12 July 1941 | Loaned post-war to the Royal Hellenic Navy as HS Amphitriti |
| HMS Varne I | 12 July 1941 | Loaned to the Royal Norwegian Navy as HNoMS Ula |
| HMS Vortex | 12 July 1941 | Loaned post-war to the Royal Danish Navy as HDMS U 3 Sælen |
| HMS Vox I | 12 July 1941 | Loaned to the Free French Naval Forces as Curie |
| HMS Vulpine | 12 July 1941 | Loaned post-war to the Royal Danish Navy as HDMS U 2 Støren |

## V-class submarine

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 300 ft (91 m). None of the V-class boats were lost and some did not see service. The boats were named HMS Upshot, HMS Urtica, Vagabond, Variance, HMS Venturer, HMS Vigorous, Viking, HMS Vampire, Varne II, Veldt, HMS Vineyard, Virtue, Visigoth, HMS Vivid, Voracious, Votary, Vox II, HMS Virulent, Volatile, Vortex and Vulpine.