U class submarine (1937)

The U-class submarines, also known as Undine-class, were a group of diesel-electric submarines built for the Royal Navy during the 1930s and saw extensive service throughout World War II. They were relatively small and designed for operations in the North Sea and Mediterranean, where their compact size allowed them to manoeuvre more easily in shallower waters. The U-class submarines were known for their reliability and versatility and were particularly effective in anti-submarine warfare and reconnaissance missions.

The U-class submarines were initially built as small, experimental submarines intended for training but proved to be quite effective operationally. This led to their eventual mass production and their use in active combat. The class went through several iterations, with each group improving upon the design of the previous one.
Specifications (varied slightly by group)
Displacement was Approximately 545 tons surfaced, 740 tons submerged, length About 58 meters (190 feet), powered by a Diesel-electric system, with two diesel engines driving electric motors for a to speed of 11.25 knots surfaced, 9 knots submerged and range of 4,500 nautical miles at 10 knots surfaced. Operational depth was around 60–90 meters, with some later boats capable of deeper dives
As far as armament went they had four 21-inch torpedo tubes in the bow, capable of carrying up to 8 torpedoes. Later versions were fitted with a 3-inch deck gun for additional surface attack capability and certain variants could also carry and deploy mines.

The U-class submarines saw extensive combat service during WWII, particularly in the Mediterranean and North Atlantic, where they conducted a variety of missions, including classic Anti-Submarine Warfare missions against enemy submarines, particularly in the North Sea. They were used for coastal Patrols, performing reconnaissance, patrolling close to enemy coastlines. They were used also for Convoy Protection by patrolling shipping lanes and were used for Special Operations, supporting covert missions and transporting Allied commandos behind enemy lines or VIPs in occupied territories.

HMS Ultimatum, of Group III, Batch 1940

These submarines were particularly effective in the Mediterranean, where their smaller size and shallow draft allowed them to operate close to enemy-held shores and in narrow straits, such as the Strait of Gibraltar. Their contributions were significant, as they helped contain the threat of Axis supply lines and contributed to the overall success of Allied naval operations.
A total of 49 U-class submarines were completed, with 20 being lost in action. Despite their limitations, U-class submarines were seen as a success due to their adaptability and combat effectiveness. Some submarines were transferred to other navies, including the Royal Netherlands Navy, Polish Navy, and Free French Naval Forces.

The U-class set the foundation for later British submarine designs and contributed valuable lessons in diesel-electric submarine warfare. They were succeeded by V-class, a final refinement of the U-class with 34 ordered, 21 built by Vickers under the 1941-42 War Emergency Programmes and the remainder cancelled. The hull was further lengthened to avoid vibrations and “singing propellers” issues whereas the bows were more streamlined. Hull Welding was introduced on thicker steel for the pressure hull, so they could dive down to 300 ft (91 m). None V-class were lost in action and they served for may years in the coldwar or were sold.

Development

The Royal Navy limited itself to 52,700 long tons (53,500 t) of submarines under the London Naval Treaty of 1930, a tonnage limit that favored smaller submarines. This was comounded by numerous reports of earlier large submarines trials showing they were slower to dive, handled poorly and were easy to see and hear. The First World War H-class submarines still around for training in anti-submarine warfare arrived at the end of their career, and this justified replacement in the eyes of the parliament. The Rear-Admiral Submarines, Noel Laurence wanted to simply replaced these with the same type of simple and inexpensive training boats but with enough torpedoes to found usefulness by making short-range patrols in wartime.

In March 1934 he approved the future U class specifications. He called for a “Small, Simple, Submarine, for Anti-Submarine Training (…).” The first three Unity-class boats were eventually ordered once finance was obtained, as HMS Undine, Unity and Ursula on 5 November 1936, from Vickers-Armstrongs, Barrow-in-Furness. The 1926 Hopwood Committee confirmed that names were preferrable to numbers due to crew morale and command and control, but that these names would begin with the same letter in the alphabet. As the plans and detailed blueprints were approved, the new U class would appear as the smallest built since the last war.

Predecessors: The H class

H4 at Brindisi in 1916
The British H-class submarines were Holland 602 types, constructed between 1915 and 1919 and becoming Britain’s largest class of submarine before WW2. They were designed and built in response to minelaying U-Boats and also to perform similar operations in German waters or to hunt German submarines in British waters at large.
They were considered as cramped and many lacked a deck gun but these remained popular amongst submariners. In addition many were sent to the Adriatic but most arrived late and saw little service and further batches saw no service at all, but on the interwar. They still sank U-51 and UB-52, loosing four of their own.
Post-war, many were retained for training purposes, four more lost in accidents in the 1920s. They were obsolete in 1939 and so they served in training and for coastal patrol, mitigating the heavy RN submarine losses in the early years. Two were sunk by the Germans. Canada also built some, which were equipped with Fessenden transducers.

The U class were completely different beasts from the S-class, desptite the fact the latter were also light submersibles. They found their origin in the Shark class, with more made in the 1941 programme, 1942 and 1943 programmes. They had a much longer range and much heavier tonnage of 810-990t for the latter series versus 500/700 tonnes for the U class.

Unity class boats

This class, laid down in 1937 and completed in 1938, were intended as replacements of the ‘H’ class for training and local patrols. They were distinguished by electric drive when surfaced, the main motors being driven from the dieselpowered generators, and were of single-hull type with an operational depth limit of 200ft. The external TT were in the bows and resulted in a bluff form which was not very satisfactory in a seaway.
The UNDINE class (also called “U” class prewar programme was designed at first for a 500t displacemnt, which looked unrealistic, and was later ported to 540t standard. She displaced 630t/730t on “normal” and fully loaded displacement for hull just 191 feet long and to be powered by Paxman-Ricardo diesels coiupled with Vickers electric motors. The former actually developed less than the latter and both surfaced and submerged speeds were about the same between 11-10kts. On trials Undine made 12.45kts surfaced and 8.58kts submerged.

Range was an issue as they only carried 38t of oil, in two 19 tonnes fuel tanks. The initial armament was to be only in the bow and initially of six tubes plus 10 torpedoes including those in the tubes already, leaving 4 spares. It was impossible to fit all six in the pressure hull so two remainder were placed in the outer hull and not reloadable. They were also given a 3 inches/20cwt deck gun from the start. Ursula had only 8 torpedoes to compensate for the weight of the 3in gun, which only she carried, and she could subsequently carry 6 M2 mines as an alternative. The crew amounted to just 27 compared to 48 for an S-class boat (almost double) and to 61 on a T-class (2.5 times larger).

This was due a clever way to manage ergonomics so that some crew members could take on several roles. Still, in their tiny pressure hull they felt extremely cramped. Yet, they appeared in general to be very reliable and agile despite lacking speed and range.
In all three boats were made, UNDINE (Vickers, Armstrong-Barrow, launched 5.10.1937), UNITY (16.2.1938) and URSULA (16.2.1938) the only one to survive the war, discarded in 1950. She was loaned to USSR as B4 from 1944 to 1949 but was allegedly handed over in such a poor state that she was no use to the RN and quickly decommissioned. See later for the historical records of all three.

Design of the class

Hull and general design

The U class were the smallest British submarines built since the D class back in 1908. They displaced 540 long tons (550 t) standard as well as 630 long tons (640 t) full load but surfaced and 730 tons submerged so a 100t buoyancy difference. The weight of a submarine under water needed to always equal its buoyancy, with extra weight compensated for by removing an equal amount of ballast near the keel and it was linked to the density of the water around, from fresh to highly saline.
They were also moderately compact at 191 ft (58 m) long overall for a beam of 16 ft 1 in (4.90 m) and a draught of 15 ft 2 in (4.62 m). To compare the 1908 D-class measured only 50.2 meters long but were beamier at 6.2m, with a 3.5 m draught. Theor conning tower was a simple bathtub style

The U-class boats had a hull of riveted steel, 0.5 inches (13 mm) thick to be able to dive down to 200 feet (61 m) while having the fuel tanks and ballast tanks inside rather than outside the outer hull. Still they were of a partial double hull type. The superstructure and conning tower were built with free-flooding holes as well as storage spaces for cables, anchors and sundry items which was found handy in service. No spare space was left inoccupied. The pressure hull was divided into five bulkheads. The main acess was from the conning tower with an hatch in the torpedo-stowage compartment. However the engine room had drop-down canvas trunks usabled in emergencies. Lessons of the losses of the H class were well retained.

After closing all water-tight doors, the trunks were lowered, connected to the deck. The hatch was opened slightly until air–water pressure was equal. The crew breathing trapped air until escaping. Each crewman had a Davis Submerged Escape Apparatus of nose-clip and mouthpiece connected to the short duration oxygen bag, only there for the pressure balance and rise up. The first man in trunking opened the hatch and left the boat, then the others in turn. Escape from the conning tower was saw two entering the tower and closing the lower hatch, then opening the upper one, flood this before leaving. So at least now there were ways to two escape.
Among interesting equipments were their 200 mm bifocal periscope fitted with low and high magnification and a second 6 inches (150 mm) low magnification periscope for attack only, more discreete. The periscopes could rise 12 ft (3.7 m) but they had a very shallow periscope depth and were easily spotted from the air in the Mediterranean.

Powerplant

These small boats were powered by two 400 hp (300 kW) Paxman diesel-electric engines. Each had an outout of 615 bhp (459 kW). Tis was completed by two Vickers electric motors rated for 825 shp (615 kW). The diesels totalled 1230 bhp, enough for a surface speed of 11.25 knots (20.84 km/h; 12.95 mph) and the two electric motors a submerged speed of 10 knots (19 km/h; 12 mph). The diesels drive directly the propellers via generators also charging the battery composed of 112 cells under the control room/crew accommodation. There was a small hatch for checking these. The propellers were the object of great care, made not to perform best on the surface but rather submerged in order to reduce propeller noise. However destpite of this, these “singing propellers” remained a problem for the class. They had a fuel capacity of 38 long tons, enough for a range of 3,800 nmi (7,000 km; 4,400 mi) at 10 knots (19 km/h; 12 mph) surfaced, 120 nmi (220 km; 140 mi) submerged at 2 knots (3.7 km/h; 2.3 mph). She needed to surface to recharge her battery. In 1944 however some of the wartime U-class tested dummy snorkels solely for ASW training. For quick diving the U class had six ordinary ballast tanks and a special quick-diving “Q tank”. These ballast tanks as well as the hydroplanes and rudder were all hydraulically operated. The forward hydroplanes were placed high on the bow, folding upwards for docking.

Armament

As seen above the small pressure hull was too constrained to fit more than four tubes. Still, specs called for six, so the two extra ones were relocated to the outer hull, and so considered “external”. This was done also for the T class. These four internal bow torpedo tubes could be reloaded underway. Each had a single spare torpedo, the other being already present in tube when loaded at port. The two external tubes were only reloadable in port. They were located in a specific bulged housing forward, creating also a “forecastle” of sorts. Between the internal and external tubes this amounted to ten. The prospect of having two stern tubes was dropped early on due to the lack of space and trimming complications.

Before the war, the first second group boats, HMS Unique, Upholder, Upright and Utmost only had eight torpedoes for weight reasons, and kept their external tubes, but later groups dispensed of these, as bulge generated a large bow wave. Dive stability at periscope depth was problematic and trimming even more sensible. These boats had a shallow 12 ft (3.7 m) persicopic depth, which conducted captains to also to discard the two external tubes. This loss was felt fully justified in operations. Plus when firing these two external tube torpedoes, sudden loss completely break stability and trim, making them to porpoise, break the surface under enemy guns. It was already feared in 1938 and so the Group two boats of the War Supplementary Emergency Programme had the bulg but not the external torpedo tubes already. Group III boats were the first with a straight bow.

21 inches Mark VIII**

The Mark VIII were the first burner-cycle torpedo in service and the most common became the VIII**, with 3,732 fired by September 1944, 56.4% total of those made. It was exported and maintained in service as late ass 1983. A truly fast and dependable model. When correctly used, itw as a sure kill in stark contrast to the US Mark 14. The model suggested below was standard when completed. They were designed betrween 1925 and 1927, and were mass produced for all British subs from the O class. They had a negative buoyancy of 804 lbs. (365 kg).

3 in (76 mm) QF 20 cwt

HMS Ursula and most of the U class built afterwards carried a 3 in (76 mm) Mark V deck gun. It was not protected by the conning tower and unshielded. Ther crew was completely exposed. To compensate for its weight the ten torpedoes carried on paper was reduced to eight. This deck gun was originally a dual purpose or AA model, but the deck gun mount had a more limited elevation than surface ship’s 90°. This gun was shared by the S-class, U-class and V-class submarines. Approximate Barrel Life was 1,250 rounds.

Sensors

The U class had Hydrophones fitted on each side near the bow and facing outwards. There was an extra one on the conning tower, facing aft to cover all angles. Next, an Asdic Type 129 was installed forward of the keel (from 1937). For communication the U class had two wireless aerials plus a jumping aerial on the conning tower usable to detect low frequency signals at periscope depth. The also had a WT mast raised above the water spread for conventional wireless signals.

Group I profile general appearance, HMS Unity.

Rendition of HMS Ursula, Group I

Group II (Umpire class)

(To come)

Group III (Ullswater class)

11 March 1940 batch

23 August 1940 batch

12 July 1941 batch

(More to come)

Succession: V class

(More to come)

Career of the U class

Undine was built by Vickers Amstrong, Barrow-in-Furness. She was laid down on 19 February 1937 and commissioned on 21 August 1938, pennant N48. In 1939 she was part of the 6th Submarine Flotilla. From 26–29 August 1939, she was moved to her patrol bases at Dundee and Blyth. On her fourth war patrol in January 1940 her sonar failed. At 09:40 on the 7th she could not detect incoming German auxiliary minesweepers M-1201, M-1204 and M-1207. She spotted them, tried to sink the leading vessel, but they counter attacked, forced her to dive to 50 feet (15 m). She waited for five minutes with no more depht charging before she raising her periscope and the spotted, attacked, badly damaged by an explosion, abandon ship being ordered and she was scuttled.

Unity was built by Vickers Armstrong, Barrow-in-Furness. She was laid down on 19 February 1937 and was commissioned on 5 October 1938. She was part of the 6th Submarine Flotilla as all three sisters of the Unity clas, Ist group. From 26–29 August 1939 she moved to Dundee and Blyth, patrolling in home waters, North Sea, spotting and attacking but missing U-2. She rescued men from the Dutch fishing vessel Protinus, 25 March 1940. On 11 April 1940 she was spotted by U-5 (another IIa coastal model) commanded by Kapitänleutnant Lehmann. He fired a G7a (T1) torpedo and the latter spotted the bubble trail making a crash dive. U-5 followed and launched another underwater but this time with a G7e (T2) electric torpedo until contact was lost. Both departed their way.
Leaving Blyth on 29 April 1940 for a sortie off Norway, she collided with the Norwegian ship Atle Jarl. Completely rolled over and badly damaged, she had rushing water leaks and sank in five minutes, however all but two survived: Lieutenant John Low and able Seaman Henry Miller remaining behind to lock the flooded control room. They shipmates could escape. The wreck was located again between 48 and 55 m (157 and 180 ft) off the Farne Islands.

Ursula was built by Vickers Armstrong like her sisters, laid down on 19 February 1937, commissioned on 20 December 1938 and entering the 6th Submarine Flotilla. On 9 September 1939, she spotted and attacked U-35 but missed. This was the first RN sub attack of the war. On 14 December she was patrolling of the Elbe estuary when spotting KMS Leipzig, escorted by six destroyers. The light cruise was back to Kiel after already taking a torpedo by HMS Salmon. Ursula dived enough to remain undetected, close the distance, surfaced and launched a close-range attack and then dive again to escape. The cruise was missed but one torpedo hit the escort F9, which sank. Lt.Cdr. G.C. Phillips earned a DSO for this, being promoted. Still in the North Sea, she spotted and sank the German merchant Heddernheim.
Next she was ordered to the Mediterranean and there, sank the Italian auxiliary submarine chaser V 135, German merchants Sainte Marguerite II, Odysseus, badly damaged the Italian merchant Sabbia. However she was almost sunk by the escort and notably the Italian torpedo boat Generale Carlo Montanari. She also sank the trnasport Brook, Tilly L.M. Russ, Vulcania and even U-73. She badly damaged the tanker Beppe, towed to Tripoli and beached.
Lt Cdr Philips in a permission before heading to the Med, contacted a tailor to make him a specific “Ursula” suit which he wore each time he made a successful patrol. He also wanted better suits for its submariners, as the crew was dissatisfied with the conventional oilskins. Her designed himself a special clothing more suitable and navigating officer, Lt. Lakin proposed his one-piece waxed cotton motorcycling suit from Barbour, adapted and made into jacket and trousers with hood. This became soon a sensatio and the company sold it as the standard watch-keeping clothing for RN submarines.
On 26 June 1944 her RN career ended as she was transferred on loan to the Soviet Union, renamed V-4 “Soviet Svanetia” and had a new commander Yaroslav Iosseliani. On 20 October 1944 she operated from Murmansk and sank the German submarine chaser UJ-1219. She was returned in early 1950, scrapped at Grangemouth in May. She was one of the most successful U class subs.

More to come: Group II

HMS Umpire was ordered on 4 September 1939. She was rammed accidentally and sunk by trawler Peter Hendriks, 17 July 1941, North Sea, 22 killed.

HMS Una was laid down on 4 September 1939. She survived the war, sold 11 April 1949 for BU.

HMS Unbeaten was sunk by British bomber on 11 November 1942 in the Bay of Biscay.

HMS Undaunted was sunk on 13 May 1941 off the Libyan coast.

HMS Union was sunk on 20 July 1941 by Italian torpedo boat and aircraft near Panttellaria.

HMS Unique was sunk 24 October 1942 west of Gibraltar.

HMS Upholder was sunk 14 April 1942 by the Italian torpedo boat Pegaso off Tripoli.

HMS Upright survived, sold 19 December 1945, BU March 1946.

HMS Urchin was loaned to the Polish Navy November 1941–1946 as ORP Sokół, then P97 when returned in 1946, BU 1949.

HMS Urge was sunk on 6 May 1942 by Italian torpedo boat Pegaso.

HMS Usk was sunk, probably mined on 3 May 1941 off Cap Bon, Tunisia.

HMS Utmost was sunk on 24 November 1942 by the Italian torpedo boat Groppo west of Sicily.

Group III to come

Read More/Src

Books

Brown, D. K. (2012) [2000]. Nelson to Vanguard (hbk. repr. Seaforth Publishing (Pen & Sword) ed.). Barnsley: Chatham Publishing.
Chesneau, Roger (1992) [1980]. Gardiner, Robert (ed.). Conway’s All the World’s Fighting Ships 1922–46 (3rd ed.). London: Conway Maritime Press.
Colledge, J. J.; Wardlow, B. (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy. Chatham.
McCartney, I. (2006). British Submarines 1939–45. New Vanguard (No. 159). Oxford: Osprey.
Pol, E. van den (1989). “Aspects of Submarines – Part I: Some Notes on Development”. Schip en Werf. Vol. 56.
Walters, Derek (2004). The History of the British ‘U’ Class Submarine. Barnsley: Pen & Sword.
Friedman, N. (2019). British Submarines in two World Wars (e-Pub ed.). Barnsley: Seaforth (Pen & Sword).
Hutchinson, Robert (2001). Submarines, War Beneath The Waves, From 1776 To The Present Day. London: HarperCollins.

Links

rnsubs.co.uk/ u-class.html
on uboat.net/
on web.archive.org/ home.cogeco.ca
wikipedia.org British_U-class_submarine
wikipedia.org/ V-class_submarine
archive.org/ Janessubmarines
navweaps.com 3-in 45 mk1
navweaps.com/ Brit Torps. ww2

Model Kits

all kits on scalemates.com: 1:400, 1:350, 1:700

3D

On cgtrader.com/