The German Type II U-boat was designed as a coastal submarine. It was designed by the Dutch NV Ingenieurskantoor voor Scheepsbouw den Haag, a dummy company set up by Germany after World War I in order to maintain and develop German submarine technology and to circumvent the limitations set by the Treaty of Versailles.
The submarine was built in Finland by the Crichton-Vulcan shipyard in Turku. The vessel, launched on May 10, 1933, was named the Vesikko and served as a prototype of German Type II submarines, which were being built in four sub-types:
Type II A
Type A coastal submarines series consisted of only six units. Their dimensions coincided with those of the Finnish Vesikko. Their length was 40.9 m, beam 4 m and surfaced displacement 254 tonnes (303 tonnes submerged). Running of the surface they were powered by two 350 hp MWM RS 127 S Diesel engines. Underwater, they operated on two 180 hp SSW PG VV 322/36 electric motors. The maximum surfaced speed was 13 knots and almost 7 knots while submerged. Maximum range at 8 knots surfaced was 1,600 nautical miles. Maximum depth was 100 metres. Type A was armed with three 533 mm bow torpedo tubes and carried five spare torpedoes. Additionally, it was armed with 20 mm anti-aircraft gun.
Type II B
Type B was manufactured in the largest number of all Type II submarines. Until the second half of 1936, Germaniawerft AG and Deutsche Werke AG in Kiel built 18 Type II B submarines, which were designated U-7 to U-24. In March 1940, the Flander Werke AG in Lübeck, completed two more units – U-120 and U-121. Initially, they were supposed to be sold, but in the end the were commissioned in the Kriegsmarine.
Type II B was longer – 42.7 m. That allowed for installation of an additional fuel tank, which increased its range at 8 knots from 1600 to 3100 NM. Due to hull modifications crash diving time was reduced to 25 seconds.
Type II C
Third series of Type II submarines was built between 1937 to 1940. The length of the boat was further increased by approximately 1 metre, which allowed for accommodation of a separate radio room. Fuel tanks were enlarged, which increased the boat’s range to 3,800 NM (Type A had a range of only 1,600 NM). Type C was also equipped with the second periscope and had more powerful 205 hp electric motors.
Type II D
Already in the second half of September 1939, the Kriegsmarine command. Placed an order at Deutsche Werke AG shipyard for the fourth series of Type II coastal submarines. It comprised of 16 units.
Type II D hull was further lengthened, it was over three metres longer than that of Type II A submarines. Surfaced displacement was increased to 314 tonnes. The enlarged fuel tanks stored over 38 tons of oil. Thus, the range at 8 knots was increased to 5,650 NM.
The propulsion system was also modified. Both propellers were equipped with Kort nozzles. These shrouds, shaped like a foil, improved efficiency of the propellers. The shape of the conning tower was also modified, the bridge was larger and a breakwater was added – metal sheet apron between the conning tower’s top and the deck.
As a coastal submarine, Type II successfully served in the North and the Baltic Sea, which were its areas of operation. Manoeuvrable, quite fast, operating close to its bases, it needed neither large fuel tanks nor numerous spare torpedoes. In hands of a well-trained crew it could be considered a serious threat. Even, in the Atlantic, where the crews complained about cramped rooms, rolling, limited provisions storage and only five torpedoes, the boats nicknamed “Dugout Canoes” achieved successes.
Type II submarines were mainly used for training. In that role the small U-boats performed well, training thousands of submariners before they entered combat. “Dugout Canoes” trained not only future seamen-veterans, but also aces of the U-Boot-Waffe. Otto Kretschmer, Wolfgang Lüth, Erich Topp, Heinrich Lehmann-Willenbrock – were the Top 10 officers, who sank their first merchantmen commanding Type II boats. Heinrich Liege, Viktor Schütze, Herbert Schulze commanded “Dugout Canoes” before the outbreak of World War II. The remaining ones, like Lassem, Prien and Merten either served their seamanship or trained on those small U-boats. Type II submarines were also used as test platforms for new technologies and armament such as “Alberich” coating, “Schnorkel” or “Ursel” underwater rocket project.
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