| Class overview | |
|---|---|
| Operators |  Imperial German Navy |
| Preceded by | U 1 |
| Succeeded by | Type U 3 |
| Completed | 1 |
| History | |
 German Empire | |
| Name | U–2 |
| Ordered | 4 March 1906 |
| Builder | Kaiserliche Werft Danzig |
| Cost | 1,548,000Goldmark |
| Yard number | 1 |
| Launched | 18 June 1908 |
| Commissioned | 18 July 1908 |
| Decommissioned | 19 February 1919 |
| Fate | Sold toStinnes 3 February 1920 forshipbreaking |
| General characteristics[1] | |
| Class & type | UniqueU-boat |
| Displacement | |
| Length |
|
| Beam | 5.50 m (18 ft 1 in) |
| Draught | 3.05 m (10 ft) |
| Installed power | |
| Propulsion |
|
| Speed |
|
| Range |
|
| Test depth | 30 m (98 ft) |
| Complement | 3 officers, 19 men |
| Armament |
|
| Service record | |
| Part of: |
|
| Operations: | none |
| Victories: | No ships sunk or damaged |
SMU-2 was aGermanU-boat built for theImperial German Navy. She was the second submarine to enter service in the German Navy and was a vast improvement over her predecessorU-1, although problems with her propulsion plant dogged her for the duration of her career.U-2 was only used for gathering experience with operating submarines and for crew training, she saw no active service duringWorld War I.
As the German navy realized it was lagging behind in submarine development,U-2 was ordered fromKaiserliche WerftDanzig (KWD) on 4 March 1906, even before the previous U-boatU-1 had begun her trials.[2][3] The KWD had no experience at all in building submarines, all U-boats so far had been built at theGermaniawerft. But the head of the submarine development department at the KWD, Raimundo Lorenzo de Equevilley Montjustín, the designer of the previousU-1, was a foreigner and the German Navy was reluctant to share the design ofU-2 with him.[2]
U-2 featured a lot of improvements overU-1: with a larger hull there was place for more powerfulDaimler engines and the armament was increased from one 45 cm (17.7 in) bowtorpedo tube to two bow and two stern 45 cm torpedo tubes, armed with six C/03 torpedoes.[4] Apart from the twoperiscopes in theconning tower, a third periscope was installed in the control room. the control room was now placed beneath the conning tower.[5] The speed of the U-boat was not controlled anymore byvariable-pitch propellers but by the electrical engine which was split into three parts, one mounted after and the other two together before the kerosine engine, on the same shaft. Only when cruising the kerosine engines were directly coupled with the shafts. When manoeuvring, the kerosine engines were driving the double electrical engines.[5][6] The peat isolated batteries ofU-1 were replaced with a new type of large surface batteries.[5] OnU-1 the external diving tanks were not large enough so that some of the internal trim and compensating tanks had to be used as diving tanks, but onU-2 all diving tanks were external.[7]
The inexperience with submarine construction led to many delays, but the main reason for taking nearly two years before her launching on 18 June 1908, was the failure of the planned surface propulsion plant. The Daimler engines were not available and reliable before 1910 and finally the same, less powerful,Körting engines as onU-1 were installed, which reduced surface speed to 10.5knots (19.4 km/h; 12.1 mph).[5]
U-2 had a double hull, the inner pressure hull was 39.30 m (128 ft 11 in) long and was cylindrical with a maximum diameter of 3.40 m (11 ft 2 in). The outer hull had anoverall length of 45.42 m (149 ft 0 in), with abeam of 5.50 m (18 ft 1 in) (o/a).[1][8] The pressure hull was made of 12 mm (0.47 in) thick steel, with 1.00 m (3 ft 3 in) distance between frames. The outer hull was made of standard 3.5–4 mm (0.14–0.16 in) thick steel ( as used ontorpedo boats ) with a zinc coating at both sides.[7]U-2 had adraught of 3.05 m (10 ft 0 in), shedisplaced 341 tonnes (336 long tons) when surfaced and 430 t (420 long tons) when submerged.[1][8]
U-2 was refitted in June 1910[9] with two Daimler 6-cylinder two-stroke kerosene engines with a total of 600metric horsepower (441 kW; 592 bhp) for use on the surface and twoSSW double-actingelectric motors with a total of 460 kW (625 PS; 617 shp) for underwater use. Each electrical engine consisted of three components: two six-pole SGM 310/25 of 170 kW (231 PS; 228 shp) at 900rpm each wihich were mounted before the diesel engine, and an eight-pole SGM 330/34 propeller motor which produced 228 kW (310 PS; 306 shp) at 685 rpm which was mounted after the diesel engine. These engines powered two shafts, which gave the boat a top surface speed of 13.2knots (24.4 km/h; 15.2 mph), and 9 knots (17 km/h; 10 mph) when submerged. Cruising range was 1,600nautical miles (3,000 km; 1,800 mi) at 13 kn (24 km/h; 15 mph) on the surface, and 50nautical miles (93 km; 58 mi) at 5 kn (9.3 km/h; 5.8 mph) submerged. Constructional diving depth[a] was 30 m (98 ft 5 in). Her crew numbered three officers and nineteen enlisted men.[1][10][11]
U-2 waslaunched on 18 June 1908,[9] andcommissioned into the Imperial German Navy on 18 July 1908.[12] The U-boat undertook some trials and in the beginning of 1909 had her engine room modified in anticipation of the daimler engines, but once again delivery of these engines was delayed. U-2 remained in the shipyard until June 1910 when the Daimler engines were finally installed. Even then problems with the propulsion were not solved as difficulties with the dynamos rendered the submarine non-operational.[9]
At the beginning of World War I, she was still in refit.[13] During the war, she conducted no war patrols and was used as a training platform. After Germany's surrender, she wasdecommissioned on 19 February 1919 and sold forshipbreaking toStinnes on 3 February 1920.[8]
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