German Type UB I submarine

SM UB-2 and SM UB-16 in Flanders.
Class overview
Builders:	Friedrich Krupp Germaniawerft, Kiel (8) AG Weser, Bremen (12)
Operators:	German Imperial Navy  Austro-Hungarian Navy  Bulgarian Navy
Preceded by:	Type UA
Succeeded by:	Type UB II
Built:	1914–1915
In commission:	1915–1918
Completed:	20
Lost:	10
Scrapped:	10
General characteristics
Type:	coastal submarine
Displacement:	127 tonnes (125 long tons), surfaced 142 tonnes (140 long tons), submerged
Length:	27.88–28.10 m (91 ft 6 in–92 ft 2 in) (o/a) 23.62 m (77 ft 6 in) pressure hull
Beam:	3.15 m (10 ft 4 in)
Height:	7.30 m (23 ft 11 in)
Draught:	3.03 m (9 ft 11 in)
Propulsion:	1 × Daimler (UB-1–UB-8) or Körting 4-cylinder diesel engine, 59 bhp (44 kW) 1 × electric motor, 118 shp (88 kW) 1 × shaft
Speed:	6.47 knots (11.98 km/h; 7.45 mph), surfaced 5.5 knots (10.2 km/h; 6.3 mph), submerged
Range:	1,650 nmi (3,060 km; 1,900 mi) at 5 knots (9.3 km/h; 5.8 mph) surfaced 45 nmi (83 km; 52 mi) at 4.5 knots (8.3 km/h; 5.2 mph) submerged
Test depth:	50 metres (160 ft)
Complement:	14
Armament:	2 × 45 cm (17.7 in) torpedo tubes (bow, 2 × torpedoes) 1 × 8 mm (0.31 in) machine gun
Notes:	33-second diving time

The Type UB I was a class of small coastal submarines (U-boats) built in Germany at the beginning of the First World War. 20 boats were constructed, most of which went into service with the German Imperial Navy. Boats of this design were also operated by the Austro-Hungarian Navy (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) and the Bulgarian Navy. The group is sometimes known as the UB-1 class after SM UB-1, the class leader. In the Austro-Hungarian Navy, it was called the U-10 class.

Built to meet the need for small maneuverable submarines able to operate in the narrow, shallow seas off Flanders, the vessels were intended to be quickly constructed, then shipped by rail and assembled at their port of operation. The design effort began in mid-August 1914 and by mid-October the first 15 boats were ordered from two German shipyards. The German Imperial Navy subsequently ordered an additional pair of boats to replace two sold to Austria-Hungary, who ordered a further three boats in April 1915. A total of 20 UB Is were built. Construction of the first boats for Germany began in early November 1914; all 20 were completed by October 1915. Several of the first boats underwent trials in German home waters, but the rest were assembled and tested at either Antwerp or Pola. The German boats operated primarily in the Flanders, Baltic, and Constantinople Flotillas. The boats were about 28 metres (92 ft) long and displaced 127 tonnes (125 long tons) when surfaced and 142 tonnes (140 long tons) while submerged. All had two bow torpedo tubes and two torpedoes, and were equipped with a deck-mounted machine gun.