Type UB I submarine

The Type UB I submarine (sometimes known as the UB-1 class) was a class of small coastal submarines (U-boats) built in Germany at the beginning of the First World War. Twenty boats were constructed, most of which went into service with the German Imperial Navy (Kaiserliche Marine) 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. 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 for a total of 20 UB Is 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, but also in the Baltic, Pola 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.

In 1918 four of the surviving German boats were converted into coastal minelayers. Of the seventeen boats in German service, two were sold to Austria-Hungary, one was sold to Bulgaria, and nine were lost during the war. One of the five Austro-Hungarian boats was sunk and another mined and not repaired. The five surviving German boats, the four surviving Austro-Hungarian boats, and the Bulgarian boat were all turned over to the Allies after the end of the war and were broken up.

In the earliest stages of the First World War, the German Army's rapid advance along the North Sea coast found the German Imperial Navy without submarines suitable to operate in the narrow and shallow seas off Flanders. By 18 August 1914, two weeks after the German invasion of Belgium, the planning of a series of small coastal submarines had already begun.

The German Imperial Navy stipulated that the submarines must be transportable by rail, which imposed a maximum diameter of 3.15 metres (10 ft 4 in). The rushed planning effort—which had been assigned the name "Project 34"—resulted in the Type UB I design, created specifically for operation from Flanders. The boats were to be about 28 metres (92 ft) long and to displace about 125 tonnes (123 long tons) with two bow torpedo tubes.

On 15 October, eight Type UB I UB-1 – UB-8 were ordered from Germaniawerft Kiel and seven Type UB I UB-9 – UB-15 from AG Weser of Bremen. The Germaniawerft-built boats at 28.10 metres (92 ft 2 in) length overall, were 22 centimetres (8.7 in) longer than the AG Weser-built boats. All were 3.15 metres (10 ft 4 in) abeam, had a draft of 3.03 metres (9 ft 11 in), a height of 7.30 metres (23 ft 11 in) and a constructional diving depth of 50 metres (164 ft 1 in). The boats all had a pressure hull with a length of 23.62 metres (77 ft 6 in), displaced 127 tonnes (125 long tons) while surfaced, but while submerged UB-1 - UB-8 displaced 142 tonnes (140 long tons) whilst UB-9 - UB-17 displaced 141 tonnes (139 long tons). The former had an average diving time of twenty to thirty-three seconds, whilst the latter had an average diving time of twenty-two to thirty-three seconds.

The drivetrain of the boats consisted of a single propeller shaft driven by a four-cylinder, four-stroke RS164 Daimler (Germaniawerft) or Körting (Weser) 60 brake horsepower (45 kW) diesel engine on the surface, or a 90 kW (122 PS; 121 shp) Siemens-Schuckert electric motor for underwater travel. UB-1 - UB-8 had a top surface speed of 6.47 knots (11.98 km/h; 7.45 mph), and 5.50 kn (10.19 km/h; 6.33 mph) when submerged. Cruising range was 1,650 nautical miles (3,060 km; 1,900 mi) at 5 knots (9.3 km/h; 5.8 mph) on the surface and 45 nmi (83 km; 52 mi) at 4 kn (7.4 km/h; 4.6 mph) submerged. UB-9 - UB-17 boats were capable of 7.45 kn (13.80 km/h; 8.57 mph) on the surface and 6.24 kn (11.56 km/h; 7.18 mph) submerged. Cruising range was 1,500 nmi (2,800 km; 1,700 mi) at 5 kn (9.3 km/h; 5.8 mph) on the surface and 45 nmi (83 km; 52 mi) at 4 kn (7.4 km/h; 4.6 mph) submerged. The boats were equipped with two 45-centimetre (17.7 in) bow torpedo tubes and carried just two C/03 torpedoes. They were also armed with a single 8 mm (0.31 in) machine gun affixed to the deck. Type UB I U-boats had a complement of one officer and thirteen men.