UB-148 at sea, a U-boat similar to UB-115.
|Ordered:||6/8 February 1917|
|Builder:||Blohm & Voss, Hamburg|
|Cost:||3,714,000 German Papiermark|
|Launched:||4 November 1917|
|Commissioned:||28 May 1918|
|Fate:||Sunk 29 September 1918 by British warships and aircraft at Coordinates: .|
|General characteristics |
|Class and type:||German Type UB III submarine|
|Length:||55.30 m (181 ft 5 in) (o/a)|
|Beam:||5.80 m (19 ft)|
|Draught:||3.70 m (12 ft 2 in)|
|Test depth:||50 m (160 ft)|
|Complement:||3 officers, 31 men|
|Victories:||1 merchant ship sunk (336 GRT)|
SM UB-115 was a German Type UB III submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. She was commissioned into the German Imperial Navy on 28 May 1918 as SM UB-115.[Note 1] She was the only German submarine commissioned with the number 115.
She was built by Blohm & Voss of Hamburg and following just under a year of construction, launched at Hamburg on 4 November 1917. UB-115 was commissioned in the spring the next year under the command of Oblt.z.S. Reinhold Thomsen. Like all Type UB III submarines, UB-115 carried 10 torpedoes and was armed with a 8.8 cm (3.46 in) deck gun. UB-115 would carry a crew of up to 3 officer and 31 men and had a cruising range of 7,420 nautical miles (13,740 km; 8,540 mi). UB-115 had a displacement of 519 t (511 long tons) while surfaced and 649 t (639 long tons) when submerged. Her engines enabled her to travel at 13.3 knots (24.6 km/h; 15.3 mph) when surfaced and 7.4 knots (13.7 km/h; 8.5 mph) when submerged.
On 29 September 1918 while under the command of Reinhold Thomsen, UB-115 was engaged by armed trawlers (amongst others Viola), the airship R29, HMS Ouse and HMS Star. UB-115 was depth charged until destroyed and went down at position (WGS84), about 4.5 nautical miles (8.3 km; 5.2 mi) northeast of Beacon Point, Newbiggin-by-the-Sea, off Northumberland. All 39 men aboard the submarine died in the attack and sinking. 
The UB-115 left Zeebrugge on 18th September 1918 for a patrol along the north east coast of England. On 29th September she was submerged 4½ miles off Newbiggin-by-the-Sea when at 1.29 p.m. the crew of the British airship R29 sighted an oil slick on the surface. The R29 was escorting a Scandinavian convoy at the time. The airship then dropped a 230-pound bomb to indicate the location. The British destroyer OUSE arrived on the scene but could not find the oil until the R29 dropped another bomb and a calcium flare. This time the OUSE, now joined by the STAR, found the spot and the two destroyers proceeded to drop seven depth charges at 50, 100 and 200 feet; three trawler joined the hunt and dropped ten more charges. Oil and air began to come up in considerable quantities, though the air bubbles were quite small. Evidently the U-boats hull was still fairly tight. At 2 p.m. she started her motors but soon stopped them again after the trawlers, listening with hydrophones, dropped twelve more charges. An hour later she tried again; two more depth charges brought up oil. At this point she was unable to reach the surface, for between 4 p.m. and 6.25 p.m. she ran her motors constantly in spite of the depth charges occasionally dropped. Oil came up all night, and two days later sweepers located an obstruction from which oil was still rising. Nothing more was heard from the UB-115 and the entire crew were presumed to have perished along with their vessel. It is worth noting that UB-115 was the last U-boat to leave Zeebrugge to attack shipping. (U-boats Destroyed, R. M. Grant)
Summary of raiding history
|21 September 1918||Staithes||United Kingdom||336||Sunk|
- "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.
- Tonnages are in gross register tons
- Rössler 1979, p. 66.
- Gröner 1991, pp. 25-30.
- Helgason, Guðmundur. "WWI U-boat commanders: Reinhold Thomsen". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 10 March 2015.
- Helgason, Guðmundur. "WWI U-boat commanders: UB 115". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 September 2010.
- MHSC. "Viola-Dias, War, Distant Waters and the Hull Fishing Industry in Both World Wars" (PDF). MHSC Maritime Historical Studies Centre. University of Hull. Retrieved 3 March 2009.
- Helgason, Guðmundur. "Ships hit by UB 115". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 10 March 2015.
- Bendert, Harald (2000). Die UB-Boote der Kaiserlichen Marine, 1914-1918. Einsätze, Erfolge, Schicksal (in German). Hamburg: Verlag E.S. Mittler & Sohn GmbH. ISBN 3-8132-0713-7.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
- Rössler, Eberhard (1979). U-Bootbau bis Ende des 1. Weltkrieges, Konstruktionen für das Ausland und die Jahre 1935 - 1945. Die deutschen U-Boote und ihre Werften (in German). I. Munich: Bernard & Graefe. ISBN 3-7637-5213-7.
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