SM U-66

History
German Empire
Name	U-66
Ordered	2 February 1913
Builder	Germaniawerft, Kiel[2]
Yard number	203[1]
Laid down	1 November 1913, as U-7 (Austria-Hungary)[1]
Launched	22 April 1915[1]
Commissioned	23 July 1915[1]
Fate	Missing since 3 September 1917, possibly in the Dogger Bank area to a mine. 40 dead (all hands lost)[1]
General characteristics [3]
Type	Type U 66 submarine
Displacement	791 t (779 long tons) surfaced 933 t (918 long tons) submerged
Length	69.50 m (228 ft) (o/a) 54.66 m (179 ft 4 in) (pressure hull)
Beam	6.30 m (20 ft 8 in) (o/a) 4.15 m (13 ft 7 in) (pressure hull)
Height	7.95 m (26 ft 1 in)
Draft	3.79 m (12 ft 5 in)
Propulsion	1 × shaft 2 × Germania 6-cylinder four-stroke diesel engines, 2,269 shp (1,692 kW) total 2 × SSW electric motors, 1,223 shp (912 kW) total
Speed	16.8 knots (31.1 km/h; 19.3 mph) surfaced 10.3 knots (19.1 km/h; 11.9 mph) submerged
Range	7,370 nmi (13,650 km; 8,480 mi) at 8 knots (15 km/h; 9.2 mph) surfaced 115 nmi (213 km; 132 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth	50 m (160 ft)
Complement	4 officers, 32 enlisted men
Armament	5 × 45 cm (17.7 in) torpedo tubes (four bow, one stern) 12 torpedoes 1 × 8.8 cm (3.5 in) SK L/30 deck gun, later replaced by 10.5 cm (4.1 in) SK L/45 deck gun
Service record
Part of:	Baltic Flotilla 17 October 1915 – 15 January 1916[1] IV Flotilla 15 January 1916 – 3 September 1917
Commanders:	Kptlt. Thorwald von Bothmer[4] 23 July 1915 – 16 June 1917 Kptlt. Gerhard Muhle[5] 17 June – 3 September 1917
Operations:	7 patrols
Victories:	25 merchant ships sunk (73,847 GRT) 2 merchant ship damaged (6,714 GRT) 1 warship damaged (5,250 tons) 1 merchant ship taken as prize (1,005 GRT)

SM U-66 was the lead ship of the Type U-66 submarines or U-boats for the Imperial German Navy (German: Kaiserliche Marine) during World War I. The submarine had been laid down in Kiel in November 1913 as U-7, the lead ship of the U-7 class for the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine). They became convinced after the outbreak of war in August 1914 that none of these submarines could be delivered to the Adriatic via Gibraltar, and sold the entire class, including U-7, to the German Imperial Navy in November 1914.

Under German control, the class became known as the U-66 type and the boats were renumbered; U-7 became U-66, and all were redesigned and reconstructed to German specifications. U-66 was launched in April 1915 and commissioned in July. As completed, she displaced 791 tonnes (779 long tons) when surfaced and 933 tonnes (918 long tons) submerged. The boat was 69.50 metres (228 ft) long and was armed with five torpedo tubes and a deck gun.

As a part of the Baltic and IV Flotillas, U-66 sank 25 ships with a combined gross register tonnage of 73,847 in six war patrols. The U-boat also torpedoed and damaged the British cruiser Falmouth in August 1916. U-66 left Emden on her seventh patrol on 2 September 1917 for operations in the North Channel. The following day the U-boat reported her position in the North Sea but neither she nor any of her 40-man crew were ever heard from again. A postwar German study offered no explanation for U-66's loss, although British records suggest that she may have struck a mine in the Dogger Bank area.