SM UB-91

For other ships with the same name, see German submarine U-91.

UB-148 at sea, a U-boat similar to UB-91.
History
German Empire
Name	UB-91
Ordered	6 / 8 February 1917 [1]
Builder	AG Vulcan, Hamburg
Cost	3,654,000 German Papiermark
Yard number	107
Launched	6 March 1918 [2]
Commissioned	11 April 1918 [2]
Fate	Surrendered 21 November 1918, broken up in 1921 [2]
General characteristics [2]
Class and type	German Type UB III submarine
Displacement	510  t (500 long tons) surfaced 640 t (630 long tons) submerged
Length	55.52 m (182 ft 2 in) (o/a)
Beam	5.76 m (18 ft 11 in)
Draught	3.73 m (12 ft 3 in)
Propulsion	2 shafts 6-cylinder MAN-Vulcan diesel engines, [2] 1,100 ihp (820 kW) Siemens-Schuckert [2] electric motors, 788 ihp (588 kW)
Speed	13 knots (24 km/h; 15 mph) surfaced 7.4 knots (13.7 km/h; 8.5 mph) submerged
Range	7,120  nmi (13,190 km; 8,190 mi) at 6 knots (11 km/h; 6.9 mph) surfaced 55 nmi (102 km; 63 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth	50 m (160 ft)
Complement	3 officers, 31 men [2]
Armament	5 × 50 cm (19.7 in) torpedo tubes (4 bow, 1 stern) 10 torpedoes 1 × 10.5 cm (4.13 in) deck gun [2]
Service record
Part of:	II Flotilla 27 June – 11 November 1918
Commanders:	Kptlt. Wolf Hans Hertwig [3] 11 April – 11 November 1918
Operations:	2 patrols
Victories:	3 merchant ships sunk (13,487  GRT) 1 warship sunk (1,181 tons)

SM UB-91 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 11 April 1918 as SM UB-91. ^{[Note 1]}

On 4 October 1918 UB-91 sank the Hirano Maru, killing among others, Yokohama Specie Bank sub-manager S. Ujie, his wife and three sons, together with bank employee Takashi Aoki and wife Sueko. ^{[4] [5]}

Surrender

Deck gun in Chepstow today

UB-91 was surrendered to Britain on 21 November 1918 at Harwich. She toured the South Wales ports of Cardiff, Newport, Swansea, Port Talbot and was towed to Pembroke Dock, eventually being broken up in Briton Ferry in 1921. ^[6] King George V presented her deck gun to the town of Chepstow by in recognition of the bravery of William Charles Williams RN VC at Gallipoli in 1915. The gun forms part of the Chepstow War Memorial. ^{[7] [8]}

Construction

Main article: German Type UB III submarine

She was built by AG Vulcan of Hamburg and following just under a year of construction, launched at Hamburg on 6 March 1918. UB-91 was commissioned later the same year . Like all Type UB III submarines, UB-91 carried 10 torpedoes and was armed with a 10.5 cm (4.13 in) deck gun. UB-91 would carry a crew of up to 3 officer and 31 men and had a cruising range of 7,120 nautical miles (13,190 km; 8,190 mi). UB-91 had a displacement of 510  t (500 long tons) while surfaced and 640 t (630 long tons) when submerged. Her engines enabled her to travel at 13 knots (24 km/h; 15 mph) when surfaced and 7.4 knots (13.7 km/h; 8.5 mph) when submerged.

Summary of raiding history

Date	Name	Nationality	Tonnage [Note 2]	Fate [9]
25 September 1918	Hebburn	United Kingdom	1,938	Sunk
26 September 1918	USCGC Tampa	United States Coast Guard	1,181	Sunk [10]
28 September 1918	Baldersby	United Kingdom	3,613	Sunk
4 October 1918	Hirano Maru	Japan	7,936	Sunk [10]

References

Notes

1. "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine.
2. Merchant ship tonnages are in gross register tons. Military vessels are listed by tons displacement.

Citations

1. Rössler 1979, p. 61.
2. Gröner 1991, pp. 25–30.
3. Helgason, Guðmundur. "WWI U-boat commanders: Wolf Hans Hertwig". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 8 February 2015.
4. "The Torpedoed "Hirano Maru"". The Singapore Free Press and Mercantile Advertiser. 13 December 1918. Retrieved 4 January 2012.
5. "独政府を相手に損害賠償の訴え". Osaka Asahi Shinbun (in Japanese). 10 July 1919. Archived from the original on 2 March 2018. Retrieved 4 January 2012.
6. Gröner 1991, p. 54.
7. Cadw. "Chepstow War Memorial (Grade II) (2503)". National Historic Assets of Wales . Retrieved 19 February 2021.
8. "Deck Gun from German U-board UB-91 (32858)". Coflein. RCAHMW . Retrieved 19 February 2021.
9. Helgason, Guðmundur. "Ships hit by UB 91". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 8 February 2015.
10. "WW1: New memorial for Pembrokeshire's Japanese dead". BBC News. Retrieved 4 October 2018.

Bibliography

• 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. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN   0-85177-593-4.
• Rössler, Eberhard (1979). Die deutschen U-Boote und ihre Werften: eine Bilddokumentation über den deutschen U-Bootbau; in zwei Bänden (in German). Vol. I. Munich: Bernard & Graefe. ISBN   3-7637-5213-7.