Type X (XB) U-boats were a special type of large Germansubmarine (U-boat). Eight were built during World War II. Although intended as long-range mine-layers, they were mainly used as supply submarines, a task they shared with the Type XIV.
All U-boats of the German Kriegsmarine were potential minelayers since the Germans had devised TMB and TMC torpedo-mines which could be ejected through torpedo tubes. These torpedo-mines were ground mines which had to be laid in shallow waters of maximum 20m (65ft 7in) depth. For minelaying in deeper waters a torpedo mine would not be effective since the space needed for the anchor of the mine would reduce the size of the warhead. The Germans had in mind to develop a larger SMA moored mine, to be laid through mine shafts by a large, dedicated submarine.[1]
Two designs were produced for a minelaying submarine:[2] the initial Type X design had the same layout as the world war IType UE II, with a bow torpedo compartment and dry storage for mines in a stern compartment, which were ejected through horizontal tubes. Dry storage allowed mine detonators to be individually adjusted before launch. This submarine was projected to displace 2,284t (2,248 long tons). A further variant, the Type XA was projected to displace up to 2,500t (2,500 long tons), by adding lateral mine shafts in the saddle tanks for mines in wet storage. But in the end the German navy adopted a much smaller Type XB submarine, which kept the saddle mine shafts but substituted the stern dry storage mine compartment for a bow wet storage mine compartment with six vertical shafts. This allowed to install larger diesel engines for better surface speed. Instead of the four bow torpedo tubes, two stern torpedo tubes were installed.[1][3]
On 25 September 1937, plans were approved to start building a Type XB U-boat on 1 October 1938 at the Germaniawerft in Kiel, with a building time of two years. The design of the large U-boat took more time than foreseen, and construction was delayed. In October 1938, after Hitler made clear he wanted to reject the Anglo-German Naval Agreement, the German navy initiated the Plan Z for the construction of a large German fleet. The plan Z called for the construction of nine Type XB by 1944: three to be built between April 1939 and September 1941, one between April 1941 and December 1943 and a further five between April 1942 and September 1945. The first three Type XB U-116 - U-118 were ordered in January 1939. At the outbreak of World War II, the plan Z was cancelled and various alternative U-boat construction programmes were considered. On 15 June 1940 a restricted Construction Programme was approved, which foresaw the delivery of four Type XBs between April 1941 and January 1942.[4] As Dönitz supported Type XB construction for minelaying in remote waters, by June 1941 four more were ordered, for delivery in 1942-43.[5]
Characteristics
A Type XB U-boat had an overall length of 89.90m (294ft 11in), a beam of 9.20m (30ft 2in) and a draft of 4.71m (15ft 5in). On the surface a Type XA displaced1,763t (1,735 long tons), and submerged 2,177t (2,140 long tons). The length of the pressure hull was 70.90m (232.6ft) and had a maximum diameter of 4.75m (15ft 7in).[6][3]
The boat was powered on the surface by two nine-cylinder, four-strokeMAN AG F46 a 9 pu diesel engines, giving a total of 4,200 brake horsepower (3,100kW), which gave a maximum speed of 17 knots (31km/h; 20mph). With a fuel capacity of 368t (362 long tons), the range was 18,450nmi (34,170km; 21,230mi) at 10 knots (19km/h; 12mph). When submerged it was propelled by two double-acting AEG GU 720/8-287 electric motors, giving a total of 800 kilowatts (1,100hp). Maximum submerged speed was 7 knots (13km/h; 8.1mph) and maximum range was 93nmi (172km; 107mi) at 4 knots (7.4km/h; 4.6mph). Their complement consisted of five officers and forty-seven men.[7][6][8][3]
A Type XB was equipped with sixty-six SMA mines, stored in twenty-four two-mine shafts in the saddle tanks, and six three-mine shafts going through the pressure hull in the foreship. There were no bowtorpedo tubes, but two 53.3cm (21.0in) torpedo tubes were installed at the stern. Five torpedoes were stored internally, two in the torpedo tubes and three below the main deck. A further six spare torpedoes were stored externally below- upper deck in pressure-tight cannisters. As built, they had a gun armament consisting of one 10.5cm (4.1in)deck gun mounted before the conning tower, one 3.7 cm SK C/30 mounted behind the conning tower and one 2cm (0.79in) C/30 mounted on a platform aft of the conning tower. By 1944 the deck had disappeared as it was not useful, and the single 2 cm gun was replaced by two twin 2 cm guns.[9]
Service history
When the Type XB entered service in 1941, the SMA mine suffered from premature explosions and was not yet ready for operational use. As these U-boats carried a lot of fuel and there was a shortage of Type XIV supply U-boats, it was decided to convert the Type XB to a supply U-boat. This conversion involved the installation of up to eight additional external torpedo canisters. These extra canisters were placed in pallets on top of the saddle tanks, one pair forward and three pairs at the rear. The forward pair of canisters was protected with a shield to reduce water resistance.[10][11]
U-118 under attack by aircraft from USS Bogue (CVE-9)
U-116 was the first Type XB to start a patrol: on 25 April she left harbor to supply the U-boats of wolfpackHecht, but on 29 April U-116 had to abort the patrol after sustaining damage in an air attack. She resailed on 16 May to support Hecht in the North Atlantic and completed her first successful mission on 9 June.[12] On her second mission she supported wolfpack Hai in the South Atlantic. During the attack of the wolfpack on convoy OS-33 she sank one merchant ship and shared in the credit for another one with U-201.[13][14]
By September 1942 U-117 and U-118 became available for operations and as only two Type XIV were operational, they were also badly needed for supply missions.[15]U-118 executed her first supply mission between 19 September and 18 October when she transferred from Germany to France. U-116 left for her third mission on 22 September but went missing in the beginning of October.[16] U-117 started her first patrol by laying an unproductive minefield on the North-West coast of Iceland and then continued her mission by supplying U-boats in the North Atlantic.[17]
The construction of the eigth and last Type XB U-234 was much delayed, because of bomb damage caused by an air raid. Soon after the U-234 was commissioned on 2 March 1944, it was decided to convert her and the one other surviving Type XB U-219 to a transport U-boat. U-234 surrendered to US Navy ships on 14 May 1945 while en route for Japan with a cargo that included 560kg uranium oxide, two Me 262 jet fighters, and 10 jet engines. U-219 reached Batavia (present-day Jakarta) in December 1944 with a cargo including dismantled V-2 rockets for Japan. Following Germany's surrender, U-219 was seized by the Japanese at Batavia on 8 May 1945 and on 15 July 1945 was placed into service with the Imperial Japanese Navy as I-505.
Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis: Naval Institute Press. ISBN0870219626.
Blair, Clay (1998). Hitler's U-Boat War: The Hunters 1939–1942. Vol.1. Cassell. ISBN0-304-35260-8.
Blair, Clay (1998). Hitler's U-Boat War: The Hunted 1942–1945. Vol.2. Cassell. ISBN0-304-35261-6.
Gröner, Erich; Jung, Dieter; Maass, Martin (1991). German Warships 1815–1945, U-boats and Mine Warfare Vessels. Vol.2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN0-85177-593-4.
Herzog, Bodo (1993). Deutsche U-Boote: 1906−1966[German U-boats: 1906−1966] (in German). Erlangen: Müller. ISBN978-3-86070-036-5.
Miller, David (2000). U-boats: history, development and equipment 1914-1945. London: Conway Maritime Press. ISBN9780851777900.
Möller, Eberhard; Brack, Werner (2004). The Encyclopedia of U-Boats: from 1904 to the present. London: Chatham. ISBN978-1-85367-623-9.
Rössler, Eberhard (1981). The U-boat: The evolution and technical history of German submarines. London: Cassell & Co. ISBN0-304-36120-8.
Williamson, Gordon (2005). Wolf Pack: The Story of the U-boat in World War II. Oxford: Osprey Publishing. ISBN1-84176-872-3.
Further reading
Kemp, Paul (1999). U-boats destroyed: German submarine losses in the World Wars. London: Arms & Armour. ISBN1854095153.
Rohwer, Jürgen (2005). Chronology of the War at Sea 1939–1945: The Naval History of World War Two (Third Reviseded.). Annapolis, Maryland: Naval Institute Press. ISBN1-59114-119-2.
Sharpe, Peter (1998). U-Boat Fact File: Detailed Service Histories of the Submarines Operated by the Kriegsmarine 1935-1945. Leicester: Midland Publishing. ISBN1-85780-072-9.
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