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GERMAN U BOAT 1940 TO 1945
Type Oceanic conventional Submarine
Displacement
1,621 t (1,595 long tons) surfaced
1,819 t (1,790 long tons) submerged[1]
Length 76.70 m (251 ft 8 in)[1]
Beam 8 m (26 ft 3 in)[1]
Draught 6.32 m (20 ft 9 in)[1]
Propulsion
Geared Diesel/Geared battery-electric/CODABEL/Diesel-electric beltdrive/Low-noise electric beltdrive.
2× MAN M6V40/46KBB geared supercharged 6-cylinder diesel engines, 4,000 PS (3,900 shp; 2,900 kW), driving:
2× SSW geared GU365/30 double-acting electric motors, 5,000 PS (4,900 shp; 3,700 kW)[1]
2 × SSW GV232/28 "creep motors", 226 PS (223 shp; 166 kW) for silent running, and to keep the boat moving while the batteries are being recharged.
2 shafts
Speed
15.6 knots (28.9 km/h; 18.0 mph) surfaced
17.2 knots (31.9 km/h; 19.8 mph) submerged[1][3]
6.1 knots (11.3 km/h; 7.0 mph) (silent running motors)
Range
15,500 nmi (28,700 km; 17,800 mi) at 10 knots (19 km/h; 12 mph) surfaced
340 nmi (630 km; 390 mi) at 5 knots (9.3 km/h; 5.8 mph) submerged[1]
Test depth 240 m (787 ft)[1]
Complement 5 officers, 52 enlisted men[4]
Armament
6 × 53.3 cm (21 in) torpedo tubes (bow)
23 G7 torpedoes (or 17 torpedoes and 12 mines)
2 x twin 2 cm (0.79 in) C/30 anti-aircraft guns[4]
Armour Bridge: 17mm
Type XXI submarines were a class of German diesel–electric Elektroboot (German: "electric boat") submarines designed during the Second World War. One hundred eighteen were completed, with four being combat-ready. During the war only two were put into active service and went on patrols, but these were not used in combat.
They were the first submarines designed to operate primarily submerged, rather than spending most of their time as surface ships that could submerge for brief periods as a means of escaping detection. They incorporated many batteries to increase the time they could spend submerged, to as much as several days, and they only needed to surface to periscope depth for recharging via a snorkel. The design included many general improvements as well: much greater underwater speed by an improved hull design, greatly improved diving times, power-assisted torpedo reloading and greatly improved crew accommodations. However, the design was also flawed in many ways, with the submarines being mechanically unreliable[5] and, according to post-war analysis, vulnerable to combat damage. The Type XXI submarines were also rushed into production before design work was complete, and the inexperienced facilities which constructed the boats were unable to meet necessary quality standards.
After the war, several navies obtained Type XXIs and operated them for decades in various roles, while large navies introduced new submarine designs based on them. These include the Soviet Whiskey, American Tang, British Porpoise, and Swedish Hajen III classes, all based on the Type XXI design to some extent.[6]
Description
The main features of the Type XXI were the hydrodynamically streamlined hull and conning tower and the large number of battery cells, roughly triple that of the Type VII submarine. This gave these boats great underwater range and dramatically reduced the time spent on or near the surface. They could travel submerged at about 5 knots (9.3 km/h; 5.8 mph) for about 75 hours[7] before recharging batteries, which took less than five hours using the snorkel due to the new super-charged diesel engines. Being designed primarily for submerged use, the Type XXI's maximum surface speed (15.6 knots) was lower than that of the Type IX (18.2 knots) but its submerged speed was more than twice that of the Type IX (17.2 knots versus 7.7 knots) because they were equipped with much more powerful electric drive motors and had less drag.[8][9]
The Type XXI was also much quieter than the VIIC, making it more difficult to detect when submerged, and the design eliminated protruding components that had created drag in earlier models. The new, streamlined hull design allowed submerged speed of 17.2 kn (19.8 mph; 31.9 km/h), versus 7.6 kn (8.7 mph; 14.1 km/h) for the Type VIIC.[10] The ability to outrun many surface ships while submerged, combined with improved dive times (also a product of the new hull form), made the Type XXI much more difficult to pursue and destroy.[11] It also provided a sprint ability when positioning itself for an attack. Older boats had to surface to sprint into position. This often revealed a boat's location, especially after aircraft became available for convoy escort. The Type XXI was also equipped with a pair of electric "creep motors" for silent running.[11]
The Type XXI was equipped with six bow torpedo tubes (instead of the more common four in German submarines) and carried 23 torpedoes.[12] It featured an electric torpedo-reloading system that allowed all six bow torpedo tubes to be reloaded faster than a Type VIIC could reload one tube.[13] The Type XXI could fire 18 torpedoes in less than 20 minutes. The class also featured a very sensitive passive sonar for the time, housed in the "chin" of the hull.
The Type XXIs also had better facilities than previous U-boat classes, with much roomier crew berths, and a freezer to prevent food spoilage.[14] The increased capacity allowed for a crew of 57.[15][16]
A post-war assessment of the Type XXI by the United States Navy concluded that while the design had some admirable features, it was seriously flawed.[17] The submarines' engines were underpowered, which limited the surface speed and increased the time required to charge the batteries. The hydraulic system was unduly complex, and its main elements were located outside the pressure hull. This made the system highly vulnerable to corrosion and damage. The snorkel was also badly designed, and difficult to use in practice.[18]
Construction
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