Type XXI U-Boats

This unusual photograph shows the twoer of a Type XXI in testing - mounted on U37, a Type IX training U-boat during 1944.

While problems plagued the development of Professor Walter's turbine driven U-boat, Germany was forced to prepare an alternative design for an ocean-going U-boat of high submerged performance. The result was the Type XXI, a major breakthrough in submarine development. Steamlined, heavily armed and equipped with improved schnorchel equipment, the Type XXI acheived new levels of potential performance. Built to operate mainly submerged, the XXI's battery capacity was treble that of previous U-boats, the interior of the boat also being fully air conditioned - a luxury not enjoyed before by Kriegsmarine submariners.

Although propelled by the familiar combination of diesel engines and electric motors, beneath the surface the Type XXI was capable of operating at a maximum submerged speed of 17.25 knots (for a maximum of one hour), able to fire torpedoes blind and reload with a fast and efficient automated reloading system. During depth charging, the U-boat would have been able to engage a silent electric motor for each shaft and dive deep to avoid detection.

Designed to carry two pairs of 3cm AA weapons, production difficulties ensured that 2cm cannon were mounted instead, each twin cannon housed within its own small armoured cupola.

The streamlined outer hull encased a pressure hull formed by two flattened cylinders placed one on top of the other. To speed up the production of the Type XXI, the hull was of all-welded construction and prefabriated in eight sections. This also severely hampered construction, many yards employed to build segments independently of each other and not able to meet the extremely fine tolerances required by U-boat builders. That, coupled with heavy and disruptive Allied bombing, ensured that by the war's end only two Type XIIs had sailed from Norway on a war footing, neither reaching the combat zone before hostilities ended. By contrast eleven were sunk as a result of air or naval attack en-route to Norway from Germany, and three more destroyed by mines. At least twenty-two were damaged by bombing at some stage of construction or working up and either abandoned or damaged beyond repair.

Dimensions: 76.7 metres x 8 metres x 6.3metres (draught).

Displacement: 1,621 tons (1,819 tons submerged).

Complement: 5 officers, 53crew.

Armament: 4 x 2cm (2 x 2) AA cannon
6 x 53.3cm (21") torpedo tubes at bow.

23 x torpedoes or 12 torpedoes and 12 mines.

Propulsion: 2-shaft diesel/electric motors, BHP/SHP 4,000/5,000. Silent creeping motors, SHP 226 = 5 knots.

Speed: 15.5 knots surfaced / 17.25 knots submerged.

Endurance: 11,150 miles (diesel electric surfaced) @ 12 knots.
285 miles (submerged) @ 6knots.

Rated Depth: 134 metres

Derivatives of the Type XXI design

XXIB
Variation to the basic deign to carry more torpedo tubes. The XXIB had a second torpedo compartment forward, but with six rear facing tubes mounted laterally (six each side), trained 10 degrees from the baot's centreline.

XXIC
The same as the XXIB, but with the extra torpedo compartment deepened to allow the mounting of twelve extra tubes as opposed to six.

XXID, XXIE, XXIT, XXI V
Projected supply U-boats based on the basic XXI design. With the reckoning that development of these ttypes would have interfered with the already difficult production of the Type XXI, they were abandoned.