Type XB U-boat
Length: 89.8 metres
Designed in 1938, the Type XB U-boat was built as a submerged minelayer. Originally, it was intended to carry 66 SMA mines (Schachtmine = Shaft Mine) and 15 torpedoes. Each mine was 2.15 metres long and 1.33 metres diameter and 2 x 12 mines were to be stored in vertical shafts on each side of the hull with a further 6 mineshafts in forward outer hull . Unfortunately, due to a design fault, these mines suffered from premature detonation when they were deployed and it was not until March 1943 that the problem was rectified. Consequently, the XB was used as a U-tanker or Milchkuhs (Milk Cow) since it could carry 240-tons of fuel to supply attack U-boats to extend their endurance. Unlike the other U-boats, the XB had only stern torpedo tubes (2 x 21).