Type XIV submarine
The Type XIV U-boat was designed to resupply other U-boats, being the only submarine tenders built which were not surface ships. It was nicknamed the "Milchkuh/Milchkühe (pl.)" (milk cows) or U-Tanker. Design The Type XIV was based on the Type IXD long-range U-boat design, but with a shorter and deeper hull. The boats had a displacement of when at the surface and while submerged. The U-boats had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarines were powered by two Germaniawerft supercharged four-stroke, six-cylinder diesel engines producing a total of for use while surfaced, two Siemens-Schuckert 2 GU 345/38-8 double-acting electric motors producing a total of for use while submerged. They had two shafts and two propellers. The boats were capable of operating at depths of up to . The submarines had a maximum surface speed of and a maximum submerged speed of . When submerged, the boats could operate for at ; when surfaced, they could travel at . The boats were not fitted with torpedo tubes nor deck guns. The only armament was for defense, consisting of two SK C/30 anti-aircraft