U-boat Type IXB The Type Ⅸ U-boat was a development of the TypeⅠU-boat. It was an excellent ocean-gonging submarine, capable of operating in great distant waters and far more spacious and comfortable than the Type Ⅶ. Its bigger size, however, meant that its diving speed was rather slower than the Type Ⅶ. Without the external saddle tanks of the Type Ⅶ, the Type Ⅸ was a much sleeker looking boat and had greater fore and aft deck space. She had six torpedo tubes, four in the bow and two astern. Up to 23 torpedoes were stored. Secondary armament was provided by one 105 mm deck gun with about 110 rounds. AA armament differed throughout the war.