68.3mm long (2.68")
The German aircraft carrier I was a planned conversion of the transport ship Europa during World War II. The loss of the battleship Bismarck and near torpedoing of her sister ship Tirpitz in May 1941 and March 1942, respectively, spurred the Kriegsmarine to acquire aircraft carriers. Europa was one of several vessels selected for conversion into auxiliary aircraft carriers. As designed, the ship would have had an air complement of 24 Bf 109T fighters and 18 Ju 87C Stuka dive-bombers.
(more on Wiki HERE)