Why retain torpedo tubes in Queen Elizabeth-class refits and the Nelson-class instead of using the weight for machinery?
Short answerThe weight saving was modest, while torpedoes let the battleship itself finish a disabled but still-floating enemy.
NotesEliminating the torpedo installation might save a few hundred tons, useful but not enough to transform a battleship's machinery or speed. Interwar designers still valued the weapon as a guaranteed finishing method. Bismarck illustrates the problem: gunfire could destroy the fighting capability while the protected hull remained afloat. A torpedo could open the citadel to flooding without relying on a destroyer or cruiser still being present. A seemingly obsolete weapon survived when designers valued self-contained capability.