How heavy would a Renown-class battlecruiser become with three triple 15-inch turrets?
Short answerThe added beam, hull length, magazine capacity, and ammunition would bring it to roughly Tiger's displacement or somewhat higher.
NotesThe extra weapon in each turret is not an isolated weight increase. Wider barbettes force greater beam, hull proportions then add length, and three more guns require larger magazines and more ammunition. Those cascading changes move the design toward or beyond HMS Tiger's scale.