What is the furthest a warship could be refitted across changing eras?
Short answerA wooden ship of the line could theoretically pass through broadside and central-battery ironclad stages to a turret ship, though the last step amounts to new construction.
NotesThe longest plausible sequence runs from a ship of the line through broadside and central-battery ironclad forms to a turret ship over roughly three decades. The earlier conversions could still produce useful first- or second-line combatants. By the turret stage, the result would be a coastal-defence or bombardment asset rather than a competitive fleet unit. A yard pursuing the whole sequence would effectively build a new ship while calling it a refit, consuming scarce dock space as an industrial employment programme rather than an economical naval solution.