Was there a sail-area rule that fixed the maximum speed and efficiency of an age-of-sail vessel?
Short answerNo single rule held throughout the period because stronger masts and rigging allowed later ships to carry progressively larger sail plans.
NotesThe answer rejects a single fixed rule for maximum efficient sail area across the age of sail. As masts, yards, cross-trees, and standing rigging improved, ships could spread more canvas both higher and farther outboard. Sail plans consequently grew into increasingly elaborate pyramids around each mast. The practical speed limit changed with rigging technology rather than remaining a constant property of hull size alone.