Work out sailing speed (hull speed) instantly with clear inputs, formula shown and shareable results.
Hull speed is 1.34 times the square root of waterline length in feet — the practical ceiling for a displacement hull. Whether a boat reaches it depends on the sail area to displacement ratio: below 15 is under-powered, 16-18 is typical for a cruiser, and above 20 is performance oriented.
Hull speed
V = 1.34 x sqrt(LWL in feet); SA/D ratio = sail area (ft2) / displacement (ft3)^(2/3)
Only surfing down waves or planing, which needs a light hull and a lot of sail. Heavy cruisers effectively cannot.
Because the wave system is generated by the immersed hull. Overhangs contribute nothing until the boat heels and immerses them, which is why hull speed rises slightly when heeled.