Forces on sails (3 m) = 5-m/s (≈10-knot) wind at 3 m above the water would be approximately "V" (15 m) = 6 m/s (≈12 knots) at 15 m above the water. In hurricane-force winds with "V" (3 m) = 40-m/s (≈78 knots) the speed at 15 m would be "V" (15 m) = 49 m/s (≈95 knots) with "p" = 0.128. This suggests that sails that reach higher above the surface can be subject to stronger wind forces that move the centre of effort ("CE" ) higher above the surface and increase the heeling moment. Additionally, apparent wind direction moves aft with
Forces on sails mainsail causes the stagnation line on the jib to be shifted forward and allows the boat to point closer to the wind, owing to higher leeward velocities of the air over both sails. Sails characteristically have a coefficient of lift ("C") and coefficient of drag ("C") for each apparent wind angle. The planform, curvature and area of a given sail are dominant determinants of each coefficient. Sails are classified as "triangular sails", "quadrilateral fore-and-aft sails" (gaff-rigged, etc.), and "square sails". The top of a triangular sail, the "head", is raised by a halyard, The forward lower corner of the sail,