windsail

Windsail is a term used to describe a sail that captures wind to propel a vessel or vehicle. In everyday language it can refer to any sail on a sailing craft, but in modern nautical engineering it is often associated with wing sails—rigid or semi-rigid sails shaped like airfoils that generate lift as well as drag.

Design and variants

Traditional sails are fabric panels stretched along a mast and boom. Windsails in the wing-sail category use a solid or laminated airfoil profile and are mounted in a fore-and-aft orientation. These sails may rotate with the wind to maintain an optimal angle of attack, and their chord, span, and twist are adjusted to regulate power and efficiency. Control systems for wing sails can be more complex than for conventional sails, reflecting the need for precise alignment and structural integrity.

History and applications

The basic idea of using wind to propel vessels dates back centuries. The wing-sail concept gained prominence in modern high-performance sailing during the late 20th and early 21st centuries, as designers pursued aerodynamic efficiencies beyond traditional fabric sails. Wing sails have been explored on racing yachts and experimental craft to improve upwind performance and overall power.

Advantages and limitations

Wing sails can offer higher lift-to-drag ratios and better upwind efficiency under certain wind conditions, potentially reducing sail area and rigging loads. They require specialized construction, advanced handling skills, and precise maintenance, which can increase cost and complexity. Performance gains are context-dependent and may be offset by structural and operational demands in gusty or variable wind.

See also: wing sail, sailboat, aerodynamics.