mainsail

A mainsail is the primary sail on a sailboat’s mainmast. On most modern rigs it is a triangular sail attached along its luff to the mast and along its foot to the boom. It is raised with a halyard and controlled at the clew by the mainsheet. In a fore-and-aft rig such as a sloop, the mainsail is usually the largest sail and provides most of the driving power when sailing upwind or on reaches.

Design and construction commonly reflect a Bermuda rig, with a three-cornered sail that may include a roach—an extended leech area—to increase sail area. Many mainsails use battens to hold their shape, and reef points to reduce area in strong winds. Materials range from woven polyester (Dacron) sailcloth to laminated or composite fabrics, with racing sails often using lighter, more advanced materials. Some sails feature a square-top design to gain extra area for high-speed racing, though this adds complexity and handling considerations.

Control and handling involve several components: the halyard hoists the sail, the outhaul tensions the foot, and the mainsheet along with the traveler trims the leech and controls sail angle. The boom vang or other devices help manage sail twist, especially when sailing off-wind. Reefing allows lowering the sail area quickly in heavy weather.

Maintenance and care focus on checking stitching, seams, and battens, drying and storing sails away from direct sun when not in use, and inspecting rigging connections to ensure reliable performance and longevity.