Amainsail is a sail rigged on the mainmast of asailing vessel.[1]
Historical fore-and-aft rigs used a four-sidedgaff rigged mainsail, sometimes setting a gafftopsail above it.
Whereas once the mainsail was typically the largest sail, today the mainsail may be smaller than the jib or genoa;Proutcatamarans typically have amainmast stepped further aft than in a standard sloop, so that the mainsail is much smaller than the foresail.[2]
The modernBermuda rig uses a triangular mainsailaft of the mast, closely coordinated with ajib for sailing upwind. A large overlapping jib orgenoa is often larger than the mainsail. In downwind conditions (with the wind behind the boat) aspinnaker replaces the jib.
Some mainsails are "full-batten" mainsails, meaning thebatten extends all the way from the mast to the leach of a sail. A partial batten extends from the leech partway to the mast. Battens enable the mainsail to project farther away from the mast. However, there is some cost associated with the battens themselves, "batten pockets" need to be sewn into the sail, and "batten cars" may be needed to allow the sail to be raised and lowered.[3]
BeforeNathanael Greene Herreshoff's invention of sail tracks and slides in the 1880s, mainsails were limited in height. Traditional mainsails were held against the mast by hoops that went the full way around the mast. This meant a traditional mainsail could be raised no higher than the first point a rope or wire was required to keep the mast upright. Further mainsail area (and height) was obtained by adopting a gaff rig.
A mainsail may be fixed to the boom via slugs, cars, or abolt-rope, or may be "loose-footed," meaning it is only attached at the tack and clew.[4]
