Sail Cloth

Laminating films to maintain the best strength and shape
The majority of mainsails and headsails are made from the tightly woven polyester fiber known in the United States as Dacron. For spinnakers and other light-weather sails, lightweight rip-stop nylon material is used. Sails made from these materials are used extensively on cruising boats and small club racers.Racing boats, on the other hand—and even some cruisers— are increasingly using sails laminated from newer, stronger, and more stable Kevlar and Spectra materials combined with Mylar, an airtight, thin polyester film. As these technologies become more accepted, other racers seek to push the envelope still farther. High-tech Cuben and carbon fiber are the latest arrivals. Laminated sails do better than polyester and nylon at maintaining their shapes in heavy winds, and typically stretch only a few tenths of a percent under normal working loads. High-quality Dacron stretches about 1 or 2 percent, and nylon much more.The biggest problems currently facing laminated sails are higher cost and a shorter working life compared with Dacron, although it is difficult to compare their respective values on the sole basis of working life. Whereas laminated sails retain their most efficient shape for nearly all their working life, Dacron and nylon sails usually stretch into permanently inefficient shapes after a couple of seasons’ use. It is almost impossible to see the subtle differences that cause the inefficiency, however, so the problem usually goes undetected for years, especially in boats not used for racing.Different weights of cloth are used for different kinds of sails flown in varying wind conditions, but you can estimate the average weight required for everyday working mainsails and headsails by dividing the waterline length of the boat in feet by 3. The answer will be in ounces of cloth per square yard.See also Sailboat Rigs.