Generally, can be divided into two distinct types, those used in square-riggers which are set on horizontal yards crossing the masts, and those used in fore-and-aft-rigged vessels which are set from their luffs on masts or stays. These two types are sometimes used together, as with the jibs, staysails, and spanker set aboard a square-rigged ship or, in the past, the occasional square sail set from a yard aboard a fore-and-aft-rigged vessel when it was running free. There are exceptions to this general rule: lateen sails and lugsails, though set on a yard, are generally accepted as fore-and-aft sails.
Before the days of synthetic materials and machine stitching, sails were made by hand using the techniques described in sailmaker's stitching. Then, during the 1950s, synthetic materials such as Terylene replaced natural fibres and sails were stitched by machine. Now there is a whole range of new, lighter, and more stable sail materials such as Kevlar and Mylar. There are also new methods of sailmaking which use moulds and glues with computers controlling the cutting of the shape of a sail. Indeed, the shapes of the sails can be so closely controlled that they can be modified for different wind speeds. With the introduction in the 1960s of roller-reefing headsails which were permanently bent on, ultraviolet (uv) light degraded both the Terylene cloth and its stitching. At first a cover of uv-resistant cloth protected the leech of the foresail which remained exposed when furled, but better uv-resistant cloth now allows the whole sail to be made of this.
Chart, which follows the outlines of a map of the Old World, showing the distribution and possible genetic derivation of sails. Not to scale
Subjects: Warfare and Defence — Maritime History.