About sails
Sail, sheet of canvas, nylon, or other material, used for the propulsion of wind-driven boats and ships. Sails are bent to the masts, to spars attached to the masts, and to fixed lengths of cordage or wire rope, known as stays, fastened to the masts and to the main body of the vessel.
Sails are generally triangular or rectangular in form but are usually cut to allow a certain amount of fullness, or belly, to increase their aerodynamic efficiency. Rectangular sails are almost entirely confined to square-rigged ships on which they are hung from yards (spars mounted horizontally at various heights on the mast across the axis of the vessel). Fore-and-aft-rigged ships employ either triangular sails, with the forward edge of the sail attached to the mast and the bottom edge attached to a boom (a spar that is attached at one end near the bottom of the mast), or quadrilateral sails, with the upper edge attached to a boomlike spar called a gaff.
Names of Sails
In square-rigged ships, sails are named for the position they occupy. Ahead of the foremast on a typical ship, four small triangular sails are hung from stays between the bowsprit and the foremast. These sails are known, from fore to aft, as flying jib, outer jib, inner jib, and jib, and are fore-and-aft sails. Hung from yards on each of the masts, foremast, mainmast, and mizzenmast are six rectangular or square sails of different sizes. The lowest sails on each mast are called the foresail, mainsail, and mizzensail, or crossjack. The two sails above the lowest on each mast are known as the upper topsail and lower topsail and are identified according to the mast from which they hang, as mizzen-upper topsail. Above the upper topsails are the topgallant sails and above these, the royals and the skysails. The lowest sail on each mast, and sometimes the topsail, may also be called a course.
Between the foremast and the mainmast, triangular sails are mounted on stays that slant downward from the mainmast to the foremast. These sails are known as the main-topmast staysail, the main-topgallant staysail, and the main-royal staysail. Sometimes, staysails are similarly attached to stays between the main and mizzenmasts. A small four-sided fore-and-aft sail mounted on the mizzenmast with a boom at the foot and another spar called a gaff at the head of the sail is known as the spanker.
The naming of sails on fore-and-aft-rigged ships depends on the masts and the arrangement of the stays. A typical two-masted schooner carries two sails—a staysail and a jib—ahead of the foremast. The foremast has a triangular or four-sided foresail, and in the latter case may also have a gaff topsail mounted between the gaff of the foresail and the mast. On the mainmast is the triangular or four-sided mainsail; there may also be a main staysail between the foremast and mainmast. Schooners and other fore-and-aft-rigged vessels having quadrangular foresails and mainsails are said to be gaffheaded, and those having triangular sails in these positions are said to be Marconi-rigged or Bermuda-rigged. Sometimes, schooners also carry a square sail on a yard on the foremast and above it another quadrangular sail called a raffe, which is secured to the yard at the foot.
The sail plan of a ketch consists, forward to aft, of staysail, jib, mainsail, and mizzensail, and that of a yawl consists of staysail, jib, mainsail, and jigger. Cutters and sloons carry staysail, jib, and mainsail only. Certain of the above types of boats sometimes substitute a Genoese jib for the jib and staysail. This sail is a large jib with a long foot that overlaps the mainmast or foremast. When the boat is running before the wind, a spinnaker may be set in place of jib and staysail. This is a triangular sail cut with such great fullness that it is sometimes called a balloon jib, or ballooner, with its peak hoisted to the top of the foremast and its foot extended over the side of the vessel by means of a demountable spinnaker pole that is secured to the side of the foremast or mainmast.
Parts of Sails
The upper and lower edges of any four-sided sail are called the head and foot, and in square sails the vertical edges are called leeches. The lower corners of such a sail are known as clews. In four-sided sails used on fore-and-aft-rigged vessels, the head of the sail is laced or otherwise attached to the gaff; the upper corner of the head is called the peak and the lower end (at the mast), the throat. The edge of the sail attached to the mast is the luff. The corner of the sail between the luff and the foot is the tack, and the corner of the sail at the other end of the foot, the clew. The free outer edge of the sail is known as the leech.
The edges of triangular fore-and-aft sails are known as luff, foot, and leech, except in the case of gaff topsails, where they are luff, head, and leech. The corners of triangular sails are the peak, tack, and clew. In spinnakers, which are hoisted to the mast by the peak, the sides are the leeches and the foot, and the two bottom corners are the clews.
Most sails are equipped with some means of reefing, or reducing the area of the sail during stormy weather. Reefing is usually accomplished by means of a set of small ropes or cords, called reef points, that are set in a double row on either side of the sail parallel to the yard or boom. When reefing, the sail is slackened and a portion of it is bunched along the yard or boom and secured there by tying the reef points around the bunched-up sail and the spar.
Sails are never made of single pieces of cloth but are always made from a number of strips of cloth sewed together with flat seams. This structure adds strength to the sail and prevents undue stretching. Sails are reinforced by sewing ropes, called bolt ropes, around all the edges of the sail, and by adding extra thicknesses of canvas at the corners that receive most strain. To attach the rope to the sail, eyes, or cringles, are spliced in the bolt ropes or cut in the cloth of the sail and strengthened with metal or rope rings.

See also Pirates