Sail components

A sail may be classified in a variety of ways, including by its orientation to the vessel (e.g. fore-and-aft) and its shape, (e.g. (a)symmetrical, triangular, quadrilateral, etc.).

Sails are typically constructed out of flexible material that is shaped by various means, while in use, to offer an appropriate airfoil, according to the strength and apparent direction of the wind.

[3] Gaff, gunter, lug, junk and some sprit sails have four sides and are set fore and aft so that one edge is leading into the wind, forming an asymmetric quadrilateral shape.

This added area would flutter in the wind and not contribute to the efficient airfoil shape of the sail without the presence of battens.

[1] Offshore cruising mainsails sometimes have a hollow leech (the inverse of a roach) to obviate the need for battens and their ensuing likelihood of chafing the sail.

There are several key factors in evaluating a fiber for suitability in weaving a sail-cloth:[1][3] Traditionally, sails were made from flax or cotton canvas.

[3][1] Woven materials, like Dacron,[24] may be specified as either high or low tenacity, as indicated, in part by their denier count (a unit of measure for the linear mass density of fibers).

Sailcloth is typically heat-shrunk to tighten the weave and then receives a chemical bonding finish of melamine.

Mainsails are more likely to be bi-radial, since there is very little stress at the tack, whereas head sails (spinnakers and jibs) are more likely to be tri-radial, because they are tensioned at their corners.

[3] Higher-performance sails may be laminated, constructed directly from multiple plies of filaments, fibers, taffetas, and films—instead of woven textiles—and adhered together.

[3] Measures for seam structural attributes—shown with a typical value for a sewn seam—include:[30] Whereas textiles are typically sewn together, other sail materials may be ultrasonically welded—a technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being held together under pressure to create a solid-state weld.

The corners of triangular sails are typically areas of high stress and consequently often have reinforced layers and tape radiating from, whether cross-cut or radial in construction.

Only the clews on a square sail take a comparatively large amount of stress, because the head is supported along the spar.

[1] Junk rigs feature full-length battens that facilitate short-handed sail handling, including reefing.

Where sails are attached to a mast, spar, or stay there is some kind of connection—often it's the bolt rope running through a groove in the mast, boom, or head foil—otherwise, there is a piece of hardware involved, e.g.: Other hardware includes cam cleats, used to tension luff and foot lines.

[35] Gaff-rigged sails require an extra set of lines to secure the part of the leech that becomes the new clew.

[4] Mainsails on Bermuda rigs typically have paired grommets that secure the luff and leech to the boom, as the sail is lowered to reduce its area.

[35] Tell-tales are pieces of yarn, thread or tape that are affixed to sails to help visualize airflow over their surfaces.