Lateen

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A lateen (from Latin) is a triangular sail set on a long yard mounted at an angle on the mast, and running in a fore-and-aft direction. Originally found on sailing ships, the lateen is used today in a slightly different form on small boats such as the highly popular Sunfish.

History

The lateen rig is believed to have been in use for at least 2,000 years, and is probably of Arab origin. It is quite common in the Mediterranean, the upper Nile, and the northwestern parts of the Indian Ocean, where it is the standard rig for feluccas and dhows.

The European adoption of the lateen in the Late Middle Ages made ships more maneuverable, thus permitting merchants to sail out of the Mediterranean and into the Atlantic Ocean; caravels typically mounted three or more lateens. However, the great size of the lateen yard makes it difficult and dangerous to handle on large ships in stormy weather, and by the 18th century the lateen was restricted to the mizzen mast, then by the beginning of the 19th century was supplanted by the driver or spanker.

However, the lateen survived as a rigging choice for mainsails of small craft where local conditions were favorable. For instance, bargelike vessels in the American maritimes north of Boston, called gundalows, carried lateen rigs throughout the late nineteenth and early twentieth centuries. Because the yard pivots on its point of attachment to the mast, the entire sail and yard can be swiftly dropped. This was an advantage when navigating the tidal riverways of the region, which often necessitated passage under bridges.

Modern small boat lateen sails

The modern lateen differs from traditional lateens by the addition of a spar along the foot of the sail, similar to the crab claw sail traditionally used on the proa. The lower spar is horizontal, and is attached to the mast where it crosses. The front ends of both spars are joined together. Both joints are designed to allow free rotation in all directions. The sheet is attached to the lower spar, and the halyard to the upper spar. The geometry of the sail is such that the upper and lower spars are confined to a plane parallel to the mast. This results in the sail forming a conic section, identical to half of the Rogallo wing commonly found in kites and hang gliders.

The modern lateen is often used as a simple rig for catboats and other small recreational sailing craft. In its most basic form, it requires only two lines, a halyard and a sheet, making it very simple to operate. Often additional lines is used to pull down the lower spar and provide tension along the upper and lower spars, providing greater control over the sail shape.

Since the upper and lower spars provide a frame for the sail, the camber of the sail is simply a function of how tightly the spars stretch the sail. This means that lateen sails are often cut flat, without the complex cutting and stitching required to provide camber in Bermuda rig sails. Curved edges, when mated with the straight spars, provide all or nearly all of the sail curvature needed.

One of the disadvantages of the lateen, especially in the modern form, is the fact that it has a "bad tack". Since the sail is to the side of the mast, on one tack that puts the mast directly against the sail on the leeward side, where it can significantly interfere with the airflow over the sail. On the other tack the sail is pushed away from the mast, greatly reducing the interference.

External links

• [The ship's development during the Middle Ages], see bottom of page for English translation
• [PolySail Interntional] instructions for building a Sunfish-like lateen sail

 

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