Lateen

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A vessel (xebec) with three lateens

Dhow with lateen sail in "bad tack" with the sail pressing against the mast, in Mozambique.

A 17th Century woodcut of a triangular-sailed Bermudian vessel. It's raked masts were a development of the lateen.

A lateen (from a la trina, meaning triangular) is a triangular sail set on a long yardarm 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 like the highly popular Sunfish.

[edit] History

According to some historians, the European lateen was copied from Arab mariners. They, in turn, had not invented this type of sail but perfected what they had encountered on the western coast of India (see, Ronald Watkins, Unknown Seas, p. 15).

See also "Dhows" by David Howarth; London, Quartet Books, 1977.

The lateen rig is believed to have been in use for at least 2,000 years in its European history. It was first introduced by the Romans in the 3rd century, and later widely used by Byzantines and Arabs. 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 lateen sail was independently invented in Polynesia.

Until the 14th century the lateen sail was employed primarily on the Mediterranean sea, while the Atlantic and Baltic vessels relied on square sails. The Northern European adoption of the lateen in the Late Middle Ages was a specialized sail that was one of the technological developments in shipbuilding that made ships more maneuverable, thus, in the historian's traditional progression, 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 yardarm makes it difficult and dangerous to handle on large ships in stormy weather, and by the eighteenth century the lateen was restricted to the mizzen mast. In the early nineteenth century the lateen was replaced in European ships 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. Likewise, lateen sail survived at Baltic until the late 19th century. 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 required passage under bridges.

One of the disadvantages of the lateen, especially in the modern form described below, 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. On modern lateens, with their typically shallower angles, this tends to disrupt the airflow over a larger area of the sail.

The lateen rig was also the ancestor of the Bermuda rig, by way of the Dutch bezaan rig. In the 16th Century, when Spain ruled the Netherlands, Moorish lateen rigs were introduced to Dutch boat builders who soon modified the design by omitting the mast and fastening the lower end of the yard directly to the deck, the yard becoming a raked mast with a full-length, triangular (leg-of-mutton) mainsail aft. Introduced to Bermuda early in the 17th Century, this developed into the Bermuda rig, which has been adopted almost universally for small sailing vessels.

[edit] Modern small boat lateen sails

A Sunfish, which uses a modern lateen rig

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 are 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.

[edit] References

• 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
• [http://www.uhpress.hawaii.edu/journals/jwh/JWH061.html I. C. Campbell. "The Lateen Sail in World History", Journal of World History (University of Hawaii), 6.1 (Spring 1995), pp. 1-23
• "The Development of the Lateen Sail
• Björn Landström, "The Ship" (1961)