The Proa is a two hulled vessel with unequal parallel hulls, superficially similar to an outrigger canoe. Found in many configurations and forms, it was developed as a sailing vessel in Micronesia (Pacific Ocean). The defining feature of a proa is that the vessel switches directions when it changes tacks (stern becomes the bow and vice versa), always keeping the same hull to windward for ballast. This operation is referred to as "shunting". The main hull, or vaka, is usually longer than the windward hull, or ama. Crossbeams called akas connect the vaka to the ama. Traditional proa hulls are aggressively asymmetrical along their length, and often curved in such a way as to produce lift to counteract the lateral forces of the wind. Modern proa hulls are often symmetrical, and will use leeboards for lateral resistance.
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Size and sail plan
The Micronesian proa is found in a a variety of sizes, from the small, canoe-like kor-kor (about 15 feet in length) to the medium sized tipnol (20 to 30 feet), to the tremendous walap (up to 100 feet long). There is also a model proa, called a riwut, that is often raced by children. Proas could be paddled or sailed. The traditional sail used on the proa was the crab-claw sail, which is a delta wing sail relying on vortex lift. The crab-claw sail generates far more lift than the more common triangular sloop sails used on small boats, particularly when reaching. The sloop sail only begins to show an advantage with small angles of attack, such as encountered when beating.
Sailing the proa
When sailing in a strong wind, the crew of the proa act as ballast, providing a force to counteract the torque of the wind acting on the sail. The weight of the crew can provide considerable torque as they move out along the akas towards the ama. A skilled crew will balance the proa so that the ama leaves the water and skims over its surface; this is called "flying the ama", and gives the proa its nickname, the "flying proa". By flying the ama, the wetted surface, and therefore the drag of the proa is significantly reduced. When combined with the long, narrow shape of the vaka, and the large amount of torque the crew can apply on the akas, this gives the proa its large potential speed.
History of the Proa
There has recently been a resurgence in interest in the proa in the Marshall Islands, one of the locations the craft were traditionally built. There is also a loose group of individuals from all over the world with an interest in the proa, both from a historical perspective and from a scientific and engineering perspective. Many of these individuals with interests in proas can be found in the Amateur Yacht Research Society.
The first documented proa built outside of Micronesia was built in 1898 by Commodore Ralph M. Munroe of the Biscayne Bay Yacht Club. It used a symmetric, flat bottomed hull, but otherwise followed the general layout of the Micronesian proa. Only 30 feet long, it was capable of speeds up to 18 knots, and would plane on the flat hull. As this was before the advent of small power boats, this proa was likley the first ever boat capable of planing, and this was what gave it its amazing speed in the days when boats were limited by hull speed. For example, a 30 foot boat that was not capable of planing would be limited by a hull speed of about 7.3 knots; Munroe's proa could reach nearly 2.5 times that speed. This accomplishment was the nautical equivalent to the X-15 breaking the sound barrier.
In a non-traditional variant of the proa, termed the "Atlantic proa", the ama is always sailed to the lee side, and provides buoyancy for stability, rather than ballast as in a traditional proa. Other modern variants of the proa place the bulk of the passenger accommodations on the ama, in an attempt to make the vaka as streamlined as possible.
The terms ama and aka have been adopted by the modern trimaran.
An excellent source of information is the Proa File by Michael Schacht.
Other Types of Sailing Craft
|Classes and types of catamarans, trimarans and multihulls (worldwide list)|
A-Catamaran Dart 15 Dart 16 Dart 18 Hobie 14 Hobie 16 Hobie 17 Hobie 18 Hobie Tiger Proa Tornado Open Ocean Performance Sixties
|Types of sailing vessels and rigs|
Bark | Barque | Barquentine | Bilander | Brig | Brig (Hermaphrodite) | Brigantine | Caravel | Carrack | Catamaran | Catboat | Clipper | Clipper (Dutch Clipper) | Cog | Cutter | Dhow | Fluyt | Fore & Aft Rig | Full Rigged Ship | Gaff Rig | Galleon | Gunter Rig | Hermaphrodite Brig | Junk | Ketch | Mersey Flat | Multihull | Nao | Norfolk Wherry | Pocket Cruiser | Proa | Schooner | Sloop | Smack | Snow | Square Rig | Tall ship | Thames Sailing Barge | Trimaran | Wherry | Wherry (Norfolk) | Windjammer | Xebec | Yacht | Yawl