Added: 12/12/2005 |
Multihull models are able to sail in shallower waterA multihull is a sailing ship with more than one hull. The additional hulls provide stability, typically to hold the vessel upright against the sideways force of the wind on the sails. This is in contrast to monohulls which typically use a keel and/or ballast for this purpose.
Multihull models include: proas, which have two differently sized hulls; catamarans, which have two similar hulls; and trimarans, which have a larger hull in the center and two smaller ones on either side. Multihull sailboats are typically much wider than the equivalent monohull, which allows them to carry no ballast, so they are typically faster than monohulls under equivalent conditions It also means that multihulls are less prone to sink than monohulls when their hulls are compromised. There are also power multihull models, both for racing and transportation.
A 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). What distinguish a proa from the other multihull models 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.
A catamaran consists of two hulls joined by a frame. Catamarans can be sail- or motor-powered. The word catamaran comes from the Tamil language, in which the word kattumaram means "logs bound together". The catamaran was the invention of the paravas, an aristocratic fishing community in the southern coast of Tamilnadu, India.
Catamarans are a relatively recent design of boat for both leisure and sport sailing, although they have been used for millennia in Oceania, where Polynesian catamarans allowed seafaring Polynesians to settle the world's most far-flung islands. Catamarans have been met by a degree of scepticism from some sailors accustomed to more "traditional" designs.
A trimaran is a multihull boat consisting of a main hull and two smaller outrigger hulls (amas), attached to the main hull with lateral struts (akas).
The first trimarans were built by indigenous Polynesians almost 4,000 years ago, and much of the current terminology is inherited from them. Multihull sailboats (catamarans and trimarans) gained favor during the 1960s and 1970s. Modern recreational trimarans are rooted in the same homebuilt tradition as other multihulls, though there are a number of production models now on the market, such as the folding, trailerable trimarans from Corsair Marine, Quorning Boats, Performance Cruising Inc., and Ian Farrier.
The trimaran design is also becoming more widespread as a passenger ferry. Designs which can carry over 300 cars are now in production. The trimaran concept has also been considered for modern warships.
Trimarans have a number of advantages over comparable monohulls (conventional, single-hulled sailboats). Given two boats of the same length, the trimaran has a shallower draft, a wider beam, less hull area, and is able to fly more sail area. In addition, because of the wide beam, trimarans do not need the weighted keel required in monohulls. As a result, the trimaran offers much better straight-line performance than a monohull, is able to sail in shallower water, and maintains its stability in stronger winds. However, its wider beam makes it a little more cumbersome to maneuver, so tacking and jibing can be trickier, and the narrower hulls provide less living space than an equivalently-sized monohull.
There are many types of multihull boats in different categories. Among the small sailing catamarans, also called beach catamarans, the most recognized racing classes are the Hobie Cat 16, Formula 18 cats, A-cats and the olympic multihull called Tornado.
Larger boats include Corsair Marine (mid-sized trimarans), and Privilege (large, luxurious catamarans). But also the much larger French trimarans of the ORMA racing cirquit and round the world record attemps are included in this.
In the powerboat part of the multihull spectrum we find a range of boats from small single pilot Formula 1 power boat series to the large multi-engined or even gas turbined power boats that are used in the off-shore powerboat racing series and that are piloted by 2 to 4 pilots.
All the multihull models are substantially faster than monohulls, because the absence of ballast reduces their weight and the amount of drag through the water considerably, without reducing the amount of sail that they can carry, and because the waterline to width ratio is so large.
Multihulls are quite popular for racing, especially in Europe and Australia, and are somewhat popular for cruising in the Caribbean. They're not seen very often in the United States, although they're gradually getting more popular. Until the 1980s most multihull sailboats (except for beach cats) were built either by their owners or by boatbuilders on a semi-custom basis. Since then several companies have been successful selling mass-produced (by boat industry standards) boats.
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