A multihull is a boat or ship with more than one hull, whereas a vessel with a single hull is a monohull. The most common multihulls are catamarans, and trimarans. There are other types, with four or more hulls, but such examples are very rare and tend to be specialised for particular functions.
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the water, on ice (iceboat) or on land over a chosen course, which is often part of a larger plan of navigation.
A yacht is a sailing or power vessel used for pleasure, cruising, or racing. There is no standard definition, though the term generally applies to vessels with a cabin intended for overnight use. To be termed a yacht, as opposed to a boat, such a pleasure vessel is likely to be at least 33 feet (10 m) in length and may have been judged to have good aesthetic qualities.
A catamaran is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stabilized craft, deriving its stability from its wide beam, rather than from a ballasted keel as with a monohull boat. Catamarans typically have less hull volume, smaller displacement, and shallower draft (draught) than monohulls of comparable length. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or motors. The catamaran's wider stance on the water can reduce both heeling and wave-induced motion, as compared with a monohull, and can give reduced wakes.
A trimaran is a multihull boat that comprises a main hull and two smaller outrigger hulls which are attached to the main hull with lateral beams. Most modern trimarans are sailing yachts designed for recreation or racing; others are ferries or warships. They originated from the traditional double-outrigger hulls of the Austronesian cultures of Maritime Southeast Asia; particularly in the Philippines and Eastern Indonesia, where it remains the dominant hull design of traditional fishing boats. Double-outriggers are derived from the older catamaran and single-outrigger boat designs.
Proas are various types of multi-hull outrigger sailboats of the Austronesian peoples. The terms were used for native Austronesian ships in European records during the Colonial era indiscriminately, and thus can confusingly refer to the double-ended single-outrigger boats of Oceania, the double-outrigger boats of Island Southeast Asia, and sometimes ships with no outriggers or sails at all.
Waka are Māori watercraft, usually canoes ranging in size from small, unornamented canoes used for fishing and river travel to large, decorated war canoes up to 40 metres (130 ft) long.
Speed sailing is the art of sailing a craft as fast as possible over a predetermined route, and having its overall or peak speed recorded and accredited by a regulatory body. The term usually refers to sailing on water, even though sailing on land and ice is progressively faster because of the lower friction involved. The World Sailing Speed Record Council is the body authorized by the World Sailing to confirm speed records of sailing craft on water.
The 18 ft Skiff is considered the fastest class of sailing skiffs. The class has a long history beginning with races on Sydney Harbour, Australia in 1892 and later in New Zealand. The boat has changed significantly since the early days, bringing in new technology as it became available. Because of the need of strength, agility and skill, the class is considered to be the top level of small boat sailing. Worldwide this boat is called the "18 Foot Skiff". It is the fastest conventional non-foiling monohull on the yardstick rating, with a score of 675, coming only third after the Tornado and Inter 20.
A sailing hydrofoil, hydrofoil sailboat, or hydrosail is a sailboat with wing-like foils mounted under the hull. As the craft increases its speed the hydrofoils lift the hull up and out of the water, greatly reducing wetted area, resulting in decreased drag and increased speed. A sailing hydrofoil can achieve speeds exceeding double and in some cases triple the wind speed.
A wingsail, twin-skin sail or double skin sail is a variable-camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to airplane wings, except that they are designed to provide lift on either side to accommodate being on either tack. Whereas wings adjust camber with flaps, wingsails adjust camber with a flexible or jointed structure. Wingsails are typically mounted on an unstayed spar—often made of carbon fiber for lightness and strength. The geometry of wingsails provides more lift, and a better lift-to-drag ratio, than traditional sails. Wingsails are more complex and expensive than conventional sails.
Wind-powered vehicles derive their power from sails, kites or rotors and ride on wheels—which may be linked to a wind-powered rotor—or runners. Whether powered by sail, kite or rotor, these vehicles share a common trait: As the vehicle increases in speed, the advancing airfoil encounters an increasing apparent wind at an angle of attack that is increasingly smaller. At the same time, such vehicles are subject to relatively low forward resistance, compared with traditional sailing craft. As a result, such vehicles are often capable of speeds exceeding that of the wind.
USA-17 is a sloop rigged racing trimaran built by the American sailing team BMW Oracle Racing to challenge for the 2010 America's Cup. Designed by VPLP Yacht Design with consultation from Franck Cammas and his Groupama multi-hull sailing team, BOR90 is very light for her size being constructed almost entirely out of carbon fiber and epoxy resin, and exhibits very high performance being able to sail at 2.0 to 2.5 times the true wind speed. From the actual performance of the boat during the 2010 America's Cup races, it can be seen that she could achieve a velocity made good upwind of over twice the wind speed and downwind of over 2.5 times the wind speed. She can apparently sail at 20 degrees off the apparent wind. The boat sails so fast downwind that the apparent wind she generates is only 5-6 degrees different from that when she is racing upwind; that is, the boat is always sailing upwind with respect to the apparent wind. An explanation of this phenomenon can be found in the article on sailing faster than the wind.
High-performance sailing is achieved with low forward surface resistance—encountered by catamarans, sailing hydrofoils, iceboats or land sailing craft—as the sailing craft obtains motive power with its sails or aerofoils at speeds that are often faster than the wind on both upwind and downwind points of sail. Faster-than-the-wind sailing means that the apparent wind angle experienced on the moving craft is always ahead of the sail. This has generated a new concept of sailing, called "apparent wind sailing", which entails a new skill set for its practitioners, including tacking on downwind points of sail.
The J/80 is an American trailerable sailboat that was designed by Rod Johnstone as a one design racer and first built in 1992.
Forces on sails result from movement of air that interacts with sails and gives them motive power for sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and sail-powered land vehicles. Similar principles in a rotating frame of reference apply to windmill sails and wind turbine blades, which are also wind-driven. They are differentiated from forces on wings, and propeller blades, the actions of which are not adjusted to the wind. Kites also power certain sailing craft, but do not employ a mast to support the airfoil and are beyond the scope of this article.
The AC72 is a class of wingsail catamarans built to a box rule, which governs the construction and operation of yachts competing in the 2013 Louis Vuitton and the America's Cup races. The class was subsequently replaced by the smaller AC50 class.
Miss Nylex is a C-Class racing catamaran, designed and built in Australia in the 1970s specifically to compete in the International Catamaran Challenge Trophy (ICCT). It has a single wingsail with two aerodynamic flaps, instead of the conventional mast and sail combination.
The AC75 is a racing yacht used in the 2021 America's Cup match and planned to be used for the 37th America's Cup and 38th America's Cup matches. The 23 m (75 ft) monohulls feature wing-like sailing hydrofoils mounted under the hull, a soft wingsail, and no keel.
Polynesian multihull terminology, such as "ama", "aka" and "vaka" are multihull terms that have been widely adopted beyond the South Pacific where these terms originated. This Polynesian terminology is in common use in the Americas and the Pacific but is almost unknown in Europe, where the Anglo-Saxon terms "hull" and "outrigger" form normal parlance. Outriggers, catamarans, and outrigger boats are a common heritage of all Austronesian peoples and predate the Micronesian and Polynesian expansion into the Pacific. They are also the dominant forms of traditional ships in Island Southeast Asian and Malagasy Austronesian cultures, where local terms are used.
