About Catamarans

catamaran is a multihulled vessel consisting of two parallel hulls of equal size.

A catamaran is geometry-stabilized, that is, it derives its stability from its wide beam, rather than having a ballasted keel like a monohull. Being ballast-free and lighter than a monohull, a catamaran can have a very shallow draught. The two hulls will be much finer than a monohull’s, the reduced drag allowing faster speeds. A sailing multihull will heel much less than a sailing monohull, so its sails spill less wind and are more efficient. The limited heeling means the ride may be more comfortable for passengers and crew, although catamarans can exhibit an unsettling “hobby-horse” motion. Unlike a self-righting monohull, if a gust causes a sailing catamaran to capsize, it may be impossible to right the multihull; but having no ballast, an upturned catamaran will be unlikely to sink.

A catamaran’s two hulls are joined by some structure, the most basic being a frame, formed of akas. More sophisticated catamarans combine accommodation into the bridging superstructure. Catamarans may be driven by sail and/or engine. Originally catamarans were small yachts, but now some ships and ferries have adopted this hull layout because it allows increase speed, stability and comfort.

The catamaran concept is a relative newcomer for Western boat designers, although they have been used since time immemorial among the Dravidian people, inSouth India. Catamarans were developed independently[citation needed] in Oceania, where Polynesian catamarans and outrigger canoes allowed seafaringPolynesians to voyage to the remotest Pacific islands.

In recreational sailing, catamarans and trimarans initially met some skepticism from Western sailors versed in traditional ballasted monohull designs.


The word catamaran is derived from the Tamil word kaṭṭumaram (கட்டுமரம்), literally “tied wood” (from kaṭṭu “to tie” and maram “wood, tree”). A “kattumaram”, a geometry-stabilized rowboat used by the Dravidian people, shares component part-names with the proa, a multihull sailboat used by the Oceanic people. Although the original “kattumaram” included a monohull raft, the modern word catamaran exclusively means a twin-hulled vessel.

In the United States, there are three terms that describe the main components of catamarans and trimarans, namely: “vaka”, “aka”, and “ama”, terms derived from the Malay and Micronesian language group terms for parts of the outrigger canoe. These terms, which reflects only American usage, are unknown in the UK, where simple English words are used instead.

  • Vaka – the canoe or main hull
  • Aka – the framework member that connects the vaka (hull) to the ama (outrigger, or “float”)
  • Ama – the outrigger, connected to the vaka by an aka

In Hawaiian, the main difference is the main hull or canoe is a wa’a pronounced like va ah. There is no plural in Hawaiian and so a double canoe, or two canoes joined together by aka is a wa’a wa’a. An area in lower Puna is called wa’a wa’a. A comprehensive list of Hawaiian words for a boat is published by the Polynesian Voyaging Society.


Polynesian cats

A Polynesian catamaran

While the English adventurer and buccaneer William Dampier was traveling around the world in search of business opportunities, he found himself on the south-western coast of India. He was the first to write in English about a kind of vessel he observed there. It was little more than a raft made of logs.

On the coast of Malabar,” he wrote in 1697, “they call them Catamarans. These are but one Log, or two, sometimes of a sort of light Wood … so small, that they carry but one Man, whose legs and breech are always in the Water.

The vessels described by Dampier are still in use today on the coasts of South India. “kattumaram” literally means logs tied together. Today’s kattumarams have about four logs tied together in a shallow arc to make a raft. The logs are usually from a local, fibrous palm tree. Typically the raft is untied and logs are scattered to dry out before reuse.

Although the name came from Tamil, the one-hull-ballasted sailboat variant is from South Pacific. English visitors applied the Tamil name catamaran to the swift, stable sail and paddle boats made out of two widely separated logs and used by Polynesian natives to get from one island to another.

Older European cats

The larger Hellenistic polyremes (“sixteens”, “twenties”, “thirties” and one “forty”) were most likely double-hulled catamarans.[8] Two such super-galleys built by the Ptolemaic king Ptolemy IV (221–205 BC) have come down to us by name, the Thalamegos and the Tessarakonteres. Catamarans were also used by Greeks engineers under Ptolemy II (283–246 BC) as obelisk carriers:

It was conveyed by Phoenix, who by digging a canal brought the waters of the Nile right up to the place where the obelisk lay. Two very broad ships were loaded with cubes of the samegranite as that of the obelisk, each cube measuring one foot, until calculations showed that the total weight of the blocks was double that of the obelisk, since their total cubic capacity was twice as great. In this way, the ships were able to come beneath the obelisk, which was suspended by its ends from both banks of the canal. Then the blocks were unloaded and the ships, riding high, took the weight of the obelisk. (Pliny, Nat. Hist. 36; 14, 67–68)

Early modern cats

A present sweep row training on catamaran

Early modern Europe’s first documented catamaran was designed by the polymath and Royal Society member William Petty in 1662. It was designed to sail faster, in shallower waters, with less wind & crew than other vessels of the time, but the unusual design met with scepticism and was not a commercial success.design remained relatively unknown in the West for almost another 200 years, until an American, Nathanael Herreshoff, began to build catamaran boats of his own design in 1877 (US Pat. No. 189,459), namely ‘Amaryllis’, which immediately showed her superior performance capabilities, at her maiden regatta (The Centennial Regatta held on June 22, 1876, off the New York Yacht Club’s Staten Island station). It was this same event, after being protested by the losers, where catamarans, as a design, were barred from all the regular classes and they remained barred until the 1970s.

This ban relegated the catamaran to being a mere novelty boat design for many years.

In 1936 Eric de Bisschop built a Polynesian “double canoe” in Hawaii and sailed it home to a hero’s welcome in France. In 1939, he published his book Kaimiloa,which was translated in English in 1940.

In 1947, surfing legend, Woodbridge “Woody” Brown and Alfred Kumalae designed and built the first modern ocean-going catamaran, Manu Kai, in Hawaii. Their young assistant was Rudy Choy, who later founded the design firm Choy/Seaman/Kumalae (C/S/K, 1957) and became a fountainhead for the catamaran movement. The Prout Brothers, Roland and Francis, experimented with catamarans in 1949 and converted their 1935 boat factory in Canvey Island, Essex (England), to catamaran production in 1954. Their Shearwater catamarans won races easily against the monohulls. Yellow Bird a 1953-built Shearwater, raced successfully by Francis Prout in the 1960s, is in the collection of the National Maritime Museum Cornwall. Inspired by de Bisshop’s Kamiloa, in 1955 James Wharram built a utilitarian catamaran and sailed across the Atlantic with a crew of two German girls. In Trinidad he built another one and returned via the North Atlantic, west to east, pioneering catamaran cruising (maritime). James Wharram designs are a reference for simple, not too expensive self-built boats. Not needing a keel catamarans are more suitable for DIY construction.

A Hobie catamaran sailboat

The speed and stability of these catamarans soon made them a popular pleasure craft, with their popularity really taking off in Europe, and was followed soon thereafter in America. Currently, most individually owned catamarans are built in France, South Africa, and Australia.

In 1970 Les Thompson began work in Inverloch, Australia, to single-handedly build the Llinase, a 70-tonne, 24 meter steel ketch motor-sailer which was subsequently launched in 1980. The vessel was able to “walk” up any suitable beach using a shunting system located under the wing and powered by hydraulic rams.

Sailing and transport

Maxi Catamaran Orange II

In the mid-twentieth century, the catamaran inspired an even more popular sailboat, the Beach Cat. In California, a maker of surfboards, Hobie Alter produced the 250-pound in 1967, and two years later the larger and even more successful Hobie 16. That boat remains in production, with more than 100,000 made in the past three decades.
The Tornado catamaran was an Olympic class sailing catamaran since 1976, with a crew of two. It was designed in 1967 by Rodney March of Brightlingsea, England, with help from Terry Pierce, and Reg White, specifically for the purpose of becoming the Olympic catamaran. At the IYRU Olympic Catamaran Trials, it easily defeated the other challengers.

Important builders of transport catamarans are Austal and Incat, both of Australia and best known for building large catamarans both as civilian ferries and as navalvessels.

Usage and application

Faster boats

Catamarans, specifically the multi-hulls, are normally faster than single-hull boats for two reasons : less drag, more power.

  • The major increase in speed over a monohull is due to the hull shape. A monohull with a traditional displacement hull has a quickly building hydrodynamic dragbarrier which set the theoretical hull speed based on square root of “length at waterline”. Catamarans make use of needle like hulls which significantly reduce this wave drag.
  • Catamarans are typically lighter and thus have less displacement (weight). This is because they don’t require a keel counterweight since righting moment is derived from the spacing between multiple hulls.
  • Catamarans have a wider beam (the distance from one side of the boat to the other), which makes them more stable and therefore able to carry more sail area per unit of length than an equivalent monohull.
  • The greater stability means that the sail is more likely to stay upright in a gust, drawing more power than a monohull’s sail which is more likely to heel (lean) over.

A catamaran is most likely to achieve its maximum speed when its forward motion is not unduly disturbed by wave action. This is achieved in waters where the wavelength of the waves is somewhat greater than the waterline length of the hulls, or it is achieved by the design piercing the waves. In either case pitching (rocking horse-like motion) is reduced. This has led to it being said that catamarans are especially favourable in coastal waters, where the often sheltered waters permit the boat to reach and maintain its maximum speed.

An example of an off the beach catamaran is the Ron Given of New Zealand designed Paper Tiger Catamaran

Catamarans’ peculiarities

Although the principles of sailing are the same for both catamarans and monohulls, there are some “peculiarities” to sailing catamarans. For example:

  • Catamarans can be harder to tack if they don’t have dagger boards or centre boards. All sailboats must resist lateral movement in order to sail in directions other than downwind and they do this by either the hull itself or else leeboards (including Bruce foils), dagger boards, centre boards, or other systems like hydrofoils. Also, because catamarans are lighter in proportion to their sail size,[citation needed] they have less momentum to carry them through the turn when they are head to wind. Correct use of the jib sail (back-filling the jib to pull the bow around) is often essential in successfully completing a tack without ending up stuck in irons (pointing dead into the wind and sailing backwards, see: No-Go Zone).
  • Catamarans are slower turning than monohulls as hull spacing is increased and hulls are narrowed to a more needle like shape.
  • Catamarans are less likely to capsize in the classic “beam-wise” manner but often have a tendency to pitchpole instead—where the leeward (downwind) bow sinks into the water and the boat ‘trips’ over forward, leading to a capsize. Other sources state that trimarans are more prone to “pitchpole”, while catamarans can flip sideways. Either way, it is caused by sail overpowering (and not moving weight aft fast enough for smaller vessels). “Trim a monohull for the lull, ride the puff; trim a multihull for the puff, wait the lull”

Teaching for new sailors is usually carried out in monohulls as they are thought easier to learn to sail, a mixture of all the differences mentioned probably contributes to this.

Catamaran sailing

A small Formula 16 sailing catamaran

Small recreational catamarans are typically designed to be launched and landed from a beach. They will come to rest on their keels without heeling over like a monohull. Additionally, their rudders can be retracted to the depth of their keels, which protects the fragile rudders from damage when the vessel is run aground.

Lagoon 380 showing her keels

Larger catamarans make good cruising and long distance boats: The Race (around the world, in 2001) was won by the giant catamaran Club Med skippered by Grant Dalton. It went round the earth in 62 days at an average speed of eighteen knots.

Cruising sail cats

Below a minimum size, about 8 m (24 ft), the catamaran’s hulls do not have enough volume to allow them to be used as living space. At the same time, the bridgedeck area isn’t sufficiently sized to make effective live-aboard space either.

There are a lot of folks doing long-distance offshore cruising in monohull yachts of 9m (30 ft) and less. No responsible designer or multihull sailor would recommend this for a multihull. 12m (40 ft) is the minimum recommended LOA and 15m (50 ft) is preferred. This size allows adequate storage for necessary cruising equipment and still give you a good turn of speed in comfort and safety. … If 15m (50 ft) sounds enormous, remember that the weight of a multihull, of this length, is probably not much more than half the weight of a monohull of the same length and it can be sailed with less crew effort.

While more popular in Europe and Australia, they are gaining popularity in the US as well. These boats can maintain a comfortable 300 nmpd (nautical miles per day) passage, with the racing versions recording well over 400 nmpd. In addition, they don’t heel more than 10-12 degrees, even at full speed on a reach.


One of the biggest developments over the last decade in the yachting arena has been the rise of the super catamaran: a multihull over 100 feet in length.

Various international manufacturers are leading the way in this area including Incat, Blubay, Yapluka, Blue Coast Yachts, Sunreef Yachts, Lagoon and Privilege. Allures, a yacht-catamaran of more than 100 feet was launched in 2007 at Blubay Yachts, France and refitted by Coste Design&Partners. A catamaran of 150 feet in length is under construction at Derektor shipyards in Bridgeport, Connecticut. Coste Design&Partners are preparing a power yacht-catamaran of 203 feet. This project called Event Cat will be a luxury yacht dedicated to corporate and private events. Coste Design&Partners and the designer Jean-Jacques Coste are working on a full range of yachts-catamarans between 80 and more than 200 feet in length.

The emergence of the super or mega catamaran is a relatively new event akin to the rise of the mega or super yacht, used to describe the huge growth in luxurious, large motor yachts on the French Riviera and Floridian Coast.

One of the reasons for increased mega catamaran construction was “The Race”, a circumnavigation challenge which departed from Barcelona, Spain, on New Year’s Eve, 2000. Because of the prize money and prestige associated with this event, four new catamarans (and two highly modified ones) over 100′ in length were built to compete. The largest, “PlayStation”, owned by Steve Fossett, was 125′ long and had a mast which was 147′ above the water. Virtually all of the new mega cats were built of pre-preg carbon fiber for strength and the lowest possible weight. Top speeds of these boats can approach 50 knots.

Fly Bridge Catamarans

The recent trend in the catamaran industry is the Flybridge catamaran. Catamarans for charter usually have a shade over the cockpit that later became a solid fiberglass roof and the charter catamaran Akasha was the first catamaran to arrive with a fly bridge over the cockpit. Today most mega catamarans over 58 feet and above are usually manufactured with a flybridge. The Fly bridge gives height to your position on the water. There are many flybridge catamarans chartering in the Virgin Islands today.

Powered catamarans

Cruising powered cats

A recent development in catamaran design has been the introduction of the power catamaran. The ‘power’ version incorporates the best features of a motor yacht and combines it with the characteristics of a multihull.

Usually, the power catamaran is devoid of any sailing apparatus as demonstrated by one of the top-selling models in the United States, the Lagoon Power 43. This vessel has now been introduced to a number of charter fleets in the Caribbean and the Mediterranean and is becoming an increasingly common sight.

Smaller powered catamarans are becoming quite common in the United States with several manufacturers producing quality boats. A small “cat” will almost certainly have 2 engines while a similar sized mono-hull would only one engine. All mid-size and larger cats will have 2 engines.

The Swiss-registered catamaran Tûranor PlanetSolar which was launched in March 2010, is the world’s largests solar powered boat and has completed the circumnavigation of the globe in 2012.

Passenger transport

The Stena Voyager is a catamaran that provides a fast ferry service across the Irish sea.

An increasing trend is way, who launched the Westamaran design in 1973. The Westamarans, and later designs, some of them consisting of a catamaran hull resting on an air cushion between the hulls, became dominant for all high-speed connections along the Norwegian coast. They could achieve speeds comparable to the hydrofoils that it replaced, and was much more tolerant of foul water and wave conditions.

Since the 1970s, the length of catamarans increased from some 20 m up to 115 m long. The high-speed Stena (HSS) is the world’s largest fast ferry, traveling at a speed of 46 mph, although it is capable of doing over 70 mph.

There is a list of catamaran ferry routes documenting the growing number of routes.

Military cats

HSV-X1 Joint Venture, a large, experimental, high-speed military catamaran.

A military catamaran is being designed for the Us Navy and is in its experimental phase. It is much more resilient and faster than ordinary catamarans.


Basic Catamaran

Two main types of catamaran exist: the regular catamaran and the open catamaran, which features a trampoline between the hulls instead of plating. The normal catamaran multihull, powered or not, consists of two Amas separated by two Akas, which may suspend a platform or trampoline between them. They can be of various sizes and, recently, have become very large.


SWATH type

The Small Waterplane Area Twin Hull (SWATH) is a hull form used for vessels that require a ship of a certain size to handle in rough seas as well as a much larger vessel. An added benefit is a high proportion of deck area for their displacement—in other words, large without being heavy. The SWATH form was invented by Canadian Frederick G. Creed, who presented his idea in 1938 and was later awarded a British patent for it in 1946. It was first used in the 1960s and 1970s as an evolution of catamaran design for use as oceanographic research vessels or submarine rescue ships.

Catamarans provide large, broad decks. It also allows for a design that greatly reduce water resistance (the part that generates waves) by moving as much displacement volume as possible to the lower hull and narrowing the waterline cross-section sharply, creating the distinctive pair of bulbous hulls below the waterline and the narrow struts supporting the upper hull. This design means that the ship’s flotation runs mostly under the waves, like a submarine (the smooth ride of a sub was the inspiration for the design). The result is that a fairly small ship can run very steadily in rough seas. A 50-meter ship can operate at near full power in nearly any direction in waves as high as 12 meters.

The S.W.A.T.H. theory was further developed by Dr Thomas G. Lang, inventor of improvements to the semi-submerged ship (S3) in about 1968. Basically, a SWATH vessel consists of two parallel torpedo like hulls attached to which are two or more streamlined struts which pierce the water surface and support an above water platform. The US Navy commissioned the construction of a SWATH ship called the ‘Kaimalino’ to prove the theory as part of their ship research program. The Kaimalino has been operating successfully in the rough seas off the Hawaiian islands since 1975.


Source wikipedia