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 increased 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, in South India. Catamarans were developed independently in Oceania, where Polynesian catamarans and outrigger canoes allowed seafaring Polynesians to voyage to the remotest Pacific islands.
- 1 Multihull component terms
- 2 History
- 3 Usage and application
- 4 Powered catamarans
- 5 Variations
- 6 See also
- 7 Notes
- 8 Bibliography
- 9 External links
Multihull component terms
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 Tamil 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.
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. 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 same granite 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
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. The design remained relatively unknown in the West for almost another 160 years, until the 1820s or 1830s, when Englishman May Flower Crisp built a two-hulled merchant ship called "Original" at Rangoon. Crisp described it as "a fast sailing fine sea boat; she traded during the monsoon between Rangoon and the Tenasserim Provinces for several years".
Later, 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.
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
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.
Usage and application
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 drag barrier 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
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, 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.
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.
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.
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.
An increasing trend is the deployment of a catamaran as a high-speed ferry. The use of catamaran for high-speed passenger transport was pioneered by Westermoen Hydrofoil in Mandal, Norway, 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.
A military catamaran is being designed for the U.S. Navy and is in its experimental phase. It is much more resilient and faster than ordinary catamarans.
The Alcock Ashdown Class is a class of 6 large catamaran hull survey ships being built for the Indian Navy. One ship INS Makar (J31) is in service from 2012 and 5 more under various stages of construction.
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.
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.
Pontoon boat or hydroairy ship
The hydroairy ship appears to be nothing more than an upgraded and enlarged pontoon boat with a formed and shaped underplatform. The general architecture is identical, consisting of two flotation chambers, for the Amas, joined by a load carrying platform, which carries the superstructure.
Invented in 1952 by a Minnesota farmer, in the rural town of Richmond, MN. Ambrose Weeres had an idea that if you put a wooden deck on top of two columns of steel barrels welded together end to end, you would have a sturdy deck that would be more stable on a lake than a conventional boat. This was Ambrose Weeres, walking the same idea paths as the early Polynesians, while proving that the ideas behind the multihull are not all that counter-intuitive.
These sorts of boats are cheap and easy to make, require no ballast, and thus have good performance. Although this design is almost exclusively restricted to power boats, it is still essentially a catamaran. No displacement is lost towards ballast, therefore yielding huge operational efficiencies.
One factor following the rise of popularity in catamarans is the popularity of catamaran "kits". Most popular are materials such as woven fibreglass fabrics and foam, balsa or paper-honeycomb cores. These materials are pressed to create "panels" which are then often cut to specific shapes and parts for construction by amateurs or professionals.
|Wikimedia Commons has media related to Catamarans.|
- Hawaii Superferry
- International Catamaran Challenge Trophy
- International C-Class Catamaran Championship
- SWATH, another twin hull design
- The Hirondelle
- Turtling (sailing)
- James Wharram
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- Multiblog is the catamaran's blog !
- Catamaran Sailing at TheBeachcats.com Site devoted to all types of small catamarans known as beachcats.
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- Multihulls World Catamarans aficionados magazine
- Transporting A Catamaran Pictorial of transporting a 32 foot catamaran over land