# Catamaran

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A catamaran () (informally, a "cat") 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.

## Contents

Catamarans were invented by the Austronesian peoples which enabled their expansion to the islands of the Indian and Pacific Oceans. [1]

Catamarans range in size from small (sailing or rowing vessels) to large (naval ships and roll-on/roll-off car ferries). The structure connecting a catamaran's two hulls ranges from a simple frame strung with webbing to support the crew to a bridging superstructure incorporating extensive cabin and/or cargo space.

## History

Catamarans from Oceania and Maritime Southeast Asia became the inspiration for modern catamarans. Until the 20th century catamaran development focused primarily on sail-driven concepts.

### Etymology

The word "catamaran" is derived from the Tamil word, kattumaram (கட்டுமரம்), which means "logs bound together". However, the original kattumaram did not refer to double-hulled boats at all, but to a type of single-hulled raft of the Tamil people made of three to seven tree trunks lashed together. The term has evolved in English usage to refer solely to unrelated double-hulled boats. [2] [3] [4] [5] [6] [7] [8]

### Development in Oceania and Asia

Catamaran-type vessels were an early technology of the Austronesian peoples. Early researchers like Heine-Geldern (1932) and Hornell (1943) once believed that catamarans evolved from outrigger canoes, but modern authors specializing in Austronesian cultures like Doran (1981) and Mahdi (1988) now believe it to be the opposite. [9] [10] [1]

Two canoes bound together developed directly from minimal raft technologies of two logs tied together. Over time, the double-hulled canoe form developed into the asymmetric double canoe, where one hull is smaller than the other. Eventually the smaller hull became the prototype outrigger, giving way to the single outrigger canoe, then to the reversible single outrigger canoe. Finally, the single outrigger types developed into the double outrigger canoe (or trimarans). [9] [10] [1]

This would also explain why older Austronesian populations in Island Southeast Asia, Madagascar, and the Comoros tend to favor double outrigger canoes, as it keeps the boats stable when tacking. But they still have small regions where catamarans and single-outrigger canoes are still used. In contrast, more distant outlying descendant populations in Micronesia and Polynesia retained the double-hull and the single outrigger canoe types, but the technology for double outriggers never reached them (although it exists in western Melanesia). To deal with the problem of the instability of the boat when the outrigger faces leeward when tacking, they instead developed the shunting technique in sailing, in conjunction with reversible single-outriggers. [9] [10] [1] [11] [12]

Despite their being the more "primitive form" of outrigger canoes, they were nonetheless effective, allowing seafaring Polynesians to voyage to distant Pacific islands. [13]

The following is a list of traditional Austronesian catamarans:

### Western development

The first documented example of double-hulled sailing craft in Europe was designed by William Petty in 1662 to sail faster, in shallower waters, in lighter wind, and with fewer crew than other vessels of the time. However, the unusual design met with skepticism and was not a commercial success. [14] [15]

The design remained relatively unused in the West for almost 160 years until the early 19th-century, when the Englishman Mayflower F. Crisp built a two-hulled merchant ship in Rangoon, Burma. The ship was christened Original. Crisp described it as "a fast sailing fine sea boat; she traded during the monsoon between Rangoon and the Tenasserim Provinces for several years". [16] [17]

Later that century, the American Nathanael Herreshoff constructed a double-hulled sailing boat of his own design (US Pat. No. 189,459). [18] The craft, Amaryllis, raced at her maiden regatta on June 22, 1876, and performed exceedingly well. Her debut demonstrated the distinct performance advantages afforded to catamarans over the standard monohulls. It was as a result of this event, the Centennial Regatta of the New York Yacht Club, that catamarans were barred from regular sailing classes, and this remained the case until the 1970s. [19] On June 6, 1882, three catamarans from the Southern Yacht Club of New Orleans raced a 15nm course on Lake Pontchartrain and the winning boat in the catamaran class, Nip and Tuck, beat the fastest sloop's time by over five minutes. [20] [21]

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 experiences in a book, Kaimiloa, which was translated into English in 1940. [22]

Roland and Francis Prout experimented with catamarans in 1949 and converted their 1935 boat factory in Canvey Island, Essex (England), to catamaran production in 1954. Their Shearwater catamarans easily won races against monohulls. Yellow Bird, a 1956-built Shearwater III , raced successfully by Francis Prout in the 1960s, is in the collection of the National Maritime Museum Cornwall. [23] Prout Catamarans, Ltd. designed a mast aft rig with the mast aft of midships to support an enlarged jib—more than twice the size of the design's reduced mainsail; it was produced as the Snowgoose model. [24] The claimed advantage of this sail plan was to diminish any tendency for the bows of the vessel to dig in. [25] [26]

In the mid-twentieth century, beachcats became a widespread category of sailing catamarans, owing to their ease of launching and mass production. In California, a maker of surfboards, Hobie Alter, produced the 250-pound (110 kg) Hobie 14 in 1967, and two years later the larger and even more successful Hobie 16. As of 2016, the Hobie 16 was still being produced with more than 100,000 having been manufactured. [27]

Catamarans were introduced to Olympic sailing in 1976. The two-handed Tornado catamaran was selected for the multihull discipline in the Olympic Games from 1976 through 2008. It was redesigned in 2000. [28] The foiling Nacra 17 will be used in the Tokyo 2020 Olympics, [29] [30] after the 2015 adoption of the Nacra 15 as a Youth World Championships class and as a new class for the Youth Olympic Games. [31] [32]

Australia became the site of builders of large transport catamarans—Incat in 1977 [33] and Austal in 1988 [34] —each building civilian ferries and naval vessels.

The largest ship ever built in terms of gross tonnage, the Pioneering Spirit, incorporates a catamaran design. [35]

## Performance

Catamarans have two distinct primary performance characteristics that distinguish them from displacement monohull vessels: lower resistance to passage through the water and greater stability (initial resistance to capsize). Choosing between a monohull and catamaran configuration includes considerations of carrying capacity, speed, and efficiency.

### Resistance

At low to moderate speeds, a lightweight catamaran hull experiences resistance to passage through water that is approximately proportional to the square of its speed. A displacement monohull, by comparison, experiences resistance that is at least the cube of its speed. This means that a catamaran would require four times the power in order to double its speed, whereas a monohull would require eight times the power to double its speed, starting at a slow speed. [36] For powered catamarans, this implies smaller power plants (although two are typically required). For sailing catamarans, low forward resistance [37] allows the sails to derive power from attached flow, [38] their most efficient mode—analogous to a wing—leading to the use of wingsails in racing craft. [39]

### Stability

Catamarans rely primarily on form stability to resist heeling and capsize. [36] Comparison of heeling stability of a rectangular-cross section monohull of beam, B, compared with two catamaran hulls of width B/2, separated by a distance, 2×B, determines that the catamaran has an initial resistance to heeling that is seven times that of the monohull. [40] Compared with a monohull, a cruising catamaran sailboat has a high initial resistance to heeling and capsize—a fifty-footer requires four times the force to initiate a capsize than an equivalent monohull. [41]

One measure of the trade-off between speed and carrying capacity is the displacement Froude number (FnV), [42] compared with calm water transportation efficiency. [43] FnV applies when the waterline length is too speed-dependent to be meaningful—as with a planing hull. [44] It uses a reference length, the cubic root of the volumetric displacement of the hull, V, where u is the relative flow velocity between the sea and ship, and g is acceleration due to gravity:

${\displaystyle \mathrm {Fn_{V}} ={\frac {u}{\sqrt {gV^{1/3}}}}}$

Calm water transportation efficiency of a vessel is proportional to the full-load displacement and the maximum calm-water speed, divided by the corresponding power required. [45]

Large merchant vessels have a FnV between one and zero, whereas higher-performance powered catamarans may approach 2.5—denoting a higher speed per unit volume for catamarans. Each type of vessel has a corresponding calm water transportation efficiency, with large transport ships being in the range of 100–1,000, compared with 11-18 for transport catamarans—denoting a higher efficiency per unit of payload for monohulls. [43]

## SWATH and wave-piercing designs

Two advances over the traditional catamaran are the small-waterplane-area twin hull (SWATH) and the wave-piercing configuration—the latter having become a widely favored design.

SWATH reduces wave-generating resistance by moving displacement volume below the waterline, using a pair of tubular, submarine-like hulls, connected by pylons to the bridge deck with a narrow waterline cross-section. The submerged hulls are minimally affected by waves. [46] 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. [47] In 1990, the US Navy commissioned the construction of a SWATH ship to test the configuration. [48]

SWATH vessels compare with conventional powered catamarans of equivalent size, as follows: [46]

• Larger wetted surface, which causes higher skin friction drag
• Significant reduction in wave-induced drag, with the configuration of struts and submerged hull structures
• Lower water plane area significantly reduces pitching and heaving in a seaway
• No possibility of planing
• Higher sensitivity to loading, which may bring the bridge structure closer to the water

Wave-piercing catamarans employ a low-buoyancy bow on each hull that is pointed at the water line and rises aft, up to a level, to allow each hull to pierce waves, rather than ride over them. This allows higher speeds through waves than for a conventional catamaran. They are distinguished from SWATH catamarans, in that the buoyant part of the hull is not tubular. The spanning bridge deck may be configured with some of the characteristics of a normal V-hull, which allows it to penetrate the crests of waves. [49]

Wave-piercing catamaran designs have been employed for yachts, [50] passenger ferries, [51] and military vessels. [52]

## Applications

Technological advances catamerans have over traditional monohull craft include foils that lift racing catamarans out of the water, capacious and stable cruising vessels, and racers that have achieved average speeds on the open ocean, comparable to much larger vessels. A catamaran configuration fills a niche where speed and sea-kindliness is favored over bulk capacity. In larger vessels, this niche favors car ferries and military vessels for patrol or operation in the littoral zone.

### Sport

Recreational and sport catamarans typically are designed to have a crew of two and be launched and landed from a beach. Most have a trampoline on the bridging structure, a rotating mast and full-length battens on the mainsail. Performance versions often have trapezes to allow the crew to hike out and counterbalance capsize forces during strong winds on certain points of sail. [53]

For the 33rd America's Cup, both the defender and the challenger built 90-foot (27 m) long multihulls. Société Nautique de Genève, defending with team Alinghi, sailed a catamaran. The challenger, BMW Oracle Racing, used a trimaran, replacing its soft sail rig with a towering wing sail—the largest sailing wing ever built. In the waters off Valencia, Spain in February 2010, the BMW Oracle Racing trimaran with its powerful wing sail proved to be superior. This represented a break from the traditional monohulls that had always been sailed in previous America's Cup series. [54]

On San Francisco Bay, the 2013 America's Cup was sailed in 72-foot (22 m) long AC72 catamarans (craft set by the rules for the 2013 America's Cup). Each yacht employed hydrofoils and a wing sail. The regatta was won 9-8 by Oracle Team USA against the challenger, Emirates Team New Zealand, in fifteen matches because Oracle Team USA had started the regatta with a two-point penalty. [55] [56]

Yachting has seen the development of multihulls over 100 feet (30 m) in length. "The Race" helped precipitate this trend; it was 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 feet (30 m) in length were built to compete. The largest, PlayStation , owned by Steve Fossett, was 125 feet (38 m) long and had a mast which was 147 feet (45 m) above the water. Virtually all of the new mega-cats were built of pre-preg carbon fiber for strength and the lowest possible weight. The top speeds of these boats can approach 50 knots (58 mph; 93 km/h). The Race was won by the 33.50 m (109.9 ft)-long catamaran Club Med skippered by Grant Dalton. It went round the globe in 62 days at an average speed of 18 knots (21 mph; 33 km/h). [57]

Whitewater catamaran—sometimes called "cata-rafts"—for whitewater sports are widely spread in post-Soviet countries. They consists of two inflatable hulls connected with a lattice scaffold. The frame of the tourist catamaran can be made of both aluminum (duralumin) pipes and from felled tree trunks. The inflatable part has two layers—an airtight balloon with inflation holes and a shell made of dense tissue, protecting the balloon from mechanical damage. Advantages of such catamarans are light weight, compactness and convenience in transportation (the whole product is packed in one pack-backpack, suitable for air traffic standards) and the speed of assembly (10–15 minutes for the inflation). [58] All-inflatable models are available in North America. [59] A cata-raft design has been used on the Colorado River to handle heavy whitewater, yet maintain a good speed through the water. [60]

### Cruising

Cruising sailors must make trade-offs among volume, useful load, speed, and cost in choosing a boat. Choosing a catamaran offers increased speed at the expense of reduced load per unit of cost. Howard and Doane describe the following tradeoffs between cruising monohulls and catamarans: [41] A long-distance, offshore cruising monohull may be as short as 30 feet (9.1 m) for a given crew complement and supporting supplies, whereas a cruising catamaran would need to be 40 feet (12 m) to achieve the same capacity. In addition to greater speed, catamarans draw less water than do monohulls—little as 3 feet (0.91 m)—and are easier to beach. Catamarans are harder to tack and take up more space in a marina. Cruising catamarans entail added expense for having two engines and two rudders. Tarjan adds that cruising catamarans boats can maintain a comfortable 300 nautical miles (350 mi; 560 km) per day passage, with the racing versions recording well over 400 nautical miles (460 mi; 740 km) per day. In addition, they do not heel more than 10-12 degrees, even at full speed on a reach. [61]

Powered cruising catamarans share many of the amenities found in a sail cruising catamaran. The saloon typically spans two hulls wherein are found the staterooms and engine compartments. As with sailing catamarans, this configuration minimizes boat motion in a seaway. [62]

The Swiss-registered wave-piercing catamaran, Tûranor PlanetSolar , which was launched in March 2010, is the world's largest solar powered boat. It completed a circumnavigation of the globe in 2012. [63]

### Passenger transport

The 1970s saw the introduction of catamarans as high-speed ferries, as pioneered by Westermoen Hydrofoil in Mandal, Norway, which launched the Westamaran design in 1973. [64] The Stena Voyager was an example of a large, fast ferry, typically traveling at a speed of 46 miles per hour (74 km/h), although it was capable of over 70 miles per hour (110 km/h). [65]

### Military

Military Sealift Command operates several Expeditionary Fast Transport catamarans owned by the U.S. Navy. [66] They are used for high speed transport of military cargo, and to get into shallow ports.

The Makar-class is a class of two large catamaran-hull survey ships built for the Indian Navy. As of 2012, one vessel, INS Makar (J31), was in service and the second was under construction. [67]

First launched in 2004 at Shanghai, the Houbei class missile boat of the People's Liberation Army Navy (PLAN) has a catamaran design to accommodate the vessel's stealth features. [68]

## Related Research Articles

A multihull is a ship or boat with more than one hull, whereas a vessel with a single hull is a monohull.

A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying goods or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boats, based on size, shape, load capacity, and tradition. In the Age of Sail a "ship" was a sailing vessel defined by its sail plan of at least three square riged masts and a full bowsprit.

A yacht is a sail or power vessel used for pleasure, cruising, or racing. There is no standard definition, so the term applies to such vessels that have a cabin with amenities that accommodate 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 have been judged to have good aesthetic qualities.

A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.

A sail plan is a description of the specific ways that a sailing craft is rigged, as discussed below. Also, the term “sail plan” is a graphic depiction of the arrangement of the sails for a given sailing craft.

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.

An outrigger is a projecting structure on a boat, with specific meaning depending on types of vessel. Outriggers may also refer to legs on a wheeled vehicle that are folded out when it needs stabilization, for example on a crane that lifts heavy loads.

A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another.

Outrigger boats are various watercraft featuring one or more lateral support floats known as outriggers, which are fastened to one or both sides of the main hull. They can range from small dugout canoes to large plank-built vessels. Outrigger boats can also vary in their configuration, from the ancestral double-hull configuration (catamarans), to single-outrigger vessels prevalent in the Pacific Islands and Madagascar, to the double-outrigger vessels (trimarans) prevalent in Island Southeast Asia. They are traditionally fitted with Austronesian sails, like the crab claw sails and tanja sails, but in modern times are often fitted with petrol engines.

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.

Capsizing or keeling over occurs when a boat or ship is turned on its side or it is upside down in the water. The act of reversing a capsized vessel is called righting.

The Hobie Cat is a small sailing catamaran manufactured by the Hobie Cat Company. Hobie's line of products includes surfboards, sailboats, kayaks, stand-up paddle boards, and pedalboards, although the Hobie Cat Company is known worldwide for its catamarans. Hobie also designed a successful monohull, the Hobie 33.

A beachcat is an off-the-beach class of catamaran ("cat") sailboat.

In dinghy sailing, a boat is said to be turtling or to turn turtle when the boat is fully inverted with the mast pointing down to the lake bottom or seabed. The name stems from the appearance of the upside-down boat, similar to the carapace, that is the top shell of a sea turtle. The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats. Relative to monohulls, it is more hazardous on multihulls, because of their inherent stability in an inverted position. Measures can be taken to prevent a capsize from becoming a turtle.

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 twice the wind speed.

A sailing yacht, is a leisure craft that uses sails as its primary means of propulsion. A yacht may be a sail or power vessel used for pleasure, cruising, or racing. There is no standard definition, so the term applies here to sailing vessels that have a cabin with amenities that accommodate overnight use. To be termed a "yacht", as opposed to a "boat", such a vessel is likely to be at least 33 feet (10 m) in length and have been judged to have good aesthetic qualities. Sailboats that do not accommodate overnight use or are smaller than 30 feet (9.1 m) are not universally called yachts. Sailing yachts in excess of 130 feet (40 m) are generally considered to be superyachts.

Traditionally, many different kinds of boats have been used as fishing boats to catch fish in the sea, or on a lake or river. Even today, many traditional fishing boats are still in use. According to the United Nations Food and Agriculture Organization (FAO), at the end of 2004, the world fishing fleet consisted of about 4 million vessels, of which 2.7 million were undecked (open) boats. While nearly all decked vessels were mechanised, only one-third of the undecked fishing boats were powered, usually with outboard engines. The remaining 1.8 million boats were traditional craft of various types, operated by sail and oars.

James Wharram is a multihull pioneer and designer of catamarans.

Kaep is a traditional type of double-ended Proa sailboat native to Palau. Some of the essential design elements have also been adopted as a modern smaller multihull prototype variant.

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.

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