Crab claw sail

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Traditional Austronesian generalized sail types. C, D, E, and F are types of crab-claw sails.
Double sprit (Sri Lanka)
Common sprit (Philippines)
Oceanic sprit (Tahiti)
Oceanic sprit (Marquesas)
Oceanic sprit (Philippines)
Crane sprit (Marshall Islands)
Rectangular boom lug (Maluku Islands)
Square boom lug (Gulf of Thailand)
Trapezial boom lug (Vietnam) Austronesian Sail Types.png
Traditional Austronesian generalized sail types. C, D, E, and F are types of crab-claw sails.

The crab claw sail is a fore-and-aft triangular sail with spars along upper and lower edges. The crab claw sail was first developed by the Austronesian peoples some time around 1500 BC. It is used in many traditional Austronesian cultures in Island Southeast Asia, Micronesia, Island Melanesia, Polynesia, and Madagascar. [2] Due to its extraordinary performance and ease-of-operation, it has also become very popular in modern sport sailing. [3] It is sometimes known as the Oceanic lateen or the Oceanic sprit, even though it is not restricted to Oceania, is neither a lateen sail nor a spritsail, and has an independent older origin.

Contents

History

Crab-claw sails were invented by the Austronesians somewhere in Island Southeast Asia at no later than 1500 BCE. It spread with the Austronesian migration to Micronesia, Island Melanesia, Madagascar, and Polynesia. It may have also caused the unique development of outrigger boat technology due to the necessity for stability once crab claw sails were attached to small watercraft. [4] Crab claw sails can be used for double-canoe (catamaran), single-outrigger (on the windward side), or double-outrigger boat configurations, in addition to monohulls. [2] [5]

Malagasy lakana with a basic crab claw sail Madagascar - Traditional fishing pirogue.jpg
Malagasy lakana with a basic crab claw sail

Crab claw sails are rigged fore-and-aft and can be tilted and rotated relative to the wind. They evolved from "V"-shaped perpendicular square sails in which the two spars converge at the base of the hull. The simplest form of the crab claw sail (also with the widest distribution) is composed of a triangular sail supported by two light spars (sometimes erroneously called "sprits") on each side. They were originally mastless, and the entire assembly was taken down when the sails were lowered. [4] There are several distinct types of crab claw rigs, but unlike western rigs, they do not have fixed conventional names. [6]

1846 illustration of a Fijian camakau, a single-outrigger canoe with a canted mast "crane sprit"-type crab claw sail Atlas pittoresque pl 096.jpg
1846 illustration of a Fijian camakau , a single-outrigger canoe with a canted mast "crane sprit"-type crab claw sail

The need to propel larger and more heavily laden boats led to the increase in vertical sail. However this introduced more instability to the vessels. In addition to the unique invention of outriggers to solve this, the sails were also leaned backwards and the converging point moved further forward on the hull. This new configuration required a loose "prop" in the middle of the hull to hold the spars up, as well as rope supports on the windward side. This allowed more sail area (and thus more power) while keeping the center of effort low and thus making the boats more stable. The prop was later converted into fixed or removable canted masts where the spars of the sails were actually suspended by a halyard from the masthead. This type of sail is most refined in Micronesian proas which could reach very high speeds. These configurations are sometimes known as the "crane sprit" or the "crane spritsail". Micronesian, Island Melanesian, and Polynesian single-outrigger vessels also used this canted mast configuration to uniquely develop shunting, where canoes are symmetrical from front to back and change end-to-end when sailing against the wind. [4] [6]

The conversion of the prop to a fixed mast led to the much later invention of the tanja sail (also known variously and misleadingly as the canted square sail, canted rectangular sail, boomed lugsail, or balance lugsail). Tanja sails were rigged similarly to crab claw sails and also had spars on both the head and the foot of the sails; but they were square or rectangular with the spars not converging into a point. [4] [6]

Hokule'a in 2009, with crab claw sails where the upper spars also function as fixed masts Hokule'aSailing2009.jpg
Hokule'a in 2009, with crab claw sails where the upper spars also function as fixed masts

Another evolution of the basic crab claw sail is the conversion of the upper spar into a fixed mast. In Polynesia, this gave the sail more height while also making it narrower, giving it a shape reminiscent of crab pincers (hence "crab claw" sail). This was also usually accompanied by the lower spar becoming more curved. [4] [6]

Austronesians traditionally made their sails from woven mats of the resilient and salt-resistant pandanus leaves. These sails allowed Austronesians to embark on long-distance voyaging. In some cases, however, they were one-way voyages. The failure of pandanus to establish populations in Easter Island and New Zealand is believed to have isolated their settlements from the rest of Polynesia. [7] [8]

Because of the crab claw sail's more ancient origin, there is also a hypothesis that contact between Arabs and Austronesians in their Indian Ocean voyages may have influenced the development of the triangular Arabic lateen sail; and in return Arab square-shaped sails may have influenced the development of the Austronesian rectangular tanja sail of western Southeast Asia. [9] Others, however, believe that the tanja sail was an indigenous invention of Southeast Asian Austronesians, though they also believe that the lateen sail may have been introduced to Arab sailors via contact with Austronesian crab claw sails. [10] [11] [12] A third theory however, concludes that lateen sails were originally Mediterranean and that Portuguese sailors introduced the lateen sail to Asian waters, starting with Vasco da Gama's arrival in India in 1500. This means that the development of lateen sails in western sailors were not influenced by the crab claw sail. [13] :257f

In Indonesia, crab claw sail appeared as a recent development. Traditionally the people from Nusantara archipelago use the tanja sail, but starting in the 19th century the Madurese people developed the lete sail. "Lete" actually means lateen, but the existence of pekaki (lower spar/boom) indicates that the layar lete is crab claw sail. [14]

Construction

Crab claw sail being constructed for Hot Buoys trimaran. Notice pocket in right hand edge of sail to hold spar. Second spar in this particular configuration is not required since a bolt-rope holds the sail's upper edge and the mast is located in the back of the sailboat. Note lack of shaping. Smaller Crab Claw Sail.JPG
Crab claw sail being constructed for Hot Buoys trimaran. Notice pocket in right hand edge of sail to hold spar. Second spar in this particular configuration is not required since a bolt-rope holds the sail's upper edge and the mast is located in the back of the sailboat. Note lack of shaping.

The crab claw sail consists of a sail, approximately an isosceles triangle in shape. The equal length sides are usually longer than the third side, with spars along the long sides.

The crab claw may also traditionally be constructed with curved spars, giving the edges of the sail along the spars a convex shape, while the leech of the sail is often quite concave to keep it stiff on the trailing edge. These features give it its distinct, claw-like shape. Modern crab claws generally have straighter spars and a less convex leech, which gives more sail area for a given length of spar. Spars may taper towards the leech. The structure helps the sail to spill gusts.

The crab claw characteristically widens upwards, putting more sail area higher above the ocean, where the wind is stronger and steadier. This increases the heeling moment: the sails tend to blow the watercraft over. For this reason, crabclaws are typically used on multihulls, which resist heeling more strongly.

The sail is shunted; the bow becomes the stern, and the mast rake is also reversed. The vessel therefore always has the ama (and sidestay, if there is one) to windward, and has no bad tack

Proa

In a proa, the forward intersection of the spars is placed towards the bow. The sail is supported by a short mast attached near the middle of the upper spar, and the forward corner is attached to the hull. The lower spar, or boom, is attached at the forward intersection, but is not attached to the mast. The proa has a permanent windward and leeward side, and exchanges one end for the other when coming about.

To tack, or switch directions across the wind, the forward corner of the sail is loosened and then transferred to the opposite end of the boat, a process called shunting. [15] To shunt, the proa's sheet is let out. The joined corner of the spars is then transferred to the opposite end of the boat. While remaining attached to the top of the mast, the upper spar tilts to vertical and beyond as the forward corner moves past the mast and onward to the other end of the boat. Meanwhile, the mainsheet is detached and used to rotate the rearward end of the boom through a horizontal half circle. The spar join is then re-attached at the new "forward" end of the boat and the mainsheet is re-tightened at the new "rearward" end. [16]

Tepukei

The Maunga Nefe, a te puke or folafolau was built on Taumako and sailed out of Nifiloli; it was used for travel and trading within the Santa Cruz archipelago Sudseeabteilung in Ethnological Museum Berlin 11d.jpg
The Maunga Nefe, a te puke or folafolau was built on Taumako and sailed out of Nifiloli; it was used for travel and trading within the Santa Cruz archipelago

A shunting rig with the sail propped vertically at the bow, very similar to the proa rig described above.

Non-shunting crab claw

The term "crabclaw sail" is also used for non-shunting sails that widen upwards. [18] The 'ōpe'a, the upper spar, is braced up so high that it is nearly parallel to the mast (as in a gunter rig). The paepae, the lower spar/boom, points well above the horizontal, unlike the boom of most gunter rigs and gaff rigs. The two spars can be brought together or pulled apart with control lines. [19] The mast is fixed and stayed. [17]

Performance

The crab-claw sail is something of an enigma. It has been demonstrated to produce very large amounts of lift when reaching, and overall seems superior to any other simple sail plan (this discounts the use of specialised sails such as spinnakers). C. A. Marchaj, a researcher who has experimented extensively with both modern rigs for racing sailboats and traditional sailing rigs from around the world, has done wind tunnel testing of scale models of crab-claw rigs. One popular but disputed theory is that the crab-claw wing works like a delta wing, generating vortex lift. Since the crab claw does not lie symmetrically to the airflow, like an aircraft delta wing, but rather lies with the lower spar nearly parallel to the water, the airflow is not symmetrical. However, the presence of the water, close to the lower spar and parallel to it, makes the airflow behave roughly like the airflow over half of a delta wing, as though a "reflection" in the water provided the other half (apart from a narrow gap near the water, which causes a small difference there).

This can clearly be seen in Marchaj's wind tunnel photos published in Sail Performance: Techniques to Maximise Sail Power (1996). The vortex on the top spar of the sail is much larger, covering most of the sail area, while the lower vortex is very small and stays close to the spar. Marchaj attributes the large lifting power of the sail to lift generated by the vortices, while others attribute the power to a favourable mix of aspect ratio, camber and (lack of) twist at this point of sail. [20] [21]

A more modern academic wind tunnel study (2014) provided similar results, with the Santa Cruz Islands tepukei's crab claw sail configuration dominating measurements. [22]

See also

Related Research Articles

Sailing ship Large wind-powered water vessel

A sailing ship is a sea-going vessel that uses sails mounted on masts to harness the power of wind and propel the vessel. There is a variety of sail plans that propel sailing ships, employing square-rigged or fore-and-aft sails. Some ships carry square sails on each mast—the brig and full-rigged ship, said to be "ship-rigged" when there are three or more masts. Others carry only fore-and-aft sails on each mast—schooners. Still others employ a combination of square and fore-and aft sails, including the barque, barquentine, and brigantine.

Sail plan Diagram of the masts, spars, rigging, and sails of a sailing vessel

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.

Lateen

A lateen or latin-rig is a triangular sail set on a long yard mounted at an angle on the mast, and running in a fore-and-aft direction.

Outrigger boat

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.

Proa Type of multihull sailboat

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.

Fore-and-aft rig Sailing rig consisting mainly of sails

A fore-and-aft rig is a sailing vessel rigged mainly with sails set along the line of the keel, rather than perpendicular to it as on a square rigged vessel.

Tepukei

A tepukei, tepuke or TePuke is a Polynesian boat type, characterized by its elaborate decking, its submerged hulls and symmetrical "crab claw" sail slender foil or radically extended tips claw sail. Tepukei boats are produced primarily by the Polynesian-speaking inhabitants of Taumako, and have been occasionally borrowed by other Polynesian and Melanesian societies.

Canoe sailing refers to the practice of fitting an Austronesian outrigger or Western canoe with sails.

Spritsail

The spritsail is a four-sided, fore-and-aft sail that is supported at its highest points by the mast and a diagonally running spar known as the sprit. The foot of the sail can be stretched by a boom or held loose-footed just by its sheets. A spritsail has four corners: the throat, peak, clew, and tack. The Spritsail can also be used to describe a rig that uses a spritsail.

Hilu

The Hilu outrigger is a personal size, beach launched sports boat in the sailing canoe style. Hilu was AMF's production version of a boat variety more commonly found in designs hand built by outrigger aficionados. Hilu utilizes fiberglass pontoons and carries a single polyester lateen sail mounted to an un-stayed aluminum mast.

Paraw

Paraw are various double outrigger sail boats in the Philippines. It is a general term and thus can refer to a range of ship types, from small fishing canoes to large merchant lashed-lug plank boats with two outriggers (katig) propelled by sails

Sail Fabric or other surface supported by a mast to allow wind propulsion

A sail is a tensile structure—made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may be made from a combination of woven materials—including canvas or polyester cloth, laminated membranes or bonded filaments—usually in a three- or four-sided shape.

Camakau

Camakau are a traditional watercraft of Fiji. Part of the broader Austronesian tradition, they are similar to catamarans, outrigger canoes, or smaller versions of the drua, but are larger than a takia. These vessels were built primarily for the purposes of travelling between islands and for trade. These canoes are single hulled, with an outrigger and a cama, a float, with both ends of the hull being symmetrical. They were very large, capable of travelling open ocean, and have been recorded as being up to 70 ft in length.

Kaep

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.

The following outline is provided as an overview of and topical guide to sailing:

Tanja sail Oblique quadrilateral sail from south east Asia

Tanja sail or tanja rig is a type of sail commonly used by the Malay people and other Austronesians, particularly in Maritime Southeast Asia. It is also known as the tilted square sail, canted rectangular sail, or balance lug sail in English. In historical sources, tanja sail is sometimes incorrectly to referred as lateen sail or simply square sail.

Bangka (boat)

Bangka are various native watercraft of the Philippines. It originally referred to small double-outrigger dugout canoes used in rivers and shallow coastal waters, but since the 18th century, it has expanded to include larger lashed-lug ships, with or without outriggers. Though the term used is the same throughout the Philippines, "bangka" can refer to a very diverse range of boats specific to different regions. Bangka was also spelled as banca, panca, or panga in Spanish. It is also known archaically as sakayan.

Mayang (boat)

Perahu Mayang or simply mayang is a type of fishing boat from Java, Indonesia. This type of boat is used mainly for fishing and trading. Historically, this indigenous vessel is also favored by European skippers and private merchants for trading in East Indies: 50% of them were using mayang and pencalang. It is mostly used in northern coast of Java. The major production site is in Rembang, Central Java.

Sakman

Sakman, better known in western sources as flying proas, are traditional sailing outrigger boats of the Chamorro people of the Northern Marianas. They are characterized by a single outrigger and a crab claw sail. They are the largest native sailing ships (ladjak) of the Chamorro people. Followed by the slightly smaller lelek and the medium-sized duding. They are similar to other traditional sailing ships of Micronesia, like the wa, baurua, and the walap. These ships were once used for trade and transportation between islands.

Orembai

Orembai or Arombai is a type of plank boat from the Maluku Islands of Eastern Indonesia. It is mainly used for fishing and transport. This vessel is used as far as Batavia, where in the 17th century it became popular to go out "orembaaien" on an evening rowing on the river or city canals.

References

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