"Takapu" Maori for Gannet
Illustration by Harmen HielkemaINTRODUCTION
I have lived all my life with a deep longing for a place to call home..
This inquiry goes some way towards the understanding of where in this great ocean I belong. The product of a culture that has many differences from that of New Zealand, I was born the son of Dutch immigrants in Auckland on the twentieth of December 1957. My father immigrated to New Zealand from Holland in a great iron troop ship called The Sibayak in January 1953.
Sibajak in her heyday: Capetown 1930’s.
A WW2 troop ship which became an immigrant ship in the 1950'sMy mother followed in September of the same year in the Waterman. There was something alien about our family that set us apart from our community. I have felt this difference profoundly throughout my life.
Waterman: Dutch immigrant ship, 1950's
My ancestors were part of a seafaring tradition not too dissimilar from that of the pacific people. The Dutch were among the first Europeans to venture into the Pacific.
What this image does not show is the attack by Scouten and his men on this waka which is under fire from a ships boat. This one got away but the early explorers were in the habit of acquiring artifacts for close study by force with no regard for the lives of the "natives."
Great sailors and ship builders, explorers and adventurers, in search of knowledge, fame, and wealth, they built a powerful colonial empire on what came to be known as the VOC the Dutch East India Company. The relationship of the Dutch with the sea was an area of great interest to my father, whose passion for sailing history and love of all sailing craft awoke a similar interest in me.
Flax wood model of proa: by the author.
As a boy I felt compelled to make sailing models of outrigger canoes, whittled out of the dry, woody flowering stems of the flax plant that flourishes in the coastal areas of New Zealand. My friends and I would send them racing across the bay and watch them longingly, wondering where they might eventually end up, as they dwindled from sight; out to sea.
Harmen with a flax model scratch built from found objects off the beach.
Photo by Sasha Stollman.
My first experience with an outrigger canoe came when my parents took me to the Auckland Museum. In the Pacific Canoe Hall I saw my first Micronesian proa. I was captivated by the beauty of its design and was quick to see that the proa was different from western sail boats. For me the process of understanding these differences has become a link between my own experience and the cultural diversity around me, leading me to a new way of seeing the world and my place in it.
Pacific Canoe Hall: Auckland War Memorial Museum. 1962
Above & below, Louis Choris Sketch: Marshallese Walap, 1822.
The first drawing of a proa I ever saw from a book on Captain Cook that my Father gave me for my 10th birthday. I built a sailing model of this canoe out of a ceder weather board which sailed very well and got me hooked for life! See if you can spot the error he made in the plan and front elevations.
A mutual admiration of the proa was shared by at least two other people whose paths were to eventually cross with mine. In 1974, at seventeen years of age, I met Mike Toy. We were both accomplished yachtsmen, having experience in a variety of small racing and recreational sail boats. Our shared interest of high performance sailing came from an obsession with sailing literature and discussions with weekend race competitors. We all made observations based on the experience gained by building and testing models and full scale vessels. Mike is a talented designer with great practical experience who, along with my father, showed me much of what I know about boat construction. The other person is Jefferson Chapple who I met at the National Maritime Museum in 1993. Jefferson has contributed greatly to my world-view by sharing his philosophies and unique insights with me.
Mike's first drawing of Quiet Cook. 1976.
Takapu the proa is a design by Michael Toy, a design he originally called Quiet Cook. My father and Mike helped me to construct the hull of my new boat over a form built up of stringers on sections. We cold-molded in mahogany veneer with epoxy adhesive.
Takapu soon after launching 1978
Photo by Richard Van Alphen.
Takapu, launched in 1978 at Waiake beach in Torbay, was crudely rigged with a Tornado catamaran sail and a disparate collection of gear, bought, bartered, begged & borrowed from my surroundings at the time. [In the true spirit of the pacific builders of such vessels.] I bought my experience dearly, as we all do. After about five years of persistent trial and error I had something that worked. Takapu's reincarnated and most successful form, utilising only the existing main hull, was launched in February 1995.
Takapu at the National Maritime Museum, "Waka Moana" Symposium 1996
Photos by Peter McCurdy.
(In common with many Pacific cultures is the naming of a vessel in the masculine gender, hence my reference to He when referring to any oceanic vessel)
The basis of this article is the result of experience combined with applied research into the subject of the sailing culture of the pacific region, an investigation into the many virtues of an ancient traditional water craft, and an exploration of its place in a contemporary setting. My task is to develop my skills in design and communication to bring my emerging understanding of people, cultures and artefacts in and around New Zealand to you. Join with me in the process of looking at the descriptions by some of the early observers and consider my analysis of their observations. Many of those who come from outside the pacific sailing paradigm find it difficult to accept some of the ideas associated with proas as a sail boat design. My findings concerning design details of the physical features of the proa and how they work should, to some extent, de-mystify the strangeness of the proa. By planting this small seed in fertile ground, let us see what kind of tree will grow.
I invite you to consider what I now understand about sailing outrigger canoes and sailing craft generally in the new light cast by my research. This may require that you step out of your present understanding into an alternative pathway: the Micronesian single outrigger sailing canoe, or proa.
Takapu with Harmen at Shoal Bay Auckland 2005.
Photo by Tim Anderson
WHAT IS A PACIFIC PROA?
My drawing of Takapu at his winter mooring Ngataringa Bay Auckland.
A proa is a double-ended sailing outrigger canoe unique to the western pacific especially Micronesia where it reached the pinnacle of its development prior to western incursion. A proa is a vessel whose ABA line of symmetry is at 90 degrees to its keel line. [in contrast to a western vessel who's ABA symmetry is in line with the keel]. In order to change direction, the proa is turned end for end, this enables the outrigger to always remain on the windward side on all points of sailing and on either tack. A proa is a mono hull with a buoyant counter-weight attached to a long horizontal keel. Many people see the proa as a multi-hull and categorize it with the catamaran and trimaran, however this is not accurate. The modern trimaran and the catamaran are best seen as hybrids derived from early observations of Pacific sailing craft. This has, at times, resulted in an uncomfortable marriage between contemporary technology and an ancient, highly evolved pattern.
The generic Pacific word for a canoe is waka; [It's outrigger an ama] Variations are waga, wa, va'a, vaka however the term proa [sometimes flying proa ] may be derived from a different origin.
Prau is a Malay word meaning small boat. An other commonly used name is prau, prahu, proe. The word pirogue, (Spanish derivative Peragua, periagua for small boat or log canoe, from the Caribbean), is used by the French, Spanish and Portuguese. Owing to early influence in Indonesia and Malaysia from these countries, I am tempted to speculate that the Malay word prau could have come from this source. The Portuguese sailors may have named the proa from the same word which in their tongue means simply, "bow". The proa has two bows so they may have named the vessel "proa" because of this unique feature. Another translation from Portuguese may be "proa voador" which means flying bow
As a shunting vessel the outrigger is carried on the windward side on both tacks. When early Portuguese first saw how these vessels manoeuvred they might have concluded that technically the ama or windward counterbalance was actually the bow. This definition would presuppose that the leading ends could be thought of as the port and starboard sides and the lee side of the canoe the transom!
Design Brief
“Create a vessel to carry people quickly and safely over water utilizing the energy of the wind with maximum efficiency and the minimum of materials.” This reads like a design brief whose criteria is very adequately answered in the form of the Micronesian proa. They are among the simplest and most refined of sail craft.
Walap of Rongelab, Marshall Islands. Photo: Courtesy American Museum of Natural History.
“The smaller sailing canoe, 20-30 feet as a rule, but sometimes larger, used for deep-sea fishing primarily, but also for short inter island voyaging, usually equipped with a balancing platform, the vaa ta'ie. Beautiful vessels these were, works of sea going art, for they were all utility, marvelously efficient with the minimum of material.
The larger sailing outrigger canoe, 30-50 feet, most of them Micronesian, useful for long-range, deep-sea sailing between island groups. And these as refined sailing machines were the best of all ... they were the most efficient sailing machines ever designed. It will not be long before we recognize that our Americas cup contenders are clumsy in comparison”. (Dodd E., Polynesian Seafaring, Dodd, Mead & Co, USA, 1972)
The proa is the design result of a very different worldview from that which I was nurtured with. The pacific sailing paradigm comes from a sense of being at one with the world and everything in it; land, wind, water, animals, plants, etc. The European comes from a belief that they are individual, isolated and separate from their environment from which, it seems ever greater efforts are being made.
THE PROA.: A New Zealand context.
Left: The Proa "Te Hau" by Jefferson Chapple.
Middle: Waalap "Waan Aelon Kein" Marshall Islands.
Right: Waka Tete "Hou" By Neill Beken. at "Waka Moana," Auckland. 1976.
Photo by Peter McCurdy.
The proa is not a stranger to New Zealand waters. According to Elsdon Best, relics of this type of vessel, which he calls wakatiatia, have come to light in this country suggesting early use of the proa with definite Micronesian origins.
(Best E. Polynesian voyagers, Dominion Museum monograph #5, second edition.1975)
Kiribati canoe model N.Z. National Maritime Museum.
At present there are a number of beautiful Waka ama held in museums throughout New Zealand representing nearly every Pacific sailing culture. The New Zealand National Maritime Museum has a four-meter and a twenty-five-meter Kiribati proa on display in its canoe hall. The Auckland Institute Museum has a five-meter Kiribati proa in storage along with a large collection of models. The Canterbury Museum has an eight meter Kiribati proa. All the proas I have mentioned are micronesian. However, apart from a handful of people, like myself, who own a proa, there is little contemporary use of this highly successful design in this or any other country.
The outrigger canoe association of New Zealand is currently following the world trend toward the sport of Hawaiian and Tahitian paddling waka ama racing. (Waka ama is the name given to the outrigger canoe by the Polynesian people waka = canoe, ama = outrigger)
The sport of wakatere (canoe racing) here in New Zealand is gathering momentum with enthusiastic support from people of all ethnic origins and gender. Dear to the hearts of these people is the desire to create an international Waka ama sailing program, a development project in which I am currently involved. Simply rigging a mast and sail to their existing paddling canoes is only a temporary solution to the design problem of a serious outrigger canoe sailing program.
When the Dutch explorer Abel Tasman encountered the Maori, he discovered a culture that had already established at least a thousand years of history in this country. Most of what is understood about the origins of the Maori is based on myth, legend from a strong verbal tradition, sketchy archaeological evidence and speculation. Maori artifacts vary in detail but their basic cosmology is universal down the length of New Zealand. Like all the pacific people they share an oral tradition of legends and histories. With a sophisticated sense of aesthetics expressed in carving, painting and weaving, they embody the spiritual in everything they make to the extent that they regard their creations as individuals who are named, respected and spoken to. The scale of their expression in terms of the sheer size of their artefacts as well as investment in terms of resources and manpower demonstrates the Maori's commitment to their cosmology. They worked with a highly advanced understanding of the characteristics of timber. Trees were utilized for the construction of buildings, canoes, weapons tools and ornaments.
The life force of the tree was deeply respected and blended with the spirits of their ancestors. Unfortunately much of what remains of this rich legacy is contained in museum collections; ancestors in jail. Expression of the unseen spiritual realm and the dependence on intuition to solve complex problems is where my interest lies. Elaborate carving of structural and decorative elements in their constructions is a feature of many Pacific cultures (making the supernatural world visible) and is also true of the Vikings of northern Europe (comparisons between these cultures have often been made in the past; Sir Peter Buck called his famous book on Polynesian culture Vikings of the Sunrise (Whitcombe and Tombs, New Zealand,1958) This ornamentation features swirling patterns resembling turbulence and vortices which demonstrates a sophisticated awareness of the powerful yet subtle energies at work in the world around them. There is a connection between these art forms and recent scientific photographs of turbulence in the study of fluid dynamics. This will form the basis for further discussion with regard to proa dynamics
THE PROA : a history.
The history of sail is an area of research where it is difficult to find a basis on which to model theories. The earliest graphic evidence being of Egyptian origin; five thousand-year old depictions of relatively sophisticated sailing vessels rendered on tablets excavated by archaeologists during the 19th and 20th centuries.
"Every culture with very few exceptions, somewhere in its past has some connection with the sea and a technology for moving or sailing on it. The sailboat was the first machine to give men freedom of motion without muscle power. Few of us any longer recognize that the sailboat was truly the first instrument which freed us from bondage to the land ... the first sailboat that could move up wind. This invention made the whole world accessible to man, ... Neither do we recall, unless our attention is drawn to it that the sailboat was the first machine to achieve powered motion without rotating parts." Smith B., The 40 Knot Sailboat, Grosset & Dunlap, New York, 1963.
The pioneering nature of the ancient people of the Pacific is made evident by the emerging understanding of their migratory paths across the island-studded Pacific. They had a highly successful, dynamic, neolithic technology. They ranged freely in canoes that were simple, safe, fast and seaworthy. Technology was, as always affected by the constraints of available materials. Concern about creating accurate reproductions of these ancient craft down to the original materials used in their construction may be a bit pedantic. When James Dina set out to build an American Indian birch bark canoe he worried about being unable to find one species of timber he knew had been used in a particular application in the canoe's construction:
"You don't have to worry about keeping it pure, the Indian was a true child of the forest, so he had many ways of doing things. If one material wasn't there he found another; Man is a survivor: he always did what made the most sense at the time."
[ Harold Tantaquidgeon, Mohegan Indian chief, from Voyage of the Ant, Dina. J, Stackpole, USA,1989 ].
Their vessels were designed for their needs out of the materials at their disposal. Trees, coconuts, driftwood. Tools were of shell, fire, and stone (where available). Evolution, ingenuity and ritual guided their hands as they created craft of elegant, functional simplicity. Lives were invested in these canoes, time and resources. A person's mana or status determined by the quality size and speed of the vessel. This assured their future in the equilibrium of their relationship with Tangaroa the sea god, the evolution of a flexible pattern. The quality of the canoe, all that protected its occupants from the awesome power of the ocean, was in many instances, sculpted from the trunks of living trees, pacified and sacrificed with deep respect for their life force.
"Conserving any resource, no matter how abundant." (Dina J. et al)
Small wonder that pacific canoes were (and still are) regarded as living beings in their own right, endowed with the status of an important community member. Canoes were consulted by their owner, communication taking place in meditation and ritual at a deeply personal level. Imagine, if you will, a view of the world in which matters of great significance are discussed with the spirit of a canoe!
The following quotation by respected European anthropologist, Malinowski, confirms my view.
Canoes setting out from Mailu, Papua New Guinea. Photo: Rev. W.J.V. Saville, London Missionary Society, 1827."
A canoe is an item of material culture and as such it can be described, photographed and even bodily transported into a museum. But and this is a truth too often overlooked the ethnographic reality of a canoe would not be brought much nearer to a student at home, even by placing a perfect specimen right before him.
Lakatoi under sail, port Moresby, Papua New Guinea, Photo: J.W. Lindt, 1885. La Trobe Collection, State Library of Victoria, Melbourne.
The canoe is made for a certain use and with a definite purpose: it is a means to an end and we, who study native life, must not reverse this relation and make a fetish of the object itself. In the study of the economic purposes for which a canoe is made, of the various uses to which it is submitted, we find the first approach to a deeper ethnographic treatment. Further sociological data, referring to its ownership, accounts of who sails in it, and how it is done: information regarding the ceremonies and customs of its construction, a sort of typical life history of a native craft all that brings us nearer still to the understanding of what his canoe truly means to the native. Even this however does not touch the most vital reality of a native canoe. For a craft, whether of bark or wood, iron or steel, lives in the life of its sailors, and it is more to a sailor than a mere bit of shaped matter. To the native, not less than to the white seaman, a craft is surrounded by an atmosphere of romance, built up of tradition and of personal experience. It is an object of cult and admiration, a living thing, possessing its own individuality.
We Europeans, (oops! apologies on behalf of Mr Malinowski for excluding people of other ethnic origins from reading his material.) whether we know native craft by experience or by descriptions, accustomed to our own extraordinarily developed means of water transport, are apt to look down on a native canoe and see it in a false perspective regarding it almost as a child's plaything, an abortive attempt to tackle the problem of sailing, which we ourselves have satisfactorily solved. But to the native his cumbersome, sprawling canoe is a marvelous almost miraculous achievement and a thing of beauty. He has spun a tradition around it and he adorns it with his best carvings, he colours and decorates it. It is to him a powerful contrivance for the mastery of nature, which allows him to cross perilous seas to distant places. It is associated with journeys by sail, full of threatening dangers, of living hopes and desires to which he gives expression in songs and story." ( Bronislaw Malinowski, Argonauts of the Western Pacific, E.P. Dutton, USA, 1961 )
Trading canoe with traditional matting sails, Siassi Islands, Papua New Guinea.
Photo: Philip J. C. Dark.
In this millennium, and certainly from the late fifteenth century it was the Portuguese who, in their clumsy ships, made bold voyages of discovery contributing to the colonisation of the Pacific by Europeans.
In my view proas have been misrepresented because of their basic lack of understanding of the pacific sailing paradigm applied to proas by European observers. Over the centuries, since the first reports of these canoes to emerge from explorers such as Magellen, Drake, Tasman, Schouten, Dampier, Cook, and Anson to name but a few, an erroneous opinion has been formed by outsiders based on the observations of these great navigators.
Dampier describes, with great accuracy, the features of the outrigger canoe of the Mariana group of islands in Micronesia but fails to notice an error when he reported that the outrigger float was carried to leeward. William Dampier wrote in his journal, The New Voyage on May 21 1686:
"The natives are ingenious beyond any people, in making boats, or proes, as they are called in the East Indies, and therein they take great delight, these are but built sharp at both ends; the bottom is of one piece, made like the bottom of a little canoa, very neatly dug, and left of good substance. This bottom part is instead of a keel. It is about 26 or 28 foot long; the underpart of this keel is made round, but inclining to a wedge, and smooth; and the upper part is almost flat, having a gentle hollow and is a foot broad; from hence both sides of the boat are carried up to about 5 foot high with narrow plank, not above 4 or 5 inches broad, and each end of the boat turns up round very prettily. But what is very singular, one side of the boat is made perpendicular like a wall, while the other side is rounding, made as other vessels are with a pretty full belly. Along the belly side of the boat, parallel with it, at about 6 or 7 foot distance, lies another small boat, or canoa, being a log of very light wood, almost as long as the great boat, but not so wide, being not above a foot and a half wide at the upper part, and very sharp like a wedge at each end. And there are two bamboos of about 8 or 10 foot long, and as big as oneÕs leg, placed over the great boat's side, one near each end of it, and reaching about 6 or 7 foot from the side of the boat: by the help of which, the little boat is made firm and contiguous to the other. These are generally called by the Dutch and by the English from them outlayers. Because the wind here being in a manner constantly east, (or if it were west it would be the same thing) and the range of these islands, where their business lies to and from, being mostly north and south, they turn the flat side of the boat against the wind, upon which they sail. And the belly side consequently with its little boat is on the lee; (this is one example of misrepresentation of the facts by this observer, in fact these boats have always sailed with the outrigger to windward) ... and the vessel having a head at each end, so as to sail with either end foremost, (indifferently) they need not tack, or go about, as all our vessels do, but each end of the boat serves either for head or stern as they please. When they ply to windward and are minded to go about, he that steers bears away a little from the wind by which means the stern comes to the wind which has now become the head, only by shifting the end of the yard. This boat is steered with a broad paddle instead of a rudder. I have been more particular in describing these boats because I do believe they sail the best of any boat in the world. I did hear for my own satisfaction the swiftness of one of them; sailing by our log we had twelve knots on our reel, and she run it out before the half minute glass was half out which if it had been no more, is after the rate of 12 miles an hour: but I do believe she would have run 24 mile in an hour. It was very pleasant to see the little boat running along so swift by the others side."
Kiribati Proa: Photo by Peter Carmichael.
Anson assumed that the outstanding windward performance of these vessels was a result of their extreme fineness and flat leeward side, not far off the mark but not the whole story.
Quote from Anson's Voyage Around the World, J.M. Dent, London, 1911.
October 1742 ... These Indians are no ways defective in understanding, for their flying proas in particular, which during ages past have been the only vessels employed by them, are so singular and extraordinary an invention that it would do honour to any nation, however dextrous and acute. since, if we consider the aptitude of this proa to the navigation of these islands, which lying all of them nearly under the same meridian, and with the limits of the trade wind, require the vessels made use of in passing from one to the other to be particularly fitted for sailing with the wind upon the beam; or if we examine the uncommon simplicity and ingenuity of its fabric and contrivance, or the extraordinary velocity with which it moves, we shall in each of these articles, find it worthy of our admiration, and deserving a place amongst the mechanical productions of the most civilised nations where arts and sciences have most eminently flourished. As former navigators, though they have mentioned these vessels, have yet treated them imperfectly, and, as I conceive that besides their curiosity they may furnish both the shipwright and the seaman with no contemptible observations, I shall here insert a very exact description of the build, rigging, and working of these vessels, which I am the better enabled to perform, as one of them fell into our hands on our first arrival at Tinian, and Mr. Brett took it to pieces that he might delineate its fabric and dimensions with greater accuracy; so that the following account may be relied on. The name of flying proa, appropriated to these vessels,. is owing to the swiftness with which they sail ... I cannot help believing that with a brisk trade wind they will run near twenty miles an hour ... a prodigious degree of swiftness. But let us give a distinct idea of its figure. The construction of this proa is a direct contradiction the practice of all the rest of mankind; for as is customary to make the head of the vessel different from the stern, but the two sides alike, the proa, on the contrary, has her head and stern exactly alike, but her two sides very different; the side intended to be always the lee side being flat, whilst the windward side is built rounding, in the manner of other vessels: and to prevent her from oversetting, which from her small breadth and the straight run of her leeward side, would, without this precaution, infallibly happen, there is a frame laid out from her to windward, the end of which is fastened to a log fashioned into the shape of a small boat, and made hollow. The weight of the frame is intended to balance the proa, and the small boat is by its buoyancy to prevent her oversetting to windward; and this frame is usually called an outrigger ... the proa, by sailing most excellently on a wind, and with either end foremost, can run from one of these islands to the other and back again only by shifting the sail, without ever putting about; and by the flatness of her lee side and small breadth, they are capable of lying much closer to the wind than any other vessel hitherto known, and thereby have an advantage which no vessels that go large can ever pretend to. The advantage that I mean is that of running with a velocity nearly as great, and perhaps sometimes greater than what the wind blows with..."
Anson's drawing credited to his ship's carpenter. If you followed this drawing, as so many museum curators do, it would never sail.
Not until late last century did we begin to understand what we were looking at!
Both witnesses reported very high speeds, higher in many cases than the recordings of proa performance characteristics today, in the range of twenty nautical miles per hour.
What Anson couldn't see, was that the close winded performance of the proa was partly the result of invisible aero-hydrodynamic forces.
PROA-DYNAMICS: In the wind
The Oceanic lateen, sometimes referred to as the crab claw sail, (because of the obvious similarities some variations of this sail type bear to a crabs claw) may be derived from the square sail. Perhaps ultimately this sail-form could have Phoenician and even Egyptian origins since it is known that these civilizations had ancient contact with the Chinese. The Chinese had contact with the Pacific down through the Indonesian archipelago since ancient times. (I have deliberately avoided providing references for these ideas as I have yet to see information that was verifiable and not just speculative.) Of course these sail forms could have evolved independently from each other.
The Oceanic lateen sail is triangular in profile. The angle at the tack where the two longest sides converge is always between fifty to sixty degrees. Jefferson Chapple, a proa specialist and owner from Auckland, has measured these convergent angles from evidence collected from models and photographs comparing them to modern delta wing jet aircraft and found that they correspond. Further reading of advanced aerodynamic principles has provided me with the understanding that the delta wing is a simple solution to the problem of providing stable powerful lift. According to Marchaj lift may be the result of two large lift-producing vortices on the sail's leeward surface. Practical experience has shown me that vortex lift may occur when the sail is over sheeted when reaching (this practice produces no discernible stall characteristics) and laminar flow lift occurs when hard on the wind.
A discussion about airflow over a sail must begin with a brief overview of aerodynamic theory and how airflow over a surface generates lift, in the case of a sail-boat, thrust (still referred to as lift) and drag. These are the primary forces that influence the shape of a sail.
"Nature's wings, designed to suit the needs of the individual bird, dictate the type of flying the bird may perform. ( Gyford Stever, Flight, Time-Life Books, The Netherlands, 1970. ) Long narrow wings for soaring; like those of the albatross, or short broad wings like those of the humming bird, for high energy bursts of speed and maneuverability."
The same is true for both sail and aircraft.
Lift is actually produced by the difference in air pressures above and below a surface. In 1738, Swiss mathematician Daniel Bernoulli formulated the principle of pressure variation on a surface based on the velocity of the fluid (in this case air). In the case of a bird (or aircraft)'s wing its upper surface is convex. When presented with airflow across its surface from front to back, the surface splits the flow of air which then reconnects behind. During the transition, air over the upper curved surface must move faster to make that connection. This has the effect of reducing the ambient air pressure on the upper surface, the wing moves toward the resulting area of reduced pressure under the influence of relatively higher ambient pressure below.
Low pressure zone
Plan view of air flow over sail:
perpendicular lines indicating lift.
High pressure zone.
Modern yacht sails are engineered to maximize the potential energy of this phenomenon.
Operating on the same physical principle is lift created by vortex flow. (Kuchemann, D., The Aerodynamic Design of Aircraft, Pergamon, 1978) The awesome lifting power of this force in nature is demonstrated by the tornado, a meteorological phenomenon capable of lifting heavy objects off the ground. The vertical cone of this vortex is spinning at extremely high speed causing a reduction in air pressure creating lift. Any movable object whose surface area is affected by this force will defy gravity and rise if the upper surface pressure is reduced enough to neutralize the weight of the object.
My drawing of vortical turbulence over a triangular planform.
Vortical lift also exerts a lifting force when the vortex is parallel to a surface. Vortical lift is the phenomenon the Concorde relies on to fly at subsonic speed. In fact the paper dart and the classic diamond and delta kites all owe their flight capability to vortical lift.
End view of Concorde showing vortices.
Plan view of Concorde showing vortices.
The triangular, double-boom, lateen sail of Micronesia is another example of this vortex-producing sail shape.
My drawing of vortex development over an oceanic lateen sail.
My drawing: cross section of above illustration.
Recent wind tunnel tests conducted by C.A. Marchaj on a variety of contemporary sail shapes showed that under some conditions the oceanic lateen sail created, at its best, thirty percent more lift than the only other high performing sail in the experiment: the Marconi or Bermuda sloop sail. These performance data were recorded at a wind speed of twelve knots on model rigs at various angles to the wind. The oceanic lateen showed its superiority at between ninety and one hundred and fifty degrees off the true wind. ( Ref. Marchaj C.A. Aerodynamics of sails. Adlard Coles 1996 ).
I interviewed Tom Schnackenberg, Team New Zealand's aero-hydrodynamics specialist. He was involved in the development of the winning Black Magic boat design that won the America's Cup. on the subject of aero-hydrodynamics, questioning him on the issue of vortex lift as it related to oceanic lateen sails. He tended to be dismissive of this theory and was not impressed with Marchaj's tests and conclusions, saying that turbulence and vortices were, in his experience, drag forces only.
My drawing of undesirable tip vortices.
These same undesirable forces are none the less described as forces and as such represent a potential energy source. It is my belief that, based on further reading and recent experiential research on the subject, the native people of the Pacific managed to develop a sail and rig combination successfully harnessing these phenomena. Tom Schnackenberg agreed that the oceanic lateen provided a very satisfactory solution to the problem of a simple aero-foil design that would supply lift with the minimum of sail trim fittings with good performance characteristics at all angles to the wind.
The work of Dr David Lewis is of great international significance. He dedicated his life to investigating the ancient seafaring traditions of the pacific people. Lewis is the author of such books as "We, the Navigators", a definitive work on the non-instrument navigational techniques of the ancient Pacific seafarers; "The Voyaging Stars, secrets of the Pacific navigators"; and many other books and articles. David Lewis was near his home in Auckland working on a new vessel in which he intended to make a voyage to China.
He listened carefully to my explanation for my visit. I knew from reading his material that he had experienced first hand, several extensive voyages on a variety of Pacific island sailing craft.
I questioned David Lewis closely about several aspects of performance and features of Micronesian outrigger canoes. Dr Lewis told me the story of an inter island trip he took in a Kiribati proa, the crew of which were in a constant state of fear. He reported that the vessel continually rounded up into the wind and seemed to be in danger of being caught aback. (A bad situation in a proa because the rig has no support when filled with wind from the lee side of the sail. This can lead to capsize to windward or damage to vessel and occupants from falling spars.)
"The men on board sailed very conservatively and would haul hard in on the sheet to make her bear away." David's comment intrigued me and resulted in my investigating the reason why they would have this problem. It is my belief that if this vessel were set up correctly it would have behaved in a much more predictable manner. Most of the contemporary pacific lateens utilize cotton or synthetic sails. I believe that inappropriate use of cotton sails severely limits the performance potential of the lateen sails in use today. With the advent of introduced technology the characteristics of these highly refined sailing craft was compromised. With no technical basis on which to critically analyze the consequences, and with the influence of an incompatible western paradigm, today's Oceanic lateen sail is only a remnant (pardon the pun) of its former self.
On closer inspection of models and actual canoes I was able to determine that there is a fundamental difference between the characteristics of cotton and pandanus as a sail fabric. That difference is in how the cloth is manufactured and in its subsequent orientation in situ. In order to demonstrate this it is helpful to look at the manner in which a pandanus sail is made. The weavers prepare uniform widths of fibre and begin by diagonally plaiting one piece over the other at 90 degrees to each other creating as they do so a pattern of squares at forty five degrees to the straight side of the panel.
Warp, weft & shear diagram: from Jeremy Howard-Williams' "Sails"
In the case of cotton, the warp and weft (the names for the longitudinal and lateral threads), by virtue of the looms on which they are created, run parallel and at right angles to the straight edge of the panel. When bolts of cotton fabric are used as a substitute to hand woven pandanus the economical considerations call for the material to be sewn up parallel to the leech (trailing edge of the sail). Because of the longitudinal lines of thread the cloth remains taut at the leech of the sail where the fabric has been hemmed, this tripling of the material at this point renders this zone resistant to stretch. The leech, as the trailing edge, is the critical area of the sail where the most drag occurs. If this region is tight it will cause the airflow to deflect and create a stall condition which is detrimental to sail performance. A sideways force results in the vessel rounding up into the wind and coming to a stop. The body of the sail stretches and creates a belly with the force of the wind acting on it. At every join in the cloth these zones of tension prevail with alternate areas of fullness. This lumpy aerofoil is not conducive to supporting lift. This, in itself, is enough to throw out the subtle balance of forces that allow a sailboat to perform to its potential. Conversely, lift-inducing vortices form readily on the uniformly straight conical section inherent in the case of a hand-woven sail.
The diagonal weave of the pandanus sail allows for stretch to occur even at edges where the fabric is hemmed or joined. This stretch evens out the sail and its shape actually improves under tension. Unlike western sails, oceanic lateens are not cut with any shape (or draft). The optimum shape is like that of a slice cut off a cone from the apex to the base. Jefferson Chapple of Auckland, the designer and owner of Te Hau, a six-meter micronesian proa, has proven that, with draught sewn in to his lateen sail in the traditional European fashion, his proa proved; ..."completely unmanageable, I have subsequently recut the sail twice to further eliminate draft." He told me.
Example of a cotton sail with extreme leach "hook."
Photo: James Sears.
Tim Bartlett is a renowned, internationally successful, 12-foot skiff sailor. I asked his opinion on the matter of leech hook (the tendency for a sail to develop a tightly curved trailing edge detrimental to performance and control). His words were; "Sails are the engine of a yacht, too much leech hook is the best way I know to park a sailboat".
Further investigations on the question of vortical lift relating specifically to the Micronesian canoe have been conducted at the Auckland University in a wind tunnel at the School of Mechanical Engineering by I.E. Atimalala. and Keith Bailey. Their 1992 paper describes the performance predictions based on the model of a seven-meter mariana proa from western Micronesia. This document supports the claims made by Dampier and Anson that the speed potential of the proa was indeed at least as great as that of the wind.
With the benefit of hindsight (it has been 5 years since I first researched and wrote sections of this article) I can confirm from my own recently applied research on my new proa Toroa that this discussion has made several valid assumptions. That the crab-claw sail is powerful and effective as a plan-form there can no longer be any doubt. That the sail can be assembled without camber but for a small amount of luff curvature to accommodate spar bend, this has the resulting effect of contributing a certain amount of camber in the sail, which has been proven beneficial for close-hauled situations. When close-hauled the sail seems to operate under laminar flow ( Bernouli lift ) conditions. As the proa's head comes off the wind the sheeting angle remains relatively unchanged and yet does not stall as one might expect of a marconi mainsail. As the proa accelerates the apparent wind moves forward. It is at this time when I believe that the vortices form and contribute to the sudden change in performance and resulting increase in power and speed.
PROA_DYNAMICS: In the water.
Tara, a 1/5 scale model of Takapu showing hull asymmetry. (Fish eye view)
My Drawing of a vortex street in fluid.
Longitudinal hull asymmetry is a feature of the proas of the western pacific. Both Dampier and Anson accurately represent this characteristic. Sir Arthur Grimble was a missionary on the Gilbert and Ellice Islands (now called Kiribati) in the 1920s. His journal writings compiled by his daughter Rosemary Grimble in her 1972 publication "Myths Migration and Magic from the Gilbert Islands", are regarded by scholars as a definitive text on the features and performance of proas from that region. I have a problem however with his assumption that longitudinal hull asymmetry (the characteristic lop-sidedness of the micronesian proa) was intended to counteract the drag induced by the outrigger float.
(If this were true then they would surely have built hull asymmetry into their paddling canoes, which would have been as problematic to control as a sailing canoe, following this assumption). Another consideration is that the outrigger float was designed to fly above the surface much of the time. My experience with both Takapu and Toroa bear this out.
My drawing of Hull asymmetry. The example is of Takapu.
Hull asymmetry takes various forms throughout the Pacific. In Micronesia, where it was most highly developed, the backbone of the canoe is bent in two directions during construction. In other instances keels are straight but sides are built with parabolic cross sections, one side made rounder than the other and featuring a shallow concave indentation in the lee side of the hull below the waterline. Michael Toy designed the hulls Takapu and Toroa with this feature. He understood that asymmetric hull curvature works as a hydrofoil designed to counteract leeway. My personal experience is that, as the vessel gathers speed, it begins to make ground to windward to the extent that I always have to head below my objective so as not to over shoot the mark.
I described my observations to Tom Schnackenberg, Tom agreed that because of pressure reduction over a curved surface (Bernoulli's principle) the hull shape would definitely have a tendency to lift to windward. In regard of this matter many authorities still hold to Grimble's original interpretation. Tom Schnackenberg's conclusion was that the proa was a simple yet sophisticated design, making the most efficient use of the energy and materials available to oceanic people. I am sure that the performance and design characteristics of the outrigger canoes of today suffer from the influence of an incompatible sailing paradigm.
This is the one beneficial aspect of hull design that often overlooked in the many the new proas that are being built and sailed in all parts of the world at this time.
The crab claw sail or oceanic lateen, as previously discussed, generating lift in two quite different ways is mounted on the lee hull. Its effort is distributed along a significant portion of the hull from the bow where the tack is fixed, to the boom end roughly corresponding in length to the hull. Combined with the long narrow hydrodynamic hull, which dynamically resists leeway with increasing efficiency as the wind increases. This is combination contributes to longitudinal stability, allowing the vessel to be steered without rudders, by crew weight and sail trim alone.
The problem of changing direction on a conventional sailboat is solved by means of a rudder. This dynamic hydrofoil is situated at the rear of the boat and is directly linked to a steering device such as a tiller (lever) or a wheel via a series of pulleys. These mechanisms are complex and vulnerable.
Rudderless Steering
To understand rudderless steering it may help to look more closely at the dynamics involved. The process is a very simple matter. Maneuvering a proa has its parallel in the modern sail board or wind surfer. On any sailing vessel, the area of aerodynamic lift occurs in an area of low pressure on the leeward side of the sail. This force is exerted sideways and slightly forward. The sideways force on the hull of a proa is resisted by virtue of its deep profile and asymmetric waterline shape. Because there is some forward component in the driving force of the sail the vessel tends to follow the path of least resistance and move forward. If the force exerted by the sail is balanced in the center of the area of lateral resistance of the hull the boat will sail straight (given steady wind and flat water).
The area of lateral resistance versus the area of effort (side force or lift) is part of the equation that determines the longitudinal balance of the boat. When this dynamic changes, e.g. with a shift in crew position a resulting change in waterline occurs the boat quickly changes direction. The proa with its narrow water line and fine ends is extremely sensitive to pitch; that is, rocking forward and back in a vertical plane. If the vessel is trimmed with crew weight forward the bow will depress deeper into the water, this will lift the stern into the air. Consequently the back of the vessel begins to get pushed sideways away from the wind and the bow tends to move closer to the wind direction. Because the underwater hull profile is elliptical (keel rocker) the wetted area changes dramatically in relation to the sail. The area of lateral resistance moves forward relative to the area of lift. Because the area of lift is now effectively behind the under water balance area, the boat begins to deviate. The reverse of this with crew weight moving aft has the opposite effect. The back of the vessel is depressed into the water and the center of lateral resistance of the hull moves back in relation to the area of force exerted by the sail. This causes the boat to deviate away from the wind. The degree and speed of course change is governed by the weight distribution along the length of the hull. The faster and further the weight is moved the quicker and more extreme the change in direction.
The advantage of this system is the reduction of mechanical parts and the associated complexities and potential for failure. (Of course a paddle is always carried to facilitate immediate course changes and as an auxiliary power source.)
The proa has its keel and ballast above the waterline reducing drag, its counterweight exerting maximum righting moment even at rest. This makes for a very stable vessel. As the wind increases the crew move out on to the outrigger platform which effectively increases the leverage against the increased heeling moment of the sail. The mass of the outrigger is a minute fraction of that of a ballast keel, therefore requiring less energy to move. The result is that the proa is capable of both rapid acceleration and high top speed. The buoyant prancing motion of the proa through the water is a familiar characteristic. The resulting ride is comfortable and exhilarating; if a little wet.
Relatively small forces on the rig allow for less rigid, more flexible and subsequently low cost and simple construction. When sailing and shunting the rig stays to leeward leaving a large deck area free to move around on.
Flexibility is another virtue of the proa pattern. Forces of torsion and shear occur as the hull and float encounter different wave patterns. These forces are absorbed by the spring-like qualities of flexible beams secured with lashings. This technology is accessible and easily maintained.
My drawing of vortex streets illustrating underwater wake turbulence behind a proa.
TOROA: Where to from here ?
Toroa: Lake Pupuke. Photo by Mike Toy.
Our latest project Toroa is built in cold molded meranti plywood. Toroa is made entirely of recycled demolition timber, abundant where we live. There are almost no metal fastenings, everything is glued or lashed. The running rigging consists of rope and deadeyes only, no rotating parts. The sail is Novathene , (P.E. or polytarp). Spars are of radiata pine.
Toroa is a seaworthy, efficient, sheltered water vessel. Its application is only limited to the skill level of the crew. Its appeal lies in its safety and ease of handling. Suitable as a recreational or racing sailboat, the proa can be scaled in size anywhere from 5 meters to 20 meters without compromising its basic qualities.
Steering dagger boards.Toroa has been modified to carry two dagger boards fitted through centre cases near the ends of the hull. The dagger boards feature asymmetric cross sections (ogive section) with the rounded surface presented to
windward.
Ogive section foil (section of a circle with flat lee side)
The boards are controlled vertically and independently to provide steerage. When a board emerges through the keel it has a profound effect on the direction of the boat. Three things happen, leeway force is counteracted, hydrodynamic lift from the board's asymmetry occurs and the centre of lateral resistance is moved aft. Variations in depression of leading and trailing boards combine to cause dynamic course alteration. This modification was made to allow me to sail Toroa single handed so that I can focus on the important task of keeping the boat upright, a job which would otherwise be performed by a crew.
THE TOROA EXPERIENCENew Zealand: a sparkling Waitemata harbor day and a 15-knot offshore breeze. Sailing with the wind on the beam, (at ninety degrees to the keel-line) my proa Toroa tracks along with his bow slightly down, under the press of his crab claw sail. A rainbow shimmers in the fine misty spray sent up by the prow, cutting a neat swathe through the textured surface of the flat sea. The water parts and closes around his slender hull and passes with the slightest disturbance, leaving only bubbles trailing off to leeward, to mark his path. Toroa is travelling at wind speed. The outrigger float flies half a meter above the surface casting a darting reflection over the flashing facets of the water. Control at this speed is second nature for me now. The unity of sail, boat, and man, fused into one entity. In the context of this experience one cannot be without the other. The extended periods away from sailing Toroa are filled with sustaining memories of times like these, of thinking about the form, the simplicity of concept and design.
Toroa at speed: Lake Pupuke, Auckland, NZ. Photo by Nigel Holton.
Toroa & Harmen, Waitemata Harbour: (Maori for Sparkling waters)
Photo by Russel Brown '03
To conclude the sailing waka ama or proa is a pattern much maligned and misunderstood. Further research and development I believe will result in new approaches to sailing and yacht design in this century as people turn to alternative paradigms.
Proa racing would be intriguing and exciting. Imagine a round robin series featuring 20 meter proas flying around a course with two markers set one up wind of the other where their strongest points of sail would be showcased. Tacking upwind and down wind. Running flat off is not practical (this being the case with most multi hulls) the fastest course down wind between two points is not always a straight line.
"The only real voyage of discovery consists not in seeking new landscapes but in having new eyes." Marcel Proust.
Takapu logo. Derived from plan view of Takapu's waterline intersected by the sail profile. Design by Harmen Hielkema, 1996.
Harmen Hielkema