Windsurfing World

As you have already quessed, today I will focus on sails. A current windsurfing sail is constructed of monofilm (a clear PVC film), dacron ( a type of woven polyester) and mylar, so it is made with a long life and performance in mind. Sensitive parts are reinforced and proven with kevlar mesh. Two designs of a sail are predominant: camber induced and rotational. Cambered sails have 1-5 camber inducers, plastic devices at the ends of battens which cup against the mast. They help to hold a rigid aerofoil shape in the sail, better for speed and stability, but at the cost of maneuverability and generally how light and easy to use the sail feels. The trend is that racier sails have camber inducers while wave sails and most recreational sails do not. The rigidity of the sail is also determined by a number of battens. Beginners' sails often do not have battens, so they are lighter and easier to use in light winds. However, as the sailor improves, a battened sail will provide greater stability in stronger winds.

If discussing this topic, rotational sails have battens which protrude beyond the back aspect of the mast. They have to flip to the other side of the mast when tacking or jibing, hence the rotation in the name. Rotational sails have aerofoil shape on the leeward side only when filled with wind. They can be absolutely flat and depowered when sheeted out. In comparison with cambered sails, rotational designs offer less power and stability when sailing straight, but are easier to handle when maneuvering. Also, rotational sails are much easier to rig.

For extra information, the leading edge of a sail is called the luff. The mast is in the luff tube. The rear edge is called the leech. The front bottom corner of the sail, where the mast foot protrudes, is called the tack, and the rear corner, to which the boom is attached, is called the clew. The bottom edge, between the clew and the tack, is called the foot.

A windsurfing sail is tensioned at two points: at the tack (by downhaul), and at the clew (by outhaul). There is a set of pulleys for downhauling at the tack and there's a grommet at the clew. Most shape is given to the sail by a very strong downhaul, bending the mast in the luff tube. The outhaul tension is relatively weak, mostly to provide leverage for controlling the sail's angle of attack.

What's more, the sail is tuned by adjusting the downhaul and the outhaul. As a rule, the sail has to be trimmed more for stronger winds. More downhaul tension loosens the upper part of the leech, "spilling" the wind at the gusts and shifting the center of effort of the sail down. Releasing the downhaul tension shifts the center of effort up. More outhaul lowers the camber/draft, making the sail flatter and easier to control, but less powerful, and less outhaul brings more overall depth to the sail, more low-end power, shifts the center of effort upward and to the front, and may limit speed by increasing aerodynamic resistance.

Each sail has its own characteristics and is used for different disciplines of windsurfing: wave, freestyle, freeride, race. Wave sails are reinforced to survive the surf, and are absolutely flat when depowered to allow riding the waves like surfers do. Freestyle sails are also flat when depowered, and have high low-end power to allow quick accelerations. Freeride sails are all-rounders that are comfortable to use and are meant for recreational windsurfing. Racing sails, obviously, provide speed at the expense of qualities like comfort or maneuverability.

To conclude, the size of the sail is measured in square meters and can be from 3m² to 5.5m² for wave sails and from 6m² to 13m² for racing sails, with ranges for freestyle and freeride sails spanning somewhere between these extremes. Learning sails for children can be as small as 0.7m² and racing sails being up to 13m² large.

First of all, do you know what windsurfing is? Windsurfing, also called boardsailing, is a sport involving travel over water surface on a small 2-4.7 meter windsurf board powered by wind acting on a single sail. The rig is connected to the board by a free-rotating flexible joint called the Universal Joint (U-Joint). Unlike a rudder-steered sailboat, a windsurfer is steered by the tilting and rotating of the mast and sail as well as tilting and carving the board. This method of controlling the board's direction is called the free-sail system.

The sport is a hybrid between sailing and surfing, along with a number of athletic aspects shared with other board sports like skateboarding, snowboarding, waterskiing, wakeboarding and kitesurfing. Although it might be considered a minimalistic version of a sailboat, a windsurfer offers experiences that are outside the scope of most other sailing craft design. A windsurfer holds the world speed record for sailing craft and, windsurfers can perform jumps, inverted loops, spinning maneuvers, and other "freestyle" moves that cannot be matched by any sailboat. Windsurfers were the first to ride the world's largest waves, such as Jaws on the island of Maui, and, with very few exceptions, it was not until the advent of tow-in surfing that waves of that size became accessible to surfers.

Windsurfing includes wave sailing, speed sailing, course racing, slalom, superX, and freestyle as distinct disciplines. Windsurfing is possible in winds from near 0 to 50 knots, however the ideal planing conditions for most recreational sailors is 15-25 knots, with lighter winds resulting in displacement mode sailing.

Lessons can be picked up in a school. With coaching and favorable conditions, the basic skills of sailing, steering, and turning can be learned within a few hours. Competence in the sport and mastery of more advanced maneuvers such as planing, carve gybing (turning downwind at speed), water starting, jumping, and more advanced moves can require lengthy practice.

Windsurfing, as a sport and spare time activity, did not occur until the later half of the twentieth century. Because of the financial stakes in the manufacture and sale of windsurfing equipment, there has been considerable dispute and litigation between parties claiming the rights to the invention. Different courts in different jurisdictions have recognized different inventors, clouding any possibility of clear attribution. However, what is clear from the historical record is that windsurfing, as it is known today, owes much if not all to the promotion and marketing activities of Hoyle and Diana Schweitzer. In 1968, in Southern California, they founded the company Windsurfing International to manufacture, promote and license a windsurfer design. Together with Jim Drake, an aerospace engineer at the RAND Corporation, they were the holders of the very first windsurfing patent ever, which was granted by the USPTO in 1970, after being filed in 1968. They also originated the term "Windsurfer," which was registered to them as a trademark by the USPTO in 1973. A sailing craft utilizing two surfboards supporting a frame, sailing rig and steering mechanism was patented by Michael Kiefer in 1966.

The Drake and Schweitzer invention was a surfboard-like board with a triangular "Bermuda" sail and wishbone booms, connected to the board via a universal joint. The details of the original designs are available in Drake's whitepaper on windsurfing. Also, the history of the invention is discussed in these interviews with Jim Drake. Despite forty years of subsequent development, this apparatus is remarkably similar to windsurfing equipment in use today, and the word which Drake and Schweitzer coined to describe their invention has become eponymous with the sport itself. There is no evidence that they had knowledge of any prior inventions similar to theirs.

Windsurfing International created the Windsurfer as a one-design class. Going one-design was influenced by the success of the Laser and Hobie Cat classes. Each Windsurfer had an identical computer-cut sail, a technology new at that time and pioneered by Ian Bruce and the Laser class. Later Windsurfing International produced other development board sails, so as not to be left behind with the quickly evolving sport.

Drake hand over his patent rights to Schweitzer in 1973. Through the seventies, Schweitzer aggressively promoted and licensed his design to manufacturers worldwide, and the sport underwent very rapid growth in Europe. At the same time, Schweitzer also sought to defend his patent rights vigorously against unauthorized manufacturers. This led to a host of pre-dating windsurfer-like devices being presented to courts around the world by companies disputing Windsurfing International's rights to the invention.

Schweitzer sued Tabur Marine, the precursor of Bicsport, which is still a major manufacturer of sailboards and other marine recreation equipment today. In Windsurfing International Inc. v Tabur Marine (GB) Ltd. 1985 RPC 59, British courts recognized prior art by Peter Chilvers, who as a young boy on Hayling Island on the south coast of England, assembled his first board combined with a sail, in 1958. Intended to be steered by a rudder, it did not incorporate the curved wishbone booms of the modern windsurfer, but rather a "straight split boom". The courts found that the Schweitzer windsurfer boom was "merely an obvious extension". It is worthy of note that this court case set a significant precedent for patent law in the United Kingdom, in terms of Inventive step and non-obviousness; the court upheld the defendant's claim that the Schweitzer patent was invalid, based on film footage of Chilvers.

In 1983, Schweitzer sued Swiss board manufacturer Mistral, which also continues as a major manufacturer of sailboards. However Schweitzer lost the case. The Mistral defense hinged on the work of US inventor Newman Darby, who in the mid-sixties conceived the "sailboard" a hand-held square rigged "Kite" sail on a floating platform for recreational use. Darby's published version did not show any connection between the rig and the board but it did refer to a "more complex swivel step for advanced riders not shown". He published his "sailboard" design in August 1965 Popular Science magazine. Darby organized Darby Industries, Inc. in 1964 to build what they called sailboards. However, the "sailboard" never gained popularity, and Darby's company ceased operations by the end of the sixties. Eventually US courts recognized the Schweitzer windsurfer as an obvious step from Darby's prior art. Schweitzer had to reapply for a patent under severely limited terms, and finally it expired in 1987. Shortly thereafter, having lost its license royalty income, Windsurfing International ceased operations (see interview with Hoyle Schweitzer). For their part, Australian courts, in a 1983 patent case reported in "Intellectual Property Reports" 3 IPR 449, attributed the first legally accepted use to an Australian boy, Richard Eastaugh. Between the ages of ten and thirteen, from 1946 to 1949, aided by his younger brothers, he built around 20 galvanized iron canoes and hill trolleys which he equipped with sails with split bamboo booms. He sailed these near his home on the Swan River in Perth. There is no evidence that any of the later "inventors" ever sighted the Eastaugh craft of a decade earlier on the other side of the world. It is known that the Eastaugh, Chilvers, and Darby inventions all pre-dated the Drake and Schweitzer invention. However, the popularization of windsurfing would not have taken place without the efforts of Schweitzer. The prior inventions simply lay forgotten until they re-emerged in legal defenses in opposition to litigation by Schweitzer.

Windsurfing bring about the development of scoring programs on first portable computers. Because Windsurfing regattas were drawing a large number of competitors at remote locations, Windsurfing International sponsored the development of software running on portable computers to score regattas, starting with the 1976 World Championships in the Bahamas. The software, named OSCOR, was developed for the HP9825 and later ported to the TRS-80. The OSCOR software was finally donated to the United States Yacht Racing Union. The boom of the 1980s led windsurfing to be recognized as an Olympic sport in 1984. Though, windsurfing's popularity saw an intense decline in the mid-1990s, as equipment became more specialized, requiring more expertise to sail. Nowadays the Windsurfing sport is undergoing a modest reawakening, as new beginner-friendly designs are becoming more and more obtainable.