Stephen Bourn

Private individual;

New sailing theory produces ultimate wing borne hydrofoil

A radical new sail craft design promises a quantum leap in performance for all courses and conditions. A tilted wing, one tip almost skimming the waves, pulls obliquely against a single scythe-like hydrofoil, trailing a fine spray as it slices the water. The air-borne cockpit is suspended between. The design followed a theoretical breakthrough. International patents have been granted.

Project description

A revolutionary new sail craft design has the potential to shatter the full range of performance expectations set by conventional yachts, skiffs, catamarans, sailboards and kites. Top speed will be more than twice the wind speed, and it will sail upwind and downwind faster than the wind. The craft will challenge the world speed sailing record, set by an extreme purpose built craft that sails in one direction only on a unique flat-water course. The new craft will be able to sail in all directions and in open unsheltered water.

A single inclined wing-like sail connects from its centre via a long slender beam to a single hydrofoil. The hull connects to the beam in between. With sufficient wind and speed the hull will lift completely off the water. The craft will fly, leaving only the submerged hydrofoil cutting the water. The fine curtain of spray thrown up by the hydrofoil struts will be the only testimony to the staggering speed. The sail and hydrofoil are pivoted to allow the pilot full control, via two joysticks, over the height, speed and direction of the craft.

Normal sail craft rely on some angle of cross wind blowing over a sail to drive them forwards. As the boat moves forward the wind seems to swing forward and become more head on. The geometry of forces then conspires to limit the maximum speed. More force from increased sail size could help, but conventional craft would eventually capsize. The design of the new sail craft means that it is inherently stable, and will not capsize as sail force increases. Furthermore, with the weight of the airborne hull supported largely by the inclined wing, the drag is much lower. The result is much higher maximum speed.

The initial design is for a craft with an eight-metre wingspan carrying a single pilot. The craft will fly at remarkable speeds whenever the wind exceeds 15 knots. In less wind, high performance hull borne sailing is still possible. The craft will be launched from the beach, and be self-righting. The cloth wing will collapse quickly and easily for transport by trailer.

A prize winning technical paper has been written explaining the theoretical breakthrough. International patents have been granted for the sail craft design concept. Thorough analysis and computer simulation has been undertaken. The design concept is being proven on a series of radio-controlled models.

Evidence of Quality

Amateur Yacht Research Society (AYRS)-Hogg Memorial Prize, second place announced at the London Boat Show in January 2002

Australian Patent No 750,682 granted 28 November 2002

United States Patent No 6,675,735 dated 13 January 2004

An abridged version of the October 2001 technical paper was published in the AYRS Catalyst Journal, January 2002. Photos and video were displayed at the January 2002 London Boat Show.