Defence Scientist Designs World Record Sail Craft

An Australian defence scientist has created the design for a revolutionary sail craft, based on a wing-borne hydrofoil concept, which he believes will break the world sailing speed record.

Appearing to gain its influence more from flight design rather than sailing the craft looks like a cross between an aeroplane and a sailing boat; imagine a catamaran with a beam and no trampoline and a much smaller second hull. Underneath this smaller second hull is a scythe-like hydrofoil and is the only part of the craft that doesn't lift out of the water.

Stephen Bourn, a mathematical scientist with the Adelaide-based Defence Science and Technology Organisation (DSTO), says his design will allow the craft to travel at more than twice the speed of the wind in which it is sailing.

He also believes the design has potential applications for Defence, including wings for lightweight unmanned aircraft and high-speed hydrofoils for naval boats. He has a degree with honours in mathematics from the University of Adelaide and is currently completing a PhD in pure and applied maths.

The theory has been proven on a series of radio-controlled models. The craft incorporates a wing-like sail, submerged hydrofoils and a cockpit for one 'pilot'.

"With sufficient wind and speed the hull will lift completely clear of the water surface, the craft will fly, leaving only the submerged hydrofoil struts cutting the surface," Mr Bourn said.

"The air-borne hull means much lower drag," he said. "The relative positioning of the wing, hull and hydrofoil is inherently stable and there is no risk of capsize as sail force increases, unlike conventional craft. This allows a much higher power-to-weight ratio, and combined with lower drag, the result is much higher maximum speed."

Mr Bourn believes the new design has the potential to shatter the full range of performance expectations set by conventional yachts, skiffs, catamarans, sailboards and kites, and to challenge the outright speed record.

The initial design is for a craft with an eight-metre wingspan. The craft will fly at a maximum speed exceeding 30 knots whenever the wind exceeds 15 knots. It will sail upwind and downwind faster than the wind. The sail and hydrofoil are pivoted to allow the pilot full control, using two joysticks, over the height, speed and direction of the craft. The craft will be launched from the beach, will be self-righting and transported by trailer.

"The idea came from a fresh look at the basic principles of sailing, and the absolute limits to performance," Mr Bourn said. "Almost as a revelation, I discovered a new fundamental 'law of motion' applicable to all sail craft."

Mr Bourn has written a prize winning technical paper and has been granted international patents. He has undertaken thorough analysis of the design, simulating its performance on computer.

The single hull is where the pilot sits controlling the height, speed and direction of the craft by two joysticks. 'The positioning of the wing, hull and hydrofoil is inherently stable meaning, unlike conventional craft, there is no risk of capsize as the sail force increases,' says the sailor-scientist.

'It can be launched from the beach and the cloth wing collapses quickly and easily for transport by trailer.' If tests on the full sized craft prove successful, the next sailing craze could be hitting our shores soon.