A Frenchman at the helm of a “flying yacht” and a kite surfer are locked in a race to become the fastest through the “wind barrier” of 50 knots – nearly 60mph.

Alex Caizergues, 29, from Marseilles, made nautical history off the coast of Namibia last week when he broke the record for wind-powered craft by keeping up a speed of 50.57 knots (about 58mph) over 500m with his kite surfboard.

A few days before that, Alain Thébault, 45, had reached 52 knots in southern France, albeit over a shorter distance that did not qualify for a record.

His craft, the Hydroptère, is a trimaran whose unusual design, he claims, gives it the acceleration of a sports car.

The destruction of the “mythical wall” of 50 knots, which Thébault compared to the sound barrier in flying, has been hailed as a great French accomplishment.

Thébault expected to break Caizergues’s record before the end of this month aboard what he calls his “flying carpet”: instead of ploughing through the waves, the Hydroptère rises on “wings” to glide over them.

“Speed has always been a factor of progress for mankind,” said Thébault. “What is the limit? Who knows? After 50 knots we are facing the unknown.”

Caizergues was elated by his entry into the record books at the Lüderitz Speed Challenge in southern Namibia last week. “I’ve been training for this for four years,” he said. “I can hardly believe it.”

Subject to verification by the World Sailing Speed Record Council, he will be hailed as the “fastest sailor” in history, even if some sailors grumble that kite surfers should have their own category because their parachute-style wing bears little resemblance to a sail.

Thébault, a former surfer, was the first to congratulate his kite surfing friend, but does not intend to let Caizergues’s record stand long.

Already the 60ft Hydroptère has crossed the Channel in 37 minutes, not much more than it takes the Eurostar train to go under it and faster than the 40 minutes it took Louis Blériot, the French aviator and the first person to fly over it, from Calais to Dover, in 1909.

Thébault believes nothing except unfavourable weather can hold back the Hydroptère. A breeze of 12 knots (14mph) is enough for “take-off”. The boat rises up to 15ft out of the water on carbon fibre ailerons that descend from the outer keels.

Only the tips are left in contact with the sea and the drag of the vessel is reduced to almost zero, allowing it to hover over the waves. Hence the “flying carpet” comparison.

A “panic button” will bring the vessel to a halt if too strong a gust risks capsizing it. The vessel has suffered several near-calamitous accidents in trials over the past few years.

“Speed is always dangerous,” said Thébault. “Thrilling, but dangerous.” Building a “flying yacht” has been his ambition since childhood.

Politicians, captains of industry and a dozen retired aeronautical engineers from Dassault and Airbus have helped him to make it a reality, along with the backing of Eric Tabarly, a French yachtsman, and Thierry Lombard, a Swiss banker.

Kite surfing, by comparison, seems uncomplicated and its practitioners need no backers.

“My board cost only a few hundred euros and the kites – they virtually give them away,” said Sébastien Cattelan from Toulouse, who was the first to officially cross the wind barrier on October 3 in Namibia with a speed of 50.26 knots. The record was snatched from him by Caizergues five days later.

Cattelan said there was little to compare with the thrill of being pulled by a kite at close to 60mph over the water on a surfboard. “You get the acceleration of a Porsche 944,” he said.

For Thébault, crossing the 50-knot barrier is not enough. “I’ve always wanted to cross the Atlantic on my flying boat.”

He hopes to make the attempt next year. The aim is to beat the record of four days, three hours, 57 minutes and 54 seconds set by the French trimaran Groupama 3.

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