Lift-off for speed record

A trimaran using advanced hydrofoil technology will attempt to break the world 50-knot sailing record. George Coupe reports.

According to legend, when the mistral wind screams down the Rhone valley in winter, it turns people mad. Once a source of fear, the elemental force of this torrent of air flowing south to the Mediterranean, will this year be harnessed in an attempt to break the world speed sailing record.

The goal is to smash the 50 knots (58mph) barrier but, like the most famous water speed records, this exploit is not without danger or a touch of madness. One leading vessel preparing for the attempt will literally fly above the waves, risking destruction without warning.

Hydroptere is a 60ft trimaran which, on reaching a speed of about 12 knots, is designed to lift all its hulls out of the water simultaneously to reduce drag; it planes along 5m above the surface on two hydrofoils that extend at an angle down into the water from the outer stabilisers.

The ‘flying yacht’, as it has come to be known, was conceived in 1975 by a team of French aeronautical engineers, aircraft part manufacturers and sailors. Since then, with the support of a range of engineering companies and in collaboration with the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, the project has gathered record-breaking momentum.

After crossing the Channel in 34 minutes and 24 seconds in 2005, the yacht set two world speed records last year: a category record for speed over a distance of 500m with an average of 44.81 knots, and a new all-category record of 41.69 knots for the nautical mile.

Led by skipper Alain Thébault, the team has been modifying the boat in Brittany for an attempt on the absolute sailing speed record. Until earlier this month this was held by the Irish windsurfer Finian Maynard, who reached 48.7 knots on the Canal des Saintes Maries de la Mer in 2005. But on March 5, on the same canal built for the purpose, Antoine Albeau set a time of 49.09 knots, also on a sailboard.

This month final preparations were being made to transport Hydroptere down to Vieux Port, Marseille. The team has chosen a stretch of “flat” water nearby at Port Saint Louis du Rhone, where the mistral blows constantly at 30 knots-35 knots off the land, as the place where it will try to win the title of the fastest vessel on the planet and be the first to break the 50- knot barrier, a goal likened to breaking the sound barrier in yachting circles.

Hydroptere’s website proclaims: One thing is certain, 2008 is the year of the absolute sailing speed record… There are too many contenders and there is too much motivation for the record to remain at its current level. The whole community is dreaming of sailing at 50 knots.

That community includes two other contenders making serious bids for the record this year. SailRocket, a two-hulled, UK-designed boat, has been in Walvis Bay, Namibia, since the end of February, hoping to capitalise on favourable conditions, which have not yet materialised. And Macquarie Innovation, a multi-hull Australian yacht, reached top speeds of 44 knots last year and will try again this year.

Both yachts are extremely lightweight and intended solely for breaking speed records in calm waters. If either breaks the 50-knot barrier they will do so with at least one hull firmly in the water.

By comparison, Hydroptere claims to be the only yacht in the race capable of sailing at speed offshore in rough waters as well as taking part in pure speed trials. In calm waters, the team claims it has already reached speeds of more than 45 knots.

The 60ft trimaran Hydroptere is designed to lift all its hulls out of the water simultaneously to reduce drag when it reaches a speed of about 12 knots

Hydroptere is not the first yacht to be equipped with hydrofoils that lift the boat out of the water. The concept dates back to before the Wright Brothers, who used booster planes to lift a catamaran clear of the waves in 1907. While there have been many attempts at the ‘flying yacht’ since, it was only with the advent of composite materials, that combine extreme lightness with extreme strength, that larger-sized boats such as Hydroptere could be built.

Hydroptere remained an idea for many years, only making its first flight in 1994 as a viable prototype, nearly two decades after its inception.

The boat’s foils, which produce the vertical thrust as they move through the water, could only perform if they were made from carbon and titanium composites. Conventional materials such as aluminium could withstand the extreme stresses involved in lifting the boat, but would make it too heavy to clear the water in the first place.

Meanwhile, with the aid of specially developed simulation software, the geometry of the foils was conceived to limit the increase in lift so the boat stops rising and stabilises a few metres above the water. ‘As soon as the wind speed is over 11 or 12 knots l’Hydroptere works like a plane,’ said Jean-Mathieu Bourgeon, the boat’s research and development manager. ‘Her foils are like wings that generate lift as soon as she increases her speed. The floats come out of the water and the drag is reduced, which permits it to reach a very high speed.

‘At that point the boat is flying on the support of only three points, the main foils at the end of each crossing arms, and the rudder at the rear of the boat, with the horizontal foil at the end of it. This T-foil permits us to control the pitch of the boat, exactly like the rear wings of a plane.’

After setting two speed records last year, the team has decided to reconfigure the boat solely for speed to make an attempt on the 50-knot title. Much of this work was done in collaboration with EPFL. Bourgeon, who leads the joint Swiss-French design team, said they have made changes to the yacht’s rigging and sails, but most importantly the design of the hulls and foils.

‘We have worked on several points to achieve our goal,’ he said. ‘We have streamlined most of the parts of the deck and principally the arms. But we have also modified the full rig of the boat. We have a new mast and sails which are designed specially for the wind speed we need to make the record.’

This has meant shortening the mast and boom to lower the centre of sail thrust. But most important, the team has focused on optimising the boat’s hydrodynamics, its special ingredient.

And at boat speeds close to 50 knots, a new challenge appears: cavitation, which occurs when the low pressure around the foils transforms water into a stream of bubbles.

Bourgeon explained the problems caused by this phenomenon: ‘We first have a reduction of the lift, which could be very dangerous because it could destroy the stability of the boat, and we have an increase in the drag of the boat. This phenomenon could be considered like the sound wall was for aviation.

‘We have done important work to change our profiles in order to delay the onset of the cavitation. This modification of our foils and rudder should permit us to break the 50-knot barrier. Our new potential is even higher than 50 knots. We will see that in May.’

Onboard stress monitoring has greatly helped in the boat’s development and its capability to sail at speed in heavy seas. Bourgeon said: ‘The analysis of our measurements taught us that we could always meet stronger seas, which could break the boat even if the structure is made stronger and stronger. So in 2004 we set in place shock absorbers on our foils, and this permits us to sail in very rough seas at high speed without having to increase the strength of the boat.’

Bourgeon firmly believes boats such as Hydroptere are the future of sailing. ‘Thanks to the work of all the team and the willpower of Alain, we are now very close to our goal. More and more people recognise the values of this concept. No other project could bring such satisfaction to me. It’s so interesting to imagine solutions, to set it in place on the boat, to test it during extraordinary sailings, and then maybe to write a new line in the history of sailing.’

The collaboration with EPFL has given birth to other variants of the Hydroptere, aimed at developing a vessel capable of taking part in the great ocean races and even circumnavigation.

The Hydroptere maxi, as it is known, would be larger (30m) in order to cope better with rough seas. It is being designed with the goal of slashing the round the world record from 50 days to 40. Alinghi, the America’s Cup-winning team, has reportedly shown interest in using the Hydroptere in future races.