Researchers seek to sail into history

The Hydroptère is already the fastest wind-driven vessel around hydroptère.com

Scientists at Lausanne's Federal Institute of Technology are helping a revolutionary yacht project overcome one of sailing's biggest barriers.

The French Hydroptère hydrofoil vessel is already close to beating the 50-knot (92.6 kilometres per hour) mark.

A sleek multihull yacht sets out to sea, gathering speed. Then suddenly it climbs out the water, seemingly travelling through the air a few metres above the surface.

It is flying – well almost. What is keeping it up are hydrofoils, long struts that act like wings in the water. They push the yacht upwards as it goes faster, reducing drag as well as friction and maximising speed.

The hydrofoil concept has been around since the early 20th century. Italian inventor Enrico Forlanini tested the first motorised craft on Lake Maggiore, which straddles Italy and Switzerland.

The first commercial uses of a hydrofoil came in the 1950s, with the development by Swiss company Supramar of a passenger vessel, the PT10, that plied its trade on Lake Maggiore.

The Hydroptère project is a more recent twist on this concept. Since it was first launched 15 years ago, the yacht has demonstrated that hydrofoils can be used on sailing craft.

But its promoters want to go after one of sailing’s big targets – the 50-knot limit known as the wind barrier.

Wind barrier

Whereas unlike the sound barrier, there is no change in underlying physics at play, the fact remains that no wind-driven vessel has beaten the mark yet. The institute’s researchers have been working for the past two years to help the yacht break 50 knots.

They are not the first group of specialists to come to the aid of the French-based Hydroptère team. Defence and aerospatial giant EADS has already participated in the project.

The Swiss stepped in after Geneva banker Thierry Lombard offered his financial backing to help keep the Hydroptère afloat. Much of the scientific work has now moved to Lausanne, and the design team has set up shop at the nearby scientific park.

What the researchers are doing is helping tweak an already sound design.

“We aren’t working from scratch in this case,” explains Pascal Vuillomenet, spokesman for the project. “On the other hand, there are no limitations on what we can propose to improve the yacht.”

In this sense, the work differs to some extent from the institute’s previous work with the America’s Cup defender Alinghi.

“With the America’s Cup, you have to work within the constraints of the gauge,” adds Vuillomenet. “With the Hydroptère, the aim is to beat a record.”

Challenges

One of the major challenges is to overcome a phenomenon known as cavitation. As the hydrofoil moves faster, bubbles form around it, threatening to eliminate all lift and stop the yacht in its tracks.

“It would be extremely dangerous for the yacht and the crew if lift was suddenly to disappear,” says Mark Sawley, a senior scientist at the laboratory of computational engineering. “Water is very hard at that speed.”

This is one the reasons the revamped Hydroptère has not tackled the record yet. According to Sawley, the yacht probably could better the mark given the right conditions, but safety is considered more important.”

By modifying the hydrofoil’s shape, the researchers, backed by a computer cluster for simulations and an experimental laboratory for model testing, hope to eliminate cavitation.

But even if the hydrofoil itself is optimised, the yacht also needs to gather maximum power from the wind and to find its best sailing position. Video imaging comes into its own here.

“We have been for example able to supply them with a video system that allows to see how far the foils lift the yacht out of the water,” says Julien Pilet of the Computer Vision Laboratory. “They had tried other systems, but none of them have proven to be up to the task.”

Problems included vibration, salt water, spray to name but a few. Another challenge has been to find the optimal sail configuration for the yacht.

Solution

The solution that Pilet and his colleagues have developed is a single camera that can monitor sail movement in three dimensions.

“The idea is that we can tell the sail designer and the crew under which conditions the sails performed best,” Pilet told swissinfo. “Once we have recorded various tests, we can advise the crew on how they might want to set the sails.”

But Sawley admits that nobody wants to tell the crew or the builders how to do their job. “They ultimately decide what they want to implement,” he said.

The project is a promotional beacon for the institute.

“Engineering students are far more interested in getting their hands dirty with a real-life project,” adds Sawley. “And in this case the project management allows them to get really involved.”

The researchers could find out very soon if their work has paid off. The Hydroptère team is planning to tackle the record in the coming weeks, the final stage before the construction of a giant yacht to break the round-the-world mark.

swissinfo, Scott Capper in Lausanne

Pushing the envelope

1975: A team of aeronautical engineers, aircraft part manufacturers and sailors convince “father of French yachting” Eric Tabarly of the Hydroptère’s viability.

1987-1992: Alain Thébault builds a model on a one-third scale.

October 1, 1994: Hydroptère finally tackles the sea.

February 9, 2005: The symbolic record across the Channel set by Louis Blériot in 1909 is smashed by Hydroptère in 34 minutes and 24 seconds with an average speed of 33 knots.

April 4, 2007: Hydroptère sets two world records: fastest sailing vessel over one nautical mile with an average speed of 41.69 knots, and fastest over 500 metres in category D (sail surface area over 27.88 m²) with an average speed of 44.81 knots.