Leading French offshore sailor Sébastien Josse says he believes that designers and builders need to develop improved control systems for foils to be fit for extreme ocean conditions.

The solo sailor was forced yesterday to retire from the Vendée Globe after damage to the head of his port foil. Had it come loose it would potentially have broken the boat’s structure and placed him in a very dangerous position in a remote area of the Southern Ocean.

Read what happened to him.

He says that seeing these huge lift-generating foils simply as ongoing developments of the previous generation of daggerboards is wrong because of the immense loads they see and, in turn, create.

“Foiling monohulls are very different to the previous boats. With this Vendée Globe, the big teams have prepared the ground for everyone. There will need to be a debriefing before any real conclusions can be drawn…

“We’re here to make progress but I think we’ve not taken these technological advances as far as they can go and all treated this revolution as part of the usual changes from one generation to the next.”

Sebastien Josse (FRA), skipper Edmond de Rothschild

His new IMOCA 60 Edmond de Rothschild is one of a tranche of new designs sporting foils. The purpose and reason for them is explained in this article.

Read about why the latest IMOCA 60s have foils.

There is no question these foils have produced unprecedented speeds in the Vendée Globe – leaders Armel Le Cléac’h and Alex Thomson have set a clutch of new records in this race: fastest to the Equator, to the Cape of Good Hope and Cape Leeuwin and also Thomson’s new 24-hour record of 535 miles.

But the completely unknown aspect of these prototype foils was how they would behave in the extreme conditions of the Southern Ocean. Here, the forces are incalculably large and it could potentially be difficult to stop completely the foils from working and load bearing, even when skippers might need them to.

This point was recently made to us by Mike Golding who, for the first time in 16 years, is not taking part in the race and has been an interested observer. He thinks likewise – more work needed. At times, they may even be a hindrance.

“From the outside [foils are] an incredible increase in risk because of the span. Another thing is the foil is down in almost all circumstances,” he remarked to me recently.

“You can reduce the risks by bringing it in but can’t eliminate it, whereas a daggerboard is fully safe once retracted. The level of unreliability risk has jumped up immeasurably, if you actually sat down and did the maths.

“The foils can’t actively control the amount of lift so the faster you go more lift you get and there’s no way of controlling that, so when you’re doing 18-19 knots in waves, and a big wave picks you up and you’re surfing at 26 knots that’s a massive range of power.

“At the bottom end it’s just enough to work and at top end way too much, so boats are really hard to modulate and control the amount of power when you are in large wave set. That’s how I imagine it.”

Seb Josse is already talking about the need for foil control systems. “Controlling the foils and their systems must be thought out differently as the load they’re under are massive,” he said from the boat.

“We’ve missed the point on the concept because we thought about them as we did the classic daggerboard while now the boat is effectively supported on these appendages.”

Watch the video

For a startling demonstration of how these foils work, just take a look at this remarkable video of Seb Josse during training. Bear in mind that, during the Vendée Globe, none of the skippers would be wanting to push their boats nearly so hard but it shows that, once deployed, these foils see huge loads…