Extraordinary boats: TF35 semi-automated foiler

The TF35 is a new one-design catamaran with a unique computer-controlled automatic foil system, that will race in the TF35 Trophy. James Boyd looks at the foiling catamaran

In recent America’s Cups we have seen a small army of grinders pumping away to bring pressure to their flying yacht’s hydraulic lifeblood, while flight controllers attempt to keep up with their speeding craft’s accelerations in three dimensions. But while these athletic and technical skills are impressive, these days there are simply better alternatives to humans carrying out these roles. Enter the TF35.

The TF35 is a new one design foiling catamaran created to take foil-borne sailing to the next level. It has no hydraulics to keep primed. Conventional ropes and winches handle the sails and raising and lowering of foils, but battery powered electric actuators drive the rest, including split-second adjustments of the foils and rudder elevators. What’s more, these operations are automated, leaving crew free to focus on skills such as helming and tactics.

The shape, size and efficiency of the TF35’s foils means it requires just seven knots of wind to take off upwind and nine downwind (when boat speed reaches 2x and 3x wind speed respectively). It also passes the acid test of foiling upwind and through tacks.

The racks increase righting moment but also protect the foils when alongside pontoons and improve crew safety. Photo: Loris von Siebenthal

A small penalty for having such light wind take-off is ultimate top speed, which is 18-19 knots upwind and 34-35 knots downwind, but still plenty fast enough.

After the prototype launched at the end of 2019, the new TF35 is enjoying its first full season of competition this year. The class follows on from the D35, the one design catamaran that provided sterling service on Lake Geneva for 16 years and countless Bol d’Or Mirabaud victories for Ernesto Bertarelli’s Alinghi, his sister Dona’s Ladycat-Spindrift and many others.

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