Foiler: Did You Ever See a Flying Boat?

In 1906, on Lake Maggiore, a boat lifted clear of the water and ran at 68 km/h. No carbon fibre, no computer, no hydraulics. That is the number I keep coming back to whenever someone describes foiling as a recent invention, because the idea is older than the aeroplane’s first decade and it took a century to become ordinary.

What a foil actually does under the hull

A hydrofoil is a wing, mounted on a strut below the hull, working in water instead of air. Water is roughly eight hundred times denser than air, so the wing can be small and still produce enough lift to raise several tonnes once the boat is moving.

The gain comes from what disappears rather than what is added. A displacement hull spends most of its power pushing water aside and dragging a wetted surface through it. Lift the hull out and almost all of that resistance goes with it, leaving only the foils and the strut in contact. Above the take-off speed, the boat also stops slamming into waves and starts passing over them, which is why foilers feel eerily smooth at speeds that would be punishing on a conventional hull.

The cost is complexity, and it is real. Foils add structure, weight and expense to the build, they need control over pitch and ride height, and they are unforgiving when they touch something. A foiling craft demands proper instruction before you take one out, and that is not a formality.

A hundred and twenty years of the same idea

The precursor was the Italian aeronautical engineer Enrico Forlanini (1848 to 1930), who had been modelling hydrofoils since 1898. His full-scale craft used a ladder arrangement of foils, a 60 hp engine and two counter-rotating air propellers, and on Lake Maggiore in 1906 it reached 68 km/h.

The story then jumps continents. During his world tour of 1910 and 1911, Alexander Graham Bell rode in Forlanini’s boat on that same lake with Casey Baldwin. The HD-4 they went on to build reached 87 km/h, and once the United States Navy supplied two 350 hp Liberty engines it recorded 70.86 mph, or 114.04 km/h, on the Bras d’Or Lakes at Baddeck on 9 September 1919. That world marine speed record then stood for two decades.

Racing pushed it, and racing still does

The America’s Cup catamarans that first showed their foils to a wide audience have since been replaced by something stranger. The AC75 is a foiling monohull of roughly 23 metres carrying articulated foil arms and a flexible wing rig, and it has redefined what a big single-hulled yacht looks like under way.

The most recent edition settled in Barcelona on 19 October 2024, where Emirates Team New Zealand beat INEOS Britannia seven races to two for a third consecutive win. The 38th America’s Cup moves to Naples, with the match due to begin on 10 July 2027, again in AC75s.

Alongside it, SailGP runs identical F50 catamarans that keep resetting the ceiling. The league record now stands at 56.1 knots, 103.93 km/h, set by the Rockwool Denmark team at the Germany Sail Grand Prix in Sassnitz in 2025. For scale, that is roughly three times the speed of a typical cruising yacht at full tilt.

The quiet part: foils on a commuter route

The most interesting foiler afloat right now carries commuters rather than sponsors. Candela’s P-12 has been part of Stockholm’s public transport since autumn 2024, running between Tappström on Ekerö and the City Hall in the centre. It cruises at 25 knots with a top speed of 30 and a range of 40 nautical miles at cruise, and by lifting the hull clear it uses around 80 per cent less energy than a conventional vessel of comparable duty, according to the builder.

The passenger-facing gain is time. Candela puts the crossing at about 30 minutes against roughly an hour by car or bus, and Region Stockholm extended the service to daily operation from May 2025 after the pilot phase. That is the moment foiling stopped being purely a performance trick and became an efficiency argument.

Where to see one in the flesh

The best way to understand a foiler is to watch one take off from the shore, and France has a gathering built for exactly that. La Semaine Affoilante at Port-Fréjus brings together kitefoils, windfoils, foiling boards, catamarans and trimarans for several days of racing and demonstrations, with the fourth edition held from 14 to 17 June 2018 and a later one in April 2022.

One honest caveat: I could not confirm a scheduled 2026 edition when checking in August 2026, so treat the event as a recurring fixture whose dates need verifying with the Fréjus tourist office before you plan a trip around it. Local sailing clubs on foiling waters are usually the faster route to a first ride anyway.

Do foils work on any boat?

No. The hull, the weight and the power available all have to suit the foil package, which is why foilers are designed around their foils rather than fitted with them afterwards. Retrofits exist on small craft, but they change the handling completely.

What happens if a foiler slows down?

It settles back onto its hull. Below take-off speed there is not enough lift to support the weight, so the boat simply becomes a normal, and rather draggy, hull again.

Are foilers safe in rough water?

They are efficient in a chop and unhappy in a steep, confused sea, where a foil can ventilate or break clear and drop the hull abruptly. Every foiling class runs to its own limits, and those limits are lower than most beginners assume.

Updated August 2026. Historical figures for Forlanini and for the Bell and Baldwin HD-4 are the commonly published records of those craft. America’s Cup results and the Naples 2027 schedule come from the event organisers, and the SailGP speed record from the league, all consulted in August 2026. Candela’s speed, range and energy figures are the manufacturer’s published claims. Foiling craft require training and this article is general information, not instruction.