Foiling sailboats have appendages placed under the hull which help lift the hull out of the water making the vessel fly; this drastically reduces hydrodynamic drag and increases speed, writes Saša Fegić.

Importantly, it also has a wow effect.

Comparing a foiler to a Jeanneau Sun Odyssey is like comparing a Formula 1 car to a Toyota Corolla.

A few years ago, while sailing around the world, I stopped at Fiji’s Vuda Marina. In a bar after a few drinks, I had a long discussion with a fellow cruiser about foiling.

The German retired pilot was convinced that it was just a matter of time until we would all fly above water.

He said it might take a while, but computers would soon allow boats to zoom effortlessly across oceans. “The weather routing will give us the best time to start and which route to take to be fast and to avoid all the storms, and onboard computers will take care of the foils and sails. It will be great!” he told me.

Back then I wasn’t convinced.

Recent developments, however, have made me re-examine my position on the matter. So let’s start from the beginning…

How foiling works

Foils use the same principles as aircraft wings. Just as an aircraft wing will lift a plane off the ground, the foils will lift the boat out of the water by using a special shape to guide the water around them and generate the lifting force to get boats flying up in the air.

Initially, the sails are set up as on a normal yacht.

Once they generate enough speed and the amount of lift exceeds the boat’s weight, it will pop out of the water almost instantly. The magic happens in a matter of seconds.

Once the boat is flying, it can achieve speeds exceeding double and even triple the wind speed.

How to control the flight

Once the boat is up in the air there’s a danger it could flip backwards. This is why the foil has to be raked backwards as the boat accelerates.

This will reduce the lift and the boat will come to an equilibrium at a steady height above the water. Sounds easy.

But if conditions change, like the wind speed going up or down, or the boat hits some waves, then the rake will need further adjustment to find the new equilibrium.

Foils have to be raised and lowered through bearings and internal mechanisms in the hull.

This means a lot of power to operate them and a lot of work to keep the friction down and the efficiency high.

History of foiling

The early development of hydrofoils started over 100 years ago when Italian Enrico Forlanini achieved 36.9 knots with his 60hp airscrew-driven boat in 1906.

The first patent for hydrofoil was for a rowing boat in 1869 made by Frenchman Emmanuel Denis Fargot and the first known sailing hydrofoil was produced by Americans R Gilruth and Bill Carl in 1938.

In 1955, the hydrofoil sailboat Monitor recorded a speed of 25 knots. It was designed by Gordon Baker and built by his firm, the Baker Manufacturing Company of Evansville, Wisconsin, with financial input from the US Navy.

Monitor had cotton sails and could foil in 13 knots of wind on two ‘ladder foils’ forwards and a submerged foil aft.

In 1980, the legendary Frenchman Éric Tabarly sailing the offshore foiling trimaran Paul Ricard beat Charlie Barr’s 75-year transatlantic record by more than two days.

Barr’s record of 12 days, 4 hours, 1 minute and 19 seconds was achieved in 1905 aboard the three-masted schooner, Atlantic.

These early successful concepts were ahead of their time and were ignored by mainstream boat designers.

That was until relatively recently when foils were introduced to the 2013 America’s Cup, with teams competing for the first time on wingsail foiling catamarans.

These were followed by the AC50, AC62 and AC75 foiling catamarans; the last of these designs were most recently raced in the 2024 America’s Cup, although the AC75 design was slightly tweaked to improve light wind performance and crew numbers were reduced from 11 to 9.

The 2016 Vendée Globe saw the first foiling ocean-going IMOCA 60 class boats.

When foiling boats came to Class Mini 6.5 it opened up a world of opportunities for designers and sailors.

The class allows T-foils on their rudders, giving rise to the prospect of a full flying boat that is cheaper than any other.

Production series foiling yachts

Pogo Foiler

French builder Pogo designed the Foiler to match the Class Mini prototype rules, with T-foils and a canting/telescopic keel.

The boat’s flight can be controlled with the rudder T-foils that move in all directions.

The Guillaume Verdier design is based on the monohulls of the America’s Cup.

Beneteau Figaro 3

The class was launched in 2018 and became the world’s first foil-assisted series-build production monohull.

However, the foils on the Figaro 3 are not designed to lift the boat out of the water but to eliminate the need for water ballast by creating side force to help the keel.

ClubSwan 36

Nautor Swan also decided to try foiling. Their yacht, like the Figaro 3, isn’t meant to fly but to be more stable and go faster.

The one-design ClubSwan 36 has a simplified foil system with a large single circular C-foil that slides to a variety of depths through a watertight case inside the boat.

This generates both horizontal and vertical forces based on boat speed and heel angle, helping to deliver power and planing.

Retrofitting

Installing foils on old dinghies is also an option now. You can buy foiling kits suitable for the Optimist, Laser, Aero, Open Bic and Melges 14 dinghies.

Some manufacturers state these foiling kits can be fitted in 10 minutes; you can then rig your dinghy and go!

But is it possible to retrofit hydrofoils onto a monohull? Anything is possible in absolute terms. But would it be economic or sailable?

That’s a completely different question. Some enthusiasts are trying in their garages to put foils on old boats with various results, but we’re still waiting to see a great success story.

Cruising

In the late 1960s and early 1970s, David Keiper cruised 20,000 miles through the South Pacific on his 32ft hydrofoil sailing yacht, Williwaw.

His book, Hydrofoil Voyager, was part cruising log, part technical manual, but the idea of a cruising yacht with hydrofoils never gained traction, although he did sell a small number of retrofit hydrofoil kits for catamarans.

In 2015 luxury catamaran builder Gunboat launched the Gunboat G4, a foiling high-performance cruising catamaran with comfortable cabins, easy sailing characteristics and room for all the family.

The foils were advertised to deliver comfortable speeds of 20 knots in 12 knots of wind, with a top speed of up to 40 knots.

Although the multihull was launched with much fanfare and was raced (notably in Les Voiles de St Barths in the Caribbean, where it capsized on the final day), foiling cruising catamarans have not become mainstream, although it is likely only a matter of time before a similar concept will appear again.

Baltic Yachts launched a 111ft superyacht in 2023, the first of her size and type to use foils mounted on adjustable side arms.

It isn’t designed to fly, but to sail on her chine with the leeward foil supporting a large proportion of her displacement.

Early sea trials have been described as ‘very successful’, reaching sustained speeds ‘in the high 20s.’

What’s next?

The development of computers and sophisticated software is expected to be a major factor in the production of foiling cruisers.

Automated control and self-adjustment of the foils are necessary to avoid crashes.

LiDAR (Light Detection and Ranging), a remote sensing method that uses a pulsed laser to measure ranges, is already being used on autonomous craft and commercial boats to scan the water and surrounding area to gather information about the sea state and objects in the water in front of the boat.

Yachts in the future could have a central motherboard which calculates the right set-up for the foils and sails for any circumstance – winches, lines and crew replaced by computer-controlled hydraulics.

But computers can fail, which at high speed could be fatal.

Conclusion

You can’t stop progress.

But cruisers are generally an old-school bunch.

Even now, you can buy a proven, fast series production yacht capable of long-distance cruising, like a Pogo, but the vast majority of cruisers would still rather choose a more old-fashioned and seaworthy vessel like a Hallberg-Rassy.

Every boat is a compromise and cruisers generally prefer comfort over speed; it is likely that using foils for control and improved performance, rather than full-on ‘flying’ will find its way into more mainstream designs in the future.

As is the case with cars, everyone would love to drive a Ferrari, Lamborghini or Bugatti, but only a very few get a chance and even fewer people drive them daily.

I’d love to try foiling.

Flying above water powered by the wind must be a great feeling, but for cruising, I’d still choose a Hallberg-Rassy over a foiler.

Pros and cons of foiler-cruisers

Pros

• Speed When out of the water, these flying machines can achieve great speed, unimaginable for normal boats. Being that fast is thrilling and can give you more cruising options.
• Smooth ride In theory, if the boat is flying above the water, it should give a much smoother ride than a displacement yacht rolling up and down the waves. Anyone who has watched footage of the Vendée Globe skippers may disagree!
• Avoiding storms Being fast means good weather routing software can guide you easily away from storms and safely to the next destination.

Cons

• Cost The complex systems of computers, hydraulics and electrics, foils and a boat that will need to be structurally reinforced with carbon fibre means that a foliing cruiser will be extremely expensive.
• Foil challenge The foil system will take up interior space, impacting accommodation down below. Docking the boat and safe mooring with appendages sticking out from the hull will also present a challenge.
• Vulnerability Thin, razor-sharp foils cutting through the ocean at great speed could easily break if they hit even a tiny piece of debris. High power consumption means a reliable source of power is necessary.

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