Foiling has really become a mainstream form of sailing in the last 15 years. Despite being a concept for a long time, it�s showcasing in the 34th America�s Cup and the increasing popularity of the International Moth class has raised the profile and increased accessibility to sailors. The 2020 Olympics in Tokyo will feature a foiling event for the first time in the form of the Nacra 17, which was modified to a fully foiling catamaran after the 2016 Olympics.
Foiling is when a boat sails above the water on its hydrofoils. In layman�s terms the hydrofoils work like an aeroplane wing under the water. When the boat reaches its take-off speed, enough lift is created from the foils to lift the hull clean out of the water. This massively reduces the drag as the hulls are lifted out of the water into the air, which is 1,000 times less dense. This big reduction in drag allows for a big increase in speed.
There are two common types of foiling boats. Boats like the Waszp and the Moth which use a �wand� controlling a flap on the trailing edge of the horizontal foil. This works very much like an aeroplane wing � when the boat gets close to the water, the wand makes the flap go down to create more lift.
The other common type of foiling is what we use on the Nacra 17 and is a more crude approach. The boat also self-regulates ride height, but this self-regulation relies on the shape of the foil and how much of it is under water. When the boat goes faster it lifts higher out of the water and the lifting area of the foils below waterline is reduced. We also control the flight of the boat by changing the angle of attack on the foils. This is done through pitch control (moving our body weight fore and aft) or by pulling a rope to put more or less rake on the dagger boards.
The better the control system, the more aggressive the shape of the foils can be. For example, the foils used in the latest America�s cup yachts were very �L� shaped, whereas the foils on a Nacra 17 or A-class are more �Z� shaped. An �L� shaped board is very unforgiving as the whole lifting surface comes out of the water at once. A �Z� shaped board is more forgiving because the lifting surface progressively comes out of the water as the boat gets higher. A forgiving design of foil requires less accurate control but also won�t be as fast because it�s not such an efficient way to create lift.
Foiling is an incredible way to sail and if you�re going to be having a go we have two top tips!
Tip 1: The take-off
Tip 2: Stable flight
Want to learn to foil? Find out more about the RYA Foiling courses at https://www.rya.org.uk/courses-training/courses/dinghy-multi-keel/Pages/foiling-courses.aspx or pick up a copy of the new RYA Foiling publication from the RYA shop www.rya.org.uk/go/shop