Windfoil Setup: How to Trim Your Sail, Board and Foil

Hydrofoil windsurfing really sucks. That's what you would say if your foil, board and sail weren't set up right.

A big chunk of windsurfers still haven't made the step onto the foil, and if they have, it's probably with a wing in their hands. I get it. It seems a bit scary and wiggly, it's another investment into your quiver, and it's hard to understand which foil you need and how to tune your gear. But just like when you started windsurfing, it's a struggle that really pays off. The right adjustments play a big, big role in wind foiling.

There's a lot of information coming, so I've split it into three parts: the rig, the board and the foil.

1. The rig: sail trim for foiling

Why a pure foil sail helps

Of course, a pure foil sail is a big help in flying steady. Foil sails are usually designed with a higher aspect ratio, which gives you less back-hand pressure, so you can absorb the gusts way easier. They also have a deep profile in the front, which makes them very controllable. Together with the high aspect ratio, that keeps the nose from rising easily.

Trimming a normal windsurf sail for the foil

The good news: you can trim any windsurf sail to be a bit more forgiving and faster for foiling.

• Go smaller. The most important thing is to use a smaller sail than you normally would. You get the most control when you barely have enough wind to get going and up on the foil.
• Less downhaul. Put on less downhaul than your sail manufacturer suggests. My sail has minimum and maximum marks: set the downhaul to the minimum mark, or even a bit below.
• Outhaul rather tight. As a rule of thumb, on a fin you want the sail to touch the boom when pressure comes into the sail. When foiling, you don't want it to touch the boom.

That combination creates a nice deep profile in the front of the sail while reducing the back-hand pressure, and that makes it really good for foiling. That's exactly what a foil sail gives you by design. On a fin, the same combination is one of the most common mistakes I see, more on that in 3 Trimming Mistakes (Almost) Every Windsurfer Makes.

Longer harness lines

Keep your harness lines long, longer than you would normally use them. That gives you a bit more range of motion and a more secure feel. It also encourages the right technique: hips low, so you can put tension on the harness lines.

Of course, long is a bit relative. It depends on your arm length, your boom width and your level. I personally run my harness lines around six inches (about 15 cm) longer than on a fin. More on line length in general in Long Harness Lines: The Easiest Upgrade in Windsurfing.

2. The board: footstraps and mast base

On the board there are three places where you transfer the pressure from the sail to the board, and ultimately into the foil: the back foot, the front foot and the mast base.

Start with the footstraps and the mast base in the middle position, so you can get the foil tuned right first. More about the foil in a moment. Once the foil is set, these are the tweaks to consider.

Footstrap position on a foil board

What most of us World Cup riders do to gain control is set the footstraps further apart. For you, that could mean putting the back strap one plug further back and the front strap one plug further forward.

How that works is pretty self-explanatory. Imagine standing on your board in no wind with your feet quite far apart. Now imagine putting your feet all the way together. Which way do you think you'd stay on the board longer?

How far outside the straps should be mounted really comes down to your level:

• New to the foil? You want to be as centred over the board as possible, so mount your straps further inside.
• Getting comfortable? Once you notice you're already placing your feet further outside, start moving the straps further out.

With your feet further outside you create more leverage on the foil and go faster, but it also gets a little more wiggly.

Windfoil mast base position

The mast base is another great tool to get the trim of your board in the air right. Start in the middle. If you need the nose higher after setting up your foil, bring the mast base closer to your feet. If the board still tries to rise too much, move it slightly to the front.

3. The foil: rear wing and mast rake

Last, and probably most important: the foil. It consists of the mast, the fuselage, the front wing, the rear wing or stabiliser, and hopefully a set of bolts.

The foil works almost like an airplane underwater. The asymmetrical profile of the front wing creates a pressure that pushes the foil up. The stabiliser extends far behind it, and the further back it sits, the more stable your pitch will be.

Setting up the rear wing (stabiliser) with shims

One important adjustment is the angle of attack of your stabiliser. The angle of attack is the angle between where the wing's nose points and the direction you're travelling. As a rule of thumb: the more you bring the trailing edge of the stabiliser up, the more your foil wants to climb to the surface of the water.

You need an angle that matches your footstrap, foil and mast base position. The easiest way to start is with the suggestions of the foil manufacturer. If your setup is a mix of brands, you might have to do the fine-tuning yourself.

Go on the water and focus on how the pressure is distributed between your legs:

• A lot of pressure on the back leg just to get the board out of the water? You're most likely missing angle of attack in the stabiliser. Increase it slightly, step by step, with the shims that come with your foil, until you have the right weight distribution between your legs.
• Up in the air, the pressure should be distributed evenly, with slightly more through the back leg.
• You can hardly put any pressure on the back leg without the foil wanting to send you to the sky? Then you probably have a bit too much angle of attack. It feels like your front leg gets pushed towards your body, when you should actually be able to stretch both legs quite a bit. Reduce the angle step by step.

Foil mast rake: keep the board level

Another important factor is the rake of your foil mast compared to the board. Whether you can change it depends on the box system you use for the foil connection. For a Double US box or a Deep Tuttle box there are washers, or shims, that change the rake of your foil mast. I've linked the shims in the video description. Most of the time you won't need to reduce the rake, but increase it.

The rake affects the pitch of your board. On a well-shaped board, for your board to glide smoothly and avoid hard nose dives, you want the part between the straps and the mast base to be parallel with the water.

So if your nose points down too much, increase the rake, meaning the angle between the board and the mast. Again, step by step: place the washers or shims between the mast and the board until the board is parallel with the sea.

With all these tips you'll hopefully be foiling super steady. I know it's a lot to consider, but it pays off. Hydrofoiling is a bit like driving an electric car: you don't get the hard splashes from the water anymore, but this feeling of efficiency is just a lot of fun, and you'll get a lot more quality days on the water.

Below is the whole setup in four steps, plus a checklist to save on your phone for the beach. The full video is at the end of this guide.