Windsurfing Stall Speed and Windfoil Jibes

Words: Tez Plavenieks, Pics: James Jagger

When most riders initially get into windfoiling, it’s because they want to fly in light winds and cruise along using as small a sail as possible.

The hydrofoil industry has reacted to this trend with new equipment that more easily facilitates this: bigger foil wings that boast earlier lifting properties. These foils are super easy to learn with and progress on.

These bigger wings also give you early takeoffs, smooth glides, and an easier time completing the elusive foiling jibe due to a lower stall speed.

Just as with regular carve jibes in windsurfing, foiling jibes takes a lot of skill to master. Whilst there’s plenty of tutorials available for the actual technique insights, a massive factor to nailing the move is stall speed.

What is “Stall Speed” on a Hydrofoil?

In windfoiling, “stall speed” refers to the minimum speed at which the foil starts to sink due to lack of speed/water movement over the wings. The foil “stalls out” and drops, similar to the stalling of an airplane.

While stall speed is something you’ll have to deal with when learning to foil, it becomes even more important when you’re learning to jibe.

Having (myself) tested in excess of 70 different windfoil set ups – including low, mid, and high aspect foil wings – the sentiment: ‘slowly, slowly’ rings true. Of course, if you’re a high aspect (usually also means low surface area) foil rider then you can certainly learn to foil jibe. Chances are, however, it’ll take you longer.

How Does a Wing Impact Stall Speed?

There are two design components of the wing that affect the stall speed. (Note: these are general guidelines, hydrodynamics of wings are a very complex subject that I don’t claim to be a master of!)

The first is the surface area. The surface area is the total area of the wing when looking at it from above, and this is usually measured in cm2.

A larger surface area means the foil will be slower but have more lift and low speeds, thus it can maintain a lower speed before it stalls out. I would define a large surface area as ~1200+ cm2.

The other component is the aspect ratio of a wing. The aspect ratio refers to the ratio of the width of the wing to the height of the wing (from the tip of the nose to the back).

A low aspect ratio has a lower stall speed, whereas a high aspect ratio will stall out sooner. I would define a low aspect ratio as being less than 4 and a high aspect ratio as being over 5.

See the below diagram from Slingshot depicting these features.

A Lower Stall Speed Means Easier Jibes

To nail the jibe you need to slow everything right down so you almost hover on the spot.

Having a super low stall speed means the chances of making the move is upped considerably. Crashes usually occur during foot changes. If you’re using a smaller front wing, you’ll have to move much faster than with a large wing to avoid stalling.

In the video below, Wyatt Miller of Slingshot takes you through the different steps of the gybe, and gives his best piece of advice: “Slow everything down!”

Right about now you might be thinking all this talk of ‘slow’ equates to boring, which isn’t the case at all. Slow is smooth, and smooth is fast on the water!

Wing Size and Water Speed

The other thing to consider is larger windfoil wings that do allow for lower stall speeds can usually be coupled with much smaller sails – more so than with foils that are quicker and therefore require more power to lift.

But the beautiful thing about foils is they let you get going much faster than you would if you were dealing with the friction of the water across all of your board. You can generate decent speed vs the actual wind strength.

My biggest foil wing is “slow”, but I regularly clock 18-20knts in 10-12knts of true wind on a 5.3m. With this big, slow wing it gives me much more time and stability to complete a jibe while remaining in the air.

Another ‘thing’ recreational foilers lean towards is being on gear that’s nimble and maneuverable. Having gone through the learning phase and progressed to competently controlling and sustaining ride height, the logical next step is turning around (also known as foiling gybes/jibes).