Those red and green bits - are what causes a hydrofoil to whistle!

Are you riding a foil that likes to hum? Perhaps it whistles? More of a Buzz? This phenomenon is common to a lot of foils, whether it's windsurf foils, kite foils, SUP foils or those used by boats.

Good news! There is a way to fix it, and all it takes is a piece of sandpaper. Yep, 60c at the hardware store and that annoying noise will disappear. Here's how to do it, and a basic rundown of what causes it.

What causes a hydrofoil to hum? Without getting into a the nitty gritty Hydrodynamics of it all, humming in foils is all about the tiny vortexes left behind as your foil passes through the water. Imperfections in the trailing edge (of both production hydrofoils and home-made ones) create a resonance through the mast, which is the noise you can hear. Listen closely, and the frequency of the noise will change as you speed up and slow down. Getting rid of the noise, is as simple as changing the shape of the trailing edge, to alter the frequency.

Stop foils from Buzzing

-Take your piece of sandpaper and wrap it around a sanding block. -Sand a 30 degree bevel into each side of (the trailing edge) of your foil mast. -Test it out! Still humming? Continue: -Sand a 30 degree bevel into the top and bottom of the trailing edge on your main wing. -Test it out! Still humming? Continue: -Sand a 30 degree bevel into the top and bottom of the trailing edge on your stabilizer. -Test it out! Hopefully, this will have fixed the problem.

Watch the video below to see the fix.