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How Hydrofoils Work

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Toby
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How Hydrofoils Work

Postby Toby » Tue Dec 29, 2020 2:09 am

In this video we explain how hydrofoils work. Believe it or not, most of the common explanations of how hydrofoils work are incorrect or incomplete at best. We'll take you through the misconceptions and share an intuitive, easy to understand explanation of where lift comes from. Enjoy!



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Re: How Hydrofoils Work

Postby revhed » Tue Dec 29, 2020 9:45 am

Nice vid,THX! :thumb:
BUT,
Also, :idea:

I lean this way for understanding. Could be a combination of all to some degree?
R H

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Peter_Frank
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Re: How Hydrofoils Work

Postby Peter_Frank » Tue Dec 29, 2020 11:12 am

Good videos.

Just one correction, she mentions hydrofoils use a lower angle of attack because of the water having higher density/viscosity.

It is wrong.

You can use a much smaller wing because of the higher density, compared to air, but the most efficient AOA is still the same, and the stall occur at the same AOA too, no difference.
(Reynolds numbers can have a small effect on boundary layer separation at low numbers, but not an issue here)

In fact, in real life a foil can be ridden at a higher AOA without stalling, compared to airplanes/gliders, because our foils have very low AR, meaning the tip vortices changes the AOA down so they stall at an even higher geometrical AOA :D

But when we ride in normal somewhat faster cruising speeds, the AOA is quite low, as we get so much additional lift with just a little bit more speed, that we can ride our hydrofoils at close to zero lift coefficients just a tad above, meaning extremely low AOA's, actually negative AOA's if cambered profile, this is true :thumb:

8) Peter


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