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Windfoiling Jericho

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by grantmac » Tue May 14, 2019 10:23 pm

You can oversimplify the airfoil shape by saying it acts like a loose leech it doesn't really work that way.

Rather they took an airfoil developed specifically for foiling (looks like one used for the AC72 cats) which has a very stable center of lift. The original H2 has more lift per cm2 but the undercambered shape is notorious for changing center of lift with speed. This is that building of front foot pressure and eventual instability as speed increases.

Washout just softens the stall and reduces the chance of tip stalling which should help lock it in during carves/gybes.
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by morrison » Wed May 15, 2019 7:18 am

Airfoil?

"A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to the fluid flow). If the fluid is a gas, the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil."
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by grantmac » Wed May 15, 2019 9:43 am

My background is aeronautical, old habits die hard.

Also from a physics standpoint air and water aren't very different depending on the speeds, which gets us into Reynold's numbers etc.

Most foil profiles are based on one of the NACA series.
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by morrison » Wed May 15, 2019 1:14 pm

grantmac wrote:My background is aeronautical, old habits die hard.

Also from a physics standpoint air and water aren't very different depending on the speeds, which gets us into Reynold's numbers etc.

Most foil profiles are based on one of the NACA series.


Yes, agreed. I was just trying to be humorous. My aeronautical background was limited to leasure.
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by grantmac » Wed May 15, 2019 1:21 pm

Leasure here too, although a long time since I did ant soaring.

But I built a few RC sailplanes including tailless designs, which use a reflex airfoil for exactly the same reason that Slingshot does.

Hydrofoils experience a very wide range of Reynold's numbers while being basically a weight-shift craft. A combination that demands a lot of stability.
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by morrison » Wed May 15, 2019 1:34 pm

"Hydrofoils experience a very wide range of Reynold's numbers while being basically a weight-shift craft. A combination that demands a lot of stability."
CofG above center of lift. Like trying to fly a Hang Glider from on top the wing.
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