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Hydrofin? Any insights on this?

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tmcfarla
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Re: Hydrofin? Any insights on this?

Postby tmcfarla » Fri Jun 21, 2019 1:17 pm

elguapo wrote:
Fri Jun 21, 2019 3:17 am
Oldman_Dave wrote:
Fri Jun 21, 2019 3:04 am
I'm fairly convinced that due to airfoil shape+ laws of physics there will never be a half decent bidirectional foil. That vid does nothing to change my mind.
well...
at least for the wing/most efficient shape part....NASA has already figured it out.

https://www.nasa.gov/directorates/space ... ying_Wing/



Image
This nasa wing is a supersonic wing, which operates very differently than a subsonic wing. Subsonic wings are reasonable models for hydrofoils, but supersonic wings are not.

BWD
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Re: Hydrofin? Any insights on this?

Postby BWD » Fri Jun 21, 2019 1:31 pm

Actually it’s been said many times, hydrofoils at 15+ knots are more similar to airplane wings operating near or above the speed of sound, than they are to airplane wings that operate at low speed.
Has to do with water density and viscosity being much greater than air.
Hydrofoils and fins in kiteboarding are usually scaled much thinner than low speed airfoils, and often have their max thickness shifted aft, like supersonic airfoils.

GTC
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Re: Hydrofin? Any insights on this?

Postby GTC » Fri Jun 21, 2019 1:44 pm

elguapo wrote:
Thu Jun 20, 2019 11:22 pm
Image
3 Hydrofoils for bi-direction

The board is setup with 3 Hydrofins™, at any one point you would be riding on 2 of the Hydrofins™, the middle one creating the primary lift with a rear one for stability and balance.

That's how it looks to me
Attachments
Captura de Pantalla 2019-06-21 a les 14.43.14.png

elguapo
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Re: Hydrofin? Any insights on this?

Postby elguapo » Fri Jun 21, 2019 4:59 pm

tmcfarla wrote:
Fri Jun 21, 2019 1:17 pm
elguapo wrote:
Fri Jun 21, 2019 3:17 am
Oldman_Dave wrote:
Fri Jun 21, 2019 3:04 am
I'm fairly convinced that due to airfoil shape+ laws of physics there will never be a half decent bidirectional foil. That vid does nothing to change my mind.
well...
at least for the wing/most efficient shape part....NASA has already figured it out.

https://www.nasa.gov/directorates/space ... ying_Wing/



Image
This nasa wing is a supersonic wing, which operates very differently than a subsonic wing. Subsonic wings are reasonable models for hydrofoils, but supersonic wings are not.

super/hyper sonic stuff is beyond my paygrade.
i'll take your word for it

(was just giving an example...that there ARE examples of bi-directional wings out there)

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Re: Hydrofin? Any insights on this?

Postby norcom » Fri Jun 21, 2019 10:13 pm

This reminds me of an idea I had of attaching my GoFoil Iwa wing just a few inches from the bottom of the surfboard. :lol: Sure, I know it wont work. I've used my Moses 12" mast and it's quite hard to ride once the chop gets above ankle high but still works in shallow water. But with a huge SUP wing a few inches under the surfboard? Perhaps it'll give me enough in lighter winds to get back upwind and still have fun on the waves. I love the 50cm masts with the big SUP wings on small waves. Now if I they could make the foil wings retractable on a surfboard, like a windsurfer dagger board, that'd be sweet. :lol:

The video looks like he's still edging with the board. Seems putting bigger fins on for better upwind or a retractable daggerboard like the Flyrace board would be more efficient than whatever that is. Props for the ingenuity though! Someone try my idea. :D

OzBungy
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Re: Hydrofin? Any insights on this?

Postby OzBungy » Sat Jun 22, 2019 6:55 am

For a foil to work everything that is not the foil has to be out of the water. If the non-foil bits have contact with the water then they create drag and you stop, or go really slowly. Even the mast creates drag, but you need that bit to keep the rest out of the water.

If you want to go fast on a TT in less wind, simply make the TT stiffer and wider and have no fins at all.


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