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"Foil Effect": A team Rista video on race dev't in Maui

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tautologies
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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby tautologies » Sun Mar 11, 2012 10:41 pm

You guys obviously have put more thought into this than me, but I have ridden fins that had more flex than the g-10 rista fins that comes on the naish board, and as far as I could see the length and shape of the fins were pretty much the same, but the flex different.

HUGE difference in ride....

The flexy fins was almost uncontrollable and the board was all over the place...took me a long time to be able to reasonably control the board....it was having what I would call temperamental issues..it would just jump out of the water and crash back in...that got increasingly worse as the speed increased. Once I got the g-10 on it was easy to control and perfectly easy to do what was hard before...

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby Gebi » Mon Mar 12, 2012 4:33 am

Yes too much flex in a race fin is a crazy and unpredictable ride. Rista fins are flexing only in the tips relative to the base. Gebi out.

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby discojuggernaut » Mon Mar 12, 2012 6:52 am

I know this is a bit of newb question, but would it be possible to create a hydrofoil shape that would work well on a raceboard? Maybe a board that can be designed to minimize whetted surface to be able to ride flat with minimal distrubance from chop?

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby tautologies » Mon Mar 12, 2012 9:59 am

discojuggernaut wrote:I know this is a bit of newb question, but would it be possible to create a hydrofoil shape that would work well on a raceboard? Maybe a board that can be designed to minimize whetted surface to be able to ride flat with minimal distrubance from chop?



You mean like this http://www.cheynehoran.com.au/starfin.html

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby ronnie » Mon Mar 12, 2012 12:18 pm

Paolo Rista seems to have a good plan on how to identify the things in a fin that work better. Its always been a bit of a black art and depended a lot on good rider feedback. Paolo is skilled enough to ride hard enough to get his own feedback, plus he has a group of top riders doing the same. Its a very difficult thing to get right.

Chip Wasson used to race a foil board in the series at San Francisco. It was fast upwind but struggled downwind and Chip now races a normal board. There are a lot of foil racers still in France, and on some types of course they seem competitive, and I think beat Julian Keurner in a race.

Up against a Moth, the kite raceboard is clearly faster.

http://www.mach2mothusa.com/2012/01/mot ... kiter.html

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby Jade » Mon Mar 12, 2012 5:36 pm

tautologies wrote:There are a lot of foil racers still in France, and on some types of course they seem competitive, and I think beat Julian Keurner in a race.


I raced in the French National Championship - http://www.tregorkiteparty.com/

The top 3 or 4 guys on foils stormed ahead on every race and stayed there till the finish, - they categorized as a separate class in the event. Yep your right, seriously tricky downwind.

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby tautologies » Tue Mar 13, 2012 4:15 am

well if you guys are talking about regular foil boards, I have one, and I can see the point in ultralight conditions. There is barely any drag from the surface, so going is fairly easy...going downwind is silly...going fast on the one I have is not easy. It is a low aspect foil, so it produces a lot of lift in low wind / speed, but becomes harder to control in higher wind. Either way. I like to ride the raceboard more in light wind. The foil is fun, but not a board a bring very often.

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby Rabidric » Wed Mar 28, 2012 11:48 am

davesails7 wrote:Is that a little too much of a "foil effect"?

On my board it seems like when I get too much out of the water and pushing hard on the fins, the fins airate or stall or something. I thought you wanted where the board meets the top of the fin to stay in the water at all times. Is this not an issue with larger fins like these? (I'm riding the stock fins on the 2011 Cabrinha 183 board)


Lift coefficient is a key aspect of ventilation. Get a large total fin area, and you need a lower Cl to create a given total load to match the kite. Lower Cl -> less ventilation(and a nice low AoA for good L/D) . length of fin helps too. Fin length and area needs to be surplus to requirements for "ideal running", so that you have enough of it left in those "dynamic periods" when you are out of sorts a bit.

Adding non-liftproductive extra wetted area like fences isn't typically worth the drag penalty.

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Re: "Foil Effect": A team Rista video on race dev't in Maui

Postby john-brasil » Thu Apr 05, 2012 11:47 pm

about the foil effect.
How about 3 foil fins (wingtip fins) under the board, would that work as well??

Would maybe be another option to get the board out of the water....


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