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 Post subject: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:04 pm 
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Location: Slovenia
Hi,
I am guessing, that a compleatly flat front wing should have a bigger surface arrea compared to a profiled front wing to produce the same lift. The lift on a flat plate comes from the angle of attack (AOA), while an assimetrically profiled wing produces lift also at a zero AOA. Am I compleatlly wrong here?
Greetings,
Jaros


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 Post subject: Re: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:31 pm 
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Joined: Fri Jul 16, 2010 6:27 am
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Location: Ford Lake, Michigan


I don't understand the question but maybe this video from 1930 will help.


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 Post subject: Re: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:42 pm 
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Location: Slovenia
Quote:

I don't understand the question


I am not very good in explaining thinks in English, but I will try to be clearer...
All commercially available kite Hydrofoils have profiled wings (eppler, naca,...). For exmple - if you would change the stock front wing with the wing made of flat carbon plate - exactly the same outline and the same anhedreal as the stock wing- will it have less lift? Should you make this wing with bigger surface arrea to be able to ride it at the same speed as the stock profiled wing?
Greetings,
Jaros


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 Post subject: Re: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:43 pm 
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watch the video I posted. I think it explains exactly what you are looking for.


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 Post subject: Re: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:47 pm 
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You are absolutely correct Jaros, a good thought :thumb:

The AOA is not important here (well, only if you are building of course), but the fact that a flat plate has a max lift coefficient just below 0,6 whereas a "curved" plate, or a cambered thicker profile typically has max lift around 1,0 to 1,3.

Because of the low AR a foil has, the high lifting foil will "lose" lift (tip vortices and loss at the tips), so the lift is not fully twice as high, but definitely way higher than a flat plate :D

If it was a glider wing (high aspect), the curved plate or profile would have slightly more than twice the lift of the flat plate :naughty:

So yes, if using a flat plate (which will work fine), you need more surface area to get the same lift, although not quite twice the size.

8) Peter


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 Post subject: Re: flat wing vs. profiled wing surface arrea
PostPosted: Tue May 13, 2014 9:51 pm 
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Location: rhode island
most likely more area.
AOA higher than zero is a definite.

.....either that or go faster


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