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Faro
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Downward-Curved Wings

Fri Oct 07, 2011 7:30 am

Given a downward-curved wing, shaped like the upper section of a circle with a high mid-span curving down to low wing root and low tip, would this appreciably reduce induced drag resulting from leeward vortex mixing of air (from upper and lower wing surfaces) some distance from the aircraft? The premise is that you are ‘flexing’ the shape of the wing’s pressure trails in the opposite direction to that of the leeward vortex.

If yes, could such a wing shape be implemented with CFRP’s without too much weight penalty? What other drawbacks would it have?

Faro

[Edited 2011-10-07 00:40:08]
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tdscanuck
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RE: Downward-Curved Wings

Fri Oct 07, 2011 1:53 pm

Quoting faro (Thread starter):
Given a downward-curved wing, shaped like the upper section of a circle with a high mid-span curving down to low wing root and low tip, would this appreciably reduce induced drag

Not really. It would still have about the same Treftz plane pattern so, all other things being equal, it should have the same induced drag.

Quoting faro (Thread starter):
The premise is that you are ‘flexing’ the shape of the wing’s pressure trails in the opposite direction to that of the leeward vortex.

Without a CFD run I can't exactly picture how the flows would work out, but the major factor in determining induced drag is how far you stretch out the trailing vorticity...in this case, you have the same aspect ratio so the only difference in distance from the vortex sources and lift production is the thickness of the wing. That's not going to make much a of a difference, I think.

Quoting faro (Thread starter):
If yes, could such a wing shape be implemented with CFRP’s without too much weight penalty? What other drawbacks would it have?

You could certainly do it in CFRP and probably get something like comparable weight, but you'd have an absolutely attrocious ground clearance problem. Whatever you gained in efficiency would be more than lost in landing gear weight.

Tom.
 
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tb727
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RE: Downward-Curved Wings

Sun Oct 09, 2011 7:57 pm

It probably wouldn't be very stable either.
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luckyone
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RE: Downward-Curved Wings

Mon Oct 10, 2011 3:06 am

Quoting faro (Thread starter):
If yes, could such a wing shape be implemented with CFRP’s without too much weight penalty? What other drawbacks would it have?

If what I'm picturing based on your description is correct, wouldn't it have rather tall landing gear? I'm envisioning the Tu-114, plus some!
 
330guy
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RE: Downward-Curved Wings

Mon Oct 10, 2011 3:45 pm

Didnt Concorde have downward curved wings??

[Edited 2011-10-10 08:45:54]
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tdscanuck
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RE: Downward-Curved Wings

Mon Oct 10, 2011 6:35 pm

Quoting 330guy (Reply 4):
Didnt Concorde have downward curved wings??

Yes, although it was most pronounced just along the leading edge. And reallllly long landing gear.

Tom.
 
2H4
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RE: Downward-Curved Wings

Mon Oct 10, 2011 8:32 pm

Quoting tdscanuck (Reply 1):
You could certainly do it in CFRP and probably get something like comparable weight, but you'd have an absolutely attrocious ground clearance problem. Whatever you gained in efficiency would be more than lost in landing gear weight.

Unless one could adapt this Rutan gear design:


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