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 Downward-Curved Wings
 faro From Egypt, joined Aug 2007, 1757 posts, RR: 0Posted Fri Oct 7 2011 00:30:30 UTC (4 years 7 months 4 weeks 5 hours ago) and read 4269 times:

 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]
 The chalice not my son
 tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 78 Reply 1, posted Fri Oct 7 2011 06:53:53 UTC (4 years 7 months 3 weeks 6 days 22 hours ago) and read 4160 times:

 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.

 tb727 From United States of America, joined Jun 2005, 2064 posts, RR: 12 Reply 2, posted Sun Oct 9 2011 12:57:27 UTC (4 years 7 months 3 weeks 4 days 16 hours ago) and read 3682 times:

 It probably wouldn't be very stable either.
 Too lazy to work, too scared to steal!
 luckyone From United States of America, joined Aug 2008, 2778 posts, RR: 0 Reply 3, posted Sun Oct 9 2011 20:06:33 UTC (4 years 7 months 3 weeks 4 days 9 hours ago) and read 3557 times:

 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 From , joined Dec 1969, posts, RR: Reply 4, posted Mon Oct 10 2011 08:45:39 UTC (4 years 7 months 3 weeks 3 days 20 hours ago) and read 3431 times:

 Didnt Concorde have downward curved wings??[Edited 2011-10-10 08:45:54]
 tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 78 Reply 5, posted Mon Oct 10 2011 11:35:50 UTC (4 years 7 months 3 weeks 3 days 17 hours ago) and read 3378 times:

 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 From United States of America, joined Oct 2004, 8957 posts, RR: 56 Reply 6, posted Mon Oct 10 2011 13:32:07 UTC (4 years 7 months 3 weeks 3 days 15 hours ago) and read 3320 times:

 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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