Question about coplanar wings

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yankeeclipper

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Jun 1, 2009
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With canards, tandems, DeLannes, etc. that have coplanar wings, does the foreward wing not complicate the stream for the rearward, at least more than just trivially? If the downward stream of the fore were to feed the underside of the aft (more so than the topside, anyway), would it not create a more turbulent stream for that wing? In the case of the Quickie, I see that Rutan juxtaposed the two wings with +/- dihedral. Perhaps to minimize the above? Or maybe just to offset the lower anhedral (required for landing gear).
 

Noah

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Nov 19, 2010
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California
Yes to all. Sometimes maybe it depends.

Look up deep stall. Multiplane wings generally have the rearward wing close and low to force high pressure air under the wing across the top of the flap or second wing, but this is essentially a longer wing and creates problems at high angles of attack.

If the wing is efficient at your speed and altitude, turbulence a good distance from the forward wing should be minimal. A short chord single plane flying wing with one leading edge and some sweep is the most efficient shape for lift.
 

wsimpso1

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Oct 18, 2003
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Saline Michigan
Search this forum on the word "downwash". Yeah, that is the term for the phenomenon that you describe.

Understand that the wing heavily influences air above and below the wing for atleast a full wingspan. And yes, in all designs with more than one plane, the flow off of the surfaces ahead have significant effect upon the angle of attack on the planes behind.

Billski
 
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