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Old Dec 03, 2012, 12:13 PM
xlcrlee is offline
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Zurich
Joined Apr 2006
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Interesting, but that's not exactly what I meant. The Acrobird's wings are cambered only because I wanted it to fly slowly. Similarly, my F-22's wings have conical camber, esp. because I needed to deal with low Rn [20 cm span] with 18g wt., so the wings are shaped basically in a smoothly curved version of the F-22 landing configuration, approximating the curvature of L.E. and T.E. flaps.



Micro Fighter /StarScream RTF R/C F-22 ORIGINAL version (0 min 42 sec)



Indoor Aircraft Carrier Landing (0 min 5 sec)




The gulls have far less camber and curve their wings spanwise [anhedral] for different reasons, incl. automatically turning into a slope wind and destabilizing for rapid maneuverability when landing [mucho more anhedral] .... and it's a very effective way to kill off lift and lose altitude fast for landing. Further, when outstretched the anhedralled wing ends are like downturned tips on a Horten. That is because, even though the gull has a tail, it is basically retracted in this mode, and the rear-swept wingtips are now the horizontal stabilizers. Because the airflow is reversed [up/down] there, as in the T-tails of 727s, etc., horizontal tail anhedral actually provides positive stability. Especially re: spiral stability. Same with an inverted V-tail: MUCH more stable in turns & gusts [I had a long flight in a V-tailed Bonanza and did not like the Dutch-roll action!]. Free flight models often have this feature, even if it's in the form of putting the vertical stabilizer on the bottom.


What I found has to do with the use of tip-vortices, which of course vary from one wing shape and camber [or camber mean-line: http://en.wikipedia.org/wiki/NACA_airfoil] to another.


When the B-2 was first displayed in public, my neighbor in Seattle didn't believe it could fly, so I traced the planform from the nearly top-view newspaper photo and quickly made a paper model. I cambered the wing -- for Rn purposes! -- and twisted in washout and downturned the T.E. at the root center [deltas work better that way, easily demonstrated with Rogallo and other hanggliders].

The quick & dirty B-2 paper model was twisted something like the hangglider in the photo below, plus the downturned center rear .... which you will note in later photos of B-2's in flight that the center T.E. sections are often also depressed.

This small model flew very stably without a hangglider-like pilot-weight hanging under for [esp.fore-aft: pitch] pendulum stability. And without reflexed T.E. or elevons. And without opened drag rudders [Horten / on B-2 only closed for stealth mode].


Lee
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Last edited by xlcrlee; Dec 27, 2012 at 05:15 PM. Reason: link typo
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