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Re: FYI -- Microraptor gui, Burnham and Alexander, PNAS...

 Tim Williams wrote:

Dan Chure <danchure@easilink.com> wrote:

Alexander, D.E., Gong, E., Martin, L.D., Burnham, D.A., and Falk, A.R. (2010). Model tests of gliding with different hindwing configurations in the four-winged dromaeosaurid _Microraptor gui_. PNAS published online before print January 25, 2010, doi:10.1073/ pnas.0911852107

... Although the hip joint requires the hindwing to have at least 20° of negative dihedral (anhedral), all configurations were quite stable gliders. ...

Gee, that's nice - but I note that not a single flying animal alive today, even unpowered ones, is particularly passively stable (most derived, powered flyers are extremely unstable, actually). Granted, some of the gliders are more stable than most powered flyers, but they still have motor control, meaning that being stable enough to fly effectively as a rigid structure is not of great importance. Unless Microraptor corpses were gliding after undergoing some serious rigor mortis... Seriously, though, if we use the criterion that the more stable planform is best, then many living gliders would be ruled "poor fits". As a result, the "build a static model and throw it" test would seem to fall on the weak side with regards to proof of concept. I'm not saying that it is not cool and fun, but it may not give the desired information, *unless* one is trying to incorporate aspects of biological planforms into a passively stable artificial glider model for engineering purposes.


--Mike H.