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Re: pteros have lift-off
David Peters wrote:
All I want now is minimum flight speed and apogee as a multiple of the
unit specified by CG height at the beginning of the leap. Been gone
all day. No reply, so far, to those queries.
Been a busy day for me, too, so I was unable to address those questions
until now. Minimum flight speed varies according to planform and body
weight, of course. What sort of aspect ratio do you assign to
Istiodactylus? Do you have a preferred body weight? I have estimates
of both that I use, but I'm more than willing to crunch the numbers for
your version. Will only take a few minutes.
The apogee is determined according to simple ballistic equations. In
actuality, because the inboard wing provides some lift even before the
wing finger is extended, the trajectory is "better" than ballistic, but
a ballistic path is quick and conservative. Therefore, it depends on
the power fraction estimates and limb lengths - it is not a simple
multiple of CG.
One last thing to note is that the long wing finger on things like
Istiodactylus and Ornithocheirids has little impact on their minimum
launch height, because the wing finger isn't unfolded until after the
wing is well into the upstroke (leap first, unfold second). The
changes in relative limb element lengths in azhdarchids improves launch
ability not because the wing finger is shorter, but because MCIV is
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181