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Re: Disney's Dinosaur Trailer



Oops, I forgot to copy this to the list.

James R. Cunningham wrote:

> Raymond Ancog wrote:
>
> > >soaring, banking, etc, to gain hieght than flapping to gain height-it
> > >saves a LOT more energy. >Betty
> >
> >  Which leads me to ask this question: is the projected weight
> > of _Quetzalcoatlus_ light enough to allow it to soar using thermals? >Ray
>
> Ray, I assume you're talking about Qn rather than Qsp.  Qn weight appears to
> have been on the order of 330-350 pounds (Greg Paul has projected about 440
> pounds, but I think that a bit heavy, though Qn could have lifted that
> weight), and wing area was on the order of 78-80 square feet, so wing loading
> was a little over 4 psf.  This is squarely in the normal range of wing
> loadings for the lighter sailplanes, and Qn's min sink was about 125 fpm,
> which is also in the normal range for soaring in today's atmosphere.  There is
> some very iffy evidence for a slightly increased density during the late
> Cretaceous, which (if true) taken together with the convective activity caused
> by the higher temperatures, would have made soaring more cost effective then
> and at slightly slower velocities than now.  However, Qn could have flown
> quite handily in today's atmosphere, launching about 9:30 or 10:00 am and
> flying till late afternoon.  Qn's low sink rate would have allowed it to make
> use of a phenomena called 'microlift' which Gary Osoba has described and  used
> extensively in the last few years to set several world records in ultralight
> sailcraft.  I have some really neat wingtip video of Gary using 'cloud
> streets' and microlift to make a cross-country in his Woodstock, a sailplane
> with similar size, weight, and performance to Qn.
>
> At his best L/D of about 30:1, Qn had to extract a little over 1 horspower
> from thermal or dynamic lift sources to enable soaring.  His L/D (glide ratio)
> was quite sensitive to the position of his leg/tail/uropatagium structure, and
> he could  vary his glide ratio from about 30:1 down to about 10:1 by just
> adjusting the position of his legs (for visual reference, a pigeon's glide
> ratio is about 6:1 and archie's was about 4:1).  At 30:1, soaring is quite
> feasible, and possible throughout most of the average day.  At a glide slope
> of 10:1, four horsepower was required to stay in the air, and soaring would
> have been restricted to those days when atmospheric lift was averaging 400-500
> fpm.  Which is, of course, impractical and means that Qn didn't carry his legs
> in the 10:1 position except when he wanted to  descend or make some transient
> maneuver.
>
> Qn had enough muscle power to use flapping to sustain level flight and even
> climb at a respectable rate for short periods when in the 30:1 position, but
> did not when in the 10:1 position.
>
> An interesting aside is that, although changing the weight of an animal
> affects his sink rate, it does not affect the glide ratio or the range that he
> can achieve when gliding down from a given altitude.  This is why competition
> sailplanes carry water ballast when racing.  The additional sink rate caused
> by the extra weight, when applied to the unchanged glide ratio, gives them
> extra speed.  So Qn would have temporarily flown faster after feeding than
> before.
>
> All the best,
>
> Jim