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Re: Chaoyangopteridae

----- Original Message ----- From: "Unwin, Dr D.M." <dmu1@leicester.ac.uk>
To: <dinosaur@usc.edu>
Sent: Sunday, June 01, 2008 5:26 PM
Subject: Chaoyangopteridae

PS. Well, I still think that azhdarchids are dip-feeders and as for 250 kg...what kind of take-off speed would that require? A big cliff and strong nerves? Still, that might explain Dave Martill's azhdarchoid with the telescoped beak...

Depends upon the wing area. From memory, I believe that Darren and Mark are proposing a wing area somewhere about 1.3 square meters less than the wing area of my Piper Cherokee (a 4 passenger airplane that has a gross weight of one tonne). That's a BIG wing. If you make that assumption about wing area, the takeoff speed is about 30 to 36 miles/hour (48 to 58 Km/hour), and the average launch acceleration is roughly about 2.8 to 4 g's, depending upon some of the other assumptions you make. The launch takes about 0.4 to 0.6 seconds and about 3.4 meters in horizontal distance. I don't buy into that weight as an average weight nor that large a wing area, but it would not be impossible to launch at that weight IF the wing is big enough. An animal that met their geometric assumptions could get off the ground from a flat surface in its own length without the aid of wind and probably without overloading structurally. I do not know if it would have sufficient muscle mass to generate the accelerations required, but if it did, the skeleton could withstand them.

If you assume the wing is narrow inboard to the elbow before widening out to a hindlimb attachment, the speeds go up by about 40%, and the accelerations increase substantially unless you also reduce the weight commensurately.

I think Mike Habib prefers a somewhat lighter weight (about 80%) with about 3/4 as much wing area (in other words, the same wing loading). His scenario can get off the the ground without overloading.

I prefer a much lighter average weight with about half the wing area, but a larger propatagium which unloads the wing substantially. I explicitly state that I expect weights to vary by as much as 50% during the course of a long flight. That implies that I accept individuals that weigh as much as 225 Kg when on the heavy end of their weight range, and as little as about 120 Kg when on the light end. The difference between my estimate and Mike's/Mark's/Darren's estimates is within the ambiguity of the methods I use. My methods are structured to give an average weight. I believe that both Darren's/Mark's and Mike's estimation techniques are structured to give maximum weights. (Guys, correct me if I'm wrong....)