Re: Quetzalcoatlus could not jump into the air

[Erik Boehm <erikboehm07@yahoo.com>]

> I am a little out of touch with hang-glider masses, but
> don't they weigh something like 20-30 kg?

The weight range is variable, the single surface low aspect ratio ones are only 
about 20, the highest aspect ratio ones weigh about 55-60.
Then there's the harness, parachute, other equipment that will add another 
10kg... and I know of at least one pilot who flies one of the heavy, high 
aspect ratio ones, and he's over 200 lbs, so lets just say, at a minimum, the 
entire weight is 55+10+90= 155 -which is pretty close to the weights you are 
talking about.

And again.... speaking just from physics, the heavier weight would just require 
more wind - which is why I was specifically quoting "right conditions"
With the right conditions, you can make just about anything fly (as long as it 
has an aerodynamically stable configuration)

The basics of my argument are that it probably *could* launch the way the 
person asked, but if it was *limited* to *only* that type of launch, I can't 
see how it was a viable animal.
I can imagine some very small regions (places similar to popular ridge soaring 
areas) where a creature might be able to survive with only that launch 
capability - but when one considers erosion and changing weather patterns, I 
can't see such places with the right conditions lasting long enough for such 
animals to evolve, let alone last as long as they did.

--- On Fri, 11/9/12, Mark Witton <Mark.Witton@port.ac.uk> wrote:

> From: Mark Witton <Mark.Witton@port.ac.uk>
> Subject: Re: Quetzalcoatlus could not jump into the air
> To: "dinosaur@usc.edu" <dinosaur@usc.edu>
> Date: Friday, November 9, 2012, 1:55 AM
> "With Hang gliders (and I fly them,
> and in terms of wingspan and weight, they seem most similar
> in specifications to the animals we are talking about here),
> under the right conditions, you need only face into the
> wind, and raise your angle of attack to takeoff (or saunter
> two steps forward)."
> 
> I am a little out of touch with hang-glider masses, but
> don't they weigh something like 20-30 kg? I
s
> will fall well short of a likely mass for a giant
> azhdarchid, perhaps almost by half. Masses of over 200 kg
> are being argued as likely for these animals by a number of
> researchers for a long list of reasons. Hence, I'm not sure
> giant azhdarchids could readily employ hang glider takeoffs
> in the way you suggest. Also, note that giant azhdarchid
> anatomy is entirely consistent with active, powerful, and
> flapping flight. Soaring and gliding were probably employed
> at times, but there is no reason to think they were passive
> gliders.
> 
> You're observation that the longevity and widespread nature
> of the azhdarchid lineage argues against the need for
> pterosaur 'airports' is a fine one. Azhdarchids seem to be
> the longest lived lineage of all pterosaurs, and are found
> all over the world, presumably reflecting occurances in very
> different topographic and climatic settings. This may be
> why, under the quad launch model, they seem so darned
> effective at becoming airborne.
> 
> Mark
> 
> --
> 
> Dr. Mark Witton
> www.markwitton.com
> Lecturer
> Palaeobiology Research Group
> School of Earth and Environmental Sciences
> University of Portsmouth
> Burnaby Building
> Burnaby Road
> Portsmouth
> PO1 3QL
> 
> Tel: (44)2392 842418
> E-mail: Mark.Witton@port.ac.uk
> 
> If pterosaurs are your thing, be sure to pop by:
> 
> - Pterosaur.Net: www.pterosaur.net
> - The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
> - My pterosaur artwork: www.flickr.com/photos/markwitton 
> 
> 
> >>> Erik Boehm <erikboehm07@yahoo.com>
> 11/8/2012 9:31 PM >>>
> --- On Thu, 11/8/12, Mark Witton <Mark.Witton@port.ac.uk>
> wrote:
> 
> > From: Mark Witton <Mark.Witton@port.ac.uk>
> > Subject: Re: Quetzalcoatlus could not jump into the
> air
> > To: "dinosaur@usc.edu"
> <dinosaur@usc.edu>
> > Date: Thursday, November 8, 2012, 11:29 AM
> > "Dumb question:  This abstract
> > assumes a downstroke would have been
> > necessary for takeoff.  Is it possible that under
> the
> > right conditions
> > simply opening the wings
gotten the animal high enough for a full
> wingflap
> > without
> > much muscular effort?"
> > 
> > Probably not, assuming the animals weren't the 70kg,
> eating
> > disorder-ridden individuals that Chatterjee et al. make
> them
> > out to be.
> 
> 
> I'm going to have to disagree with this... they key words
> being "under the right conditions"
> With Hang gliders (and I fly them, and in terms of wingspan
> and weight, they seem most similar in specifications to the
> animals we are talking about here), under the right
> conditions, you need only face into the wind, and raise your
> angle of attack to takeoff (or saunter two steps forward).
> 
> The question in my mind is... were these "right conditions"
> prevalent enough to make this a workable lifestyle that
> spread across continents and prevailed for over a hundred
> million years.
> The lack of practicality is what prevents hanggliding from
> becoming more widespread - it is perhaps too hard to find
> places suitable to launch them  -granted pterosaurs had
> the advantage of the ability to flap for powered flight,
> presumably making them more than capable of level flight in
> still air - which would expand the launch-able conditions
> and geography.
> 
> So "under the right conditions" unpowered standing launches
> are clearly possible - but if this was the only method
> available to such a creature, that would mean that if they
> ever found themselves on ground with no spot in the vicinity
> that does not have a significant wind blowing up a
> significant slope (lets say no more than 30 degrees cross) -
> then they might as well be a beached whale, and I would not
> expect such a creature to survive more than a few
> generations, let alone millions of years across the globe.
> 
> Unless we take a more "radical" approach, and consider that
> these large creatures were more at home on the ground than
> in the air, but retained "hangglider-like" soaring
> capabilities - then if we assume the warmer climate was more
> conducive to thermal generation, then per
imply have been a long distance travel
> technique - 
> ie, you forage on the ground in some area for an amount of
> time, and when its time to find new foraging grounds, you
> climb to the top of the nearest elevation, wait for the
> right wind cycle, and launch, and then thermal and fly for
> perhaps hundreds of miles, and arrive at the next foraging
> area...
> 
> There are similar XC contests with para-gliders (which are
> more practical to hime with, and can land in smaller areas
> than HGs, but don't have the same glide performance as a
> hangglider) - where pilots will hike up to a mountain, then
> launch in the afternoon and often fly hundreds of
> kilometers, land, sleep, and repeat the next day.
> In the right places (such as the alps) in the right weather
> (ie at certain times of the year), a paraglider allows one
> to travel much farther and faster than on could on foot,
> without powered flight or powered launches at all.
> I still have my doubts that such a niche is viable.
> The question is not "is it possible to fly like that?"
> But rather "Is an organism that flies like that likely to
> reliably survive and reproduce?"
>