[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Quetzalcoatlus could not jump into the air



Thanks for the hang glider data Erik.  Good point about launch as well.  One 
additional issue for large pterosaurs is that they'd have a hard time getting 
the wings into an appropriate angle of attack while rearing bipedally.  That 
would complicate a gust-only takeoff.

Cheers,

--Mike H

Sent from my Cybernetic Symbiote

On Nov 9, 2012, at 5:51 AM, Erik Boehm <erikboehm07@yahoo.com> wrote:

>> 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?"
>>