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PatriciaJB
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Posted: Wed Jul 9th, 2008 12:16 am |
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Here's an interesting [ and readable !] paper.
Sailing the skies: the improbable aeronautical success of the pterosaurs
Matthew T. Wilkinson
Department of Zoology, University of Cambridge,
http://jeb.biologists.org/cgi/content/full/210/10/1663
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MiloA
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Posted: Thu Jul 10th, 2008 05:26 am |
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dear Patricia,
I like the investigation but consider those propatagium, more as a 'soft' leading-edge, (part of the entire variable airfoil, to adjust for the different flight-fases), more than a leading-edge-flap, by itself
for structural reasons, a tendon is needed, anyway, from the body out to almost the wingtip,
(similar to a bat-wing)
felicidades miloLast edited on Sun Aug 10th, 2008 10:55 pm by MiloA
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DDavis
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Posted: Wed Oct 15th, 2008 04:01 pm |
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Here we go again... recent reports in New Scientist trying to claim pterosaurs couldn't have flown. I've seen this time and time again... but of course they did or their wings would have been a massive incumberance and doomed them to a very early extinction. In fact, they could not have even started. The way this latest article explains it sounds like these guys don't have a clue how flapping wings can work, I mean... just a thrashing against the air and no real science involved. As I have noted before, and also Jon... the bigger the bird the slower its flapping needs to be and I seriously expect we'll find the larger pterosaurs flapped them in an extremely relaxed way. Like... about the frequency of a rower on a sunday picnic.
For that matter there were several species (don't have the names in front of me just now) that had the most extraordinary head crests that made pteranodon look bald... and this tells me that they had such good flight ability that they could afford what aught to be a massive incumberance simply to give them a decorative advantage in courtship.
As some of you might have noted, I am not always impressed with the accademic mind... sometimes they just have their formulas and don't really understand the way things work at all. It wasn't many years ago that New Scientist ran a discussion amongst its readers on just how wings work. Plenty of new thinking was presented, but it did not appear that any engineers were consulted. Never mind the fact that modern aircraft performance can be expected to be predicted with high accuracy even before the first flight...
Pterosaurs again... I note that when these are mentioned it seems always they are referring to Quetzalcoatlus Northroppi... as if these were the only ones known. And the weight just keeps going up. A few years ago nobody was talking about 250 kilos, but now this is tossed around like a well-established fact. No mention of the fact their skeletons were extraordinay studies in lightweight construction... with many of the major load carrying components having the density of polystyrene. I can believe there was a fair weight involved, but it was all packed into muscle tissue and that alone should be an indication of their ability to fly.
By the way, I am a regular reader of New Scientist, but rarely find the technical information I crave. It is more newsy than informative, and anything that smacks of mechanical gets skimmed over like it is expected the average scientist could not fix their own lawn mower.
Most Pterosaurs were very much smaller than Quetzie... and it is a fair bet that the little crow-sized species flitted around with all the agility of the best of small birds.
Nature worked it out long ago... and we are as yet the beginners.
David.
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MiloA
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Posted: Thu Oct 16th, 2008 07:40 pm |
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dear David,
i guess that pterosaurs survived in places with beneficial air-currents, depending a lot on local up-draft conditions,
and that their crucial cartilage-structures may have been poorly understood, still,
as i strongly believe, that those reptiles weight was not that important, as they managed a perfectly adjusted wing-shape, always morphing into precise corresponding configurations, every single instant, quite similar to what bats achieve actually
felicidades milo
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DDavis
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Posted: Sun Mar 22nd, 2009 01:30 am |
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Recently there have been discoveries of fossils that indicate pterosaurs had the same breathing system as do birds, providing the same advantages of lightweight bones and a high oxygen efficiency.
I read also of suggestions they may have used air filled sacks to fill out their airfoils. This raises the possibility such a system could be used in the wings of ultra-light aircraft... and perhaps ornithopters.
I imagine this would be difficult to put into practice... but perhaps well worth a good look at.
David.
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D.Bernardin
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Posted: Thu Oct 8th, 2009 09:35 pm |
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DDavis wrote: Recently there have been discoveries of fossils that indicate pterosaurs had the same breathing system as do birds, providing the same advantages of lightweight bones and a high oxygen efficiency.
I read also of suggestions they may have used air filled sacks to fill out their airfoils.
Recently I had the idea that huge pterosaurs had a good idea : use the multi-articulated fingers of their little brothers, to grow, and grow, and grow ... still flying in a good manner !
Paleontologists do not give us any certainty that fingers could move substancially . But we have to suppose, from the point of view of flight mechanics, that, at less they could bend their wings, so they had a good set of tendons to do it . Even if there is no archeological evidence ! The same as the trailing edge tendon : finally they found it ! That was necessary because they did glide ! Then without imagine that they had 4 sets of tendons at each finger (!) we can be quite sure that ligaments allowed a passive movement up and down : so they solved (or not) a big problem of the flapping flight of great creatures (and machines), the wind-mill movement . Without any certitude about the use of apparent mass to obtain a higher span efficiency when flapping, at less avoid a contrary flow from mid-wing to body ! So I imagine the multi-articulated wing making a wave movement while it moves (flapping). Is it yet possible ? Someone has minded about this problem ?
On the other hand as well as the selective pressure would have eliminated beings with huge wings who could'nt fly, creatures having to capture their preys heaving and pitching deeply would not have let any bone for our curiosity ! Perdon they could have been carrion-eaters .
Last edited on Thu Oct 8th, 2009 10:09 pm by D.Bernardin
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