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Author Topic: Pterosaurs  (Read 885 times)
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JimC
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« Reply #30 on: November 17, 2014, 08:54 AM »

Thanks a bunch, Doug.  Sounds like our interests and backgrounds are somewhat similar - though I have never looked into kiting before.  A bit more is known about pterosaurs than is commonly recognized by those who don't actively work on them.  For example, some soft tissues are preserved well enough that we can actually see structure internal to the cells.  However, no pterosaur is preserved well enough that we have all of that animal available.  So we "cut and splice" relevant info from different individuals and different species as best we can.  Not an ideal arrangement, but such is life.

I actually became interested in pterosaurs serendipitously while attempting to think outside the box on some general aviation drag reduction mods I was designing.  The animals soon took over my life, but some of the observations did transfer from them to aircraft, so it was a two-way street of sorts.  I usually focus on the midsized Quetzalcoatlus species because it is one of the best preserved with a number of individuals.  No soft tissues though.  It's been fun partly because it has given me the opportunity to work with some of the world's most talented people in several different fields.  Makes me feel lucky.

Most pterosaurs fly with a negative static margin most of the time but obviously, not as negative as kites.

For whoever asked, no they are unlikely to stay aloft for as long as albatrosses, partly because of the difference in energy reserves and the need for additional energy in the atmosphere to compensate for the pterosaurs' usually higher wing loading and limited ability to flap continuously for long durations.  As an aside, there was more energy in the atmosphere back then due to the higher temperature. Also, there is no evidence yet to indicate that pterosaurs can sleep half their brains at a time like some birds do.  Homology would probably be the best way to address that question, but it is unlikely that there will ever be a definitive answer.  Though they could make use of thermal soaring, they did not depend on it, being adapted for extracting lift from other energy exchanges.  Microlift, lee shear soaring, etc.
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« Reply #31 on: November 17, 2014, 09:05 AM »

forgot the obligatory shots of kites that are related to this thread, all static single line kites that are superb flyers.

Joel Sholz Pteranadon:


Joel Scholz Dimorphodon:


George Peters Pterosaur:

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Doug S
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« Reply #32 on: November 17, 2014, 12:41 PM »

JimC,

Your project intrigues me, so I did a little internet research and found the following links regarding the Pterosaurs.  Very interesting, but the article opines the air was 2/3 the density of water during the time of the Pterosaurs.  Based on this assumption, the air would have been 523 times denser that it is today (at sea level).  The Pterosaurs would be more likely swimming in the air and not flying.  Is there still funding to build a flying version?  If so, how are you going to build your Pterosaurs to account for our present day air density?  523 times lighter?

http://www.dinosaurtheory.com/flight.html
http://www.dinosaurtheory.com/solution.html

Just my thoughts,

Doug
« Last Edit: November 17, 2014, 02:25 PM by Doug S » Logged

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JimC
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« Reply #33 on: November 17, 2014, 03:58 PM »

2/3 the density of water?
There's a lot of silly, ignorant trash on the Internet isn't there?
I've seen that website before.  It gave me a chuckle too.
:-)

Depending upon the time frame of interest,
CO2 levels were roughly 3 to 5 times greater than now
O2 was about 25 to 30%
Humidity was slightly higher on average
Sea level was up to 200 meters higher
Other atmospheric components were about the same as now

So, it's about a 5 minute job to calculate average sea level pressure back then and then back calculate density based on temperature.  All said and done, not all that much different from now.  I usually take the lazy way out and just use today's standard atmosphere as a base since there isn't enough difference to fret over, considering all the other variables.  All my friends who work on pterosaur flight mechanics do the same for the same reasons.  Like me, you can quickly calculate the average density and likely range if you are curious.

The last flying pterosaur replica that I built cost about US $557,000.  Paul's half scale QN cost about the same back in the mid 80's.  That sort of money comes along about once every 25 years or so.  If I were going to build another one, I would do a full scale Qsp (4.7 meter span).  I think I could do a decent one for about US $30,000.  I'm not interested in doing a Qn, though I do work on Qn (by the way, we refer to the animal as Qn and Paul's half scale replica as QN).
« Last Edit: November 17, 2014, 05:31 PM by JimC » Logged
Doug S
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« Reply #34 on: November 17, 2014, 04:40 PM »

JimC,

Thanks for the reply.  I also was very amused.  Air 2/3rds the density of water.  Now that's funny!

Doug
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« Reply #35 on: November 17, 2014, 05:25 PM »

I did have a typo in my previous post.  I said O2 was 25 to 30% greater.
It was 25 to 30% -- omit the word greater.  My fingers got carried away with enthusiasm and out ran my brain.
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JimC
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« Reply #36 on: November 17, 2014, 06:57 PM »

Doug, here's a top view of Quetzalcoatlus species (in neutral position, not flight position).
In front view, note the ventral bend (downward cupping) in the spar at about 45% of the semispan - it is important to gust response.  Also, pterosaurs can't support roach in the trailing edge.  Aspect ratio of this animal is about 16 to 16.5
span about 4.7 meters
Weight about 22 kg

Oops, I didn't include front view - will add later.
Second image is of pteranodon longiceps.  Notice the difference in proportions
« Last Edit: November 17, 2014, 07:11 PM by JimC » Logged
Doug S
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« Reply #37 on: November 18, 2014, 07:16 AM »

JimC,

From the drawings, it appears the outline of the wings and tail (lifting surfaces) are inferred.  Is there any documentation on what the actual shape (outline) of the wings and webbing around the feet/tail look like, specifically the tips and trailing edges?  You indicated the first drawing is the neutral position, but not the flight position.  Is there an opinion on what the wing and feet/tail configuration would look like in flight?

If I choose to build a scaled down version as a glider kite as a proof of concept, I would need these details.  I would prefer to build the initial glider kite version with a wing span in the 6 to 8 foot range to work out the details.  If you have information on specific Pterosaurs around that size, that would be great, otherwise, I would scale down one that you recommend or have the most detail.  I am currently building one of my Bird of Prey swept forward wing glider kites with a wing span of 8 feet, so I am comfortable with the materials for a glider kite of this size.

Doug
« Last Edit: November 18, 2014, 07:30 AM by Doug S » Logged

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JimC
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« Reply #38 on: November 18, 2014, 10:30 AM »

There are quite a few preserved membranes, some with exquisite detail.
If I were you, I would do a half scale Qsp (half scale wingspan 2.3 to 2.4 meters).
Pterosaurs are often illustrated with with too low an aspect ratio.  No preserved membrane in the fossil record has the wing trailing edge at the elbow located more than 45% of the length of the humerus behind the elbow. The trailing edge then turns abruptly aft to attach to the thigh just inboard of the knee. (some folks will argue with that attachment).
« Last Edit: November 18, 2014, 10:39 AM by JimC » Logged
Doug S
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« Reply #39 on: November 18, 2014, 12:33 PM »

JimC,

In a prior reply of yours, you indicated the first drawing is the neutral position, but not the flight position.  So if I decided to build a half scale of the Qsp as you suggested as a glider kite, I would need to know what would be considered the flight position.  Can you point me to a picture or website that would show this.  Thank you.

Doug
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JimC
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« Reply #40 on: November 18, 2014, 03:43 PM »

There aren't any.
For one thing, an individual can burn off up to 50% of his weight during a single flight, and his cg changes as he does so.  So flight configuration changes throughout the course of the flight.  For a kite, you'd just have to pick a specific condition and design for that.  Also, the hindlimbs/uropatagium are usually flown in upload configuration with the upload being slightly less than the weight of the hindlimbs.  This is done to unload the pelvic muscles.  It is aerodynamically quite unstable though.

John's quetz drawing would be close if you configured the long neck like geese or swans carry them in flight -- to spin off parallel, counter rotating vortices over the top of the neck and back.  Also, fly the torso at a slightly positive aoa (not as much as the swan in the photo below).

And the base of a pterosaur's neck exits the torso higher than it does on a bird (due to the way they align the two short vertebrae at the base of the neck)
« Last Edit: November 18, 2014, 03:53 PM by JimC » Logged
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