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Old Jun 29, 2015, 04:44 PM
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FastEddie123
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wanted UMX as3x - Pterodactyl

Who would not want a few of these to fly around the yard!! it's gotta be a real wing flapper ornithopter though , no props - don't even bother ...

maybe a Da Vinci flyer also -- eddie123
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Old Jun 29, 2015, 05:57 PM
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Eflite and losi should team up to make a Taylor Aerocar
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Old Today, 04:26 AM
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Quote:
Originally Posted by fasteddie123 View Post
Who would not want a few of these to fly around the yard!! it's gotta be a real wing flapper ornithopter though , no props - don't even bother ...

maybe a Da Vinci flyer also -- eddie123
Aerovironment made a pterodactyl but it crashed before its public trial. My personal opinion is that it flew with its neck extended and that caused stability problems. Most modern long necked birds bend their neck into an S shape and fly with their head close to their body.

Herons, storks and other wading birds fly that way. Ducks, geese and swans fly with their necks extended so it's a definite maybe on the stability question.

That said, I'd love flapping wing pterodactyl. They were almost certainly soaring creatures but all soaring birds of today can flap to take off.

Da Vinci's craft could never have flown but a fantasy version with higher aspect ratio wings would still be nice to have. I wonder how Da Vinci imagined landing his flyer?

Pete
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Old Today, 05:54 AM
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Some years ago I was asked to design & produce a simple 2-motor control EPP Ptero for TRU/Discovery Channel.

1. Although they called it a Pterodactyl, nor was it a Pteranodon, which means without teeth, as almost all of these giant flying lizards [not dinos!] were toothless, scooping fish out of the water while on the wing, I picked one of the few Pterosaurs that HAD teeth so they could present a safe non-pointy front!

2. NO predator wants to be seen, but TRU/Discovery Channel instead chose red & yellow for the kids; "the customer is always right" ....

It was very stable, but lacking the real animal's extensive sensor "fly-by-wire" system [far outdoing "AS3X"], the feet had to be enlarged to act as yaw stabilizers in tight turns. Only recently did I accidentally discovery when testing a series of albatross-like small test-configuration gliders for a UAV VTOL FPV tail-sitter project that without RC or artificial stabilization, tight turns showed too much spiral instability. By merely adding a small fixed and relatively tall vertical stabilizer AHEAD of the wing the problem totally disappeared, and from the front gave a stable-looking inverted "Y" configuration formed by the anhedralled swept wingtips and the FORWARD vert. stab!!

So I now know to a fairly high degree of certainty, that this fwd vert. fin at the rear of most Pteros' heads was there not primarily to stabilize the long snouted head ... but to stabilize the entire animal in flight. Any who have tried to fly a model without its vertical stabilizer [V-tails have a vertical component] will understand how important this aspect is for stability; modern futuristic aircraft w/o this feature must use artificial stabilization [the B-2 flies with its wingtip drag-rudders open except when in pure stealth mode].

And knowing that, instead of purposely diminishing the yaw/roll effect of the head-fin on my ptero toy, I would now do as the real animals did [and my albatross-like design test-model below], flatten, raise and enlarge that and get rid of the stupidly large big "feet".

Lee


Edu-Science video [independent of TRU/Discovery Channel sales!]

R/C Pterosaur (1 min 6 sec)


user's vid
TRU Pterodactyl (0 min 22 sec)
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Old Today, 05:29 PM
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Thanks xlcrlee,

This is very interesting. I'm far to lazy to build a model like this, mostly because I have very little room and a lot of work to do clearing off my workbench. I'm very interested in why it works though. Vertical surfaces are a substitute for dihedral in wings like the vertical surface on modern submarines banks the sub so it makes a coordinated turn.

I'm mostly curious about why it works so far ahead of the CG and center of lift.

Too bad the second video is so hard to interpret.

Maybe Festo will build some large, slow models and explore this for us.

Pete
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Old Today, 05:39 PM
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Thinking about it the neck of your pterodactyl look like the neck is not extended as was the Aerovironment version. I'll look on the Internet to see if I can find pictures of it.

Pete
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Old Today, 05:46 PM
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Pete, I can only theorize that the DESIGNED-in vortex-stabilization "system" I discovered that augments the rear vertical projection of the wings and has a longer moment than the fwd vert. fin accounts for normal yaw stability, and the fin itself keeps the nose up in tightly banked turns, as would a fwd V'd and/or swept stab [misnomered "canard"].

One must remember that "All Aerodynamics IS Empirical" and that apparently the Pterosaurs evt. found this out a while before we we born.

Lee
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Old Today, 05:46 PM
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Here's MacCready's version. Not the extended neck.

Pete
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Old Today, 06:12 PM
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He once spent an hour with me [my Boeing aerodynmicist buddies wanted us to meet] and after flying my coverstock Bald Eagle glider I made for WhiteWings [the eagle wore realistic original full color artwork made by an experienced wildlife painter], Paul told me it was the best small glider he'd ever seen.

I can't say, but propose that the Pteros also steered or stabilized with their necks
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