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Old Sep 05, 2014, 08:54 AM
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Marcialtech 2014

Hello everyone,

I have been away for a while and had to put my Orny project onhold ( almost 2 years ) , my stuff are still in boxes but im slowly getting back into it.. here's a few photo and info of what i have..

3rd gen.
10 foot wingspan ( 3 meters )
3.2 lbs ( 1450 grams )
4 cell 1200mah 45c lipo
full size metal gear servos
3536 1250kv motor


Fred M.
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Last edited by Marcialtech; Sep 11, 2014 at 01:32 PM.
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Old Sep 05, 2014, 12:46 PM
Wid
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Welcome back

That is great news. Very much looking forward to your success.

I am still looking for a good way to limit the rise of trailing edge during glide and down stroke and still allow it to deflect downward during upstroke.

I really enjoy watching the beautiful wing movement on the latter part of this video.
Robotic Eagle Project 3.wmv (2 min 25 sec)


Smooth air and happy landings,
Wid
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Old Sep 05, 2014, 01:23 PM
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To limit rise of trailing edge during downstroke, put a downward curve in the spar as seen from the front, and increase span wise tension.
See front view of wing in attached image.
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Old Sep 05, 2014, 01:45 PM
Wid
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Elegantly simple solution

Quote:
Originally Posted by JimC3 View Post
To limit rise of trailing edge during downstroke, put a downward curve in the spar as seen from the front, and increase span wise tension.
See front view of wing in attached image.
What an elegantly simple solution! I will do some experiments to quantify. Thank you very much.
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Old Sep 05, 2014, 01:55 PM
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Note that a slight aftward curve in the spar increases the effectiveness. It works best when there is no roach in the trailing edge.

In pterosaurs, maximum rate of downward curvature is located at about 45% of the semispan. Increasing chord at tip will move the location of maximum rate outboard. So will flapping.
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Old Sep 05, 2014, 02:47 PM
Wid
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Quote:
Originally Posted by JimC3 View Post
Note that a slight aftward curve in the spar increases the effectiveness. It works best when there is no roach in the trailing edge.

In pterosaurs, maximum rate of downward curvature is located at about 45% of the semispan. Increasing chord at tip will move the location of maximum rate outboard. So will flapping.
As I examine the wing on my SK Lazy Hawk I see it has a substantial roach and that is what I am seeing deflecting so much. Eliminating it would reduce wing area substantially. I suspect the loss of lift would not be prohibitive (because of the extreme deflections) but the loss of thrust would be missed. Still, a decent light weight airfoil seems worth it.

For Marcialtech's wing (I don't want to hijack this thread too seriously) and SK wings, I was working on battens that flexed downward more easily than upward. Making a little progress, not satisfied with results yet.

Edit: See Roach thread for more info.
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Old Sep 07, 2014, 08:47 AM
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Quote:
Originally Posted by Marcialtech View Post
Hello everyone,

I have been away for a while and had to put my Orny project onhold ( almost 2 years ) , my stuff are still in boxes but im slowly getting back into it.. here's a few photo and info of what i have..

3rd gen.
10 foot wingspan ( 3 meters )
3.2 lbs ( 1450 grams )
4 cell 1200mah 45c lipo
full size metal gear servos
3536 1250kv motor


Fred M.
Looking great i see the wing is solid and membrane as well .Does the solid area have airofoil regards Brian
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Old Sep 07, 2014, 09:20 PM
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If your wings are solid to the trailing edge or compression battened, roach is OK. If tension battened, roach can't be supported.
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Old Sep 07, 2014, 10:00 PM
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Originally Posted by therealthing691 View Post
Looking great i see the wing is solid and membrane as well .Does the solid area have airofoil regards Brian
Yes , it does have Airfoil...

i'm already working on a revised version of this wing, there's a few more area that needs improvement.

here's a photo of the old wing ( upstroke photo )... the wing twist and flexing need some improvement.

Fred M.
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Old Sep 09, 2014, 02:44 PM
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Quote:
Originally Posted by JimC3 View Post
To limit rise of trailing edge during downstroke, put a downward curve in the spar as seen from the front, and increase span wise tension.
See front view of wing in attached image.
There is an interesting correlation between the resulting distribution of wing-twist in the wings of this ancient creature and the slightly less-ancient albatross and the latter discoveries of the Horten brothers as it applies to nurflügel and in theory to other modern conventional aircraft wings: namely that the maximum twist most efficiently occurs somewhat inboard of the wingtip.

Al Bowers describes the latter four here >

NASA's Albion H. Bowers - " Why Birds Don't Have Vertical Tails" - AMA EXPO 2014 (38 min 48 sec)
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Old Sep 10, 2014, 07:04 AM
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In pterosaurs though, the spanwise location of maximum twist depends substantially on the amount of aftward spar bend in phalanx IV-3 and IV-4. This bend is quite variable both between species and between individuals -- even between left and right wings. A few species don't have a IV-4. Combined with the curvature described above, the spanwise location of maximum airfoil twist can be actively shifted by a pitch rotation between the distal carpal and metacarpal IV. It also moves outboard as the speed of the wingtip relative to the wrist is increased.
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Old Sep 10, 2014, 08:51 AM
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Cool!

The Al Bowers info did not address flapping wings, but since I know that pterosaurs could "morph" their wings though lots of musculature, they must have been able to find the "sweet spot" for all their moves [flt. regime].

It would be interesting to be able to at least "first-order" approach this ability with an ornithopter, even with an onboard computer-chip [amps used vs some GPS data or airspeed indicator, etc], similar to how some expensive cars can self-adjust for maximum economy. but simpler to ground-test and pre-program membrane tightness & amount/position of roach-slack, somehow simply servo-adjustable in-flight. Simplest yet to select one overall best setting for typical flying, noting that even non-RC model sailboats can have the mainsheet, etc., adjusted before launch to suit conditions.
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Old Sep 10, 2014, 11:33 AM
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Keep in mind that spanwise tension in a pterosaur wing varies substantially along the semispan. It isn't constant along the span nor distributed nor adjusted in the same way as in a boat sail. Nor is a boat sail distribution desirable. Same for chordwise tension.

Since pterosaurs use most of their body parts for multiple, independent, sometimes competing, needs, they tend not to optimize for any one purpose. They tend to get good enough and leave it at that. Even so, they were more efficient than birds. Enough so that they could afford the big draggy heads and necks that birds can't afford.

Forget pterosaur roach. It will cause an immediate uncontrollable flutter and crash due to the lack of compression battening.

Also, don't incorporate a trailing edge tendon. They didn't have one.
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Last edited by JimC3; Sep 10, 2014 at 11:39 AM.
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Old Sep 10, 2014, 12:10 PM
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Great info, JimC3:

1. OK, roach forgotten

2. clear that aircraft are not sailboats*, and also that some ornithopters don't use membranes [Robird, for ex.]


*nevertheless my feathered friend Kiki sometimes calls sailboats "Kiki" [bird] because he noticed they have a vertical wing: he even started to clean his wing as a school of small sailboats ashore next to us had their sails furled ....
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Old Sep 10, 2014, 02:11 PM
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This doesn't have anything to do with aircraft vs sailboats or membrane winged ornithopters. It has to do with - nothing else that interacts with airflow internally reinforces and manipulates its membrane anything like a pterosaur does. Making a wing 'look' like a pterosaur wing doesn't imply that the wing will react or fly in any way anything like an actual pterosaur wing does.
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