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Old Apr 04, 2011, 01:33 PM
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There's magic in those wings !
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Why do some Ornithopter need a vertical fin ?

Hi

Well .. just as the title says .. "Why do some Ornithopters need a vertical fin ?" to fly properly ??

Your input is greatly appreciated

Khaled
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Old Apr 04, 2011, 02:38 PM
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Without, the device will "walk" - left and right and become uncontrollable eventually.
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Old Apr 04, 2011, 04:20 PM
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Thanks LIG .. but what makes SK, Kazu, Robert Musters, and cybirds don't need the vertical fin to fly properly ??... I mean what's the common thing between them and not there in the Festo bird ??

Thanks

Khaled
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Old Apr 04, 2011, 04:24 PM
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Old Apr 04, 2011, 04:25 PM
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I am no expert but my fix wing Gull needs Vertical fin to sty on track. RM mentioned about SmartBird is not as advance as his which I totally undestand where he comes from since his birds don't have vertical fin but they fly straight when under glide mode.

Again, this is smething to do with aerodynamic. I am a field operator, I fly many different things but I am no engineer. Perhaps some others can chip in.
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Old Apr 04, 2011, 05:14 PM
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Old Apr 04, 2011, 05:35 PM
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I think RM's B Eagle has spoiler on top of the wing but I think that's for turning purpose so it won't pop open untill you move the aileron stick
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Old Apr 04, 2011, 05:58 PM
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Old Apr 04, 2011, 06:19 PM
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yeah, the Alula effects. It is hard to create a human made Alula feathers on any flapping devices, weight is the main issue to incorporate that and also stopped many designs
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Old Apr 04, 2011, 09:08 PM
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From my experience, the roll axis are stable by movement a range of flapping to up.
So, a vertical tail becomes unnecessary

Air resistance or leading edge vortex etc are necessary at gliding.
----> Look Next VTR.

Moven does not fly at first.(Wing shape is simillar to Falcon)
But, by adding resistance to an edge after a wing, Moven had a stable flight and gliding.

メーヴェ 飛行の秘密 Möwen of Nausicaä Secret of Flight (6 min 15 sec)
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Old Apr 05, 2011, 12:17 AM
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i have a number of small gliders in my blog that do not need vertical surfaces and also do not have a wing sweep angle. the main trick is to balance them far forwards at say 15% MAC so that the drag pulls them straight. getting them to turn where you want can be more difficult though. but again, i cover that in my blog as well
http://www.rcgroups.com/forums/member.php?u=25418
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Old Apr 05, 2011, 02:35 AM
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My robirds glide well without fertical fins. I guess that it has to do with the tip vortex that keeps the bird on the rails. If you use a split elevator it will work too but you need always a back sweep.

http://www.youtube.com/watch?v=MTvP-HQYOgQ

Robert.
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Old Apr 05, 2011, 04:28 AM
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There's magic in those wings !
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Quote:
Originally Posted by bluefalconhollan View Post
My robirds glide well without fertical fins. I guess that it has to do with the tip vortex that keeps the bird on the rails. If you use a split elevator it will work too but you need always a back sweep.

http://www.youtube.com/watch?v=MTvP-HQYOgQ

Robert.
Hi Mr Robert

By tip vortex you mean the suction force that pulls the wing tip to the outside ...as if you were pulling the wing tips by two strings tied to them from both sides to the outside

just like the representation in the photo ...

Thanks a lot for your time

Khaled
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Old Apr 05, 2011, 05:03 AM
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The main differece is the direction of the propulsión air stream.
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Old Yesterday, 03:42 AM
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I would have to agree with kjell it makes sense imho also the higher average dihedral helps
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