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TedGM
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Posted: Wed Jan 2nd, 2008 07:17 pm |
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PatriciaJB wrote: Hi Ted,
I did coat stockings [this was the first membrane I made]..see discussion and photo on page 4 of this thread.
Cheers,
Patricia
I missed the discussion in page 4. (I jumped immediately to page 5 in a hurry). Good to know that you tried it already.
Cheers,
Ted.
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PatriciaJB
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Posted: Fri Jan 4th, 2008 02:02 am |
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I'm trying this idea for Boudica 2 first with several different fibres , some extensible and some inextesible.
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MiloA
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Posted: Mon Jan 7th, 2008 07:38 pm |
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aloha Dears,
? is the wing-skin of a living bat, as flexible and stretchy as the dragon-skin-composites ? (depends on the fabric used ?), are there any epoxy-materials with rubber-consistence, similar to a dragon-skin? and perhaps less stretchy, and with the option to manufacture easily very thin layers ?
I understand that bats and birds, fold their wings in the up-strokes,
as much as the situation allows and requires, (more vertical displacement, more fold-up), while insects don’t
(and several beetles, cover up their quite soft wings, with two almost rigid protection-caps on top, which serve as a fix lift-device, do those hybrid flappers save a lot of efforts, by means of this glide-lift ?)
? to harness full control, with an oscillating, double-pair of flapping wings,
should we search for enough, almost, vertical thrust, similar to
insects, just a propos a hovering dragonfly ?, (which got a multifaceted optical- and nerve-system, just to keep their 4 wing-tips in track, managing complete command)
felicidades milo
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PatriciaJB
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Posted: Mon Jan 7th, 2008 10:37 pm |
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Quote from Milo:
>>> "? is the wing-skin of a living bat, as flexible and stretchy as the dragon-skin-composites ? (depends on the fabric used ?), are there any epoxy-materials with rubber-consistence, similar to a dragon-skin? and perhaps less stretchy, and with the option to manufacture easily very thin layers ?" <<<
Hi Milo,
I don't know exactly how the wing membrane of a bat compares to dragonskin. The best research on bat flight, anatomy and membrane and bone properties is that done by Sharon Swartz. See list of people and papers and visualizations, simulations etc here. http://vis.cs.brown.edu/areas/projects/bat.html
I haven't been able to get any of her papers !!
Re: epoxy.
West system have a new flexible epoxy called 'GFlex' which elongates more than their regular epoxy and is ideal for certain applications. It's not really intended for laminating but they say that it could be used to good effect in small laminations that need to be more flexible than usual.
http://www.gougeonbrothers.com/G-flex/
http://www.epoxyworks.com/25/pdf/Understanding_Flexible.pdf
Re: Fixed/flapping wing hybrids;
They very probably would save a lot of effort but that isn't the point. The point of this forum is to produce a pure flapping wing aircraft that is stable and controllable and can sustain flight without assistance of any kind. The object isn't to sustain flight any way we can with the least amount of effort !! Our interest is flapping wings not fixed wings.
What aircraft is that in your photo above ?
Cheers,
Patricia
Last edited on Mon Jan 7th, 2008 10:38 pm by PatriciaJB
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TedGM
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Posted: Sun Jan 13th, 2008 06:12 pm |
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Hi Patricia,
I have managed to have time experimenting with stockings, stretched it (BUT NOT FULLY STRETCHED) and coat with silicone sealant. It was stretchable when cured.
Cheers,
Ted
Last edited on Sun Jan 13th, 2008 06:14 pm by TedGM
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PatriciaJB
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Posted: Wed Jan 16th, 2008 02:03 pm |
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TedGM wrote: Hi Patricia,
I have managed to have time experimenting with stockings, stretched it (BUT NOT FULLY STRETCHED) and coat with silicone sealant. It was stretchable when cured.
Cheers,
Ted
Hi Ted,
I didn't stretch the stocking before curing . It was stretchable after curing but didn't have nearly as much 'spring' or ability to return to original length as pure dragonskin and when extreme tension was applied it permanently elongated and developed many fine tears in the dragonskin coating. I think it would be good for applications where the loads were not too great and where less 'springiness' was needed. Less springiness in dragonskin can also be accomplished by using 'Slacker' which is an additive designed for this purpose..... I have some but haven't started testing it yet. The disadvantage of using 'Slacker' is that it decreases tear strength.
Do you have any photo's ?
Cheers,
Patricia
Last edited on Wed Jan 16th, 2008 02:04 pm by PatriciaJB
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TedGM
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Posted: Thu Jan 17th, 2008 06:01 pm |
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Hi Patricia,
Re: Stockings coated with RTV clear silicone sealant.
Attached is the photo you requested.
Cheers,
Ted
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 Last edited on Thu Jan 17th, 2008 06:10 pm by TedGM
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TedGM
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Posted: Thu Jan 17th, 2008 06:26 pm |
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| A closer look .... Attached Image (viewed 358 times):
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TedGM
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Posted: Thu Jan 17th, 2008 06:30 pm |
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No tear developed after stretching..
I'm convinced that silicone can be use as coating material for membrane wing.
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 Last edited on Fri Jan 18th, 2008 06:51 pm by TedGM
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PatriciaJB
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Posted: Tue Feb 19th, 2008 01:08 am |
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TedGM wrote: No tear developed after stretching..
I'm convinced that silicone can be use as coating material for membrane wing.
Hi Ted,
I agree that silicone can be used by itself for parts of the membrane but it becomes difficult when re-inforcements or constraints are embedded . The silicone must be prevented from stretching too much or it will tear away from the very constraining material that is there to prevent it from stretching beyond a given amount !!
Re: Stocking material.
My stocking material tests showed no tears at small stretch BUT there were many small tears [ in the silicone dragonskin not the stocking material] at high stretch. These tears are , at first, quite hard to see. They appear as a diffuse , whitish area which on magnification reveals itself to be many fine tears. Eventually, when the material was repeatedly subjected to extreme and rapid stretching and releasing, some of the dragonskin flaked off as fine particles.
Since it is so difficult to restrain the dragonskin from over stretching and tearing away from the restraining material if the load goes beyond a given amount then I think it can only be used in conditions where it is known for certain that the applied load will not go beyond the tear load..... or in conditions where nothing drastic will happen if it does go beyond the tear load !
Re: Boudica 2 update.
The gearmotor for Boudica 2 has finally arrived and construction has started !
I'm going to use a modification of the flapping sweeping mechanism that we discussed in the flapping mech's thread.
I will use dragonskin for some areas of the wings and tail.
Will keep you posted.
Cheers,
Patricia
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PatriciaJB
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Posted: Wed Feb 20th, 2008 10:55 pm |
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KJELL wrote:
Patricia.
What kind of gearmotor are you using? What kind of modification are you doing to the flapping sweeping mechanism? Pls show some drawings and pictures.
Kjell
Hi Kjell,
I'm going to try these 2 motors.
Banebots gearmotors.
Both have FF-180 motor and are rated for 4.5 volts
One has a 30:1 gear ratio , 427 rpm and 92 oz-in torque
The other has a 20:1 gear ratio, 640 rpm and 62 0z-in torque.
Both have metal gears { I've had many problems with plastic gears and plastic housings...... chewed teeth, split housings etc .... no more plastic for me !  }
Neither produce all that much torque. I'm building Boudica so that it will be easy to change motor/gearbox if necessary.
Re: Flapping mech:
I'm still testing several mod's of my original mech....haven't decided which one to use yet.
Cheers,
Patricia
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Sigurd
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Posted: Sat Apr 17th, 2010 12:43 am |
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Curious how it went with the maximum squared onion bag.
And I wanted to suggest polyurethane as possibly a stronger and easier to glue alternative to silicone. Some of those vacuum bags for laminating look very flexible. Vinyl is also used sometimes but I thought PU were stronger.
Nice work, did the second one flap yet?
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