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Old Feb 24, 2013, 09:52 PM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
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Quote:
Originally Posted by djacob7 View Post
There's nothing like trying, so I did. Easy to build; not so easy to fly.
I feared that it would be tricky to overcome prop torque because of the very small "wing" span, and my fears were verified as you can see in the clip.
Next I will try to fly it without the tail...
http://www.youtube.com/watch?v=7HiSd...ature=youtu.be
that is the typical spirit of the scratchbuilt
pls kindly post some pics on the head & connecter (between segment) if available
regards
Sam
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Old Feb 24, 2013, 10:49 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
1,594 Posts
Here you go, Sam...
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Old Feb 25, 2013, 04:32 AM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
1,885 Posts
Quote:
Originally Posted by djacob7 View Post
Here you go, Sam...
thanks indeed
will start to build in next couple days
regards
Sam
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Old Feb 25, 2013, 08:51 AM
Kamikaze Ace
Glacier Girl's Avatar
USA, FL, Lakeland
Joined Jan 2010
2,348 Posts
Hmm, I went full screen on the video. At the 3:29 mark I stopped it, to me it appears there is a
frame of some type used around the outer edges of each segment. Can just barely see it.
Like he doubled or tripled the material. Thinking this would spread out the stress over the entire section.

Also looking at the video after the crash, 3:23 mark, the segments are twisted badly but the twist is at the hinge. it appears to me, the hinges are triple duty, not only allowing left and right, but also up and down movement. Maybe pinned at each connection to allow the left right and using something like Mylar to let it move up and down also, and allows it to twist slightly.
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Old Feb 25, 2013, 10:52 AM
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DeBary, FL
Joined Nov 2010
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Quote:
Originally Posted by Glacier Girl View Post
Hmm, I went full screen on the video. At the 3:29 mark I stopped it, to me it appears there is a
frame of some type used around the outer edges of each segment. Can just barely see it.
Like he doubled or tripled the material. Thinking this would spread out the stress over the entire section.
Video compression artifact. The 'youtube' version is best but even that's very bad. Check 0:12, the entire outline of each segment has a 'halo' around it caused by the high contrast between the white foam and dark grass. Other in flight views with sky background don't have halos, or any shadows or other hints that there're any doublers.

'Full outline' doublers aren't necessary. The main line of stress runs straight down the spine of the snake to pull all the segments. The 'wing' portion of each segment stresses inwards to the spine but there's no need to double the entire LE/TE of each segment, just the spine portion, and definitely no need at all to double the outer edges of the segments.

Quote:
Also looking at the video after the crash, 3:23 mark, the segments are twisted badly but the twist is at the hinge. it appears to me, the hinges are triple duty, not only allowing left and right, but also up and down movement. Maybe pinned at each connection to allow the left right and using something like Mylar to let it move up and down also, and allows it to twist slightly.
From 0:30 to 0:45 there's definitely *something* on the underside involved in connecting the segments. But maybe they're a separate plate on each segment for reinforcement not directly connecting the segments. Because, if they were directly connecting the segments then the way the segments rotate 180 deg around to 'stack' them couldn't happen.

A piece of CF cloth with a thin-thin film of maybe canopy clue would be extremely flexible and extremely strong. Doubler/strength doesn't need to run the whole outline of the segment just at the joints.

Foam doublers would be a bunch stronger but still brittle and nowhere near as flexible as the twist at 3:23.

Mylar as you mentioned is definitely possible that's very strong stuff.

I'll bet he had a bunch of failures trying to find the correct technique of strengthening the joints yet keeping flexibility way up *and* weight way down.
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Old Feb 25, 2013, 02:23 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Since roll is very hard to control with such a small wing span, I'm thinking of using a gyro on the roll. Maybe also on the pitch, we'll see.
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Old Feb 25, 2013, 05:04 PM
I don't do Normal
Pinky_d_brain's Avatar
Canada, NT, Yellowknife
Joined Dec 2011
419 Posts
You ever think of using something like this to connect the tail together
LINK
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Old Feb 25, 2013, 05:18 PM
Fremont, CA
United States, CA, Fremont
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Pinky, that hinge might work, the only problem is that it's supposed to be able to fold on top of itself (180 degrees rotation).
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Old Feb 25, 2013, 05:51 PM
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DeBary, FL
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Originally Posted by djacob7 View Post
Pinky, that hinge might work, the only problem is that it's supposed to be able to fold on top of itself (180 degrees rotation).
Well it depends on which way you orient the axle.

If oriented to rotate in yaw dimension, same as yours, I think is toooo rigid in pitch. The one you made, similar to the vid flying effects, is most flexible in yaw but still slightly flexible in pitch and roll. It's gottta have some 'give' in all three dimensions or something will *snap*.

It did make me think though whether the 'one freest' dimension -should- be yaw or pitch. The chain of segments -could- conceivable fold 'vertically' rather than horizontally.

I think that with a horizontally oriented linked chain of lifting body segments, because the -pitch- is not totally free, each segment slightly 'supports' the next segment in the chain. If pitch were -totally- free and unsupported then the slightest downdraft at -one- segment would allow that segment to purely -drop- instead or being 'encouraged' to stay up by the segment in front of it.

And, when that one segment drops all the segments behind it suffer loss of thrust too, and will lose airspeed and drop. Then when the thrust 'catches up' with the segment that dropped there's a *yank* to get it back in line. And all the segments behind it suffer a similar yank. Not good.

Final answer: you've got it right rotation in the yaw dimension.
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Old Feb 25, 2013, 06:02 PM
gpw
“There’s no place like Foam”
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Joined Jul 2002
24,049 Posts
From studying the video intently , it would appear the plates ‘ are a very thin flexible material joined with simple loops , and the shape of the front of the plate(s) encourages it to follow along in line in the “relative wind” . ...Overcomplicating it only forces weird things to happen ... a situation I also found with my “Rods” ... simple works , like a segmented paper tail ... and keeping the tail Light means less of a CG problem ...
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Old Feb 25, 2013, 08:12 PM
Canadian Bacon
flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
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Thinking of trying this with some 1/8 in. coroplast that I have. Maybe doubled layer at the hinge points.Fairly light quite strong.

Gord.
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Old Feb 25, 2013, 08:35 PM
TonyS
United States, AR
Joined May 2010
563 Posts
For what ever they may be worth, some screen capture images...

TonyS
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Old Feb 25, 2013, 10:14 PM
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Minnesota
Joined Jun 2007
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I am extremely interested!! Ive been trying to find a way to incorporate a snake into a plane. I lit up when I saw this thread!!

Shes the inspiration:
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Old Feb 25, 2013, 10:55 PM
DIY Mania from Taiwan
Taiwan
Joined Aug 2011
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Quote:
Originally Posted by tonystro View Post
For what ever they may be worth, some screen capture images...

TonyS
well done
thanks for posting
regards
Sam
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Old Feb 25, 2013, 11:04 PM
Registered User
DeBary, FL
Joined Nov 2010
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Quote:
Originally Posted by djacob7 View Post
Since roll is very hard to control with such a small wing span, I'm thinking of using a gyro on the roll. Maybe also on the pitch, we'll see.
See the post just above that mentions ball python? So I said to myself, I says, 'Self, let's go look at some snake pics and find out how wide we can make the head and still keep it looking very snaky.' So I said back to myself, I says, 'OK,' and I came up with https://www.google.com/search?q=ball...w=1370&bih=789

It looks like the base of the head is almost twice as wide as the start of the body.

So, add a bunch of width, and 'fade' the head into the body, and it'll look fine.
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