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Old Apr 12, 2015, 07:56 PM
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Video
Chucking the JB-2 to find CG

Just finished building a Republic Ford JB-2 and did some CG testing...

Chucking the JB-2 to find CG (0 min 40 sec)


Looks like I have a balloon or a spring on the nose the way it bounces. It's just a 6" long piece of EPP on the nose. No damage whatsoever.
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Last edited by djacob7; Apr 13, 2015 at 12:39 PM.
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Old Apr 13, 2015, 12:27 PM
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what happened to the video?
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Old Apr 13, 2015, 12:35 PM
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Sorry about that... fixed.
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Old Apr 13, 2015, 02:49 PM
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An itch?. Scratch build.
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Have a look at this thread in the Giant Electric Planes forum --

Giant RC V1 flying bomb
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Old Apr 13, 2015, 02:53 PM
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An itch?. Scratch build.
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P.S. , from the video, the model looks too light to check the CG by chucking. There is no real mass to allow the model to use gravity to glide.

If you chuck a real light weight too hard it will just zoom, it's trying to fly faster than it wants to for the set up.

Try adding some lead around the expected CG location.
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Old Apr 13, 2015, 06:51 PM
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Build straight - Fly twisty
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With a plan-form like that here is no need to chuck it to see where the CG should be.
25% of the cord will be a conservative position suitable tor a test flight.
Subsequently bring the CG back to where you like the way it feels.
I follow full-size practice. They didn't get a bunch of guys to test chuck the A380 did they?
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Old Apr 13, 2015, 10:59 PM
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@Ray: Great thread, Ray. And so recent too!
@Whiskers: 25% is exactly where it ended up!
Almost ready to maiden....
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