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Old Mar 09, 2003, 09:16 AM
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Rochester Monroe Cty, New York, United States
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Skelecor

There is a thread where I first tried this:

http://www.rcgroups.com/forums/showt...threadid=87377

But, the Tadpoles and miniFrogs flew very well yesterday, so I think a complete building thread showing the entire process would be in order. I will start one this week.

Jerbear had it just right. Outline with a shallow cut, pick out the pieces to the center. The latest variation is to push to the center about 1/4-3/8", then dig in with your nail and push from the interior back to the line you have begun to remove. This variation needs a picture. Its advantage is that tears do not get very big.

Some sheets of F3 seem to be more skeletonizing-friendly than others. One side of a sheet may be easier to use than the other.

Good luck
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Old Mar 30, 2005, 03:20 PM
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Joined Feb 2005
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hi friends

i have made a pusher model such as the tadpole so some of questions.
what is the best point of CG for a pusher model such as tadpole?

can i say because the motor is mounted ar the back of the plane so the CG is at about 25 to 30% of TRAILING age of the wing(opposite of a puller model)?

with a pusher model i must use from down thrust for the model or up thrust????

thanks for any help
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Old Mar 30, 2005, 05:57 PM
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Not really actually. The cg of a plane is always relative to the shape of the airfoil, and the direction of travel. CG isn't really related to the location of the motor, however, having the motor in the back can sometimes make it hard to balance the plane far enough forward.

As for the direction of thrust, if you're not sure, make it straight, but you'll need to know if the thrust is higher or lower than the wing etc.

You want the direction of thrust to push the nose up slightly, or not at all. So, if the motor is higher than the wing, and is forward of the wing, then you need to point the motor up. If it's behind the wing, point it down. The plane will rotate around it's CG, so the motor should push in the direction that will rotate the nose up, or at least work out even.

Hope that helps a little,
-Dan
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Old Apr 03, 2005, 05:15 AM
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thanks Dan for your attention

but according to my experiences the C of G is at the back of the wing when we have a pusher motor so i cant see why the CG is related to the wing shape!?

i couldnt understand what did you say about: As for the direction of thrust, if you're not sure, make it straight, but you'll need to know if the thrust is higher or lower than the wing etc.
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Old Apr 04, 2005, 10:37 AM
The effect is sadly temporary
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Ann Arbor, Michigan
Joined Oct 2001
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No problem. The CG of a plane, and where it balances are two different things. You need both of these to be in the same place, or it won't fly well. So, yes the plane may balance at the back of the wing, but dont' fly it that way. You'll need to add weight in the nose until you can balance the plane at the correct CG.

As for the rest, all I can say is that a lot of angles and numbers on a plane depend on other factors in the design. You can find out a lot more about it by asking with a specific question about a specific plane. I tried to give a general answer because you said "such as the tadpole" and I don't know what's different about your plane.

Happy to help if I can.
-Dan
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Old Apr 04, 2005, 01:48 PM
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Rochester Monroe Cty, New York, United States
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Thrust line

The official Tadpoles had zero offest in either the vertical or horixontal planes.

Cabin-type tractor planes have downthrust because they are typically below and forward of the wing. If the motor thrust line is right through the center of drag, I don't think you would want any up or down thrust. My understanding of all this is fairly thin, however.

Direct drive Tadpoles have very little moment arm to cause yaw or pitch, so there would only be a small effect in any event.

John

PS. Tell us about your Tadpole. Pictures would be great.
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