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How to balance an airplane with a pod mounted engine above the wing

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How to balance an airplane with a pod mounted engine above the wing

Old 09-18-2010, 11:15 AM
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cslota
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Default How to balance an airplane with a pod mounted engine above the wing

I have a Ken Willard designed Wave Master that has the engine in a pod above the wing. I have tried to balance it both up right and inverted. The problem I have is that when balance is close to being correct, the airplane will either drop nose heavy or tail heavy depending upon the the attitude of the nose. For example, if I hold the nose slightly nose high, the tail will drop. If I hold the nose slightly nose low, the nose will drop. This happens when trying to balance the plane both upright and inverted.

Any suggestions?

Thanks,

Calvin
Old 09-18-2010, 11:38 AM
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HighPlains
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Default RE: How to balance an airplane with a pod mounted engine above the wing

It sounds like it is balanced. But you can hang it by one wingtip with a string taped to the balance point and see if it is nose or tail heavy. Another method is to tie the nose and tail with a string and let the model hang from a single point with the airplane about level. From the same pivot point hang a plumb bob, and it will point to the balance point.
Old 09-18-2010, 11:41 AM
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Top_Gunn
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Default RE: How to balance an airplane with a pod mounted engine above the wing

Make one of these:

http://home.mindspring.com/~the-plum...%20Machine.htm
Old 09-18-2010, 11:51 AM
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JohnBuckner
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Default RE: How to balance an airplane with a pod mounted engine above the wing


ORIGINAL: cslota
if I hold the nose slightly nose high, the tail will drop. If I hold the nose slightly nose low, the nose will drop.


Stop doing that. The airplane will not be at the desired balance point unless the airframe is relatively level. Always check CG with the airplane level not a schoosh nose down or any other schoosh. If you do that you have just balanced the airplane at some unknown point forward of what the target is so you really have no idea where you just balanced it at.

I agree with HP, sounds as though you are very close already.


John
Old 09-18-2010, 05:25 PM
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Augie11
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Default RE: How to balance an airplane with a pod mounted engine above the wing


ORIGINAL: Top_Gunn

Make one of these:

http://home.mindspring.com/~the-plum...%20Machine.htm
The CG device based on the Archer design is a good one and you'll find some threads discussing the pros and cons. However, the advise to balance the plane LEVEL is well taken. That 'nose down a bit' will usually give you a noseheavy plane.....not that that is a big problem.

I've had several pod designs and they seem to be the most critical to balance the most sensitive that is. Try the level balancing technique. You are probably pretty close right now based on what you are describing. I never had that specific plane but I'm assuming the designer says to balance her with an empty tank and that's what you're doing.

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