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Author Topic: center of gravity and lead out location  (Read 734 times)

Offline scott matthews

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center of gravity and lead out location
« on: February 21, 2012, 06:48:16 PM »
Well I have another plane finished and going to balance it and position lead out location.I am using the article from Aeromaniacs that's called Bench Trimming A Stunt Ship, to find that doing my math the center of gravity falls a little more than 5/8 of an inch farther forward of the plans. I figured the MGC and used the percentage recommended for a non flapped plane( used 14% to 18% of MGC) this has me worried to be off this far from the original planes. Would you use this position or just use what is called out on the plans. This position also has my lead outs all the way forward in the slot in the end of the wing. Can someone put my mind at ease about this?

Offline Randy Powell

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Re: center of gravity and lead out location
« Reply #1 on: February 22, 2012, 11:31:02 AM »
Scott,

Nose heavy isn't usually a problem. It may be sluggish but it will be perfectly flyable. The leadouts should be around 3/4" behind the CG to start. If the plane is sluggish, you can start adding tail weight in small increments until you're happy with it (and move leadouts back accordingly). Tail heavy is a different problem and can cause real problems flying if it gets too far back and becomes touchy and unstable.
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Offline Jim Thomerson

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Re: center of gravity and lead out location
« Reply #2 on: February 22, 2012, 03:52:57 PM »
I balanced a SigTwister at 15% MAC and it flew to suit me. 

Offline scott matthews

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Re: center of gravity and lead out location
« Reply #3 on: February 22, 2012, 04:32:33 PM »
How often does the CG end up in a different place than the plans call out? I only used the formula to see how well it would work out and now I am obsessing over the new location.Also I am assuming that when you find the mean cord average you are measuring from the center of the body to farthest point on the wing tip.

Offline Bill Little

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Re: center of gravity and lead out location
« Reply #4 on: February 22, 2012, 05:58:32 PM »
Hi Scott,

The CG shown on the plans is a suggestion.  Often the individual might like the CG in a different place.

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