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Balancing a nitro airplane

PostPosted: Thu Aug 25, 2011 1:02 am
by Treebuster
I have a .65 O.S. powered trainer with 14 oz fuel tank. I have read everywhere that you balance the plane at the COG with the fuel tank empty.

My tank, like almost all, is located right behind the firewall and of course ahead of the COG balance point.

Just wondering since you (hopefully) land without your fuel tank empty, maybe 10-25% fuel left, that maybe it would be better to fill tank with around 20% of capacity and then balance it, since it would better represent COG at landing....or am I getting to particular and maybe it should not matter that much.....any thoughts?

Re: Balancing a nitro airplane

PostPosted: Thu Aug 25, 2011 1:53 am
by RCModelReviews
It's really not that critical but in theory, the model should be balanced with the fuel-tank empty or near-empty since extra fuel will move the CG forwards which is safer than having the CG too far back.

In the case of a trainer, any CG that is within the range of 25%-33% back from the leading edge of the wing should be fine -- that's quite a range.

As the CG moves forwards the plane will require a little more up-trim to fly level but will be less sensitive to the elevators.

As the CG moves backwards, the model will tend to float a little more and the elevators will become more sensitive.

Too far forwards and you won't be able to flare the plane properly for landing. Too far back and the elevators will become so sensitive as to make the model difficult (or impossible) to fly.