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Old Aug 04, 2013, 04:44 PM
flyingflipper is offline
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Great Planes RV-4 What is the true COG?

I bought a used but pristine electric RV-4 and I can't wait to take it out and fly it. I downloaded 2 manuals for the RV-4 and they both show different CG's and ranges. I can't ask the former owner - deceased.

RV44P03 for GPMA0180 V1.0 copyright 2001
CG - 4 3/8"
Range - 1" [25mm] forward or 3/8" [9.5mm] back

GPMZ1357 for GPMA1357 V1.0 copyright 2006
CG - 3 3/4"
Range - 3/8" [9.5mm] forward or 1" [25mm] back

Any help will be appreciated.
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Old Aug 05, 2013, 11:53 AM
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There are several different ways to calculate CG and each one give a slightly different answer. Search here or google on how to do it, different people will swear their way is the only way. I have done it 3 different ways before and the averaged those results and came out pretty good.

I have a Slipstream 80" RV8 and the recommended CG is right on the wing spar. A lot of designers intentionally put it right on the spar or just in front of it.

Good luck on your quest for the right CG. When it comes time for the maiden flight you may want to have a spotter standing next to you so they can adjust the trims if necessary. That way you don't have to take your eyes off the plane during those first few turns.
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