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-   -   CG balance? Please help. (https://www.rcuniverse.com/forum/arf-rtf-75/450627-cg-balance-please-help.html)

rosenbaum11 12-31-2002 09:24 PM

CG balance? Please help.
 
I just got a cg machine ,read instructions put it together put plane on location from leading edge specified by plane instructions. The problem is what reference line do you use to make sure plane is balanced? Stab level, wings level,fuse level & if so how do you get reference line on fuse. lookin for some place to use a bubble level to balance plane . Got an ultra stick on the way & want learn how to balance my old plane first.Please explaine the reference points places to put level. Or step by step how to balance a plane . PS" IM LOST!


__________________
"Thanks Scott"

Steve Guinn 12-31-2002 10:42 PM

CG balance? Please help.
 
I think you're trying to make a mountain out of a mole hill. It should stay reasonably level with hands off. If tail or nose drops significantly move batteries fore or aft, or add weight.

rosenbaum11 01-01-2003 07:05 AM

CG balance? Please help.
 
Maybe so! Im new in hobby just trying to learn the proper way to balance a plane . Werent you there at some point. Ps maybe some one else will try to answer my question.

Jemo 01-01-2003 02:04 PM

CG balance? Please help.
 
Scott,

If there is a place on your plane to put a level on it, then do so on the bench, to get an idea what it should look like on the balancer.

Depending on the plane, the thrust line (engine shaft) , the wings and stab should be level.
If you use the level on the balancer it will only throw you off because of the weight of it.
After you do your first one it will look pretty obvious to you. Don't get fooled by the shape of the fuselage, sometimes it will look like the nose is down or up when actually the thrustline and wings are level.
After all is said and done, let it be slightly nose heavy and you will be fine.

High wing plane balance right side up... Low wing balance upside down, makes things easier.

I don't think Steve meant anything by his answer, he just didn't elaborate.

Bob Pastorello 01-01-2003 03:47 PM

CG balance? Please help.
 
I've been using the CG machine for several years, up to 90" wingspan airplanes, and it works fine. The advice about "learning" what level looks like on the bench is great. In addition, GENERALLY, most stabilizers are 0-0 relative to the longitudinal fuselage axis. What I've done is used a stool, or table to put the balancer on, then the plane, and I just measure up from the floor....looking for the same measurement on the stabilizer Leading edge as the elevator Trailing edge.
After you do your first one this way, you'll see that it is very easy and lets you get really accurate.
The part about erring on the side of slightly nose heavy - GREAT advice. In the three decades I've been playing with these I've NEVER gotten bit by a nose-heavy airplane. Wish I could say the same for TAIL heavy airplanes. <Ugly crash story>
The CG machine is VERY sensitive to very small changes in nose or tail weight. I had to shutoff the air conditioner floor vent when I did my last Extra, as the airflow on the stab was making it rock up and down.

Steve Guinn 01-01-2003 05:42 PM

CG balance? Please help.
 
Hey Scott,

I was just trying to be helpful. Did not intend to sound derogatory. I just don't believe it has to be so exact. Get within the safe limits, fly it, then adjust to your liking.
Thank you jemo.

:)

rosenbaum11 01-02-2003 01:36 AM

CG balance? Please help.
 
No problem Steve.


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