Is it me or is this confusing?
 

I'm trying to balance my trainer and I'm told that the cg should be 1/3 the way back. How full should my tank be?

Thanks, Dave Trimmer

RE: Is it me or is this confusing?
 

Dave,
The fuel tank should be completely empty when you balance your plane.

Ken

RE: Is it me or is this confusing?
 

Dave,

Which trainer. 1/3rd the way back is a decent start but it's better if you know exactly where. If you don't someone else might

RE: Is it me or is this confusing?
 

never balance a plane with any fuel in it.

1/3 back makes perfect sence. take the length from the leading edge of the wing to the trailing edge of the wing and divide by three. set it 1/3 back from the leading edge of the wing, 9 times out of 10 this is the rear edge of the spare

RE: Is it me or is this confusing?
 

Most trainers I've seen balance on the spar.

RE: Is it me or is this confusing?
 

enter the measurements and this site calculates your cg for you;)

http://sky.prohosting.com/air2/cg_calc.htm

RE: Is it me or is this confusing?
 

Ive always balanced front spar bottom of the wing, slightly nose tipping. With an empty fuel tank.

RE: Is it me or is this confusing?
 

depends on the trainer, I've seen ones where the CG is almost 35% of the root cord, others were 18% - 25% ... well, wait a minute now ... Were you just told this? Or is this what the manual calls for?
I had a Hobbico trainer and the cg on that was 2 1/2 inches back on a 10 inch wing cord ( 25% )... which, after the second tree it hit, I found out is exactly where the spar is. There is a trainer ... a tail dragger ... can't remember the name of it, but the guy was talking about the CG being 4 inches from the LE and had a 12.5 inch root cord. Well, just find out for sure, because there's a big difference between landing and crashing with style.

RE: Is it me or is this confusing?
 

Every plane I've assembled to date gave exact measurements for the CG range from the leading edge of the wing, not fractions or percentages.

RE: Is it me or is this confusing?
 

With your plane--yes, you balance the plane empty of fuel. This represents the aft most position of the CG. So, when you fill it up with fuel, the CG moves forward--which is manageable. However, on pusher type planes--and in any case where the fuel tank is located behind the CG, the plane is usually balanced full of fuel--again, representing the aft most point of CG.

To reitereate--with your trainer--empty of fuel, and on the spar would be a great spot to start--especially with such vague instructions!

RE: Is it me or is this confusing?
 

Try reading the manual? They usually tell you where it is.

RE: Is it me or is this confusing?
 

Maybe next time I shouldn't by it used from the flea maket.:D

RE: Is it me or is this confusing?
 

Dave does the plane have any identification ?
Lots of times a plane will have its name right on the wing.
If no marking to ID the beast if you post a picture here someone might know what it is.

RE: Is it me or is this confusing?
 

I am not trying to be trite or crass, but I think it would be extremely important that you do a little studying up on the aerodynamics of airplanes. Believe me I truly understand the urge to get out there and fly, but understanding the basics will make you a safe flyer, as well as a happier one too. It can be a pain, but knowledge is power. Good luck and welcome to the hobby.

RE: Is it me or is this confusing?
 

For a trainer -- tank empty.

25% aft of the leading would be safe. It might not be optimal for that model, but it will be safe.

RE: Is it me or is this confusing?
 

About the only time you would balance with fuel in the tank is if the tank is AFT of the CG.

RE: Is it me or is this confusing?
 

Hi Dave, I agree with the responses so far, & my recomendation would be, get an instructor or experience pilot to check out your plane, he will check directions of flying surfaces, balance engine tuning & so on, & to fly it & trim it for you. better than doing it yourself & decking your new bird.
Cheers, & good flying.
Allan