Question:

How to Measure the Correct CG at the Wing ROOT?


Detailed Explination:

So I have a Seagull Models 75 sized ARF (Extra 300S).

Manual can be found here:

http://www.horizonhobby.com/ProdInfo...0usaManual.pdf

But they recommend the CG to be set at 4.5CM measured at the Wing TIP. I do not have another person, plus it seems silly when I have a great planes CG Machine to balance all my other planes.....

http://www.greatplanes.com/accys/gpmr2400.html


If I run a string as shown in the attached pictures, you can see I get 9.5 CM to 10CM at the wing root. Is that the real CG at the root?

Is it safe to balance this way?

Are they equivelent?

Thanks for the feedback in advanced.....

As long as the point of contact between the string and the fuse does not give you a false reading, and it is in line with the wingtips, you are doing the correct measurement.

As a bonus, having a straight line spanwise, allows you to use a balancer of any width, having the right distance from the LE at any point.

The actual CG is located in a vertical plane over the center line of the fuselage; hence, any reference, like the LE at the wing tips or at the wing root, is just that, a reference.

Nice model, Tom; enjoy it!

Thanks.......I will also have someone at the field confirm the "Tip" measurement before maiden, which will be soon.

Have always done it the way you did. Shouldn,t be any less acutate.

Have always done it the way you did. Shouldn,t be any less accurate.