What C of G methods do you use for your sailplane?

[Wild Doogie]

I did not see any information on this website.......looking for methods that work best for these large sailplanes.

Thanks!

[Stew2]

I use the Vanessa Rig. I will set the sailplane up on the floor and then block the tail up until an incidence meter on the horizontal stabilizer reads zero. Lift the airplane and adjust the Vanessa rig until the distance from the tailwheel to the block and main wheel to the ground are the same and the plumb bob tells you where the C.G. is. Be careful translating the C.G. location from the root rib to the top fuselage centerline, you can introduce error there. But you can determine the CG on a very large very heavy airplane this way without damaging it. The final C.G. is always set by flight testing.

http://creswellrcflyers.org/Text/Vanessa_CG_Machine.pdf

[Wild Doogie]

Thanks for the reply Stew2. Can you use a level on the horizontal stab instead of an incidence meter?

[Stew2]

If the horizontal stabilizer does not have an airfoil cross-section, you could. Otherwise you will be balancing in negative incidence in the stabilizer which equates to a nose heavy airplane. That is assuming that you put the level on top of the horizontal stabilizer. Many people eyeball the stab incidence, which is the same thing as judging "slightly nose down" which is the classic description of safe balance/C.G. location.