I have question about balancing the SIG Four Star 40. I haven’t seen this question posted before, but if this is redundant just point me to where I need to go.

Using my Great Planes CG Machine I balance this plane perfectly. I had the plane in the CG machine so that the landing gear was pointing up and pivot points of the CG machine right on the center of the main spar on the wing. I was very proud of the job that I did balancing this plan.

When I took the Four Star to the field it was obviously tail heavy and the pitch control was extremely sensitive. Some how I lucked out and was able to get it back to the ground with only minimal damage.

I now have the Four Star repaired and am ready to balance it again.

I was wondering if some of you experts could tell me where I went wrong in balancing this plane.
The Four Star has +1/2° incidence on the wing and I was wounding if by placing the plane on the CG machine upside is what caused the error.

If some one has some Ideas I would like to hear them.

Thanks,

Mike

Verify the balance point on the plans, not all planes balance at the main spar.

bhole is correct. I don't remember where the CG is supposed to be on a 4*, but not all planes use the Spar as a balance point.

Second: Even if that IS the correct CG point, remember that it is only a reference point. Now that you have flown the plane, and you KNOW it's tail heavy, Shift some weight forward, or add nose weight. Keep making slight changes until the plane flies the way you want it to.

I fly the 4*40 with CG 2" from the LE. which was near the spar.

I used GP balancer and put the plane inverted.

I have verified the balance range on the plans. The plan has an arrow pointing to the leading edge of the bottom spar and an arrow pointing to the trailing edge of the bottom spar. Between these two arrows is the text "BALANCE RANGE".

I Realize that the balance range is just a reference point, and that is what one of the guys in my club was saying at last nights meeting.
We had the Four Star and the Balancing machine at the meeting we took the batteries out from where I had them and relocated them under the fuel tank. This made the model so nose heavy that it would not even sit on the CG machine. Then that is when this other guy said that the plane will fly like that.

I know the plane will fly nose heavy, but I would like to get it closer than it is right now.

Thanks for all the input, I think I will do what you all have been trying to tell me. Get the plane where it will fly then make small adjustments until it will fly the way I want it.

Try flying the plane nose heavy and see how it handles. You can then slowly start shifting the battery back a little at a time until it handles the way you want it to. A nose heavy plane flies well, a tail heavy plane flies once.(usually)

I may be showing my ignorance but, mine flys great with it balanced on the rear of the main spar. I used the GP Balancer also. Check your tail incidences somethings wrong. Also double check the ailerons. I have mine reflexed up about an 1/8". Another thought what is your thrust line of the motor?
John