ORIGINAL: spiral_72
Yea, I don't doubt that she flies straight.... Lemme explain:
If your CG is too far back and your model is nose heavy with correct engine down thrust.... You'll have to give it up trim to keep the nose level.
If your engine thrust is high or low you'll have to add down or up elevator to keep the nose level.
If your engine thrust is left or right you'll have to add right or left rudder to keep your nose on course.
All these add drag to an airframe and depending on the severity, things can get pretty bad especially if you have multiple problems. What you want is an efficient plane. When I started this stuff, I put a plane in the air extremely nose heavy. The plane would fall at anything less than about 60mph (no kidding) and loops, inverted.... the fun stuff was impossible. The landing didn't go so well either.
I said just an idea, because once you have your plane flying straight and level (which you do) take a quick look at the elevator and rudder to see if neutral, or where the plane flies straight, is actual 1/4" down elevator, 1/4: left rudder etc. Some big trim problem.
Ok, that makes sense. I will check, but the cg is right where the fuse markings say it is supposed to be. I have no manual for the plane so I have no measurement. It is about 1/3 back from the leading edge, and just behind the main spar. When it was given to me, it was very tail heavy and it required an entire package of great planes lead bolted to the motor mount to balance. That is why it is so heavy. I might try removing the non balsa dowel rods used as control rods, and replace them with a small metal rod.