ORIGINAL: acam37
I have a Ultimate 30 ARF by World Models and have a couple of questions regarding balancing. I know this question has been asked a thousand times but after going through countless posts in the search engine I still don't have a clear answer. First the manual calls for the CG to be 81mm or 3.19" behind the leading edge measured at the center of the top wing. Now once I get this measurement do I draw a straight line out to the wing-tips or do I follow the wing sweep all the way out. If I go 90 deg. out then at the wing-tip it measures approx. 1-7/8".Second, if this is where it balances do you balance the plane upright or inverted.
I am powering this plane with a TT pro .46 which should make it nose heavy if anything. It flew OK last weekend without adding any weight but after extensive crash repairs I feel like NASA is with the Discovery and don't want to take any chances.
On mine, I put dots of masking tape underneath the top wing, on both sides of the center support, at the specified location. Then I reached under the top wing from the back, and located fingertips on each dot of tape. Lift the plane, it should be level.
I set mine up wrong at first, the top wing incidence was positive. The plane would lift off and try to snaproll. After some rework and getting the top wing incidence negative (about 1 degree, or less) it became a whole different plane, and a joy to fly.
Mine will hang on the prop with a Magnum .52 fourstroke, does huge loops, nice four-point rolls, will almost stay in knife-edge across the field. A little too responsive, but I tamed it down with dual rate rudder.
Good luck,
Dave Olson