Is precession that the excess tip weight is causing inertia to make the outboard tip to want to continue in a straight line causing the yaw or roll? cuz that is what I thought so I removed tip weight and it did improve.... I will seal the hinge lines...can't believe I have not already done so..that helped a lot on my old bucaneer. It's been 17 years since i last flew and have actually forgotten some of the "rules" that I used to know so well. This is the hardest plane I've ever had to trim. It is my second forerunner and the first was just awesome..adjust rake, add some tail weight and boom..there it was...point and shoot. This one sat in my garage for 17 years in the heat and cold of Texas....maybe I've got a warp? there is 0 rudder offset and 0 thrust offset...but of course I will double check all of this. I bet a trip to Samuel Park in Garland where I used to fly would yield some good results...met Tom Farmer out there and in one day he took my bucanner from OK to a 3rd in a contest a week later...his first sug was to SEAL THE HINGE LINES! Funny ol' world idn't it?
Without the hinge lines sealed, just about anything could be going on, so do that first and then we will see.
I would suggest forgetting about the precession entirely. I think you can explain it entirely with line tension changes and the leadout position. At some point, there will be a little bit of residual yaw that you can't get rid of, and that might be due to precession.
Think of it this way - assume that the leadouts are too far forward, and in level flight, you have some pressure on the rear side of the leadout guide holes forcing the yaw angle more to the left that it would be otherwise. At a constant speed and line tension, the airplane stays at some steady yaw angle, with the leadouts trying to force the nose in at you, and the aerodynamics (fin/rudder/fuselage and extra drag on the outboard wing) forcing it to the right, and it stops when one torque cancels the other. When you go to maneuver, moving the controls temporarily puts in extra line tension, while at the same time, the airplane slows down, reducing the aerodynamic effects. So now the leadout torque goes up, the aerodynamic torque in the other direction goes down, so it yaws in at you. Once it gets started, it take a while to stop, so you end up crabbed sideways, with the outboard wing forward and the inboard wing back, causing a roll torque to the left.
Other potential causes are things like stab tilt, stab skew WRT the wing, differential flap flexing, fuselage twisting or bending causing stab tilt or skew, on and on.
Taking out tipweight would certainly help this particular issue, and you may end up taking out more later. But taking it out to fix this one issue, in one place, will tend to make everything else worse. You need to get it to work the same way on insides and outsides before you can really tell what you need.
Brett
Topic: trimming a forerunner (Read 1715 times)