I haven't changed nothing other than what I said in my first post, just a needle valve change.
I don't have any aluminum pads under the motor, and I haven't taken it out since the time I put the motor in.
Two things - you *did* change something else, you changed fuel. If it was off a little, but you were leaning it out more on 5%, it would tend to obscure the upright/inverted difference. Now with 10% you are running at a different point on the power curve and maybe a slight misalignment shows up more. Also, if you are shimming it for consistent *maneuver* speeds instead of consistent *upright/inverted* speeds, that means that the engine was running differently on insides and outsides before, and since that's a function of the acceleration and the combustion conditions, 10% would be expected to be different. In fact nitro changes were one of the ways we tried to fix or alter that effect. I think you should shim the tank only for upright/inverted level flight - and if it's not the same in the maneuvers, fix that some other way (nitro/plug/bypass cross-section, head clearance and shape, prop diameter and pitch, pipe length, or get a different engine!). Shimming it for the maneuvers and living with the difference in level flight is a good stopgap measure, but not solving the underlying issue.
Additionally, with no pads, there's a good chance the engine has shifted a little since the wood compressed. Did you tighten the engine bolts? If so, you moved the engine a bit. I have no idea what the motor mounts are like in that particular airplane, but I have seen plenty of mounts compressed by 1/32 or more just from the wood getting squeezed. I would also note that the chances it squeezed the same front-to-back is also negligible, so you might have some up or downthrust. Before we all started using motor pads this used to drive people crazy, all the shimming from day to day just to maintain the same thrust angle.
Standard stuff - just fix it and move on.
Brett
Topic: Tank not shimmed right (Read 1181 times)