I have no Rebel experience so ignore this if someone else pipes up but
if it were mine I'd compare all adjustments in cruise with the same
power setting while always maintaining the ball in the center with
rudder foot pressure. Then an aileron tab or spring to eliminate roll. A
tab is less effective as you slow down (useally preferable) whereas a
spring tends to have more effect as you slow down. Some guys apparently
do use a light spring or bungee on the control stick. When all is
perfect then adjust a rudder tab for no foot pressure. A rudder tab
probably makes more sense than a rudder spring since it sounds like your
machine probably needs more right rudder at higher power and at higher
speed which is common I believe. One advantage of using springs though
is that it is much easier to make a cockpit adjustable spring mechanism
for in-flight adjustments.
There is some discussion of roll with flap application in the archives.
I would think that some roll or stick deflection with flaperon
application is normal and a result of the geometry between the bell
crank and each flaperons being slightly different. One flaperon horn
might be rivetted on a degree or two different for instance resulting in
a slightly different angle to the pushrod. Propwash also is not
symetrical on them and varies with power as well. I'd guess that the
aerodynamics the rotating propwash from adding powere would tend to roll
a flaperon extended rebel to the left a bit compared to a Rebel with
separate flaps. (Prop rotating cw as seen from pilot seat) That said, I
seem to recall it mentioned that the roll with flaperon extension could
be minimised by adjusting the push tube at a flaperon one way while
doing the opposite on the vertical pushrod on the bellcrank if you
wanted to play with it enough.
Ken
Ian Donaldson wrote:
G'day from Australia.
I have lived with a slightly out of trim airplane since I built it, and as
part of my new Years resolutions, I have decided to fix it but I am looking
for some advice as to what the cause of the problems may be, and how to cure
them!
My plane is the standard Rebel fitted with a 100 hp Rotax engine.
Problem #1
In straight and level flight if you take your hands off the controls, the
Rebel wants to do a gentle aileron roll to the left, and when the wing is
brought back up to the level position, it also requires a little right
rudder to keep the ball centered. I have offset the vertical stabiliser as
directed in the manual and have the flaperon set up, not split flaps. My
plane is the standard Rebel fitted with a 100 hp Rotax engine
Problem #2
When I have the plane flying straight and level, if I apply the flaps, the
Rebel wants to do a gentle roll to the right!
None of these out of trim situations seem to make any difference to the
flying characteristics, but I would like to be able to have the plane fly
true, without continually making adjustments.
I do look forward to some help.
Regards and thanks
Ian Donaldson
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