When you have an engine spinning in the conventional direction, it acts like a gyroscope wheel. When you try to corner, the gyroscopic precession tends to make the airplane nose out on inside corners and nose in on outside corners. The Rabe Rudder (named for modeler Al Rabe, who invented it) move the rudder to try to compensate for this effect. In absence of other factors, it would move inboard on inside maneuvers and outboard on outboard maneuvers to try to keep the airplane from yawing due to precession. In practice, they usually end up moving outboard in both turns but a lot more on outsides than insides.
This is a very real effect and actually works *if you can adjust it correctly*. That last is, unfortunately, a big "if" and almost no one can adjust it properly, even following Al's directions to the best of their ability, and they end up causing more problems than they would have had without it. And I don't just mean beginners, Top 5 pilots have proven time and again unable to make it work and wound up with a severe liability for having it.
If you have enough fin and aft fuselage area, you can hold the yaw angles to something reasonable without any sort of active control like a Rabe rudder. That has been my approach and it works plenty well enough if you get everything else (like the rudder offset and leadout position) correct.
Note that the precession also affects the pitch axis, pitching the airplane nose-up in the airplane reference frame all the time, because you are continually yawing it to the right by flying in a circle. That is handled a different way, either with *very slight* downthrust built or shimmed into the engine, *very very slight* positive incidence in the stabilizer (which is what I do), or more commonly, rigging in a bit of down elevator when the flap is neutral.
Again, in many cases, people try this stuff and greatly overdo it, so it is safest to build everything 0-0 alignment and adjust the elevator. My stabilizer, for instance, has about 1/4 degree of positive incidence, which means I put the LE about 1/64" above the 0-0 reference line. That is just enough to know that it is not below the line. Do any more, and you might be cutting it apart later to fix it.
Brett