The Rabe rudder is set up or set up properly will go to the inboard side of the plane on down elevator. This is for regular IC engines or even Electric if flying the counter clockwise prop. Don't know if it makes a difference on the clockwise props.
OK, a quick discussion on gyroscopic precession and our CLPA models. For a model with a counter clockwise turning propeller, viewed from the front, the model will yaw to the left on outside turns and yaw to the right on inside turns. The yawing forces are opposite for a clockwise turning propeller. Now, Al Rabe did not invent gyroscopic precession, but I believe he was the first to be able to trim his airplanes to minimize the undesirable affect that line tension tends to be reduced on outside maneuvers. He devised a system so that right rudder is increased on outside maneuvers and the amount of rudder offset is changed for inside maneuvers. (For Al, he decreases the amount of rudder offset for inside maneuvers by about half or one-third the amount he increases rudder offset for outside maneuvers. The success Al has had over the years with his super semi-scale stunt ships (S
5) cannot be criticized.
Now, to answere a previous question if others have used this. I have incorporated a movable rudder trim capability in my CLPA models since the early 70's after Al introduced the concept. By some measure, I have had some success in competition with these models. I have encountered other modelers who also use this concept in their CLPA models including some at the World Championships. I use a system whereby the rudder control mechanism is completely enclosed and I can program the rudder travel and rate with any given elevator position. I use a different trim process than Al that seems to suit my models. I have found others who also have found the same thing. Al's system works for him because I think he sets sets his model up differently than others that does not need to be discussed here. Whatever it is, it works for him.
Al has written extensively about his system in the publications and on these forums. Alternatives to his linkages have also been published and appear in the forums.
Now, is it really necessary to have a Rabe rudder capability in our CLPA models? Probably not given that most contests have been won and will continue to be are won by models without that capability. My opinion is that it helps and it is definitely worth the effort to have that capability. It is reassuring to have all the line tension I want (which can be trimmed in) during the high outside maneuvers.
There is an interesting experiment that will demonstrate what gyroscopic precession is. Mount a propeller (the heavier the better) on a shaft in a 1/4" or 3/8" drill. Hold the drill in your hands and turn it on. Then, rotate the drill up and down (as in a pitching maneuver). Then reverse the drill rotation and you will feel the opposite affects. It is surprising what those forces are, even at the relative low rotational speeds of the drill compared to our engines/motors.
Keith
Topic: Rabe Rudder question (Read 2487 times)