ORIGINAL: Jim Woodward
You may have already figured this out, but for those of us who are "rudder-cable-hole-exit-location-impared", an easy way is to think of it like this. The rudder horn hole-to-hole width is 2-5/16". If I match the rudder servo horn dimension to this 2-5/16" width, and mount the servo on the center of the fuselage, then the cable should exit the fuselage where it too is 2-5/16" in width. To find this, just glue a 2-5/16" piece of balsa to a long stringer, and stick it down the fuselage until it rubs on both sides. This at least takes care of the "x" dimension.
Jim W.
Jim,
Another way that I have found a bit easier is to use a woodworkers caliper and adjust it to match the rudder horn hole-to-hole distance. Slide this up the rear fuse until it touches. To get the vertical alignment, line up a straight edge on the outside of the fuse from the rudder horn to the servo horn location and lightly mark a line (erasable pen) at the caliper point.....No fusing with long sticks down the fuse. Also remeber that this hole-to-hole dimension gives you the forward most point of the cable slot...because rudder deflection will decrease the cable separation the slot will need to be cut from this mark aft.
I've played around with making a rudder "pulley" system for large IMAC birds......These were custom machined, but I have heard people using available pylon racer wheels with great success. I may try this type of set-up on my Impact......nice thing with these is cable is always tight and no cosine shrinking in the cable separation, so the exit slot can indeed be very small.
-Erik
P.S. I was born and raised in Lancaster CA... I was president of the AV Tailwinds back in 1982. Flew mostly at the lake-bed back then before MMM came along. Flew EU-1A's with Jerry B. back then in the "rocket pattern days"....say hi to the gang for me. (Although I think I read in the K-Factor that you are now in Florida?)