JRDualElev

1. Control takeoff on elevators. Clevis attachment point should be the same distance from the control surface, AND the same distance (front to back) from the hinge line with the elevator neutral. The idea here is that the leverage points for both elevators will be identical. The MOST critical is the alignment to hinge line...work on that, if need be, and try to get them both the same. The distance of the clevis hole from the control surface can be dealt with by the Travel Adjustment, mostly.

2. Servo Mounting - (again, this is "new plane"; use as appropriate) - It is very important that all the geometry of the mechanical installation be as close to symmetrical as you can make it. Optimum - the very best setup - is to have the servo output shafts the same distance forward of the hinge line on both sides, and the same distance "down" from the centerline of the stabilizer (chordline). Of course, the servos themselves should be mounted long side parallel to the stab chordline.

Did all of that make sense? The idea is to ensure, as much as you can, that BOTH halves are "mechanically" identical. At least THEN, you'll only be dealing with electronic variation of the two servos. I'm making an assumption that you're using some pretty good servos, but here's the thing...you have to be able to get their "neutral" mechanical point the same on both sides.

3. Using a small triangle piece of ply that has a 90 degree reference on it, find, choose, swap, exchange the servo OUTPUT arms until you find the one that is closest to perfectly perpendicular on that servo. Mark it "L" or "R", but MARK it.... Now, ON THAT channel, adjust the individual Function 15, Sub Trim, until the arm is perpendicular to the servo case (assuming everything is like supposed to be in #2 above). Then do the SAME thing on the "other side", again setting the SUB TRIM function to establish the electronic "zero" at perpendicular to the servo case. DON'T touch SUB TRIM again.....

If #2 above, and this step, are done accurately, your pushrod lengths will be identical. That's one way to verify the accuracy of all this 'building stuff' that affects the dual elevator setup.

4. Make up pushrods that are slop-free, and that are the same. I use CF rods, and I usually will measure one side, allow for the threaded rod and clevis/ball link setup, then cut both pieces to the same length. I have found building them in "pairs" assures a better setup overall.

5. Attach the pushrods to servo and elevator. Remember the control arm geometry from # 2 ? This is where those steps become important. ANY angular variation from perpendicular, or distance variation from hinge line from one elevator half to the other, will cause you headaches. When you connect everything up, elevators mechanically centered, adjust the pushrod clevis', radio on, until BOTH elevator halves are aligned at neutral. DO NOT go back and tweak Function 15, Sub Trim, UNLESS you've tried everything else. Elevators aligned at NEUTRAL is a "must have"....

6. Now set Function 12, Travel Adjust, for one half by measuring the movement of the elevator when you move the stick. Use some reference point for this measurement that you can accurately duplicate on the other half. Also very important. Write these numbers / measures down for the first half. Check the other half. If not the same, what I do is adjust the SECOND servo. It helps my weak brain to know that I've only screwed with one side if things have to be redone. When you have BOTH of the elevator halves moving the same amount with Function 12, Travel, NOW you'll change the rest of the "flying characteristics" using the Function 14, Trace Rate. Don't forget function 13, Expo, and DO NOT forget to loctite everything.

7. Use Function 14, Trace Rate, to set the flying feel of the elevator. And if you have to exchange servos for some reason...particularly a gear set change, recheck the mechanical "zeroes" before you start programming. I've messed up my share of dual-elev setups by using too much programming.

If you've stayed with me this far, I think you've seen that the REAL "secret" of a uniform elevator setup is the mechanical stuff surrounding the servo installation, as well as the control arm takeoff points, distances, and geometry.