Control Arm Drill Guide...

For those of you who DREAD drilling those holes in hard points on control surfaces, I share your pain.   Took me years to get frustrated enough to finally sit down and solve it.

Here are pics of a fixture you can make, and some suggestions on how to use it.  I already have on two airplanes, and can PROMISE it 'works'.  You will be surprised.

Shown above is the assembled jig.  Parts are 1/8" ply plate, 3/8" sq. hardwood.	A brass tube is glued into a groove on the adjustable vertical block.  Either use a needle, or 3/32" music wire as a marking tool..	This view shows the 4-40 screw that tightens the guide into the appropriate position.  Keep the plate 90* to the hinge line, and measure your setback (distance from hinge line) to repeat on other elevator/aileron, whatever.	Once in position, wrap a paper towel, or cloth, around the control surface, and clamp the ply plate FLAT against the control surface.  Then, drill carefully through the brass tube all the way through the control surface hardpoint.
To ensure VERTICAL perpendicularity to the flying surface chordline, rest a large carpenters' square on the anti rotation dowels, and sight from the outboard tip, even with the hinge line.  In this picture, parallax angle makes it look slightly crooked, because I held the camera AFT of the hinge line..	This is what you end up with.  Move the clamp to the second control point location, clamp in position with the same SETBACK dimension from the hinge line, and mark/drill as before.  You will end up with PERFECTLY 90* to chordline drilled holes for those long control screws.