Monthly Archives: October 2017

Use of paint booth and fabricate custom parts for empennage attach.

Over the last few months, Tal and I have been constructing a paint booth in his workshop.  This was our first run of priming parts in the just finished facility. Here he prepares to apply PPG DP40LF primer to the internal side of his canopy/overhead console, plus my horizontal and vertical stabilizer fiberglass tips.

My tips had to be sanded heavily to get the properly rounded outside profiles to match the elevator tips.  My experience is the fiberglass parts from Van’s are just rough approximations – to get this right requires plenty  of work.  Witness the sanding completely through the gel coat on the left part, this required additional fiberglass/resin layers on the inside to prevent holes.

Next up is prepare and fabricate additional parts on the empennage attach sequence.  The left photo shows a supplimental cover on the rudder bottom.  Not necessary, but it should help deflect some water from entering.  The right photos shows HS attach shims being made.

Attach points for the elevator trim motor and cables are being prepared on the left.  A 3/8″ spotting drill in a clamped vice ensures the attach rivet and bolt holes for the AN6 pivot bolts are correctly aligned to hold the trim bellcrank.

While the horizontal stabilizer is in the jig for work on the fairings, there are also elements of control surface configuration which can be performed.  Checks on elevator up +30 degrees and down -25 degrees confirmed proper range of motion.  Then both sides are set to the “trail” position for drilling the elevator center bearing and elevator push rod bolt holes. To accomplish these tasks two drill guides were fabricated.

The first drill guide protects the center bearing while the pivot points in the elevator horns are configured.  The outer diameter of the guide needs to be reduced just small enough for a snug fit in the inner bearing.  The Delta drill press and Pferd files did the trick.  Once again I am amazed and happy at the incredibly small runout on the drill press!

The left photo shows the drill guide inserted into the center bearing for drilling the right elevator horn.  Next comes the actual drilling operation.  The right elevator is then removed and the same process used on the left elevator. The guide aligned everything perfectly and an AN4 bolt fits cleanly between both elevator horns.

To facilitate proper alignment of the push rod holes, a drill guide is made from a piece of oak sanded to the exact thickness spanning between the elevator horns. Caliper readings were used for initial hand sanding.  Then the piece is aligned and drilled perpendicular to the surfaces with the drill press.

Here the oak drill guide is clamped into place prior to drilling the second hole.  A piece of 3/16″ stainless rod is inserted to align the first hole for the right elevator with the undrilled face of the left elevator.  After drilling is completed, an AN3 bolt passes cleaning through both horns with perfect alignment.

This week was also some final sanding and fitting of the HS tips. The desired 1/8″ gap between the tips and the elevator fairings look good.