Problem: find a simple solution to drilling the trailing edge. I was looking at the cross-section of the R-916-1 trailing edge and concluded that a scrap piece would make a great drill guide because of its shape. It has a nice, well-defined grove in the back with the vertex going through the chord line. The requirement is to have the drill axis perpendicular to the trailing-edge chord line. Because the trailing edge is sharp and because of the small angles, it works very well to clamp a scrap piece to the drill table and to slide the sharp edge of the trailing edge to be drilled into the groove of a scrap piece that is clamped to the table. It works because the groove sits, approximately, the same distance above the drill table whether one side of the trailing edge is flat on the table or tilted with the chord line parallel to the table (the geometrically correct configuration). I am happy with the results I got. Photos:
Drill guide is clamped to the drill press table. To drill, the trailing edge slides into the guide with the sharp edge nested into the groove on the thick side of the scrap (the drill guide).
Get a firm clamp to the drill table.
The countersinks have an asymmetrical shape on both sides because they are not perpendicular to the surface. They are perpendicular to the chord line.
A rivet, sitting upside-down on the table and going thru one of the holes is aligned correctly.