Prepping for the dreaded rudder trailing edge. Riveting the trailing edge is one of the most challenging chores an RV-7A builder faces. It's GOT to be straight, but it can end up wavy and necessitate a trim tab.
Images 1 and 2 show the strip of metal that, while sandwiched between the left and right skins, joins the edge. The skins' rivet holes are dimpled, and will seat into these countersink holes. Image 3 shows two electric cable channels I bought as straight-edge templates for the next phase (I matchdrilled the holes to the skins....you'll see why).
Countersinking the trailing edge strip
Countersinking the trailing edge strip
Electric wire channels for use as straight-edge braces