Today I finished preparing the top skin by back riveting the doubler plate and then bucking the rivets for the rib.
Previously, I had found an issue with the doubler where the edges of the dimples appeared to be cracked. I drilled out the rivets and ordered a new part. This time I took extra care to debur the holes, and dimpled before priming. Using some pre-squeezed rivets made it much easier to back rivet the doubler rivets where they are tight up against the doubler flange. I was happy with how these turned out.
I had been puzzling over how to rivet the rib to the top skin. Ideally I would back rivet these, but the flange on the rib makes access impossible without an offset. I don’t like the idea of offset riveting in general, and back riveting that way sounds like trouble. I eventually found a good solution by clamping the skin to the side of a small table (I used a smooth piece of pine between the desk and skin). This kept everything nice and tight, and allowed my to perfectly buck all of these rivets.
Finished riveting rib to top skin