Fuselage - Bulkheads
I had quite a few problems riveting the firewall. I had more than my average number of drill-outs. I seemed to slip off of the rivet with the bucking bar, and munged a lot of rivets. Since this was an assembly that I wanted to make sure was strong, I drilled out all of the bad rivets.
When I was done, I realized that the two top rivets on the center vertical stiffeners needed to be riveted. You need to make sure that you do not put rivets where the firewall recess piece goes, but the top two rivets in the corner do not attach to the recess, so you need to rivet the center stiffeners to the top stiffener. This is a funny joint, which really needs to be clamped (clecos do not do the job), and I messed-up the final rivet.
When I drilled it out, the flush hole was nicely centered, but the backside ended up with an elongated hole. Like I said, these two pieces need to be clamped together. Anyway, I decided to just put a longer rivet in there and pound it down so it would fill the space. It filled-in ok, and I went on to the next section in the manual, but It kept nagging at me, so I decided to fix it with my big honking 3/16" pop-rivets. Apparently, I bought a small quantity of 3/16" AN470 rivets a while back--hey, even better. So, I drill-out the bad rivet and replaced it with the correct fix. Now, I have this big honking round rivet in the center of my firewall to mark my screw-up.