Sec 8-5 Step 1: Rivet Front Spar, Doubler, and Caps (2). Requires 5 different rivet types/sizes, so needed to follow the diagram explicitly. Again, Main Squeeze works great, although arms get tired after this many 1/8 in rivets.
My woodworking clamps make great stands for the Spar while riveting.
Step 2: Finished the Spar with 9 rivets on top flange at middle in Countersunk holes, and 9 more on bottom flange.
