Squeezing Double Flush Trailing Edge Rivets

After reading an article in one of these recent RVators about double flush rivets, I decided to take the advice and make a long steel "bucking bar" to use for the trailing edge riveting. I used a peice of 3"x3"X1/4" angle iron about 4 feet long that I had laying around the shop. I used the belt sander to get a nice smooth finish, first with a course grit and then finer grit. I then used a DA sander with a couple finer grits to put a finishing polish on it. The piece of iron I used hapened to have two large holes near either end which worked great to bolt it to the work bench flush with my work surface. Note the 2x6 on the bench is secured to the bench to be used as a stop for the leading edge of the elevator preventing it from slipping during riveting.

I positioned the 2x6 stop so that the trailing edge was flush with the edge of my riveting plate. This photo shows everything lined up and ready to rivet - except the clamps!

OK, now it's ready to go! I began the double flush riveting on the left elevator using the rivet gun and the standard backriveting technique, and had reasonable success. But, I thought it would sure be nice if I could use the pnuematic squeezer on these rivets instead of backriveting. This got me thinking about a flush set that had an appropriate angle to match the AEX wedge used in the trailing edge.
 
 
 

Soooo, I decided to sacrifice my 3/16" AN470 squeezer set and turn it into an angled flush set. I used a benchtop disc sander to grind down one edge and used a piece of AEX T.E. wedge as a guide to make the angle an exact complement of the wedge. I took it down just far enough to remove the cup from the set and have a smooth surface. After a few more passes with finer sandpaper and a little polishing, I had an angled rivet set as seen here.
 
 
 

Realizing that the angled set would have a tendency to fold the rivet over to one side rather than set it flush the way I wanted, I used a standard flush rivet set and pre-squeezed the rivets to the point where one edge was close to flush with the thicker portion of the TE as shown here.
 

I then used the angle set and completed the squeezing to get nice double flush rivet heads. As shown here, I squeezed both the rivet plate and the TE effectively using the rivet plate as the lower rivet set. I used an AN470 squeezer set on the bottom of the rivet plate because I didn't want to squeeze directly with the expensive adjustable set holder in the squeezer. You can see one of the already set rivets through the yoke. Because of the lighting, you can barely see a black reference line I made on the angled set to make sure I could tell where the thickest part of the set was. A firm grip on the squeezer was required when squeezing, as there was a slight tendency for the angled set to want to slide off the rivet. However, this could be easily compensated for with a firm grasp on the pnuematic squeezer. I'm not sure how this technique would work with a manual squeezer, as it might require a third hand to prevent the angled set from slipping off the rivet. A firm back stop (as described above) to prevent the work piece from sliding out from under the angled set is essential.
 
 
 

You can see the results are nicely squeezed double flush rivets. However, you'll notice the slight indentation above the rivet on the left was caused when using the standard flush sets to "pre-squeeze" the rivets and I didn't have the rivet close enough to the edge of the sets.
 
 
 

This is an end view of the right elevator after using the squeezing technique with appropriate clamping along the trailing edge. You can see the E-906 root rib to the left and the end of the AEX wedge in the center. You can see how straight the trailing edge turned out looking down it's length to the workbench.