VS rivet setting - common problem and my solution

I wanted to take a moment to elaborate on what appears to be a very common problem when riveting the rear spar, spar doubler, and the center spar hinge together, add then get to the point where you are trying to attach the skin on both sides to the rear spar in that same area. Many run into a probem trying to figure out how to set the 4 rivets of the skin to the rear spar where they are in alignment with the hinge plates of the center rudder hinge. I will try to get a picture in here that more clearly demonstrates the problem, but for now th three pics that I do have will have to suffice.

The top pic shows the center hinge on the rear spar at the top of the pic. The bottom pic shows the relationship of the rivets attaching the skin to the location of the rear spar doubler and the corresponding round headed AN470 rivets that were used to attach the spar stiffener to the rear spar. Note the rivet shaft hanging down from the top skin and going through the rear spar flange before the rivet is set. Also note how the round rivet head attaching the stiffener to the rear spar is directly in the way of where the bucking bar or rivet set must be inserted to set that rivet. This will give you at least an idea of how certain things can get in the way of a bucking bar or squeezer yoke, making the setting of some of the rivets that attach the slin to the spar a bit of a challenge. Now use your imagination to add the center hinge plate the top of the rear spar stiffener. This adds at least another 1/16th of an inch, plus the additional width of the AN470 rivets attaching the hinge to the rear spar. Basically what is happening is that the amount of space to insert a bucking bar so that it will cover the entire shaft of the rivet attaching the skin to the spar is being reduced as each "layer" of thickness from each different part is added to the "girth" of the rear spar.

Most folks are trying to insert a squeezer yoke in there to squeeze the rivet, and there is too much of gap between the face of the rivet set and shaft of the end of the rivet. The end result is that only about half of the rivet shaft is able to be set, and you end up with a deformed rivet that has to be drilled out. Their solution is to grind down the end of the squeezer yoke. Not liking that solution very much, I ended up discussing this with Vans, and they promptly asked me if I had a bucking bar with an angled face on it that should be able to reach in there and provide enough area for the rivet to be set properly.

I told them that I had two different tungsten bucking bars, each with an angled face on one end. Refer to the second pic and you will see one of them next to the rivet gun. I have affectionately named each of these bucking bars Fat Man and Little Boy, after the two atomic bombs that were dropped on Japan at the end of WWII. The one in the pic is Fat Man. It is short and fat, and allows it to fit in between the flanges of rear spars and other small areas fairly easily, where your hand can still be placed relatively close to the work. Little Boy is longer but skinnier, and can fit into other areas where Fat Man cannot.

Anyway, the important thing to note is the angled face on one end of the bar. It comes to a point, which reduces the surface area, so that it can be inserted in such a way that avoids the protruding hinge plate and round rivet heads that attach it to the rear spar. In fact, it allows you to bypass all the things that would get in the way if you try ot use the flat side of the bucking bar or an unmodified yoke. I was able to use this bucking bar with the rivet gun to set each of the 4 skin-attach rivets without any further problems. Just make sure you tape up the bar to keep it from marring the spar flange or the hinge plate, and you will be fine. This approach beats the heck out of grinding down your expensive squeezer yokes.