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Empennage bottom skin rivets

Anyone have any tips for the bottom skin rivets? I’m getting a 60% failure rate, where before I typically would get one bad rivet every 30-40 or so. I manage to make the stretch with one hand below and the other inside with the bucking bar, but so many rivets are not seating and sticking partially out! My “good” rivets here would be considered “acceptable” elsewhere as the tiniest bit still catches a fingernail.

Please give me some tips!!
 

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If you are talking about the bottom tail rivets in general, I backriveted all of them, laying the tail on a hard surface with a back rivet bucking bar under it. I used slices of plywood to position the tail so it sat flat on the bucking bar.

For the two rows of rivets that connect the tail to the fuselage, I built up a tower of scrap wood to the height of the bottom of the fuselage (it was sitting on dollies). Using a couple of wedge shaped carpenter's shims, I was able to adjust the angle of the top of the pile to the angle of the tailcone. Then I slid in a bucking bar between the shims and the rivets taped to the tail. Lifting the tail a little bit and giving the pile a hard shove resulted in a lot of the plane's weight sitting on the pile and bucking bar. Then I was able to backrivet from the inside. Hit rate wasn't perfect on the rivets, but this worked 8 or 9 times out of 10.
 
Should I rivet the sides support rails to the side skins first and then take off most of the bottom clecos and back rivet as you suggest at that point? Thanks for the help

8 or 9 out of 10 would be amazing at this point haha!
 
Yeah I was hoping no one would say that, no willing helpers here. Hopefully I don’t have to stall until family comes over. Urgh I need COVID to go away.
 
Have you tried using a small piece of rubber hose on the tail of the rivet to help pull the joint tight? Learned that trick on VAF and use it quite often now!
 
I had a bit of an unfair advantage on the rivets along the curve where the tail and fuselage come together. Since I am putting in a BRS parachute, I have a hole in the right side fuselage that is approximately opposite the baggage door. I didn't need to reach 4 feet around the skin for the curve and side rivets - I just went through the parachute egress hole the same way I did for the baggage door side. So, giant tower o' wood and shims for the flat bottom joint rivets, reaching in on either side for the sides and curve.
 
I may be unclear regarding what part you are actually talking about. For the hundreds of rivets along the stringers and longerons and ribs that connect the skin to the entire tailcone, I back riveted 99% of them. For the bottom, lay it flat on something and backrivet. For the sides, I rocked the tailcone 90 degrees and back riveted. Even for the curves, strategically placed blocks of wood and styrofoam let me brace the tailcone at just the right angle to back rivet. Every different position required reorganizing the blocks of plywood and foam so that I was always keeping the factory heads flat and flush, but once it was set up, backriveting was the way to go. With a long bucking bar, I could bang out blocks of 10 at a time.

8 or 9 out of 10 was my score for the tail-fuselage joint using the pile of wood. For the backrivets for the entire tailcone, I was running more like 49 out of 50. As long as you triple check that the factory head is centered on the bucking bar and the metal is tight and flat, it is really hard to screw up a back rivet.
 
Thanks I am going to try this method out tomorrow, it sounds very promising. I gave up for today and needed a break anyway.
 
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