I figured it would be best to rivet the stabilizer in the jig. We have the jig, so I might as well use it to make sure everything is straight. After making sure every part was ready, the edges were filed and polished, and no tools were left inside the structure, I clecoed the top side of each skin to the frame. Yes, we would start with the top... Why? Because we could leave the bottom skin completely free to swing up, thus allowing me to see exactly where the bucking bar was. Hopefully, then, by the time we got to the bottom skin, which would need to be riveted blind (not with blind Pop rivets, but without seeing the bucking bar), I would know exactly how the bucking bar feels in my fingers when it's on the rivet. Ben's rule of thumb is to always give the upper surfaces of a low-wing airplane the easiest process and the best chance for a pretty finish (less chance to screw up).
The episode went as flawlessly as I could have ever hoped. Ben ran the gun-- a new U.S. Tools 2X that I bought him for Christmas (knowing full well that I would use it most... heeheehee)-- and I did the bucking. Bucking is a new skill for me-- when Ben needed a hand with the 8 or the 10 tail, I always ran the gun. Manipulating a bucking bar is a bit more difficult, but it's not bad when the rivets are small. For this job, I used a small, rectangular iron bar that fit well inside the small area we had to work with.
The top side went together easily. While I worked hard to get every rivet lookng like a little bronze-colored Oreo cookie on the inside, I didn't know how it looked on the outside until we were all done with the top of the first skin. (The correct proportion of squished-shank length to diameter of a correctly-set solid aluminum rivet looks like an Oreo to me...) I was not disappointed! No proud or literally stuck-up rivets, no dents-- everything was as it should be.
The bottom was a bit more difficult because I had to squeeze my little hand up inside to hold the bucking bar against the rivets going into the front spar, and the aft edge of the tough .032 skin cut into my own skin on the bottom of my forearm. (Good thing I had polished the edge before riveting...) Ben wedged a pair of 2x4 chunks in there to keep pressure off my arm, and that helped a lot. I had to make sure the bar was ALWAYS in contact with the rivet to be pounded when the gun was in operation, or else he would severely damage the outer skin. This required some good, basic, very clear communication:
1. I place the bar behind the hole-- I can see the bar through the hole we are about to rivet. Then I move it back 1/4" or so.
2. He places the rivet in the hole and puts the gun up against it.
3. I place the bucking bar against the rivet. He feels me put pressure on it through the gun. If there is any doubt, I tap the rivet lightly or he feathers the trigger to give one or two very light taps with the gun.
4. I brace the bar against the rivet, confident that it's THE ONE, and yell "GO!"
5. He gives a short burst with the rivet gun. With the 2X gun and 40 psi, it took a burst of just under 2 seconds.
We used a mirror and a flashlight to check the ones we couldn't see. Sometimes they needed a little more, adn then just a very short burst with the gun against the bar would finish the rivet off.
We quit after the first half of the stab for the evening. My hand ached from holding the bucking bar up with my fingers. But today we started again and got the entire left-half of the stab finished pretty quickly.
My next job was to remove the stab from the jig and set it on the work bench on some carpet squares, where I could then set the rivets on the ribs and rear spar. I thought the hardest part was going to be the bucking. The first round of rivets went well. Most of the rib rivets and outer rear spar rivets were easy and rather fun to squeeze. But let me tell you, riveting the rest of this thing was not all roses and moonbeams like I planned. The rear sparline was just a smidge too close to the rear doublers. When Van says you "may" move the aft sparline aft of the flange centerline, he means you MUST move it more than 1/16"! Ben showed me how to tweak the pneumatic squeezer and coax it around the shop heads of the doubler rivets to avoid gouging them or the doublers. Eventually I gave up on the pneumatic and squeezed them all by hand. This hurt after a awhile, but gave much nicer results. Some rivets were too close to the elevator hinge brackets to be dimpled or bucked traditionally-- for these, I countersunk the spar to accept the skin dimples, and Ben ground off the squeezer yoke and flat die into an oval shape to fit next to the hinge brackets. They are ugly on the inside, but still nice looking cosmetically where they will be visible. (My polishing dream is still alive...)
Anyway, this was all finished on Saturday, March 5th. Which leads me to the next blog entry...
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