Today I started out by test fitting a bubble to a door frame, to confirm @alexM's idea that mounting tape will cover most of the holes. Indeed, the bubble contacts the door frame all the way around the perimeter, leaving only the holes in the center bar needing to be welded (plus the holes from the original latch bracket).
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With that knowledge in hand, I took the frames over to the welder's shop and dropped them off with marks showing which holes to weld and which to ignore. I don't have an ETA for their return, but I won't need them for quite awhile.
When I got back, I masked off the brake calipers, cleaned them with acetone and gave them a shot of primer. Later, when that was dry, I painted them to match the rest of the airframe. The only reason I did this is because I had to sand them quite aggressively to remove corrosion pitting, so they looked pretty rough, with only small areas of their original finish intact and mostly bare metal showing.
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I put the new elevator push-pull tube next to the old one, and using the fret marks from the mid-fuselage bushing as a guide, I masked an area on the new tube about 2" longer than those marks, then used acetone to remove primer in that area.
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With the bearing area laid bare, I used the brush-on method to Alumiprep/Alodine that ~6" area. I didn't get any photos of that due to the need to work quickly. With that done, I reversed the masking so that the bare area was covered, sprayed primer up to the tape line (and on a few other spots that got scratched during all this futzing around), and set it aside to dry.
Having discovered that primer is pretty delicate stuff and easy to scratch, once the tube was dry I painted it gloss black like everything else. So, I'm left with a tube that matches the fuselage and other control hardware, but with a bare, Alodined section (which will be greased) where it will slide through the mid-fuselage bushing.
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Some reamers have arrived in the last couple of days, so I went back to the plastic "bearings" in the rudder pedal mounting tubes. I managed to get a good fit in fairly short order, except for one of them that seems to have been warped during welding. In the end the bolts all rotate easily and don't wobble.
For the life of me, I can't fathom why that assembly was designed with that ridiculous 4" plastic bearing. If the tube gets warped a bit during welding (as one of mine did), it bends the plastic bearing along its length, making it extremely difficult to ream to a straight bore. It's a silly PITA that could easily be eliminated by putting a short 3/16" ID Oilite bronze bushing at each end of the pedal mounting tube. Sand the OD of the bushing to fit the tube, assemble, done.
Anyway, the rudder pedal section is ready to reinstall, once I get the front floorboard rehabilitated (rough varnish job and some mold spots).