Prep for turtledeck riveting

First up this morning, before heading over for the usual Sunday morning coffee across the runway, I got Josie’s help with dimpling the rest of the turtledeck skin. There weren’t a ton of holes to take care of here, and we were doing quite well until one, where I had her reposition a bit and then didn’t double-check I was still aligned with the dimple die. Fortunately I was only slightly off, so instead of making the traditional figure-eight double hole, I just slightly elongated it. For the moment, I just hammered it flat again; for one thing, I wasn’t 100% sure how I’d approach the fix, and for another, the elongated hole meant that trying to redimple it again immediately would be tough, since it was hard to tell which end was the “right” one. Something to let my mind work on in the background.

Next, while it was still cool and I had a second set of hands, I reinstalled the transponder and ADS-B antennas, using caulk on the outside to seal them and the permanent locknuts on the inside. Then it was time for coffee, plus working on the museum’s Helio Courier. (almost got the annual done so we can fly her!)

Back at work this afternoon, I had my plan for fixing that elongated hole. First up was going to be correcting the dimple; from there, I could evaluate what other action was needed. To fix the dimple, I minimally clecoed the skin in place on the fuselage; this way, I could use the matching hole in the upper bulkhead to properly locate the dimple. The plan was to use the pop-rivet dimple die in the assembly hole, even though I knew it wouldn’t make a full dimple. Then I could remove the skin and use the shallow dimple to properly locate the final thing. Not only did this work out quite well, but the final hole was only slightly elongated by the time I was done. What I’ll do when I reinstall the skin for riveting is drill the hole up to #30 and use a NAS1097 rivet here; that should give me a nice quality result overall.

Finally, I needed some work platforms to go in the tail. The lower skin is pretty flimsy, and there are also the bulkheads sticking up – basically, there’s no way to safely lay back in the tail without some kind of provisions. Some folks stuff foam between the bulkheads, but the plans include dimensions for fabricating plywood back boards to go in the bays and rest on the longerons, which should be much better for load bearing than the skins or bulkheads.

Originally I’d considered borrowing the boards from my neighbor – he bought an -8 project and it came with the boards already made – but after looking at my setup and thinking it through I decided to make my own, for a couple reasons. For one, this won’t be the last time I need to crawl back in the tail, so these are probably things I should just have on hand. Second, because of the way I have the wiring routed with the rear avionics shelf, the plan-specified boards would need some modifications anyway.

I further modified the plans a bit – while they called for a single large board in each bay, I chose to make two boards for the aft bay. The main reason was that this worked well with the scrap MDF I had lying around, but I think this will also make it easier to get the boards and and out if I need them down the road for maintenance. For the forward bay, I made what was intended to be the forward half board, but it ended up fitting further back than I expected. I’m going to initially try things with just these three boards, and see if the gap bothers me – if so, I can always cut one more narrow board to go in the space where the avionics shelf normally is.

We’re going to take advantage of the holiday tomorrow and see if we can make some good progress on riveting. I’m not sure if we’ll get through it all before it gets obnoxiously hot in the hangar, but we’ll try. The plan is for me to be the lucky soul wriggling back into the cave and bucking while Josie does the shooting from outside. I’m hoping I can get a fan rigged up somehow to blow air through the tail while I’m in there, otherwise it’s going to be pretty miserable. Well, I’m pretty sure it’ll be miserable no matter what, but at least a fan would reduce the misery a bit.

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