Seat rib assembly match drilling

Not a lot of work tonight. My main goal for the evening was to finally go back and watch the 2015 webinar on flying into Oshkosh. The webinar was held the same night I was buying a car, so I couldn’t watch it live. But I did manage to get out and work for a little bit while waiting for Josie to finish up her work. First I just scanned through the completed steps for this subassembly, just to get familiar with where I’d left off – which was just after clecoing all the ribs to the rear spar carry-through and just before match drilling all those ribs. So I started off with that but of match drilling. The only interesting part was on the outboard most ribs; these have two 1/8” rivets and one AN3 bolt through the bulkhead. To hold the ribs in place while I drilled, I needed to insert a bolt through the bolt hole, but the holes in the rib flanges were slightly undersize, so I just had to drill those out. No big deal.

Next up, the two bottom skins get fitted to the bottom of the seat rib assembly. One of the skins has a stiffener angle bent into its inboard edge, but this leave the skin dead flat, whereas it needs to be curved to fit against the bottom of the ribs. Kind of hard to see, but here’s a rib assembly on top of the flat skin:

IMG 5974

The skin is bent by simply fluting that stiffener angle until the skin bend is acceptable. I was kind of surprised how heavily I had to flute here. The instructions say to flute every 1.5”, but in retrospect I wonder if it would have been better to put the flutes closer together and maybe not have to flute so aggressively. But then again, there might be a good reason for the spacing. Might as well just follow the instructions.

Next I flipped the seat rib assembly upside down and clecoed the bottom skins in place, then match drilled all the holes:

IMG 5976

And that’s where I left off tonight. Next I get to pull all this apart and do the whole deburring dance, but I think all this stuff will be going back together permanently in the relatively near future.

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