« Archives in January, 2007

More trim tab stuff

1.5 hours.
This could have gone badly. But it didn’t. First thing that happened was that I noticed a mistake. I countersunk the bottom of the left elevator trim tab spar and dimpled the top. It’s supposed to be the other way round, because the trim tab hinge is supposed to lie flat against the inner top edge of the spar and the dimpled skin is supposed to go into the countersunk holes on the outer top. After posting a question on VAF and getting no response in the short time I waited for one (patience has never been one of my stronger qualities), I decided to match-drill the hinge and dimple it. The only answer was from an older post about flap hinges, and supposedly, countersinking, doubling, and dimpling are all acceptable options. The only drawback of dimpling the hinge is that it distorts the metal and makes it harder to get the hinge pin through the eyes. Mine became a little bit stiff, but not that much, and the hinge travels freely. I’m going to call it OK. I still have to trim off the excess hinge to bring it into line with the inboard edge of the elevator and trim tab, but that’s a no brainer. Once I get that together, I have to do the trim access plate and the trim tab horn, and we’ll be ready for deburr/dimple/prime on all the left elevator bits. Right elevator skin needs to be deburred/dimpled, and all the skeleton parts are ready for prime.

Picking up the tab.

4 hours.
The whole bent-tab design on the elevators and the trim tabs of the RV series is frakking retarded. There. Got that off my chest. The elevator tab turned out messy. The inner tab looked like it got worked over by somebody looking to collect a debt or extract information. Unfortunately, that wasn’t the case, it was just me. I had it clamped in the blocks, to make the bend, but during some light work with the rivet gun, it slipped and I bashed the hell out of it. The outer (upper) tab went a lot better, and looked fairly decent. In my attempts to get the lower tab looking a little better, I managed to crack the metal near the relief notch on one end. No big deal, cut the cracked part out (crack was less than 1/8″), round it out, deburr. As soon as I got that done, I bent the upper one (the good one) out just a bit so I could get to something and it cracked too. So I built a riblet. I probably could have built it out of a thinner material, but the scrap available was the same gauge as the root rib and spars. The good thing about that was that I could machine countersink it to accept dimpled skins and not have to worry about getting a dimpler inside the riblet. I like the riblet, but it cost me a couple of hours.
After that, I got going on the trim tab itself. Bending the tabs on that is much easier. And like someone said on VAF, it’s a lot easer to do any tab-bending before you bend the skins in the brake. It’s probably easier to do it before you rivet the stiffeners on, too. But I got that done, then drilled in the trim-tab hinge to the trim tab spar, and that’s where I’m at right now.