Thursday, April 22, 2010

Back on track

I was able to go visit the almost-done RV-12 to check the fit of the semi-circular wing spar tab receptacles today. Normally it would be somewhat of a burden to ask a guy to remove the wings from a plane that is nearly complete and ready for its airworthiness inspection but in this case one of them had to come off anyway. It's kind of a sad story, really. He and a friend had moved the plane to his hangar and were reassembling it when a gust of wind grabbed the right wing off of the trailer and threw it against some immovable objects. The net result is that he will have to strip off and replace the skins of the damaged wing, along with at least one of the inner ribs.

The only thing I could think to say was "at least it wasn't painted yet."

I'm not particularly adept in situations of personal loss.

Thankfully I did have sufficient tact to refrain from pointing out the benefits to me from his misfortune. So there is that.

It was interesting to be involved in removing a wing, and I have to say that it is every bit as easy as advertised. Remove the pins, pull the wing out, and ensure there is someone on the root end to catch it as it comes out of the plane. Not necessarily in that order. In fact, the third step works better as the second step. Just, you know, for future reference.

With the wing off, I test fitted the semi-circular wing spar tab receptacle to the aft wing spar tab. It fit like a glove. Now, I could have stopped there and simply assumed that the left would fit as well, but... I'm losing enough sleep over this thing already and don't need to add new chapters to the horror novel that is on my current stuff-to-worry-about-at-three-AM shelf. And really, the wing would only need to come out a few inches - what's the big deal?

Well, it's not a herculean effort by any stretch and I'm sure it gets easier with practice, but it is inarguably harder to put the wing back in than it is to take it out. Lesson learned. Naturally after all that effort, the left receptacle fit just as well as the right. Neither will need any filing or trimming at all.

Oh, and I got to sit inside a nearly-finished RV-12 too. I liked it! It's wider and seemed to have a more comfortable seating position than the RV-6. The visibility is great and the control stick falls readily to hand. I will have to adjust to the new throttle location, but that's a nit.

Now that I'm sure the receptacles are ready to be installed I can finish up the aft bulkhead on the center section. That's a simple matter of riveting the receptacles into place with a few handfuls of LP4-5 blind rivets. Interestingly, this is the first time the manual has asked that all of the rivets be put in place before driving any of them; the work of holding the parts together and in alignment is normally left to the venerable clecos.

Bada, bing, and boom. All done.

In what appears to be a pretty random ordering of steps, I then was tasked with assembling a pair of aileron hinge brackets. The four parts used to make two brackets are completely identical, a situation that I have learned requires caution. In this case, it would be very easy to countersink all four of the bracket sides, but only two of the parts need it. The other two sides will have the non-flush shop head on them. The plans clearly state this, of course, but I still caught myself thinking that I'd be countersinking both sides of the brackets. Taking a breath to think things through saved me from that. As a reminder, I marked the holes that I would countersink.

Once the parts were clecoed together, I saw a potential problem: there was a notable gap at the ends of the brackets where the bearings were inserted. I put a clamp on one of them and it closed the gap down, so the problem wasn't a mis-fit of the bearings. I figured I'd just leave the clamp on while I did the riveting to keep the parts tight.

Which worked, more or less. Now there's a gap at the other end. I suspect that I've only managed to kick that can down the road. There's nothing I can do about it now. I'll just have to burn that bridge when I get to it.

With that diversion out of the way, it was back to getting the aft bulkhead attached. This was another step that had a potential pitfall in it that I successfully circumnavigated. At first glance, it would appear that all six of the ribs get riveted directly to the aft bulkhead, but a closer reading shows that the first step only involves the two outer most ribs on both sides. The innermost ribs get riveted on the next step after having a couple more little ribs put in place. I went ahead and clecoed those little riblets into place so I so I wouldn't forget and rivet the inner ribs prematurely.

It turned out to be a better position for the riveting over on the saw horses rather than on the work bench. I'm going to miss being able to move this thing around easily when it gets bigger.

As long as I was riveting, I went ahead and riveted the riblets too. Those rivets were down in the flanges and pretty hard to get at, but the articulated rivet puller made it possible. This seemed like a great time to quit for the night. Have you noticed the way that I'm humped over in every picture of myself that I put up on this blog? It's not because I'm bending over the work; I think my back is taking a permanent set from all of this riveting and stuff.

It doesn't look like much, does it? Just to give you an idea of where this will eventually end up:

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