Just like a butterfly

Or more fittingly, I suppose, a schmetterling.

Right before your eyes and without the privacy afforded a caterpillar by a cocoon, the Horizontal Stab box is transmogrifying into the Horizontal Stab skeleton.

Well, it will.

Soon.

But first, I had to fabricate the inner pieces of the hinges that the stab will pivot on. And by "fabricate," an overly lofty sounding word, I mean "make." And by "make," which in this case is also overly aggrandizing considering the nature of the actual work involved, I mean cut a little tube of aluminum into smaller tubes of aluminum. 21/32" long tubes, in fact. With a tolerance in size of plus 1/32" and minus 0. Zero. None. Nada. (As is "nada smidgen shorter." Oh, you thought I knew Spanish? Nope.)

You'd think my first step would be to find a ruler graduated in 1/32" increments. And, well, you'd be right. But I haven't got one. So my second step was to pull out my precision calipers. Which quite naturally led to the third step: go back upstairs and get a calculator to find the decimal equivalent of 21/32. Which, as I'm sure most of you already knew, is .65625 inches. My calipers are only useful down to .656, though.

It would have to do.



Cutting the tube with a hacksaw was easy enough, but doing it well was a completely different story. The saw leaves a rough edge that has to be deburred, and the deburring is not easy. In one case, I deburred a piece to below the minus zero tolerance. You can pick it out easily enough:



You can also see that the remaining pieces will still need to be cleaned up a bit. I'm letting them sit over night while I think of a way to get them nice and flush in the ends without chasing them down to below the allowable size. I'm thinking it's going to be something not involving the Scotch-Brite wheel. The great thing about the wheel is that it removes a lot of metal quickly. Of course, the bad thing about the wheel is that it removes a lot of metal quickly. It's a lot like working with fiberglass that way.

With that part back-burnered, it was time to move onto something more gratifying. Something like a little helicopter flying:



Unable to put it off any longer, I started attaching the parts that would hold the ribs that in turn would support the skin of the stabilator. This is another of those situations where Van's made sure that the parts could only (correctly) go in one way:



If you tried to install them incorrectly, the holes in the flange wouldn't match up with the holes in the spar box. That's what drills are made for if you're the type to insist on having things your own way, but I found it easier to just turn the part over so it would fit:



Those little parts will have the ribs aft of the spar box riveted to them. Eventually. Not tonight. For tonight, I was concentrating on the stuff forward of the spar box. That involved the preparation of eight ribs. The preparation included the normal deburring, plus some fluting to straighten them out and some grinding away of material on their noses. Just as with the vertical stab, the noses of the ribs are going to have to nestle into the bend at the leading edge of the skin. To allow for that, some of the material that got pushed forward of the leading edge of the rib when the flanges were bent needed to be ground away.

This is a before and after picture:



Grinding that much material off of eight ribs takes a toll on the relatively spendy Scotch-Brite wheel. After enough time watching the wheel shrink, I started to feel like it was billing me by the minute! Here's the spar box, half way to becoming the horizontal spar skeleton:



I hope to get to the back half tomorrow, but I'm on vacation. It seems like that would be a great time to get airplane work done, but my time seems to be getting soaked up honoring all of the "I'll do it when I'm on vacation" commitments that I've been piling up for three or four months. Plus there's RV-6 cowl work to do, although that's going to be on hold while I wait for a few little bags of appropriately sized rivets to arrive from Van's.

Spar box done

I spent most of the day working on the RV-6 cowl. The weather today was simply gorgeous and here I am without a functional airplane to fly in it. Time to get it fixed! But that's a story for another blog.

While the epoxy that I had injected into the holes from the drilled out cowl rivets set, I went back to work on the RV-12. There wasn't much to do, really: a total of 24 rivets needed to be pulled to seal up the spar box. Being rather the over-achiever at times, I pulled 25. Oops! You can see the 25th rivet here:



It's the flush blind rivet at the top that doesn't have a '120' written next to it. That means that the hole wasn't countersunk to 120 degrees. In fact, it wasn't countersunk at all, for the very obvious reason that no rivet should have gone in that hole. Yet, anyway.

So, my first attempt to drill out a blind rivet. It's actually quite easy, but it did have the unfortunate side effect of bending down the flange that it had been riveted into. You know, a flange inside of the spar box that I had just riveted shut. And to add insult to injury, it is very likely that I will now be one rivet short in my inventory, a fact that almost certainly become painfully apparent at an extremely inconvenient time. That's just the way these things go...

Rather than drill out all of the rivets, I found that I could reach up inside one of the lightening holes in the spar box with a long, thin rod and bend the flange back into place. Hopefully I got it straight enough such that whatever rivet ends up inhabiting that hole will go through it rather than just push it out of the way. These are the loose threads from which the fabric of sleepless nights is woven when building an airplane. I'm virtually guaranteed to wake up in the demon filled hours of the night worried about that flange, with the only way of getting back to sleep being to go downstairs and look at it again to assuage my doubts that I got it bent back where it belongs.

Here's the ostensibly completed and equally restless spar box recumbent on pair of borrowed saw horses, no doubt wondering if my arthroscopic surgery has obviated the need for a far more invasive procedure:



Only time will tell. And I'm likely to have plenty of it: I got a letter from Van's yesterday telling me that I won't be seeing the fuse kit until at least Feb 1, 2010.

Hey, remember I'm a part-timer!

It's not that I haven't been working on the plane; I have. I haven't written about it because I've only been able to squeeze in a little rivet squeezing and hammer a little rivet driving into my schedule this week.

On Tuesday I hosted a shop visit with Kyle and Don, a father and son pair that are contemplating building an RV-12 to replace their Cessna 152. I think that's a terrific idea, but I'm clearly biased in favor of the more sprightly and capably Van's airplane. I was able to squeeze in the rivets that hold the nutplates on the fore and aft spars of the spar box. It went swimmingly, but I will pass along a tip: there are two different rivet sizes to be used, depending on which nutplates are being riveted. I used the wrong length on one of the nutplates before realizing my error.

The shop visit was fun. They both had a lot of the same questions that I had when I was considering the kit and I think I was able to answer most of them accurately based on the smattering of experience I've gathered so far. There were a few times when I had to caveat my answers with a cautious "as far as I know" or "at least with regards to the tail," of course. As with any RV, there were a lot of questions about riveting, and a lot about the quality of the plans/instructions. Riveting: well, blind rivets are super easy. Squeezed rivets are too, for the most part, although some can be hard to reach with the squeezer. Driven rivets? Well...

Last night I was ready to rivet the counter balance brackets onto the spars. Those require the thicker #4 rivets and are therefore a little harder to squeeze. I was going to squeeze them anyway, but the yoke on the big squeezer wouldn't clear the flange of the spar. I had to load the two spars into the little Subaru and take them up to the hangar to drive the rivets with my rivet gun. I brought co-worker Egg along to hold the spars in place while I devoted my two-per-customer hands to the riveting. I'm still quite the novice at driving rivets and it showed. Five or six needed to be drilled out and re-done because I let the rivet set (the part attached to the rivet gun, as opposed to the bucking bar on the other side of the rivet) slip off the rivet head and completely mess it up. I also think I had the air pressure a bit too high as a number of the rivets were slightly over-driven. After I got back in the groove, though, it went as well as could be expected considering that I hadn't had a particularly pleasant day at work (nor on either of the commutes, for that matter) and that was being reflected in my hands. They just didn't want to behave themselves.

With the counter balance brackets in place, it's time to do the final riveting on the spar box. Once that's done, the ribs get attached and the skin goes on. That will take a few days as the parts for the broken RV-6 have arrived and I need to devote some attention to that. I'm off work all next week, so there should be a whole lot of progress to report on both fronts.