Wednesday, December 23, 2009

Finally! Done with all of that deburring

The tough slog of preparing tail cone skins is finally done! The next step, which I had been deferring because the "full scale" drawing wasn't, finally came to the fore. I decided that it didn't really matter that the "full scale" drawing didn't actually match the scale of the defining object; all that was required was enough fluting on the part to get the slight bend in the four-hole flange to match the barely discernible bend in the "full scale" drawing. That was easy.

So, with a long period of deburring done, it was on to.... another bunch of parts that needed deburring.

Not so bad this time, though, since these parts are small enough to be deburred with the Scotchbrite wheel. That didn't take long, so it was on to the next step: flute the formers. Aw, crap. More fluting. If you remember, the fluting for the ribs in the vertical or horizontal flight surfaces was very easy. Just a few light squeezes flattened everything out nicely. This was not the case with the tail fuselage formers, as you can see here:

In fact, it seemed like the more I fluted, the more "bent" the parts got. I posted the picture above to the Van's Airforce forum and was told that the part appeared to be "over fluted." I was also told that it wasn't super critical to get the part to lay completely flat; the part is pliable enough that I will be able to pull it into alignment with the skins when I go to assemble the cone. Ah, cool! I de-fluted the over-fluted part and pressed on with using the clecos to test fit everything.

In an interesting (but probably meaningless) twist (so to speak), two of the formers are assembled with the right half overlapping the left, but the third former does the opposite:

Oddly enough, it now appears that the "less is more" fluting advice was absolutely correct:

Except, that is, when it isn't. It took quite a large amount of fluting to get that minimal curve into the flange:

There's still a little more deburring to do on those formers, then they will be riveted together. These formers will eventually provide the basis for the tail cone skins to be formed into the "too big for the shop" tail cone. The clock is ticking on the time I have left to work in the comfort of my indoor shop.

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