Wed Oct 24 2007

Left aileron tweaking

These three photos are actually from late on Tuesday night. This evening I continued match drilling the left aileron. I'm fighting a cold so I'm not too motivated. All I got done was match drilling the nose ribs to the spar and clecoed the assembly together.

Somehow I ended up with this ski slope effect on the trailing edge. The right aileron has this slightly, but not as severe. It seems like the prepunching in the rib flanges aren't lined up with the prepunching in the skin. I'll send Van's an e-mail asking them about it.

The opposite end of the aileron doesn't seem as bad.

This evening I did some more investigation. Van's responded and basically said "it's OK", but I won't be happy with that. Taking the clecos out of one side of the worst skislope rib allowed the skin to relax. Here you can see that the prepunching is mismatched by half a hole.

With those clecos removed, I wanted to see if my aileron had any twist to it. I don't trust that this workbench is flat, so I used the hanging fishing line method at each end of the aileron to check for twist. I had to arrange the aileron in this precarious hanging-over-the-edge position. Yikes!

Here on the outboard end of the left aileron, you can see that the fishing line is nearly perfectly parallel with the top surface.

...but down at the other end, the line isn't parallel. It looks like I've got about 1/8 inch of twist. to get that out???

After much tweaking, I'm pretty sure I've got the twist out. Here on the outboard end, the fishing line is nice and parallel to the skin surface.

...same at the inboard end. How did I do it you ask? I elongated the holes of the top surface of the trailing edge skin relative to the spar. I filed about 5 or 6 of them with a needle file so they were about .010 to .015 oblong, then clecoed the skins back down to the spar. This allowed the top surface of the skin to shift sideways just enough to take the twist out. After that all that was required was to match drill all the remaining holes.

Here you can see one of the holes before I match drilled. The trailing edge skin is shifted about .010 or .015 to the left of the leading edge skin and the spar.

I wrote myself a note so I wouldn't forget when it came time to dimple the trailing edge skin.

With regard to the skislope effect, I think I'm just gonna order a new rib from Van's that doesn't have the prepunched holes. That should work fine. Perhaps tomorrow after I finish match drilling this aileron, I'll go through the same exercise with the right aileron to make sure there's no twist there either.