Shrinking a Hole (cont…)   April 11th, 2007

After leaving the JB Weld alone for a couple of days, I figured it was about as dry as it would get. I first used my Scotch Brite wheel on my air grinder to polish the epoxy so it is flush with the spar flange. This stuff is pretty easy to take off, so I had to go slowly and carefully. I manged to not expose too much more bare aluminum along the way.

Then I used my handy aluminum angle guide to drill a another hole. As you can see in the picture below, I had to cut off some of the angle to allow the 90 degree drill to fit perpendicular to the flange. I got this drill from Brown Tools on a sale. I’ve only used it two or three times, but it’s already paid for itself.

Finally, I countersunk it again, being careful to not go too deep this time.

Doesn’t look as shiny as the original, but it actually looks pretty good, considering….

Now on to more interesting stuff….

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I emailed Van’s aircraft asking if it was OK to just leave the one oversized hole alone, or whether I should try to fix it.

I am not the first guy to screw this up, and they have a method (using doubler plates and aluminum slugs) where you basically drill out the countersink, and then stick a slug in the hole, drill the hole again, and countersink to the right depth. Not something I really wanted to do.

Their response was to go ahead and fix it, but with an ‘alternate method’: Fill the hole with JB Weld and then re-drill the hole and countersink. They made it clear this was acceptable only for one oversized hole. I tried this on a scrap piece of aluminum, and I liked the results, so I’m going to give a try. (I’ve never used JB Weld before…this stuff is amazing!)

First, I needed a way to cover the hole so the JB Weld doesn’t just ooze out of the bottom of the flange. I covered a piece of aluminum angle with some painter’s tape (so I don’t weld the angle to the spar!).

Then I just clamped the angle to the bottom of the flange:

And finally I covered the hole with JB Weld. On my test run, I wiped all of the excess JB Weld so it was exactly even with the surface. When it dried, it became a little too concave. So, instead of doing the same here, I put put it on, but didn’t wipe the excess off. This way, when it dries, I’ll just use my little Scotch-Brite wheel on the air grinder to make it exactly even with the surface.

This stuff cures in 24 hours, so tomorrow we’ll see how this turns out.

The next step is to prime all the countersinks, but I’m leaving that for a warmer day (It’s freaking sleeting in Austin, in April!!)

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