Mike Bullock's RV-7: Rib match drilling

Build Time:
2236 Hours

Flying & Maintenance Time:
1693 Hours

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[January 31, 2006]

Tonight I got the counterbalance skin clecoed to the two end ribs. This took some work and I needed to rig something up to squeeze the ribs together tight to get some clecos in. I suppored the bottom of one rib with some scrap wood and then used a clamp to compress the ribs. It worked rather well. I did this for both the left and right side.

Now comes drilling the counterweights with a #12 bit. This is more or less of a blind process. I was scared to death that I was going to end up with some holes too close to ribs/edges. Everything looked good when I was done. I took my time drilling and made sure that everything was straight. One of the holes might be maybe 1/64" or so too close to the rib. I might need to shave down the corner of a washer a hair or so.... Hindsight being 20/20, I would of definitely done this in a drill press. There is just too much that could go wrong here that could ruin a perfectly good day. I consider myself lucky!!!

Next I clecoed the counterbalance ends to the spars. Once everything was together, the alignment on everything got better. I don't know why, but all my allignment concerns went away. I drilled the inner rib #40 holes. Then the skin went on, finally the horn brace went on. Match drilled everything.

Next I took the skin off and dimpled the #10 screw holes (#12 drill holes) with the Avery #10 screw dimpler. Next countersunk the counterweight. I made a template to check my countersinking depth. I went ahead and did the left countersink while I had the countersink set.

Finally, I countersunk the inner spar where it attached to the inner rib with a #40 rivet. The inner holes are easy to get to. The outer two interfere with the countersink cage. I ended up putting the countersink bits into the swivel deburring tool and that worked great. It was slow enough to work at a comfortable pace, but fast enough to give a good looking face to the countersink.

One thing I noticed on my trailing edge of my right skin was some slight buldges where the stiffeners might of squeezed into the skin. When I put a ruler over them, the ruler didn't even find them, but they reflect in the light of my shop. I called Van's up about this too, and Scott said it wasn't anything to sweat about. I was able to push some of them down a little with my fingers. Man, my next RV is going to turn out so much better knowing what I do now!

This is how screwed up some of the holes are in the countersink skins.

I used this clamp to squeeze everything together. Before you gasp at how bad this setup is, I had a bunch of plywood shims between the lower rib and the table. The end result put NO MARKS IN THE RIBS.

Next I drilled the holes for the counterweight. I used plenty of BoeLube to lubricate this drilling process.

Finished product. I put the ruler on the edge of the counterweight to level everything out. With it sitting on the bench by itself, it was about 5-10 degrees off.