I had a bit of trouble working on the E-606PP spar, had to reorder it and had to match drill and counter sink the new part to go into the left elevator. The problems cenetered around the need to support the material during the countersinking process. I also had to consult the Van's help line to figure out how to accureately set the depth on my countersink cutter. Overall I learned that I had been countersijnking my holes too deeply, and that I should be countersinking just enough that the dimpled material going into the countersink sits proud a slight amount.
If you look at the first attempt at countersinking, you'll notice that the first attepmt that the countersink bit drifted as the bit cut into holes. I also struggled to keep the drill perpendicular and as such some of the round holes ended up squared as the bit cut into the aluminium.
So I stopped and reordered the part (actually two of them), to try to make the trim tab again. This time I created a jig using a length of anle stock with holes drilled into it at the rivet interval. this allowed me to both secure the material, cut into it at 90 degrees, and finally cut the hole straight into the material. the results of my second attempt were remarkably better.
