12/30/2003
7 hours: The first step in wing construction is making a large number of very deep countersinks on the spar which will eventually help attach the fuel tank. Since the countersink will enlarge the hole it is not easy to keep things centered. I spent quite a few hours setting the countersink and coming up with a good method...
Here are the first few countersinks. You can see on the edges of the photo that the hole starts out pretty small and ends up pretty big.
The technique I ended up using is just a piece of scrap metal clamped to the back of the spar with a #30 hole in it. Rather than clecoing, clamping, and unclecoing it, I just stuck a long rivet in the back and centered it by eye. This worked out really well.
You can either use high drill speed and lots of boelube to prevent chatter, or low drill speeds and high feed pressure. The latter gets the job done much faster, oddly enough.
I did all 62 of them tonight, this is the bottom side.
