This session concentrated on countersinking the row of holes in the T-00001-L & -R Fuel Tank Skins that attach the Skins to the T-00002 Tank Baffle to fit the head of a AN426AD3 rivets. Typically, material that is .040 thick gets countersunk (and material thinner gets dimpled). The Fuel Tank Skins are .032 thick, but will have the Tank Baffle underneath it. The plans state:
“Countersinks that are up to .005 too shallow are acceptable and preferable to countersinks that are too deep”.
*****If you recall from earlier in the Wings build (Top Wing Skin, Part 11), the same statement was made concerning the holes in the Inboard Top Wing Skins that were countersunk.*****
I started by making a cut, then checking the depth with the AN3 rivet. Based on the fit of the rivet head, I would adjust the depth of the countersink cutter, make another cute, and re-check. This process continued until I achieved what I felt to be the proper depth. This process took a little while to get the results I wanted, but definitely worth it in the end.
In the picture below you can see a portion of the holes that were countersunk in the row with clecos on the bottom of the picture.
I was able to finish the top row of 73 holes and 36 of the 72 holes on the bottom row in the Left Fuel Tank Skin. I will complete the remaining holes and the Right Fuel Tank during the next session.