More VS spar work and trouble countersinking

My wife Meggin helped be tonight with final drilling some holes in the VS spar, the spar doubler, and the rudder hinge brackets. It all went well until it came time to countersink several holes in the spar doubler. Apparently I’m not using the countersink cage correctly, or my technique is just bad. I was paranoid about countersinking too far so I started off by backing off the cage several clicks so that it would start cut a shallower countersink and then I could slowly work it back up to the correct depth. Once I got it set correctly it worked well for three holes but on the fourth hole, without changing the cage depth at all, it countersunk the hole too deep.

These two holes were countersunk very well
This hole was countersunk too deeply

I assumed it was my fault somehow so I decided to try using my drill press so that I could hopefully do a more consistent countersink. I started off the same way I did at first, I backed it off several clicks and slowly worked back to the correct depth. Once it was set, I moved on to another hole and that one ended up too deep as well. I ended up trying this on several more holes and some ended up just right, others were too shallow, and some were too deep. Maybe I have a bad countersink tool or maybe I just wasn’t positioning the part correctly on the drill press. Luckily I have a friend who has already built an RV-10 coming over tomorrow so I’m going to see if he can figure out what I’m doing wrong.

This was a REALLY frustrating end to the build session tonight. I’m sure that this part is still fine to use, and I’m getting tired of reordering so many parts so early in the build, but I’m going to replace it. I could have lived with one hole on the part that was a little too deep but now I have four and even though no one will ever see this part once the airplane is finished, I’m just not willing to accept this level of quality. I just hope I can get my problem figured out before the replacement part gets here!


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