The plans call for the rudder counterweight, and the counterweight rib in which it sits, to be drilled out with a #10 drill.
Ah. The Avery Tools RV toolkit comes with almost everything, but not a #10 drill.
The UK Avery distributor, Gloster Air Parts, hold #10 cobalt drills at about a fiver for a pair, so I've ordered those for first class delivery.
Since I'm ordering stuff anyway, I've also treated myself to a hex adapter for the countersink/deburring bits, which is a little bit of luxury that allows deburring using an electric screwdriver rather than the manual method used to date.
Not cheap, but advice from other build logs is that it will pay dividends when building wings and fuselage.
#10 drills and hex deburr adapter - next day delivery
