Now that the HS is finished, it's back to the VS for yours truly. I match-drilled the new spar reinforcement bar to the new VS spar, and then set about cutting out a new set of lightening holes. I discovered that the non-removable pilot drill in my fly cutter had gotten bent somehow, so this time around I decided to try a set of hole cutters from Hougen by way of Cleaveland Tool:
They were outrageously expensive but they do a good job of cutting nice round holes, and give me the willies somewhat less than the fly cutter. The other aspect I failed to realize until after I'd bought them is that the set doesn't include a 1 1/2" cutter, only 1 3/8" and 1 3/4" ones. Rather than spend yet more money special-ordering the correct cutter size, I decided to just cut the specified 1 1/2" holes 1/8" undersize using the next smallest cutter I had. Since the lightening holes are optional anyway, it just means that I have a spar reinforcement bar that's slightly heavier than it needs to be.
Let's see… five 1 1/2" holes that are each undersized by an eighth of an inch, in 1/8" thick aluminum… 0.224 in3 of extra material, at 2.643 g/cc… the tail of my airplane will be a third of an ounce heavier than it might otherwise be. Yeah, I think I can live with that.
For the remaining two 2" holes I did have the right sized cutter, so I finished those too and all my lightening holes are now drilled. Deburring will have to wait till tomorrow when I can run the air tools without waking up the neighbors.
