Drilled THE rear spar holes
This evening I did a bunch of rechecking of the wing alignment (square, sweep, incidence), then marked and drilled the rear spar attach bolt holes. For edge distance, I ended up with a target square about 1/8″x1/8″. Not a lot of room for error here, but I didn’t have to do any additional trimming either. I started with a #30 bit and worked my way up to just under 5/16″. I used some drill guide inserts for general squareness checks at #30, 3/16″, 1/4″, and 5/16″. I didn’t drill all the way up to 5/16″. The bolts measured .310″ and I have a .3110″ reamer that I used for the final hole. The holes are a perfect fit with that reamer. 5/16″ would be just a bit to big.
For those not “in the know”, these are very critical holes to be drilled, with very specific tolerances, that are dependent on a lot of previous construction coming together correctly. Definitely a flight safety concern if they aren’t right.
The holes are drilled and alignments rechecked again. Everything is spot on. The wings are square, don’t have any sweep, and both are straight without any twist. I’m very happy.
