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Hi All,

I previously completed my left main spar and I’ve started banging in the rivets on the right main spar.
I’m getting pretty close to spar mating and it’s starting to worry me.

I think I will follow the factory endorsed method and updrill the attach blocks only to 1/4" for now, and updrill to 3/8” with one of those piloted drill bits when rigging the wings.

To ensure the best possible outcome I believe updrilling of the blocks from the current 3/16” to 1/4" now should be done as good as possible, if I end up with an oval hole it will not serve as a good guide for the piloted drill bit when updrilling to 3/8” later on.

So how to make sure this is done well, updrill the holes in the blocks in small steps? Maybe try to put the whole spar assembly leveled on my drill press? (not sure if my drill press has the reach required to drill a hole that deep).

Any suggestions?

Thanks.

I clamped them together and used a drill bushing guide to drill the holes:





If you don't want to do it this way, use a drill press. I wouldn't recommend free-handing this job!