Predrilled holes in spar

[Txairmale]

I purchased the built-up main wing spar with my kit. I am preparing to install the main spar through the fuselage and have learned the hard way too many times not to rely on the predrilled pilot holes. I set up the W17-06 over the predrilled holes but did not updrill the spar. The inside dimensions between the left and right W17-06 is exactly 27 inches. I measured the outside dimensions of the fuselage sides with the root ribs installed and it measures 27 1/8".

Has anyone else had issues with this?

Suggestions?

[inventor]

I think you are talking about the inboard wing skins. I am pretty sure they are not cut square but have a taper to match the out of squareness of the spar/rib assembly. Maybe because of the slope of the outboard pivot ribs.

[Txairmale]

I marked the C/L of the spar and the location of the pilot holes for the W17-05’s and -06’s on the top of the spar. I also verified the pilot holes were equidistant from the C/L. I inserted the spar into the fuselage and then adjusted it so the pilot hole marks were the same distance from the fuselage sides on both sides, about 3/32” on both sides.

I clamped the W17 brackets in place and drilled out two AN 3 size holes on each one and bolted everything in place. I then removed one side at a time and slid the spar out a few inches to make it easier to drill and ream out the rest of the holes.

Everything is flush and solid and I checked everything for plumb and level. I’m glad I checked before I just trusted the pilot holes and fired up the drill!