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Time to start skinning the wing! The first thing to do is to make sure the wing frame is square and true to eliminate any twist in the wing. Sonex has an instruction sheet that details how to do this on the workbench, but when I attended the builders workshop, Sonex suggested doing this on a couple of saw horses and let gravity assist you. This is the route I am going.

The first thing to do is to make sure the hole in the aft spar attach plate is aligned to a point that is 19 inches outboard of wing station 0.0. This sets the inboard location of the upper wing skin and squares up the ribs to the wing spar. To help align the hole to this point, I used a socket cap machine screw that has the same diameter as the hole and drilled out the center. This allows me to pass a piece of piano wire straight through the center of the machine screw and will act as a registration pointer to align the center of the hole to the 19" location. I also attached some scrap aluminum to one of the tooling holes on the inboard rib and attached another piece of scrap to the wing station 0.0 hole on the spar. I clamp these scap pieces together to lock the position in place once I establish the proper alignment between the rear spar hole and the 19" mark.

To eliminate twist, I used a method I saw on Jeff Shultz's website. I used some piano wire and hung it from the top tooling hole on the outboard rib and shimmed the spar until the wire exactly aligned with the lower tooling hole on that rib. I also did the same thing on one of the inboard ribs. After doing the alignment, I checked for any twist between the wingtip and the root ribs by using my digital level. I confirmed there was practically no twist. I got this aligned to within 0.05 degree of twist - basically dead on.

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