I was able to start fitting the wing skins today, the first step was to verify the wing was square and without twist. Step one was measuring corner to corner, and step 2 was dropping plumb bobs off of each wing rib and measuring to ensure the distance is equivalent on both ends of the wing.
Here is the outboard wing rib.
And the inboard wing rib.
The next step is supporting the center of the wing to take the sag out of the wing. A tight line down the length of rivets shows the sag in addition to sighting down spar.
In this picture the line should be aligned with the top of the string. Supporting the center of the wing makes the skin installation much easier.
Here is the spar after it has been supported.
While I was reviewing things I ran into a couple of problems. The first was an easy fix. On one of the ribs near the center of the wing, I left the wrong hole open. The line in the upper section of the picture is where the flap brace attaches, that circled rivet should be left open, and the hole with the arrow pointing to it should have a rivet in it now. Easy fix, just drilling out and replacing a rivet.
The other issue I ran into was the outboard spar supports overhung the sides of the ribs. The skins also overhang for the wingtip attachment. You can see the issue in the figure below.
After notching and reworking the braces, I was able to get back to fitting the skins.
Here are the bottom skins fitted, you can see the new larger brace here.
On the top skin side, I had to notch both brackets to clear the skin. I added additional braces where parts were notched, and then rechecked the wing for straightness.
To create the notches, I first cut out initial notches with a cut-off wheel, and then filed them for clearance.
With the spar supported, the skins went on very easy, the only clecos that were a challenge were the ones that went through three materials, the skin, spar, and then the rib.
Next step is to drill the wing walk doubler, and fit the top skins.