My grandfather and I continued to work on the plane today and focused on the leading edge skins. First, we installed the stall warning horn ground wire to the spar web per section 441, finishing the wiring steps that must be completed before the skins are installed. From there, we once again installed the PVC into the nose ribs to align them (rather than using tape) thereby completing section 452. The nutplates were already installed in the landing light housing and it was generally the correct width to fit between the nose ribs (trimmed) so section 463 didn’t require any action and we were ready to start section 494, installing the skins themselves.
Once again, we drilled the hole for the middle rivet in each of the end nose ribs, stretched a string line between them to mark the positions of the other holes, and then drilled the rest with a #30 bit. This will allow us to match drill them through the skins from underneath. We also performed this same procedure for the top row of rivets in the fuel tank bay. With that complete, we began putting the skins in place, carefully marking the position of the top middle rivet, match drilling it, and then working outward to finish the other ribs for the skin. This went much more quickly on this wing since the manual had instructed us to trim the intermediate nose ribs and skip installing a rivet in them. Since the ribs were already trimmed, we couldn’t have still installed a rivet even if we had wanted to. This really sped up the process though since transferring the position of the center rib onto the skin and drilling accurately was a bit of a challenge and somewhat error prone (as evidenced by the two holes that “missed” in my right wing).
This worked well for the 3 most outboard skins and we were careful not to drill the final (most inboard) hole until the next skin was in place. Unfortunately, we had some issues with the most inboard (fuel tank bay) skin and will need to replace it. We tried holding it in place flat up against the spar cap while drilling but this is made extremely difficult in this bay since the fuel tank straps sit between the skin and the spar cap. After drilling the first two holes, we realized that the skin was positioned a little too far down and was also not quite straight. The good news about this mistake is that, since the holes in the ribs were pre-drilled, we can just get a new skin and start drilling it again like nothing happened (we don’t have to redo anything else). The bad news is that it’s a part to have to replace and we will have to wait to receive it - meaning that we won’t be able to finish the skins during my grandfather’s visit.