I'm struggling with the directions regarding the wing skins. Below is the excerpt from the Vans provided directions. The part I'm struggling with is the part in bold
Cleco the forward row of holes in W-702 and W-703 skins to the matching holes in the main spar. Cleco the W702 and W-703 skins in place using a cleco in every fourth hole.
Don't forget to insert the doubler between the ribs and the W-702 skin. The main skins overlap at the eighth rib from the root. The outboard skin should fit on top of the inboard one.
Gently pull ribs into position if the matched holes do not align with the skin holes. Drill all the holes to final size.
Start drilling in the upper middle of the panel and work down and out toward the edges, work out any slack as you go.
Move the clecoes down one hole (into the drilled holes) and drill all the remaining holes.
Draw a couple of lines on the main skins that intersect at the center of the hole for the tiedown eye.
Remove the bottom main skins before fitting the leading edge and tank skins. Leave the top skins clecoed.
Where I'm lost is it tells me to remove the bottom skins, but it never tells me to install them. The installation is only the top skins. Further, it tells me to start drilling before checking the wing for any twist. This feels like it could cause me to build in a twist.
So questions:
1) Do I need to install the bottom skins also before drilling?
2) Do I need to worry about a twist in the wing before I start drilling?
Cleco the forward row of holes in W-702 and W-703 skins to the matching holes in the main spar. Cleco the W702 and W-703 skins in place using a cleco in every fourth hole.
Don't forget to insert the doubler between the ribs and the W-702 skin. The main skins overlap at the eighth rib from the root. The outboard skin should fit on top of the inboard one.
Gently pull ribs into position if the matched holes do not align with the skin holes. Drill all the holes to final size.
Start drilling in the upper middle of the panel and work down and out toward the edges, work out any slack as you go.
Move the clecoes down one hole (into the drilled holes) and drill all the remaining holes.
Draw a couple of lines on the main skins that intersect at the center of the hole for the tiedown eye.
Remove the bottom main skins before fitting the leading edge and tank skins. Leave the top skins clecoed.
Where I'm lost is it tells me to remove the bottom skins, but it never tells me to install them. The installation is only the top skins. Further, it tells me to start drilling before checking the wing for any twist. This feels like it could cause me to build in a twist.
So questions:
1) Do I need to install the bottom skins also before drilling?
2) Do I need to worry about a twist in the wing before I start drilling?