Bottom skins clamped in place ... for more on Wing Stand
Z-Bend fits nicely over built-up rib
Left wing panel with inner-bottom skin clamped in place.
exactly into the Z-Bend confirming the accuracy of the build
Match drilled angles hold rib-tops in position.
Top wing skin moved down to the next set of holes as verification.
Rule used to double-check distance between the top rib holes.
With the rib top flange secured ... back-drill the hole closest to rear-spar.
Make certain the rear-spar portion of the skin is pressed down tight to rib.
Flange space is too close to permit bending of the drill bit.
With bottom skin pulled down and flat, back-drill hole closest to main-spar.
Note: the short Cleco to allow drill bit to pass over.
Finger bends 12-inch drill bit to ensure the hole is drilled perpendicular to skin.
Note: bottom wing skin is in the upper-left of the image.
Once the top and bottom holes have been established,
Re-install the top skin to accurately align all the rib tops.
Then using a flexible drill guide, drill the remaining bottom skin holes.
(Probably all of the holes could have been back drilled.)
Once all the wing kind rib holes are drilled in the bottom skin,
I removed the top skin and back drilled the spar cap holes.
Note: the easy method to hold the drill perpendicular!
Ignore camera lanyard swinging into view.