Hi Rob,
Having just done this very operation I will share what I can. Sorry though. I took no pictures during the process.
First off I elected to mount my conduit through the ribs in the approved location as opposed to through the lighting holes. I taped short segments of conduit in various positions and then hung the bottom skin and tested sticking my hand through the access panels to simulate maintenance. What I found for me was that I personally disliked having the conduit through the lightning hole. Either the conduit was in the way of the aileron bellcrank or the aileron bellcrank was in the way of the conduit. When the conduit was in the position approved by Van's it seemed to be out of the way the most.
The instructions on placement and how big a hole you can put in the ribs is
here.
It took a while but I found a thin wall (about .012") polycarbonate tube with an OD of about 9/16" that fit very nicely through a -10 snap bushing. The tube is tough, abrasion resistant yet flexible enough to not require a laser straight path through the ribs and the -10 snap bushing will fit in the allowable 3/4" hole.
I figured out if I had a drill 12" long I could get through the four ribs in the wing walk area and from there out I would use a short bit in an angle drill and go in through the access panels. You can get all the remaining ribs doing it that way until you get to section without skin and life gets easy again.
I made a little fixture from a piece of scrap aluminum that I could clamp to the rib with a side grip. The fixture just had a #30 hole in it at the correct location and the idea was I would drill a #30 pilot hole through the rib and then the plan was to follow up with a step drill to 3/4". I shaped the fixture piece to somewhat conform to the lightning hole shape so i could get a relatively consistent location as I moved it from one rib to the next as I was drilling. This would get me a set of holes through the ribs that were relatively straight.
I had a step drill that topped out at 3/4" but I had to find an extension for it. Problem was, all the extensions were click lock types and the shank on my step drill was too big for the
universal extensions I could find. After a couple days looking I gave up and took my step drill to a friend and we turned down the shank of the step drill in his lathe.
Once all the plans and tooling had been made it was an easy chore. I started at the root and clamped my fixture on the end rib and drilled a #30 pilot hole. Then I opened the hole to 3/4" with the step drill and moved my #30 fixture to the next rib etc etc. I would not recommend attempting to pilot drill all four wing walk ribs at once. To me that just seemed a way too easy way to make a large alignment error in short order. The root rib has no issues, even the second rib in has no issues but the third rib will be drilled in perfect line with the holes in the first and second rib so they better be perfect. As I said, I elected to pilot drill a rib, then open it up. That allowed me the ease of drilling through tighter and tighter quarters without having to worry about alignment.
Once all the holes were drilled and opened through the wing walk area I switched to short threaded bits in an angle drill for pilot holes and had the step drill in a collet that could be threaded into the angle drill. After all the holes were drilled I spent quite a bit of time ensuring the hole edges were smoothed with no burrs.
If you still want pictures of tools or procedures I can stop by the airport Saturday and take a few.
Hope that helped.
