Drilling the wing box stringers

[flion]

So I read in the plans, section 13, the procedure for drilling the stringers and wondered what they were for; it looked like they would interfere with the ribs. So I delved into the plans and it soon dawned on me that they became the stringers that go spanwise midway between the front and rear spars. So we're not really match-drilling them to the spar; we are just using the spar as a drilling jig (and a potentially inaccurate one, at that). That gives us a chance to booger up the holes in both the stringers and the spars before we ever get the skins on. I'm wondering why we don't just match drill the stringers to the skins the same way we did for the stringers in the tail cone. Did anyone do it this way? Am I missing something important here that make it imperative to pre-drill the stringers?

 

[Auburntsts]

You could I supose, but it's way easier just to follow the plans and use the spar. That method works just fine. Reasons why I wouldn't want to use the skins:

- Since the row of holes that the j-channel gets riveted to is in the center of the skin that makes it's use as a drill guide problematic. So that leaves the forward edge holes which have gaps where the access plates will go meaning now you have to do an extra step to account for that. Just another potenial way to screw something up.

- Using the spar allows you to cleco both siffeners in-place and locate them accuarately (remember the short and long stiffeners nest together) and you can do it very quickly. Using the skins is doable just more cumbersome. With the tailcone, you had the bottom skin and bulkheads in-place to hold the sides in position while doing the drilling, which is not the case with the wing skins.

Bottom line, it's not that you couldn't the skins, but I just don't see how it would make the job any easier or less prone to error. My $.02.