Drilling Misaligned Holes?

[RVScooter]

This is probably a really stupid question that has already been answered, but I haven't been able to find it after searching through the forums. It's time to start drilling the fuselage skin holes on my 8A. The first instruction is to match drill the holes along the bottom of the F-891 Fwd Side Skin and drill new holes into the F-843 Lower Longeron. That's all fine and dandy, except that towards the aft end of the longeron you also need to drill through the F-895 Gusset and the WD-821 Landing Gear Weldment. The gusset and the weldment already have pilot holes that you're supposed to line up with the holes in the skin, but with the longeron in the way I'm not sure how to align all four layers of holes correctly. Any ideas from the brain trust? Every 8A builder has to have figured this out, but it's escaping me.

 

[Jonnyb]

I’m building an -8 so it might be slightly different.

On the side skin there are 2 indexing tabs that should align with the bottom of the lower longeron. As long as that happens. And all the rest of the structure aligns and is clecoed tightly then the holes “should” align.

Just make sure you drill perpendicular to the skin, I used a drill bushing for it.

Even saying all that, I still had 2 holes that were out and went up a size n rivet.

 

[Girraf]

From the drawing, it appears the weldment tab sits up about 1/8 to 3/16" off the horizontal part of the longeron rather than resting on it as you've shown in your picture. If you make that adjustment, looks like the line of holes in the side skin would be much closer to the holes in the weldment tab. In these type of instances when a solid piece is between two pre-punched pieces, I try to take measurements from a know reference nearby on both sides of the hole as some insurance that both pre-punched holes are line up.