This is my first post on the forums, and I'm working on my horizontal stabilizer for my RV-9A. As is tradition, I've hit a couple of snags fabricating my HS-908 attach angles. I had to remake one, but I think I have the outside dimensions right. I've started drilling holes, and I used a tip from the forums for getting the top center holes lined up, at least vertically (clamp both angles to a piece of scrap aluminum and use one as a drill guide).
I drew Sharpie lines to mark where I wanted the remaining holes to be, and I used my pin punch to make a small divot where I wanted the hole to be centered. I used a new #40 bit, centered it in the divot, and drilled slowly, but the holes came out slightly off from where I wanted them to be.
I have what I think (if I'm reading my technical reference correctly) is adequate edge margin (all greater than 0.250", assuming the electronic calipers I got from Lowe's can be trusted), but the holes are not uniformly spaced among themselves, and some holes are closer than the 0.500" called for on DWG 3. I measured the distances between them and added the hole diameters; the distances (center to center) range from 0.464" to 0.565" (remarkable that it's almost exactly 0.100" from smallest to largest!). I think the minimum distance is three times the diameter of the rivet (again, assuming I'm reading the technical reference right), and for these AN470AD4 rivets that should be 0.375", so the 0.464"-0.565" range should be fine.
remake the angle, but I don't know for sure that I'd make a better one if I did. And part of this task is learning what's serviceable and what to redo. I know once I match-drill the HS front spar and doubler plate, I'm committed to either accepting the angle or buying a new spar half and doubler plate.
I'd appreciate any thoughts or suggestions! Also, any suggestions for getting the other angle drilled right the first time?