I marked centerlines on the F-772B floor stiffeners per the plans. Read Wirejock build log about drilling these solo. Clamped in place with centerline showing and noticed a large gap with the firewall gussets. Thanks to Draker for highlighting this issue and describing the fix. I trimmed the forward end of the stiffeners to clear the firewall angle and reclamped the stiffeners in place. They fit well against the gussets, but no centerline visible through the bottom skin. Used a sharpie to mark several hole locations on the stiffeners. Removed and saw that all the holes are about 1/16 off the centerline and will have sufficient edge distance. Reclamped the stiffeners and match drilled through the skin, clecoing as I went. Removed the stiffeners and deburred all holes.
There was no way to clamp the outboard stiffeners with the skin in place, so I removed the skin and clamped them to the firewall angle and the F-704 bulkhead using the centerline. Match drilled one hole on each end using the firewall and F-704. Removed the stiffeners, reinstalled the bottom skin, and cleco'd the stiffeners back in. Centerline was visible in all the holes. Proceded to match drill and cleco the remaining holes in the stiffeners. Removed the stiffeners and deburred all holes.
