1. Located upper fuselage longeron doublers 6B16-4. 2. Removed material at aft of doublers to match gusset and seat back surface. 3. Slid doubler aft, pushing fwd edge outboard. 4. Located exisiting rivet hole in primary longeron at fwd end of doubler. 5. Drilled pilot hole into existing hole with #40 bit. 6. Clecoed in place. 7. Slid aft end of doublers inboard, until edge just lined up at the widest point. 8. Taped in place. 9. Using hole duplicator, drilled to match existing hole in aft gusset. 10. Clecoed doublers at aft hole as well. 11. Traced edge of pimary longerons on outboard lower surface of longeron doublers with fine tip pen. 12. Cut outboard of line with band saw. 13. Sanded smooth to line in iterative attempts with belt sander. Used large dog bath to cool metal between sandings. 14. Dressed sanded edges with file. 15. Installed atop primary longeron with end clecoes. 16. Marked "no rivet" zone at aft end of longeron doublers for later striker plate installation. 17. Established rivet line atop doublers with 40 mm pitch. 18. Center punched rivet locations. 19. Pilot drilled with #40 bit and clecoed alternate holes. 20. Opened holes with #30 bit for A4 rivets.
