Today I drilled the F-652 top baggage bulkhead to the F-706 fuselage bulkhead and F-751 lower baggage bulkhead. I started out at #40 to check hole locations, then went to #30 before I realized that due to a miss-read of the plans and a poor assumption on my part, that the bulkhead was about 1/16 lower that called for in the plans.
The problem was that I could not tell where the 5/8" measurement on the extreme right of DWG 29 locating the bottom edge of the upper bulkhead was referencing from. I found a post on VAF that correctly stated that it refers to the distance below the top outboard corners of the lower bulkhead where the flanges are cut out. The post incorrectly stated that locating the bottom edge of the upper bulkhead 3/4" below the upper flange of the lower bulkhead would put the upper bulkhead in the proper location. AFTER I had drilled the screw holes out to #30 (so I could locate a nutplate with a cleco for match drilling its rivet holes), that I should have located the lower edge of the upper bulkhead at least 13/16" below upper flange of the lower bulkhead. The result is that the holes in the upper outboard corners of the lower bulkhead are only 1/4" from the upper edge rather than 5/16" everywhere else
Before drilling all of the screw holes to final size, I calculated that I could lower the upper bulkhead down by 0.040" without elongating the holes. I traced the top edge of the upper bulkhead in its incorrect position, then re-taped it in the new position using a scrap piece of 0.040 between the top of the bulkhead and the reference line. I then drilled the 4 holes along the top center to final size and installed nutplates. I then secured the upper bulkhead with these 4 screws and proceeded to drill the rest of the screw holes. The location isn't perfect, but it's less than 0.025 from where it should be. I'm going to let it ride.
Rivets Today: 8
Rivets Total: 11701
All screw holes in the upper bulkhead initially drilled to #40 to the structure.
4 nutplates installed along the top and all screw holes drilled to final size.
