Date:	12-29-2013
Number of Hours:	7.90
Brief Description:	Center Fuselage
I found the spacer blocks I borrowed from another local RV-7 builder, and checked their thickness against the spar stub thicknesses I measured yesterday (photo 1). The spacer blocks are anywhere from 0.005 to 0.010 thinner than the spar stubs, so I adjusted them with one or two layers of masking tape (~0.005 per layer) to bring the blocks to within a few thousandths of the spars. I then clecoed the F-704A assembly in place, clecoed the F-704H plates in place, then used the spacer blocks to check the fit. The blocks were a medium slip fit, so the spars should be slightly tighter. I then used two large bolts on each side through the bulkheads and spacers to attach the forward 704 bulkhead to the aft one. Using 5 washers on each bolt, I was able to use the nylock nuts to snug the bolts without getting into the locking material. I was a bit quick on the draw on attaching the forward bulkhead, as just about the time I got the bolts snugged I noticed that I hadn't final drilled the F-716 floor ribs to the aft bulkhead. :O( After taking care of that oversight and reinstalling the forward bulkhead, I final drilled the forward row of holes in the F-776 bottom skin to the F-704A bulkhead flange. I thought about waiting to drill these until the forward bottom skin is in place, but the instructions are pretty clear about doing it now. I suspect it is due to the fact that the center bottom skin and bulkhead flanges wouldn't be easily separated for deburring and dimpling after being riveted to the floor ribs. I then fabricated an 0.040 dimple coupon with standard 3/32 dies so I could properly set the countersink depths for the four holes where the floor stiffeners attach (photo 2). After setting the countersink depth (11 "clicks" deeper than for a rivet) on a piece of scrap and checking it with the coupon, I countersunk 4 holes in the F-776 bottom skin and F-704A flange. The fit looks great! The dimple coupon fits flush against the skin, and there's no sideways play (photo 3). (continued)