Joining the Rear and Center Fuselage Assemblies – 2

The F-770 forward side skins were fitted next.

I was installing the optional step on each side of the fuselage, so I used a hole saw to drill the F-770 where the tube of the step would pass through, using the pilot holes to show the location.

I then clecoed the F-770 forward side skins to the F-704, F-705, and F706 bulkheads, and the F-773 aft side skins.  It was necessary to raise or lower the tailcone slightly to align the holes.

I used a straight edge to mark the flanges of the F-623 corner ribs where the step comes through using the F-770 forward side skin and F-725 baggage rib as a guide. I then removed the ribs and trimmed them on the table.

Then the forward ends of the main longerons were checked to see that they followed the top edge of the F-770 side skin.  The bend/twist in the longeron was adjusted until they did.

I fit and drilled the F-720 armrests, fluting them lightly between the holes in the armrest to make them match the holes in the fuselage side skin.  After drilling, I removed and stored the armrests as they would be installed after the side skins are riveted on and the seat floors are installed.

The LP4-3 blind rivets would also be installed later, after the installation of the F-704Ks.

I removed the F-770 forward side skins to make the conical bend at its lower aft end which would be rolled to fit the aft fuselage. I clamped the F-770 to the table with a couple of C-clamps and a length of angle and arranged the skin so that the bend line rested between the edge of the angle and the edge of the table. I drilled a piece of scrap AA6-125 angle to match the lower edge of the skin and clecoed it to the skin, using clecoes in every hole.   The bend of the skin was very tight -a sharp 90 bend – on the forward end, and opening to a gentle curve at the aft end.  I clampEd visegrips to the aft end of the angle and used a twisting, rolling motion to start the curve. At the same time, I used a strong push with the thumb of the other hand to form the tight bend at the forward end. It took several tries and trial fits to form a bend that made a smooth transition to the rear fuselage.

I also made and installed the F-623A Rib Attach Strips that fastened F-623 to F-705, as illustrated by View C-C’, DWG 22.

Finally I clecoed the F-770 skins back on the fuselage.

Time: 8 hours.