I started final assembly of the center section this morning. First up is to rivet the crotch strap brackets to the appropriate ribs. I used solid rivets here instead of the blind rivets called for in the plans. These can all be reached with the squeezer when the ribs are out in the open like this.
These pairs of ribs can then be riveted and bolted to the aft side of F-704 (bolts go through the top and bottom ends of the forward flanges of these ribs and through the thick spar carry through bars).
Now the rest of the ribs can be riveted on. I also final torqued all of the rib to F-704 bolts and lacquer sealed them.
F-705 and the baggage ribs can then be riveted on. Because of the rear spar carry through, spacers, etc., the lengths of the rivets varies pretty significantly through here, so pay close attention to the rivet callouts.
While access is good, I bolted on the control mounts and lacquer sealed them.
Since everything is now bolted to the aft end of F-704, there is no reason not to bolt the two halves together. I reinserted a couple of close tolerance bolts to ensure perfect alignment, then installed the two AN4 bolts and spacers.
Here is a closeup of one of the spacers and the installed bolt. I had to use three washers under the nut (the maximum allowed) to cover the grip (this bolt is a little long like this because it also holds part of the gear weldment on nosedraggers).
I riveted together the connecting straps for the modified seat ribs and temporarily installed them so the ribs are more rigid during the next few steps.
I also installed the one leg nutplates in the top of the crotch strap brackets. This would have been easier to do before riveting these to everything else.
I deburred and dimpled the bottom skin and shot a little self-etching primer on the parts that will be covered by the corner ribs and F-704.
Finally, I clecoed the bottom skin to the center section skeleton. This is ready to rivet; I need to see if I can find a riveting partner sometime in the next couple of days.
