Brief Description: Center Fuselage - Crotch Strap Brackets
Today I drilled the right crotch strap brackets to the seat ribs and floor. Today's drilling only took about half the time that it took on the left set a couple of days ago, now that I knew what I was doing.
I finished up the fabrication of the crotch strap brackets by drilling the 5/16 bolt holes in all four brackets. I marked one of the aft brackets by extending the vertical centerline of one of the existing holes down, and marking the horizontal centerline 1/2 inch below the existing hole to allow for the longer Crow harness fitting. Since I had already drilled and marked each bracket to a particular set of ribs I was careful to mark and drill the outboard side of the vee. After pilot drilling one aft bracket to #40, I clecoed it back to back with the other one, and drilled it.
With the aft brackets pilot drilled, I assembled the brackets to one rib and clamped a spacer between them, then pilot drilled the forward bolt hole. I then clamped the fore and aft brackets together firmly, removed them from the rib, then drilled them out as a set to just under 1/4 inch in the drill press. I finished up by opening up the holes to 5/16 with a unibit.
I spent the rest of the time deburring all new holes and edges, and countersunk all the rivet holes for attaching nutplates to the brackets and ribs.