7/31/2008 Tank Z-Brackets - 2 hours I have decided to use the Dan Checkoway method for fabricating my tank attach z-brackets. I marked six of the brackets with a centerline offset 1/16" toward the web (for the six most-outboard brackets) and one bracket with the centerline offset 1/16" away from the web (for the most-inboard bracket).
I went by Home Depot and picked up a spring-loaded center punch so I can operate it one handed. I used it to mark the center point for the #12 center hole. I stacked up some washers on an AN3-4A bolt and used a nutplate to bolt the brackets to the main spar. The washers help space the bolt far back enough so the threads never reach the locking portion of the nutplate - no need to tap out a nutplate or fight to tighten the bolt all the way down - it simply catches the first few non-locking threads of the nutplate. I then squared up the bracket to the spar, checked the underside so that the line was centered in the hole, then back drilled the remaining two holes in each bracket, using the holes in the main spar as a guide.
I then used the bolt, washers, and nutplate trick again as a jig to drill the holes for the rivets in each bracket. I deburred all the holes and called it a night.
8/02/2008 Tank Z-Brackets - 1.5 hours Today I riveted the nutplates to the Z-brackets. First I had to countersink where the rivets went. I also drew my lines on the fore side of the Z-brackets that will hopefully line up with the holes in the rear baffle.
I also countersunk the holes in the spar where the inboard-most z-bracket will go. The top- and bottom-most rivet holes had to be countersunk with the deburring tool because the spar bars prevented the countersink cage from getting over the holes. On the left wing, I'll be sure to rivet these nutplates on BEFORE attaching the ribs - there isn't much room to get in there to buck!
