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Task: Finished attaching tank nutplates to
right spar. Fabricated tie-down brackets
I started the day by working on the right spar tank attach
nutplates. I had already predrilled the holes yesterday so
I went right to riveting. I started on the top flange, riveted
the nutplates, then countersunk them with my #30 countersink
using the same OD of 0.370. I then flipped the spar over and
riveted the bottom side nutplates. Once I had countersunk
all the tank nutplates I changed to the #40 pilot and countersunk
the inspection plate holes to an OD of 0.312.
Once all the holes were countersunk I masked
off the spar and primed it with NAPA 7220.
task was to fabricate the W-731 tie-down bars. They were already
the correct size but needed to be drilled 3/16".
I then tapped them 3/8-16 x 1" deep. LOTS
of cutting oil used!
Next I cut 4 W-726 spacers out of AB4-187x1.25 material. They
are cut into 2" lengths and edge deburred.
I then marked over 1" and down 5/8" to find center
I used my Unibit to drill the holes 3/4". The plans call
for 1" lighting holes but I really didn't want to use
my fly-cutter. Its a dangerous tool and these spacers are
pretty small to clamp down. They are spacers only so I was
I then taped the W-726 in place and clamped
the W-731 tie-down bracket onto the spar. I used the one bolt
hole and a square to align the bracket on the spar and ensure
it was square. I then drilled all the holes to #12.
Next I marked through a K1000-3 nutplate for
the rivet holes, center-punched, and drilled to #40. I match
drilled these holes to the W-726 spacers.
Repeated the drilling on the right spar.
Finally, I primed the tie-down brackets.