I used these same fasteners on my Lancair IV having learned
about them from Brent
Regan.
I selected them instead of using hinges along the side
of the cowl because I modified my cowl inlets such that the side seam between
bottom and top cowl is no longer straight, but curves up at the front.
I also selected them because I have incorporated cowl flaps
to control the cooling air flow, and when closed, they increase the separation
force between top and bottom cowl requiring a lot of shear resistance. The
Tridair fasteners (part numbers from Bill, below) have exceptional shear strength.
They are produced by Alcoa which has a huge aerospace fastening business based
in Southern
California.
Alcoa bought all the big name fasteners, put them under one roof, but kept the
original brand names. They were probably responsible for the 787 fastener
delays.
Some cautions:
1)
As
I recall the studs are $18 apiece and the receptacles are $24 apiece or $42 a
set. That was a few years ago.
2)
They
require precision drilled hole for the stud.
3)
They
use a quad lead thread and little engagement tabs on the bottom of the studs
which engage a spring loaded ratchet in the socket. You only
tighten them finger tight. They are locked by the spring loaded
ratchet. Do not over tighten!
4)
Don’t
ever force them into their hole. You will damage the threads
and/or damage the little engagement tabs on the bottom of the stud. If
the stud does not go in, try some other studs to get the alignment corrected
(it must be dead nuts right on the money), wiggle the cowl, but DON”T
FORCE THEM. Been there, done
that once, and at $18 each, that was enough. Putting your cowl on will
require a bit of extra patience as they can be fiddly, particularly if the temperature
changes such as can happen when the top cowl is in the shade, bottom cowl is in
the sun, and you then try to put them together. As I said,
patience.
5)
If
you are not in the USA,
fuggetaboutit. They are DOD export controlled, and can not be shipped
outside of the USA without a Dept. of Commerce
permit. Really! Been there, done that too.
Fred Moreno
I just recently looked into these fastners and found
them from:
I spoke with Margo Bryant.
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