My standard bulkhead flanges at the widest point are approx. 5/8 inch wide
measuring from top. A centerline on that flange would put the hole center at
5/16 inch. Great edge distance!
Measuring the flange area at the corner radius (cornerwrap area), the flange
necks down to approx.. 7/16 inch (3/8?) depending where you measure (again,
measuring from top). With that in mind, I drew a centerline on this narrow
flange. I then took into consideration and mentally deducted the thickness
of material (.025), minus 1/16 or so for the inside radius (I don't like
drilling holes too close to radius) and kept in mind that a #30 hole will be
drilled on this centerline. Rivet end expansion/mushroom to approx. 3/32
inch diameter was also taken into consideration. That would keep the rivet
expansion/mushroom1/32 inch away from the radius. This would make the final
edge distance approx. 1/8 inch. That is if you can hit every hole exactly
(which was my main goal) and the flange was a consistant width, which mine
is not. Other considerations I factored, were the shear that these specific
rivets would see, distance between said rivets, quantity of rivets holding
these parts together, the epoxy primer (very, very minimal) and the
thickness of the final riveted areas. Factored at the overlap areas were
three plys of aluminum (included two overlapping with good edge distance)
and spanning the length of the cornerwrap radius. Total thickness of these
three plys is a little over 1/16 inch thick (.065 inch), it seemed to me
that my 1/8 inch edge distance wasn't something I was going to worry about.
I also took into consideration where, at the corner radius, there were two
plys of aluminum (worst case at .045 inch thick) and 1/8 inch edge distance
didn't seem a major problem to me.
That is what my calculations were anyway. Geez . . . all of that was many
years ago!
Now one might be able to use a 3/32 inch Cherry Rivet in lieu of #30 Avex
which would give one more edge distance?
Enough rambling.
Over-and-out . . .
Terry "I am going to sleep good tonight" Dazey
Rebel 662
Lake Tapps, Washington USA
Actually I didn't aim for the centerline but rather as far from the edge
as I could without hitting the face of the bulkhead.
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