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Jon, Jim, Hugh.......
I went through the same problem a while back after Cliff pointed out that
my hull penetrations weren't up to par. I had been using the "cubic inches" idea
rather than the "square inches" as Hugh mentioned.
The solution I have developed with help from Hugh ( thanks again, Hugh ) is
to remove the entire window frame for the largest 24" main window ring and
replace it with a much thicker ring.
The calculations we worked out came up as needing about a 1-1/2 inch
thick ring ( by 6 inches long ) for the larger window with a 2 inch thick
plexi-base ring inside the thicker window frame.
The smaller 12 inch windows need the same thing but the "fix" will include
replacing the current assembly with larger windows ( 16 inch viewing area ) and
again much thicker window rings.
This is a big change so will be done sometime next year. In the meantime my
maximum depth will be limited to about 50 feet until the proper design has been
run through a comprehensive FEA to determine the exact dimensions. I too was
confused by the documents as it relates to how much material to replace what was
cut out for the penetrations.
This is still a bit of guess work because the documents are really talking
about penetrations in the tube section rather than the end caps, so an FEA that
relates specifically to eliptical head penetrations will be required.
Basically.......I'm not WHACKING a new hole in there until all the facts
are in !
Frank D.
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