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Jon, I have been thinking about hull penetrations for hatches
and windows and looking at ASME / ABS. There is a very simple rule of
thumb that the reinforcing ring should be a minimum radial thickness
of 5% of the hole diameter and the height of the reinforcing should be a minimum
of 6 times the shell thickness. Somehow this simple formula should be put
into the ABS Hull calc tools. I.e. a 20” diameter hole should
have a 1” thick ring 24” should be 1.2”. We
could also just add a sheet to the existing ABS calcs, I’ll send a
sample so you can have a play. We need Cliff to check it. Regards,
Hugh From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com 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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