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Hi Jon. That's about what I came up with without ribs. My number was
326 feet but again, I'm no math whiz.
I haven't done any calculations on the ribs yet because I'm still designing
the final interior space layout, but I have a general design in mind where the
ribs are located in areas where impact and overall pressure apply the most
stress. The ribs radiate out from the hatch ring which sticks down into the sub
4 inches. The ribs so far will be made from 1/2 inch by 4 inch plate cut to fit
the inside curvature. I won't be using the "T" shaped ribs but instead am
leaning toward "ladder" type stiffener bars between the ribs. I know that's not
as strong as the "T" shape but fabrication will be a lot easier and maintenance
tasks like grinding and re-painting will be much simpler. I'm trying to
keep the whole corrosion problem to a minimum and having just straight ribs will
make it possible to get a small grinder down in there if any rust starts to
develop. That and I want to be able to inspect the whole inside/outside surface
regularly without disassembling anything.
Additional plate ribs will be added around the window openings, and the
floor will have a grid pattern creating pockets for lead ballast bricks. Two
main ribs running front to back across the bottom will be used as
stiffeners, backing for the keel mounts, and runners for the reclining bench
seat and sliding ballast weight.
My friend who ran the numbers thinks that with the stiffeners I roughed out
for him, the crush depth is just over 900 feet, not counting the windows. That
seemed a little high ( deep ) to me, but like I said, I'll not be going very
deep until I get some good reliable data on just what this pressure hull is
able to take.
Thanks for running those numbers. I'll tell my buddy his calcs were
confirmed by the "expert" in the club. Frank D.
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