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Hi, Chris!
You might want to think about putting the 'T' stiffeners on
the outside of the hull - much easier to do and gives you a lot more room
inside, or, if you're happy with the volume inside the internal stiffeners it
will allow you to decrease your hull diameter by twice the height of the
stiffeners.
Seems counter-intuitive, I know, seeing that the hull is in
compression - one would think you'd want internal stiffeners to keep the hull
from 'collapsing'. The external T's will do almost exactly the same job - as the
hull membrane between the stiffeners tries to 'collapse' it has to to pull the
verticals into an asymmetric buckling mode (like a wavy ribbon) - the horizontal
'T' top flat bar won't allow the vertical to begin it's wavy
buckle.
The internal/external stiffener difference in depth rating is
quite small, but the ease of fabrication and other advantages are
significant.
Good Luck with your sub!
Phil
----- Original Message -----
Sent: Sunday, June 17, 2012 7:14 PM
Subject: Re: [PSUBS-MAILIST] My current
submarine design: Specs and picture
Emile, thanks for the pointers. I was originally looking at
10-20kW with the thought that I would normally be running the main prop at
part load while cruising, and having additional overhead if needed. Maybe I'll
look for between 5-10kW instead.
Jon, I've attached a new picture showing dimensions. I mis-typed 10'
4" when it is actually 1' 4". With regards to adding weld build-up to
dissimilar thickness parts, does it need to be a 1:4 gradient? Also, the ABS
spreadsheet shows 1136.2psi allowable working pressure for 5/8" 40" OD
hemi-sphere (39.375" mid-plane diameter) with a .67 usage factor. Is there
something that i missed doing in the calc?
-Chris
On Sun, Jun 17, 2012 at 4:57 PM, Jon Wallace <jonw@psubs.org> wrote:
Hi
Chris,
Recommend more specifics when describing your sub, for example
giving distinction between length of pressure cylinder and heads. Keep
them separate. You said 10 feet 4 inches for overall length of
pressure hull and I assume that includes the hemispherical heads.
Deducting 40 inches for the heads it looks like the pressure cylinder
is 84 inches in length. At .625 inch thickness with .5 inch thick ribs
at 24 inches on center the ABS hull calculator on our web site is showing me
a max depth of 1526 feet. It is also showing me you'll need .875 inch
hemi-heads which would provide 1575 feet. So one inch hemispherical
heads are not out of the question especially if 7/8 inch is hard to find,
but you'll be looking at some welding build-up to match the heads to the
pressure
vessel.
Jon
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