----- Original Message -----
Sent: Wednesday, February 12, 2003 5:03
AM
Subject: Re: [PSUBS-MAILIST] Pressure
hull
Thijs,
Even though this hull design is very different
from the normal PSUB hull, it does have a number of nice features. It
fits well with a streamlined FRP outer shell in that it presents a
smaller projected area to flow relative to other hull shapes that will
accommodate a seated pilot. For it displacement, it also has good
freeboard and might actually make it possible to meet the ABS 2.5 ft (76 cm)
minimum freeboard rule for a small boat without destroying the hydrodynamic
lines of the boat. The viewport locations are great for forward and
downward viewing. Side viewports could be easily added to improve
port and starboard visibility Because all viewports are flat,
the cost becomes manageable for a PSUB. Orientation of MBTs are going to
take some thought in order not to have the CB of the boat to close to the
bow. I am not sure I would go with mild steel for hull. You should
be able to find off the shelf torispherical endcaps made of a higher yield
point steel such as A516, Gr 70 or something equivalent without significantly
impacting the hull cost. I agree with Alec that it would be a good idea
to run an FE analysis of the hull including viewports to get a better handle
on crush depth. I am not sure the ABS equations to calculated hull
stress are applicable given such a short cylindrical section.
I for one like the hull.
Cliff
----- Original Message -----
Sent: Sunday, February 09, 2003 11:02
AM
Subject: [PSUBS-MAILIST] Pressure
hull
To all,
The idea is to construct a very simple pressure
hull out of two torispherical endcaps.
The conning "tower" is made out of a standard line pipe with
a little overdimensioned wallthickness and the smallest possible
diameter. The endcaps are made with a small cilindrical section on it
but i am afraid that the tower will intersect with the torispherical
part.
In order to keep it simple i chose a very
common steel for the endcaps. It is P265GH (yield strenght 265 n/mm^2, 38500
psi, tensile strenght 410 n/mm^2, 59500 psi). This is an "off the
shelf" material at Afflerbach, the german manufacturer. I think you could
call it soft boiler steel.
To calculate the strenght of it (apart from
the conningtower and viewports) one can use the formulas for a sphere,
using the dishing radius of the endcap (in this case 1040
mm). Maybe it is my age, to much alcohol or lack of intelligence
but watever method i use (ABS, Lloyd's or an old pressure vessel
codebook) i get different outcommings. Can anyone of you say something
sensible on this? I am considdering a wallthickness of 12 mm, divingdepth
100 mtr?
If it is ever going to be build it will be
tested unmanned to a depth 50% more than its safe working depth. Should
it collapse i will hold no one responsible for that. So please be free to
give your advise.
Thank you very much,
Thijs Struijs
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