----- Original
Message -----
Sent: Friday, September 18, 2009 7:20
PM
Subject: [PSUBS-MAILIST] Hello; Design;
Materials; Thanks
Dear
Sirs;
First,
let me say hello and thank you in advance for your
time.
I’m
considering building a submersible with the following
characteristics.
L:
25’
B:
6.5’
D:
2.5 - 4’
Operational
depth 30’ – 50’
Brief
dives to 60’
The
vessel will conduct itself primarily in semi-submerged/ low-profile
condition (aside from the conning tower stacks etc.), showing full
freeboard only in harbor, or as dictated by necessity. At the
desire of the operator, the vessel can make brief, excursion dives up to
the aforementioned depths.
The
exact depths are yet undecided.
In
other words, I’m looking to build a David-boat/Monitor type vessel
capable of excursions to a designed depth, mostly 1.5 to 3 atmospheres
with extended submerged endurance. Early-early WWI submersibles
were treated (and designed) as surface-craft with limited submersible
capability. I would like to mimic this design
concept.
The
nature of these requirements clearly points to a dry-ambient submersible
but I wish avoid the dry-ambient for the reasons of decompression.
Even at thirty feet, there are no-decomp limits, and I would like to
avoid these issues if possible. Although I’ve considered limiting
dive depths to 20’, in which case ambient would make
sense.
Materials:
Some
pre/post-Victorian vessels were made of thick wooden planks, metal
sheathing, riveted construction, and included deadlights and
scuttle-glass portholes. Many of these vessels were capable of
greater depths than I am now proposing. What are some today’s hull
materials that could give me the same performance more
cheaply?
Why
not consider steel/fiber/carbon/etc. reinforced plastics, or wood, given
the limited design parameters. Indeed 60 psig is large, but it seems a
trifle to many of today’s resources. Far older and more poorly
designed submersibles dropped past 70’ with materials of lesser quality
– and lived to tell the tale.
Would
it be folly to sink 5’ in a hull made of 3” wood? What about10 feet? or
25? At what depth does wood betray you to the abyss?
What
about 5/16” steel? Would I be called an engineering marvel for
using 5/16” in a vessel designed to dive 5’ feet?
Personally,
I suspect that most industrial strength materials will bring you safely
back from a depth of <33’ – even those of mediocre
design. Informally, it appears that most shallow water (1.5 – 2
atm) accidents related to through-hull/porthole failure, as well as
entanglement and swamped with decks awash. Hull failure due to
pressure buckling appears to be a rare event in shallow waters. I could
be wrong, of course.
Ultimately,
I suppose I’m looking for design/hull-materials advice given the
operational characteristics I’ve already mentioned.
Thank
you all for you time and I look forward to a response.
TC