----- 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