Re: How catastrophic is catastrophic?

[protek@shreve.net]

Rick,
    My attempt at humor was not a flame of anyone on here talking about
concrete.  I once saw in Popular Science or Popular Mechanics a large boat
built out of concrete.  And I have no idea where to start on a concrete
sub.  All that I know about concrete is that I have never seen a concrete
structure with or without rebar that was not cracked somewhere.  I have
seen large culverts break when rolled off a truck.  I know, from my past
knowledge, that if you want it to be water tight, you will have to
construct it probably in one seamless piece.  I know that its coeficient of
thermal expansion is different from metals and if joined to metals at
places like window seats the two must be engineered to slide against each
other as the temperature changes.  It is a far more brittle material than
steel in general.  When I was younger, I was into designing habitats using
concrete.  I worked out the thickness to counter the boyancy generated by
the enclosed air etc.  I could see a mobile habitat constructed like this.
But frankly, and it may be from my ignorance, I would be absolutely
petrified to find myself in a concrete sub.
   One factor you need to think about for the wire mesh deposit method;
deposits of any material out of solution due to an electric current are
related to the current density (amps/sq meter).  This is true in
electroplating and would be true in constructing a habitat.  Where the
current density is highest, there is the highest rate of deposit.  This
would be tricky to say the least.
   I have receintly seen photos of a sub from someone who is probably not a
member of psubs.  It is in the final stages of completion and it could be
fatal if it goes below 20 feet, due to the construction.  Also, oddly
enough, I do not know where it is, or who it belongs to.  The pictures were
sent to me from someone who does not know either.  They were passed to him
etc, etc.
   As long as I am allowed to stay on psubs I will probably try to persuade
people to not venture out into what they do not know about.  I admit that I
do NOT know anything about concrete, but few do know about it for a use
such as proposed.  I just do not want to see anyone get hurt, and the idea
of using exotic unapproved materials scares me here.

Gary Boucher

P.S. This is NOT a flame.  Anyone considering it so is misunderstanding me.



At 10:59 PM 3/14/99 -0800, you wrote:
>DaveIrons@aol.com wrote:
>
>> >I think I am seeing a dead horsie surfacing in a concrete hulled sub,
>> or, no it may be a, yes, a wire mesh electrolysed hull.
>> Gary Boucher
>>
>> Has this subject been discussed before?  I would be interested in any
previous
>> discussions.
>
>Previous discussions cover a lot of territory to be sure.  Unfortunately,
boredom
>sets in for some when a thread goes longer than a few postings or when the
subject is
>considered useless, irrelevant or ridiculous (a concrete sub?  Let's get
back to
>"real" sub materials).
>
>This discussion is actually hammering out many of the technical details we
need to
>design and dive in concrete safely.  I don't think we're approaching the
barn quite
>yet.    ;-)
>--
>Rick Lucertini
>empiricus@sprint.ca
>(Vancouver, Canada)
>
>
>