Re: Concrete subs?

[Axel Iehle <ai@augusta.cma.fr>]

Hi All,
I searched DEJANEWS http://dejanews.com/
for 'submarines' and found out that there is a thread
running in sci.military.naval about cement subs.
I haven't read all messages, but I caught the proposition
 of a double fiberglass/cement hull. This sounds really wrong to me.
Different materials won't react the same under pressure, temperature, UV,
chemicals,... and then how do you check both? If concrete is to be used for 
sub hulls, this should be waterproofen by an additive (like those used for 
swimming pools. They make concrete waterproof AND a bit softer so it can 
absorb deformation without cracking) inside the cement mixture, not around it.

Paul's description of a possible procedure to build a concrete hull sounds 
good but still some major issues should be answered:
- How making concrete waterproof?
- How having a perfect connection between concrete hull and jonction steel 
plate
(concrete shrinks a lot during drying phase)?
- How calculating the strength of such a hull (where, how, and what kind of 
iron bars stiffening of the concrete should be used?)

These questions seems to me impossible to answer at our level for a "x" 
percent safety operation
(replace "x" with the figure you accept to play your life with).

Though I still think concrete could be an idea to test (SHALLOW WATERS!) the 
behavior of a certain hull shape.

Axel Iehle


>Paul Anderson <hacker@geeky1.ebtech.net>  wrote:
>
>I was in the magazine store the other day, and Popular Mechanics had a
>blurb on a submarine made out of concrete.  That got me thinking about how
>one could construct such a thing.  My idea is that, basically, you build
>it up from two halves, each half starting with a steel plate fitting the
>profile of the sub, rebar is then welded to it to create the essential
>shape of that half, at which point the concrete is poured around the
>rebar(probably using a mould).  When the concrete has set for both halves,
>the steel plates are then welded together and internal hardware is them
>mounted in place.  Any thoughts, beyond difficulty of transport?  TTYL!
>
>
>---
>Paul Anderson