Re: Chiseled in Stone (Or Concrete)...

[DaveIrons@aol.com]

Gary Boucher wrote


>Psubbers,
>I am often concerned about the safety of those on here.  

I've never heard anyone say they were not in favor of safety :-)

>I think
>everyone knows that I do not endorse all materials for sub
>construction, although in theory many could be used, but I
>seriously question the wisdom of their use for numerous reasons. 
>Concrete is one of those materials that I seriously question for use
>in a sub. However, I am not as worried about anyone getting
>killed in a concrete sub, mainly because I feel that nobody is
>going to build one to that stage of completion.
>Lets think about some facts here.  To build a concrete sub I can
>only think of three methods one could use.  First, you could
>construct a steel wire frame with wire mesh and apply the
>concrete on like plaster.  This would result in hideous flaws,
>severe weak spots, bad out of round conditions etc.  This would
>be an extremely dangerous approach to say the least.

What you are describing is ferrocement.  John Shaw told a story
of a ferrocement boat that broke up while transporting it to the
water.  If done correctly ferrocement is an excellent material for
boat hulls, if and only if it is constructed properly.  Tying the steel
into a rigid structure suitable for applying the concrete is incredibly
time consuming.  The concrete must be applied in exactly the right
way.  I would recommend that the builder call in a skilled
professional to apply the concrete.  I have rejected ferrocement as
a submarine hull.  The time required and the watch-making like
precision required is just too much for me to consider.  However,
someone with the knowledge, skill and patience to do the job
correctly my be able to create a submarine hull that combines the
compressive strength of concrete and the tensile strength of steel.  

>Second, you could construct each part separately.  A cylinder, end
>caps, 

The cylinder and end caps are bonded together with epoxy.
Seacon was built this way and the joints remained intact even when
the hull was tested to implosion.

conning tower, etc etc. 

The conning tower is located outside the pressure hull.  I would use
steel for that portion.

> But this approach would be extremely
>time consuming and would result in a bunch of concrete parts that
>could not possibly be "stuck" together with cement to hold in the
>environment to which they would be subjected.  Some form of
>rubber gaskets would probably need to be employed.  But, how
do you bolt them or fasten them together.  Are you going to use a
big O- ring at each joint?  

No O-rings are required the simple epoxy joist has proven
effective.  
 
>The latest that I have heard on here is that now  you cannot use
>rebar???  I don't know.  But, you will have to pull all
>these parts together somehow, and I cannot think of a safe way to
>do that, or even an effective way.

The experts do recommend that re-bar should be used.  I have
presented a method what I think is not only superior to steel re-bar
but also less time consuming.  It would also require less steel
which would make it more economical.  Take a look at my
previous post in which I describe using pretensioned steel cable on
the outside of the hull.  The method is nonstandard, however, it is
based on well established engineering practices.

>Ihe third method would be to pour the hull, end caps, and conning
>tower in one pouring.  Now, this would be by far the best
>approach from a seamless standpoint.  However, keep in mind
>that you will have to build an inside hull out of something to form
>the inside.  The outside will have to be contained by a second
>hull.  How are you going to support a sub inside a sub when
>pouring, steel bars (through hulls)?  Also remember the density of
>liquid concrete.  The hydrostatic pressure is high for only a foot
>or two of depth.  Your forms will have to be substantial!  

I can see you have put a lot of thought into this subject.  These are
important questions.

Yes, concrete weighs 5,000 lb. per yard that requires substantial
strength.  An inside and outside form must be built.  I described
form building in an earlier post.  

>How are you going to be sure that you have all the air bubbles out
>of the mold?

Whit proper quality control there will be no voids in the concrete. 
That is another reason, I would not place re-bar inside the concrete. 
The concrete is easier to compact, if I do not have to work around
the steel.

 >What happens if you do have an air bubble?  Plaster over it? 
>What about inside the hull wall itself?  X-ray it?

In an earlier post I mentioned ultrasound as a method of detecting
unsound concrete inside the pressure hull.  Another method is
examining x-ray diffraction patterns.  
Does anyone have any information on x-ray diffraction or
ultrasound technology?

The most import factor is, good quality control.  No voids should
ever be found in a concrete hull.  

>(Snip) Concrete; not so easy.  Everything has to have a special
>interface.  Windows; can't weld them to concrete.  You need a
>mounting system, and one that does not compromise the concrete. 
>Almost every system will be made more complex using this
>approach.

There are straight forward methods of mounting steel into
concrete:  
The hull penetrator can be built into the form and concrete formed
around it.  The expansion coefficient of steel and concrete are the
same.  I would apply a bonding compound like Acryl 60 to the
steel penetrator and to the concrete surrounding the steel.
An opening can be cast in the concrete.  The steel seat can be
epoxyied into the opening.  Both of these methods are standard
construction practices.

An alternative method I would like to explore is to use the concrete
itself as the viewport seat.  I explained this method in more detail
in earlier posts.  I called "viewport seats."


David Irons