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

[Rick Lucertini <empiricus@sprint.ca>]

protek@shreve.net wrote:

> The third method would be to pour the hull, end caps, and conning
> tower in one pouring.    [snip]    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!

All things being equal, I'd have to say that steel subs, including learning the
welding skills necessary, are probably easier to build than concrete.  However,
people who know something about concrete don't have a problem with forms.  As with
steel, one-time pours of a hull are not especially complicated.  But, yes, they do
require heavy duty form construction.  It's my feeling that a person would have to
enjoy working with the material.  Form construction is straightforward, though.

> How are you going to be sure that
> you have all the air bubbles out of the mold?  What happens if you do
> have an air bubble?  Plaster over it?  What about inside the hull wall
> itself?  X-ray it?

Industrial concrete vibrators do a good job of reducing bubbles.  Of course, mixing
the concrete properly is primary to cement/water ratios.  I believe it was Dave Irons
who had mentioned that voids can be filled by injecting with polymer.

> Supposing you used method-3.  Once you got your hull finished
> the outside would come off easily I assume, but what about how you
> would get the inside form out?

Standard boat building technique: smash it out, tear it out or politely disassemble
it using the reverse setting on your well charged cordless drill.

> I think it was proposed to use wood
> for the inside forms, I think it was for the beauty of ceder or
> something like that.  How do you remove the wood??  Do termites
> eat cedar?  What about African Termites, can you import them for
> the job?  Just a little joke here, chill Rick...  Nothing personal.

Enchanté  ;-)     We are assuming here that a hatch opening is allowed for prior to
the pour to permit access to the interior.

I had proposed using cedar (for the beauty) as a deck and hull material epoxied over
marine ply decking for a wet or ambient boat only.  It's a proven technique for
conventional wooden boats.  An ambient sub is certainly nothing too much more complex
than a boat with a hole in it.  That's why conventional boat building techniques can
work so well with this type of sub.

I would only use cedar planking inside a one-atm. sub if access plates were designed
in for plumbing, electrical, etc.  There was, in fact, a lovely little one-atm. sub
designed for "the man who had everything" back in the hey days following WW I.  I
have a picture of it somewhere.  The darned thing had a wood and brass (a proper
yacht, you know) interior with buttontucked bench seats and, I believe, teak
flooring.  Bring your own tophat.

As for forms on the inside, laminates of thin ply cold-molded over a circular (or
whatever) form would give the cylindrical shape needed.  Certainly very labour
intensive.  More so than steel.

>    Being as I have built my own fully functional sub and taken it
> down a number of times I would like to give some insight into what
> you are probably going to feel if you do build a sub and test it.  You
> are going to wake up in the middle of the night and start thinking
> about what could go wrong that you have not thought of yet.  You
> are going to question each and every one of your decisions.  If you
> are using a material like concrete, you will wonder about it before,
> during, and hopefully after the dive.

I don't know about the rest of you, but, that describes what my experience will be
like regardless of the material I choose, and regardless of whether it's a wet boat,
ambient dry or a thwump boat.  It's the feeling I get whenever I've worked on the
Caravan and find myself in farm country at 0200h with the family asleep and a map in
my lap.  "Did I reinstall that O2 sensor properly?"  "What about the fuel pump - so
THAT'S what those two gaskets were for!".

An interesting thing about boat builders.  I have to assume this applies to psubbers,
as well.  Home builders tend to overbuild their craft.  I'm sure psychology plays a
strong role in the process.  In working with concrete, this may be a good thing or a
bad thing.  After reading about the necessity of leaving out most of the rebar, I'd
have to wonder about whether over building would weaken, strengthen or . . .

> [snip]
> It is a
> common misconception that the hull is the majority of everything
> and if a hull could just be constructed, the rest will be easy and fast.

Hmmm.  Sounds like a conventional boat to me.  Same dilemma.

> [snip]        I think that the main reason people want to try different materials
> is that they do not feel comfortable welding or don't really know
> how.

That was certainly my reason for choosing other materials.  I've worked with
concrete, wood and fiberglass. Even knowing what I do about one-atm. hull
construction, I still feel more comfortable with a dry ambient.

Now, if it was a toss up between bone necrosis from long term shallow water diving
(vis a vis wet/dry ambient, day in and day out diving) and learning to be comfortable
with a one atm. sub, I think I'd learn how to weld.


Rick


--
Rick Lucertini
empiricus@sprint.ca
(Vancouver, Canada)