[PSUBS-MAILIST] concrete
Marc de Piolenc
piolenc at archivale.com
Fri Apr 11 22:14:56 EDT 2014
Great minds think alike. I suggested to a friend, who had bought a
fiberglas tank packaged as a 20-foot ISO container, that he split it on
a vertical diametral plane, hinge it at one end and use it as a female
mold for making submarine hulls or submarine habitat modules. I was
thinking in terms of laminated ferrocement technique, so no inner mold
required, which is good because I would have no idea how to keep it
centered. I went to a lot of trouble to work out how to support the
weight of the growing FC structure and how to integrate at least some of
the necessary appendages and hull penetrations, but I never heard from
the friend again on this topic. I guess he wrote it off to momentary
mental aberration.
Concrete is still, despite NCEL, very much an unknown quantity in
submarine engineering terms. Besides the NCEL reports, some information
is available from the offshore oil industry, which builds gigantic
semi-submersible platforms which may extend to depths of hundreds of
meters, but even that data is hard to get hold of and hard to interpret
for our purposes.
My plan, when I finally build my ferrocement or prestressed sub, is to
build two hulls (take two - they're cheap!). One will be sacrificed by
ballasting to slightly negative buoyancy and sinking it, unoccupied, in
waters deep enough to be certain to exceed its crush depth, then
recording the depth where the first failure occurs and the final crush
depth. That will be used to calibrate the code used to design the second
hull. Considering the fact that the test hull will be only that - no
fittings or equipment of any kind other than the data recording module
which will be recovered - and considering the cost differential between
concrete and steel - I think I can bring in the test hull and the final
hull for much less than a single equivalent steel hull. And as for
maintenance...he he.
Best,
Marc
On 4/12/2014 9:50 AM, hank pronk wrote:
> Marc,
> I built a concrete hull for a sub once. I took a 500 gal propane tank and split it like a hot dog bun and mad a mold from it. The inside mold floated in the concrete and the hull thickness was thin at the top and thick on the bottom. It was a failure but when I opened the mold the outside of the hull was perfect. It was a cheap experiment. Now I know how to do it. I work with concrete all the time in different ways. My company does concrete cutting, concrete demolition and concrete line pumping. My problem is, I am not a mathematician or an engineer. I like the idea, but can not implement it due the lack of engineering. There is no room for guessing with submarines.
> Hank
> --------------------------------------------
> On Fri, 4/11/14, Marc de Piolenc <piolenc at archivale.com> wrote:
>
> Subject: Re: [PSUBS-MAILIST] concrete
> To: personal_submersibles at psubs.org
> Received: Friday, April 11, 2014, 9:42 PM
>
> I think I will post those reports to
> Dropbox.
>
> Right now I feel like I'm one of a tiny deviant cult of
> Portland cement
> cultists within the psubs community. Maybe the reports will
> help me
> proselytize new adherents...
>
> Marc
>
> On 4/12/2014 9:03 AM, hank pronk wrote:
> > Marc,
> > Not only is it dirt cheap, concrete is so easy to form.
> The material cost for a 6 foot sphere is in the hundreds,
> not thousands. Hank
> > --------------------------------------------
> > On Fri, 4/11/14, Marc de Piolenc <piolenc at archivale.com>
> wrote:
> >
> > Subject: Re: [PSUBS-MAILIST] concrete
> > To: "Personal Submersibles General
> Discussion" <personal_submersibles at psubs.org>
> > Received: Friday, April 11, 2014, 8:26
> PM
> >
> > I don't have hard numbers, but
> > remember that resistance to mostly
> > compressive loading is a structural
> STABILITY problem. Most
> > practical
> > steel structures buckle under
> compression long before
> > reaching their
> > actual compression limit. Concrete has
> an advantage there
> > due to its
> > stiffness - the NCEL tests suggest
> that it comes much closer
> > to using
> > its full compressive strength.
> >
> > That said, my primary interest in
> concrete is due to its
> > cost and ease
> > of maintenance.
> >
> > Marc
> >
> > PS. If anybody is interested, I will
> add the relevant
> > reports that I
> > have to my public Dropbox folder and
> post the link.
> >
> > On 4/12/2014 3:15 AM, hank pronk
> wrote:
> > > A six foot od sphere built in
> 1.25in thick steel would
> > be equal in weight to 4in thick
> concrete. I would not
> > ever expect 4in concrete to compare to
> 1.25 steel.
> > But, it would be interesting to know
> where the concrete
> > stands in comparison.
> > > Hank
> > >
> --------------------------------------------
> > > On Fri, 4/11/14, Marc de Piolenc
> <piolenc at archivale.com>
> > wrote:
> > >
> > > Subject: Re:
> [PSUBS-MAILIST] concrete
> > > To: "Personal
> Submersibles General
> > Discussion" <personal_submersibles at psubs.org>
> > > Received:
> Friday, April 11, 2014, 9:59
> > AM
> > >
> > > A huge amount of
> work was done on
> > > concrete for
> pressure-resisting
> > structures, including long
> > > term, deep
> exposure tests, by the US
> > Naval Civil Engineering
> > > Laboratory. Most
> of the reports are
> > available for
> > > downloading free
> of charge from DTIC.
> > >
> > > Excellent
> results were achieved with
> > concrete having NO
> > > reinforcement.
> There has been limited
> > work done with
> > > prestressed
> concrete and even less
> > done with reinforced
> > > concrete and
> ferrocement, which can
> > reasonably be expected
> > > to give much
> more efficient and
> > distortion-tolerant
> > > structures.
> > >
> > > Marc
> > >
> > > On 4/11/2014
> 8:25 PM, hank pronk
> > wrote:
> > > > A cheap
> alternative to a super
> > strong sphere hull is
> > > re-enforced
> concrete. I feel like
> > hiding under a blanket
> > > while I say
> this,lol. I know it
> > is way out there, but
> > > concrete is
> super strong under
> > compression. It is not
> > > so good for
> impact resistance.
> > Concrete is a very easy
> > > material to work
> with and form into a
> > sphere shape. I
> > > have no idea
> what thickness would be
> > needed. Properly
> > > engineered I
> would trust it.
> > > > Hank
> > > >
> > > >
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