[PSUBS-MAILIST] concrete
hank pronk
hanker_20032000 at yahoo.ca
Fri Apr 11 22:32:11 EDT 2014
Marc,
I would think that one test is not enough especially with concrete. I would want in the range of ten tests to failure just because of the unknown. I like it but just can't get there from here. It will take some serious resources to prove the concept. I may make a sphere in the winter and destroy it just to satisfy my curiosity.
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, 10:14 PM
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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> > >
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