[PSUBS-MAILIST] concrete
Marc de Piolenc
piolenc at archivale.com
Fri Apr 11 22:44:22 EDT 2014
Actually, the consistency of the results of the NCEL tests on
un-reinforced concrete is what encourages me to consider only one final
check on the numbers for the hull as a whole. I expect even better
consistency from ferrocement because of the absence of coarse aggregate,
which is the major source of "scatter" in finished concrete properties.
The presence of reinforcement in the form of fine, distributed mesh with
high surface adhesion also builds confidence.
It will also be possible to build small test panels to cheaply test the
properties of the cured composite on land without investing in a
complete hull.
Currently trying to recover some of my Dropbox and local hard drive
space so I can post the reports that I have,
Marc
On 4/12/2014 10:32 AM, hank pronk wrote:
> 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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