[PSUBS-MAILIST] concrete

[Marc de Piolenc]

EXACTLY.

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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