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        <div dir="ltr" data-setdir="false">Hi Mark,</div><div dir="ltr" data-setdir="false">We do not find air pockets, in most cases the concrete is vibrated.  I think the issue is aggregate segregation.  Before concrete pumps, long chutes  witch will allow the aggregate to separate from the mix.  This common with those mixer trucks that mix on the spot also.</div><div dir="ltr" data-setdir="false">Hank</div><div><br></div>
        
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                    On Monday, June 26, 2023, 04:52:54 AM MDT, Marc de Piolenc via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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    <p>When you encounter an easy-to-cut section of concrete, do you
      find a void there (air bubble) or a place where the concrete
      exists, but has stratified of been allowed to dry before setting?</p>
    <p>Marc de Piolenc<br clear="none">
    </p>
    <div class="yiv5506290890moz-cite-prefix">On 6/26/2023 12:16 AM, hank pronk via
      Personal_Submersibles wrote:<br clear="none">
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      Alec. The Swiss sub was concrete with a slip form method.  I think
      Farrow cement is troweled onto a mesh frame.  I was pretty
      intrigued by this also. A conversation with Sean made me change my
      mind.  Although concrete structures under water have a good track
      record, the chance of a weak spot is too great.  My business
      includes concrete cutting, and often when cutting we hit spots
      that cut much easier within the same pour.  
      <div>Hank</div>
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        <div dir="ltr">Sent from my iPhone</div>
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          <blockquote type="cite">On Jun 25, 2023, at 9:08 AM, Alec
            Smyth via Personal_Submersibles
            <a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org" class="yiv5506290890moz-txt-link-rfc2396E"><personal_submersibles@psubs.org></a> wrote:<br clear="none">
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            <div dir="ltr">There's an interesting story about cement
              subs, which I will tell to the best of my recollection. In
              the early years we had a PSUBS member whose name I forget,
              I believe Swiss or Austrian, who had built a ferrocement
              sub that he kept at a mooring in a Swiss lake. The sub was
              successful, he dived it for years. But eventually he moved
              to Colombia due to marriage, and scuttled the sub in the
              lake, because the road he had used to take it there had
              been re-routed or modified somehow, leaving him without
              any way of getting it out. The sub became an attraction
              for local SCUBA divers. 
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              <div>The second part of the story is that another PSUBS
                member, Ian Roxborough, hired the first guy to build him
                a large cement sub with the intention of making it an
                ocean going live-aboard. The project was done completely
                on the level, with notification to authorities and in a
                major port. This was no drug sub built in the jungle. It
                got to the point where the hull was complete, and I
                think they were about for the first launch. However,
                Colombia being plagued by drug subs, the authorities
                would not sign off on final paperwork or something
                (can't remember the exact glitch.) Ian had sunk a ton of
                funds into it, and the sub was probably perfectly good,
                but approval never came. I'm not sure what happened to
                the sub. But Ian is still very much active, so maybe can
                tell us. I'm not sure if he's on the email list. If you
                are, Ian, sorry for bringing up this rather painful
                memory!</div>
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              <div>Best,</div>
              <div>Alec</div>
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              <div dir="ltr" class="yiv5506290890gmail_attr">On Sun, Jun 25, 2023 at
                8:35 AM Marc de Piolenc via Personal_Submersibles <<a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org" class="yiv5506290890moz-txt-link-freetext">personal_submersibles@psubs.org</a>>
                wrote:<br clear="none">
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                  <p>That's it. I lost interest when I realized he had
                    built a superstructure on a conventional pressure
                    hull.</p>
                  <p>Very sorry  to hear about Brian Cox.</p>
                  <p>Marc<br clear="none">
                  </p>
                  <div>On 6/25/2023 6:11 PM, Jon Wallace via
                    Personal_Submersibles wrote:<br clear="none">
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                      <div dir="ltr">Marc, that was probably Brian Cox
                        who passed away a year or so ago.  His pressure
                        hull was steel but he did use ferrocement for
                        the superstructure.  <a rel="nofollow noopener noreferrer" shape="rect" target="_blank" href="http://www.subdb.info/cgi/database/showvessel/index.cgi?ID=1272980224&VN=Esmae&VT=1">http://www.subdb.info/cgi/database/showvessel/index.cgi?ID=1272980224&VN=Esmae&VT=1</a></div>
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                      <div dir="ltr">There are no standards for using
                        ferrocement as a manned submarine pressure hull
                        and I think anyone attempting it would find
                        little support for the project given the Ocean
                        Gate loss.</div>
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                      <div dir="ltr">Jon</div>
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                        <div> On Sunday, June 25, 2023 at 04:09:00 AM
                          EDT, Marc de Piolenc via Personal_Submersibles
                          <a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org"><personal_submersibles@psubs.org></a>
                          wrote: </div>
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                          <div dir="ltr">I know. I fell in love with FC
                            for yachts, which made me wonder how <br clear="none">
                            useful it would be for pressure hulls...
                            Turns out there is a 2010 <br clear="none">
                            exchange of messages in my archive with
                            somebody on this list who built <br clear="none">
                            in FC, Brian Cox. Is he still there?<br clear="none">
                            <br clear="none">
                            Marc<br clear="none">
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                            On 6/24/2023 8:27 PM, Bernie Hellstrom via
                            Personal_Submersibles wrote:<br clear="none">
                            > Many boat hulls were made with FC. Even
                            the landing barges in the ww2 , to make
                            piers to in load ships!<br clear="none">
                            ><br clear="none">
                            > Sent from my iPhone<br clear="none">
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