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Re: Concrete keels?

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  • ellengaest@boatbuilding.com
    Mat, If you re wondering specifically about the MICRO keel in concrete,figure out first the weight of lead/cubic foot and then concrete.You will then very
    Message 1 of 17 , Nov 30, 2001
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      Mat,
      If you're wondering specifically about the MICRO keel in
      concrete,figure out first the weight of lead/cubic foot and then
      concrete.You will then very quickly see that,although there may well
      be wonderful products out there that will bond concrete to
      wood/glass/steel/foam etc...,the amount of concrete needed to equal
      the weight of the lead casting is rather impressive.Now imagine how
      you would get all that concrete to replicate the keel dimensions
      specified on the plans.
      We won't even talk about all the fuss of adding boiler punchings
      into the mix or some type of steel armature leading to all sorts of
      corrosion concerns...........
      In short,lead is hard to beat as are the time proven methods of
      securely attaching it to a hull.
      But then again,I'm a happy MICRO owner whoes field of vision may be
      slightly twisted by lust.
      Sincerely,
      Peter Lenihan.



      --- In bolger@y..., mat_man@u... wrote:
      > Hi,
      >
      > I was wondering if anyone had any luck with building something
      > like a Micro keel with ferrocement and attaching it with 5200?
      >
      > Thanks
      > Mat
    • pvanderw@optonline.net
      We can be specific. From William Garden s Yacht Designs, we get Lead - 710 lb/cu ft Iron - 440 lb/cu ft Concrete - 144 lb/cu ft By putting boiler punchings,
      Message 2 of 17 , Dec 1, 2001
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        We can be specific.

        From William Garden's Yacht Designs, we get

        Lead - 710 lb/cu ft
        Iron - 440 lb/cu ft
        Concrete - 144 lb/cu ft

        By putting boiler punchings, etc. in the concrete, we can increase
        the weight. Let us guess (I really don't know what is realistic) we
        can get

        Iron/Concrete mix - 250 lb cu ft.

        Now, the first 64 lb in each cu ft compensates for the displaced
        water, so the ballast effect is that much less than the above numbers.

        Lead - 646 lb/cu ft
        Iron - 346 lb/cu ft
        Mix - 186 lb/cu ft
        Concrete - 80 lb/cu ft

        The Micro ballast casting is supposed to be 420 lbs (from Common
        Sense Designs site) or .59 cu ft. and will have 382 lb of ballast
        effect. The equivalent ballast volumes are then:

        Lead - .59 cu ft
        Iron - 1.10 cu ft
        Mix - 2.05 cu ft
        Concrete - 4.78 cu ft.

        You can see that the keel would need complete redesign to use a
        concrete ballast casting.

        PHV
      • amoore@hfx.eastlink.ca
        I must agree with Bill here. There is a reason the old timers use lead most of the time and most of that reason is density. For the price and availability
        Message 3 of 17 , Dec 2, 2001
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          I must agree with Bill here. There is a reason the old timers use
          lead most of the time and most of that reason is density. For the
          price and availability you can't get much denser. Switching a micro
          keel to cement you would have to increase you depth quite a bit to get
          the same righting arm. There is another reason to use lead and it
          depends on the ballast location, not being familar with Micro's I
          don't know if this applies. Lead is soft and if external (bolted on
          the bottom of the hull as apposed to poored in the hull) ballast is
          used it can make for a very good shock aborber against an unfortunate
          bump on something hard like a rock. Iron can send a terible vibration
          through the hull affecting the keel bolts, cement could crumble and or
          vibrate the keel bolts(or what ever) which would be very difficult to
          repare. Any dents in lead are easy to repare.


          Andy
        • thomas dalzell
          In micro s case the slug is inserted into a plywood housing, so you couldn t get reasonable stability from cement in the shoe, but you possibly could with a
          Message 4 of 17 , Dec 2, 2001
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            In micro's case the slug is inserted into a plywood
            housing, so you couldn't get reasonable stability from
            cement in the shoe, but you possibly could with a full
            length cement keel.

            --- amoore@... wrote:

            <HR>
            <html><body>
            <tt>
            <BR>
            I must agree with Bill here.  There is a reason
            the old timers use<BR>
            lead most of the time and most of that reason is
            density.  For the<BR>
            price and availability you can't get much
            denser.  Switching a micro<BR>
            keel to cement you would have to increase you depth
            quite a bit to get<BR>
            the same righting arm.  There is another reason
            to use lead and it<BR>
            depends on the ballast location, not being familar
            with Micro's I<BR>
            don't know if this applies.  Lead is soft and if
            external (bolted on<BR>
            the bottom of the hull as apposed to poored in the
            hull) ballast is<BR>
            used it can make for a very good shock aborber against
            an unfortunate<BR>
            bump on something hard like a rock.  Iron can
            send a terible vibration<BR>
            through the hull affecting the keel bolts, cement
            could crumble and or<BR>
            vibrate the keel bolts(or what ever) which would be
            very difficult to<BR>
            repare.  Any dents in lead are easy to
            repare.<BR>
            <BR>
            <BR>
            Andy<BR>
            <BR>
            </tt>

            <br>

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          • John Bell
            Chiming in late here... I suspect this story leaves something out: Could it have been the keelbolts had been removed for some type of repair? But because the
            Message 5 of 17 , Dec 3, 2001
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              Chiming in late here...

              I suspect this story leaves something out: Could it have been the keelbolts
              had been removed for some type of repair? But because the keel had been
              bedded in 5200, it did not fall off right away without some persuasion.

              I can't imagine a manufacturer purposely leaving out keelboats. Too much
              liability there. 5200 is good stuff, but it ain't that good.

              JB



              ----- Original Message -----
              From: <mat_man@...>
              To: <bolger@yahoogroups.com>
              Sent: Friday, November 30, 2001 8:57 PM
              Subject: [bolger] Re: Concrete keels?


              | About the only thing I could find at rec.boat.building was
              | from Glenn Ashmore (builder of 45' stip/glass cutter):
              |
              | "I've seen a fin held on only by 5200 my self. To get it off, the
              | boat was raised with a travellift and a fork lift truck was brought
              | is to support the keel as the 5200 was cut off. Even then the fork
              | lift had to work the keel a little to get it off. Overall it was a
              | smooth operation and left me with a very comfortable feeling. There
              | was no possibility that keel would come off by itself even if all the
              | bolts failed.
              |
              | The keel had to come off so the boat could be shipped."
              |
              |
              | Mat
              |
              |
              |
              |
              |
              |
              |
              | Bolger rules!!!
              | - no cursing, flaming, trolling, spamming, or flogging dead horses
              | - pls take "personals" off-list, stay on topic, and punctuate
              | - add your comments at the TOP and SIGN your posts, snip all you like
              | - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
              01930, Fax: (978) 282-1349
              | - Unsubscribe: bolger-unsubscribe@yahoogroups.com
              |
              | Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
              |
              |
            • ravenous@gate.net
              ... JB, You are exactly right. ... BTW, the 316 SS bolts were in perfect shape even after 15 years of blue water cruising. The 5200 kept any possibility of
              Message 6 of 17 , Dec 3, 2001
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                "John Bell" <jmbell@m...> wrote:
                >Chiming in late here...
                >I suspect this story leaves something out: Could it have been the
                >keelbolts had been removed for some type of repair? But because the
                >keel had been bedded in 5200, it did not fall off right away without
                >some persuasion.

                JB,
                You are exactly right.
                The rest of Glenn Ashmore's post:
                --------------------
                BTW, the 316 SS bolts were in perfect shape even after 15 years of
                blue water cruising. The 5200 kept any possibility of sea water
                reaching the them. The keel had to come off so the boat could be
                shipped.
                ----------------------------------
                Rhett, the soon to be "Other AF4 Owner in Georgia"
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