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Re: [bolger] Double Bottom on Martha Jane.

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  • Mark Albanese
    Col, When I promoted single sheets I was thinking of something thinner than 1 . But for you: 2. Good scarfs are always stronger than the wood. 1. From the
    Message 1 of 4 , Sep 4, 2000
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      Col,

      When I promoted single sheets I was thinking of something
      thinner than 1". But for you:

      2. Good scarfs are always stronger than the wood.

      1. From the study plan, I can see that the curve in MJ's
      belly is very gentle. The worst is in that 6' section under
      and just behind the tanks. The bottom's almost straight
      apart from that. 1" sheets fulcrummed at the deepest part of
      the hull would surely work the long way, if they were wide
      enough. Since you have to lay them athwartships, right there
      they might be a little too stiff.

      It would save A LOT of work, though, if you can get away
      with it. This makes it sound more complicated than it will
      probably be, but to get any needed extra leverage for the 4"
      rise beyond the tanks, you could either fasten temporary
      levers or make up an 8' x 8' sheet of ply. Patience and some
      warm water might make all the difference.

      Why not spring for a sheet of cheap stuff to play around
      with? Generations of builders could be in your debt.

      ( Another not quite so elegant idea is to use the 1" sheets
      in the straighter parts of the bottom and only laminate with
      thinner stuff between . )

      Whadaya think?

      Mark



      col_mooney@... wrote:
      >
      > Just a quick question that has been bugging me about double
      > bottoms, on boats such as Micro, Long Micro, Martha Jane etc. In the
      > earlier discussion about doubling the bottom ply someone asked "why
      > not just one thicker sheet?" I may have missed the reply if there
      > was one.
      > I'd planned to double sheet my MJ, as I figured the generous
      > offcuts would be useable elsewhere on the boat, which I figured was
      > one of Phils reasons. Then I thought I'd be clever and save time,
      > glue and maybe money by using one layer of inch thick. Should I or
      > should I not use 1 inch sheets to make the bottom? The only possible
      > drawbacks I can think of, which may or may not be valid, are:
      > 1. The 1" solid piece will not curve around to meet the sides,
      > 2. Traditional scarf joints are not suitable.(although on my
      > 16ft sailing dory with considerable rocker this method was used - 9ml
      > bottom - seems fine)
      >
      > Are there any other drawbacks I may have missed? Any imput to help
      > me solve my dilemma would be appreciated.
      >
      > Regards,
      > Col
      >
      > Bolger rules!!!
      > - no cursing
      > - stay on topic
      > - use punctuation
      > - add your comments at the TOP and SIGN your posts
      > - add some content: send "thanks!" and "ditto!" posts off-list.
    • hwal@aol.com
      Col - When you use 1/2 inch instead of 1 inch - it s easier to get the curve - and you will have overlapping seams - which means you won t be relying only on
      Message 2 of 4 , Sep 4, 2000
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        Col - When you use 1/2 inch instead of 1 inch - it's easier to get the curve
        - and you will have overlapping seams - which means you won't be relying only
        on your cloth for a water tight seal and you will have greater strength at
        the joints and you will have more laminations. What scarfs by the way? There
        are no scarfs on the bottom. The plywood joints are butted but offset from
        the lower layer. Steve ( mj Landroval)

        ps

        my sponsons and new rudders will be finished and painted today. A good
        feeling.
      • Mark Albanese
        ... I had the thought that, apart from maybe being the only way to take a curve, the advantage of double layered bottoms might be to protect against the poor
        Message 3 of 4 , Sep 4, 2000
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          Mark Albanese wrote:
          >
          >
          > Col,
          >
          > When I promoted single sheets I was thinking of something
          > thinner than 1". But for you:
          >
          > 2. Good scarfs are always stronger than the wood.
          >
          > 1. From the study plan, I can see that the curve in MJ's
          > belly is very gentle. The worst is in that 6' section under
          > and just behind the tanks. The bottom's almost straight
          > apart from that. 1" sheets fulcrummed at the deepest part of
          > the hull would surely work the long way, if they were wide
          > enough. Since you have to lay them athwartships, right there
          > they might be a little too stiff.
          >
          > It would save A LOT of work, though, if you can get away
          > with it. This makes it sound more complicated than it will
          > probably be, but to get any needed extra leverage for the 4"
          > rise beyond the tanks, you could either fasten temporary
          > levers or make up an 8' x 8' sheet of ply. Patience and some
          > warm water might make all the difference.
          >
          > Why not spring for a sheet of cheap stuff to play around
          > with? Generations of builders could be in your debt.
          >
          > ( Another not quite so elegant idea is to use the 1" sheets
          > in the straighter parts of the bottom and only laminate with
          > thinner stuff between . )
          >
          > Whadaya think?
          >
          > Mark
          >
          > col_mooney@... wrote:
          > >
          > > Just a quick question that has been bugging me about double
          > > bottoms, on boats such as Micro, Long Micro, Martha Jane etc. In the
          > > earlier discussion about doubling the bottom ply someone asked "why
          > > not just one thicker sheet?" I may have missed the reply if there
          > > was one.
          > > I'd planned to double sheet my MJ, as I figured the generous
          > > offcuts would be useable elsewhere on the boat, which I figured was
          > > one of Phils reasons. Then I thought I'd be clever and save time,
          > > glue and maybe money by using one layer of inch thick. Should I or
          > > should I not use 1 inch sheets to make the bottom? The only possible
          > > drawbacks I can think of, which may or may not be valid, are:
          > > 1. The 1" solid piece will not curve around to meet the sides,
          > > 2. Traditional scarf joints are not suitable.(although on my
          > > 16ft sailing dory with considerable rocker this method was used - 9ml
          > > bottom - seems fine)
          > >
          I had the thought that, apart from maybe being the only way
          to take a curve, the advantage of double layered bottoms
          might be to protect against the poor quality of cheaper
          plywood. Sort of a way to distribute the voids.

          Mark
        • col_mooney@globalfreeway.com.au
          - Mark and Steve, Thanks for the imput, lots of food for thought there. I ll brainstorm it a bit more yet, but the pros seem to be outweighing the cons at
          Message 4 of 4 , Sep 5, 2000
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            -

            Mark and Steve,
            Thanks for the imput, lots of food for thought
            there. I'll brainstorm it a bit more yet, but the pros seem to be
            outweighing the cons at this stage. Wastage would not be so bad with
            the offcuts, the leeboards and rudders on the revised plans have to
            be built up to 2 inches and 1 & 1/2 inches rom memory.(only got them
            yesterday) Being the cheapskate that I am, I thought at least on the
            leeboards I'd have a full sheet for the outsides and offcuts of the
            inch sheets cut to fill in the middle.
            Compliments to Mr B by the way on those leeboards,
            thought they were quite brilliant.

            Col

            -- In bolger@egroups.com, Mark Albanese <marka@o...> wrote:
            > Mark Albanese wrote:
            > >
            > >
            > > Col,
            > >
            > > When I promoted single sheets I was thinking of something
            > > thinner than 1". But for you:
            > >
            > > 2. Good scarfs are always stronger than the wood.
            > >
            > > 1. From the study plan, I can see that the curve in MJ's
            > > belly is very gentle. The worst is in that 6' section under
            > > and just behind the tanks. The bottom's almost straight
            > > apart from that. 1" sheets fulcrummed at the deepest part of
            > > the hull would surely work the long way, if they were wide
            > > enough. Since you have to lay them athwartships, right there
            > > they might be a little too stiff.
            > >
            > > It would save A LOT of work, though, if you can get away
            > > with it. This makes it sound more complicated than it will
            > > probably be, but to get any needed extra leverage for the 4"
            > > rise beyond the tanks, you could either fasten temporary
            > > levers or make up an 8' x 8' sheet of ply. Patience and some
            > > warm water might make all the difference.
            > >
            > > Why not spring for a sheet of cheap stuff to play around
            > > with? Generations of builders could be in your debt.
            > >
            > > ( Another not quite so elegant idea is to use the 1" sheets
            > > in the straighter parts of the bottom and only laminate with
            > > thinner stuff between . )
            > >
            > > Whadaya think?
            > >
            > > Mark
            > >
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