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Re: 630

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  • Eric
    I thoroughly agree about the stiffness argument. If stiffness is wanted, laminate from plywood. I will second Bruce Hallman s reference to Buhler. If using
    Message 1 of 25 , Aug 28, 2010
      I thoroughly agree about the stiffness argument. If stiffness is wanted, laminate from plywood.

      I will second Bruce Hallman's reference to Buhler.
      If using dimensional lumber use water resistant glue, plain old bedding compound or asphalt tar. Asphalt tar is cheap and will act like glue once it sets up. I have experience using epoxy on dimensional lumber and have seen 3/8" * 4" 8* 26' walnut (relatively stable with moisture changes) shake off its 4" wide glue line because of moisture cycling. I've seen epoxy used on big keel pieces by professionals who also bolted everything together as if the epoxy were bedding compound. I think they were asking for trouble and should have just used bedding compound or asphalt tar. Epoxy is great stuff for cold molding and fiberglassing. It is not great stuff for gluing dimensional lumber. It is an inappropriate use.

      By the way, epoxy is water proof, but not moisture proof. Moisture will penetrate and it will condense in voids in plywood if it can penetrate the plywood and if the plywood has voids and if the temperature of the plywood is below the dew point. It will not exit as easily as it enters. Anyone had any experience with this? I am unclear about how well moisture will penetrate plywood.
      Eric


      --- In bolger@yahoogroups.com, Rick Bedard <sctree@...> wrote:
      >
      > I think if the 3" thick shoe was laminated from six courses of 1/2" ply it would
      > hold it's shape and add to the hull stiffness. I don't think two courses of 2x
      > material would.. Also the shrinking of green lumber or the swelling on dry would
      > cause havoc with two courses at 1.5" each sharing a single glueline.
      >
      > BUT... I've never tried it, so what do I know.....
      >
      > Rick
      >
      >
      >
      > ________________________________
      > From: Bruce Hallman <hallman@...>
      > To: bolger@yahoogroups.com
      > Sent: Fri, August 27, 2010 8:38:10 AM
      > Subject: Re: [bolger] 630
      >
      > On Thu, Aug 26, 2010 at 9:30 PM, <shortdottedline@...> wrote:
      > >
      > > not sure using dumentional lumber for the shoe for the 630 would work, The 1/2
      > >in ply will conform to the rocker of the bottom, while lumber be it 2 X 4s etc
      > >would conform and be difficult to make it solid. The idea of using treated stuff
      > >makes sense,, ed (I am the one Phill designed 630 for)
      >
      >
      > Fair concern. According to my math, the total rocker in the
      > 'Illinois' bottom is about 12 inches spread over the 51 foot long
      > length. That is relatively flat.
      >
      > I am pretty sure that if you picked up a 50 foot long piece of
      > "two-by" lumber by its middle, that it would sag under its own weight
      > by much more than the 12" of needed bend.
      >
      > The shoe of the design 630 'Illinois' is 3 inch thick. I had imagined
      > that you could laminate two courses of standard "two-by" lumber which
      > is 1 1/2" thick, staggering the joints. You could also scarf the
      > joints, but that would not add much strength worth the extra trouble
      > in my opinion.
      >
      >
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