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polyester vs epoxy?

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  • shoalwater1
    Okay, if you think I m making a big mistake with this one, please tell me now, and why. A friend owns a factory, and does a lot of fiberglass work in polyester
    Message 1 of 5 , Sep 29, 2002
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      Okay, if you think I'm making a big mistake with this one, please
      tell me now, and why.

      A friend owns a factory, and does a lot of fiberglass work in
      polyester resin.

      I was planning on using epoxy on my boat, but I can get such a good
      deal on polyester that I'm considering it.

      What is the performance difference? Enough to deter me? I can get
      really good quality polyester resin for 10$ a gallon.

      What will the lifespan difference be? Weight? durability?

      If I use PL for the adhesive, will it conflict with polyester resin?

      ???????????

      Polyester gets a bad rap alot these days.

      Steve
    • Larry Whited
      I ve never been a fan of polyester in the context of sealing playwood. To me, anything worth my time is worth putting a waterproof coating on. Poly adhers to
      Message 2 of 5 , Sep 30, 2002
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        I've never been a fan of polyester in the context of sealing playwood. To me, anything worth my time is worth putting a waterproof coating on. Poly adhers to wood ok but for pure water resistance I think you would be ahead with exterior latex house paint. If your going down and dirty taped seems and polyester resin will work. Then just paint it with house paint. I've heard a lot of good things about the lasting qualities of exterior latex. OTH, if you want the moisture content of the wood to be stablelized through epoxy saturation on both sides, that's the only way to really achieve it. Obviously epoxy joints are much stronger. Polyester compounds like bondo or boat repair polyester fillers are hydrophylic. The work fine on a poly boat that is sealed with either gelcoat or a two part polyuethane paint job. Also remember that polyester won't adher to epoxy. Take a look at Noah's marine under epoxy's East System is much cheaper and probably a reasonable compromise.
        http://www.noahsmarine.com/United_States/Epoxies-us/epoxies-us.html
        That's my two cents.
        Larry
        shoalwater1 wrote:Okay, if you think I'm making a big mistake with this one, please
        tell me now, and why.

        A friend owns a factory, and does a lot of fiberglass work in
        polyester resin.

        I was planning on using epoxy on my boat, but I can get such a good
        deal on polyester that I'm considering it.

        What is the performance difference? Enough to deter me? I can get
        really good quality polyester resin for 10$ a gallon.

        What will the lifespan difference be? Weight? durability?

        If I use PL for the adhesive, will it conflict with polyester resin?

        ???????????

        Polyester gets a bad rap alot these days.

        Steve


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      • Lincoln Ross
        I suggest one possibility is Raka. Pretty cheap compared to West, and works just fine. ON a small boat, the cost difference will not be large, as epoxy can be
        Message 3 of 5 , Sep 30, 2002
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          I suggest one possibility is Raka. Pretty cheap compared to West, and
          works just fine. ON a small boat, the cost difference will not be
          large, as epoxy can be only $40 a gallon or so.
          see below
          --- In Michalak@y..., Larry Whited <lwhited@y...> wrote:
          >
          > I've never been a fan of polyester in the context of sealing
          >plywood. To me, anything worth my time is worth putting a waterproof
          >coating on. Poly adhers to wood ok

          Not on my boat! Peeled right off. Also, I took over a couple of
          projects that had polyester tape and had been left in the weather a
          bit. Peeled right off them too! Have heard this from other people too.
          I suppose if you used polyester without wax and always kept the boat
          indoors, you might get away with it.

          I concur with the rest of the post

          snip
        • egiajack
          ... There is a good reason why polyester gets a bad rap. At a microscopic level, polyester hardens in long linear chains which are far enough apart to allow
          Message 4 of 5 , Sep 30, 2002
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            > Polyester gets a bad rap alot these days.
            >
            > Steve

            There is a good reason why polyester gets a bad rap. At a
            microscopic level, polyester hardens in long linear chains which are
            far enough apart to allow water molecules to slowly work their way
            through it. To prevent this, most production boats use gelcoat as
            the outer layer because gelcoat is much more water resistant (notice
            I didn't say waterproof). When applied to wood, polyester will still
            allow enough water through to affect the stability of the wood,
            causing it to swell, contract, swell, contract, and over time the
            polyester will "let go" of the wood. Then it will trap water between
            the resin/fiberglass and the wood, and before you can say "Davey
            Jones' Locker", the whole thing has turned into a rotting stinking
            mess.

            Now there are some advocates of polyester, including Mr. "Instant
            Boats" Payson, and Mr. Michalak. For those that plan to keep their
            boats in a dry barn, it could work. Sometimes the planets align
            correctly during application and it will last for years, even in the
            water. However, I've personally seen too many disasters to recommend
            it. Epoxy is more expensive, but you get what you pay for.

            For all my doom and gloom, it really comes down to what you want and
            how long you want it to last. If you want to just get on the water,
            build it from ACX and paint it with External Latex. If you want it
            to last, put more money into it.

            Jack
          • Ashley
            ... I m working on Jim s latest design, Dorado, at the moment. Jim specifies epoxy for the fillets, taping and hull glass sheathing. This is Jim s highest
            Message 5 of 5 , Sep 30, 2002
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              --- In Michalak@y..., "egiajack" <jgclayt@e...> wrote:
              >
              > Now there are some advocates of polyester, including Mr. "Instant
              > Boats" Payson, and Mr. Michalak. For those that plan to keep their
              > boats in a dry barn, it could work. Sometimes the planets align


              I'm working on Jim's latest design, Dorado, at the moment. Jim
              specifies epoxy for the fillets, taping and hull glass sheathing.
              This is Jim's highest powered design so far, with 30 hp max. Much
              more hull integrity is required for the greater hull forces at speed.


              > Epoxy is more expensive, but you get what you pay for.
              >
              > If you want it to last, put more money into it.
              >

              I agree. But for me, it's a no brainer if the difference in cost is
              only $30/gallon. This is a small part of the cost in a boat, and
              really doesn't change the completed cost much at all. I'd go for
              integrity every time.

              Regards,
              Ashley

              PS I'll post pics of Dorado soon - haven't taken any yet, coz its
              just a plie of parts right now. Hopefully hull assembled by end of
              the week. Plans will be available soon from Jim.
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