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Re: [boatdesign] Re: Epoxy/Polyester

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  • Bradley Davis
    Hey guys, I stumbled across this web resource yesterday, it seems like something you all may be interested in. There are many sites dedicated to offering
    Message 1 of 9 , Dec 5, 2012
      Hey guys,

      I stumbled across this web resource yesterday, it seems like something you all may be interested in. There are many sites dedicated to offering educational lecture videos for free... MIT, Stanford, for example have one. I use Khan Academy as well.

      This link is specifically for ship / boat building:


      And this one gets more into the motion and control of ships / boats:


      I hope you find this as useful as I did! Tons of information, I'll probably not get through it all.


      On Sat, Oct 20, 2012 at 11:41 AM, nutty_boats <nutty_boats@...> wrote:


      --- In boatdesign@yahoogroups.com, "Carel Ruysink" <c.ruysink@...> wrote:
      > As an architect I learned at university no material is 100% waterproof or watertight, it is resistant and/or repellant and you can adress a number to it and epoxy has a very high number, much more than polyester.

      I would amend that statement to say that no coating is 100% waterproof.

      A few years ago I read studies that others had done (they had better test equipment than I) that showed that two or more layers (it must be at least two layers, as one layer opens holes as it soaks into the wood, the second layer plugs those holes) of sealer equals or exceeds the water resistance of epoxy. I do not remember where I found those articles, so would have to google them to find them again.

      > From what I have seen, sealers do always fail at the end or much earlie,r sealers fail when scratched or rubbed down. Do not trust them as the only barrier.

      Epoxy encapsulation fails for the same reasons given here. Where epoxy is superior is when it is part of a fiber/epoxy combination surface treatment. The right fabric soaked into an additional layer of paint should provide a similar resistance to abrasion.

      > Impregnating (thin) epoxy is very much more dependable.
      > Epoxy needs indeed a UV barrier or it will fail within ten years.
      > Epoxy is the best intermediate as it comes down to strength, resilience to impact and movement, it strenthens the wood it impregnates and it is with great distance the best intermediate with Kevlar and/or carbonfibre.
      > In aircraftindustry and highperformance boatbuilding polyester has been abandoned for decades over epoxy and that has nothing to do with fetishism or shortsightedness.
      > The specs of epoxy are much better for high performance.

      You are comparing epoxy with polyester, not sealer/primer.

      > But in the end it is up to you what you choose and what your goal is. Polyester is not bad. I have seen "boats" built from cheap cupboardpanels and painted with interior wallpaint. It did last a whole season.

      Others beside myself have claimed that they get results with a good sealer/primer (two coats) finished with a good exterior paint that equals epoxy encapsulation, results that can last a decade or more.

      > But for serious work I always choose epoxy, the extra money is after two months forgotten and the pleasure from a "state of the art" boat will last for years. (and often pays itself back in less and/or easier maintanance).
      > Carel
      > ps; everybody has his own favorite materials wich work fine for him and other materials he never will learn to like. But with epoxy let the specs convince you (compared to anything else).
      In the end, it is what the builder thinks is the best material for the job and/or what he is most comfortable with. The choice is yours, and I will not criticize the choice you make.

      T. Lee.

      Bradley Davis

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