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#1
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Polyester or Epoxy?
experience varies. on some surfaces polyester is fine. some builders have
been using is successfully for decades. but as there is no experimental data a lot of builders pay extra and use epoxy. if your designer recommends polyester you might want to contact him or her to find out what feedback he is getting from builders. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned |
#2
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Polyester or Epoxy?
Allan,
Thirty five years ago, when epoxy was hundreds of dollars a gallon, we used poly for glassing, never as an adhesive (it was not as strong as a good glue). The general consensus of the experts was that It should only be used for glassing on a virgin, stable, substrate which was mostly plywood back then. NEVER on planking, strips, etc or previously painted wood, because the bonding strength and sheer strength would not hold up to the forces which resulted in the expansion of these substrates or the poor penetration of the previously painted surface. The first coat of poly was thinned with styrene (the base solvent of polyester) 30% as I recall, immediately followed by a straight coat that the glass was laid into. The rest of the buildup was as with epoxy except you had to work your ass off if the job was of any size. This method worked ok and some of it lasted at least several decades. The ones that failed were usually the ones that violated the rules above or were boats that were grossly mistreated. For instance, acetone was substituted for styrene which reduced the mechanicals of the poly by about 20% to 30% as I recall. About the same time I was introduced to epoxy in the lab at GE (they could afford it). For the next twenty or so years I waited for the price of epoxy to come down to my recreational budget level. That was about 15 years ago and I have not used poly since. As far as I am concerned, the only justification for poly is in high volume production molded parts (unfortunately like boat hulls). But even there you will see the highest quality products using epoxy. Bottom line. With epoxy at $40 to $50 a gallon, I wouldn't use poly if it were FREE! My opinion, worth what you paid for it. Regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. |
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