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Old 18 June 2006, 12:12   #1
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Epoxy / fibreglaas question

Help! I have primed some plywood with SP epoxy, then given it a few layers of glass mat with standard polyester resin. The stuff on top (grp) has cured ok, but it looks like the layer that was next to the epoxy is still goo. Does anyone know if newish epoxy will react with the polyester resin (maybe the styrene?) I am wondering if I should get the grinder out now and remove it or give it more time to go off. Any advice from experienced boat builders / laminators would go down a treat! Thanks Jack
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Old 18 June 2006, 15:37   #2
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you should really have left the epoxy to fully cure before applying polyester.
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Old 19 June 2006, 04:27   #3
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I'm no expert but I have always been told that you can apply epoxy over polyester but not polyester over epoxy. I've also heard that if you sand the epoxy well, the polyester will adhere but I have also heard of many failed atempts. If there are no experts out there I will try to get more info and do another post.
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Old 19 June 2006, 12:22   #4
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start over. use an additive to help stick to the wood.
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Old 19 June 2006, 13:52   #5
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Quote:
Originally Posted by Channelwatch
. If there are no experts out there I will try to get more info and do another post.
the post above yours was from an expert, but he's a hardboater so can he be trusted that's the question?
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Old 19 June 2006, 13:53   #6
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A norvern hardboater of all things!
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Old 20 June 2006, 18:58   #7
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Quote:
Originally Posted by Channelwatch
. If there are no experts out there I will try to get more info and do another post.

Quote:
Originally Posted by Rogue Wave
the post above yours was from an expert, but he's a hardboater so can he be trusted that's the question?
Well, our fleet consists of both hard and soft boats so I would be inclined to at least 1/2 trust his advice. So is there any truth to "its ok to use epoxy over polyester but not polyester over epoxy"? Any tricks, other than letting the epoxy fully cure, to getting polyester to adhere to epoxy?
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Old 20 June 2006, 19:11   #8
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Quote:
Originally Posted by Channelwatch
Quote:
Originally Posted by Channelwatch
. If there are no experts out there I will try to get more info and do another post.



Well, our fleet consists of both hard and soft boats so I would be inclined to at least 1/2 trust his advice. So is there any truth to "its ok to use epoxy over polyester but not polyester over epoxy"? Any tricks, other than letting the epoxy fully cure, to getting polyester to adhere to epoxy?

i have heard the saying........ but .... its not correct! however epoxy needs to be fully cured and keyed before applying polyester. the difference between the two i can only imagine is the amount of shrinkage with polyester over zero shrinkage with epoxy.....
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