Polyester vs Epoxy resin to repair tops

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Dec 28, 2019
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Peoria, Illinois
The P.O. installed a sun roof and now I want to fill it in with some new glass, but I am unsure of what type of resin to use. Epoxy resin or Polyester? Any suggestions?
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smtdvm

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I just did mine. I’ve worked with both, in fact I started with epoxy and ended up starting over with polyester. I’m glad I did. I ended up reglassing both sides of my roof. I was astounded in the end that I went through four gallons of resin, which up here anyway, is over fifty bucks a gallon, plus methyl ethyl ketone catalyst. West System epoxy was about $110 per gallon plus more expensive catalysts. There are also compatibility issues when it comes to finishing, gel coat,etc.
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AussieHJCruza

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Epoxy resin has better adhesive properties, tensile strength and stiffness, resistance to micro-cracking and fatigue and more resistant to degradation from water ingress, ie. osmosis.
However, for the top of a 40, a basic polyester would be absolutely fine - structural FRP is my day job and quite frankly, very rarely do we need to go to an epoxy resin, in 90+ % of situations, a polyester or vinyl ester resin is suitable and besides, polyester resin and MEKP catalyst will be the most budget-friendly
 
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Aug 4, 2009
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New Hampshire
 
 
I just did mine. I’ve worked with both, in fact I started with epoxy and ended up starting over with polyester. I’m glad I did. I ended up reglassing both sides of my roof. I was astounded in the end that I went through four gallons of resin, which up here anyway, is over fifty bucks a gallon, plus methyl ethyl ketone catalyst. West System epoxy was about $110 per gallon plus more expensive catalysts. There are also compatibility issues when it comes to finishing, gel coat,etc.View attachment 2263429
that top must weigh a ton now.
 

smtdvm

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Juneau, Alaska
that top must weigh a ton now.
My thought too. But it eliminates the need for a roll cage. Seriously, yes, it’s a little heavier but still pretty manageable and very strong. No oil canning. I can stand on top, no problem. With a small outboard motor clamped on, it doubles as a small boat
 
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Epoxy resin has better adhesive properties, tensile strength and stiffness, resistance to micro-cracking and fatigue and more resistant to degradation from water ingress, ie. osmosis.
However, for the top of a 40, a basic polyester would be absolutely fine - structural FRP is my day job and quite frankly, very rarely do we need to go to an epoxy resin, in 90+ % of situations, a polyester or vinyl ester resin is suitable and besides, polyester resin and MEKP catalyst will be the most budget-friendly
Basically what I was going to say.
I have used both and think epoxy is best but is more expensive.
I did repairs on the targa top on my X19 and polyester wouldn't adhere where the epoxy stuck right off.
Did some work on the fj40 top and polyester worked fine.
The Land cruiser tops are probably a polyester as Epoxy wasn't on the market 40 years ago.
If you use epoxy then that is what you will have to use from that point on.
Epoxy will stick to polyester but polyester will not stick to epoxy.
 
Joined
Dec 28, 2019
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Peoria, Illinois
Thanks for the great information.
What about brands? In the boating community, West Systems is the go to, but it is a bit spendy. Anyone have an alternative? I’ve been reading a bit on TotalBoat and it is cheaper and in the boating community it has been getting decent product reviews. Anyone have any experience with that brand?
 
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