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Great questions, will try to explain better.
Polyester resins from basic boatyard resin to casting resins, can come in many formulas. A blend for winter work, summer heat, super clear for casting tables, for surfboards. Some very hardened so on.
If building a hull with Kevlar cloth you need a resin that has memory qualities…that is if bent when in the cloth it will bend a % and then come back to its original shape without cracking.
Hence the word fiber Glass.
Vinylester resins can have this quality. As epoxy resins if you get these blends.
If you have a resin that cures very hard it will pop out of a Kevlar weave .
The best resins start with epoxy at the top of the chain and then it’s vinylester and down to polyester resin.
Blisters that you see and hear about today are mostly caused by bad shop working conditions when doing old school open molding. That’s hand layup. Dust particle gets on top of the gel coated surface and when hand laid up if not properly rolled out can cause microscopic air holes which water can then migrate into causing a blister.
Using a bottom line polyester gelcoat combined with a dusty dirty shop and casual work standards can make for blisters to come.
Now using vinylester resin or epoxy resin does not guarantee and perfect hull skin. You have to continually check the quality of the manufactures resin against its spec sheet daily. I can write a chapter here about my time dealing with top of the line resins and gelcoat companies.
So…I have always felt that if building by open molding if your build is properly laid up by hand a polyester build like I wrote above will most likely out live all you guys in your 20s.
Now if built properly a vinylester resin build if built to the same above standards will do the same but with a slight advantage being a tighter molecular blend that will inhibit water absorption. If using a blend that has good memory which is a good characteristic of some vinylester blends than you would have a hull if built in core that could be a more long term resilient hull to much abuse.
Ok, epoxy resins… I built a racing trimaran 10 years ago using The top of the line Systems Three epoxy blend that had to be post cured. It cost over $100.00 a gal. Inadequate to build an oven over the entire 34’x26’ boat and cure it with heat to120 degrees for 4 hours. This boat weighed all up, sails, mast, motor everything 3500 lbs. I went through a major gale in it at sea. Amazing how strong it was for the thin skins used. It was an Ian Farrier design.
If money was no object then epoxy is the way to go if you can handle the skin issues.
It’s very technical as it has to be mixed to .01% tolerance.
When I look at old 30-40 + year old polyester boats that I am repairing I get to see all there insides, by removing hardware. The world today has a glut of polyester boats that if left in a swamp or sunk in front of your waterfront house will never go away. It’s just amazing stuff. It can only be ground up to be put in a land fill.
To me the bottom line is ..proper job, good up keep = super long life.
But we are guys and we like cool stuff.
Well said. The key is quality materials be it poly, vinyl, or epoxy and a quality lamination using said materials. I think a lot of folks think of poly as a bad choice because so many mass produced chop gun built boats using inferior resins and under qualified help.
 
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