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Epoxy Resin or Polyester Resin

R

RAMAnnino

New member
What is better? should I use West Marine Epoxy resin or polyester resin. The epoxy is more expensive but if it will be easier to work with and last longer than would be worth it in my opinion. I have a 5 foot by 5 foot section and i am replacing about 5 foot piece of my stringer. How much resin would I need as an estimate. Thanks for the help.
 
RAMAnnino said:
What is better? should I use West Marine Epoxy resin or polyester resin. The epoxy is more expensive but if it will be easier to work with and last longer than would be worth it in my opinion. I have a 5 foot by 5 foot section and i am replacing about 5 foot piece of my stringer. How much resin would I need as an estimate. Thanks for the help.
Click to expand...

Epoxy is better but poly will do the job for what you're doing. If you go with epoxy, I would recommend US Composites as it's less expensive than West Marine. An estimate would be hard to give no knowing what fiberglass and resin you're using but a "rough" guess is around 1/2 gallon or less.
 
I'm an epoxy guy too. I have used both West System and the US Composites epoxy with success. Like said above, the US Composites is quite a bit cheaper. Make sure you get a pump kit with whatever epoxy you choose, they make getting the correct ratio a breeze.
 
i like epoxy too - like the west system stuff - works very well, but poly is alot cheaper if you are doing a big area.
 
Ditto everything that's already been said about epoxy being better. I also agree with buying from US Composites. While it's not my favorite epoxy it is certainly adequate and costs much less than any other I've found that will do the job. (The best epoxy I've ever used is made in Germany - MGS - and costs somewhere around $150 per gallon. West Systems is also very good epoxy to work with.)

Epoxy absorbs less than 1/10 as much water as polyester resins. It also forms much better secondary (mechanical) bonds to existing fiberglass than polyester resins, making it superior for repairs.
 
That's one of the most contentiuos questions on many of thr boat restoration/ building sites I've been to.

Makes sense that there would be some contention, since manufacturers use poly-/vinylester, the obvious question would be ... "If it's good enough for the manufacturer, why isn't it good enough for me." One retort to that seems to be that poly has a good initial bond, but not as good a secondary bond. On the flip side, the poly advocates state that epoxy can't be gelcoated and requires extensive prep to paint.

So, my own conclusion is that I would use epoxy for structural repairs and poly for any area (above the waterline) that needs to be gelcoated or painted.
 
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