Epoxy vs. Resin

[Matt1121]

Hi Gents-

I've been reading alot threads where most of you guys have been using epoxy for repairs, instead of traditional resin. My question is....is there any sort of compatibility issue with using epoxy based products with boats that are made out of polyester and/or vinylester resin. One would think that you should use the same type of resin that the boat is made out of, right?

I understand that epoxy seeps better into wood and therefore better encapsulates it from moisture but I have also heard that the mixture needs to be exactly right and the it is much more expensive.

If it (epoxy) is a much better product for boat building, are there any high end builders using it?

[EBEACH]

Yes, there are compatibility issues. You can repair polyester and vinylester with epoxy, but you can’t repair epoxy with polyester or vinylester. Gel coat is a polyester product, so if you want to gel coat you will need to apply over poly not epoxy.

Epoxy is better suited for structural purposes, but is WAY more expensive. When I re-do my transom, I will use epoxy for the inside, and then the last layer will be done with vinylester. Vinlyester is stronger than polyester. Epoxy will give me a lot more time to work before it sets up. I’ll need that when trying to handle sheets of plywood and screw it all together.

Don Herman said somewhere here to go ahead and use polyester for everything. I think it all comes down to opinion and your wallet. Poly will absorb water where as epoxy won’t. Don’t know about what boat builders are using. I'm sure others have more to add.

[Matt1121]

Thanks EBEACH. I kinda thought there might be some compatability issues.

My buddy who owns a restoration shop thinks along the same lines as Don Herman. He only uses polyester or vinylester. He also disagrees with several of the repair techniques mentioned in the West System repair guide.

[Scott]

Ed ....I think EBEACH might be referring to the post I had on re-coring the decks ...... I went with Vinylester ..... no real reason .... I've been using epoxy , wanted to try something different. The Guys up at LBI in CT also recommended poly and better yet vinyl so I gave it a shot .....not bad to work with ....you can control how quick it "flashes" and its slightly less expensive ( shipping/haz mat. charges kill you on this stuff!!!)..... The poly/vinyl resins also complexes and chemically bonds and form a stronger bond when using fiberglass MAT ...epoxy does not dissolve the binding material in the mat....Working inside with the resin definitely requires a respirator ....Bottom line everyone’s boat here was built using this stuff

[FELLOW-SHIP]

GREAT QUESTION
AGAIN NOT A EASY ANSWER WILL HAVE TO DO WITH YOU, AND YOUR ABILITIES, EXPERIENCE, PREFERENCES, AND GOALS. FOR ME I LIKE EPOXY LETS CALL IT
“BOAT BUILDING FOR DUMMIES RESIN” THE STUFF IS USER FRIENDLY BECAUSE OF THE AMOUNT OF TIME YOU HAVE TO WORK WITH THE STUFF BEFORE IT STARTS TO HARDEN. ON MY BOAT THE FIRST RESIN JOB WAS TO FIBERGLASS / RESIN THE BELOW DECK AREA WHERE THE GAS TANK RESTS ON. I CUT THE PLYWOOD 30” X 8 ‘ PUT IT ON SAW HORSES BOUGHT A FEW GAL OF POLYESTER FOR ABOUT $12 A CAN AND I’M OFF TO THE RACES. NOW YOU GOT TO REMEMBER THIS IS A ONE MAN JOB THE ONLY HELP I GOT WAS WHEN I CALLED MY BROTHER FOR A FEW HRS IF IT WAS IMPOSSIBLE FOR ONE GUY TO DO IT LIKE REMOVING THE CAP, I EVEN DID THE TRANSOM SOLO. BETWEEN MIXING, POURING, SPREADING, AND PUTTING ONE LAYER OF GLASS “JUST IN CASE” ON THE PLYWOOD IT WAS A RACE OF TIME AND QUALITY JUST TO GET THE STUFF ON EVENLY AND THIS WAS JUST A NARROW SHEET OF PLYWOOD. MY ANXIETY LEVEL WAS WAY UP THERE BECAUSE ON THE TIME ELEMENT THUS THE QUALITY OF JOB SUFFERED. NOW I KNOW WHY THE BOAT BUILDERS SPRAY THE STUFF AND THEN VACUUM BAG THEIR WORK PLUS USING A CRU TO DO IT SIDE A WAREHOUSE. AFTER THIS I DECIDED THAT IF I WAS GOING TO GET A GOOD JOB I NEEDED THE TIME EPOXY WOULD PROVIDE ME PLUS I WAS GOING TO PAINT THE INSIDE AND OUT OF THE BOAT ANYWAY. AS FOR THE COST I USED ABOUT 15 GAL OF EPOXY TO DO EVERYTHING. THERE ARE OTHER BRANDS OTHER THAN WEST AND YOU CAN BUY IT IN LARGER QUANTITIES THAT 1 GAL SIZE. IF I WAS GOING TO DO IT OVER AGAIN FOR MY OWN BOAT I STILL WOULD USE EPOXY PROBABLY A CHEAPER MANUFACTURER. IF I WAS GOING THIS FOR A LIVING SELLING MY WORK AND WANTING TO MAKE A PROFIT I WOULD USE A CHEAPER RESIN.
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[FELLOW-SHIP]

MY PREVIOUS POST I DIDN’T MENTION ALL THE OTHER QUALITIES OF EPOXY LIKE ITS ABILITY TO ADHERE TO OLDER RESIN AND ITS ABILITY TO SEEP INTO PLYWOOD AND USING DIFFERENT TYPES OF FILLERS IN IT TO GET FAIRING OR BONDING QUALITIES THERE ARE A NUMBER OF OTHER REASONS WHY IT IS A VERY GOOD RESIN TO USE.
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[Jon G]

I'm a big epoxy fan, they both have there place but I really like mixing the epoxy with pumps, no guess work just pump and stir. It is pricey when compared to regular resin though.