Mike,
You've got the opinions of two professionals, I'll add the opinion of an amateur that's done a little research and played with both resins.

Poly is "good enough", epoxy is better. Why? For an amateur, epoxy is easier to mix, easier to work with, and has little to no odor. A guy using poly resin in an attached garage may run the whole family out of the house with styrene fumes.

Epoxy also has better secondary bond strength, is water proof while poly is only water resistant, and has the best physical characteristics of any of the laminating resins. But it's the most expensive, too.

Either will work, epoxy will work better, last longer, and cost more. So, ya pays yer money and takes yer choice.

Lets make it even harder to choose. I prefer Vinylester resin
 

It is a lot cheaper then epoxy. but It is more then polyester. It is water proof. Some claim more water proof then epoxy. It has better secondary bonding then polyester resin. It is thinner and wets out most glass better and easier then epoxy.

Well i had already ordered the epoxy from Merton's in Massachusetts so i might as well use it, the guy there talked me into it. I will post some more pics as i make headway, just have to get through this nasty storm coming our way tonight.

it's allways best when jobs like this are done in a building,out of the weather - you really want to avoid performing jobs like this,when things are exposed to the elements - rain water and wood isn't a good combination...
there's nothing wrong with using a wood core,provided that wood core is completley sealed...

I have lots of friends!!

strick

Cutout will epoxy today

I used vinyl ester resin, it's not porous like poly.

Epoxy Precautions
 

Mike, I agree with the choice of epoxy because of it's superior bond strength and waterproof properties as others have mentioned. However, even though it doesn't smell, it's a LOT more toxic than poly or vinylester! There are some nasty chemicals in the hardener, so you need to take some precautions when using it! Check out this note I posted a few years ago. http://www.classicseacraft.com/commu...cautions+epoxy Denny

The room temperature epoxies that we buy are generally DGEBA chemistry with an amine hardener. The "BA" in DGEBA stands for bisphenol-a. The same BPA that everyone freaks out over in their water bottles. People do get sensitized to the stuff, to the point where they can't get near it. So protective gear is important. Otherwise you could wake up one day and not be able to work on your boat again with epoxy. Some might say that is not a bad thing...

Also, I seem to recall that the vinylester resins have a chemical structure of an epoxy on one end and a polyester on the other. But that composites class was a long time ago. It didn't seem to bother the guy who had DGEBA epoxy sensitivity. And it doesn't stink of styrene monomer like polyester resin.

So is your real job welding? We all need a welder!
I just see all the stock behind the transom cut out and I need a welder for a bow rail.