From what I have gathered, polyester resin will work, but not as well as epoxy. Epoxy sticks much better to the wood, and is much more waterproof.

If you are looking for cheap epoxy, the cheapest I've found is Raka. www.raka.com I've been very happy using Raka epoxy.

If you are putting the time and effort into building a boat, you might as well spend a few more dollars for materials that last.

I hope this helps.