David, For a wooden boat, I'd stay away from polyesters. They are resins that work well with fiberglass and other fabrics, but aren't good for coating, penetrating, and sealing wood. If you're wanting to build a wooden boat, spring for the epoxies; they'll make the boat last longer, especially if you get some damage that penetrates the fiberglass layer. Raka epoxies are good, and will only cost you $35-40 a gallon. I haven't had any problems with their epoxies at all. I'm not sure why more people buy more expensive epoxy like MAS and West Systems (I haven't used them, but I've had no reason to change), but I'm sure they'd agree that inexpensive epoxy is better for wood boats than a polyester resin.

However, if you want to build a solid fiberglass (and/or kevlar, carbon, etc.) boat, then you might be ahead to try the polyesters. Read Charlie Walbridge's Boatbuilders Manual if you're considering this type of construction. Also include in the hidden costs the cost of ventilation and respiratory protection equipment.

Shawn
> OK. This makes more sense than a $15 polyurethane. Still, epoxy has
> tensile strength twice that of polyester, and compressive strength four
> times as great. It adheres better to the wood and is less brittle upon
> impact. Orthophthalic polyesters are even weaker than isophthalic resins
> also, though if it comes from a reputable marine supply house it may be
> suitable. You will also need some MEK peroxide catalyst, DMA, and perhaps
> some wax additive, as well as mixing containers, so there are some hidden
> costs.

> If rock bottom cost is the objective, give it a try. Still, in my opinion
> epoxy is a much better bet for just a little more money. Here is a tip
> that might save you some money. I am in the epoxy floor business, and have
> built boats with leftover concrete coating and grouting materials. I have
> used Sika 35, Permagile Permatop Liquid Binder, and Neogard 70714/70715.
> My cost on these materials has been $34 - $42 per gal., and they have all
> worked just fine. They are all 100% solids, non-blushing and low-viscosity
> materials, and I suspect there are lots of others out there that would
> work just as well as the expensive marine resins. Truth be known, nearly
> all epoxies come from the same manufacturing sources, differing mostly in
> diluents and fillers.

> Another tip: industrial painting and flooring contractors wind up with
> hundreds of gallons of leftovers from jobs. Our cost for disposing of
> these cats and dogs is $17 per gallon, so you may be able to call around
> and get a great deal on what is to them a storage and disposal problem!
> Good luck.