> Byron, thanks for the info. What is the difference between your recomended
> resins and polyester? Is polyester not binding enough? -Fred

Polyester has been used for decades for boat building. Based on that long history we have a pretty good idea of how it works, and how it lasts.

Polyester resin resists water wonderfully, however, water vapor can penetrate it slowly. Some wood boats that were constantly immersed in water (usually BIG boats) have had the wood under the polyester develop rot from the trace amounts of water vapor that did penetrate the polyester. This usually took years of immersion, and was rare with small craft like canoes and kayaks that were removed from the water afer use.

The water vapor that penetrated canoes and kayak had the potential for causing delamination of the glass cloth. This would happen if there was a lot of moisture in the wood, and the boat was stored in the hot sun, where the water could turn to steam, which would be trapped between the wood and the glass cloth. This did not happen to every boat, nor did it necessarily compromise the integrity of the boat. It looked funny, but was easily fixed. Finally, there was a question of wood use. White cedar used to be the wood of choice for strip built canoes (and the few strip built kayaks) that were covered with polyester. Red cedar needed to be primed or sealed before using polyester. People who did not know about this step, or forgot it, were disappointed with the results.

Epoxy resin, on the other hand, soaks into the wood and seals it against rot, provides a much better barrier to water vapor (as well as water) and works nicely with red cedar. It can also be used as an excellent glue. Polyester is not as good as a glue.

If you are looking for an inexpensive boat that will last 15 to 25 years with care, by all means go with polyester. If you are new to using fiberglass and resins, go with epoxy. It is a bit simpler to mix, less smelly, and it might be less hazardous to work with. Unfortunately it costs a bit more. The authors of books on building small boats who have previously used polyester seem to now be promoting epoxy. This doesn't mean their old boats were poorly built, just that they have found something that is better.

One thing about epoxy that is NOT better than polyeser resin is the resistance to UV ( ultraviolet light). Epoxy needs to be covered by something to prevent degradation from long exposure to sunlight. Polyester is much more resistant. So, we usually varnish the boats made with epoxy, and we use a varnish that has a UV blocking ingredient in it.

With stitch and glue designs, my usual recommendation has been that if a person wants an inexpensive boat they build it from lauan and use polyester resin, and if they want a fancier boat they should build it from okume or better, and use epoxy resin. With strip built boats I would go with epoxy.

Hope this helps

Paul G. Jacobson