I’m leery of even writing about this topic since many boat builders and owners have such strong opinions on the topic. I think each has its use and that both are good products which can be used to build quality boats. You will meet people who will swear one type is great and the other is terrible, and vice versa.
Polyester resin is more commonly used and has been in use longer than epoxy resin. It is more often used by large boat manufacturers than epoxy. The main benefit of polyester resin is that it’s much less expensive than epoxy. Many boat builders and ship wrights also believe it’s easier to work with.
There are a few drawbacks to polyester resin. First, it has a very strong odor which makes it unpleasant to work with for many people and makes some people sick. The second drawback is that polyester resin is more susceptible to osmosis. Osmosis allows water to get into the fiberglass and cause blisters and delamination. This problem can be as minor as cosmetic blemishes on the hull’s bottom or as serious as the hull coming apart in sheets. A sailboat with osmosis problems can be very expensive to fix.
Whether a hull made of polyester resin has osmosis problems is largely dependent on the boat builder. Some boat builders are known to build boats with polyester resin and never have any problems while certain boat builders are notorious for hull blistering. Do your research before buying.
Epoxy resin is harder and less flexible than polyester, its low odor and not subject to osmosis problems. The fact that it is low odor can be a double edge sword since it will deter some people from wearing a respirator when working with it. Even if you can tolerate the odor you should always wear a respirator whether working with polyester or epoxy.
Epoxy is more commonly used by smaller boat builders or people building their own boats. One main drawback is that it’s several times more expensive than polyester.
When making boat repairs you can use epoxy for repairs over existing polyester resin but never use polyester resin to make repairs over epoxy. It’s not really recommended to repair polyester hulls with epoxy. It can be done but the two materials have different hardness and this can cause problems since the polyester flexes more than epoxy.
In the end there are great boats built from each type of resin and there are terrible boats built from each type. Do your research to find out what type of resin the boat you’re interested in is built from and whether the manufacturer is known for having hull problems. It’s also important to have the hull inspected for problems by a qualified marine surveyor. In the next article we’ll discuss steel and aluminum as choices for sailboat hulls.
Photo By Lance Gettler All Rights Reserved