So no doubt you’ve heard the use of the term epoxy in wakesurf board construction and if you’ve followed us for any length of time, you’ve seen us use it frequently. We thought we’d spend a little time talking about epoxy as it relates to wakesurf board construction and clarify the term epoxy wakesurf board.
You may have heard the incorrect reference to wakesurf boards divided between epoxy and fiberglass. Those who have followed us have know that fiberglass is a reinforcement fabric present in just about all wakesurf boards manufactured and that epoxy is a resin that is an alternative to polyester and vinlyester, the other two major laminating resins. So the process is that fiberglass or some other reinforcement is laminated to the underlying wakesurf board blank or foam. So the misnomer is that an epoxy wakesurf board also have fiberglass and wakesurf boards made with polyester resin also have fiberglass or some other type of reinforcement fabric.
The correct comparison would be between epoxy resin and probably polyester resin, which is one of the most widely used laminating resins.
Both epoxy and polyester as resins use some form of catalyst or hardener. Polyester uses a small amount of a liquid called MEKP and epoxy has matching resin and hardeners. When the two components are mixed together a chemical reaction starts or is accelerated. In both resin the end result is a hardened plastic and when used to laminate fiberglass you wind up with a FRP or Fiberglass Reinforced Plastic.
So what’s the difference between epoxy and say polyester? Polyester resin has a few advantages over epoxy. One is that after mixing with the catalyst is cures and is done! A few hours later that cure cycle is complete. Polyester resin is also substantially cheaper than most epoxies that are that white water clear formulation. Polyester is also more forgiving with mix ratios, there are usually a range of catalyst to resin ratios that will allow the polyester to cure.
Epoxy has some advantages over polyester in a few areas, one is variety. You can get different formulations that change the cure time that can match the ambient temperature. Epoxy doesn’t use solvents to affect the cure and so can be used with just about anything to cause adhesion. When working with EPS foam as a core for a wakesurf board, only Epoxy is a suitable resin the other resins will melt the foam. Epoxy is also substantially stronger than polyester. Typically Epoxy has a bond strength of 2,000 psi, vinylester around 500 psi and polyester 100 psi. You can see there is a HUGE difference. Can you also see the built in hype? Polyester resin was the resin of choice for years, but how could that be true when there is such a difference in the bond strength? It’s the underlying foam. Do you think a piece of 1.9 pcf density EPS foam used in an epoxy wakesurf board can handle the 2,000 psi? We know that EPS has some great properties, but putting 2,000 pounds on a 1 square inch section of the foam would result in disaster especially if the surface is laminated with a lightweight fiberglass. It’s the system that matters and in that system the weak link is the underlying foam. So while it’s true that epoxy is stronger and stiffer than polyester, in terms of the system, the foam is basically the same and will give way long before the epoxy. Epoxy also is much less toxic.
Is epoxy the strongest adhesive? No, Urethane Methacrylates Yeah, say that three times fast is typically stronger, but for the manufacture of wakesurfers epoxy is about the best combination of attributes.
In the next installment, probably sometime next week we’ll talk about some of the different brands and why we are switching from one of the most popular brands of epoxy resin used today. Thanks so much for following along!