In the last post we talked about strength vs stiffness or rigidity. There is a general misconception about something this concept of elasticity and strength. Often times there is deliberate misinformation, as in 6 times stronger than polyester! We tend to take that sort of information in as super stiff and strong. Realistically, is super flexible what you want in a wakesurf board? Maybe yes. Read on to find out!
So there are three major resin groups that are suitable for wakesurf board construction. In this context, when we say resin we are talking about an adhesive, a glue if you will. There are substantially MORE resin groups that are out there, but not all are suitable for wakesurf board construction. For example, the resin must be basically waterproof when cured. In effect that white Elemers glue is a resin, but it’s not suitable for wakesurf board construction, because once it gets wet it starts to dissolve. The resin must also have good adhesive capabilities, we want it to stick the external reinforcement down to the substrate or core of the board. So that sticky stuff that’s on the back of Post It! notes while that’s a resin, it wouldn’t do real well in holding our wakesurf board together, because it’s specifically designed to have low adhesion. The resin must also be fairly easy to manage, without expensive applicator machinery or requiring post cure autoclave ovens. There are some amazing polyurethane resins, but literally you could buy a new boat for the cost of the machinery needed to apply and cure it.
So, when folks sat down to figure out what resins were useful and could be used in surfboard and wakesurf board construction, it boils down to three broad groups: Polyester, Epoxy and Vinyl Ester.
Did you pick up on the first bit of yahoo’ism? We referenced it in the previous post where folks refer to wakesurf boards as fiberglass or epoxy. We know that our resins are glues and we’ve all seen those 5 min epoxy packages at the local hardware store. So we know that epoxy is a resin or a glue, is fiberglass? No! Fiberglass is a cloth and it’s used as a reinforcement in wakesurf board construction. In fact wakesurf boards that use epoxy as the resin typically use fiberglass as the reinforcement. So when you hear that reference, epoxy board vs a fiberglass board quickly think YAHOO! and disengage from assimilating any information from that discussion!!!!
So you are now, substantially more informed than the many in the wakesurf community. All wakesurf boards currently available at retail have some form of resin that glues the whole mess together (polyester, epoxy or vinyl ester) and each also uses some form of reinforcement cloth like fiberglass, carbon fiber or kevlar. There are a bunch of other reinforcement fibers but we’ll save that for a different post.
There are tons of reasons that one resin may be used instead of another. For example, polyester is substantially cheaper than epoxy and if you are thrifty, polyester may be the resin of choice in your next wakesurf board. Another is what is referred to as VOC’s. Volitale Organic Compounds or VOC in short is a measure of the toxicity of the resins. Epoxy has almost none, Polyester is like a toxic waste dump! That may be important to you as a consumer. We’ll go more in depth in comparison of the various resin groups in a later post, but what we want to bring to your attention is that there are three basic resin groups suitable for this type of constructionand each of those resin groups requires a form of resinforcement, such as fiberglass, when used in building a wakesurf board.
We wanted to further document this concept of strength vs elasticity or rigidity by making up three test panels, to compare the three major resin groups. So our procedure was to cut 3 pieces of 4 ounce fiberglass and then wet out each piece with a separate resin. That is one with epoxy, one with polyester and one with vinyl ester.
We started this by cutting three separate pieces of fiberglass, the reinforcement, and then applied different resins to each piece. In the picture below you can see the three pieces of fiberglass and we have started to wet out the first piece with some industrial strength epoxy.
The second test panel was fiberglass and polyester resin. We did not use a water clear polyester, instead just a general purpose laminating resin, which we had floating around.
The third and final test panel was Vinyl Ester resin and fiberglass.
We wanted to show that last picture with the tiny bottle of MEKP catalyst. All three of the resins mentioned cure utilizing some form of chemical reaction. Epoxy has a side A and side B or resin and hardener and the polyester and vinyl ester resins use this MEKP catalyst to start the chemical reaction.
Ok, so we wet out all the fiberglass reinforcements with the separate resins and allowed them to cure. Then did a very unscientific test of elasticity based solely on the weight of the test panel. Now this isn’t scientific because we didn’t insure each test panel was the same weight, same dimensions, perfectly flat, etc, but what we wanted to document and test was the relative stiffness of each resin, which we are pretty comfortable with.
The first up is the polyester resin and fiberglass reinforcement. This is old school and was the mainstay of surfboard construction for almost 50 years. Fairly stiff and it’s easy enough to apply.
The next test panel is the industrial strength epoxy and fiberglass reinforcement. ummm, no sophmoric jokes! As you can see it has some rigidity, but is quite frankly pretty elastic. Now, we should be clear, we didn’t get super critical with amount of resin and size and shape of the reinforcement test panel, so the lack of rigidity is somewhat over-emphasized, but the take away should be that epoxy is MORE elastic.
The final test panel is Vinyl Ester resin and fiberglass reinforcement and as you can see, we had a small issue with runners! Also the wavy nature of the test panel would effect the final stiffness results, so we can place too much reliance on this data, but we can see that relatively speaking the vinyl ester seems to fall in between polyester and epoxy in terms of elasticity/stiffness.
Are you feeling freaking brillant at this stage? Yeah, we don’t either, but if you’re following along you should be gaining some useful information for your next wakesurf board purchase. First is that strength vs stiffness is not as intuitive as we all thought and we are bombarded with advertising messages that tend to be deliberately misleading. Strength isn’t stiff when it comes to the resins used in wakesurf board construction. Second is that epoxy is a resin and isn’t comparable to fiberglass, which is a reinforcement and all wakesurf boards need both a resin and a reinforcement. The fiberglass vs epoxy wakesurf board comparison is not valid, ignore those folks.
So are you asking what does all this mean to me as a wakesurf board consumer, well first off are you paying a premium for epoxy construction? Yes indeedy you are. Why is that? Is it the extra bendy capacity of that resin that you want? No of course not, but you shoudl understand that epoxy is more costly as a resin, it takes loads more time to cure and work with and in this context it’s stronger in the sense that it has more elasticity. BUT and this is huge, how much do you need? Is it overkill? Does your wakesurf board flex at all that you need to pay that premium? Obviously you need to tune back in as we talk more about resins and their use in wakesurf board construction!
Thanks so much for following along we know a LOT of this is as boring as watching paint dry, but the end game is you’ll know a ton more about wakesurf board design and construction and can use that in your buying decision and also if you plan to make your own boards!