I'm considering a board made with Hydroflex "Natural" construction (epoxy over poly foam). However, it worries me that I've heard it called "extremely light", compared to standard 100% poly boards. I've owned a few eps/epoxy boards and hated the lack of momentum that comes with ultralight boards. I've also owned poly boards that were too heavy and they sucked just as bad as eps. There's an ideal weight balance on the best boards of any construction - as far as standard shortboards go, if it has to lean either way, I prefer them slightly on the heavier side. Is Hydroflex "natural" closer in weight to 100% PU or is it closer to eps boards?
Since epoxy resin weighs the same as poly resin (basically) if you order a traditional glassing schedule, i dont see why a board with a poly core and epoxy lamination would weigh noticably different than a normal PU/PE board. I've shaped maybe a half dozen poly boards that were glassed with 4+4/4 cloth and epoxy resin. Mostly fishes, and they didnt weigh differentely than a normal PU/PE board. If it is "extremely light" then it must either be using a low density poly core, or a light glassing schedule, or is just marketing hype. I would inquire about those details. By the way...i really liked my Poly Core / Epoxy boards. They retained the feel/heft/momentum (call it what ever but i know what your talking about) of a poly board, but the epoxy construction was noticably more durable after a year or two of heavy use.
according to hydroflex, their epoxy resin is lighter than polyester (hype?) Their processes "roots" the resin into the foam, so they can remove unnecessary resin from the deck and still maintain equal strength to standard epoxy glassing. However, I just realized that whatever is rooted in the foam makes up for what they took off the deck...so it should still be similar weight to standard epoxy glassing. therefore, my gut feeling is their epoxy and processes is maybe only slightly lighter than any other epoxy construction and that, in the case of their "natural", the term "extremely light" is exaggerated marketing hype for what is probably just somewhat lighter than standard poly construction. It would be nice to get some verification from someone who has either owned Hydroflex "Natural" or, at least, inspected some in a shop.
Well...a bit of online research indicates that epoxy resin IS less dense than poly resin (although i gotta say its not enough of a difference that holding two-three cups either one while glassing a board seems any lighter or heavier than the other). So yeah i guess i stand corrected on that. Its a bit hard for me to imagine that JUST the lighter properties of epoxy vs. poly resin make that much difference in overall board weight. The vacuum bagging process they use certainly would draw a significant amount of resin out of the cloth laminate, regardless of the resin type, even accounting for the bits of resin that might be pushed down into the foam by vacuum pressure...(the "roots" you refer to). Anyways, i've never ridden one so let someone with actually experience chime in. I'm interested myself. Some of those ...Lost grovel shapes in a durable, light boardbuild technology sound pretty cool.
Keep in mind, also, that epoxy's slower cure time will give more time for the epoxy to seep further into the foam... any foam... before it cures. With some epoxies, you could be talking about an hour or more, rather than minutes with poly. That, along with vac bagging, gets the best mechanical skin-to-core bond. "Extremely light" is a vague and relative terms, so I'd chalk that up to hype until you get actual numbers. As Mitchell said, epoxy is only slightly lighter than poly. But it does build a stronger, more durable board, over any core.
