Extruded Polystyrene

Extruded Polystyrene Foam Core with Epoxy Resin Shell

Regular Joe enjoys studying and thinking about aspects of life, including the foam material that is whittled into surfboards.

The greatest message in the world came to the world using the means of marine travel. I think there is good work for the grand purpose of the world in engineering, chemistry, biology, medicine, etc. I’m just not cut out to be one of those workers. But I still like learning a bit about it.

Extruded polystrene is the topic of this blog, or rather, a review of the practical differences in riding a surfboard made from extruded polystrene core and shelled with epoxy resign and multiple layers of fiberglass cloth as compared to riding one with a polyethalene core and polyurethane resin. Exciting, I know.

My college chemistry classes taught me that I am not a chemist, so the whole molecular side of extruded polystrene is not the concern of this review. Rather here’s what I have found it to be like to stand on top of piece of extruded polystrene wrapped in 12 oz of fiberglass cloth soaked in epoxy resin while in certain places on a moving fluid.

Fun. Intrinsically it is not the material but the end use of it. Surfing is merely fun, no matter what it is on. I started on one of those canvas rafts that would eat a hole in stomach.

Float. I think my physics is correct to understand the increased bouyancy due to the decreased weight relative to total volume. The volume is not different due to the material but the lighter weight with that same volume creates more float. This equates to more efficient planning which results in more efficient paddling. This can result in catching more waves. This results in average guys who surf at most once a week more time on a wave per unit of time invested. This results in a better use of time in recreation away from one’s family who is more important than the recreation.

Firm. Extruded polystyrene is more firm or harder than expanded polystyrene and polyethalene. At least my experience on the three different materials indicates this to be so. Add to this more layers of fiberglass cloth and a more durable epoxy resign and you have the next attribute…

Fighter tough. I could say ‘tough’ but tried to stick with the alliteration. I’ve surfed used boards of this material and have just bought my first brand new one of this core and shell and nothing I’ve used surfs as close to the feel of the traditional materials of polyethalene foam and polyurethane resin than this combination. I have but dings in it but they are mainly punctures. When I have dinged it I’ve been surprised that it is not worse. I’ve also landed in positions where I really thought that I would put some serious pressure dings in the deck of the board only to find none.

Lighter weight. I will not repeat the benefit to float but elaborate on another benefit to lighter boards – maneuverability. Lighter boards in the more performance orientated designs enable the rider to move the board with less work. Positioning the board upon the falling lip of the wave or positioning the board under one’s body as they come down from the crest of the wave to the face or trough of the wave is done faster and/or easier (less work) when the board is lighter. Lighter weight in a successful planning design also ends up going faster. This can be used for more enjoyable turns at a higher speed and the experiences of riding places on or above the wave that require faster speeds. Where this is especially attractive is to those average fellows like me who ride small waves 95% of the time. Two areas that lightness is not a benefit is in wind. When the wind is closing in on gale force and is offshore or sideshore the light material does not feel as good as a board built out of traditional materials. The traditional material seems not to be blown off the wave and also seems to absorb or plane through (don’t know which one and I’m sure it depends upon the hull design, too) the surface chop. So when it’s larger surf and hard offshore I prefer my traditional materials.

Conclusion. “More mature” surfers [read: surfers who are less light footed than they used to be, less muscular than they used to be, carry more mass than they used to carry, yet know what boards and dimensions they ride, what shapes work for them, and ride the same style board faithfully] riding smaller waves (less than chest high and not powerfully shaped) should consider expanded polystyrene with epoxy resign for the materials of their faithful shorter boards for the above reasons.

Where PU makes more sense is when one is ‘testing’ a design and thus can get a PU board for less money. When one is ordering a board that he/she will not ride too often, then PU is cheaper and the durability is not a real issue. When one is surfing in a lot of chop on the face of a very fast wave or paddling into a very strong offshore wind the weight of a PU might be to the advantage of the rider over a EPS. For little ones riding boards for short periods of time and thus grow out of them before they wear out PU still makes sense.

Joe’s testing equipment and grounds: extruded polystyrene with epoxy resin boards were thrusters at 5’10 x 19.25 x 2.4, 6’0 x 19 1/16 x 2 3/8, 6’1 x 18 7/8 x 2 1/4, 6’3 x 19 x 2 3/8; keel twin fin at 6’0 x 21.5 x 2 ½. Beach break waves from weak shin-high-should-not-be-in-the-water-surf to chest-high, offshore A-frames to head-high-no-one-goes-to-the-beach-on-a-day-like-this-day slop windsurf in 25 kt wind to overhead, offshore at 20kt, the-crowd-is-a-lot-smaller-on-these-days waves over the course of two years. Joe is about an average rider of a shorter board (read: he pays for all his gear).