Question for shapers who’ve made boards with both PU+Polyester and epoxy+ polystyrene. It seems to me that there are many variables in board design that all act upon each other. With the physical properties of PU/Poly you have a bunch of absolutes - kind of fixed starting point that all mesurements, foil, rocker etc have been tuned to over the years, through the collective experience of many of shapers and surfers. When you switch to epoxy+ polystyrene, how much is your design influenced by the different properties of these materials? eg. polystyrene foam is generally lower density (28kg/m3- 35kg/m3) Than PU (40-45kg/m3) so do you make boards with less volume by making them thinner or narrower or shorter? Epoxy is stiffer than PU. Do you dispense with the stringer? or do you use an epoxy formulated to be more flexible as Greg Loehr talked about in an earlier post? Thanks in advance
I’ve never made a PU/Poly board. I look at designing EPS/epoxy boards this way. Most of the designfeatures of surfboards come from their use, ie strength and density (buoyancy). EPS/epoxy strength is like fuel efficiency in a car. You can use the fuel efficiency to make a faster car or to make a more fuel efficient car. You can use EPS/epoxy to make a lighter board or to make a stronger board. Your choice. A board maker who leaves the stringer out of an EPS/epoxy surboard does so for assembly requirements, not for board performance. PU/poly boards get their strength and flex from stringer and foam. EPS/epoxy boards get their strength and flex from stringer and laminate. If the next assembly process requires it will they leave off the laminate? My boards are roughly equivalent to PU/poly boards in weight, volume, and therefore in buoyancy. They are far more ding resistant, and I hope a little more resistant to snapping. My boards use 3 and 4 layers of 6oz glass, and I shape them just like PU/poly boards, with a stringer built in. The flex isn’t quite as good as new PU/poly boards but it’s acceptible, and roughly equivalent to used PU/poly boards. You can make EPS/epoxy boards with carbon or kevlar which are lots stronger for their weight and volume. Again, harvest the strength, floatation, or a little of both. Be careful going too thin. Thinning a board drops strength exponentially. Even titanium won’t keep a too-thin board from snapping. EPS goes well with epoxy glass because EPS matches epoxy glass’s resilliency. You depress epoxy glass and the EPS under it depresses. Release the force and both EPS and epoxy glass spring back together. PU foam is stiff. If you depress it, it stays depressed. Though resillient, EPS is weak, a perfect match for the added strength of epoxy glass.
I don’t know where the EPS/epoxy buoyancy hype comes from, but don’t get too caught up in it. If you can save two whole pounds in the construction of a board, how does that translate? You can throw the board around on a wave better, but not “that” much better. Buoyancy is a function of volume, volume of the whole system, board and rider. Paddling, two pounds will float you maybe 1mm higher. Sitting in the lineup tow pounds will float you maybe 3 mm higher. When riding, savings in angular momentum would yield slightly more improvement. But for the most part you could accomplish the same thing by skipping a meal.
I’m curious about eps foam. Years ago, there were disasters of expansion with explosive tendencies here in California. Many builders lost great sums of $ . How has eps changed? Anybody know more? I’m seeing more and more new start up builders with high hopes.
The differences are in semantics and in process. Builders used Extruded PolyStyrene. the capillary action during lam caused pressure buildup. Most shaped EPS boards are now 2lb Expanded Polystyrene. But builders now prepreg the foam with spackle or epoxy before sealing it.
I’ve read in the Pointblanks Surfboards site that they use extruded polysterene, they make it sound like it’s this new discovery because it doesn’t suck water. Is this just pure marketing BS?
I’ve got my story, and I’m sticking to it. Prepreg works for expanded (beaded) EPS. I imagine it works for extruded EPS as well, but new and better? You be the judge.
Boyancy is a product of density. But everything else is right noodle.
Polystyrene is my personal first choice. About two years ago a new technology sprung up from Europe called EDRO. EDRO machines are a new computerized version of the old EPS (expanded polystyrene) press technology. It makes an EPS foam with significantly enhanced strength and fusion that doesn’t leak when dinged. The first EDRO machines installed in the US were done here in Florida. They are now across the US with two in Fl. and at least two in California. This technology takes polystyrenes strength to weight advantage and combines it with a foam that doesn’t leak or delaminate. Another question in this tread was about Shulers foam being used by Patagonia and others. This is an extruded polystyrene (XPS). I was the Dow distributor for a similar product about 12 years ago. The problem we had then, and the problem that continues to plague it today, is delamination. This is caused by the fact that a significant amount of blowing agent is trapped in the cells during production. Blowing agent expands under heat. That’s what makes it work. 95% of the blowing agent in EPS foam is lost during the pre-expansion process. 95% of what’s left is lost in the molding or press cycle. With urethane the chemicals are being changed during the polymerization process and you end up with only CO2 left in the cells. But with XPS the cells are left filled with blowing agent gases. When these cells are damaged, and the gas released is then heated, a delamination or bubble forms under the glass. Also these foams are copolymerized with polyethylene which NOTHING sticks to. This makes the problem even worse. This problem has existed with XPS since Bob Simmons first used it in the 50’s. Also the new Solomon blank is based on an XPS foam so don’t go holding your breath on that one either. While it’s true that these foams are superior as far as being water tight, today I’ll go with EDRO EPS
I was thinking eps was extruded. Thanks for the clarification (s)!
Greg, what kind of density EPS are you using and what glassing schedule? regards, Håvard
Greg… do you have to “spackle” over your blanks before you glass them?
Noodle- Have you tried the Edro EPS foams yet? Where are you located? I’ll bet there’s a machine near you.
Tuna - We don’t have to but because of cosmetics we sometimes do. Just depends on color (airbrush) and other cosmetics. We do think that spackling reduces break strength though. We are actually pretty sure about that, although we haven’t run any in house break tests as of yet. The foam is sealed well enough through the EDRO manufacturing process that there is no need to spackle because of resin drain in the laminate. The new fast hardener helps there as well. We are even fooling around with an excellerated version of the fast for hot coats. We think now that a 2 hour flip time in 75* may be possible. That’s as fast as any polyester.
Havard - We generally use 2# EPS but we use 1.5# sometimes as well. We do a lot of double 4 oz. bottoms and double 6 oz. decks. Sometimes more. Depends on where it’s going. Floida is all beach break (no rocks) so we can build more for break strength and less for ding strength. A 1.5# blank with, let say, a 4 & 6 bottom and a 6 & 8 deck would be better for a place like N. Cal. where it’s rocky reef and point breaks. We’ve found through the years that points and reefs break fewer boards than beach breaks so we’ve built he boards with that in mind.
i live 500yard from this factory(link) they make blocks edro-EPS 3,2ft X 2,3ft 20 ft long from 1lb till 3,7 lb. a good friend does the maintenance on the moulds and electronics. any questions on EPS are always welkom. www.kemisol.be-products-specifications http://www.kemisol.be/
Greg, I’m in Houston. The EDRO foam sounds super to me. What is the easiest/cheapest way for me to buy a billet or get a blank cut from my templates?
I’ve never heard of an EPS/epoxy board bubbling glass EXCEPT when water was glassed into the board, like when someone patches a blank ding with thick spackle, or when the shaper fails to thoroughly dry the spackle skin. The wet spackle emits steam pressure after glassing. Damp glass produces a similar outcome. Even if you do everything right, relative air humidity while glassing can increase pressure inside the finished board. Water is why it would be nice to eliminate the use of spackle altogether with EDRO… if it works. There are too many water sources. It would be nice to eliminate one of them.
EPS boards never bubbled. But XPS does, big time. Always has. Again Noodle, where are you building boards? Speaking of humidity, that is the source of many problems in laminating, finishing, hot coating. Humidity causes blush. Blush is a bi carbonate that forms on the surface of curing epoxy. It is a reaction of humidity and the polyamine in the hardener. Blush makes board building difficult in many ways. Additive F eliminates blush no matter how humid it gets.
Houston huh? I’ll see if I can chase down an EDRO machine there. Someone must have one by now, I mean, they have one in Nebraska for god sakes.