Hi,
Are EPS foam blocks meant for surfboard really different from the EPS foam you can buy in hardware store (meant for building isolation etc…)
I’m looking forward to run structural tests to compare newer greener EPS alternate technologies for future surboards vs standard surfboard EPS and was wondering if I had to buy an EPS Surboard blank or if I could just go to my local hardware store and buy EPS there.
Cheers,
Marc
Hello Marc,
My experience with ‘DIY’ big box home improvement store EPS is that it is not dense enough to shape, often being at a density of 1 PCF nominal which is more like 0.88 PCF or 14 kg/m^3. I have been happier shaping off of a block I bought from a local EPS company that is more of a true 1.5 PCF or 24kg/m^3 or almost 2x the density.
With the less dense foam, the beads are tearing out at a higher rate rather than staying put to be shaped. Because of this more lightweight spackle or epoxy+microsphere slurry is needed to compensate, reducing the weight advantage. The heavier foam may allow a design to not to need a stringer or just a glue line stringer to prevent sagging on the stands until there is some fiberglass cloth and epoxy resin laminated to the shape. Windsurfers and SUP’s often use lighter foams but then have imolded nserts, compsand outer layers, and crazier glassing schedules to tie it all together.
Please let us now how it goes.
I’ve had different experiences with EPS from different surfblank companies so based on that I believe that some EPS is better suited for board construction than others. jrandy mentioned foam density which is certainly a thing, but you can get the 1# density surf blanks or SUP blanks, too. Bead sizes, whether they’re molding in blocks or forms, what chemicals they’re using to blow and/or bind the beads, etc. I’m no chemist and I know next to nothing about their processes but I do think there are different combinations out there.
The EPS slab cut never weighs out as light as people think it should. I am talking about blanks that are slab cut by Marko, Millennium and US Blanks. The tighter the bead structure, the better for shaping. So blank companies have chose to hit a happy medium between light and tight.
I can find all densities of eps bloc, but most of time quality of industrial foam bloc isn’t constant. I find that 1.5lb which is a standard for many application is the most regular. Molded surfboard blanks are better but too expensive for a no structural part of board. I like more spend money in skins where strength is…
I haven’t seen what Marko is doing these days, but at one time they were making really good molded EPS blanks. Super tight and small beads, very light too. I have not seen other manufacturers EPS slab cut blanks, but the ones that we could get that were made locally were OK. I have used their 1.0 and 1.5 versions. I have also used their 2.0 foam that was in a large block form. That foam was blown locally and the manufacturer used to sell slab style blanks, but they cleared out their supply from the warehouse, and I don’t know if they still do custom cuts. They used to sell large blocks, but the price went up a lot when EPS became a popular choice.
I’ve made many boards using the foam from Lowes and Home Depot, but they are all composite sandwich construction. The EPS that Lowes sells here on Oahu is super soft, and Home Depot doesn’t have EPS now. The boards made from Lowes foam came out super light and a bit flexy, the Home Depot boards were just right.
Density, density, density…
Often overlooked is the voume of air (gas) per unit volume of foam. Amount of air/gas content increases as density decreases. The greater the air content, the greater the expansion and contraction as ambient temperature changes. And internal surfboard pressure changes. Vents.
Also, as density decreases, minimum compressive strength decreases, and the foam crushes easier.
Marko is still the same. Good foam. They are honest enough to tell you that 1.5 is not truly 1.5, but closer to 1.8. They slab cut the bigger blanks. That foam is also very good. Have bought and sold a few Millennium slab cut EPS blanks. They are very high quality as well. You can get their EPS in any plug that they have in Poly. So a 9’5P Poly is the same as a 9’5P EPS. The difference is in the shaping. Foil, deck etc.