Surfboard foam

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Surfboard foam is what the very inside layer of your surfboard is made from. This foam core enables your surfboard to float better under your body weight, known as buoyancy, and also makes your surfboard a lot lighter to carry around than the sides of trees that were used in the early days of surfing.

The initial piece of foam that is ultimately shaped into a surfboard is called a surfboard blank. A surfboard shaper cuts and carve this piece of surfboard foam into the desired outline that he wishes to produce. You will therefore often hear shapers referring to them as “surfboard foam blanks”.

There are several types of surf foam available and the one you select will determine a few factors concerning your board.

Deciding whether to ride polyurethane or polystyrene surfboard foam will affect several other factors in your next surfboard design. Being such a crucial decision, it is important to realize the different characteristics of each material and conduct a good amount of research in your quest for the perfect surfboard. To help you gather the facts SurfScience attended the October 2009 Sacred Craft Surfboard Expo to learn the latest thoughts on polystyrene vs. polyurethane.

Most surfboard manufacturers now offer a choice of polyurethane or a variation of polystyrene (Styrofoam). When Grubby Clark shut down Clark Foam December 5, 2005 it triggered an intense interest in other technologies. This is due in part because Clark’s foam recipe offered a superior ride to other polyurethane blanks available on the market. The lack of quality polyurethane blanks caused the industry to take a hard look at alternative foams and resins, including polystyrene and epoxies.

Types of foam

Polyurethane Foam Surfboards

In most surfer’s minds, polyurethane is associated with the traditional surfboard of the 90′s. This type of foam core is the original surfboard foam that has been most commonly used for surfboard shaping.

Clark Foam has been the main supplier of polyurethane foam to surfers worldwide, up until the closure of its factory in 2005. Other companies have since begun to manufacture and distribute polyurethane foam to shapers.

Like all of the surfboard foams available, polyurethane has some advantages and disadvantages.

The thing that both shapers and surfers love about polyurethane foam is that it makes for a very responsive surfboard initially due to its great flex pattern.

Many surfboard artists also love it since it is very easy to airbrush and paint surfboard art on to this foam before laminating the surfboard.

However one of the major drawbacks to polyurethane is that even though it has a great flex pattern is has poor memory. What this means is that the great flex pattern that you had in the surfboard initially will be slowly lost over time and the surfboard will eventually lose its responsiveness.

The only way for a surfer to regain that once lost flex is to have the shaper of the original surfboard try to shape a replica of your once magic stick! And even then it is very unlikely this new board will fell identical to the original surfboard.

A second downside to a polyurethane foam core is that this type of surfboard form will absorb water over time causing the foam to discolour and turn yellow. This is not only aesthetically unpleasing but will also cause the flex pattern to deteriorate quicker.

Expanded Polystyrene / EPS / Epoxy Foam Surfboards

Epoxy surfboard foam is sometimes also called beaded foam, EPS or polystyrene and is the same sort of foam that is used in beer coolers.

After the closure of the main supplier of polyurethane surfboard foam, The Clark Foam Factory, in 2005 the surfing world was in dire need of a replacement foam core for shaping surfboards.

EPS foam became very popular as the alternative foam of choice due to a number of favorable characteristics.

For starters expanded polystyrene foam is one of the most inexpensive types of foam and is widely available for a number of applications. This made it easy for shapers to get access to this type of surf foam.

In addition polystyrene foam is a very lightweight foam being lighter than polyurethane foam as well as a much more buoyant foam than PU foam.

Once this polystyrene foam was then covered by an epoxy resin during the final stages of the shaping process the result was a very light, buoyant and stronger foam core surfboard. This strength made it harder to damage and ding the surfboard.

You might be thinking how could this surfboard foam get any better but low and behold EPS foam is also less toxic than PU foam, making it much safer for both the shaper and the environment.

Regardless of these great benefits there are however a number of disadvantages to polystyrene surfboard foam that slowed its acceptance into the surfing world.

Shapers find this type of foam a little more challenging to shape due to its larger cells. This made it tough to add those fine tweaks that help differentiate a surfboard shaped by a good shaper from a great shaper.

Surfers on the other hand find that polystyrene foam core surfboards have a poor flex pattern compared to polyurethane surfboards making these surfboards stiffer and less responsive that traditional polyurethane foam surfboards.

Not a big a problem for sponsored professional surfer but this foam also, should your surfboard get dinged or damaged, will absorb water very fast as it is an “open cell” foam. This would completely destroy the surfboard.

Lastly surfboard graphic artists find it difficult to airbrush and paint polystyrene surfboard foam due to the small visible spheres in the open cell foam.

Extruded Polystyrene Foam Surfboards (XTR) aka. Styrofoam

Extruded polystyrene surfboard foam is a second type of polystyrene foam used to make epoxy surfboards.

This foam is different from expanded polystyrene foam due to the fact that it is a “closed cell” foam that is produced (or extruded) using costly machinery.

The closed cell of this surfboard foam ensures that no water is absorbed when the surfboard gets dinged. This feature results in a foam core surfboard that maintains its pristine white colour and flex pattern for many years.

Extruded polystyrene foam is very strong, with a density of less than 2.00lb/psi. This allows shapers to manufacture surfboards that are very strong yet lightweight. These surfboards are therefore also very resistant to both compression and impact.

Extruded foam surfboards are also more responsive than regular expanded polystyrene foam surfboards with better memory and flex patterns. And similar to traditional polyurethane foam, due to its closed cells, extruded surfboard foam is easy to airbrush and paint

Extruded XTR foam can be either shaped by CNC machine for higher production, or by hand for a custom surfboard. This allows shapers to mass produce surfboards to meet the high demands of the surf industry while still being able to custom shape boards for their sponsored professional riders and the average joe.

Sounds like the most ideal surfboard foam doesn’t? But of course as we all know everything has its negative side.

Expanded polystyrene XTR foam suffers from delamination issues. You see what happens in this closed cell foam is that gases begin to build up inside this foam core and due to a surfboard being completely sealed by fiberglass there is nowhere for these gases to go.

Unfortunately this resulted in bubbles forming underneath the deck where you would place your front foot and ultimately in delamination.

XTR surfboards however have claimed to solve this problem with their patented Thermoventing Technology whereby tiny holes are placed throughout the surfboard allowing these gases to escape.

So Which Surfboard Foam Core Should You Choose?

The most important factor that will affect your choice of foam will mainly be your budget.

The traditional polyurethane foam surfboards are still the cheapest to date available for under $500 USD. EPS epoxy and XTR foam surfboards on the other hand can set you back as much as $750 USD. However you must remember that one of these epoxy surfboards will last you 3 times as long as a polyurethane surfboard and can therefore be well worth the money.

What I recommend is that you base your decision on both price and your surfing ability.

If you are an experienced surfer who surfs hard every chance you get, and maybe even enters contest, then high performance is your goal. I would recommend custom ordering surfboards made from polyurethane foam.

Shapers know this foam best and can work with you to custom shape surfboards that will work for your high performance improvement! Once one board loses its flex and dies on you, bite the bullet and buy another one for the sake of improvement.

If you are a beginner surfer on a tight budget just fork out the extra $250 and buy an epoxy foam surfboard. These surfboards will withstand the beating and battering you will give it during the learning process, will remain pristine white and will last you many years.

Also if you are purchasing a surfboard for your kids these EPS epoxy boards are also great cause they will last so long that you won’t be buying your kid a new board every time he whacks the tail of the surfboard into the doorway on his way out!


The Polystyrene foam and epoxy resin combination continues to offer strong lightweight surfboard, with a perceived lower impact on the environment.

“Standard polyurethane surfboards use a three pound foam,” explains Surftech’s Robert Hyland. “What that means is if you have a one foot cube of foam it would weigh three pounds. Expanded polystyrene, like the foam found in Surftech models, is typically one pound foam. Blank to blank you’re looking at cutting a third of the weight.”

Water Absorption

One of the major drawbacks to using polystyrene blanks in the past was the quick absorption of water. This material is made up of many styrene beads stuck together. As a result, some versions of the material had many voids for water to seep into. This has been addressed in recent years.

“Our Ultraflex boards have the normal Techlite fused cell EPS core (Fused Expanded Polystyrene),” continues Hyland. “It doesn’t have any voids and it doesn’t absorb any water. All the cells are completely fused together. When we’re blowing the EPS foam, we pressurize the mold. As we pressurize the foam, it forces the foam cells to fuse together completely so there are no voids or gaps in the foam. Closed cell EPS doesn’t transmit water from cell to cell. Bad EPS, on the other hand, will be full of voids.”

Toxicity and Strength

Another reason a shaper may use polystyrene is because it emits less volatile organic compounds (VOCs). Given this fact it was no surprise to learn Fletcher Chouinard, surfboard builder for Patagonia, uses extruded polystyrene foam in his surfboards. According to their website, this foam is also 73% more resistant to taking on water than normal surfboard foam.

“It starts with an extruded polystyrene foam core; a real fine cell structure,” tells Roy Koffman of the Patagonia surf shop in San Diego County. “It’s a real lightweight, high density foam core. It allows us to glass with epoxy resin and a much stronger glassing schedule. This particular board here has a triple 4 oz deck, which is significantly more than you would find on a typical stock board. That core is so light, yet it has much more durability built into it. It’s a fine line between building a more durable board but at the same time be able to surf at a high level of performance.”

The Case For Polyurethane

Just when I thought EPS had arrived as the preferred foam of all riders and shapers I heard some very conflicting views from La Jolla based shaper Tim Bessell.

Bessell does not shy away from using alternative materials, such as carbon fiber, to build a stronger and better performing product. He offers his surfboard designs in Aviso because he considers it the most advanced surfboard technology available today. Knowing this you might think he would be on the polystyrene bandwagon, but he was quick to point out polystyrene’s deficiencies.

“Styrofoam has heat and absorption issues,” says Bessell. “XTR can’t go over 140 degrees or it will start delaminating and out-gassing. The EPS has problems because it has absorption problems. If you get a ding in an EPS board it will suck water like no tomorrow. They have these round pellets they’re trying to form together. It’s just not ever going to work. Polyurethane foam is still, I believe, the best foam in the world. Its weight to strength ratio is comparable to any of the best polystyrene blanks.”

Bessell goes on to comment on how bad styrene is for the human body.

“I’m not a big fan of Styrofoam. First of all, it’s bad for your body. I know so many veteran board builders who have gotten out of the industry because they have bad allergic reactions. I have bad allergic reactions. Our society is a fast food society. They’ve found that people have way too much styrene in their systems. I can’t even shape Styrofoam anymore.

“I’m not a big fan. It doesn’t make boards better. And the only thing better about making epoxy is they don’t use any acetone. If you want to be a naturalist then you ought to get a wood board and rub seed oil on it, but we’re kind of beyond that.

“EPS is just the wrong way to go. They’ve been blowing polyurethane foam for fifty years. Styrofoam is not the same deal. It doesn’t look good, it doesn’t take color well, and you have to use epoxy resin. With polyurethane you can use both polyester or epoxy resins.”


All three people we spoke to for this article prefer different surfboard foam…and they’re all right. Each foam has its own benefits and drawbacks. XTR and Fused EPS may resist water absorption, but will they delaminate? Standard expanded polystyrene may take on water like a sponge, but it is still much lighter than traditional Polyurethane. Polyurethane may still give the very best ride, but what can we do to make it less toxic? These are all questions that deserve attention. Any good shaper worth his salt will be glad to help you answer them.