EPS or Expanded Polystyrene is associated with Epoxy surfboards. There are 2 types of EPS blanks being used today. EPS that is extruded (XPS) and tends to look more like Polyurethane foam and the Bead foam which is more commonly called styrofoam. Even though most people call it styrofoam it is actually a trade name used by Dow Chemical for their EPS foam. Most epoxy surfboards being made today use the EPS bead foam so that is what we will focus on. The EPS beads are put into a mold and using pressure, steam and a blowing agent the beads are fused together to take on the shape of the mold. Most of the foam is made into large blocks and then are cut using a hot wire into either smaller blocks or what ever shape the customer may desire. The smaller block can then be cut into the shape of a blank using rocker templates and a hot wire.
After the blank has been cut it can be cut lengthwise to insert the stringer or stringer combination of your choice. This is more work for the shaper but the benefits are all the rocker templates are your own and you can design and adjust the blank to your liking. It is a great tool for any shaper as the product is completely your own , not a reshape of whoever shaped the plug in other foam blanks. By doing it this way, the blank is very true to start with and little time is spent truing up a molded blank.
Marko EPS foam with parabolic stringer
The mega rocker boards that were so popular in the early 90′s would probably never have happened if it wasn’t for this method of construction. These boards were first made out of EPS because a new design can be done so easily. Greg Loehr first started building the mega rocker boards for Bill Hartley. Bill is a well respected surfer at Sebastion Inlet and as Kelly Slater saw them being ridden he took the designs to California and the rest is history. At the time Clark foam had no blanks being made with that type of rocker and new rocker templates had to be made along with new blank molds to accommodate the design changes of the time period.
Many shapers like shaping a blank like the molded urethane they are used to and Marko foam makes a styrofoam blank that looks like the old standard. The benefits of doing it this way is there is less waste as cutting it out of a large block there tends to be a lot of waste. The foam can be recycled but finding a recycler and the logistics of doing this are hard, especially for us out here on the Outer Banks. We do find ways to use some of the leftovers though still find ourselves throwing to much away.
EPS foam is readily available, there are many manufacturers throughout the country, the type used for most eps boards is the 2 lb density made out of a “B” bead. Originally many years ago when EPS was first being used for surfboards it was hard to find a good quality foam that had good fusion of the beads but that has changed as time has gone on. Most of the foam manufactured is used in the construction industry and they have demanded a better product and we have benefited from their demands. One of the problems facing the surfboard industry is the fact that we are very small and have almost no clout with large chemical companies and manufacturers. If we go to a foam company and request a change they will not even respond as the amount used is so small they feel like it is a waste of their time, but when the construction industry demands a better product they listen.
There are some other advantages of using EPS bead foam. I have never seen one delaminate. The foam will crush in and you will get the knee wells but because there isn’t a cell structure like urethane foam it doesn’t break apart from itself and delaminate. It is lighter and tends to be more buoyant so you can ride a smaller board than a urethane foam.
There are some disadvantages and even though the beads themselves will not absorb water the space between the beads will. It is really important to keep your board repaired. Remember to repair it with epoxy resin as polyester resin will melt EPS foam. Also styrofoam melts at 220 degrees and because of the fact there is more air space inside your board if you leave it in a hot car on a summer day there is a chance the board can “blow up”, however this has become more rare with the use of the 2 lb density styrofoam. I usually don’t recommend an EPS board to someone who throws his board in the back of the pickup and leaves it all day and rides his board with dings in it.
I personally really like EPS boards. I have been riding them for many years now. I like the light weight and they feel alive to me. Some people say they are to stiff but I’ve never felt that. You can’t compare a custom made EPS to a molded sandwich construction. As I explained though there is a different care procedure and as long as the customer is aware of that all should be well.
gee scott; is that the block my board is coming out of?
the way nursing classes and clinical’s are going of late, I’m REALLY going to need that board in June. how big are those blocks anyway? is there a size limit when you get them?
The largest size I get is a 10 ft. block which I use for longboards but theoretically you can get any size you like.
Scott,
I was in your shop about a month ago and spoke to you about this very issue. I also contacted Fletcher Chounard Designs and inquired about their form of EPS. The use extruded. What’s the pro’s and con’s of extruded vs. the type you use? No rush. Your next blog post topic?
I’m not well versed on the XPS but here goes,the only Patagonia surfboards I have seen have all been done out of EPS beaded styrofoam. But I haven’t seen one in a couple of years so they may be using extruded now. I haven’t used extruded in some time now but when I did there was a problem with a lot of blow ups on the decks. The extruded that I had used had a very tight cell structure and the glass just didn’t bond as well. Or once sealed the blanks were still gassing, whatever several things were tried and nothing seemed to work out. Also at the time (late 80′s) trying to get 2 boards out of a billet was hard. The billets only came about 5″ thick and and they were to expensive to do one and you struggled to get 2. I’m sure a lot has changed since then. I can’t think of the guys name right now but he is in southern california and used the XPS and drills small pinholes in the finished product to allow the blank to “breathe” which is supposed to solve the bubbling problem.
Thanks, Scott.