Surfboard builders did the first experiments with the new foam and fiberglass and rapidly understood its potential. As the surfing fever grew, the polyurethane blanks married polyester resin and became the standard core, and the art of shaping, glassing, and sanding lived with it for decades.
Before the closure in of Clark Foam, the world's largest polyurethane blank manufacturer, the chemical-based core had a global market share of 90 percent.
The polystyrene foam core is an alternative material that gained new supporters since the closure of Clark Foam. Polystyrene blocks are traditionally lighter and less resistant than polyurethane and are cut using a hot or fast wire technique to create a smooth cut. Polystyrene surfboards are also greener than their polyurethane counterpart, and stringless models are increasingly popular. A version of polystyrene that features small foam balls in a closed cell.
It is an extremely light and buoyant material and very difficult to shape by hand. As a result, surfboards made out of EPS foam are usually molded by shaping machines. EPS surfboards are the most environmentally sustainable choice. Epoxy resin is the only skin resin that can be used with expanded polystyrene surfboards.
The extruded foam core is a percent closed-cell foam that does not absorb water, even if dinged. It offers great flex memory, ensures high resistance to strong impacts, and it doesn't feel too rigid to ride. Explore the most common styles and shapes of surfboards.
For more information on surfboard construction materials, get " The Surfboard Book. How to improve your duck dive technique in 4 simple steps. Considering the interesting materials available nowadays, its surprising that surfboard manufacturers still insist on using wood for the stringer.
There are a few companies playing around with this idea, and have released boards with fibreglass, or a carbon fibre stringer, and even a PVC plastic example — mainly to get a more measured and consistent flex pattern. The professional surfer and average consumer previously considered the shape and design of the external properties, whilst ignoring the internals.
Manufacturers are now moving towards where the ski and snowboard industry have been for some time. Considering the influence materials have on the user experience, and refining the internal characteristics is becoming more prevalent in surfboard design; so getting a consistent flex pattern is now a priority. More common now even at your local surf shop, you can find surfboards with strips of carbon fibre within the skin, in an effort to engineer the flex of that particular part of the board.
Another change recently, companies like FireWire and FutureFlex are taking the stringer, and placing it in the rails, rather than down the centre of the board; changing the way the board flexes, allowing more twist rather than flex along the length; similar to how a snowboard might bend. The end goal is the same however, whether wood or carbon, the rails are there to stop the board from snapping when placed under high loading or stress.
If you have ever snapped a board and investigated its contents, then you may be familar with the core. Typically a plastic foam material, that for the past 60 years has heavily been polyurethane also Poly, or PU. Poly comes in different densities, whilst the standard for surfboards is around 3lbs per cubic foot which works out neatly as approximately 26 litres, or a standard performance shortboard size. Some pro surfers seek out lower density blanks for a high performance board, and high density blanks for a step up or big wave board — a tow in board might weigh as much as lbs per cubed foot.
Shapers might refer to blue or red foam, the colour coding system to indicate density. Have you ever shaped Polyurethane foam? Sandpaper and a breadknife glide through it like butter. Shapers can make micrometer adjustments with little effort, due to the high density of the bubbly material. Its also cheap as its a widely used chemical, all together shapers have been happy using it for those reasons.
So what are the problems? Well yes it flexes well, but its compression strength is terrible, so under small concentrated pressure it crushes easily; hence all those pressure dings from your feet, or in some cases your head. Another problem with polyurethane is that if the outer skin is compromised, through a ding or crack, the foam will take on water.
This can lead to the break down of the foam, yellowing or brittleness; and lets face it, nobody wants a yellow surfboard. PU boards are also terrible for the environment. In the future, this alone could be the death of polyurethane as a core material. Through the production of the material itself, the process creates some nasty chemicals, and the finished product takes a long time to break down once discarded. These reasons all contribute to an increase in expanded polystyrene, or EPS, as a material for the core.
You are probably already familiar with EPS foam in drink coolers. This foam blank is made up of small expandable foam balls that inflate when heated to make it expand to form a low-density mould. This makes it one of the lightest out of the three types of foam blanks. However, it is not water resistant like XPS. Extruded Polystyrene XPS. This type is manufactured in a unique continuous extrusion way. The blanks are made by firstly mixing special chemicals with polystyrene crystals.
This chemical liquefies the polystyrene. Next, a blowing agent is applied to create tiny little air pockets.
This mixture is put in to an extruder where the mixture melts under controlled heat temperatures and pressure, forming a liquid. The liquid is then forced continuously through a die where it expands to foam that you can shape.
The end result is a unique closed-cell foam blank water repellent. Surfboards are typically constructed with a stringer running down the centre of the board. The stringer acts as the back bone or spine of the surfboard providing extra strength and rigidity.
Stringers can be made from wood types such as bamboo, balsa, paulownia or ply or PVC polyvinyl chloride. Traditionally, there will only be one stringer in a surfboard however there can be more.
Multiple stringers 2 or more are usually incorporated when you need to minimise flex and wobble. You can usually see this design in Longboards.
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