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Let's Talk About Surfboard Flex

Why Surfboard Flex is all the rage.

Flex is a topic often over looked when talking about surfboards. Many people who do talk “flex”, usually veer more towards fins and fin design. In fact, we even have an article related to the flex in your fins, The Definitive Surfboard Fin Guide, but we have yet to really discuss the flex in your surfboard.

tom curren bottom turn
Tom Curren pretty much defined bottom turns and knows exactly how to use flex and projection through turns.

What is Flex?

The flex in a surfboard acts very much like the flex in fins...Flex = projection, which really means your speed when coming off the bottom, or laying into a nice speed turn off the top. This projection comes from your board bending into the shape of the wave with the force you put on it, and snapping back into shape. It is basically storing up all of that energy and releasing it, projecting you forward.

Look at it this way...when you drop into the wave and come to your bottom turn, your board bends somewhat to the shape of the wave when you power down onto it. This builds up the energy in the board as it is stressing out of its natural shape. Now, when you start to drive up the face, your board recoils back to its original shape, releasing all that pent up energy projecting you through your turn. The more proficient you become at surfing, the more you can feel this flex and use it to link your maneuvers while constantly generating speed down the line of the wave.

The trick, for shapers, is how to manipulate this to get the ideal flex properties you are looking for.

How do we control Flex?

Ever since Polyurethane foam blanks came into use, wooden strips, called stringers, were used down the center of the board. These were put in place to help increase the strength of the board and to help stiffen it up a bit. This was especially handy on longer boards as they tend to flex or bend more, simply due to their length. The strength and flexibility of the board could be controlled by using stringers of various widths. Sometimes multiple stringers would be used for the same effect, with the added bonus of looking aesthetically pleasing.

stringer work
The typical stringer used to help control the flex of a surfboard.

As shapers and surfers started paying closer attention to the flex and projection of a surfboard, stringer placement and materials started becoming more crucial. Still the most common placement for a stringer is down the center of a board. This holds true for every type of board and is more or less the status quo for most boards around the world. A board with the center stringer will feel nice and strong under foot which is important, as much of the force put down on your board will be from your feet down the center of the board. But this leaves the rails to be much softer, which can result in them flexing, twisting and wobbling differently. This is called torsional flex and can result in slowing your board down a bit.

By placing the stringer out towards the rail, you can stiffen the rail line up and give it more spring along its perimeter where the board is in contact with the water when going through turns. Parabolic stringers are often used in this case, where the stringer follows the curve of the rail instead of in a straight line.

Alternative materials for Flex

While some shapers choose to continue to use wood for both the centerline and parabolic stringers, others have begun using alternative materials like carbon fiber tape down the center or wrapped around the rail to give the same parabolic stringer effect. Carbon fiber has a fantastic strength to weight ratio, so you can essentially get the strength you need with a fraction of the weight added to the board compared to traditional wooden stringers.

future flex technology
Future Flex Technology developed by Haydenshapes Surfboards, using carbon reinforced parabolic rails.

These parabolic carbon stringers, like the Future Flex option found on many Haydenshapes Surfboards, give you all that controlled flex and projection out at the rail, helping to snap your board back into shape and project you down the line in a more efficient manner. The Future Flex technology is said to feel lively and a little springier than a traditional stringer.

Another way carbon is used instead of a parabolic stinger, is wrapping it around the board in strategic ways to help control the flex. DMS and Lost in Australia have been playing around with this technology called “Carbon Wrap” with great success.

carbon wrap technology
Carbon Wrap Technology, controlling flex and adding serious pop...Matt "Mayhem" Biolos is convinced!

Taking Flex to the Core

There are also other ways to help control and prevent too much torsional flex from happening. Different types of foam, or lamination processes can help to minimize the amount of torsional flex on traditional stringered boards, or stringerless boards altogether.

Hydro Flex technology is a lamination process that actually anchors the fiberglass skin to the foam. This not only gives you a much better bond, helping to prevent delamination, but also helps to stiffen the whole board all the way out to the rails to some degree. These boards also feel lively underfoot, but slightly different than a board with parabolic stringers in other materials.

Varial Foam is somewhat of a new technology to the surf industry, but has been used in automotive and aerospace for years. This foam is uniform in density throughout and is around 7 times more rigid than standard polyurethane foam. You don’t need a stringer in one of these boards except in extreme circumstances like a big wave gun or tow board (in which the stringer needed would be extremely thin). Without the need for a stringer, boards made with Varial Foam have a more consistent flex throughout. A foam that is more rigid and has no need for a stringer, resulting in a board with a lot of spring and projection. The added bonus of this foam is that it is about 20% lighter than PU, and can be glassed with any kind of resin.

panda surfboards geoblank
Check out the flex patterns available with GeoBlanks. Panda Surfboard and a range of our leading shapers utilise the GeoBlank range to enhance the benefits of surfboard flex.

Another technology coming out of Australia and making landfall in the US is the GEOblank tech. This is essentially combining EPS foam of different density in strategic areas throughout the blank. The individual pieces are in a hexagonal shape and glued together in what ever manner needed. This way the shaper can request that the nose of his blank have a slightly different flex pattern than the center or the tail. Even the rails can be more rigid, whatever needed to get the desired flex.


We haven’t even begun to hit the countless amount of other materials, technologies and ideas that are currently being explored. People are looking to other areas of life to get wonderful ideas…the way a fish (not surfboard) is shaped, they way its scales are laid out along its body, etc. One thing for certain is that more and more people are taking serious notes on how surfboard flex comes into the whole equation of what makes a certain board ride the way it is intended to. Controlling flex is the next frontier in surfboard design breakthroughs, and there are more experiments being tested everyday.

Make sure you check out the Board Engine to find a range of boards all made in Australia by professional shapers at the top of their crafts. Email with your details for a detailed report of board recommendations for you.

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