Surfboard Volume Dial copyright 2012 Mat Arney

Dial it up. Photo: Mat Arney


The Inertia

How are you meant to measure a surfboard?

No, I mean accurately, and in a way that allows you to compare different surfboards to one another in a meaningful fashion?  I can measure a square no problem; at a push I could recall the Pythagoras equations for the circumference and area of a circle.  But surfboards are different beasts:  3-dimensional shapes comprised of varying and complex parabolic curves.  Frankly put, they are a nightmare to measure, and the result is that, whilst many of us might regularly ride a 6’2” x 18½” x 2¼” squash tail, we all ride remarkably different surfboards.  Does that measurement of width apply all of the way from nose to tail and does your board hold that thickness all the way out to the rails, or does your board’s planshape pull to a point at either end with foiled, knifey, rails?  You see what I mean:  three, incredibly basic, dimensional measurements give you very little clue as to the applicable size of a surfboard.

“There are no readily available formulas for calculating the volume of an irregular object, so the easiest method is liquid displacement.” states Nick Blair of Joistik Surfboards in Australia.  “To my knowledge that method has never been used in the industry by your average custom shaper, so I think that the recent phenomenon of volume’s importance to your everyday surfboard consumer is a direct roll-on effect from the use of machines by most shapers these days.”

Before CNC shaping machines, there is no way that any two boards could be identical, and even now it is unlikely that highly refined features such as bottom contours would be perfectly replicated over and over again when being hand finished.  Nuances in factors such as rail profiles and depths of bottom contours can make a surprisingly large difference, not only to how a surfboard performs, but also to how it feels under your feet.  Which is why it stands to reason that more and more of the major players in surfboard design and production should be including a fourth dimension in their measurements to help surfers to make informed purchases:  volume.  The overall size of a board is one of the key measurements that we ought to consider, surely?  I mean, there are others too, but volume is one single measurement that we can all understand and use as a baseline.

The coaches at the Surf Simply coaching resort out in Costa Rica are unashamed geeks. They’ve been busy cutting up old surfboards and doing some sums to try and make this whole idea more accessible and meaningful to board buyers.  They’ve worked out a single measurement whereby perhaps at some point in the future, if the world champ is asked what size board he’s riding then a reply of “five-nine” or “six-two” will not refer to the length of their surfboard in feet and inches but instead to the ratio of their weight in pounds to their board’s volume in liters.  Ru Hill, Surf Simply‘s owner explains:

“The whole idea of referring to boards by length is misleading, even if you mention the width too. The most significant single measurement is obviously the volume. My 5’7″ is 27.9 liters while my 6’0″ is actually a smaller board at only 26.3 liters.”

By considering the volume as the primary dimension of the surfboard, surfer’s can go out and purchase a range of different length surfboards, off the rack, knowing with confidence how the volume is going to compare to the boards that they are used to.  Each subsequent surfboard that they then purchase, whether as a replacement or as their ability improves, can be an informed purchase based on either replicating the feeling of a favorite board, or changing a board’s volume to match improvements in their surfing or varying conditions.

“But that’s not the whole story either,” Hill continues. “If I want to ride what Kelly is riding so that I know what he’s feeling under his feet, then I can’t just buy the same boards as him because Kelly (at 160lb/72.5kg) is 5 pounds (2.25kg) heavier then me. What I need to know is the ratio of pounds to liters those guys are riding. Kelly is riding a 5’9″ Semi Pro 12 which is 24.3 liters, meaning than his ratio of pounds to liters is just under 6.6 (just under 3kg/L).  I’m nowhere near that level and I know that boards that work for me are around 5.8 pounds per liter so when I bought my semi pro 12 I chose a 6’0″ which is 26.2 liters.”

Hill and his team of coaches estimate that the biggest board that anyone can duckdive is around 3.4ppl (pounds per liter), while the smallest, “toothpick” surfboard that the pros might ride is around 6.7ppl.  For female surfers the range is slightly shorter, going from 4.5ppl (beginners) through to around 5.5ppl for female pros.

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  • ScottTX

    I have never shaped a board but want to and so this article was interesting. While volume has recently gained more attention, all design factors still have to be considered nearly equally. I mean, building a surfboard is a multi-attribute model, with each component receiving an importance “weight.” I’d argue that an multi-purpose funboard would likely approach attribute-weight parity. Also, I’m intrigued by the suggestion of surfer weight-to-board volume ratio. But “static” volume (placing an object in the water, then measuring displacement once water is calm”) is just the beginning. We also have to consider force applied to the board while in motion with a human rider, and the result on displacement. A 5’6 egg with equivalent volume to a 7’0 thruster is obviously not going to ride the same as the longer board…and different maneuvers displace varying amounts of water…..so after this rambling entry…are we overemphasizing volume? Or is it just that volume has historically been underemphasized?

  • dodo

    volume distribution is just as important as the volume itself. you can foil out the ends or put volume forward, you can push it out to the rail or dome it up under your chest, etc… the only time volume is a good measure as a constant is when you are sitting on your board waiting for a wave. (or as you mentioned duck-diving). you can have a flat thin low volume board that paddles and planes better than a higher volume board that has more extreme rocker or a rolled bottom contour. volume is a useful tool in a very general sense. a starting point. the volume that your typical 3d software spits out is never accurate. a lot of material is removed during shaping. rail volume is the easiest controlled variable for custom shaping for a particular rider. the type of surf you will be surfing will dictate your volume as well. you dont want the same volume when surfing perfect mentawais as you would for trestles.

  • Mat

    Dodo and Scott, you both made very valid and insightful points, thank you. I wrote a fairly extensive response to your comments this morning that doesn’t appear to have posted, so I’ll attempt to rewrite it as best I can. Surfboard design is obviously an enormous subject, one that could easily fill a book with the topic of volume justifiably deserving it’s own chapter. What I tried to do here was produce a concise and I hope interesting piece accessible to the large number of surfers who perhaps don’t pay a whole lot of attention to the details of their equipment, and to open up a debate. As you both point out, volume is a useful tool in a general sense but it is still limited and needs to be considered alongside other variables. There are a myriad of other factors that come into play with volume alone, the greatest of which must be distribution. The force applied by a surfer and where to, is also a valid consideration and is obviously something that varies in particular according to the stature of the surfer and whether they have a high or low centre of gravity which affects the leverage that they apply when turning on rail. The centre of mass and centre of effort are widely used in boat design, but not something that appears to be considered in a uniform way in surfboard design. Then as soon as you throw the planing area or position of the widepoint into the mix, it again opens up new avenues of interest. As I mentioned before, it is a multi-faceted topic, open to debate, and condensing it into a short article is nigh-on impossible! I suppose the main point that myself (and the people who I sought information from) are trying to make is that whilst volume is a limited measurement in the same way that traditional length x width x thickness is, it is a valid one, particularly when used in a weight:volume ratio. So, to answer your last question Scott, I think that volume has historically been under-emphasized because of the difficulty in measuring it, and now that computer aided design and manufacture can measure volume (prior to hand finishing) then perhaps we ought to integrate it into our language of surfboard design on a par with LxWxT. The more that we know and understand, the better, as far as I’m concerned.

  • Dexter Hough-Snee

    Spot on and I would agree that your average surfer doesn’t really know what it is that (s)he feels in/on their surfboard, whether underarm or in the water. Volume is a concept that can be ‘felt’ more so than LxWxT. If I’m not mistaken, volume really came to the fore via all the Swaylocks guys about fifteen years ago (maybe more?) but wasn’t easily mechanically quantifiable until the last ten or so years. Probably as a result of being founded in the transition from APS3000-to-CNC platforms and the digital shaping backgrounds of its San Diego and Burleigh collaborators, Firewire was one of the first big boardmakers to begin listing volume on every shape in their production line back in 2006 or so and then C.I. and all the major board manufacturers followed suit. Cottage industry guys in Australia probably had them beat by five or ten years, although their measurements were cruder given the absence of a machine. As footnote, there are numerous guys building guns and big wave equipment that advise their riders on volume instead of the traditional dimensions. Good piece. In spite of being accessible, easy science, most surfers are completely clueless about some very basic concepts from foam and resin types to bottom contours. Maybe easy articles as such will prevent so many parking lot know-it-alls spouting the typical “bro, this board is insane, it’s magic (insert mangled design concept theory) makes it awesome” pitch.