Fine design

Surfboards are proudly customised — now fins can be tailored too, using cutting-edge technology.

 Illustration by Emily Chandler

Illustration by Emily Chandler


Field Studies is a monthly column by Clare Watson, who travels around Australia and the world exploring science by participating in studies, visiting research institutes, going on trips with scientists, and a lot more.

Thursday, September 15th, 2016

What started as a pastime in Hawaii, with wooden boards shaped like paddle pop sticks, has become an industry sprouting 5mm-thick wetsuits for the Arctic waters and inland man-made wave pools. These days, surfboards are made from composite materials: a core of polystyrene foam for buoyancy, laced with carbon fibre, wrapped in sheets of fibreglass and sealed in resin to improve their durability. 

Surfers typically have in their quiver a variety of boards fit for different types of waves and they like to experiment with fins as well. Using select materials for stiffness or flexibility can change the feel of a board under foot and, considering shape, fins are designed to either hold speed in a straight line, turn sharply or draw a wide arc. They might even match the personality of the surfer — aggressive or fluid — but all fins are meant to prevent the surfboard from sliding sideways. From the first rectangular metal fin transposed from a speedboat to twin fins, thrusters and quads, fins have propelled the evolution of surfing to greater heights.

Marc in het Panhuis, a keen surfer and materials scientist who rocks Movember all year round, has been tinkering with the shape of fins and testing different materials using the tools of his trade — 3D printers. The latest version of these fins is nicknamed the Marc 5.

Three-dimensional (3D) printing is an additive manufacturing technique that uses computer-designed models to build 3D objects from the bottom up. The computer drawing is sliced up into sequential planes to instruct a nozzle where to move. Like an inkjet printer, it dispenses a fine layer of molten materials — be that plastics, polymers, liquid metals, food products or human cells. After one coat is cured, the nozzle retreats and the platform drops a fraction, allowing another layer to be deposited on top of the last, which has set fast. Theatrically, the final product rises from within the printer.

Intrigued, I visited Panhuis’ lab which is part of the Australian Institute of Innovative Materials and not far from the beach in Wollongong, south of Sydney. More of a workshop than a laboratory, the benches are scattered with prototypes and cast-offs, each a stepping stone to a better product. It speaks of creativity. 

Researchers at the institute are printing 3D-scaffolds to grow tissues such as cartilage, the cushion between bones in our joints which wears out over time, and soon, perhaps, replacement organs. Titanium implants to match a person’s bones are already a reality. In another corner of the lab they are spinning fibres interwoven with conductive threads to fashion smart textiles that contract like an artificial muscle. There is also a room with large silver vats that resembles a brewery for upscaling the production of some materials.

When it comes to surfboard fins, commercially available fins are made by injecting a material, usually plastic, into a mould — this point and shoot method is standard for basic fins. By using 3D printing techniques as Panhuis does, manufacturing becomes far more precise. Every arc, angle and slope on the Marc 5 fins has been inspected and corrected in the computer design and the printer has a resolution down to one-thirtieth of a single Hundred and Thousand. 3D printing also allows for rapid product development: Panhuis is able to print a set of fins and ride them that afternoon, fresh off the press. He also recruits others surfers of varying abilities to trial the fins. 

For all their high-tech design, the Marc 5 fins have a striking natural quality to them. Honey coloured with a woodgrain finish, they look as if they are made from timber. You don’t need a trained eye to appreciate the finesse in fabrication; the layers of printed plastic are coarse under thumb, each stratum slightly smaller than the one beneath it, to shape the centre ridgeline. 

The 3D-printed fins are put to the test against commercial sets in the lab as well. They are scanned for comparison and subjected to mechanical testing. Held horizontal in a vice clamp, a downwards force is applied to the fin and their deflection to the point of fracture is measured. So that the fins don’t shear under the normal stresses of surfing, the fins are printed as they lie horizontally rather than vertically as they stand in a board. Panhuis studies the fracture points of surfboards too; in his office on a shelf next to the textbooks are boxes of snapped boards given a second life in research.

When I first got my hands on a set of Marc 5 fins to test out in the water I was charmed by their novelty. The waves were nonchalant, small and gentle, but I was excited. With the 3D-printed fins in place, I wanted to scrutinise their performance relative to my usual set up — would they be more sensitive or rigid? — so I tuned into my feet. I had to pay attention; usually when I am surfing my mind is drifting out with the tide. 

But of course, there would be bias depending on whether I thought that I was surfing on specialty fins versus a work-in-progress. With my love of science, I was hooked on the former. 

Surf sessions usually rate on a scale of “Well, that sucked” to “Stoked!” often for reasons other than the quality of waves alone. My happiest days surfing are those where I feel in sync with the ocean, able to sense the next wave after a lull and move with ease and grace. The Marc 5 fins were playful and made me experiment on the wave more than usual.

Panhuis is equally interested by perception and satisfaction in surfing. He uses a GPS tracker fixed to his board to log each wave in a session — and to account for the personal bias of different riders when testing fins. The tracker spits out data on how hard and fast you turn, and your speed into and out of each manoeuvre to trace the fins’ performance.

As Panhuis enjoys testing his designs, other makers are printing fins with a ribboned leading edge to mimic whale flippers. Tubercles are the bumps along whale flippers that focus the passing water into streams between them, reducing drag from turbulent flow and generating speed. Meanwhile, on the sustainability front, with the support of crowd-funding Five Oceans is moulding plastic ocean waste into surfboard fins. Sticking to a straightforward design, the focus is on repurposing plastics that have washed ashore — approximately 100 plastic bottle caps in each a set of ecoFins — which are reinforced with glass fibres. 

Whether it be to mimic nature, make a stand for the environment or to enjoy the beauty of fine design, spinning science into tangible, everyday products offers a constructive learning experience for all.

Edited by Jack Scanlan