Riding a new wave - surfboard in trials
Integrating electronic sensors and recording devices into a high-performance surfboard offers a chance to measure and study surfers’ techniques in ways not previously possible. Dr Urko Esnaola and Hector Marin-Reyes from Fundacion Tecnalia Research & Innovation, San Sebastian, Spain, analyses its benefits.
Surfing is still a feeling-based sport, and most improvements in surfboard manufacturing and technique analysis are based on visual information and the experience of shapers, surfers and coaches.
The coach films the surfer in a training session, then replays and analyses the images, trying to find ways to improve the surfer’s technique. Similarly, in surfing competitions, the only feedback to the audience and judges is visual. As yet, no additional information, such as speed or acceleration, is available.
In surfing, it is important to control feet position and the weight applied with each foot to have the centre of mass just right at each moment. It is vital to use the surfboard rails as much as possible, so lateral inclination of the board must always be under control. Timing is also crucial, which means that, for surfing manoeuvres to succeed, forces must be applied in the correct place at the correct moment. But using a video source only as a guide, it makes it difficult, if not impossible, to determine these parameters.
Torsion and flex
Experimentation with design, materials dimensions and construction techniques has resulted in some new approaches to surfboard manufacturing, but the subsequent optimisation of a surfboard’s behaviour has mostly been through trial and error.
This behaviour is characterised by the board’s response to flexion (called ‘flex’ by the surfing community) and torsion forces. Two boards of the same design and dimensions, but built from different materials have individual mechanical properties, which results in markedly different sensations for surfers riding them.
Experience says traditional surfboards – manufactured from a polyurethane foam core with an outer shell of fibreglass cloth and polyester resins – are still the ones that perform best in competition. They are the common choice for surfers participating in the World Championship Tour. There have been attempts to improve surfboard performance using different materials, but, so far, no such initiative has completely succeeded. The main reason being that it has not been possible to measure flex and torsion properly to improve surfboard performance.
The SurfSens solution aims to provide the missing information to surfboard manufacturers and users. A surfboard has been developed that incorporates sensors to measure the appropriate parameters, while preserving the board’s performance properties. The SurfSens board incorporates strain gauge sensors for flex and torsion measurement, accelerometers, gyroscopes, a compass and GPS for movement characterisation. Pressure sensors also record position.
The components carried on the SurfSens board (see diagram below) include an IGEPv2 embedded computer to process and store sensor data on an Secure Digital (SD) memory card, two U3-LV data acquisition devices, a three-port USB hub, one DC-DC converter, several LJTick-InAmp signal-conditioning modules to handle strain gauge signals, a xsens MTi-G 6 DOF measurement unit, a GPS receiver antenna, 16 force-sensing resistors, eight strain gauges and two lithium-polymer battery cells. The electronics acquire data at 100Hz – an acceptable rate for characterising torsion and flex.
SurfSens is claimed to be the first board in the world that can simultaneously measure flex, torsion, acceleration, speed and the position of the board and the surfer’s feet while riding the waves.
All the sensor data are stored in the PC’s SD card while in the water, before being transmitted wirelessly to a remote PC.
Some tools have been developed to visualise and interpret this information. The Robotic Operating System has been chosen as the base framework. It is widely used in the robotic science community and offers many tools to develop data analysis algorithms. Tools have also been developed to synchronise SurfSens data with surf session videos recorded by an external camera:
On the seas
Real-world tests (see photographs below) with professional surfers Aritz Aranburu, Hodei Collazo, Mario Azurza and Kepa Acero have validated the SurfSens solution in varying conditions.
Analysis has shown that data acquisition is accurate enough to enable deeper analysis to map the surfboard’s critical points and help improve technique.
This opens a promising new research field for the surfing community and provides the tools to measure information that was unknown until now. Proper testing and data analysis will make it possible to find the key properties that directly affect a surfboard’s performance. This is expected to drastically influence manufacturing by making it possible to include new material combinations at localised points on the board.
From a training point of view, SurfSens could also make it possible to classify and model each of the different surfing manoeuvres using artificial intelligence mechanisms. It is anticipated that future developments of the SurfSens board will enable the transmission of real-time data about the quality of the manoeuvres being performed during surfing competitions.
Johnny Cabianca, Pukas Surfboards, Olatu SL, Olagarai (Lg Ugaldetxo) 01, 20180, Oiartzun, Spain. Email: firstname.lastname@example.org