Modern Surfboards and Their Structural Characterization: Towards an Engineering Approach

Abstract

Recently, manufactures who produce surfboards using computer aided design and robotic (CNC) shaping tools have gained a larger share of the surfing market, allowing board producers and shapers to produce lighter and more durable boards. The improvement in design and production process of surfboards has been directly linked with the adaption of technologies tested and validated in other industries. However, the surfing industry still lacks methodologies, standards and testing facilities to scientifically investigate and quantify the structural and hydrodynamic properties of surfboards. It is widely accepted that distributed rigidity, damping and stiffness in the three directions play a huge role in defining surfboard performance. These properties are rarely stated by producers and never measured. The present paper compares two boards with equal outline and geometric shape but built with two different technologies: one board built with a traditional high density polyurethane (PU) blank, polyester resin and a stringer to improve longitudinal stiffness and one board built with bio epoxy resin, expanded polystyrene (EPS) and two side inserts made of cork to improve longitudinal stiffness and damping. Different tests were carried out to compare the two boards and a testing methodology with the aim to evaluate board structural properties and identify key parameters that will influence the board performances. Accelerometers were used to characterize stiffness and damping while a custom-made flex machine was used to evaluate the torsional stiffness. Differences between the two boards are highlighted, leading to the fact that the two boards, even being identical in size, will behave differently in different wave conditions and for different surfers.