Abstract

A Computer Aided Design (CAD) tool called Fin Designer has been developed at the University of Wales, Swansea for three-dimensional design of surfboard fins. This tool has been developed as part of a larger project aiming to facilitate design of fins and surfboards for manufacturers with user-friendly software and direct linking into manufacturing processes such as CNC machines and injection molding. This type of tool also provides the basis for in-depth scientific and engineering studies, using engineering software for stress analysis and Computational Fluid Dynamics (CFD), giving deeper insights into potential improvements from design and material modifications. Previous papers (Lavery, Fester, Carswell and Brown 2005; Carswell and Lavery 2006) have dealt with the description of the geometrical models used in the software as well as preliminary computational results made possible by the software. In this paper the emphasis is on the correlation between drag and lift forces for surfboard fins as predicted and measured in a flow tank. Drag and lift forces predicted by the CFD were fed into a specially coded Finite Element Analysis (FEA) to obtain displacements of the fin undergoing these hydrodynamic forces. This paper presents preliminary validation of fluid-solid coupling on the standard benchmark of a cylinder, as well as some results for a single fin. While further verification of the models are required, the current results appear to suggest that the displacements are of a couple of orders of magnitude smaller than those expected by current fin manufacturers, and hence that fin stiffness remains a strong candidate for fin design improvements. Verf.-Referat