Layered Fiberglass vs. Injection Molded Fiberglass Surfboard Fin Finite Element Analysis 1st Progress Report Dan Ippolito Project Advisor: Ernesto Gutierrez-Miravete Rensselaer Polytechnic Institute October 17, 2011

Layered Fiberglass vs. Injection Molded Fiberglass Surfboard Fins Deflection Comparison Analysis A deflection comparison analysis is a study of two or more components in which displacements, as a result of an applied load, are compared When identical loads and boundary conditions are applied, a comparison of flex patterns can be done by observing the x, y and z displacements throughout the geometry of the components To do a detailed deflection comparison finite element analysis should be uses to plot displacement contours to visualize various deflections The goal of this analysis is to investigate how different the flex patterns are when a surfboard fin is constructed of layered fiberglass vs. cheaper injection molded fiberglass

The Project Model a surfboard fin as accurately as possible in Abaqus CAE Make two identically shaped, and meshed, fins and assign one isotropic material properties and the other layered orthotropic material properties with alternating fiber angles Apply a force to the fins exposed surface and secure the base of the fin plugs Run an Abaqus FEA analysis and compare deflections throughout the fin for layered fiberglass vs. the injection molded construction Injection Molded Fiberglass Fin Layered Fiberglass Fin

Fin Geometry and Model Development To make the fin’s part geometry a popular thruster center fin (a FCS® model G-AM) is modeled as a solid part in Abaqus CAE. This is done using a picture of the fin as well as the actual fin to scale the part accordingly Since layered fiberglass must be assigned Lamina material properties, and are not suitable for solid parts, a shell made is made using the solid fin model The shell is assigned various thicknesses to map the thickness contour of the solid fin. This shell model will be used for both the isotropic injection molded fin and the orthotropic layered fiberglass fin to provide an accurate apples to apples comparison Picture of the FCS® G-AM Center Fin Abaqus Solid Model of the FCS® G-AM Center Fin Abaqus Shell Model of the FCS® G-AM Center Fin Abaqus Shell Model of the FCS® G-AM Center Fin with Thickness Contour Shown

Assigning Material Properties Assigning different materials properties to each of the two fins simulates the different construction methods One fin is assigned isotropic elastic material properties, for injection molded fiberglass, and different shell thicknesses to different geometric regions to provide the thickness contour The other fin will be constructed using a composite layup in which elastic orthotropic fiberglass material properties are defined. A composite layup is assigned with defined thicknesses and alternating fiber angles of +45°/-45° Abaqus Shell Model of the FCS® G-AM Center Fin Material Properties for Orthotropic E-Glass/Vinylester Fiberglass Material Properties for Isotropic Injection Molded Fiberglass

Derivation of Drag Pressure Applied to Fin Exposed Surface Calculation of Drag Force for a Full Speed Bottom Turn The drag force is calculated for a full speed bottom turn on a wave that is 10 ft high assuming you are traveling the same speed as a vertical drop from that height Derivation of Drag Pressure Applied to Fin Exposed Surface A Surfing Bottom Turn Drag Force Equation

Preliminary Results of Isotropic Injection Molded Fin Expected Outcomes It is expected that layered fiberglass will behave differently that injection fiberglass when loaded. How different these flex patterns are is what this study is aimed to find In general, a fin with a stiff base and flexible tip is ideal for performance Preliminary Results of Isotropic Injection Molded Fin

References [1] Ronald F. Gibson “Principles of Composite Material Mechanics”, second edition, CRC Press Taylor & Francis Group, 2007 [2] White, Frank M., “Viscous Fluid Flow”, 3rd Edition, McGraw Hill, 2006 [3] Chou Shih-Pin, “Finite Element Application for Strength Analysis of Scarf-Patch-Repaired Composite Laminates”, Master of Science Thesis, Wichita State University, Dec. 2006 [4] Stephen Pirsch, “How to Build Your First Surfboard – Glassing”, www.surfersteve.com, 2003 [5] M. Nurhaniza, M.K.A. Ariffin, Aidy Ali, F. Mustapha and A. W. Noraini, “Finite Element Analysis of Composites Materials for Aerospace Applications”, Nov 2010 [6] Y.W. Kwon, D.H Allen, R. Talreja, “Multiscale Modeling and Simulation of Composite Materials and Structure”, 2008