Finish uses parametric design tools to design fins and tooling. A parametric model is created with inputs like constraints, dimensions and the relationship between geometric entities. The designer is not drawing a 3D-model directly. The parametric model generates the 3D-model, based on the input parameters. Parameters like chord, profile and outline can be adjusted quickly with high accuracy. The efficiency of multiple designs is then compared in CFD software.
Calculation of twist and deflection curve
Finish believes the performance of a fin has a major dependency on bending characteristics or how a deformed wing travels through the water. That's why the main focus is on the deformation of the fin during sailing / loading. The ability to calculate the deflection curve and twist provides a fast convergence to the best solution. As a result the contribution of trial-error design is limited. Differential equations for multiple domains along the length of the fin are solved.
resin transfer molding
All fins are manufactured by a temperature and pressure controlled RTM process. RTM (Resin Transfer Molding) is one of the best production techniques to manufacture composite parts. In contrast to hand laminating the fibers are still dry when the mold is closed. After closure resin is slowly injected. The major advantages over wet layup are:
Very low void content (<1%). Air bubbles inside a laminate have a big impact on the structural properties of a laminate. Reducing voids equals increasing structural capacity. Increased structural capacity makes a more aggressive design possible. The process also delivers a perfect surface finish.
High fiber volume fraction without distorting the fibers. Compressing the fibers before they are wet makes sure the fibers won't shift during compaction. This is a crucial part in producing fins with consistent bending characteristics.
All fins are loaded on a test bench where bend and twist is measured to ensure the fin has the proper deformation values. Afterwards the fins are blind tested by (semi-)professional windsurfers to couple a feeling to the actual deformation of the fin. A "blind test" is a method of testing in which the participants have no idea about what they're getting. Applying this method is very important to avoid errors arising from bias. Without this feedback there is no starting point for a new layup calculation / design.