Hydrodynamics of three slender models resembling Polynesian canoe hulls

Towing tank tests were carried out on three slender models in the Towing Tank at Newcastle University at fixed sink and trim in order to obtain more information on the hydrodynamics of such shapes, and in particular, how the shapes could generate side force when operating at a leeway angle. The research was motivated by a study of ancient Polynesian multi-hull vessels which did not appear to have keels, and so the side-force had to be generated by the hulls. The authors speculate that the earliest vessels had rounded hulls (from trees) and were probably used mainly for sailing downwind. However, it appears that evolution has caused a change in shape from circular to Vee, presumably because such shapes are better able to generate side force to enable the vessels to also sail across the wind. A CFD study with ANSYS-CFX using three different hulls was carried out as suggested by the first author and it showed that sharper Vee sections were better at generating side-force than a rounded hull. The purpose of the present tests was to investigate whether such behaviour could also be observed in physical testing. Three models were manufactured and were tested in the Towing Tank at Newcastle University in July and August 2013. It was found that there was good agreement between the CFD and tank test results, and that indeed the hypothesis that narrower Vee-shaped hulls would generate more side-force when at leeway than a rounded hull was proved.