Investigation of Keel Bulbs for Sailing Yachts

Detta är en Master-uppsats från Chalmers tekniska högskola/Institutionen för sjöfart och marin teknik

Sammanfattning: In this master’s thesis an evaluation of the performance of four different keel designs has been made. The keels were designed for a performance pleasure sailing yacht, more specifically the YD-40 which is a 40 foot sailing yacht from Principles of Yacht Design [1].The designs are: a fin keel, an integrated L-bulb keel, an L-bulb keel and a T-bulb keel. All design types can be found on existing sailing yachts but there has been little research made which clearly explains why one should be chosen before another from a hydrodynamic point of view.The evaluation of the performance of the four different designs has been made both by using RANS (Reynolds Averaged Navier Stokes) CFD (Computational Fluid Dynamics) as well as wind tunnel testing of keel models. Force coefficients and force trends were measured in the wind tunnel were then compared with the coefficients gained from CFD.More quantitative results are also presented which were derived using VPP (Velocity Prediction Program), calculating the race time for an Olympic race course of the keels together with hull.One important additional purpose of the thesis was to contribute to an open information platform of wind tunnel results for validating CFD; most existing work in this field has been made by professional sailing teams, and since this involves investments of huge amounts of time and effort the results are rarely open for the public.