YACHT RACING
DESIGN

In 2018 Cape Horn Engineering was proudly commissioned once again to assist in the design of the new foil system for HUGO BOSS. The CFD approach involved setting up 4 and 5 ‘degrees-of-freedom’ simulations, where the fully appended yacht is free to move in space and the aerodynamic and hydrodynamic forces are mostly balanced and the yacht finds its floating – or semi flying attitude – during the simulation.

After our successful involvement in the design of the foils of HUGO BOSS, we were delighted to be commissioned again to assist with CFD analysis to refine the design of the enclosed cockpit.

The complex behavior of the sailing yacht in reaching waves with forward speed is studied, with all the 6 DoF let free during the unsteady RANS simulation. The two different hulls show non-linear response to the wave caused by slight difference in hull form.

Cape Horn Engineering have developed a 1-button click RANS calculation to simulate the viscous flow over the rigid sails, mast, boom, hull, and any other required elements (crew, stacked sails, …). We start 1-button click simulation with a IGES file as input, computation time of 2 hrs, viscous effects taken into account, automatic detailed PDF reporting Pressures in Membrain format.

Cape Horn Engineering have run thousands of simulations in the quest of designing the perfect Formula Kite Hydrofoil for the Paris 2024 Olympic Games. Hydrofoils registered as official equipment for the Games. More to come…

CFD analysis of a yacht flooding and sinking due to water ingress through an open seacock while sailing in stormy weather conditions. Yacht sailing upwind in 20 knots of wind and corresponding developed sea state.

America’s Cup (AC35) Aero simulation. Cape Horn Engineering was responsible for providing CFD analysis to the design team and was also involved in the overall concept design of the boat and the performance prediction during the AC35 with the British Land Rover BAR challenge. In this movie, we show one of several thousand simulations performed to optimise the ‘Aero Package’ of the foiling catamarans. The Aero Package included everything that was allowed by the AC rule to be modified on the platform above water. The simulations were run for two typical sailing conditions, one upwind and one downwind. The sailing attitude, flight height, heel and pitch as well as the wing and jib trims were taken from the VPP for those conditions. Furthermore, derivatives from the VPP were used to obtain a direct comparison of the investigated candidates in terms of best VMG around the course.

CFD for 35th America’s Cup in Bermuda. The first movie shows a take-off simulation in which the rake of the daggerboard is controlled by a PID controller to achieve a pre-determined flight height. The second and third movie shows a daggerboard drop simulation in 3D. Hundreds of such simulations were performed for different daggerboard shapes at different boat speed and set rake angle. Ventilation and cavitation were monitored during the immersion process. The next simulation also shows a daggerboard drop test but in 2D, which also includes laminar to turbulent transition and the cavitation ‘bubble’. The next two simulations show cavitation, with the first using the calculated cavitation bubble in the upper (suction) side of the daggerboard based on the pressure drop. The second however is a simulation with a more detailed cavitation physics model enabled. The last two movies show velocity and vorticity fields for a 2D daggerboard section obtained by running Large Eddy Simulation.

This set of movies shows some of the simulations performed during the 34th America’s Cup (San Francisco, rigid wing 72 foot catamarans) for Team Artemis Racing. The first 3 movies show 6 Degrees-of-Freedom simulations, where the full hydrodynamic is solved and the aerodynamic forces are inputs interpolated from accurate response surface models of the sail plan. All aerodynamic and hydrodynamic forces and moments, as represented by the coloured vectors, are balanced. The analysis was performed when we were learning to ‘fly’ the AC 72 catamarans in the simulations, after TNZ demonstrated that was possible in reality. The second simulation show the dynamics of the catamaran burying the bows after a perturbation simulating a wind gust is applied to the sail plan while she was sailing with the leeward hull just touching the water or ’skimming’. The third simulation shows the boat bearing away and accelerating and taking off into her foils. For this case the trajectory was given and the rudder was balancing the moments. The last simulation shows water on deck for the catamaran running downwind and overtaking waves, burying one hull in the wave.