Royal Huisman Shipyards asked us in September of 2004 to become a participant in the design team for Ethereal, a 58m Ketch for an American owner, together with Ron Holland, Pieter Beeldsnijder and Royal Huisman experts.
Our work mainly involved those aspects associated with the performance of the yacht (hull, keel and rudder lines, propulsion configuration, etc).
The work carried out consists of the following:
- Extensive resistance analysis, in calm water and in various sea states
- Analysis of various propulsion configurations (both conventional shaftline and Pods)
- Analysis of tank test results
- Design of shaftline and struts
- Fairing of keel and winglets
- CFD analysis for hull, keel and winglets
The CFD analysis was specifically aimed at the verification of the model test results and to assess the performance of the winglets. For this, we chose an equilibrium sailing condition, upwind at a Froude number of 0.33, and analysed two models; one with winglets, and one without winglets.
In the analysis of the results special attention was given to the development of the bulb tip-vortex and the remaining rotation in the water aft of the bulb. The numerical values for sideforce and resistance (corrected for free surface effects) corresponded well with measured values from the towing tank and the predicted values from our in-house developed VPP.