Saphira- 72' Custom Catamaran VPP

VPP Method Optimized Yacht Balance For Optimal VMG

The purpose of this study was to determine whether the yacht was in balance and what its performance would be in various sailing conditions. We completed this project coupling RANS CFD for the aerodynamic forces, RANS VOF CFD for the hydrodynamic forces, and these forces to our in house Velocity Prediction Program (VPP). This project was interesting for multiple reasons, as it was a very slender catamaran with a bi-plane rig, and dagger boards with keel stubs. One issue that RANS CFD identified early on was the interaction of the keel wake with the rudders. Our VPP balanced the forces and moments for various sailing conditions based on the diagram below.

By automatically trimming the sails for optimal driving force we were able to save man-hours and cost to the client. The images below depict how slight modifications in trim change the velocity around the sails, where dark blue is low velocity and red is high velocity. The following set of images illustrates how by moving the aerodynamic center of effort via rake, we were able to make the yacht have a better VMG upwind.


Using our approach for VPP’s we were able to determine the optimum configuration for where the aerodynamic and hydrodynamic center of efforts should be so that the yacht would balance and sail upwind at the best VMG possible.



Services Provided

VOF Model
Rans CFD
Custom VPP
Sailplan Optimization