We use an in-house numerical model for the prediction of the resistance and propulsion properties of motor yachts and other mechanically-propelled vessels. The first version of this computer program was developed some 20 years ago. It has been the subject of continuous development over the years and is now our main method for predicting the resistance of all possible types of hull forms and their propulsion properties. For resistance calculations the program singles out which of the adopted 10 or so methods for the bare hull is most reliable. This includes methods we have developed based on the hundreds of models we have tested in the towing tank over the years. Other methods use the formulations developed and published by Holtrop, Holtrop and Mennen, Savitsky, Hadler, both Fung methods, Mercier and Savitsky, Radojcic, Compton, Van Oortmerssen, Bailey, Callisal, Ping-Zhong, Lahtiharju, The Delft Systematic Yacht Hull series, and others. The program can also run all applicable methods, showing the results in a graphical format from which an appropriate resistance curve can be deduced. Methods are also available for calculating the resistance of all possible types of appendages.

For the determination of the best propeller a routine is available for calculating any number of unknowns from a matrix comprising propeller diameter, blade pitch, blade area ratio, rate of rotation and number of blades. The search for the best propeller for any combination of these dependent parameters, for a given available power or total resistance, then yields the optimum propeller within the set boundary conditions. In this process predictions for the wake fraction, thrust deduction fraction and relative rotative coefficient are taken into account. Use can be made of the Wageningen BB-series, the Newton-Radar series, the KCA series, the Gawn-Burril series, the AEW Gawn series, and various Marin series for Propellers in nozzles.

Methods are also included to predict the added resistance due to waves, wind resistance and the additional resistance due to shallow and/or restricted water effects. Furthermore, it can be linked with our in-house VPP in order to look at propeller-sail combined propulsion systems, hydro-power generation by a free-wheeling propeller and other combinations.