The continuously increasing computer power has made it possible to make performance calculations based on RANS CFD method for propellers within commercial acceptable lead times nowadays. Wärtsilä has decided to extent the scope of the numerical analyses, to include the ship hull geometry as well. The final goal is to have a full scale numerical towing tank in operation within the next few years. This ambitious plan can be divided into several building blocks, like developing method to calculate open water performance and the implementation of the cavitation model. In this paper two building blocks will be discussed in more detail. The first topic is about the Reynolds scaling effects on ducted propellers, like the well-known 19Anozzle. The performance of the propeller and nozzle are split into pumping efficiency and loss-coefficients.Comparison of model scale and full scale calculations give a clear explanation of the scaling effects observed. The second topic is the method to calculate wakefields. It is confirmed once more that there are clear scaling effects on the wakefields as well.