A detailed investigation has been conducted into the use of Reynolds-Averaged Navier-Stokes (RANS) methods, for predicting the performance of conventional and high lift rudder sections, operating under free stream and periodic propeller flow conditions. The standard and RNG k -ε turbulence models with wall functions are applied. A methodical step wise approach to solving the propeller-rudder flow problem is shown to be necessary, in order to ensure the highest degree of accuracy and credibility in the results. By conducting detailed verification and validation studies at every stage of the research, the critical parameters required for accurate rudder performance prediction, in terms of skin frictional drag, pressure drag and lift force are identified. Steady state and time-accurate computations of the free stream flow over a NACA 0012 section fitted with a Gurney flap are conducted. Good agreement is found between the computed and experimental results, validating the RANS method for predicting flows about high life rudder sections with blunt trailing edge features. The RANS method is shown to be capable of predicting the performance response of both conventional and high lift rudder sections, when subjected to periodic transverse gusts, similar to the flow produced in the race of a propeller. The research presents the first published RANS computations for high life Schilling rudder sections, operating under free stream and periodic flow conditions. The high quality grids created around the rudder sections investigated, consisted of between 40000 and 85000 grid nodes.