Ship powering prediction from isolated load-varying test data

A method for predicting full-scale ship powering performance from model load-varying self-propulsion test data is presented. The method uses load varying tests in isolation of resistance and/or propeller open water tests. Although presented here for a conventional twin screw icebreaker, the method is being developed as an alternative to conventional lITC 1978 based methods for ships fitted with unconventional propulsors, including those using podded propulsion systems. Values of a form factor, a resistance and a thrust deduction fraction are found from an analysis of the under/overload tests. The full scale torque and thrust coefficients are estimated from the model propeller data in the behind condition. The method is illustrated by using model test data for the Canadian R-Class icebreaker for which corresponding full-scale trials results are available. Comparisons are made of the results with an extrapolation done using the lITC 1978 method. The effects of use of different friction lines are also discussed.