On the importance of added resistance, propeller immersion and propeller ventilation for large ships in a seaway.

The influence of parameter variations on added resistance is discussed. It is indicated that changes in hull form to minimize added resistance in waves do not represent a significant saving in fuel consumption. The effect of periodic variations in propeller immersion on propulsive performance in head seas is discussed. It is indicated that changes in hull form and relative motions in order to minimize the loss in propeller efficiency do not represent a significant saving in fuel consumption. The possibility of reducing the risk for propeller racing due to ventilation by changing the propeller geometry is discussed.