Experimental Validation of Rudder Representation in Reduced-scale Physical Model Tests

Froude-based reduced-scale modelling of port areas is widely used to assess manoeuvring safety, including passing ship effects, confined navigation, and berthing operations. For reliable results, ship models must reproduce full-scale displacement responses to rudder inputs, particularly for turning performance. Variations in rudder geometry influence flow patterns and the resulting hydrodynamic forces that govern manoeuvrability. This study experimentally investigates the impact of rudder shape and aspect ratio on manoeuvring performance by testing eighteen NACA rudder profiles with a free-running scale model. Standard manoeuvring tests, such as turning circle trials, were conducted. The results revealed that strict geometric scaling of the rudder leads to significant discrepancies in model behaviour, while modifications to rudder geometry improve dynamic similarity. This research provides practical data showing how rudder design adjustments affect manoeuvring responses and highlights that adapting rudder geometry for scale models is an effective strategy to enhance the similarity between model and prototype ship behaviour.