Sixty years of research on ship rudders: effects of design choices on rudder performance

Rudders are primary steering devices for merchant ships. The main purpose of using rudders is to generate forces for course keeping and manoeuvring. In exceptional cases, rudders are also used for emergency stopping and roll stabilisation. Furthermore, rudders affect propeller thrust efficiency and total ship resistance. Therefore, rudders are important to navigation safety and transport efficiency. The performance of rudders depends on the rudder hydrodynamic characteristics, which are affected by the design choices. Scholarly articles concerning the design of rudders date back more than 60 years. Moreover, a lot of knowledge fragments of rudders exist in literature where ship manoeuvrability and fuel consumption are discussed. It is worthwhile to gather this information not only for researchers to advance the state-of-the-art development but also for designers to make proper choices. To have a contemporary vision of the rudders, this paper presents a consolidated review of design impacts on rudder performance in ship manoeuvrability, fuel consumption, and cavitation. The discussed design choices are rudder working conditions (Reynolds numbers and angles of attack), profiles (sectional shapes), properties (area, thickness, span, chord, and rudder aspect ratios), types (the position of the stock and the structural rudder-hull connection), and interactions (among the hull, the propeller, and the rudder). Further research is suggested on high-lift rudder profiles, multiple-rudder configurations and interactions among the hull, the propeller, and the rudder. Recommendations for industry practices in the selection of the rudder design choices are also given.