The whipping vibration of large high speed catamarans

This paper reports on a study into the whipping behaviour of large high-speed aluminium catamarans and its influence on fatigue life. Full-scale measurements of slam events and exciter tests have been conducted on two large high-speed catamarans to investigate the modes, frequencies and damping of their vibratory whipping response. A corresponding theoretical modal analysis was also conducted utilising finite element analysis and including fluid-structure interaction. Good correlation between the predicted and measured frequencies and mode shapes was found. The influence of forward speed on the added mass formulation was found to be negligible, while vessel loading conditions were found to have a significant influence on modal frequencies. Results are also presented from a fatigue study which highlight the influence of whipping on fatigue life.