Dynamic Stability of Planing Boats

Abstract

High-speed craft have been known to lose stability while underway even though they possess adequate static stability. Dynamic instabilities have been reported in roll, pitch and yaw, and include porpoising, chine walking, loss in running trim (diving), bow steering, progressive heeling to port or starboard, or a combination of motions. Instabilities can result in structural damage, loss of control, and crew injury. The problem is not well understood and accepted guidelines do not exist which will ensure adequate dynamic stability. The authors report data for boats which exhibit nonoscillatory dynamic instabilities and suggest quantitative criteria which may result in development of dynamically stable planing boats. Experimental procedures are presented to indicate the potential for nonoscillatory instabilities for expected operating conditions.