A power boat propeller blade failed during a high speed power boat race. The propeller blade separated from the main body of the propeller and flew a few hundred yards into a swimming area near the race course.
An overall view of the failed propeller is shown in Photograph A.
Photograph A Overall view of failed power boat propeller.
Visual examination of the propeller blade fracture revealed a thumbnail on the failed blade trailing edge as shown in Photograph B.
Photograph B View of failure site on failed propeller hub. Thumbnail fatigue fracture is noted.
Further visual examination of the failed blade revealed a flat fracture. Low cycle fatigue appeared to extended over 40% of the blade fracture. The failed blade failure modes denoted is shown in Photograph C.
Photograph C Overall view of failed blade with fracture profiles noted.
Visual examination revealed that the power boat failure was the result of metal fatigue. Metal fatigue initiated at numerous locations along the interface between the plating applied to the blade and the propeller.