During builder's trials held in late 1989, the USCGC KANKAKEE, the first of two river buoy tenders constructed for the U.S. Coast Guard, experienced severe vibration and noise levels in the hull girder and deckhouse at design speed, even though the vibratory behavior of the main propulsion systems was well within specifications. To determine the cause of this problem, an underway hull vibration survey was conducted, together with dockside impact tests and a 11spuddrop11 test. The cause of the problem was traced to the coincidence of the four-bladed propeller exciting frequency with the hull girder natural frequency in the four-node mode of vertical vibration. After studying a number of corrective options, the owner decided that the most expedient method would be to build three-bladed and six-bladed propellers and then choose those generating the least vibration and noise. Interim trials with both wheelsets and detailed propulsion system vibration tests led to the adoption of the six-bladed propellers.

This content is only available via PDF.
You can access this article if you purchase or spend a download.