U.S. Coast Guard 270-ft Medium Endurance Class Cutter Fin Stabilizer Performance

Abstract : As part of the seakeeping trials conducted on board the United States Coast Guard Cutter BEAR (WMEC 901), anti-roll fin stabilizer system performance was to be evaluated. The fin system as installed and operated aboard the USCGC BEAR, however, exhibited a number of deficiencies which prevented an accurate assessment of its roll reduction capability. Among the problems which were identified were intermittent excessive travel of the port fin; improper speed input into the controller; incorrect operation of the MANUAL versus AUTOMATIC GAIN modes by the crew; and a defective roll angle sensor which degraded the control algorithm, particularly in quartering seas. It was further discovered by subsequent data reduction that highly desirable alterations should be made to increase the size of the bilge keels and fins to obtain optimum roll damping. Such changes are considered crucial in order to overcome the excessive degradations in crew performance (i.e., fatigue and motion-induced interruptions) caused by the large vertical accelerations in the ship's work areas. In addition to fin enlargement, corrective actions are recommended to bring all BEAR-class fin systems up to full capacity. These include step-by-step instructions for the crew in the check-out and operation procedures, and a reduction in the maximum fin angle limit.