Woods Hole Oceanographic Institution

Ned C. Forrester

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Michael J. Purcell and Ned C. Forrester, Bobbing Crane Heave Compensation for the Deep Towed Fiber Optic Survey System, Society of Naval Architects and Marine Engineers, New England Section, Fiftieth Anniversary Proceedings, May 6-8, 1994

The Fiber Optic Survey System (FOSS) is an underwater vehicle designed for high resolution observation of the seafloor. Towed with the standard 17.3 mm (0.68 inch) fiber optic, electromechanical cable at speeds up to 1 m/s (2 knots), it may be deployed at depths from 100 meters to 6000 meters in wave conditions up to sea state 4. These parameters result in large variations in deployed cable length, towing angle, static cable tension and cable/vehicle dynamic response to wave induced ship motions that are transmitted into the cable. Computer modeling of the cable/vehicle system indicates that certain combinations of towing parameters result in excessive vehicle motion or high dynamic cable tension. This paper addresses the effectiveness of heave compensators, particularly a bobbing crane, in reducing induced motion and cable tension. Both a passive and a combination active/passive system have been considered. Modeling results indicate that the passive system reduces high dynamic cable tensions, but eliminating induced vehicle motion requires an active component.

FILE » heavecomp.pdf
Text of Heave Compensation Paper

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