Capability of the swell-compensator for Nos. 1 and 2 winches on the Hakuho-Maru has been evaluated by a deep-sea pressure sensor. This swell-compensator has two modes: i) active mode which can compensate the ship movement detected by the accelerometer close to the gantries, ii) passive mode controlling the wire tension smoothly from accidental snatch tensions. Heaving displacement of the end of winch wire during active mode operation of the swell-compensator decreases to one-third to one-fifth of that of no control mode. Heaving displacement of wire end of at least 0.3 to 1.0 meter still remains depending on wire length, even if swell-compensator is operated in active mode. Passive mode seems to be useful only for deduction of accidental tension load on the winch and gantry.
