When the tug tows the shipwrecks in rough seas, the large dynamic towline tension occurs due to the relative motion between tow and towed ship and causes the breakage of the towline. There occurs such accidents resulting in the secondary disaster such as the collision and strand. The prediction of the unstable motion of the towed ship is quite important to estimate the towline tension accurately. The authors have made the various model and full-scale experiment to measure the towline tension during tow comparing with the numerical calculation so far. However, the relation between the towline tension and distance from tow to towed ship has not been accurately measured.
The Japan Coast Guard Academy makes a tow training using the training ship named ‘Kojima’ every year. Authors had a chance to participate in the tow training and measured the data during tow. The at sea towing experiment was carried out in the Seto Inland Sea December in 2000. The towline force and the distance between tow and towed ship were mainly measured. The relation between towline force and the distance has been made clear using KGPS. The towline figure during tow by the observation has been compared with the numerical calculation with a good agreement.
The elongation characteristics of polyethylene rope with 65 mm diameter used during tow was made clear by the full-scale measurement of both the distance between tow and towed ship and towline force. The hysteresis loop has also been confirmed in this experiment.
