다랑어 선망선의 선형개선을 통한 조업성능 향상

Abstract

Abstract

In an attempt to take measures to meet the increase of international oil prices recently and to reduce the operating expenses of tuna purse seiner, a remodeling job was carried out on a 740ton class tuna purse seiner(ship A). To strengthen the competitiveness of the fisheries industry by improving vessel performance, a bulbous bow was newly equipped, and the slipway and rudder area were also lengthened and enlarged without any transform on the propeller and main engine. To reduce the hull resistance, a cylindrical type bulbous bow was attached on the stem forward of bow thruster. The new rudder area was expanded 15% more than the old one within the extent that the existing mechanical control part and rudder stock were not changed. To prevent a damage of the fishing net and stabilize the wake field, slipway was lengthened to the optimal position. All of the new design of remodeling parts went through the model tests in towing tank and CWC(circulating water channel). Besides the resistance test, all of required model test were carried out for the hydrodynamic characters on the original and the modified ship. The maneuvering simulation to verify that the modified ship satisfies the IMO rules was performed in both zigzag test and turning test. The estimated resistance with new bulbous bow and lengthened stern was reduced by 4.8% in the 2-dimensional analysis and 17.4% in the 3-dimensional analysis in comparison with original ship. The average reduction of resistance was estimated about 10%. Maneuvering character of modified hull form was found to satisfy all regulations under IMO. In the zigzag test, increased K' value showed the improvement on the turning ability, but T' value didn't display any marked improvement on the yaw checking ability for the modified ship. In the turning test, the advance and the tactical diameter were improved very much for the modified ship. In addition to the tank test, the real sea test was carried out for the original and modified ship A. It showed that the results of real sea test corresponded with that of the tank test on the whole. On the other hand, a similar remodeling job was performed on 730 ton(ship B) and 600 ton class(ship C) tuna purse seiner respectively to grasp the progress of maneuvering and resistance on ship B for new bulbous bow only, and on ship C for new bulbous bow, enlarged slipway and rudder, and then the zigzag and the turning test were carried out for the original and modified ships in real sea. In the result of the zigzag test on ship B, the turning ability was improved very much, but the yaw checking ability was deteriorated in just some degree for the modified ship. In the turning test, both advance and tactical diameter were improved a little for the modified ship. Both original and modified ship B satisfied the IMO rule of maneuvering regulations. In the result of the zigzag test on ship C, the turning ability and yaw checking ability were remarkably improved, and the advance and the tactical diameter in the turning test were also made very much progress for the modified ship. Ship C was the most improved among the three ships for the maneuvering character of modified hull form. In according as the improvement on that, ship C was came to satisfy all the maneuvering regulations of IMO sufficiently. To find the improvement of the fishing efficiency according to the hull form remodeling for the three ships, the author analyzed the Catch-Per-Unit-Effort(CPUE) for that undertaken before(2008) and after(2010), and in addition, the CPUE of 6 similar ships operated same period and same fishing ground. As result, it came to verify that the three modified ships had a significant value on the CPUE. An another index for the improvement of fishing efficiency is the rate of reduction of fuel oil consumption for the modified ships. Fuel oil consumption per day in service speed as comparing with the original ships were reduced 2.1%, 4.0% and 5.1% on the modified ship A, B, and C respectively. And each ship's service speed was increased 1.0kt, 0.6kt, and 0.4kt according to the modified ship A, B, and C in due order. One more thing they could obtain a financial profit through the remodeling job was to reduce the net damage, the rate of net damage for the modified ship A and C were reduced 50% more than those of original ones. In the conclusion, the remodeling job with newly equipped bulbous bow, lengthened slipway and enlarged rudder area were improved fairly much on the maneuverability, fuel oil efficiency, and the ship's speed, and in the end, that led to the improving fishing efficiency. Hence, the remodeling jobs of tuna purse seiner come to improve not only the fishing performance, but contribute to the reduction of operating cost by saving energy for the fisheries industry.