櫓漕ぎ和船漁舟の船型調査と運動性能に関する研究

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The small fishing boats “wasen”, Japanese style vessels were mainly propelled with scull or sails before the last War. Nowadays, however, the wasens are mostly equipped with an outboard engine and their wooden hulls are replaced with fiberglass-reinforced plastics (FRP). Accordingly, the wasens made of wood and their boat-building techniques are gradually disappearing from fishing villages. In this research, though wasen was left from the mainstream of the present age, I promoted to the wasens for its rationality of the hull-type and provided to them and their boat-builders to the historical and the technical rank throughout the wasen's model resistance test of fundamental kinematic performance and theory for security of stability. Therefore, I visited about 200 boat-builders in Kyushu, mainly within Nagasaki Prefecture and collected over 1,000 memorandums of their boat dimensions and board drawings of hull structures from 1975 to 1985. Hull lines of wasen were redrawn from the collected data. Therefore, standing on the current state mentioned above, this study was conducted to record accurately the wasen’s structure. Also, collection of hull line records, model tests and analysis of the wasens were made to clarify its characteristics. Stasistical analysis were conducted on the principal dimentions measured from the hull lines and various characteristics were probed according to type, sea area and period of use. The procedure of clarifying the wasens of their hull-type and characteristics mentioned above were intended in the first department, “Survey of hull-type and statistical analysis for wasens”, and showed them in the second to 4th Chapter. Next, the investigation of the wasens for their rationality, kinematic performance of resistance and stability in the first department were intended in the second department, “Hull-type and its kinematic performance”, and showed them in the 5th to 7th Chapter. The general result was as follows: 1) I classified and showed their characteristics about 600 various wasens which could be read necessary dimensions according to application such as fishing boat, angling, seiner, whaling, carrier and other boat from field survey. So I showed each genus of the stem post, “Miyoshi” geometry that represented wasens and made its usage clear. 2) I measured around 25 major parts of hull dimensions and showed the hull-type changes by the period and characters of the sea area usage for angling and seiner wasens. In angling wasens became small all principal dimensions and tended constant length of stern keel, “tomogawara” to approach modern times by degrees. In seiner wasens the depth became large against for the length or width of principal dimensions to approach the modern times. The characteristic usages of sea area, in angling wasens were constructed wider for the length and high stability boat around the Goto inlands and western coast of Nagasaki prefecture, and in seiner wasens were constructed so as to be applied for the fishing ground by kind and size of net fishing. 3) Next stage, I selected and produced restoring scale-models of 22 high-speed wasens used mainly as whale chaser boat from the lines of board drawings for the tank test. For the examination, there were 6 stages with full or half load condition and 3 kinds of trims, by the head and stern about 1% extended mainly in even keel for the resistance test of the towing tank. From the tank test, I showed the dimensionless total resistance coefficient sγt for actual boat and same for 5 tonnage 5γt, mean full-load displacement the sample boat used for comparison of hull-type, that were converted from model total resistance. As a result of 5γt coefficient was 0.04 to 0.07 in low speed in Fn and near by the last hump of high-speed in Fn around 0.17 for full-load and 0.15 for half-load. 4) Therefore I tried analysis about propulsion performance of wasen through the above-mentioned resistance performance and the method of sweeping propulsion force of a “Ro” for the skill seaman. As the result of wasen’s effective horsepower was of 0.04 to 0.05ps in average and was calculated 0.06ps for the maximum in a “Ro” of the skill seaman. So I inspected and suggested the possibility of the boat speed about eight knot from historical fact for the 8 sweeping pieces whale chaser “8-cho-ro, Iki-seko-bune”. 5) I examined the stability of the 22 wasens above-mentioned, to compare with “standard of stability of a small fishing boat”. I decided the KG as the gravity center of height from the keel was 65% for depth (KG=0.65D) from the field survey, and calculated the stability from inlet angle and static stability of cross-curve calculation. As a result, I understood maximum righting lever was 12 to 28cm and restoring angle was 17 to 41.5 degrees for half-load, and same as 7 to 25cm, 11 to 31.5 degrees for full-load condition to the actual boat of wasen. The estimation of dynamical stability was calculated the examination of rolling period and result of the radius gyration from the inclining test for the representative models. From the result, the consequence that satisfied a safety level was provided and the wasens were recognized as the construction that maintained security. 6) On the other hand, I examined damping coefficient about roll decay (N coefficient) from angling and seiner representative model boat. The angling boat has comparatively greatly upper stack and apron stage of chine part. When the list seemed to be buried in water damped by one swing and N coefficient was about 0.035 of 10 degrees of inclining test. But seiner boat did not show the same characteristic, N coefficient about 0.018 same as 10 degrees of inclining test. As the result, I utilized it in application of ships stability law of next section. 7) The Japanese-style fishing boat wasen by the human power propulsion with a “Ro” was the mainstream investigated from the Meiji era to the last War in Showa had been moved in FRP boat of with outboard engine equipment in present. Therefore I examined the present situation and the stability of the small fishing boat that originated from wasen for the small size fishing boat safety level and stability law. I estimated the metacentric height of GM and displacement of the each small fishing boat from the experiment of its inclining and rolling test used by the result of radius gyration before mentioned for the trawling and long-line fishing boat at Mogi-town in Nagasaki city. The consequence that examined rationality of wasen’s hull type was as follows: 1) The principal dimensions of angling and seiner fishing wasens were clarified by period and usage of sea area. 2) The total resistance performances of selective 22 fishing wasens were clarified. 3) The propulsion performance of wasen was clarified from resistance test by towing tank and the sweeping test of a “Ro” of skill seaman. For the “8-cho-ro” whaling chaser was described the possibility of the velocity of historical fact in Edo-era. 4) The selective 22 fishing wasens were confirmed security with a small fishing boat safety level. 5) The roll damping coefficient of wasens were clarified from the still water rolling experiment using the models of angling and seiner fishing boat. 6) The security of stability and current state of the small fishing boats originated from wasens were identified.

著者

高山久明
長崎大学水産学部

櫓漕ぎ和船漁舟の船型調査と運動性能に関する研究

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