Manoeuvring Performance of the Fishing Boat Modified by a Bulge by Yasuo Yoshimura, Member Shiro Suzuki Ning Ma, Member Yoshiyuki Kajiwara Summary Fis

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1 Manoeuvring Performance of the Fishing Boat Modified by a Bulge by Yasuo Yoshimura, Member Shiro Suzuki Ning Ma, Member Yoshiyuki Kajiwara Summary Fishing boats suffer from much capsizing as compared with other vessels. It may be pointed out that the stability of fishing boats tend to be poor as the bases of the severe operations and the poor management of loading condition as well as the problem with the restrictions of principal dimensions of ship. According to the recent capsizing of the trawler "Ryuho-maru V", Ministry of Land, Infrastructure and Transport of Japan forced to check the stability of existing fishing boats and to improve the stability if not enough. As for the improvement of the stability, the fitting of a bulge on sidewall of the vessel is one of the best solutions. This method was adopted in the old naval fleets and polar research ship "Sohya" in Japan. However, it is not commonly used. It is important to clarify for the design of the bulge what influence it has on the ship's performances not only on the stability. In this paper, the authors have investigated into the effect of the bulge on manoeuvrability and the manoeuvring prediction, based on the model experiments and the full-scale experiments of original and enlarged fisheries research ship "Ushio-maru". They have also investigated into the predicting method for a fishtail type high-lift rudder is proposed. The concluding remarks are summarized as below. (1) By fitting the bulge on sidewalls of the vessel, hydrodynamic sway damping lever is slightly reduced. In addition, the yaw damping lever is reduced by the increase of ship's mass, which keeps the almost the same stability lever of course keeping as the original ship. (2) For the prediction of the hydrodynamic derivatives of the fishing boat with an initial trim, Kijima's formula are useful except Y'5, Nr, Y'-m' using the effective draught and block coefficient of the ship. It is desirable that Ys, Nr, Yr-m X are not corrected by the initial trim. (3) For the simulation of the manoeuvring ship motion with the fishtail type high-lift rudder, the rudder open characteristic is to be altered in the proposed mathematical model. The coefficient becomes 1.4 times larger than the conventional rudder. Even for the large rudder angle such as 65, the conventional rudder model is still available, because the actual angle of attack is decreased by the turning motion of ship.

2 Fig.1 Table Database of L/B for fisheries research ship 1 Principal dimensions of original and enlarged "U shio-maru" (designed FULL) Fig.2 Body plan of the enlarged bulge. "U shio-maru" with

3 Fig.3 Co-ordinate system Fig.4 Measured hydrodynamic hull cients of original "Ushio-maru" force coeffi

4 Fig.6 Measured rudder lateral velocity component at the Fig.5 Measured hydrodynamic rudder cients of original "Ushio-maru" force coeffi- Table 2 Measured of original hydrodynamic force derivatives "U shio-maru" Fig.7 Comparison of turning circle tests with 35 deg. of rudder angle between measured and simulated

5 Fig.8 Comparison of steady turning between measured and simulated. performance Table 3 Measured hydrodynamic force derivatives of enlarged "Ushio-maru" Fig.9 Measured hydrodynamic hull cients of enlarged "Ushio-maru" force coeffi

6 Table 4 Comparison of measured linear hydrodynamic force derivatives Fig.10 Initial trim and false keel of a fishing boat Fig. 11 Comparison of the hydrodynamic derivatives between measured and estimated by Kijima's formula Fig.12 Comparison of the hydrodynamic derivatives between measured and modified estimation.

7 Fig.l4 Comparison deg. of rudder simulated. of turning circle angle between tests with 35 measured and Fig.l3 Comparison of the rudder normal force between fishtail rudder and conventional rudder. Fig.l5 Comparison of steady turning between measured and simulated performance

8 Fig.16 Comparison of 20 ured and simulated. Fig.17 Comparison of deg. of rudder simulated. deg. Z-test between meas- turning angle circle between tests with 55 measured and

9 Fig.A1 Experimental model arrangement (1) Fig.A2 Experimental model arrangement (2)

10 Fig.A4 Differences between ordered and drift angle of X-Y carriage measured Fig.A3 Forced motion by X-Y carriage Table Al Comparison of identified hydro- dynamic derivatives between utilizing the measured motion of X-Y carriage and ordered motion (Original "Ushio-maru") Fig.A5 Differences between ordered and towing speed of X-Y carriage measured

Fig. 1 KAMOME50-2 Table 1 Principal dimensions Fig.2 Configuration of the hydrofoils (Endurance and sprint foil) Fig. 3 Schematic view of the vortex l

Fig. 1 KAMOME50-2 Table 1 Principal dimensions Fig.2 Configuration of the hydrofoils (Endurance and sprint foil) Fig. 3 Schematic view of the vortex l A study on the simulation of the motion of personal full-submerged hydrofoil craft by Yutaka Terao, Member Summary A new energy utilization project developed by Tokai University was started in 1991. It