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Fig.4 and Fig.5 show the size of the experimental models. In case of Fig.4, the model was named as the high mast sail. The rigid wing sail of NACA0030 type, which is 1.0m in height and 0.llm in width, was set up on the column mast that is 0.25m in height. The effect of the boundary layer on the floor can be ignored because of the sail's position. Two slats were made to investigate the effect of the size of them. The chord length and the circular arc radius of the slat are O.1m, 0.1m named as the large slat and 0.05m, 0.1m named as the small slat respectively. The position of the slat is not translated, but the angle of that against the sail can be changed. The square soft sails with a nylon, that are 1.0m in height and 0.2, 0.25, 0.3. 0.4, 0.5m in width and the triangular soft sail of 0.45m in base, were prepared for the experiments. This triangular hybrid-sail is shown in the reference paper [4].
Fig.4 Experimental models on the high mast sail
Fig.5 Experimental models on the low mast sail
Fig.6 Experimental condition of the model
In case of Fig.5, the model was named as the low mast sail. In the design stage of the sail, height of the sail that influences on the sail area is very important factor. According as the mast becomes tall, it is possible to have a large sail area, but there is restriction from the viewpoints of the stability and the manoeuvring in severe weather. Moreover, the port that can be used is limited in case of bulk carriers etc. because of the bridge near the port that the height is lower than that of the mast top of the sails. Therefore, the experiments using the low mast sail as in Fig.5 were carried out. Six soft sails were prepared to investigate the effect of the form and the width of the sails.
2.2 Experimental condition
The wind tunnel experiments were carried out in our research institute to investigate the aerodynamic characteristics of the sails. The experimental condition is shown in Fig.6. The load cell to measure forces and moment was set up to the center in the turntable and the sail model was jointed on the load cell. The wind velocity was uniform in the vertical direction, but the boundary layer about 0.1m existed on the floor in the tunnel.
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