4. FIN CONFIGRATIONS
We propose the 3 different patterns of fin configurations. Fin configurations has been considered from the viewpoint of propulsive and navigation performances. The fin area cannot be so enlarged in consideration of the propulsive performance and harbors limitation. We change the position and type of fin. We assume that the sail-assisted ship is general cargo ship and this ship length is 180m. The 3 fin arrangements that we select are explained as follows;
・Case 1 is installed in center of the ship and two sideboards.
・Case 2 is installed in Square Station (S.S.) 4 of the ship and two large sideboards that is small aspect ratio.
・Case 3 is installed in S.S. 8 of the ship and one centerboard that is same area as Case 1.
The details of fin configurations are shown in Fig.3. We perform towing tank test using the original model (General Cargo ship) and model equipped with these fins in order to measure the hydrodynamics force and moment. Then the results of hydrodynamics force and moment due to this experiment are shown in Fig.4. The underwater fin affects the side force Y. The experiment parameters of original model are leeway angle and heel angle. That of the model equipped with the fin only by leeway angle, since the changes of hydrodynamics force and moment due to heel angel are assumed to be small in the range where the heel angle is small. From the experiment results, the underwater fin effects the roll moment Mx. But the yaw moment Mz is influenced so much by the under water fin. The resistance of the ship equipped with the fin increase as the surface area of the fin increases. The coefficients used in simulation model have been requested to analysis these experiment results.
Fig.3 The each configuration of underwater fin for 3 cases
The force and moment on the under water fins are estimated by using simple formula as follows;
This simple formula of the force and moment on the underwater fin make approximation formula to the first expression by experiment results. This simple formula can be estimated easily for another fin configuration. We can investigate the qualitative characteristic of hydrodynamics force and moment of various fin configurations when we plan the sail-assisted ship.