| 摘要 |
PURPOSE:To make swirl-making resistance reducible as well as to secure a high lift-drag ratio, by making a head sail and a staysail so as to be unfurled rearward a post, approximating to the post and corresponding to a wind direction. CONSTITUTION:When receiving a wind W in an arrow direction, a pole 16 is moved in the opposite direction against a direction receiving the wind W along a first guide rail 11, and locked to the first guide rail 11 at a position of 16a. Next, when a block 15 is set free to a second guide rail 12, a staysail 13 receives wind force, and the block 15 shifts to a position of 15a along the second guide rail 12 whereby a head sail 14 and the staysail 13 both are automatically unfurled as shown in one-dotted chain lines 14a and 13a. With this constitution, since the sail is unfurled in an almost tangential direction of a post 1, a swirl is prevented from being produced rearward the post 1, therefore swirl-making resistance is well reduced so that a lift-drag ratio can be improved so high.
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