| 摘要 |
A sensing vane is placed near the leading edge of the keel of a sailboat where the water flow splits. The vane is deflected away from a "center" position (i.e., a position aligned with the keel) by the water stream as a function of the water flow angle (the angle between the heading of the boat and its path through the water). The rotational movement of the vane is sensed by a synchro transmitter which drives a synchro follower positioned at a location near the helm of the boat where it drives an indicator dial. The indicator dial is appropriately calibrated for each boat to provide a direct reading of flow angle, the ratio between the side force of the water on the keel (Sk) and the water drag force (Dk) being a function of this angle. The dial is marked to provide an indication when optimum flow angle (i.e., that for maximum Sk/Dk) is being achieved. In addition, an alerting signal may be provided when such optimum condition exists. It should be noted that the water flow angle relative to the keel differs from the leeway angle by the cosine of the heel angle, i.e., water flow angle = cos heel angle x leeway angle.
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