| 摘要 |
A through-hull speed sensor of the magnetized paddlewheel sensor type wherein a paddlewheel is rotatably supported in a cavity adjacent a magnetic sensing device which generates electrical pulses corresponding to paddlewheel speed as the wheel rotates when the vessel moves through the water. The sensor has improved low speed characteristics provided by a housing which extends the paddle wheel into the water below the hull. The bow of the housing provides a new leading edge, generating a smaller thickness boundary layer at the paddlewheel, so that the paddles project beyond the layer at low speeds. High speed performance is improved by having a high ratio of paddle fore-to-aft drag coefficient shape; keeping the periphery of the paddlwheel hub within, or flush with, the bottom of the cavity; a low paddle projection versus paddlewheel radius ratio; and by keeping the ratio of paddle cross-section versus available cavity cross-sectional space within an optimum range.
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