| 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 water. The sensor has improved low speed characteristics provided by a housing which extends the paddlewheel 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 paddlewheel 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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