Measuring and testing – Navigation – Ship's log
Patent
1989-11-22
1992-07-07
Woodiel, Donald O.
Measuring and testing
Navigation
Ship's log
G01C 2112
Patent
active
RE0339822
ABSTRACT:
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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"Elements of Fluid Mechanics", D. G. Shepard C 1965, pp. 344-357.
Drawing entitled "Outline Dwg-Knot-Meter Assy" by Airmar Technology Corporation, Amherst, N.H. 03031.
Airmar Technology Corporation
Woodiel Donald O.
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