Calibration Tests of a Japanese Log Rodmeter

A Japanese log rodmeter of the rotating-vane impeller type, with a co mmutator on the impeller shaft, was calibrated in Langley tank no. 1. The rotational speed of two impellers was determined for forward speeds up to 24 knots at angles of yaw up to ?10 0 . In general, the rota tional speeds of two apparently identical impellers tested in the rod meter decreased with increasing yaw angle, right yaw causing a greate r decrease than left yaw. The difference in calibration between the t wo impellers was approximately the same as that produced by a change in yaw angle from 50 left to 50 right. Evidence of cavitation within the impeller fairing appeared at speeds above 24 knots.