Speed and Deceleration Trials of U.S.S. Los Angeles

The trials reported in this report were instigated by the Bureau of Aeronautics of the Navy Department for the purpose of determining accurately the speed and resistance of the U. S. S. "Los Angeles" with and without water recovery apparatus, and to clear up the apparent discrepancies between the speed attained in service and in the original trials in Germany. The trials proved very conclusively that the water recovery apparatus increases the resistance about 20 per cent, which is serious, and shows the importance of developing a type of recovery having less resistance. Between the American and the German speed trials without water recovery there remains an unexplained discrepancy of nearly 6 per cent in speed at a given rate of engine revolutions. Warping of the propeller blades and small cumulative errors of observation seem the most probable causes of the discrepancy. It was found that the customary resistance coefficients C, are 0.0242 and 0.0293 without and with the water recovery apparatus, respectively. The corresponding values of the propulsive coefficient K, are 56.7 and 44.6. If there is an error in these figures, it is probably in a slight overestimate of C, and an underestimate of K. The maximum errors are almost certainly less than 5 per cent. No scale effect was detected indicating variation of C with respect to velocity (author)