Improvement of Propeller Hydrodynamic Drag and Efficiency on USCG Cutters Operating in Trailshaft Mode

Large US Coast Guard cutters spend much of their underway time with only one of two propellers operating. The offline propeller is "trailed," often creating a significant amount of hydrodynamic drag. Operators from the fleet do not appear to have any specific guidance on how best to reduce this drag. Using the propeller analysis tools PSF-3 and PSF-10, propeller thrust coefficient values versus advance coefficient values were created for the propellers of the USCG 270' cutters. These values—and the associated drag—vary significantly in magnitude based on the trailed propeller pitch. Based upon sea trial measurements, expected magnitudes of this drag versus pitch setting were predicted. Minimum drag pitch settings were identified for an operational 270' cutter at 8 knots. RPM and pitch settings for maximum hydrodynamic efficiency for the online shaft are sometimes developed during ship acquisition. In the current work, a methodology for conducting such a study is discussed to demonstrate to ship operators the relative ease with which they could perform this analysis on board, if effective power and propeller thrust coefficient values are available. Consideration of prime mover specific fuel consumption rates together with propeller hydrodynamic efficiencies is discussed.     

The Effects of Boating Safety Regulations

This article investigates the effects of boater education programs and an increase in the number of water patrol officers on the prevention of recreational boating accidents. The empirical study, which estimates a reduced-form model similar to those used in the automobile safety literature, analyzes data on boating accidents that occurred in 1994 from 49 states and the District of Columbia. Model simulations, based on empirical estimates from Poisson and negative binomial models, suggest that a uniform law-enforcement policy of one-and-a-half water patrol officers per 1,000 boaters would prevent between 2,229 (negative binomial) and 2,318 (Poisson) accidents in 44 states.