Efforts to design water jet craft with safe stopping characteristics have been hampered by lack of straight ahead and yawed resistance data. The characteristics of a Kawasaki model 300 stand-up jet Ski are contrasted with a Polaris model 750 SLT multi-chine three person watercraft. Drag and ift were measured in the towing tank with no jet thrust enabling directional control. To identify other variables that could be useful in design, turning circle and stopping field tests of the Polaris craft were made. It was found that most of these quantities follow linear theory, or are approximanately constant as non-dimensional variables. Measurements of the hydrodynamic forces at midships acting on an unpowered jet ski are the first step to understand vessel control in situations when the engine has been stopped or at very low RPM. These results can be used to quantify personal watercraft characteristics, and predict stopping distances and turning circle diameters for constant power.
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