Preliminary Jet Selection
The engine power is often the first consideration for jet selection. However, the boat displacement is equally, if not more important. The power to weight ratio of the boat will primarily determine the speed of a planing hull. Next is the need to select a jet that will absorb the available engine power at the estimated boat speed.
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Jet Specification
Many times the specification of a waterjet-propelled boat is based only on maximum speed at full throttle in calm water at relatively light loads. However, in the real world, engine manufacturers want their engines to run at less than full throttle, boats become heavier in service, and and the boats need to operate in less than ideal sea and wind conditions. Jet selection should also specify boat performance at cruise throttle in less than ideal conditions.
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Boat Acceleration
Waterjets convert engine power to thrust. Thrust then propels the boat. Static thrust can be measured with a bollard pull test but it is impracticable to measure thrust when underway. However, ACCELERATION is the result of thrust and hence provides a basis for comparing thrust and power absorption. Acceleration should be considered, or included, in the boat specification.
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Boat Speed & Power Estimates
If you would like to receive a performance estimate based on your specific hull and power, please complete an Application Questionnaire and send to Ultra Dynamics.