Naval Architects such as myself regularly use a range of mathematical techniques to predict the resistance of a boat’s hull at a range of speeds. With this information it is then possible to work out what power is required, enabling the most suitable engine, transmission and propeller to be selected.
Basic hull design data, such as measurements taken from the lines plan, are used as input data to one of the many powering routines, each one being applicable to a particular type of vessel. After having completed the calculation procedure the output data normally consist of resistance and required power figures at a range of hull speeds in tabular or graphical form. The full size resistance figures for a yacht or boat can also be obtained from the tank testing results. The results for the measured resistance of the model are scaled up, or extrapolated, using established computational procedures.
One memorable powering project that I carried out involved the evaluation and powering tests of the 20-oared galley “Argo,” designed by Colin Mudie for the writer and explorer Tim Severin, who rowed “Argo” 1500 miles with a crew of volunteers to trace the route of the legendary Jason and the Argonauts. The investigative work performed on a model of the hull of “Argo” is amusingly described by Tim Severin on page 41 of his book “The Jason Voyage - The Quest for the Golden Fleece”.