A systematic investigation of ship resistance reduction by beam increment for small craft

Model tests conducted with a conventional fishing boat model (UBC series model #3) showed that its hull resistance could be reduced by a systematic application of the parabolization concept, a process in which the parallel middle body of the vessel is expanded outward with locally parabolic waterlines. To accomplish this, modifications were made to the hull of a model using add-on retrofits to parabolize the waterlines continuously about the middle body. Residuary resistance values were experimentally obtained and compared with expected predictions based on Michell's integral. These numerical and experimental results suggest that there could be a significant reduction in the ship's Effective Horse Power (EHP) at modest to relatively higher Froude numbers by parabolization of the water lines. The tests show that parabolization might also be used as a retrofit to reduce the EHP of a large class of ships including small craft. An improved hull was designed and tested to combine and validate the results obtained in these tests. An extension of the experimental results to numerical optimization methods suggests that the application of conventional constraints, such as constant beam and constant displacement, may not be appropriate at higher Froude numbers. In addition, the tests showed that the frictional resistance coefficient increased during this process, which could be seen contradicting Froude's hypothesis.