Resistance reduction by increased beam for displacement-type ships

The resistance of a conventional hull with a parallel middlebody was compared with its modified version having no parallel middlebody. The modified hull was obtained by parabolizing the waterlines, that is, by extending the waterlines continuously about the middlebody, which results in an increased beam and elimination of shoulders. Numerical and experimental results suggest that there could be a significant reduction in the ship's EHP by parabolizing the waterlines at modest Froude numbers. Also, a theoretical justification based on Michell's integral is presented.