Innovative approach to evaluate ship resistance in a Transitional Mode using the Length/displacent ratio

. The article aims at give a different approach to the study of the transitional mode of ship, in order to have a criteria to make a preliminary evaluation of the resistance based on the ratio Length/Displacement and on the Froude number calculated on the volume. This approach is consequent to the definition for the HSSC for vessel, and aims at provide an other element to evaluate the behaviour of the ship, especially in what is called “transitional mode” according to literature.The paper examine some case study of HSC vessel, of different categories: yacht, patrol, fast ferry, each with tank test to provide a robust set of data, in order to express a formula for an easy evaluation of the residual resistance and compare the results.The formula take in consideration the change in the residuary resistance displacement ratio, when the Froude numbers and the length displacement ratio of the vessel are changed. The final results were compared with the results of statistical calculations and with the results of calculations according to the proposed scheme