Dihedral bows: a new type of bulbous bow for small vessels

Abstract

This paper presents the experimental results of a new type of developable added bulbous bows that have been named as dihedral bows. These type of bows are based on polyhedral bows that are used in small vessels whose origin is traced to 1990’s. The bow is designed with two developable surfaces that are designed following previous methodology on surfaces that consider material properties and will contain some chine lines. Two dihedral bow designs and their towing tank tests are presented in this work in still water, comparing the effect of the dihedral bow vs. original designs. The tests covered displacement, semi-displacement and planning hulls, tested in two different loading conditions each and for different Froude numbers. The lines of the models are real ships. An important reduction of the effective power (PE) of the ships with the dihedral bow was obtained from the experiments (About a 20%), and this successful cutback into the power is the main reason of this paper. Dihedral bows are a good option for efficient small ship design like the fishing vessels presented in this paper, and is open for larger ships.