Triple-hull ships with small water-plane area: Towing test results and some full-scale comparisons

Abstract

A small water-plane area (SWA) ship consists of an above-water platform and one or more hulls, which include an underwater gondola and thin strut(s) crossing the freewater surface. Applications of the SWA concept ensure very high seaworthiness, but their relatively large wetted areas provide the motivation for finding methods for reducing wave resistance. The main characteristic of triple-hull ships with identical hulls is the strong interaction between wave systems generated by individual hulls. This provides an opportunity to find configurations with favorable wave system interactions, which is the main reason of interest in triple-hull SWA ships. In this study, the model series of triple-hull SWA ships with the hull aspect ratio 9, 15, and 24 was tested in a towing tank. The effect of the triple-hull SWA configuration was determined by comparing these test results with those of twin-hull SWA ship models. Based on the tests, the effective power of some 1,000-tonne ships was predicted. Triple-hull ships were shown to be advantageous in a certain range of relative speeds. Generally, this advantage decreased with an increase in the hull's aspect ratio.