Study on the lightship characteristics of merchant ships

Abstract

Lightship weight and its distribution have significant influence on the intact/ damage stability and longitudinal strength of the ship. In this study, the range of limiting lightship longitudinal and vertical centre of gravity for different types of merchant ships have been determined. The merchant ships considered are bulk carriers, crude oil tankers, liquefied gas carriers, container ships and pure car carriers. Detailed hull form and general arrangement layout of the merchant ships were developed. Applicable rules and regulations and design considerations for each type of merchant ships were considered for this purpose. The principal dimensions, form coefficients, powering, stability and statutory rules and regulations are matched to the ships in service. At this stage, different rules and regulations concerning ships stability and trim were considered. Finally, after deducting the vertical and longitudinal center of gravity of the deadweight components (cargo, fuel and fresh water), the limiting lightship vertical and longitudinal center of gravity are determined.