3000. Weight Estimating and Reporting for Major Ship Conversions

Paper

Abstract

There have been several major conversions conducted in the United States during the last decade to increase the Military Sealift Command fleet. Weight estimating and reporting for major ship conversions presents a significant challenge to the weight engineer. A major conversion is usually defined as one that changes a ship’s principal dimensions, type of service, or light ship weight by 10% or more. As-built weight data and drawings are sometimes unavailable and often the ship has already undergone many other alterations since its construction that may significantly affect weights and centers of gravity. The accurate prediction of light ship weight and centers is critical to the success of a major ship conversion since the principal characteristics (length, beam, depth, draft, speed, etc.) usually cannot be easily changed, as they can in preliminary design for new construction. This paper describes the process of preparing and maintaining weight estimates and reports throughout a major ship conversion project. Definitions and reasons for major conversions are discussed in the introduction and then the process of establishing a preconversion baseline is described. The preliminary and contract design weight estimates are described and removals, installations, vendor data, margins, level of detail, and other aspects of them are discussed. The process is then followed through the detail design and completion phases, and concluded at the post-conversion inclining. Several recent examples from the authors’ experience are described in detail, and lessons learned are shared with the reader. The result is a comprehensive guide to the subject that should be useful to anyone involved in ship conversion weight work.