860. Merchant Ship Weight Estimation

Paper

Abstract

The estimation of the weights of the various parts of a ship is of major importance in a commercial shipyard for two reasons. They are one of the prime factors affecting the technical characteristics of the ship and they also form the basis for estimating the building cost of the ship. One would therefore expect that the derivation of accurate weights of ship parts would be a well ordered and almost mechanical procedure in every shipyard. However, although this may become so within the next few years with more and more familiarization and utilization of computers, it is not the case today. In fact, the methods used in some shipyards for the estimation of the steel weight and the weight of wood and outfit and, therefore, a major portion of the building cost would most likely surprise and even shock designers from other disciplines. Fortunately, these simple methods utilize data from similar types and sizes of ships and prove to be adequate as long as similar ships are being built. The trend today is toward new ship concepts and the existing simple empirical methods can therefore only be used for the purpose of preliminary design or ‘ball park’ building cost estimates. This paper will attempt to show how the weights affect the overall design problem and to review the development of the better known existing empirical methods suitable for preliminary design. A method for preliminary design weight estimation, developed by the author some years ago, and a detailed weight estimation method which he has used, will also be described. Finally, some observations on the impact of computers to the problem of ship weight estimation will be offered.