Feedback to design power requirements from statistical methods applied to onboard measurements

Definition of the ship main dimensions at the contract design phase plays an impor­tant role on the profitability of the ship project. Cargo carrying capacity and design speed are fixed at this stage. Power requirement is then estimated and an allowance to weather margin and hull fouling is reserved. Clean hull resistance in calm sea conditions can be generally estimated at high accuracy. How­ever, the sea margin is generally taken as 10-20% of the clean hull resistance. Onboard measurements, with the information gathered on similar ships provide important insights into actual power requirements. The ship may be operated on different loading conditions (draft and trim), speed profile, and weather conditions than what was expected at the contractual design stage. Statistical methods applied to onboard measurements can capture the dependencies of the ship power consumption from different factors, and a decomposition into weather, shallow water, and hull-fouling effects, of the required power can be presented. In this paper, a statistical method based on regression model and application to the onboard measurements is presented. The statistical method enables constant monitoring of the power requirement, and the development of hull condition. Regression model can make use of the entire data set, instead of limiting the analysis on the variation of fixed set of parameters.