Uncertainties and Margins in the Ship Propulsion System Design Process

An important aspect for a new-built vessel is the contract speed. Not reaching the contract speed can lead to penalties for the shipbuilder and dissatisfaction for the customer, while an under-predicted contract speed can lead to non-competitive design and a lower income for the shipbuilder. The performance of a new-built vessel is uncertain due to the uncertainties that are involved in the design of the ship and its propulsion installation. Another type of uncertainty is introduced during the full scale trial measurements at which the contract speed is to be demonstrated. This paper aims at quantification of the uncertainties that are involved in the predicted performance of a ship in terms of predicted trial ship speed. This is done by systematic analysis of the propagation of uncertainty from input (design) variables up to the predicted trial speed. An 80m, 22 kts Offshore Patrol Vessel is used as a case study. The effect of uncertainty reduction by means of model testing is analysed and discussed