Third International Symposium on Marine Propulsors smp’13, Launceston, Tasmania, Australia, May 2013 Uncertainty in Bollard Pull Predictions Arthur Vrijdag 1 , Jochem de Jong 1 , Hain van Nuland 2 1 Damen Shipyards Research Department, Gorinchem, the Netherlands 2 MSc-student Marine Technology, Technical University Delft, the Netherlands ABSTRACT An important aspect for a new-built tug is the contracted bollard pull performance. Not reaching the contracted bollard pull can lead to penalties for the shipbuilder and dissatisfaction for the customer while an under predicted bollard pull can lead to non-competitive design and a lower income for the shipbuilder. The bollard pull performance of a new-built tug is uncertain due to the uncertainties that are involved in the design and building of the tug and in its propulsion installation. Furthermore uncertainty is introduced during the full scale trial measurements at which the bollard pull is to be demonstrated. This paper aims at the quantification of the uncertainties that are involved in the bollard pull performance prediction. This is done by systematic analysis of the propagation of uncertainty from input (design) variables up to the predicted bollard pull performance. Keywords Bollard pull, uncertainty analysis, sensitivity, prediction 1 INTRODUCTION As said, the most important performance indicator of a tug is its maximum bollard pull. It is therefore important that the prediction of bollard pull receives considerable attention during the various stages of design. When a tug is sold, a specific bollard pull value is to be agreed upon by the shipbuilder and the customer, which is subsequently formalised in the sales contract. Based on the shipbuilders experience a certain margin is applied to the calculated theoretical bollard pull prediction. The size of this correction is traditionally based on experience and is in fact a balance between risk and reward: a high contract value may lead to high reward (profit for the shipbuilder), but may also easily lead to a penalty and dissatisfaction if the contracted bollard pull is not met. During the sea trials the vessel performance in terms of manoeuvrability, ship speed and also bollard pull is measured by means of specialised equipment (see Figure 1). In case of the bollard pull test, a certified load cell is to be used. Figure 1: Execution of a bollard pull test. Wireless load cell readout panel not visible Load cell Towing line Bollard (not visible) 447