Hull fouling and performance degradation
The added resistance and fuel penalty a fouled hull and propeller impose between dry dockings, how it is measured, and how it enters a performance claim.
Hull and propeller fouling raises frictional resistance and therefore the power required to hold a given speed, so a ship that met her trial figures on delivery will not meet them at the end of a docking cycle. The penalty accumulates with time out of dock, with idle time in warm nutrient-rich water, and with the coating system’s condition and its remaining service life.
The operational consequence is a divergence between the speed and consumption figures written into a charterparty description and the figures the ship actually achieves, which is why fouling is the most common technical defence and the most common technical complaint in a performance dispute.
The full article will cover the measurement problem and the normalisation of noon-report and continuous monitoring data for weather, draft and current, the distinction between a slime layer and hard macrofouling in resistance terms, the propeller polishing and hull cleaning interventions and their in-water regulatory constraints, and the interaction with the operational carbon intensity indicator. See charter party speed and consumption warranties and voyage estimation .