This paper presents a method for hull condition estimation regarding fouling, by focusing on the increase of power demand over a period. Onboard recorded data from performance reports and noon reports of four Panamax bulk carriers identical sister ships were provided by a shipping company. In most cases, engine power onboard vessels is measured using a torque meter. Since torque measurements are generally considered of variable reliability and the required accuracy for the present study was high, the propeller shaft torque demand was calculated using an engine simulation software tuned for each specific engine and fed with recorded engine data. To distinguish the effect of fouling, wave-added resistance, air resistance, and calm water resistance were deducted from total ship resistance. Wave-added and air resistances were calculated using the STAwave-2 empirical method and Fujiwara regression formula, respectively. Calm water resistance was calculated using the FORMDATA systematic statistical series due to the lack of vessel's lines. The increase of resistance due to fouling was estimated through the increase of the Propeller Law coefficient (CPROP) and the Fouling Resistance coefficient (CFOUL), over a dry dock interval period.

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