Hull block coefficient, host factors set propeller speed / ship goods loading change will cause the output power, fuel consumption is also different. In addition, the fuel consumption makes navigation in fuel tank fuel reduction, ship longitudinal moment change trim changes. Ship model test and stability report information that, properly adjust the ship propeller immersion, meet certain requirements, ensure the propeller efficiency, can reduce water damping effect, reduce fuel consumption.
Generally in the ship, maintaining proper stern slope is favorable. Such a ship propulsion efficiency is good, can save fuel oil. The ship out of port, in order to reduce the wind area, maintain steerage, meet the demand the manipulation, general provisions first draft of not less than 2% captain, aft draft is not less than 3% of the captain.
In the stowage generally should ensure that the draft aft is greater than the first draft. But stern slope can not be too large, one will increase the ship blind is not conducive to the safety of navigation, two is easy to cause the tail water. In a draft restricted port especially to tide in and out of the port, in loading should be flat draft to ship the smooth import and.
Establish the mathematical model, reasonable adjusting optimum trim, optimization speed.
To get the best draft difference, the voyage to adjust the draft difference common way is pressed, discharge of ballast water or inner loop adjusting ballast ballast water to change the fuel consumption caused by the change of the longitudinal moment.
· adjustment of ballast water should be considered when the sea environment, meteorological conditions in order to ship safety, considering China's territorial waters under the jurisdiction of the ballast water management rules and international marine pollution prevention Convention ( Marpol Annex 1 Regulation 18.2 ) required by the ballast water management plan.
·ballast water discharged outside should be embodied in the ballast water management plan. To adjust the trim the start time and the actual draft difference in the log .