Decisions of the design speed, MCR, and engine capacity have been empirically made by assuming the value termed the sea margin. Due to ambiguity regarding the effect of some factors on the sea margin, the value has been commonly decided based on experience. To evaluate the value from a new viewpoint, it is necessary to construct an approach to estimate the sea margin through an objective procedure based on a physical and mathematical model.

In this paper, a framework to estimate the actual sea margin of an LNGC based on the maneuvering equations of motion is suggested by considering the hull, propeller, rudder, and given sea route under wind and waves. The fouling effect is additionally quantified as the increase of total resistance by considering the re-docking period. The operation data is reviewed to amend the increase of the total resistance considering the speed loss of a ship. Finally, the factor of how much the resistance increases due to fouling is newly obtained for the vessel. Based on the comparison of the estimated sea margin with the empirical range of the sea margin, the constructed framework is regarded as feasible.

设计速度，MCR和发动机容量的决定是通过假设称为海域的值来凭经验做出的。由于对某些因素对海缘的影响含糊不清，因此通常根据经验确定该值。为了从新的角度评估价值，有必要构建一种基于物理和数学模型通过客观程序估算海容的方法。

在本文中，通过考虑船体，螺旋桨，方向舵以及在风浪中的给定航路，提出了一个基于运动机动方程来估算LNGC实际海域的框架。通过考虑重新对接时间，可以将污垢效应量化为总阻力的增加。考虑到船舶的速度损失，对运行数据进行审查以修正总阻力的增加。最后，新获得了因结垢而使阻力增加多少的因数。通过将估计的海边缘与海边缘的经验范围进行比较，可以认为构建的框架是可行的。