Denoting as the initial unstretched mooring line length and as the attachment points on the two structures (in the fixed reference axes, where one structure may be a fixed location, for instance an anchor point), the tension as a polynomial function of the mooring line extension is defined as

(9–21)

where (j = 1, 5) are the coefficients of the polynomial function and

When a polynomial nonlinear line is used as a winch line, the winch tension can be specified together with a winding in factor or paying out factor . The tension in the polynomial winch line when winding in is given by:

(9–22)

When paying out, the tension is given by:

(9–23)