Lift line coupling The Lift Line coupling is a single line model, which includes the following features in a simplified way: Drag forces on the line. Static line weight. Longitudinal inertia forces due to vertical acceleration at both ends. The Lift Line model gives fast and quite accurate model for prediction of the total static and dynamic line end forces, and load offset. This coupling type requires that the line is mainly vertical. The net weight of the body at the lower end of the line will be applied as a force and it is therefore not possible to have two coupling lines down to the same body. The simplified Lift Line is modeled by nominal E-module, diameter, transverse and longitudinal drag coefficient, and mass per meter length. The model gives zero compressive forces. The basic model is a straight line. A modification to the straight-line assumption is made to take into account the transition of horizontal motion and forces from the crane to the lifted body due to WF motion, LF motion and transient motions (moving vessel). Current forces and the damping forces of the line acting on the body and the load are calculated along a straight line. The line weight and buoyancy and the dynamic line mass forces are also calculated along the same line.