An investigation on material diversity of synthetic fiber ropes in the course stability of towing under wind

Abstract

The synthetic fiber ropes are commonly employed as the main material for the towing line to connect the towed ship and tug boat. The diversity of material e.g. polyester, aramid, and HMPE could impact the behavior of towing system and lead the instability of towed ship. Following the practical method previously proposed for the towing system analysis, authors aim to present a numerical model to properly take into account the characteristics of fiber ropes into the towing system. Specially, the dynamic stiffness of fiber ropes which is determined according to the mean load of the towing line is considered when solving the governing equations in the time domain. A detailed iteration procedure for the calculation of dynamic stiffness is described. The performance of dynamic yaw and lateral offset of towed ship under various wind speeds are discussed. The effect of various types of fiber ropes for the towing line and the initial length is also investigated thoroughly. Results of case study show that diverse material characteristics could influence the ship’s directional stability significantly. The shorter towing line and stronger wind can reduce the fishtailing effect of the towed ship while the longer towing line would make the motion period larger.