Development of a Towing System Design Program Based on the U.S. Navy Towing Manual

Marine towing is required for transporting ships and floating structures and for salvage operations of damaged vessels. Safe towing operations require the estimation of towing resistance, selection of an appropriate tug and towing equipment, and verification of the towing system. However, the design procedure based on the U.S. Navy Towing Manual involves repeated manual calculations using tables, curves, and empirical criteria, which can be time-consuming and prone to reading errors. In this study, a towing system design program was developed based on the U.S. Navy Towing Manual. The procedure was divided into four modules: steady-state towing resistance calculation, tug selection, towing equipment selection, and towing system verification. Tabular data were implemented as look up data structures, while graphical data were digitized using polynomial regression and natural cubic spline interpolation. The developed program was applied to a manual example, and the results were consistent with the manual calculation, confirming that the program reproduced the manual-based procedure.