Introduction to Towline

A tow line is used with a tug (tugboat or towboat) which is a type of vessel that maneuvers other vessels by pushing or pulling them either by direct contact or by means of a tow line. Tugs typically move vessels that either are restricted in their ability to maneuver on their own, such as ships in a crowded harbor or a narrow canal, or those that cannot move by themselves, such as barges, disabled ships, log rafts, or oil platforms. A tow line is the essential link between tug and ship. This applies to tugs operating alongside a vessel in the push-pull mode as well as to towing tugs fastened with a tow line to the bow or stern of a ship, also called `tugs towing on a line‟.

Basic towline requirements

A towline must fulfil two basic functions, firstly to function as the load-carrying link between tug and ship and secondly to cope with the dynamic loads resulting from the relative motion between tug and ship. This leads to the following basic requirements for towlines for harbour tugs:

Strength:- The towline should be of sufficient strength to cope with the forces that can be experienced during ship handling operations.

Stretch:- Dynamic loads should be well compensated by the towline and/or load reducing system on the winch to avoid excessive loads in the towline and attachment points.

Weight/Diameter:- The towline should be manageable on board the tug as well as on board the ship. When no towing winch is used the towline should be flexible enough for easy handling.

Life:- When in use the towline should suffer a minimum of wear, distortion and loss of strength providing a the longest possible useful life.