Marine Engineering and Naval Architecture

There are many different types of rope both in terms of the material and construction used. Outside of the more specialised ropes available the most common materials used are; Polyester.   Polypropylene. Nylon. Materials Polyester and Polypropylene are the most common materials used for towlines. Nylon isn’t generally used by Coastguard as a towline, not because of any issues of strength – in fact Nylon is very strong, and often used in commercial towing. The problem is Nylons capacity for stretch. While a towline needs to be able to stretch to absorb some of the dynamic loading imposed on it, Nylon rope depending on its construction can stretch to an excessive degree (60% + in some cases). The greater the stretch the greater the recoil when a line parts. The danger is not just from the towline, there is also the risk of a fitting such as a cleat being pulled out but remaining attached to the recoiling line. Polyester Stretches approx 25 to 35% of its length. Does

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 harbo