ROPE AND ITS CARE

Rope—and a sailor’s mind instantly pictures a ship. Ropes belong to a ship in his mind’s processes and since man launched his first boat on the water, rope has been in one form or another part of a boat’s equipment. Savages probably had ropes before they had boats, but with the development of the boat has come the development of rope into the product of today.

Did you ever stop to think why rope is so much used aboard ships? What are the qualities which make it such a necessary part of a ship’s gear? Ropes are primarily used to transmit power in a convenient way. If sailors could grasp the sail in their hands and clew it up no clew-lines would be necessary. But their arms are not long enough and the power would be spread over such a large area that it would become ineffective. A clew-line concentrates that power from that point of application to a convenient place for the sailor to apply it. An iron rod would do the same thing, you say. Yes, but an iron rod lacks two essential qualities—lightness and flexibility. Flexibility is the cardinal virtue of a rope. When not in use it can be coiled down to a very small space and it can follow the wake of the worst helmsman without fear of breaking its back. A chain is flexible, but its own weight is so great that it is only of value for certain kinds of work.

Ropes are made of organic material such as cotton, hemp, manila, grass, and of metals such as iron, steel, bronze and sometimes aluminum.

The class of organic materials is classified as to the material and the manner in which they are made up. Grass, manila and hemp are spun into rope, while cotton is spun, braided and knitted. Braided and knitted ropes have the distinctive quality of being able to transmit torsional stresses such as a flexible shaft and are used for this purpose in the patent log-line. They are also free from turns, which makes them valuable as signal halyards, though by the use of small swivels this bad feature on spun rope has been overcome for use as signal halyards. When you do use cotton, remember it has a great ability for shrinking. Therefore, do not haul your halyards taut in dry weather and wonder why they parted in the first rain-squall.

If spun rope has ruined so many dispositions by the diabolical turn which it can foul itself into—why use it? Because that very same twist—the cause of so much cursing—is the secret of its strength. Rope is subjected to a tension or pull along the line of its longest axis. The thread is made of little fibres which are twisted together. The threads are then twisted to make yarns or strands and the strands twisted or spun into rope or lines. Rope or lines are made up into hawsers.

Take a coil spring and pull out the ends. If you put power enough on the wire it straightens out. This is exactly what happens when you put a strain on a rope; the twists or turns try to straighten out, and lie in a straight line along the center. But there is yarn already in the center, and the coils are pressing in on all sides, squeezing it more and more as the load increases. Now the reason why the two first fibres clung together when they were twisted was that this same pressure made the friction between the fibres so great that they could not slide by each other. This applies to the many hundreds of fibres which make up the rope as a whole. So the harder the pull the harder the squeeze and the harder it is for them to slip by each other. The fact that some pieces of fibre are first on the outside and then on the inside makes all get an equal share of the squeeze. Why does this not go on indefinitely? Because up to a certain load the tendency to cling together is greater than the reaction from the center, which has to push them apart, but when this pressure or reaction becomes greater than the friction the little fibres begin to slide and the ropes part.

The smaller sizes of spun ropes of this organic class are designated by the number of threads used to make up the rope, such as nine-thread or eighteen-thread line. The larger sizes are designated by the number of inches of circumference, such as one-inch, three-inch, etc. Hawsers are measured by the circumference in inches. Spun ropes are three-stranded or four-stranded. A three-stranded rope is more flexible than a four, but a four has greater surface area for the same strength and weight and therefore wears longer.

Hemp rope is harder and less flexible than manila and is used for standing rigging, while manila rope is used for running rigging.

Grass or coir ropes are used where the rope is submerged often, as they do not rot when damp and can be stowed wet. They are very elastic and are specially used for towing light weights, such as targets in the Navy.

Just a few hints about this general class of organic ropes:

Always dry these ropes before stowing them to prevent rotting.

Protect them from chafing by use of chafing gear or reversing end for end to bring the wear in different places.

Always coil down right-handed or with the sun.

The greater the surface the less the wear on any one strand, so use four-stranded for ropes whose particular wear is from chafing such as anchor warps, for small boats and boat-falls. A small size rope would often be strong enough but would chafe through quicker.

Metallic or wire ropes are generally either iron, steel, bronze or combinations of metal strands spun with hemp or manila strands.

Bronze rope is used for tiller ropes because it is non-magnetic and it will not rust. This is important, as tiller ropes are often in inaccessible places. If it does not pass near your compass and it is out where it can be easily examined and cared for to prevent rusting, a flexible steel tiller rope is cheaper and stronger for the same weight and also wears longer.

Galvanized iron wire is used for standing rigging, and the rusting in places where turns have broken the surface coating, such as around thimbles of an eye splice, should be carefully looked for. Most sailors think it wiser not to paint wire except for decorative purposes. If it is painted be sure to remove all grease and water from the surface.

Steel rope is used for running rigging because of its flexibility and lightness. It is not adapted, however, for small boats.

A combination of alternate strands of wire and hemp is made into rope known as durable rope, and is used particularly for cargo falls and it is more flexible and more easily handled.