Care of Marine Lines and Ropes

Modern rope or cordage used by boaters offers enhanced performance compared to those previously made of natural fibers. Man-made synthetic materials used to produce marine ropes include polyamide (nylon), polyester (Dacron), polyethylene, and polypropylene.
While these new rope building materials are long-lived, resist rot and offer superior strength, they can be damaged or fail from poor use and care. A note on nautical terminology; mariners typically refer to materials on spool and yet to be used onboard as rope, while cordage in use on a vessel is line. Others will refer to rope as anything over 1 1/8 inch in diameter.
Here are a few hints for boaters to improve rope safety and make them last longer:
Application - Rope performance is a product of material and construction method used to manufacture it. Match the rope to its intended application. Nylon lines stretch and adsorb shocks, making the material a good anchor or towline. Double braided polyester represents some of the strongest line available to boaters. The line is flexible and displays little stretch, making useful in mooring and reeving. Use the right sized rope for the sheave in block and tackle gear. The same advise holds true for the use of cleats.
Environment - Proper storage of rope effects its strength and lifespan. Avoid storing rope in direct sunlight. The preferred environment for long-term storage would be a cool, dark and dry space. Protect synthetic from contact with chemicals like battery acid, motor oil or chorine. Keep rope away from heat sources. Examples include exhaust manifolds, friction points and barbeque grills. If possible, don't let a water soaked rope freeze.
Rope Care - Avoid use or storage of a dirty rope. Grit will work its way into rope fibers and cause abrasion. Salt crystals cause the same concerns. Wash rope in warm water and dry them carefully. Reverse the ends of long used lines. Occasionally switch your anchor line end for end to distribute wear uniformly.
Overloading - Boaters need to consider the safe working load of lines used on their vessels. Working load is calculated by dividing the minimum breaking strength of the rope by a predetermined design factor. Design factor is a ratio based on risk and can range from a value of 5:1 to 12:1. Risk of life and property cost will push the design factor used to higher value.
Abrasion - Wear caused by abrasion weakens the strength of a rope. Regular cleaning will keep abrasive grit out of rope fibers. Use chaffing gear at rub points like chocks and where the line crosses a structure at a sharp angle. Ready made chaffing gear is readily available in the marketplace or you can improvise with materials like used fire hose to protect lines. Do not walk on lines.
Kinks - Sharp bends or kinks greatly reduce rope strength. They are caused by repeatedly twisting a rope in one direction. Sailors that correctly coil a line will throw twists in and out of the line as it is laid down. Passing a kink through a restricted space like a pulley will cause serious damage to a line.