Know the Ropes
Choosing the right ropes for your boat can become a rat’s nest of confusion. Three strand, laid, braided, hollow core, solid core, single braided, double braided — it’s a challenge to match the right rope to its intended application. An anchor line, a dock line, and a towline each perform a specific function. Get it wrong and your confidence level as a skilled skipper could take a big hit. So could your boat.
To my way of thinking, marine cordage (rope is called line when attached to something) is the most important piece of safety equipment on any recreational vessel. Think where you’d be without anchor rodes and docking and towing lines. That’s why it’s important to know the basics of each rope you need — what it’s made of, its size, breaking point, and if it’s the proper length for the application. The fundamentals apply to both sail and power (line choices really get esoteric for the sailing crowd, particularly racers, but I’m not going there).
Almost all marine rope is synthetic. The most popular is nylon as it doesn’t rot, is incredibly tough, resists abrasion and the sun’s UV rays, is the strongest of the synthetics, and is a bargain to buy. Nylon is the standard for docking lines and anchor rodes because it stretches. Elasticity is important as a boat at anchor or tied up to a dock is in frequent motion from tide, currents, and wind. If a line suddenly tightens, the load on that line goes from zero to maximum and it could break. Stretchy nylon smoothes out the pressure.
Polyester rope has similar qualities to nylon but is softer to the touch and less stretchable. It doesn’t shrink when wet as nylon does, but it is hard to splice. Some rope combines polyester and nylon.
Polypropylene is another synthetic rope material. It doesn’t stretch so it is good for control lines on sailboats like halyards and sheets. It also floats, a desirable quality for towlines used for skiing, wakeboarding, and tubing. However, it is not as strong as the other synthetics.
In the manufacturing process, rope is either laid or braided. Which is better? Even professional riggers disagree. Three strand line, almost always nylon, is rough on the hands — think of hauling in 150 feet of anchor line — and has a nasty habit of catching on pilings.
How strong should safety lines be? It depends upon their purposes. The line attached to your anchor should be as big as your cleats and chocks can handle. Many forces pull on an anchor including wind, current, and displacement, so a rough rule of thumb is to increase the diameter by one-eighth of an inch for every eight feet of boat length. If yours is a heavy craft like a trawler or a full displacement sailboat, be super cautious by starting the count at seven feet. This takes into account adequate breaking point for the rope. Minimal diameter should start at three-eighths of an inch (one-eighth is OK for canoes, kayaks, and paddleboards). Three strands of the same size aren’t quite as strong as braided, so go up one size to be safe. I use the same formula for docking lines even though multiple lines spread the holding power.
How long should lines be? For anchor rodes, it is a matter of scope. Allow a seven to one ratio of the length of line to the depth of water. A cruising type vessel should have a minimum of 100 feet unless all you ever do is drop the hook in shallow water.
When it comes to docking lines, allow a boat length for each line (four bow and stern lines and two spring lines). By the way, keep guests away from a working line under tension. Should it break, the snapback can cause serious injury.
Rope wears out, abrades, and breaks, but except in an emergency, don’t tie two ropes together. The new rope can lose up to 50 percent of its breaking strength. Better to learn how to splice as the loss there is only 10 to 15 percent. Best is to have a backup for every rope aboard.
Check ropes frequently. Sun, sand, and dirt can destroy or severely weaken the fibers, so hose down lines with fresh water at the end of each excursion. Before storing for the winter, pack your lines into a pillowcase and wash it in a top loading washing machine with detergent and fabric softener. Coil and hang on a hook for the off-season.
The author is the Division 5 – Staff Officer Public Affairs, First District Southern Region, for the U.S. Coast Guard Auxiliary, the all-volunteer, non-military arm of the Coast Guard, teaching boating safety education and conducting search and rescue operations. Visit http://cgaux.org/ to join the Auxiliary or for class information.
By William C. Winslow