There are myriad choices in dock lines. Just as there is no perfect boat, there is no perfect type of line for use in tying a boat to a dock. That said, the following tips are intended to help you make more informed choices when selecting dock lines for your boat.
Nylon is the best choice for a dock line, in my opinion. It offers good resistance to the sun’s rays, fuel and chemicals. It stretches 15 percent when loaded to about 20 percent of its breaking strength, providing shock absorbency. Dacron lines soon become too stiff, and polypropylene lines degrade rapidly in sunlight.
Bigger isn’t necessarily better. Larger-diameter line won’t provide as much cushion as thinner line under equal loads. It may also be cumbersome to fit around existing cleats. As a rule of thumb, use 1/8-inch diameter for every 2 inches of boat cleat length.
For your home slip, cut and splice the lines to length to suit the tidal range or expected water level changes. For use at transient docks, we recommend that spring lines be as long as the boat and that bow and stern lines be half the length of the boat. You can always deal with some excess line, but a too-short line can be useless.
Less expensive than braid, tougher on the hands and available in limited colors, three-strand nylon provides excellent shock absorbency. When used over wood pilings or poles, three-strand nylon slides down and/or around such pilings easier than other types of line do. It’s also easy to splice, if you want to make custom-length lines to suit your boat and slip.
More expensive, double-braid line is soft on the hands and supple to coil; it also comes in a kaleidoscope of colors to match your boat. Double-braid provides less shock absorbency because it stretches less than equivalent three-strand line, and, for lines used around pilings, the fine weave may snag, making loops recalcitrant to drop or slide into position.