Choosing the right line sounds simple until you stop to think about all types and functions of lines found on big boats, little boats which vary from high tech to low tech and everything in between.

Cordage is a term that includes all the different types of line on a boat that you use to winch sails in, cleat the boat fast to the dock, raise the anchor, and from time to time, perhaps even use as a belt in a pinch. The wide variety of tasks a line might be used for aboard a boat means the manufacturers are continually providing the consumer with knowledge about the ever increasing variety of both construction and material styles--knowledge that sometimes ends in confusion not only for the novice, but the seasoned cruiser and racer as well. There are tried and true staples like nylon and Dacron and more exotic lines like Spectra and Vectran. Today’s new fibers are stronger and more durable if used for the right application. Here’s a quick review of some of the more popular fibers and their uses:

Nylon is not only strong, but it also stretches. This makes it great for docklines and anchor lines where you need not only holding power, but also some stretch to absorb the shock loading that can occur on a rough mooring or windy dock. There are several different styles but the two most popular are the double-braid construction and three-strand construction. Double-braid provides a more flexible and easier line to handle. Three-strand becomes stiffer and harder to handle with age but provides greater durability and value. Three-strand is great choice for anchor lines and backup docklines, while double-braid makes for great docklines. Do not use nylon for any of your main or jib halyards, sheets or other control lines as the stretch will be far too great.

Dacron or polyester is the second most commonly used material. Dacron is the same fiber used in many of our sails and has a much lower stretch factor than nylon. The same property that makes the fiber good for sails makes it a good choice for control lines like jib sheets, mainsheets, traveler control lines and spinnaker halyards. The predominant style of construction is double-braid, but you can also find it in a three-strand construction and also an eight-plait braid. Three-strand is usually used by sailmakers for boltropes but the traditionalist will enjoy its original look too. The eight-plait construction was made to increase the flexibility, making it easier to handle. It’s very popular for use in mainsheets and other block and tackles, but with its open lay it is not a good choice for jib sheets or any use that has the line running across masts and rigging. It’s also not a good choice for docklines, as any line with a low-stretch factor means maximum cleat tweaking at the dock.

The wrong kind of dockline will bring lots of creaking and squeaking if there’s any kind of surge. Nylon docklines like these have a natural shock absorbing tendency.

The next most popular material is likely Spectra or Dyneema. The durability and strength of this product has just about eliminated the use of wire halyards aboard many boats. Spectra reduces stretch and weight for halyards, spinnaker sheets, and afterguys. Spectra is also found in a twelve-strand product for the ultimate strength-to-weight ratio. Spectra is so durable and strong that it is starting to be used for replacing vinyl-coated lifelines. The twelve-strand construction also allows for easy on-the-spot splicing. If you’re serious about keeping weight aloft and windage to a minimum, Spectra is so durable that you can even remove its cover for additional weight savings on halyards and spinnaker sheets. The one drawback to Spectra is that it’s very slippery and known to creep or stretch slightly under very high loads. It’s not the perfect choice for a halyard or spinnaker afterguy that you really want to stay put.

For those lines that you really don’t want to stretch or creep, consider selecting a fiber called Technora, a high-tenacity aramid fiber, eight times as strong as steel and three times as strong as fiberglass, polyester and nylon of the same weight. It’s a great product for jib halyards, afterguys, and even jib sheets or any line that requires minimal stretch at any load. Manufactures have created blended cores of Technora that keep its price reasonable for this level of product.

Next in the no-stretch, no-creep category is Vectran which is a liquid crystal polymer exceeding stainless steel in the no-stretch category. Vectran has great abrasion and heat resistance which will allow it to last longer and remain stable under sustained loads. Uses for Vectran cordage include backstays, primary jib halyards, and even standing rigging applications.

Now that we understand some of the available materials (and, yes, there are even more out there), we need to spend some time considering line construction too. How a line is constructed impacts its performance and longevity. To keep it simple, we will discuss double-braid, twelve-strand and then some combinations that have a core made of one material and the cover of another material.

Double-braided lines have a braided core and a braided cover, both braids are usually the same material (Dacron/polyester) but the cover braid might have other materials blended in for additional softness or coloring for identification. With the core and cover being similar materials, the splicing required is a basic double braid splice.

Combination braids are lines with a cover out of one material and core out something completely different. With high-tech cores being as strong as they are, it makes sense to cover them with a more durable and less expensive polyester cover. For dinghies, the cover will be made of polypropylene or Olefin for additional weight savings and to also eliminate any additional weight from water absorption. Owners of larger boats should beware of these types of lines: while their weight and strength are very appealing, these lightweight covers can melt under the load and friction from a winch. Combination braids all have very high tensile strengths, and require special core to core splicing. By tying a knot in these high tech braids you forfeit 50% of the line’s tensile strength. Unless you are very good at splicing, allow a professional rigger to do the splicing for you.

The last styles are twelve- and eight-strand hollow braids. These lines are usually made out of a single material, but there are some blends starting to show up as well. Polypropylene, Dacron, Vectran, Technora, and Spectra are all now being used. Polypropylene is used primarily on ski ropes and makes for a great tether for safety gear and for towing dinghies as well. Its best characteristic is that it floats, thus making it great for the man overboard buoy or pole. These stranded coreless lines are light, strong, pliable and simple to splice. Use high-tech materials to replace wire, or down size line diameters to save weight. Use the blends or Dacron for mainsheets or other block and tackle systems when you want the line to run through blocks without hackling.

Higher performance boats demand higher performance line. Here’s the arrangement found on a J/105 backstay. The grey line eliminates windage aloft while the green braided line running through the blocks presents a diameter that is easier to work with.

Now, let’s put all this knowledge to use and figure out how much you’ll need. With any rigging on a boat it’s always best to measure the length of line that you know works and duplicate those ‘finished lengths‘. I call them ‘finished lengths’ because if you have splices on the end you will need to add the appropriate length of material to make the splice. A good rule of thumb is to add 1.5 feet for a standard double braid splice, while adding 3 feet for a core to core splice is sufficient. If you can’t measure your existing lines, here are some very basic rules that will work. Genoa and spinnaker afterguys should be about 1.5 times the length of your boat. Spinnaker sheets should be twice the length of your boat. For spinnaker and jib halyards there is a rigging dimension call the boat’s "I" dimension, or the measurement of the masthead above the deck. Once you have this dimension, double it to get the line up and down the mast and then add the distance from the base of the mast to the winch or termination point on deck. Mainsheet lengths are slightly harder to determine, but if you determine the distance with the boom all the way out for a run and then multiply that by the number of purchases, the result should provide you with good length.

Selecting the proper line diameter will depend on material strength, rope clutch, self-tailing winch and finally, your hands. The new materials are strong enough to allow downsizing the diameter from your existing lines, but be aware that you might need to modify the cams in your existing clutches if you do. If your boat doesn’t require winches and your hands are your winches, 5/16-inch (with good pair of gloves) is as small a diameter you would want to handle with any load. This is definitely a personal preference and if comfort is a concern increase the diameter for easily handling.

As for load, most manufactures suggest using a line at about 20-25% of its tensile strength. There is a very simple calculation that’s based on sail area and wind strength you can use, but remember it doesn’t account for the displacement, nor the stability of the boat which will impact the ultimate load the line will experience. One of the leading cordage manufacturers suggests the following formula: square the windspeed and multiply by .004, then multiply this number by the square footage of the sail. The result is the load the halyard or sheet will experience. We hope this clears up some of the mysteries about cordage and will help in making a better selection.