Single-Braid Line –
Single-Braid Line appears to have bundles of fibers running diagonally in both directions and woven or braided over and under each other where they cross. It is stronger than laid line, stretches less, and is generally easier to handle. It also is more wear resistant.
Double-Braid Line –
Double-Braid Line has the same appearance as single braid, but inside the braid line cover is another, smaller braided line. The properties are similar to the single-braid line, although sometimes the double-braid product is stronger and has less stretch. Rope manufacturers also offer several special double-braid products with a wear-resistant polyester-braid cover over a braided core of less durable but enormously strong high-tech fiber. The properties of this line come from the core, and it is usually ultra-strong with very low stretch.
Parallel Core Line –
Parallel Core Line is a relatively new line configuration with a wear-resistant braid cover such as polyester fiber over a core of extremely high-strength but somewhat fragile fibers such as Kevlar® or Spectra® running lengthwise inside the cover. No effort is made to twist or braid the core fibers. The integrity of the rope is dependent entirely on the braided cover. The properties of the line come entirely from the high-strength, low-stretch core. The stretch is generally so low that the entire load is taken by the core.
Parallel Core Line
Size and Strength
The final factors that affect the performance of rope are size and associated strength. Generally speaking, the larger the diameter of the rope, the more strength it will impart to whatever line for which it is used. A typical size-to-strength table is shown in Figure 21 for various types of rope. The working or safe load of a rope is 20 percent of its breaking or tensile strength. Usually sizes of rope smaller than 5/8” are given by diameter and called small stuff, while larger rope is measured by circumference rather than diameter. Rope greater than 5” in circumference is called hawser.
Rope Weight & Strength Specifications
|Nominal Size in Inches|
Tensile Strength in Pounds
|Nominal Size in Inches|
Weight in Pounds per 100 feet
provides additional information on strength of knots and splices. Deciding the best type, size, and construction of rope to use for the various functions on your boat is complex and, in many cases, trade-offs must be made. Help in making these decisions can often be found at your local marine supply store.
Boat Handling: Knots and Line Handling
Strength of Knots and Splices
(Percentage of Original Rope Strength)
|Figure-Eight Knot||45%||Overhand Knot||45%|
|Square Knot||45%||Half Hitch||45%|
|Sheet Bend||55%||Anchor Bend||55%|
|Clove Hitch||60%||Eye Splice||60%|
Caring for Rope and Line
Keeping your lines in good condition will ensure that they will perform when needed. This includes:
- making sure that the ends of your line will not unravel.
- protecting them from chafing on surfaces of the boat or dock.
- avoiding situations where lines kink or are required to make sharp bends.
- keeping them clean and avoiding contact with damaging chemicals.
- storing them out of the way of crew who might trip over them.