Braided and Plaited Ropes
More recently, the use of modern machinery and synthetic fibers has helped us move beyond the limitations of twisted ropes. Rope-making machines can now weave braided or plaited ropes that come in many decorative patterns, are tightly woven, and don't untwist easily like twisted ropes do.
One example of a braided rope is a “double braid” or “braid-on-braid” rope, illustrated in FIGURE 2-2. This structure is commonly used on more expensive rope, and it is favored for running rigging on sailing vessels due to its excellent knot-holding quality and the way it flattens somewhat to help it grip the surface of a sailing winch.
FIGURE 2-2: Structure of braid-on-braid rope
Unlike twisted rope or many other types of braided rope, braid-on-braid structure has a core that is protected by its outer braid, or sheath. This protection of the core is desirable, but can sometimes make it difficult to detect possible damage. Some “sheath and core” ropes have cores that are not braided but may have any one of many possible structures, even three-strand rope. The core material may be different than the outer sheath, depending on the properties chosen by the manufacturer. The outer sheath may also be chemically treated for particular properties, such as resistance to abrasion or ultraviolet light.
Solid Braid Ropes
When eight, twelve, or even sixteen strands are braided together, resulting in a rope of filled and round cross section (as you can see in FIGURE 2-3), it is called “braided” or “solid braid” rope. When the pattern of braiding causes the cross section to be not quite circular, the rope may be called “plaited.” With this type of weave, every strand passes along the surface as well as through the center of the rope.
FIGURE 2-3: Structure of a solid braid rope
A Variety of Options
The patterns for braided and plaited rope are endless. Some use strands of different colors, and large plaited dock ropes are sometimes even made of strands twisted in opposing directions to make the final product less susceptible to kinks. Some, like polypropylene ski ropes, consist of just a sheath with no core, giving it an easy-to-splice structure similar to finger cuffs. You can even make a braided rope yourself with a pattern like the Three-Strand Braid (described in Chapter 10).
The pattern of weave alone does not determine all the properties the rope will have. Sometimes the fibers are cut into short lengths to give the rope a fuzzy surface for an easier handhold. How tightly the weave is laid affects the flexibility and stretch the rope will have, and of course the material used will determine many of the rope's properties.