What are the different types of rope?

There are 2 broad types of rope; braided rope and twisted rope, each of which has very different characteristics. In order to optimize a rope's performance and safety, it is important to select the correct rope construction for a given application.

Twisted Ropes are made by twisting bundles of individual yarns together to form 3 strands, which are then themselves twisted together to form the rope. As the successive bundles of fiber are twisted together, the direction of the twisting is alternated so that the torque resulting from twisting in one direction is balanced against the torque resulting from twisting in the other direction. This counteracts the tendency of the three strands to unwind. These ropes can be recognized by their spiral shape. Some larger ropes may be made up of more than three strands.

Twisted ropes are typically less expensive than braided ropes, because the manufacturing process is faster. Twisted ropes can be easily spliced, however, despite the balancing of torque achieved by alternating the direction of twist, these ropes retain some torque, and therefore have a tendency to kink up, and to rotate under load.

Braided Ropes come in various braiding patterns, but always consist of bundles of fiber which are formed into "strands" and then interlaced by passing each strand over and under other strands. This structure creates a round rope as opposed to the spiral shape of twisted ropes. This round shape makes them well suited for use with hardware such as pulleys, winches, and rope grabs. Generally speaking, braided ropes are inherently torque free and non-rotating. Braiding is a relatively slow process, so ropes made in this fashion tend to be more costly then twisted ropes.

When braiding ropes, there are a number of variables the manufacturer can use to alter characteristics such as strength, elongation, flexibility, and durability. The following is a brief description of some of the more common types of braided ropes.

Solid or Sash Braid ropes are formed by braiding strands of fiber in a reasonably complicated pattern, with or without a filler core in the center of the rope. Solid braid ropes tend to maintain their round shape, and therefore work exceptionally well in pulleys and sheaves. They tend to have high elongation but are generally less strong than other braided constructions.

Diamond Braid ropes are formed by rotating half the strands of fiber in one direction, while the other half rotate in the other direction crossing alternately over and under each other. Diamond braid ropes tend to be flatter than some of the other constructions. Often, a filler is put in the core of the rope to make it rounder and firmer or to build it up to a desired size. Diamond braid ropes tend to have moderate strength.

Double Braid ropes are made by braiding one rope over top of another, so you actually have a rope within a rope. The inner rope and outer rope are generally designed to share the load fairly evenly. These ropes tend to be very flexible, strong and easy to handle. Eyes can be spliced into the ends of these ropes. Double Braid ropes are very popular in boating and marine applications. However, caution must be exercised where double braid ropes are run over pulleys, through hardware or in any situation where the outer rope may slide along on the inner rope and bunch up. This condition, often called "milking", will cause dramatic loss of strength by causing the entire load to go onto the inner rope, because the sheath is bunched up and therefore not under the same tension as the inner rope.

Kernmantle ropes are made by braiding a cover (mantle) over a core (kern). The core may be made of filaments of fiber lying essentially parallel inside the rope, or, it may be twisted into little bundles much like miniature twisted ropes. In some cases it will be made of small braided ropes. Kernmantle ropes are always designed so that the inner core is taking most, if not all of the load. The outer cover serves primarily to protect the fibers of the inner core. If "milking" occurs on these ropes, it does not generally affect strength very much because the rope is designed so that the inner core is the load bearing member. These ropes are very strong and durable, and can be made to have very low elongation. Since the load bearing fibers are inside the protective outer cover, they are well protected from abrasion, dirt, and ultra violet rays. All other forms of rope have the load bearing fibers exposed, resulting in faster deterioration. While kernmantle ropes cannot be spliced, they can be terminated very efficiently with swaged fittings.

Kernmantle ropes are often categorized as static meaning having little stretch or dynamic, meaning they have more stretch. These terms are however, relative since all ropes have some stretch. Kernmantle ropes have their origins in mountain climbing where the higher stretch versions are used to absorb energy if the climber falls. The low stretch versions are used in rappelling, rescue, and in most industrial safety applications where they are favoured because of their inherent toughness and the efficiency with which rope grabs work on them. They tend to be more expensive than other ropes because they are normally made from very high quality fibers and have stringent requirements for care in manufacturing, particularly where they are designed for use in life critical applications. Most of the higher initial cost is offset by their durability, and because one can normally select a smaller kernmantle rope for any given application.

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