1. Can the tensile strength of rope vary from the manufacturer's specifications? The tensile strength is the load at which a new rope will break when it is tested at the factory. Rope strength shown is the approximate average for newly manufactured rope. Age, use, and the type of terminations used - such as knots - will lower tensile strengths significantly.
  2. What does the cordage institute recommend as a safe working load? The Cordage Institute specifies that the safe working load of a rope is determined by dividing the minimum tensile strength by the safety factor. Safety factors range from 5 to 12 for non-critical uses. The working load is a guideline for rope in good condition used in non-critical applications, and should be reduced where life, limb or valuable property are involved, or where exceptional shock, sustained loading, severe vibration, etc. may be experienced.
  3. What are some of the different types of rope?
    1. Twisted Ropes: These are known by their spiral shapes. Rope is made by twisting together individual yarns to form strands, which are then twisted together to form rope. Twisted ropes are easy to splice. Twisted ropes have inherent torque and have a tendency to kink up and rotate when under load.
    2. Braided Ropes: These are manufactured in many variations and braided patterns, but always consist of bundles of fiber which are formed into strands and then woven together by passing each strand over and under the others.
    3. Diamond Braids: Ropes are formed by rotating half the yarn strands in one direction on the braider while the other half rotate in the opposite direction. The cords may be hollow or they may have a center core of parallel fibers. These ropes tend to flatten out more than others.
    4. Double Braid: These ropes are constructed from an inner hollow single braided rope (core) which has another hollow single braided rope constructed around its exterior (shell). The end result is a rope within a rope. Both the skin and the core share the load on the rope, but not necessarily in equal amounts. These ropes are generally very flexible, strong and pleasant to handle. They are easily spliced. 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 result in a dramatic loss of strength by causing the entire load to be applied to the inner core. These ropes are also referred to as "Marine Ropes", "Yacht Braid" and "2 in 1".
    5. Flat Braided Rope: A braided cord construction which is flat and has no core or hollow center.
      f. Hollow Braid: An easily spliced cord of a diamond braid construction or twill braid pattern with a hollow centre; most common in nylon or polypropylene - for example, water ski tow rope.
    6. Kernmantle Ropes: These are made by braiding a cover (mantle) over a core (kern). The core may consist of filaments of fiber lying essentially parallel inside the rope, or it may be twisted or braided into little bundles. The ropes are designed so that the inner core is taking most (often all) of the load, with the outer cover serving mainly to protect against abrasive action, dirt, and UV rays. All other types of rope have the load bearing fibers exposed and therefore deteriorate more rapidly. These ropes are exceptionally strong and durable, and can be made to have very low elongation. All kernmantle ropes have some stretch.
    7. Parallel Core Ropes: These use parallel core construction to maximize core yarn tensile strength conversion. These constructions have a generally stiffer hand and are not easily spliced.
    8. Shock Cord Rope: An elastic cord used for tie-down purposes, snubbing gear, etc. Made of elastic rubber core with a braided synthetic fiber jacket.
    9. Solid Braided Ropes: Rope is made by braiding 12, 18 or 20 strands in a reasonably complex pattern with all the strands rotating in the same direction on the braider. The center of the rope may contain a filler core. These ropes maintain their round shape and therefore work very well in pulleys and sheaves. They tend to have high elongation but generally have less strength than other constructions. They cannot be spliced. These ropes are also referred to as "Sash Braid".
  4. How does one identify the quality of a braided rope?
    1. Broken Yarn Filaments most likely indicate the use of improperly maintained machinery. The result is lower overall rope strength and premature wear.
    2. Looped or Pulled Strands are the result of poor quality braiding, yielding a rope in which all of the yarn strands are not working together equally. This will result in lower strength and premature wear. Looped strands may also snag on anything in the surrounding environment, causing further unnecessary wear and damage to the rope.
    3. Uneven Yarn Color or Sheen most likely indicates the manufacturer has used inferior yarn or clearing lots of yarn. Many manufacturers do this to reduce costs. However, it can result in a variety of problems including reduced or inconsistent strength and premature wear.
    4. Inconsistent Diameter occurs as a result of poor braiding. It may indicate problems with the core of the rope, or the balance of the skin and the core. It will result in lower breaking strength and difficulties if the rope is run through any hardware.
    5. Dirt on new rope, often in the form of grease or oils spots, is an indication that the manufacturer is not committed to quality and inspection.
  5. What is the proper way to store rope? Rope should be stored in a clean, dry, well-ventilated environment, away from direct sunlight, extreme heat, and chemicals.
  6. What are some of the different types of rope fibers?
    1. Natural Fibers (Cotton)
    2. Synthetic Fibers (Dyneema, Kevlar, Nylon, Polyester, Polypropylene, Technora)
  7. What is the shelf life of nylon and polyester ropes? While there is not a universally agreed-upon shelf life for unused nylon and polyester ropes, we suggest a 10 year maximum for ropes that have been properly stored. Exposure to heat, ambient moisture, UV, exposure to higher or lower temperatures and chemicals will reduce the shelf life of the rope.
  8. Do knots affect the strength of a rope? Knots reduce the strength of ropes by up to 50% because they cause the fibers to get distorted and to cut into each other. Some sizes of our ropes can be fitted with swaged eye terminations which are much more efficient than knots, resulting in minimal strength loss.
  9. How do I know my rope is safe for critical applications (e.g. Lifeline etc.)? If any rope is questionable, replace it if it is in a critical application. Watch for these signs:
    1. Evidence of broken fibers or if there are signs of lots of abrasion.
    2. Evidence of melted rope or burn marks on the rope. Signs of melted rope may be evidence that the rope may be weakened.
    3. Evidence of dirt, especially if it has penetrated the inner core of the rope.
    4. Evidence of oil or grease. Often oil contains other contaminates that can damage or weaken the rope.
  10. Is the minimum breaking strength of a rope the same as its safe working load? The rope breaking strength of rope is usually the optimum strength achieved under laboratory conditions at the factory, in accordance with prescribed test procedures, on new rope, pulling at a slow, steady rate in a straight line. However, real life applications normally involve many different types of forces and factors which will cause the rope to fail at much reduced loads. Accordingly, the safe working load of any rope is much lower than its nominal strength.
  11. What is Dyneema® rope? Dyneema® is an UHMwPE (Ultra High Molecular weight Polyethylene) fibre developed by DSM in the Netherlands over 20 years ago. Dyneema® is light weight and renowned as the world's strongest rope.
  12. What makes Dyneema® so special?
    1. High Strength: On a weight-for-weight basis, Dyneema® is 15 times stronger than steel wire.
    2. Light Weight: Strength for strength, Dyneema® is 8 times lighter than steel wire. Dyneema® also has a Specific Gravity of 0.97, which means it floats in water.
    3. Water resistant: Dyneema® is hydrophobic and does not absorb water, thus it remains light when working in wet conditions and is also more durable.
    4. Chemical resistance: Dyneema® is chemically inert, and performs well in dry, wet, salty and humid conditions as well as other situations where chemicals are present.
    5. UV Resistant: Dyneema® has very good resistance to photo degradation, maintaining its performance when exposed to UV light.