Rescue Rope Frequently Asked Questions

Written By: Lance Piatt

The following information is provide by Sterling Rope

See Previous article Rescue Rope Construction

1. What is a Marathon Sheath anyway?

The Marathon Sheath is a Sterling Innovation. This sheath uses heavier denier nylon than any other dynamic rope on the market. We do this to enhance the rope’s durability and longevity.

2. What is DryCore™?

DryCore is our unique nylon core construction that reduces yarn on yarn abrasion of wet nylon fibers, helping to maintain the original strength and elongation characteristics of our ropes. Only Sterling ropes have DryCore™. Please note that DryCore™ does not guarantee you rope will staydry, but that when the rope is wet the fibers will maintain more of their strength and stretch.

3. What happens to my nylon rope when it’s wet?

Nylon fiber is affected by the absorption of water. Nylon is hydrophilic meaning it will absorb water.The overall strength and stretch can be greatly affected by moisture in the fiber. Whenever possible try and keep your ropes away from water and as dry as possible. Our in-house testing shows that loss of strength in wet ropes may be as high as 70% in nylon ropes without DryCore™ but only 40%in ropes with DryCore™. A 11mm Drycore™ rope that holds 11 falls dry, holds 7 falls wet. That Same rope without DryCore™ may hold only 3 falls when wet. In general the data shows that the loss of strength through the presence of water in nylon ropes is significant. The good news is that nylons original strength and elongation returns when the rope dries.

4. What happens to my polyester rope when it’s wet?

Remember that polyester is hydrophobic (literally “scared of water”) and does not absorb nearly as much water as nylon and therefore is not greatly affected by being wet.

5. How should I wash my rope?

To clean rope use Sterling’s Wicked Good Rope Wash™ or rinse in warm to hot water. Machine washing is acceptable. Best is to use a front-load machine. We do not recommend using a top loading machine as the rope could damage the agitator or vice versa. The temperature of the water is not a major concern as nylon or polyester are not much affected by heat until around 300 degrees and it would be difficult to get a machine that hot.

6. How should I coil my rope?

To minimize twists and kinking, the best method for coiling your rope is a butterfly coil over your neck or hand or leg. It is important that each coil is alternatively laid down from left to right without twisting. At the end of the coil belly wrap the left and right sides together and pull a bight through the hole in the top of the coil and push the loose ends of the rope through the bight. If the ends are left long enough you can wear the butterfly coil like a backpack.

7. How should I uncoil my rope?

Ropes are hanked twist free at the factory. In order to avoid unnecessary and annoying kinking during its first use it is necessary to properly unhank the rope. To do this, hold the coil of rope in one hand and take one free end. Begin uncoiling that free end three or four twists and drop to the ground. After you have taken three or four coils off the hank, move the remainder of the rope to the other hand and begin uncoiling from the other direction. After three or four coils on that side, switch again. Repeat until the entire rope has been uncoiled. After uncoiling run the rope through your hands meter by meter two or three times to remove excess twist. This will also help you inspect the rope. Now the rope is ready to be used or flaked into a rope bag.

9. How do I know if I should still be using my rope?

  • Inspect your rope often and thoroughly.It is important to inspect your rope thoroughly before and after each use. This should be done both visually and by sliding the rope through your hands meter by meter. If your rope is excessively abraded or you have core coming through the sheath it is time to retire that rope. Often ropes wear faster on the ends from repeated short falls and tying and untying. It may be possible to cut out the damaged section of the rope and continue using the good section.
  • Do not step on your rope Stepping on a rope, while not so bad in itself, can cause dirt and crystals to get forced through the sheath, abrading the core with each use.
  • Keep your rope clean Use a rope bag and wash your rope every 30 to 40 uses.
  • Know the condition of your rope and be wary of lending it out.It is important to inspect the rope when new and continually inspect it during use. We recommend keeping a rope log in order to track the uses and abuses to your rope. Remember that every fall lessens the amount of impact a rope can later absorb. Often a rope used for sport climbing will be subjected to repeated shorter falls. While the rope may not show as much wear from these falls, the cores are being frequently loaded and its ability to cushion your falls will be affected. It is important to inspect the ends of a rope and remove them if they are soft. Please be aware that during each fall the entire rope is being loaded and just cutting off the ends does not give you a new rope.

10. What chemicals are bad for my rope?

It is best to assume that all chemicals are bad for your rope. Do not expose your nylon or polyester ropes to chemicals. That said, much recent data has been collected regarding how substances affectrope life. Data available from Honeywell Corporation (makers of nylon 6, polyester and Spectra®)shows that nylon’s strength is not greatly affected by motor oil, mineral oil, salt water, Freon, gasoline,kerosene, benzene, chloroform, paints, pine oils, or insect repellents containing DEET. Chemicals that should be avoided at all costs are bleach and sulfuric acid. Still even with this reassurance it is best to protect your rope from any exposure to any acids or alkalis and to store your rope in a cool dry environment.

11. How much strength does my rope loose when I tie it in a knot?

There are a lot of publications available that contain information about knots and knot strength. For That reason we will not include much information here, except to say that knots reduce the overall strength of a rope. Therefore, whenever possible use a tensionless knot around a cylindrical object with at least a 4’’ diameter. Four inches is the magic number for maintaining full strength in a rope up to 5/8’’. Any bend tighter than 4’’ reduces the strength of rope because they stress the rope in flexure, thefibers’ weaker direction. Here is a list of some common knots and the translating remaining rope strength.

Knot Strength

  • NO Knot 100%
  • Double Fisherman’s 65-70%
  • Bowline 70-75%
  • Water Knot 60-70%
  • Figure 8 75-80%
  • Clove Hitch 60-65%
  • Fisherman’s 60-65%
  • Overhand 60-65%

12. What is Impact Force?

Impact force is the force felt by the climber or rescuer and equipment at the termination of a fall. It’s Also the number that is used to show a rope’s ability to absorb the energy created during that fall. A Fall on static rope with little elongation and a fixed anchor point will generate much higher impact forces than a fall on dynamic rope using a running belay. There are two measures of impact force.Theoretical Impact force is the impact force without any extraneous variables. Actual impact force is the force created when you take into account a dynamic belay and friction developed over both the carabiners and rock. The UIAA mandates that the impact force generated on the first fall must be less than 12k for a single rope. This test uses a static belay with a fall factor of approximately 1.8 or a 4.6meter (15’)fall on 2.5 meters (8’) of rope. This test demonstrates a very severe fall and generally is not applicable for real world climbing situation but does give a good basis for comparing the relative elongation characteristics of different ropes. Real world experience has shown that rarely are impact forces higher than 10kN generated during a climbing fall. Again, in order to limit the impact force is it important to place protection whenever possible and to utilize a dynamic belay.

13. What is Fall Factor?

Fall Factors are something that every rescuer and climber should understand. Understanding fall factor will help a climber/rescuer determine when and how often to place anchor points. Because itis impossible to fall farther than twice the length of the rope the highest possible fall factor is 2 (except via ferrata). A fall of 8 meters on 4 meters of rope (8 divided by 4) is a fall factor 2. So is a fall of 40mon 20m of rope (40 divided by 20, fall factor 2). It is important to remember that fall factor is not the only determinant when calculating impact force; overall length of the fall, friction from anchors, weight of load, as well as the manner of belay (whether dynamic or static) also greatly affects the impact force. In order to limit the impact force created is it important to place protection whenever possible and to utilize a dynamic belay.

Fall Factors

14. How many meters to feet?

1 meter = 3.28ft

15. How much is a Kilonewton?

1 kilonewton = 224.82 Lbs Force

16. What is “sharp edge resistance”?

There are no documented cases of a rope breaking under “normal use”. The documented occurrences of rope breakages in the field are attributed to pre-exposure to sulfuric acid or by being cut bya sharp edge. UIAA just recently added an optional test to UIAA 101 for testing to sharp edge resistance (UIAA 108). Many manufacturers are claiming sharp edge resistance for their ropes. The designation of sharp edge resistance is not a guarantee of safety. These ropes can still be cut. Our inhouse testing shows that slight variables in the testing procedure can cause even “edge safe resistant”ropes to break on the first fall. We have recently received a letter from APAVE, the UIAA Approved Lab that we use for testing, that their “insurance company strongly recommend us to inform our customers that this test does not reproduce the reality and that the behavior of a rope in contact with a sharp edge can be radically different from the UIAA 108 test conditions and results.”

17. Average vs. Minimum Break Strength 

Average breaking strength is determined by averaging the samples in a given test. Minimum breaking strength can be figured several ways, either using the true minimum number that was recorded during a testing sample or more commonly by using a statistical method such as 3-Sigma.

18. What is a 3-Sigma Rating?

3-Sigma ratings are used throughout the climbing and rescue industries to determine a level of accuracy in the breaking strength numbers that we report. A 3-sigma rating is much more reliable than, say, an average strength where 50% of a sample could be below that strength. 3-sigma ratings are based on a statistical analysis of the breaking strengths of a given sample of rope.Statistically speaking a 3-sigma rating means that 99.9% of the products are stronger than the reported MBS rating. What this means is a 3-sigma rated MBS is three standard deviations below the average breaking strength. Standard deviation helps to define the spread in the distribution of a given test sample. It is not the mean. Reporting 3 sigma ratings more accurately represents a ropes strength to be at least the MBS reported.

19. What are Safe Working Loads (SWL)? 

Safe working loads for rope are usually described as a ratio of the MBS to load of a rope.Depending on industry the SWL varies. The NFPA recommends a 10 to 1 SWL for life safety rope.The National Association of Tower Erectors recommends a SWL of around 15 to 1. OSHA recommends a 10 to 1 ratio as well.

20. What’s the difference between a bi-pattern and bi-color?  

Bi-pattern ropes are a pattern shift in the middle of the rope. Neither the color nor yarns change.Bicolors are produced by changing the yarns in the pattern to a different color yarn at the middle of the rope by using an air splice technique.

21. Why does my BiColor rope have fuzzy bumpy yarns at the middle mark? 

Air Splices.are those fuzzy bumpy spots. An air splice is the joining of two yarn ends by means of high-pressure air forced around the ends causing them to entwine and snarl together. Air splices are essential to join strands into usable lengths. From a life safety perspective two yarns air spliced together test out to be 50% stronger than continuous straight fibers because they have twice as much yarn in the section that is air spliced.


Peace on your Days



About The Author: