“Kern” is German for “core”. The Kern is the inner core of the rope.  This is where the rope gets its strength (upwards of 80%).  It’s made up of a number of fibers, depending on the thickness.  These fibers can be straight or they can be twisted into a number of little bundles inside.  The amount of twist in these inner bundles will affect how much the rope can stretch.

The straight-fibered kern is “static“.  This is what we use in rescue ropes because it does not stretch the way the dynamic does.  When hauling a patient up a slope or creating a high line, we do not want to have to pull all that extra stretch out of the rope before we even start to move the load.  Add into that a mechanical advantage, and we’re really dealing with a lot of elongation and greatly reducing our team’s efficiency.  More than just being a nuisance, this excess elongation can be dangerous for the rescuers, especially in a high angle situation with an edge transition.  The trade-off is that these static kernmantle ropes do not withstand the shock of a fall as effectively, for that very same reason.  Often this static kern will be made of polyester.  Polyester is the favored material because it does not stretch as much as the nylon does.  Additionally, the polyester fibers are more resistant to UV damage and chemical damage.

“Mantel” is German for “coat”.  The mantle is the outer layer of the rope.  Though it may provide some strength, the main strength of the rope lies within its core.  The chief purpose of the mantle is to protect the inner fibers (kern).  It’s a thin layer of tightly woven material, often an abrasion resistant polyester.  A very tightly woven mantle will increase abrasion protection, but will also be less flexible and harder to tie knots.

Your team will need to determine the amount of elongation (stretch) that’s acceptable for the application.  It’s a balance between acceptable impact force upon a shock, and the amount of stretch, which not only decreases efficiency but also can cause danger to your team.  The best system will be one which will arrest a fall as quickly as possible, while also staying below the maximum force on your system’s components.  Remember that the more the rope stretches, the further your haul team will have to pull before the load makes progress. (Requirements of size, strength, elongation per use/situation can be found in NFPA 1983)

Regardless of kern type, each time a rope is bent or twisted it is degrading the strength of the rope.  Think of a running track; as the lanes go around the bend, the distance of the outer lane is greater than that of the inner lane.  As the rope is folded back on itself, the curve’s outer fibers in the kern are stretched while the inner fibers are slack.  This means that not all fibers are holding the same load, if any, and the strength is lessened.  The strength of the fibers inside the rope lies in their “tensile” strength (longitudinal).  This is why we will always try to use knots that will put the least extreme bends on the rope.  The family of figure 8 knots have relatively gentle bends, and are a good bet.

NFPA 1983 provides life safety rope performance requirements.  In this standard you will find requirements for Technical use, General use, and Escape use ropes/hardware as to size and breaking strengths.
http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=1983   “Rescue personnel can elect to use either Technical or General Use labeled equipment based on anticipated loads and acceptable safety margins as established by the authority having jurisdiction (AHJ). This choice should be based on the levels of operational capability of the organization. The AHJ should compile and evaluate information on the comparative advantages and disadvantages of the rope and equipment under consideration.”   ~NFPA 1983

In this field, we also use water rescue rope.  This is a rot-resistant, floating kernmantle rope, the sort that you’ll find in throwbags.  Often these ropes will feature a polypropylene -mantle.  Water rescue ropes are designed for water rescue applications and should not be used in other situations, such as access, escape, firefighting, or other work at height applications.  To learn more about our water rescue class offerings, check out our Swiftwater Rescue page.

Check out our Resources page for some links to quality rope manufacturers.  For a quote on a rope purchase, please visit our Contact page.

… As you arrive on the scene of the embankment, you realize that you’ll need to bring the patient back up to the top of the slope.  A member of your crew reaches into the compartment and grabs the 300′ kernmantle rope-rescue rope in the red rope bag.  You feel confident in this rescue, knowing that your community and department has outfitted your crew with the gear it needs to get the job done safely, and that your team is trained.  As your crew sets up the lowering system you set yourself a line and take your place as an edge attendant.  You assure the patient that help is on the way and explain to him what’s happening.

It’s a bit of a slippery mess for your litter team of 3 to reach the patient, but they manage to reach him and secure him before he slides further down toward the river.  Your haul team signals to you that they are ready to raise.  The litter team assures you that they are also ready.  You radio to begin raising, slowly.  The litter team is having a hard time on the sloppy mud slope, slipping and sliding with each step.  They are having trouble getting around some brush.  You turn to tell the haul team to slow down even more, when you hear a gasp from down the slope as one of your team members loses their footing – the rope holds firm; it has been designed to endure these kinds of shock loads.  You quickly call an “all stop”, allowing the litter team to regroup.  Once they’re ready you begin to slowly raise again, helping your team as they round the edge of the embankment.  The ambulance has arrived on scene during the raise and are ready to transfer your patient.  Your team breaks down the system and returns to the station, muddy, but happy: a job well done.

Choosing the correct equipment for the job will go a long way for the safety and efficiency of your rescue operation. Know your gear and understand why your team uses what it does.  And, as always,

Stay Safe,

PRO Instructor

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