Page 31 - Rappelling

generate heat, which could potentially weaken the Cord and Cordelettes
sling.
Both Spectra and Dyneema fibers do not retain A good all-purpose cordelette is 7mm diameter
dye and cannot be colored, so the fiber is distinctive nylon cord, about an 18- to 20-foot length tied into
in that it is always white. Manufacturers add a blend a giant loop with a double fisherman’s knot. I prefer
of nylon to Spectra and Dyneema, usually in a dis- a length that allows me to double the cordelette
tinctive border pattern, and my guess is that in the within the span of my outstretched arms. My favor-
future we’ll see more nylon in the mix. The Meto- ite brand is Sterling, whose 7mm diameter nylon
lius company recently came out with 13mm width cord is rated at 12.4 kN (2,788 lbs.) and tests over
slings that are a blend of 36 percent Dyneema and 5,000 pounds when tied into a loop with a double
64 percent nylon. fisherman’s knot.
When using Spectra or Dyneema slings, think Cordelettes made with a Spectra or Dyneema
of them like a wire cable—they have no stretch, core and nylon sheath have incredibly high strength
even with nylon blended into the weave. Avoid and low stretch. Pound for pound, Spectra and
tying knots with them—it can be almost impossible Dyneema are stronger than steel (and is the mate-
to untie a simple overhand knot in the newer, thin- rial used in body armor for the military), but both
ner Dyneema after it has been seriously weighted. Spectra and Dyneema lose an appreciable amount
Wild Country warns that the material loses a hefty of strength when tied with knots. Because these
percentage of its strength (around 50 percent) when cords are so light and strong, with less bulk to
tied in a simple overhand knot or girth-hitch—a carry, they have become popular, especially for
property that nylon does not possess. The best way rock climbing. The Bluewater company markets
to use a Spectra or Dyneema sling is clipped to the 5.5mm diameter Titan Cord, with a Dyneema
carabiners. If using them in a sling-to-sling configu- core and nylon sheath, rated at 13.7 kN (3,080 lbs.).
ration, either basket one sling over another or use a They say its “combination of high strength, low
properly tied girth-hitch. elongation and light weight provides superior char-
When buying slings for rappelling, 1-inch or acteristics over other combinations. Dyneema does
11 ⁄16-inch width tubular nylon webbing will be the not lose significant strength with repetitive flexing
most versatile material for rigging rappel anchors, and offers a huge increase in abrasion and cut resis-
as it can be cut to a desired length and tied with a tance over other materials. Bluewater Titan Cord
water knot. Double-length (48-inch) sewn nylon can be cut and sealed with a hot knife. We recom-
slings are also handy for tethering into anchors mend a triple fisherman’s knot for tying 5.5 Titan
and extending your rappel device away from your into loops.”
harness. Any sling you purchase for rappel anchor In recent years high-tech cords utilizing aramid
rigging should have a minimum strength rating of fibers (namely Technora) for the core, with a nylon
around 14 kN (3,147 lbs.). sheath, have become popular. Aramid fiber has
Recent studies show that dirty slings are weaker extraordinary tensile strength (stronger than Spectra
than clean ones. The Mammut company suggests that or Dyneema) with low stretch and an extremely
“to maintain the quality and safety of your slings, you high melting point (900°F), making it difficult to
need to clean them regularly.” Mammut recommends cut and melt. I’ve found that the best way to cut it
to “clean soiled slings in hand-hot water with a small is with wire cable cutters. Then I milk the nylon
amount of mild detergent or in a delicates machine sheath over the end and seal it by melting the nylon
cycle up to 30°C (86° F). Rinse in clear water. Leave with a lighter. The Sterling 6mm Powercord has
to dry in shade.” a Technora core and nylon sheath, with a single

20 RAPPELLING

Rappelling_i-174_3pp_CS55le.indd 20 7/24/13 10:15 AM