Page 17 - Rappelling

single rope and no more than 12 percent for a half
or twin rope.
To the best of my knowledge, the only docu-
mented rope failures among UIAA-certified ropes
were ropes that were cut over sharp edges and one
rope with known pre-exposure to sulfuric acid.

Static and Low-Stretch Ropes
For many years the term static rope was used to
define any low-stretch rope typically used as a
rescue rope or as a fixed line for rope access, rap-
pelling, and life safety. As rope manufacturers
developed new techniques and technologies to
create better low-stretch ropes, the terms static rope,
low-stretch rope, low-elongation rope, and semi-static
rope, often used interchangeably, became somewhat
ambiguous, especially since all ropes have some
stretch, so a more precise definition was needed.
The Cordage Institute, an international rope
industry association that disseminates industry stan-
Climbing shops sell static and low-stretch ropes dards, defines two categories of non-dynamic ropes:
from spools, cut to the length you desire. static and low-stretch.
static ropes
then raising it 8 ⁄2 feet above the anchor and drop- Static is defined as rope with a maximum elonga-
1
ping it 15 feet over a 10mm diameter bar (similar tion of less than 6 percent at 10 percent of the rope’s
to a carabiner) that is anchored approximately 1 minimum breaking strength (MBS). New technology
foot above where the rope end is anchored. This allows manufacturers to create ropes with virtually
simulates a fall factor of 1.7 (total distance of the fall no stretch under a person’s body weight rappelling
divided by the length of rope in the system), which down the rope. For example, the Sterling Rope com-
is a very severe fall in climbing situations. pany’s ⁄2-inch diameter HTP Static rope stretches
1
For a single rope, during the first drop the peak only 0.8 percent with a 300-pound load and has a
impact force on the rope is measured and must safe working load (SWL) of 908 pounds, which is ⁄10
1
be less than or equal to 12 kN (8 kN for a half of its MBS of 9,081 pounds.
rope with a weight of 55 kg) with a correspond- A static rope, by definition, is just that—static,
ing stretch of less than or equal to 40 percent. with very low stretch—think of it almost like a wire
Twin ropes have the same requirements as a single cable. Static ropes generally have poor handling
rope but must survive at least twelve drops with- characteristics due to their stiffness and are typically
out breakage. In addition to the stringent drop test used only for rappelling, fixed lines, haul lines, high
requirements, sheath slippage can be no more than lines, and zip lines where dynamic properties are
1 percent, and static elongation under an 80 kg not required. A static rope should never be used for
(176 lb.) load can be no more than 10 percent for a lead climbing or belaying, where it may be subject

6 RAPPELLING

Rappelling_i-174_3pp_CS55le.indd 6 7/24/13 10:14 AM