Characteristics of dynamic climbing ropes

neil — Wed, 27 May 2009 12:13:49 GMT

Current revision posted to Knowledge by neil on 27/05/2009 13:13:49

Characteristics of a dynamic climbing ropes

Filed under: Climbing Rope

Number of bobbins

The sheath encircles and protects the rope’s core, it is the visible part. It is formed from groups of filaments: each group woven from a bobbin. For equal diameter, a larger number of bobbins give better dynamic characteristics, and a smaller number of bobbins give better abrasion resistance. Thus one chooses a single rope of 48 bobbins construction for dynamic performance ( Beal TOP GUN II) or of 32 bobbins to maximise abrasion resistance (Wall Master V) by using thicker filament.

Diameter and weight

Ropes of large diameter generally have a longer active life, but they are heavier and less manageable. On routes where weight and ease of running are important, it may be preferable to choose a thinner rope.

Impact force

Values required by the Standard:

Single rope: Impact force lower than 12kN holding the first factor 1.77 fall with a mass of 80kg.
Double rope: Impact force lower than 8kn holding the first factor 1.77 fall with a mass of 55kg.
Twin rope: Impact force lower than 12kN holding the first factor 1.77 fall with a mass of 80kg, on two strands.

The impact force printed in the technical notice must not be lower than the poorest result found by the certifying laboratory.

Number of UIAA Falls Laboratory

To satisfy the Standards, single rope must withstand 5 successive factor 1.77 falls with a mass of 80kg; double rope 5 successive falls with a mass of 55kg; twin ropes 12 successive falls with a mass of 80kg on two strands. The number of falls shown on the technical notice must not be higher than the poorest result found by the certifying laboratory.

Sheath slippage

The core and the sheath of the rope are two independent components which have a tendency, if the construction is not carefully matched, to dislocate and slide against each other. The sheath deforms and little by little under the effect of the descender it bunches, creating a slack zone around the core and bulge points: the sock effect. This phenomenon results in more rapid wear, particularly with top-roping or other intensive use, it also risks jamming in descenders or belay devices.

Dynamic elongation

This is the stretch of the rope during the first UIAA test fall. It must be less than 40%.

Static elongation

Measured under a load of 80kg it must not exceed 10% for single rope, 12% for double rope, and 10% for two strands of twin rope together