Exploding rope myths

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Exploding rope myths
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Naked Bolts
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Karabiners joining waist and leg loops
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Cows tail girth hitched to dog loop
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Energy in the climbing situation

• There are two parts in a climbing set up dynamic
  parts (stretchy) and static (non stretchy) parts.

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Energy absorption and impact force

• The impact force is controlled by three variables
• The Mass of the falling object
• The Velocity of the falling object
• The Time taken to slow the falling object

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Static verses Dynamic rope impact forces

• The dynamic has a long low curve
• The static has a short sharp curve
• The energy absorbed is equal
• But one has a higher impact force

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Fall Factors
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The UIAA test for dynamic ropes

• Fall factor 1.75 Dynamic ropes
• 80kg single ropes
• 55kg double ropes
• Minimum 5 falls
• Max 12 kN impact force singles
• Max 8kN doubles

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Euro norms (EN) for Static

• 0.3 Fall Factor to not exceed 6kN peak force with
  100kg load
• Withstand at least 5 FF1 falls without rupture
  with 100kg load
• Tensile strength of 22kN and 15kN when knotted
  with fig8

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Making sense of the stats
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Tape

• Tape is Static
• Strength shown by contrasting lines

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Karabiners

• 3 load ratings
• Along the length(normal)
• Across
• Gate open

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Karabiners joining leg and waist loops
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3 way loading in use
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Girth hitched cows tail
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The Girth hitch
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Compromising your Tape
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Greater than fall factor 2

• When using a cows tail on a belay chain it is
  possible to create fall factor 2 and greater,
  relatively easily.

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FF2 on larks footed cows tail

• The impact force exceeds 12kN
• You smash your pelvis and have severe internal
  bleeding
• Your harness ruptures
• Your cows tail snaps
• You take a ground fall only to be hit on the head
  by your anchors.!!!!!!

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Recommended cows tail

• This system is as strong as it can be 22-27kN
  (slings and crabs)
• Never go level or above your anchors
• Use dynamic rope if possible to make a cows tail

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dry verses wet ropes

• Water affects nylon in the same way as heat
• Polymers become rubbery rather than glassy
• Performance reduction of up to 70

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UV damage

• 3months exposure at 2550 m 50 loss in
  performance
• 3months exposure at 1834 m 25 loss in
  performance
• Conference on nylon and ropes, Turin 2002
• (Test area was Dolomites)

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Wet and damaged rope

• 70 loss in performance when wet
• 25 -50 loss in performance when it has been
  exposed to UV
• 50 loss in performance when knotted

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Case study

• Start with a sling rated at 15kN x2 30kN
• Form a loop by tape knot reduce by 5513.5kN
• Wet day reduce by 70 4kN
• Exposed to UV reduce by 25 3kN!!!!!!
• Consider a single strand sling
• Consider a 100kg load

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