Thursday, March 27, 2014

Use The Rope To Tie Into Anchors

Testing the strength of falling directly onto slings, is a good reminder that your PAS/daisy chain is great if you're going to keep it tight at all times. Attaching your rope to a Master Point made with slings, is a good way to absorb falling forces. It also appears that clove hitches and overhand knots absorb the forces too. And nylon absorbs forces more than Dyneema. (Watch the video at the link for a detailed explanation.)

"Carrying out a final test replacing the slings with 8.2 mm rope for a worst-case scenario with a fall-factor two clearly showed – as expected – that utilising the shock absorbing properties of your rope dramatically lessens the impact forces on the anchors and is the best option. This could be by either clipping the anchors directly with the rope or into a central point in the system. For a full explanation and examination of the results watch the video...The results show how very high forces can easily be generated using slings to attach to anchor points if there is slack in the system. Clearly, it’s important to be aware of this if for example, you are moving around at a stance while clipped into an anchor using a sling or rigging a multi-pitch abseil. For perspective, most leader falls are between 4 – 7 kNs. Forces above 10kN may cause internal injuries – 10kN equates to 1 metric tonne."

Sling Set-upMaterialFF1 (Force kN)FF2 (Force kN)
Overhand KnotsNylon8.811.1
sling broke
sling broke
Clove HitchesNylon913.1
sling cut a bit
a bit of melting
slippage of hitches
‘Self-Equalising’ (Sliding X)Nylon11.519.7
Equalised with Overhand KnotNylon10.815.5
sling broke
Clove Hitches + Anchor Point FailNylon5.5-
‘Self-Equalising’ (Sliding X) + Anchor Point FailNylon10.2-
Equalised with Overhand Knot + Anchor Point FailNylon7.1-
Dynamic Rope (Pair of 8.5mm tied off with clove hitches)Dynamic Rope-7.6

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