The difference between a guide does in a training and what ENSA did is that ENSA took a scientific approach to the question. They used a load cell to measure the force...and what they found wasn't terribly surprising. Knots do help...
Check out the following video for more:
In review, they found that bulky knots are better. They recommend that you use a figure-eight on a bight rethreaded through itself. Most American guides have been using butterfly knots, but this video may have a long term impact on that methodology.
They found that in icy conditions, knots don't help that much.
And they recommended the following distances for rope between knots:
It should be noted that they style in which you elect to haul someone out of a crevasse may be determined by whether or not you have knots in your system. If you intend to use prusiks and a single haul system, knots may hinder these things. It's important to make sure you have a plan for extraction (a drop loop works well) if you put knots in your rope.
--Jason D. Martin
1 comment:
I saw this video earlier this yr and found it very compelling. I'm also intrigued about use of prussik as a sliding belay not just during rescue but travel to adjust spacing middle person in a group of three. I tried that once years ago in a group of three while travelling a very broken and complex icefall on skis. As the middle man I had prussiks set front and back and was able to adjust slack on both sides while partners were weaving through tight areas and I could not physically move without increasing danger. I'd never seen reference to such a technique until seeing another ensa glacier video
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