Tuesday, May 1, 2018

Crevasse Falls - Do Knots Work to Decrease Fall Potential?

In 2012, the French National Mountain Guide School (ENSA) began to research how knots in climbing ropes decrease the impact of a fall on a climber. Guides have been testing this for years in unscientific ways and have always come up with the same result. Mostly it works.

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:

Aaron Trowbridge said...

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