Grant Prattley

Founder and consultant at Over The Edge Rescue. Rescuer, instructor, guide, author, designer, and adventurer.

Why is a sling 2x the strength of a single strand?

Why is a sling 2x the strength of a single strand? single strand vs sling

What’s in this post? This post is about the theory and testing behind why making a piece of webbing into a sling is 2x the strength of a single strand. We address the specific question about tension on a single section of sling around a carabiner at the end and draw vectors to show what […]

Lightweight Jigger Testing

Lightweight Jigger Testing Lightweight Jigger Complete

What’s in this post? Testing of a lighter weight jigger (4:1CD/5:1 pre-rigged pulley system) using a 5mm Prusik and a 6mm high strength cord made with a Dyneema core with a polyester sheath. We also address the weight and volume of a jigger to compare the lighter weight version with a standard version using a 6mm Prusik […]

Webbing anchors: efficient rigging and 16mm testing

Webbing anchors: efficient rigging and 16mm testing webbing anchor header

What’s in this post? The basics for webbing anchors: So you know why you are using webbing anchors, what to use, set up and four ways of rigging. How to rig webbing anchors efficiently: Get the right (minimum) webbing length, rather than halfway through a rigging job finding out you are short and have to start […]

Testing the Figure-8 Device Block for Canyoning

Testing the Figure-8 Device Block for Canyoning

What’s in this post? Slow Pull testing the figure-8 device block variations with normal loading and incorrect loading. We also compare this to baseline methods such as the Munter mule overhand and figure-8 on a bight. Efficiency tests (speed) to find out if there is there any major differences in tying methods. Practical use comparisons […]

Back-tie rigging – tension and compression forces

Back-tie rigging – tension and compression forces RRRFG pg 65 backtie rigging

Back-tie rigging – tension and compression forces The other day I had a question come through about how I worked out the tension and compression forces for a post, pole or tree when you back-tie for support.  The context? Before I get to the question, we need to set the context:  The front anchor is […]

Double sheet bend; but it’s fine?

Double sheet bend; but it’s fine? Double sheet bend yosemite 10mm

Introduction I was recently undertaking testing to confirm our cave rescue setup (see the post Let’s lighten the load – update). In cave rescue, as we use the double sheet bend for rigging – being easy to adjust, especially in the middle of a rope or cord – I thought it would be a good idea to […]

Let’s lighten the load – update

Let’s lighten the load – update Two Rope Drop Testing 2

Let’s lighten the load – Update. After a particularly arduous 24hrs underground and 1000m of hauling on a deep cave SAREX (Search And Rescue EXercise), we started our journey towards asking the right questions about rope rescue. Could we lighten up our backcountry rope rescue gear while keeping acceptable safety margins? For lightweight rope rescue, […]

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