Grant Prattley

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

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 the suitability of 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 – as it’s easy to adjust, especially in the middle of a rope or cord – I thought it would be […]

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, […]

Floating anchors: But what if the anchor blows?

Floating anchors: But what if the anchor blows? 2 point floating anchor carabiner pulleys

Introduction Floating anchor: but what if the anchor blows? Isn’t it going to rip the other anchor out? I hear this as a common statement quoted back to me when talking about a two-point floating anchor (aka self-equalising, magic X, etc.). I can only think it’s based on the assumption you have: Built or chosen […]

Which bends for joining ropes? – Update

Which bends for joining ropes? – Update double overhand flat bend in use

Introduction As part of writing the Canyoning Technical Manual, I needed to find out more about flat bends. For my own peace of mind, I had to make sure what I was putting in the book was suitable. We undertook some testing in 2015 including a control test and five flat (offset) bend variations.  In 2020, […]

How much friction for your device?

How much friction for your device? Friction Testing

How much friction for your device? We were interested to know (as a guide) how much a lowering device can hold for rescue in particular but also personal use. The testing is for practical use when out on a rescue, training or instructing a group about how much it can hold in relation to: the […]

Life on the edge: testing the edge kit

Life on the edge: testing the edge kit Edge Kit 4on2 Drop Test Factor 1

Introduction We have used an edge kit for several years. Over this time, I have never done any testing on the combination of Purcell Prusik (Prusik on a Prusik), Prusik hitch 6mm on 8mm cord and double overhand (scaffold) hitch onto a carabiner. There has also been an assumption made that the edge kit would […]

Forces on an inclined plane and Tippy the tip truck

Forces on an inclined plane and Tippy the tip truck

Forces on an inclined plane and Tippy the tip truck How do you figure out the forces is a common question I get when teaching a particular subject. None more so than those on an inclined plane (or slope). Rather than getting onto the whiteboard to explain, from time to time, I bring out Tippy the […]

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