Adjustable Lanyard

[rcwild]

Here’s another use for your VT Prusik. Add a sewn 6mm x 11 inch prusik to make an adjustable lanyard. The VT is about the right length for most people to use as an ascending lanyard. The prusik will allow for fine adjustments. Can also be used as an “easy daisy” for hooking out of potholes.

I’m talking to BlueWater about making some 5-foot pieces for me. Eye sewn on each end. Plan is to create a 2-legged cowstail, similar to a Petzl Spelegyca, with a prusik on the long leg for adjustment.

[rcwild]

I love working with BlueWater. Sent in my request for the 5-foot pieces. Pointed to a couple different cords they make that would work nicely, but added that if they have excess inventory that they want to find a use for, I'm open to ideas.

Received a UPS tracking notice that 36.5 pounds of "scrap rope" is on its way.

[DJ Meding]

Cavers use this type of sling for their QAS (Quick attach safety). The ones I have seen and made have bulky figure 8 knots on both ends with a piece of webbing protecting the loop. The sewn aspect would be favorable over the knot as long as you are not sacrificing strength. Could the piece of tubular webbing be added to the loops?

[rcwild]

Originally Posted by DJ Meding

Cavers use this type of sling for their QAS (Quick attach safety). The ones I have seen and made have bulky figure 8 knots on both ends with a piece of webbing protecting the loop. The sewn aspect would be favorable over the knot as long as you are not sacrificing strength. Could the piece of tubular webbing be added to the loops?

One of the French canyoners in Nepal was using an industrial lanyard about a meter long with a Petzl Basic ascender for adjustment. I liked the range he had, but it was bulky.

The current inspiration came from a lanyard Spidey uses. It's all tied and the knots are a little bulky. I tied a 2-legged version just to see if it would work. It did, but again, knots were too bulky.

BlueWater dips the eyes and stitching in urethane to add durability.

[Spidey]

SWEET! I got first Dibs. Although inspired by my lanyard this one is a vast improvement. Once people see it everyone will want one. It's like a spelygeca only way better.

[rcwild]

Originally Posted by Spidey

SWEET! I got first Dibs. Although inspired by my lanyard this one is a vast improvement. Once people see it everyone will want one. It's like a spelygeca only way better.

Steve, can you provide a link to the Australian rock climbing web site where you found the instructions for your lanyard?

[sonnylawrence]

Originally Posted by rcwild

I’m talking to BlueWater about making some 5-foot pieces for me. Eye sewn on each end. Plan is to create a 2-legged cowstail, similar to a Petzl Spelegyca, with a prusik on the long leg for adjustment.

This is an interesting idea. Rich's system is made up of a prusik and VTprusik. Some possible short comings are:
1) The best tether should be able to absorb energy with a fall. I am guessing the VTprusik by itself does not. So the slip of the prusik attachment becomes critical.
2) I suppose one has to decide what is the maximum arrest force the human body can take. OSHA/ANSI says 8 kN. CE 6 kN. UIAA 12 kN. Canada 8 Kn. One way to break the tie is to average out the values to a tad over 8 kN. Intuitively I believe my body would only like to experience about 6 kN. A tandem triple wrap prusik made of 8 mm nylon working on 11 mm nylon will slip at about 7 to 9 kN. A Purcell prusik made of smaller diameter (5 or 6 mm) nylon cord will slip at a lower amount. I don't have actual values to quote.

So for Rich's system, it needs to be tested to see what forces would be transmitted to the canyoneer.
a) If the prusik slips at too low a value, say 1 kN, all the force goes onto the VTprusik and then the canyoneer. Not good!
b) If the prusik does not slip until something greater than 9 kN, all the force goes onto the canyoneer first. Not good!

The tandem triple wrap prusik mentioned above possibly works by converting the force of the fall into heat which melts the nylon on nylon interface. The advantage (as a Valdotain tresse used on dry rope) of the VTprusik is that Technora melts at over 900 degrees F. That may translate into a disadvantage for this tether system.

So, it looks to be an interesting idea. It can be easily disassembled, hence it could be used in parts for an emergency.

[sonnylawrence]

On a related note to this thread: http://www.dmmclimbing.com/video.asp?id=5

An avid caver friend had worn out a Petzl Spelegyca, so he thought. There were a few stitches broken and abraded fuzzy areas. He was not comfortable using it as a tether. So Paul Stovall and I set up a dynamic testing device in a lab. We used a 100 pound weight raised about 5-ish feet above the anchor and dropped it suddenly. It took many drops to significantly damage the tether. Each time we dropped, it unzipped a little bit. The Spelegyca slowly unraveled. I walked away impressed with the device. I use one for caving now. I don't recall what the impact forces were. I will have to check.

[DJ Meding]

Here are some photos of the one that I made.

[rcwild]

The other option would be for people to understand the pros and cons of all lanyards and use them accordingly.

The Rigging for Rescue tests put the fear of God into people about using Dyneema lanyards. That's a good thing insofar as it informed people about the risks. Many people opted to stop using Dyneema lanyards altogether. The tests certainly contributed to the increased popularity of Purcell Prusiks. It's all good.

However, for those who understand the issue there's nothing wrong with using a more static lanyard and taking care not to set yourself up for a severe fall factor.

I'm not bringing this up to defend the use of the VT Prusik in this application. We used it only because it was handy. Ideally, the 2-legged version will be made with pieces of dynamic rope, perhaps pieces of a stock half-rope in the 8mm range.