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Category: Skills
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Lanyards
Lanyards
On the implications of being attached to planet Earth.
Call them what you will:
- Tether
- Cowstail, cowtails, cowtail
- PAS (personal anchor system)
- QAS (quick attachment safety)
Fancy acronyms don’t imply intentional design.
Gravity of the Situation
A fall on your tether is one of the worst case scenarios for your SRT gear. Being above your anchor by any amount has severe consequences. Even a large lead fall has more rope to dissipate energy through.
Even though cowstails are short, the choice of dynamic rope is very significant in their ability to absorb energy in unplanned falls. ~Richard Delaney
“Are we all agreed on the purpose of the tether?” ~Blake Douglas
Tether Motivation
You’re always one decision away from living a completely different life. Clipping may not bring you comfort. But if you hang out at anchor stations enough, you will eventually see a tether work. Here’s some solid reasons to clip yourself to solid ground:
- Feel more comfortable
- Make your friends comfortable
The Perfect Cowstail
Instant Gratification Recipe
Ingredients
- 11mm dynamic rope
- Carabiner for short cowstail
- Carabiner for long cowstail
- Rope cutting tools
Figure-8: The bight should only be large enough to barely slip onto your d-link.
Poachers Knots: Set at each end, so they stay secure and tend to hold the carabiners in place. Set the knot by tensioning load and tail strands.
Short Length: Exactly 45cm (Maybe? todo) from the inside of the loop to the inside of the carabiner. This will lengthen after a few uses, and also shrink after a few wet-dry cycles. This length is explained in the diagram below (todo).
Short Carabiner: Lightweight, strong, perfect for clipping a hanger. perhaps locking, this is explained below(todo).
Long Length: Perfectly tuned to your body, so you can just barely reach the top of your chosen ascender. This will lengthen after a few uses, and also shrink after a few wet-dry cycles.
Long carabiner: Ovals give you more options for ascending devices and tend to perform better outside of a laboratory.
Tail lengths: At least 7cm (todo).Locking Carabiner?
The book “Risk: A User’s Guide” describes a double-bind faced by officers designing training programs for the Armed Forces.
Realistic training scenarios where soldiers are more likely to be hurt, even killed, deliver better field outcomes and potentially save more lives in battle. However, training staff are often discouraged from designing realistic trainings to avoid harming soldiers and disciplinary repercussions themselves.
Should students be trained with higher realism and higher repercussions?
In the US, the National Cave Rescue Commission requires locking carabiners in training which likely increases safety in chaotic training scenarios. In Hungary however, cave rescuers believe it’s more realistic to have a non-locking carabiner on their short cowstail. Hungarian cavers train with this choice in mind exercising more care when necessary. Form your own opinions, they may look like:
• American rescuers are hedging to make up for a lack of basic skills or infrequent exposure to rebelays. The extra locking mechanism is a crutch and may even paradoxically decrease safety.
• Normalization of deviance has resulted in the Hungarian rescuers choosing a less safe technique because that’s how they’ve always done it.
Best of both worlds? Pictured is a locking carabiner that can be easily clipped or unclipped. Everything has drawbacks, this carabiner is heavy, expensive, and potentially too large to clip old hangers. Many varieties of easily manipulated carabiners exist. Dual-action auto-lockers are another example. Why dynamic rope?
Dynamic rope blah blah
Hooked Noses
The notch gets caught on stuff. Hooked nose carabiners are old fashion. You might decide you want this feature, but in general we have moved away from this old design.
Short Cowstail:
How do we arrive at real numbers?
The situation is that you’re ascending a rope and need to cross a rebelay. Your toothed-ascenders stack up on the rope below the bolt.
The Depth of Human Knowledge
Elongation reduces forces
This screenshot from a RopeTestLab article (paywall) shows approximate cowstail elongation figures. The author uses 6kn because of EN standards. however from reading the document to the right, we also know 6kn is about what you will experience in a fall-factor 1 fall with dynamic rope.
So the knots tighten AND the rope stretches. Lengthen good.
1m stretches 585mm = 23in (todo)
French Cowstail testing
A massive set of tests performed on caving cowstails
TL:DR
- The recipe above performed best.
- Pre-tightening knots is fine
Spelegyca is more hazardous than most:
An image from the Petzl Spelegyca manual. The spelegyca complies with EU 2016/425 which implies a 6kn maximum arrest. However Petzl doesn’t mention or illustrate the required “screamer” for compliance. Purcell Prussiks and Daisy Chains
TL:DR
- Purcell prussiks are dangerous and unpredictable
- Daisy chains are dangerous
Standards & Procedures
Armed Forces
Canada
Japan
Anti-Patterns
The amount of energy needed to refute bullshit is an order of magnitude bigger than that needed to produce it.” ~Alberto Brandolini, Bullshit Asymmetry Principle
Notes:
Paul says:
Here is the lanyard that I use: https://www.petzl.com/NL/en/Professional/Lanyards-and-energy-absorbers/JANE-Y
Petzl states this fot the JANE-Y: “Dynamic rope lanyard to limit the impact transmitted to the user in the event of a short fall (1)”
Daisy Chains