One of the continuing topics I see come up in climbing classes is the use of personal anchors: should you use them, what you should use, what is common practice. This is an age-old debate which I cannot do justice describing in a blog post. There are entire books and papers written on each topic, and depending on how deep you want to go, you can spend all your days buried in scientific data.
Most of us just want to know how to be safe and get outside! So, let’s discuss some areas which are interesting to consider when looking at these safety systems. From here, you can start to think critically about the different options and dig deeper as you wish.
What are personal anchors?
Wikipedia describes an anchor as:
[…] any way of attaching the climber, the rope, or a load to rock, ice, steep dirt, or a building by either permanent or temporary means. The goal of an anchor depends on the type of climbing under consideration but usually consists of stopping a fall, or holding a static load.
All anchors have multiple uses. A common use for personal anchors is at belay stations to prevent yourself from falling from your belay stance, and/or allow yourself to hang off the anchor. Before we go into the various options you have available, let’s first look a little more at what you’re protecting against: falling. There are two main things to think about:
- Fall factor is a derived number used to evaluate shock loads generated on the climber, belayer and anchors that occur when a climber falls. The higher the fall factor, the greater the forces placed on the components of the system. SouthwestClimbing.com has a great write up which dives into more detail. You can also reference wikipedia or do searches online.
- Dynamic force is created when falling onto your protective pieces. This is usually measured in kilonewtons (or kN). Materials used in climbing are limited by various properties such as material strength. Essentially, you want to minimize dynamic force to avoid reaching the limitations of the components in your climbing system.
Now that we understand that we are protecting against the dynamic forces when taking a fall, we can more closely look at the materials available to protect that fall. I could go into all materials such as trad gear, bolts or biners, but since we’re talking specifically about personal anchors, let’s focus on the meat of the debate — the soft goods: slings, cords, webbing, rope.
As mentioned above, materials have various properties such as strength, weight, elongation, moisture effects, degradation, abrasion resistance, melting point, and chemical resistance. As such, materials will have pros and cons for their application in various situations. The key to making decisions on which material or method is best for you, is to start understanding these properties and making informed decisions. Most solutions you decide on will have a downside. Looking at the options, you can evaluate if the tradeoffs are an acceptable risk for you.
The below table outlines typical property values for materials used in ropes, slings, and cord (see also: rope). For the purposes of this discussion, we will be focusing on nylon and HMPE (aka spectra or dyneema). If you don’t know what your materials are made of, some research with the manufacturers or the web can help. To generalize, webbing and cord are made from nylon (though not always). Spectra and Dyneema materials are HMPE.
CORDAGE FIBER PROPERTIES — TYPICAL VALUES Cordage Institute
|Breaking Tenacity — dry (grams/denier)||7.8–10.4||7.0–9.5||6.5||6||30/35|
|Wet Strength vs. Dry Strength||85–90%||100%||100%||105%||100%|
|Shock-load Absorption Ability||Excellent||Very Good||Very Good||Fair||Fair|
|Percent at Break||15–28%||12–15%||18–22%||20–24%||2.7–3.5|
|Creep (extension under sustained load)||Moderate||Low||High||High||Moderate|
|Water Absorp. of Individual Fibers||2–8%||<1.0%||None||None||None|
|Resistance to Rot, mildew & deterioration due to marine organisms||Excellent||Excellent||Excellent||Excellent||Excellent|
|Resistance to UV in sunlight||Good||Best||Fair||Fair||Fair|
|Resistance to aging for properly stored rope||Excellent||Best||Black is best Excellent||Black is best Excellent||Excellent|
|Surface||Very Good||Excellent||Good||Fair||Very Good|
|High Temp. working limit||250°||275°||200°||150°||150°|
|Low Temp. Work limit||–70°||–100°||–20°||–100°||–200°|
|Effect of Acids||Decomposed by strong mineral acids;resistant to weak acids||Resistant to most mineral acids;disintegrate by 95% sulphuric acid||Very
|Resistant to most weak acids.Strong acids will attack; especially at high concentrations or high gemps||Very
|Effect of Alkalis||Little or none||No effect cold;slowly disintegrate by strong alkalis at the boil point||Very
|Resistant to most weak alkalis.Strong alkalis will attack; especially at high concentrations or high temps||Very
Data! Now we’re starting to get somewhere. Let’s start looking at how these materials perform under testing.
There are several common tests for materials, but the two I’ll mention here are:
- slow-pull tests: under what load will the material will fail when pulled at a steady rate (static load)
- drop tests: under what load will the material fail during a dynamic fall (dynanmic load)
A good place to start is Tom Moyer’s Comparative Testing of High Strength Cord. A few things to draw out about various testing I’ve seen:
- Nylon is a heavier material, but has excellent shock-load ability. This is mostly due to it’s elongation properties, which acts as a shock absorber as it stretches. It will absorb water and you will see slight performance degradation when wet.. It has a higher melting point, which helps it resist breaking during dynamic falls where heat disapation can occur with friction.
- Spectra has excellent weight to strength ratio. It’s elongation properties are low, which limits it’s ability to handle shock-loads. It does not absorb water and there are no performance effects when wet. It has a lower melting point which makes it more prone to breaking when friction/heat is involved.
- Knots will reduce the material strength depending on the matierial and the knot. TMoyer’s paper shows that spectra will lose 40%-50% of it’s strength when knotted with a figure-8 and nylon 10% or so. The Freedom of the Hills also lists breaking strength of knots in a kernmantle rope (see index under “knots”) in the realm of 15–30%.
One thing to think about when looking at test results is how the material was tested and how it applies to your use. For example a lot of anchor testing involves the use of a rope, which will help absorb dynamic forces. Also, the slippage in the system from other protection, belay devices, and the acts of a belayer/climber, will help dissipate energy and reduce the direct force on the anchor. In the case of a personal anchor system, you are directly connected to the anchor and therefore a fall’s force is applied most directly on the material used to anchor (not to mention your body).
Common Personal Anchors
With that primer, let’s start looking at personal anchoring methods. Common methods:
- Daisy Chains. Recently Black Diamond posted a blog entry regarding use of their daisy chains for personal anchor devices. Daisy chains are a single loop of webbing material which is tacked into small loops. Intended for aid climbing, this gear is built toward static loads. In a fall, you are relying on the strength of the bar tacks, which are not rated to take a dynamic fall.
- Personal Anchor System (PAS). A product developed by Metolious to address the need for use in a dynamic environment. It contains individual loops which are bar tacked separately. Since each loop is it’s own sling, it performs well under slow-pull static tests because each loop is full strength. What about dynamic load? The PAS product is a hybrid of spectra and nylon. We already know that spectra material strength is significantly impacted in a dynamic fall. In drop tests done by Mike Gibbs @ Rigging for Rescue, fall factors of 1.25 or higher will create a complete failure of the system. His conclusions:
The introduction of high performance fibers into climbing and rope rescue equipment has some worthwhile applications. However, the use of HMPE like Spectra ® or Dyneema ® in the construction of daisy chains is simply a bad idea. The properties of HMPE include the benefits of high strength, the ability to float and excellent resistance to chemicals and U.V degradation.However, HMPE properties also include very low elongation at break and a low melting point.It is these last two properties that are likely the key contributing factors to:
(1) the high peak force values observed in our testing of lanyards constructed out of these materials.
(2) the breaking of these same lanyard types on certain drops
- Slings or Nylon Daisy. I’ve seen slings used by girth hitching them to the harness and then tying knots into them. This simulates the loop system similar to a daisy chain or PAS, but avoids bar tacking by use of knots. It also allows you to choose material. Based on information provided already discussed, use of a spectra sling would not be advisible in a fall. What about nylon? Drop tests by Mike Gibbs shows that Nylon Daisys (such as Climb High 25mm) can catch a factor 2 fall with no signfificant visible damage. Also worth a look is DMM’s dyneema and nylon drop tests (video), which looks at both sling material and knots in drop tests.
- Purcell Prusiks. In the rescue world, the use of purcell prusiks have been introduced as an alternative for personal anchoring. I have not seen this in much practice except from people who have watched Rigging For Rescue drop test videos (which are quite an eye opener!) and are familiar with these studies. In 2006, Mike Gibbs furthered this study in another set of drop tests. His summary:
The testing conducted on Purcell Prusiks was by no means a comprehensive examination. However, the testing conducted certainly suggests that a Purcell Prusik constructed out of 6mm cord with a 3-wrap prusik hitch meets the recommended lanyard performance guidelines of being able to withstand a fall factor 1 event with acceptable levels of MAF and no observable degradation of the lanyard. The testing also demonstrates that the margin over and above that minimum performance criteria is approaching the 50% level at fall factor 1.5.
- Rope. Ropes are probably the best understood material for use in a dynamic fall. After all, lead climbers may take dynamic falls and a rope is a core piece of the system. A dynamic rope is intended to use elongation as a means to absorb the force of a fall. Ropes sold for climbing meet UIAA standards for testing in both a static load and dynamic fall scenario. Different ropes have different fall ratings, so it’s always best to educate yourself on how the ropes were tested and the UIAA rating. It’s also best to understand the history of the rope and it’s current condition. To use a rope as a personal anchor, the climber attachs their rope to the anchor. A common method is the clove hitch.
Some final points of consideration as you start aborbing the information out there:
- Test data is not incredibly abundant for material use in climbing, but you can find information by searching the web. Search results will improve as you start understanding the langugage of materials, and understanding which organizations typically publish this sort of information. Understanding the industry will help you tap organizations who have done testing, but don’t post results online. They will often send you the results if you ask, or will charge a small fee. Look for non-biased sources such as UIAA.org, American Alpine Journal, or International Tech Rescue Symposium. Manufacturers are also good sources, but be aware of marketing. Read and participate in debates climbers are having on active forums such as supertopo.com or cascadeclimbers.
- What’s is common practice may not necessarily be based on the “safest” method. Since climbing is very much an apprenticeship, often these methods are passed down from climber to climber because that is how they were taught. Learning from multiple people and multiple sources is useful. Triangulate!
- Manufacturers may report material strength only as a function of slow-pull tests, not drop tests or other test methods. For dynamic situations, make sure to research both and understand how products are rated.
- Material’s have multiple properties which will impact it’s performance in various situations. You must look at the specific situation to better understand the material’s performance.
- Materials used in climbing are only as good as their care and use. For example, an anchor built with the best materials has no bearing if it’s in poor rock quality. A soiled rope exposed to garage chemicals, same thing.
Mike’s more recent paper recommended some guidelines for lanyards based on his drop tests. The key takeaways:
- Avoid the use dyneema or spectra for personal anchors. They are known to fail at relatively low forces.
- Choose a material which will absorb energy, such as nylon webbing, cord, or your climbing rope.
- Give yourself a margin of error by choosing a system which will keep functioning after a severe drop. Sewn nylon slings, purcell pursiks, and use of the rope all faired well in drop tests.
- Reduce your fall factor by keeping unnecessary slack out of the system
For most occassions (when multi-pitching), I clove into the anchor with the rope. I choose this method because it’s one less single-use thing I need to carry. I also carry a sewn double-length nylon sling. This runner can exist as part of my rack as a draw or I can throw in a few knots and use it as a personal anchor.
Understanding what you should use as a personal anchor is a process of knowing why you would want one, what materials are available, and how they would perform in your specific situation. Each solution has it’s pros and cons which may vary given different situations. What’s acceptable risk for one climber, may not be for another. The information here is an overview of areas to consider and start researching. It’s not a substitute to professional training, doing your own research, and making your own decisions. I hope you found some useful sources here to start you off!
Thanks for reading!
Disclaimer: Rock climbing is inherently dangerious and potentially deadly. All content should be considered commentary on the subject. Make informed decisions. Climb at your own risk.