In my last post I talked about the Sterling Evolution rope and some characteristics that made me name this my favorite rope so far. In this post, I have put together a chart of ropes with their characteristics that show how this rope compares to similar ropes from other brands. How do you know what the characteristics mean and what should you take into consideration when purchasing a new rope?
Here is a chart showing the comparison, stacked by least weight(g)/m but not stack ranked. The rope at the top is the least weight(g)/m but does not mean it is the best rope. To understand what is the best rope for you and your use, you need to answer some questions below and understand a little more about ropes and your particular use.
First, let’s start by dissecting this chart.
- Brand: This is the company and name of the rope being used for comparison.
- Diameter mm: This is the diameter of the ropes being used for comparison.
- UIAA falls: This is a measurement standardized by the UIAA that has been developed to understand the forces that when applied to a rope could make it fail. What is the acceptable load and how do the measure it? Check out their site. This number is related to the impact force measurement, also in this table. All ropes must adhere to these tests and note their results in their specifications. Never buy a rope that is not UIAA certified. The minimum acceptable fall rating has been determined to be 5. To learn more about how they measure and determine this, see this site. Higher fall ratings means longer lifespan of the rope. To learn more about fall factors that explain why that last statement makes sense, go to this site or watch a slightly comical but very informative video that explains this.
- Weight g/m: This is the weight of the rope broken down into grams/meter.
- Dynamic and static elongation: Just like the name implies but the test is intended to simulate the amount of elongation a climber would experience when lead falling onto the rope vs. when sitting on a rope (static load). The lower the percentage, the least give in the rope. A static rope may have a small percentage of elongation something like 5%. If you saw this number, you would know that the rope would have very little elongation and might be perfect for ascending and other rigging applications, but it would be too stiff to climb on. If a climber were to take a lead fall on this type of rope, not only would the catch be incredibly stiff but it could cause serious harm to the climber.
- Impact force kN: This is the force you feel when you are falling onto the rope. The lower the impact force means the rope is absorbing most of the impact and the cushier your fall might feel. Higher impact forces means more transfer of the force onto the climber. However, high impact forces does not mean a bad rope. There are instances where you might want slightly higher impact forces. For example, to achieve the soft catch from the rope, the rope has to have some elongation/stretch to it. Too much and you fall too far. Ground falls or top roping are two situations to consider when thinking about how much stretch you want your rope to have. Note, impact force, in part, relates to the durability of a rope and this has to do with the construction of the rope, see below.
I’ve omitted cost in this chart to try to focus on the structural elements to consider. The other piece missing from this chart and the part that is not easily measured is the ‘secret sauce’ of ropes. This is the most interesting aspect to rope construction and what largely differentiates ropes from various companies. The core of a rope is largely made the same way from company to company, but how they ‘put it all together’ is what you want to consider. The following is an excerpt from the site, Alpine Exposures, that does a really good job of describing this
“Mike Kann was kind enough to explain this further (and this is the really important bit):
The impact force is a measure of how much energy is absorbed by the rope. As energy absorbtion occurs over a time period (even if its nanoseconds), you can reduce the force transmitted to the rope by lengthening the period over which the energy of the fall is absorbed. This is the same theory as used in crumple zones. The fact that you lengthen the absorbtion period means that impact force on the piece of protection is reduced, making the piece less likely to fail. Seems like a win win situation until you come to actually build the rope.
So you’ve got your twisted core. Easy. The problem is that you then need to hold the cores together with the sheath. The sheath needs to elongate by the same amount that the core elongated otherwise the cores will not be able to fully extend. So you need to weave the sheath to cope with this – which is where the problem lies. The easiest way to do this is to make it looser. The problem with making it looser is that you increase the core/sheath slippage and you end up with floppy bits on the end when you abseil on the rope. Secondly it means that it gets abraded more quickly. Making the sheath fibres more slippery helps (which is how Mammut have made the Serenity so small – new Teflon coating) so dry treatment helps. However you will always end up with a rope which does not last as long, even if you manage to find a weave that prevents excessive core slippage.”
Now that you are armed with what it takes to make a rope and what the specifications of a rope mean to you, which rope is right? Here’s a place to start.
Answer the following questions:
- What is the purpose of the rope?
- What is your weight? (convert to kg then derive your hanging impact force (your weight (kg) * 9.8 (gravity))
- 50kg*9.8=~500 newtons (divided by 1000 kN) yeilds 0.5kN
- Who will climb on this rope? are they about the same weight as yourself?
- Will you primarily be projecting on this rope, anticipating many falls over time and want something durable that has a long lifespan?
- Will this be your primary redpoint rope–something you will use only for those climbs where weight, length, and impact force really matter? Does durability matter? Will you take less weight and more comfort from a rope and sacrifice longevity?
- What kind of terrain will the rope be subjected? Ice, rock, combination? Does the construction of the rope need to take this into account?
Let’s look at a scenario:
A youth climber is buying their first lead rope for sport climbing. The youth weighs 40kg, making her hanging impact force 40*9.8=~400 N or 0.4kN. She’s the only one climbing on this rope, or other youth her weight, and will be her primary project rope. She’s half the weight of the test weight used for determining the UIAA fall rating, therefore her fall rating can be doubled for that rope. She needs a low impact force rope to absorb much of the fall force since she will likely be belayed by people who are heavier than she. The combination of a dynamic belay by the belayer and the low impact force will make for an overall soft catch. She will want low elongation rating to aid the belayer in taking in slack since her weight won’t apply enough force to take all of the stretch out of the rope.
- In summary she needs:
- A light rope (low g/m)
- low impact force
- low static elongation percentage
Based on the chart the first rope the Mammut Serenity wouldn’t qualify because it has too high of static elongation percentage. The second and third ropes listed would be solid contenders. Because of her weight, a rope with UIAA fall rating of 5 would be more durable and have a longer lifespan than someone twice her size.
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