Can You Use a Dynamic Rope for Rappelling
When you’re shopping for ropes, you’ll see there are mainly two kinds: static and dynamic. In general, static ropes are made for rappelling, anchors, and hauling. Dynamic ropes are made for climbing. But what if you want to use a dynamic rope for rappelling?
Can you use a dynamic rope for rappelling? Yes. It is absolutely fine to rappel using a dynamic rope. The only major difference between dynamic and static ropes is the rate at which they stretch - though it may be easier to rappel using a static rope due to this lack of stretch, it doesn’t vastly change the safety aspect.
This isn’t to say that a dynamic rope is the only rope you’ll ever need, and static ropes have no use because they are basically redundant. They’re just more specific, and at what they do, they do well. There is a whole world of reasons why I love to have both dynamic and static ropes in my climbing gear arsenal, and consider a static rope essential to what I do.
Best Practices for Choosing a Rappelling Rope
While it’s completely ok to use a dynamic rope for rappelling, I would only really do it out of convenience. For example; say I’m out on a full day, a nice 200 m long multi-pitch climb. I’ll top out after 7 pitches; each pitch is around 30 m long. The way down is the same way we came up; 7 individual rappels back to the ground.
Sure, I could carry a static rope with me, in my backpack, take it to the top and then use it to rappel down. I could, but will I? Absolutely not. When rappelling for a purpose like this - relatively short rappels, each rigged so both strands of my rope are running through my ATC, there is no need for a static rope. On short rappels like these, there won’t be much rope stretch. Even if there is, it’s no big deal.
If I’ve just found an amazing 60 m cliff face I want to rappel down, I’ll absolutely be using my static. When doing a long rappel like this, the rope stretch involved if using a dynamic rope becomes way too much. On the way down, I’ll be bouncing around as the rope stretches - every time I stop or don’t feed the rope through my device perfectly and evenly, I’ll bounce. It just won’t feel all that solid.
Using a static rope in this situation makes a lot more sense because static ropes are made for this. You have a higher level of control in this situation with a static rope. You can feed the rope through your rappel device much more evenly and smoothly.
The same thing goes if you have an emergency and need to rescue a climber and lower them down to safety. You can’t have them bouncing around every time you lower them further. This could increase the chance of further injury. We just have a far greater degree of control using static ropes for these cases.
When to Use a Static or Dynamic Rope
If you’re out for a day of rappelling, hauling gear up a big wall, ascending a rope, or if you want to descend a waterfall or go caving and need a rope that can get wet - get you down into the cave, then ascend back up to the surface again, you’ll be wanting a static rope.
That’s not to say you couldn’t do these things with a dynamic rope - you could. It would just make things many, many times harder. Dynamic ropes are just too stretchy for applications like this. I’ll get to why dynamic ropes are too stretchy in a moment.
These activities I’ve just mentioned; I can be pretty certain none of them will put too much dynamic force onto the rope. When I speak of dynamic force, I mean when an object is in motion (a climber taking fall, for example), and the rope is ‘catching’ the fall of the climber.
This differs from static force - static force being when the rope is just taking weight statically. If there will be no dynamic force, then you don’t really need, nor do you want the rope to stretch.
For most climbing applications, be it lead climbing, ice climbing or top rope climbing, we need this stretch. We want this stretch. Stretch is GOOD! The stretch factor of a dynamic rope is what can be the difference between a nice soft catch, and a harsh abrupt one. That stretch - that absorption of energy by the rope can lessen the load on our other gear: bolts, quickdraws, harnesses, and anchors.
When a climber falls, a dynamic rope will not only catch the climber, it will give him or her a softer catch due to the rope stretching as the energy is absorbed. The energy of the fall is transferred into the rope. Think about a dynamic rope as a slinky or spring, and a static rope as a metal chain.
If we were to use a static rope to lead climb, taking a big fall could potentially be fatal. With little to no rope stretch, we’ll have a very static catch, and with nowhere for the energy produced by the falling climber to go; a little will go into the rope, but most of it will go into the climber. A fall like this will not feel good and can result in serious injury or worse to the climber if the force produced by the fall is large enough.
Static ropes are also not designed, nor tested for the forces incurred by a dynamic fall.
Dynamic vs Static Rope - How Much Do They Stretch?
If the main difference between dynamic and static ropes is how much they stretch, then how different can they really be? The answer to that is very, very different!
See, a dynamic rope will stretch at a rate of somewhere around 10%, depending on the manufacturer. A static rope, on the other hand, will stretch very little, at somewhere around 1%. To put this into perspective, let’s do a small thought experiment.
Let’s take one end of a dynamic rope and attach it to the top of a cliff. Say we’re using a Beal Joker, 70 m dynamic rope. This particular rope has a static stretch percentage of 8%.
Static stretch means the amount the rope will stretch if we hang an 80 kg weight on the end of it. So, we’ve got one end attached to the top of a cliff, and to the other end, we’ll attach our 80 kg weight. When we do this, the weight will cause the rope to stretch an additional 5.6 m!
If we run the same test with a static rope, the rope will only lengthen around 70 cm or less.
Now if you think about it, imagine you need to ascent this 70 m rope. You’ll use your GriGri and an ascender (or two ascenders) - whatever your setup may be. You’ll be pulling 5.6m of stretch out of the rope before you even leave the ground. Just like pulling a string of elastic until it goes tight.
This is where a static rope is a thing of beauty! With the first arms-length of rope you pull up on, you’ll be off the ground!
If you ever see a photographer, someone like Jimmy Chin while filming Free Solo, he’ll be using static ropes to ascend to where Alex is. When Jimmy stops moving to take that outrageous photograph of Honnold, free soloing, heel-toe camming 800 m off the valley floor - he needs to be fast and needs to be completely still when he arrives. That wouldn’t go so well with a dynamic rope, and for this purpose, you would never go dynamic.
What size rope is best for rappelling?
Ropes come in a wide variety of lengths and diameters. They can vary from 9 mm in diameter, up to 13 mm. They generally come in lengths of between 40 and 200 m.
To figure out what length you need, look at the length of the longest rappels you want to descend, then choose your rope length based upon that. For diameter, the thicker the rope, the more durable it will be, but also the heavier it will be.
Keep in mind thinner ropes move faster through rappel and belay devices. Check the belay and rappel device manufacturers recommended rope diameter to ensure the rope you want to use is compatible with the device you have.
How can I tell if a rope is dynamic or static?
A new rope will include a small tag heat shrunk onto one end of the rope, with information such as: manufacturer, length, diameter, and whether the rope is static, dynamic or twin.
If this tag is no longer present, the color may provide some information. Static ropes are usually a single color, either black or white, sometimes a combination of the two.
Another way to tell would be to take a 20 m length of rope, attach one end to a cliff, and clip yourself to the other. If it stretches, it’s dynamic—if it doesn’t, it’s static.
How long do climbing ropes last?
Climbing ropes should be regularly inspected and should be retired if any damage is shown. This includes flat spots in the rope or too much fuzziness on the sheath.
The lifetime of a climbing rope also depends on the amount of use it receives. A climbing rope used a few times a week should be retired after around a year, whereas a rope that gets used a few times a month will last around 3 years.