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Learning the Ropes!

With the vast array of ropes available on the market today, buying a climbing rope can be confusing.  Rope prices can vary greatly and so you may wonder why you should bother purchasing a more expensive rope over one costing much less. As with anything, less expensive ropes are that way because less effort was put into their construction and design. Initially, less expensive ropes seem to be the most cost effective purchase but, it is most likely that more expensive ropes will have the best balance of all rope characteristics, will last longer and will perform better over the life span of the rope.

Ropes available in climbing shops fall basically into 2 categories: Static and Dynamic.

 

Static Ropes

Static ropes (i.e. non-stretch ropes) are commonly coloured black or white and are used most effectively for abseiling, industrial rope access work and, in the UK, are commonly used for top-roping on Southern Sandstone, where their increased durability is a valuable factor when the rope is constantly faced with heavy use in a sandy and gritty environment.  If you do a lot of sea-cliff climbing it is worth investing in a good length of static rope for your abseils.  That way you will be able to leave a rope in place at the top of the cliff to use if you need to escape the base of the cliff but can’t climb out.

 

Dynamic Ropes

Ropes for climbing are called Dynamic ropes and are designed in such a way that they stretch and absorb energy when a climber falls. This energy absorbing stretch reduces the amount of force on the climber, belayer and protection during a fall.  If a static rope was used to lead a climb and the climber fell, even for a very short distance, the impact forces on gear may be higher than the rated breaking strength of all links in the chain. Such forces may also result in whiplash injuries to the climber!  For the purposes of this article I will focus exclusively on dynamic ropes.

All dynamic mountaineering ropes are constructed from a large number of very thin braided & woven threads of nylon and have a kernmantel construction; a twisted or a braided core (kern) inside a woven sheath (mantel).  Before the rope is constructed, the nylon is heat treated to change the molecular balance of the nylon; a process which controls shrinking and enhances suppleness and elongation properties. The most important part of any climbing rope is the kern, which may absorb up to 80% of the force in a fall – that force is called impact force. The kern is made by first twisting the thin nylon threads into yarn bundles.  The twisting of the yarn bundles affects the handling and “knotability” of the rope.  Braided cores are reported to have lower impact forces when subjected to repeated falls over a short time span, like when working a route during sport or gym climbing. They are also reported to be less susceptible to kinking.

The mantel protects the kern and, depending on the nature of construction of the rope, may have more or less effect on the rope’s rated impact force.  The mantle is twisted in a way to align the load bearing direction of the nylon with its longitudinal axis, which offers the greatest strength and abrasion properties. The mantle is woven with either a double-pic or single-pic sheath.  Double-pic sheaths have a loose weave, producing a softer feel and handling but offer more abrasion resistance due to the increased nylon in the weave.  Single-pic sheaths have a tighter weave and are found in smaller diameter ropes to decrease weight.  They normally have a stiffer handling quality but due to the lack of nylon offer less abrasion resistance. Single-pic sheaths are also more waterproof due to the tighter weave of the sheath, which allows less water inside. The draw back to single-pic sheaths is that they are more prone to kinking. Sheaths are woven using 48, 40 or 32 bobbins into a 2-ply sheath. The higher the number of bobbins, the more individual threads there are in the sheath but ropes woven with lower bobbins have a thicker sheath which makes it harder wearing. Some manufactures twist their ropes with a 3-ply sheath with a higher twist rate to increase abrasion resistance.  While this will add a gram or two per meter to the rope's weight, their long term durability far out weighs the extra weight.  A thicker sheath can be more economical over the life span of the rope since most ropes are retired when the sheath wears through or is damaged (when the core becomes visible). As a general rule, larger diameter ropes will last longer, double-pic sheaths will wear longer and single-pic sheaths will have better handling and waterproofing.

Before we begin to think about the comparative benefits of different ropes though, we need to understand how their characteristics are measured…

 

Fall Factor

Fall factor is determined by dividing the length of a fall by the length of rope in use to absorb that fall.  So, if you have climbed 10m from your belay you should have 10m of rope in use. Now if you are 2m above your last piece of protection and fall, you will fall 4m, which translates into a fall factor of 0.4 (4 divided by 10).  But, if you have climbed 3m from your belay and take the same 2m fall, now it is a 1.33 factor fall (4 divided by 3).  While that is not that hard to understand, things that many climbers overlook can change this simple concept.  Very few if any climbs allow the rope to run perfectly in a straight line; the rope will have slight bends in it as it runs through your protection.  Traverses, roofs or wandering routes can greatly shorten the “rope-in-use” length – this is because increased friction at any one or a combination of these points will reduce the amount of rope that is actually going to take the impact of your fall.  All these things can increase the fall factor, perhaps only slightly, but this element of fall factors is often misunderstood.  So, always use the proper length runner or quick draw to ensure your rope runs as straight as possible.  If you feel a lot of rope drag while climbing, recognise the fact that this may place greater impact on your top piece of gear; the rope between you and this top piece of gear, your harness and even you will be subject to a higher factor fall than simply dividing the length of fall by the length of rope between you and the belay.  (The DMM Revolver karabiner is claimed to help with this issue.)

 

Impact Force

The impact force is the single most important feature of any rope. The lower the impact force of the rope the less force is transferred to the climber, runners and belay anchor during a fall.  It is worth noting that the UIAA rated impact force that comes tagged on each rope is measured using a totally static belay on a short section of rope.  However, during actual climbing, a friction device is used to belay a climber that applies friction across the rope system in a dynamic manner to slow down and hold a falling climber. The most commonly used belay device in use today for traditional climbing is the tube style (e.g. ATC).  When using these tube style devices a short amount of rope will almost always slide through the device before the belayer is able to lock it off – this act of letting the rope slip a little may even be done intentionally and is commonly known as ‘dynamic belaying’.  It is likely therefore that when using this type of device a rope will not reach its UIAA rated impact force when subjected to a fall.  However, using a locking belay device such as a Gri-Gri means that the rope is instantaneously locked off to hold a fall and so there may be no reduction in impact force as a result (but see below).  This is why Gri-Gris are not commonly used in traditional climbing where the added benefit of a dynamic belay can sometimes mean the difference between a runner staying in or being ripped out.  That issue is not so much of a concern when sport climbing on solid bolts, which is why the benefits of using a Gri-Gri are mostly favoured by sport climbers.

Another important factor to consider is that the more rope between the leader and the belayer when a fall happens, the more rope there is to absorb the fall, so less force will reach the friction device and less force will be transferred to the protection and the leader.

Actual impact force in a real climbing situation goes even deeper. In a traditional climbing scenario, a dynamic anchor system is used consisting of a tube style belay device, knots and two human bodies. The slippage of rope through the belay device, tightening of knots and the body’s flexing during a fall further reduce the total impact force. So, actual impact force in a real life climbing situation is more dependent on the friction / belay device, how much rope there is between the leader and belayer, the knots and absorption of the human bodies, rather  than simply the actual UIAA rated impact force.  While impact force is the most important feature of rope construction and should be a priority for a purchase decision, just buying a rope with the lowest impact force is not always the wisest option.  (Ropes with very low impact forces may wear and elongate faster due to their construction.)

 

Fall Rating

Fall rating is the second most important feature of a rope. The more test drops a rope can hold generally indicates a stronger rope. During the UIAA drop test (see below), where all the parameters on each test are identical, the rope is drop tested until failure.  So, the more falls the rope holds the stronger it is.  But, ropes with higher fall ratings typically have a higher UIAA rated impact force.

 

UIAA Certification and Testing

The UIAA (the Union Internationale des Associations D’Alpinisme) certifies all dynamic mountaineering ropes using the same identical parameters by performing drop tests for a 4.8m fall across a 5mm radius object on a 2.8m section of rope from a totally static anchor. This test represents a violent high-impact force fall (1.7 fall factor) rarely duplicated in actual climbing. The rope is not repositioned during the drop test so the same sections of the rope are subject to the same forces during each drop test and the test is repeated until the rope breaks.  It’s claimed that when ropes finally break during the UIAA drop test, almost 100% of them have the kern melted and fused together by the heat generated during the fall, i.e. the force absorbed during the dynamic stretch of the rope. This ‘UIAA 101’ drop test subjects ropes to tremendous forces to ensure that ropes are safe during normal climbing activities.

Dynamic mountaineering ropes are labelled into three different rope systems; single, half and twin.  UIAA tests are established for each rope system as follows:

A single-rope is dropped with an 80kg weight and must hold five consecutive test drops with an impact force not exceeding 12kn on the first test drop.

Half-ropes are tested with just a single rope of the pair but use a 55kg weight and must hold five consecutive test drops with impact forces not exceeding 8kn during the first test drop.

Twin-ropes are tested as a pair and must hold twelve consecutive test drops with the same maximum impact force as a single-rope (12kn on the first test drop).

Tests show that the impact force goes up at an exponential rate during subsequent test drops until the rope fails.  Dynamic elongation, i.e. the stretched length of the rope when subjected to the test fall, on all three systems must be less than 40%.  Static elongation, i.e. the length of the rope when the weight is hanging freely on it prior to the drop test, must be less than 8% on single and twin-ropes and on half-ropes it must be less than 12%.  All rope systems must have less than 10% sheath slippage (the extent to which the mantel/sheath moves along the kern/core during use).


 

 

Sharp Edges

Sharp edge resistant dynamic certified ropes must hold a single UIAA 101 drop test over a 90 degree edge with a 0.75mm radius. This test is called UIAA 108 Sharp Edge Resistant Dynamic Rope Drop Test.  For some this safety feature is worth considering.  In the past, ropes with this feature had very stiff handling due to a nylon mesh located between the mantle and the kern.  That nylon mesh would protect the kern from cutting on edges.  But, as advancement in rope design has improved over the last few years, it is often deemed unnecessary to use extra material in rope construction to pass the UIAA sharp edge drop test and a number of standard ropes would now pass the UIAA 108 test.  In fact, the sharp edge test has now been suspended until further notice due to inaccuracies in the test data.  (Ropes certified with passing the sharp edge test prior to that suspension remained that way until January 2005.)

 
Does Length Really Matter? ;o)

Traditionally, climbing ropes were always sold in 50m lengths.  Length is something of a personal preference but 60m has become the standard for most climbers; most modern routes require 60m of rope to reach stances, anchors or the top.  However, the longer the rope the more challenging rope management becomes and the greater the weight of the rope.  Pulling up a few extra meters of rope to clip it after a long pitch of hard climbing can be very difficult and may drain strength further and slow the climbing down.  Many classic Alpine rock climbs were put up using 45m or 50m ropes and so a 60m rope can sometimes mean pulling up over 10-15m of rope at the end of every pitch (time and energy sapping over 20 odd pitches!).    70m ropes are now popular with sport climbers and have gained popularity amongst traditional, ice and some alpine climbers.  Their longer length allows climbers to combine pitches, which may increase speed.  Some super skinny single cords are offered in 80m lengths.  As ropes get thinner in diameter the weight decreases, so carrying an extra 10m of rope is the same weight as (and at times even lighter than) thicker 60m single-ropes. Super-long ropes of 100-120m have their uses but the rope management can be a nightmare to manage when on a route.  Climbing moderate alpine routes with these pythons can speed up the ascent to lightning speed, provided you’re going in a fairly straight line (most common in ice climbing).  When the terrain becomes technical, you can double these long cords and use as a standard 60m half-rope.

 

Rope Shrinkage

A rope may shrink in length over time. After a season of use, your 60 meter cord may shrink to 58m, 55m or even shorter.  There are claims that one budget priced rope has been shown to shrink 10m over two years of use due to poor thermal molecular balance of the nylon.  Most high end manufactures cut their ropes a few meters longer than the hang tag indicates.  A 60m cord may actually be 63m in length.  So, after some use your 60m cord is actually 60m in length.  But as time wears on, you may find it shorter than 60m and constantly shrinking. If you climb on half or twin-ropes, you may find that one strand is now quite shorter than the other, this is normal.  High end rope manufacturers spend more research, time and energy in thermo-balancing the nylon to help prevent their ropes changing shape.

 
Dry Treated or Not?

There is a huge misconception about dry treated ropes.  Keeping water out of the rope is a major factor and is what most consumers understand about dry treatments.  However, quality dry treatments are designed to increase the strength of the nylon as well as actually keeping water out of the rope.  Nylon will absorb water and wick it deep into the core, tests have shown that this can decrease significantly the strength of the rope. Tests claim that wet ropes decrease their ability to absorb a fall by as much as 70%, whereas the same ropes with dry treatment may only lose around 40% of their ability to absorb a fall.  Also, dry treated ropes do not necessarily mean the rope is for ice, snow and alpine climbing only.  The dry treatment helps keep dirt out of the core for increased rope life and strength.  It also helps the rope slide with less friction over karabiners, through friction devices and of course over rock and ice. Manufacturers apply dry treatment by different processes and they all work well initially by limiting water absorption into the sheath, with the differences being how long this coating lasts. The big deciding factor is if the core is treated.  Some inexpensive ropes only have the sheath dry treated and this coating wears off after just a few pitches.  Of course the dry treatment on all ropes will wear off the surface area of the sheath with time but if the core is treated, the rope will stay drier for longer and have greater impact force absorbing abilities during a fall. It's the protection of the internal core which increases rope life and safety and that safety margin outweighs the higher initial cost of a high quality dry treatment.

 
Rope Diameters

Ropes come in different diameters but the UIAA drop test does not necessarily use the diameter of the rope as the determining factor for the system the rope will fall into, whether it be single, half or twin.  Single-ropes (currently 8.9-11mm) are used alone and the rope is clipped into each piece of protection as one climbs.  Single-ropes are the easiest to use and are the standard multi-use rope identified with a “1” marked on the labels at each end of the rope.

Half-ropes (typically 8-9mm) are used in pairs as a double rope system (this is often the term used for half-ropes) and are clipped alternately into the protection.  These ropes are good for ice, alpine or for rock areas with edges or traverses because they offer a safety margin over the cutting of both ropes.  They also allow a reduction in rope-drag by allowing each rope to be kept in as straight a line as possible, e.g. one rope used for all runners on the left and the other for runners on the right, as well as giving you full length abseils.  Half-ropes have the lowest impact forces but can be difficult to manage during belay duty - taking in one rope while giving out the other rope at the same time.  Half-ropes are marked with “1/2” on the labels at the end of the rope.

Twin-ropes (7.6-8.5mm) are two ropes used as a single rope, meaning that both are clipped into each piece of protection.  (Because the impact force of a half rope is much higher than that of a twin-rope, it is not good practice to clip both half ropes into a single piece of protection.)  Argumentatively, twin-ropes offer the highest safety margin against total rope failure but the impact force is also the highest of any rope system.  Twin-ropes must be used as identical pairs and are marked with a “T” or “00”on the labels at the ends of the rope.

It is hard to compare like for like diameter ropes between different manufacturers and often a better comparator is to use the weight per metre.  Some ropes will feel comparatively thinner, while others may be labelled as being heavier in grams-per-meter of rope but be labelled with a smaller diameter.  The diameter of a rope is commonly assessed whereby weights (of 10kg for a single rope and 6kg for half-ropes) are added to a three meter section of rope, which then has its diameter measured at 6 different points.  The diameter of the rope is then said to be the average of those 6 measurements.  

 
Caring for your rope

The rope is your lifeline so it is wise to protect and care for it.  Laying your rope on a tarp while climbing will protect it from dirt.  Never step on a rope, especially when wearing crampons.  Ropes should be stored and carried in a rope bag and those with a built-in tarp are a wise choice.  Inspect your rope before and after every use – ‘flake’ it out between your fingers and feel for any imperfections.  Dirty ropes or ropes subjected to a marine environment (as on sea cliffs) should be washed to remove dirt & salt before they have time to grind through the sheath and reduce the life of the rope.  Rope washing solution is available at most climbing equipment shops, as are rope brushes.  These can be used to good effect in cool or luke warm water in a large bowl or bath.  Alternatively, your rope may be washed on the cold & delicate cycle in your washing machine, just be sure to clean out the machine and soap tray first as the remains of the soap and softeners used in washing your clothes will not be kind to your life line.  (The same approach applies to the washing of other items of nylon climbing equipment, i.e. a harness and slings.)  Re-waterproofing ropes will help keep water and dirt out and will also increase the life of your rope.

If you are working a route where the rope is subject to a lot of consecutive falls, it is wise to reposition the rope so the same sections of rope are not subjected to the same forces during each fall.  Also, if you’ve taken a high fall-factor fall, it is always worth letting the rope cool before continuing to climb (this also gives a good excuse to get off the route and calm down!).

 
How long will your rope last?

The lifetime of a rope is a very subjective matter (as with all climbing equipment, careful consideration needs to be given after taking into account all relevant factors).  Manufacturers will often suggest a shelf life for a rope; unused and kept in a dry and dark environment at ‘room’ temperature, a rope may be said to last around 10 years.  You may well ask why it won’t last forever if it’s never used; this is because the nylon in the rope will naturally break down over time, especially when exposed to ultra-violet light (i.e. sunlight).  As conservative estimates, for occasional use, maybe once a month, a rope may last around 3-5 years.  Under regular use, say every weekend, a rope may last around 2-3 years.  Under heavy use, perhaps by a professional instructor, a rope may only last a year, or even less.

The environment in which the rope is used is also an important factor in their longevity.  Ropes used on sandstone will wear more quickly due to the particles of sand they pick up working their way into the core.  Ropes used on very rough granite or gritstone will likely wear through the sheath more quickly than if used on, say, limestone.  At the end of the day, if you’re in doubt about the strength of your rope it’s probably time to retire it; do you really want that doubt creeping up on you when you’re going for the crux move on your next route?

Retire a rope when it attains sheath damage i.e. you can see the core through it, it gains flat or soft spots, it becomes stiff, or if it should hold a single high-impact fall.  A rope should also be retired if it comes into contact with battery acid or similar corrosive materials.  (Black Diamond has an interesting piece here http://www.bdel.com/scene/beta/qc_kp_archive.php about some rough tests on a rope that had been urinated on by a climber’s cat!  It seems that the rope was ‘slightly’ weaker in drop tests than a comparable new rope.  Probably meaning that the cat’s owner would have survived a fall, though we’re not told whether the cat survived its owner’s wrath!)

Ropes can wear through to the core very quickly in the right (or is that wrong?) circumstances.  E.g. I have seen a rope wear through to the core in a matter of minutes where it has been running over an edge while someone top-roped a route and repeatedly put their weight on the rope.  I have also seen even static ropes wear through to the core on an abseil where the rope has been ‘sawing’ over an edge (even static ropes will stretch a little under body weight).  In this situation I always prefer to use a rope protector to preserve the life of the rope (and mine!).

 
So, what’s available?

For the following comparison I have ignored twin ropes as so few Brits use them.  I have also chosen just a handful of the ropes available in the UK market currently.  This list is by no means exhaustive but will hopefully give you a starting point for your shopping trip.


Happy shopping!

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