Most of what you’ll read there is based on actual tests we conducted right here in Tucson. In other cases, we’ve directly contacted individuals who have conducted controlled tests themselves.
How am I qualified to bust these myths? Judge for yourself. A lot of the time I’ve done research on what seasoned, trained climbers have tested themselves. As for my credentials: I’m an AMGA Certified Rock Instructor, I have multiple degrees involving research, thousands of days in the field, a good head on my shoulders, and lots of training from recognized experts.
Keep in mind a few things: I’ve edited most of the anecdotes to keep them succinct. It’s only necessary here to present the facts, not lengthy periodical-like papers. But don’t assume that hasn’t crossed my mind. If you’re questioning what you read below, good. That’s the point. Think critically and test things yourself in a safe environment. Nothing is better for building your confidence than your own experience.
Are carabiners fragile?
Steve Nagode, a quality assurance engineer with REI, conducted an experiment in which carabiners were dropped six times from a distance of 10 meters onto a concrete floor. The breaking strength of the carabiners was then determined with a 50-kN load cell. The results: no reduction in strength was observed when comparing the dropped carabiners with carabiners that had not been dropped.
Black Diamond’s website says this: “It’s best to inspect dropped gear for dings and significant trauma. If only light scratching is visible and gate action is still good, there is a good chance it is fit for usage.”
Here’s a more colorful test, this time done with a Petzl Reverso: I call this “Reverso VS .357 Magnum”. Shooting a small object with a snubnose .357 from a safe distance is tricky, but yields thrilling results. This is akin to throwing the Reverso into a rock surface at 67m/s, which would require dropping it 240m (790 feet). And these calculations omit air resistance, which limits the terminal velocity of the Reverso free-falling to around 35m/s (the terminal velocity of a baseball). The Reverso bent various ways, but it took 5 direct hits before it actually broke. This seems to indicate that a single, short drop for a piece of hardware does little to no damage.
Is spectra good to use for friction hitches?
Spectra produces much less friction than nylon. In “Comparative Testing of High Strength Cord” by Tom Moyer, Paul Tusting, and Chris Harmston, the authors found that the autobloc grip strength of Mountain Tools Ultratape (a nylon/spectra blend) was about 1/5-1/10 as strong as cords with a nylon cover. Thin dyneema slings I have tested were quite slick; I found them slipping under body weight when wrapped 5-6 times around a new rope. A 5.5 mm nylon cord under the same conditions gripped very well. For this reason, it’s probably best NOT to use dyneema for an autobloc.
What about melting? The melting point of spectra (297 F) is significantly lower than the melting point of Nylon-6 (Perlon) at 428 F. Spectra rapidly loses strength above 257 degrees Farenheight. The question is, however, how hot does it get under an autobloc sliding along a rope? Using a meat thermometer I found that the temperature under an autobloc on a single-rope rappel of about 100 feet does not go above 120 degrees F. So melting does not appear to be an issue, although lack of friction still remains a concern.
Will a clove hitch slip if it is loaded too much?
A properly tied and set clove hitch on a carabiner does not slip significantly under body weight. We wanted to see what happened under higher load, so we pull tested a clove hitch tied on a carabiner with a heavily-used 9.6mm rope. We started by pulling it to 1150 pounds (with a car). The rope crept about five inches. The clove was then pull tested to failure. No further slip occurred as it was pulled to higher loads. The rope broke at the entry point to the clove hitch at 2700 pounds.
Can a flat overhand fail during a rappel?
I’ve found only one documented case in which a climbing party claimed that a flat overhand (aka a Euro Death Knot) “untied itself” during a rappel (9/12/1997, Guide’s Wall, Grand Teton NP). In this case, the party had rappelled multiple pitches with the EDK, but just before the accident, someone in the party untied the EDK and then “retied” it. The newly tied “knot” untied itself during the next rappel. Countless pull tests and probably a million rappels since then have failed to replicate what happened. More than likely, the retied “knot” was not a flat overhand.
Quite a few tests, however, have demonstrated that the flat overhand is quite strong. In 2000, Burton Moomaw, an AMGA Certified Rock Instructor, pull tested the flat overhand tied in two single dynamic lines. He found that the knot inverted at 1400 pounds, then did nothing further as it was subjected to higher loads. (Source: direct communication)
In 2005, Jeff Fassett (also a Certified Rock Instructor), completed an unusual and humorous test on the flat overhand. After using a flat overhand to tie a dynamic line in a continuous loop, he dragged a 6,000 pound van with it. The van was in park with the emergency brake on! Based on the vehicle weight and the friction of the tires, he calcluated the load on the knot to be 1500 pounds. The knot did not invert or slip. He repeated the test using the flat overhand to join an 8.5mm rope and a 10.5 mm rope. Again, the knot neither failed nor inverted. (Source: direct communication)
Tom Moyer performed a series of tests on the flat overhand. He found that properly tied and set flat overhands did not roll until loads of 1400-2400 pounds were applied. If the ropes were soaked and of significantly different diameters, he found that the knot could initially invert at a load of 950 pounds. However, subsequent inversions required 1070-1400 pound loads. (Source: http://www.xmission.com/~tmoyer/testing/EDK.html)
Black Diamond pull tested flat overhands and found that they held 2800-5000 pounds before inverting (depending on the diameter of rope).
It is difficult to produce loads of even 600 pounds on a rappel. Jeff Fassett and I measured the force produced on an anchor during a double-rope rappel using a dynamometer. Not surprisingly, during normal rappelling the force on the anchor was simply body weight (in our measurements, 150 pounds). In this case, the load on the flat overhand is 75 pounds. Even with rigorous 5-foot deadfalls close to the anchor, e anchor, we were unable to produce a load greater than 600 pounds on the anchor. In this case, the load on the flat overhand is only 300 pounds. (These tests were conducted with a heavily-used 10.2 mm Beal dynamic line and a 150 pound person.)
Based on these measurements, the following conclusions can be drawn: The flat overhand is about 18 times stronger than it needs to be for rappelling when using two single, dry ropes, and rappelling normally. Very aggressive rappelling may cut this margin down to a 5-fold difference. Under the worst of conditions tested (two soaking wet ropes of different diameters), the flat overhand is still 12 times stronger than the anticipated load on the anchor. Very aggressive rappelling may cut this margin down to a 3-fold difference. Even if the “roll load” of the knot is exceeded, it would take repeated, increasing loads to cause additional knot inversions.
What’s the best way to tie in to the anchor on multipitch climbs?
Climbers will generally attach themselves to the anchor with a clove hitch on their rope. Sometimes people will use a Personal Anchor System, slings, or another tether to clip in.
Daisy chains have limited usefulness if you are not aid climbing. They are bulky and are a poor means attaching to the anchor. Slings and Personal Anchor Systems are not as bulky as you may be carrying them for your climb, but are also not the best choice for tying in.
Consider these facts:
- The rope’s there anyway. Use of a daisy chain or PAS adds unnecessary items you carry on the route.
- The rope is much more adjustable. A clove hitch can be adjusted seamlessly to any length, while most daisy chains or personal anchors are limited to ~4 feet. This will leave you in a hanging belay if the best stance is six feet below the anchor.
- The rope is resistant to being cut.
- The rope is better able to absorb shock loads than a daisy chain. Some people argue that this is incorrect over a short length of rope. We decided to test this to find out.
Jeff Fassett and I conducted a simple test using a dynamometer attached to a bolted anchor. In the first part of the test, I attached to the anchor using a daisy chain so that i hung freely two feet below it. With a backup rope in place, I pulled myself up a few inches and let go so that I fell statically on to the anchor. The force on the anchor was shocking – the dynamometer measured a peak force of 900 pounds on the first drop. I subsequently took slightly further falls, and found that the force on the anchor was over 2,000 pounds when falling just one foot. I stopped at this point simply for comfort.
In a test performed by Tim Holden, Bill May, & Rich Farnham, a test dummy produced peak loads over 2,000 pounds when taking factor 1 falls on daisy chains. The paper containing this test can be found at http://www.itrsonline.org/PapersFolder/2009/Holden-May-Farnham2009_ITRSPaper.pdf.
Similar tests conducted at BlueWater found that a two-foot fall (with a test weight) caused a two-foot sling to completely fail. This is consistent with the simple data we obtained; in sum, it is likely that falling two feet on to a daisy chain will cause (at the minimum) a failure of that loop.
On a candid note, I can confirm that if you did not cause the daisy chain to fail, you would almost certainly sustain injury.
The story changes significantly if you are attached to the anchor with a climbing rope and a clove hitch. Jeff and I repeated the test: this time, however, I was attached to the anchor with my climbing rope tied at two feet long (the same length of daisy chain used above). I immediately noticed that short, static falls on the anchor were far less jolting, and the dynamometer confirmed my suspicions. When falling one foot on the climbing rope, the force was about 400 pounds. On subsequent, longer falls, we found that even falling two feet (the full length of the rope I had tied) the force on the anchor was only 1,000 pounds.
Is it ok to use a grigri for trad climbing?
There’s risks and benefits with each kind of belay device. Obviously, the big advantage to use of a GriGri is the assisted belay.
However, Use of a GriGri for traditional climbing makes it more likely that marginal placements / low rated pieces will fail.
With a GriGri, a fall is stopped relatively abruptly when compared to a plate device such as an ATC. The reason for this is the very limited amount of slipping that occurs when a GriGri arrests a fall. An ATC, however, allows the rope to slip through the device during a fall, arresting the fall more slowly.
Beal did a nice comparison between belay plates (ATC) and autolock devices (GriGri) and has it posted at http://bealplanet.com/sport/anglais/facteurdechute.php. Breifly, depending on the rope’s impact force and friction in the system, they found that the force exerted on the top piece was consistantly higher when using a GriGri versus an ATC.
We decided to do a test of our own to get some real-world measurements. After climbing up 40 feet on a sport climb with a heavy, clunky industial dynamometer strapped to my back, I took repeated 10-foot falls and measured the maximum force on the bolt with each fall. After five falls were caught on the GriGri and five falls were caught using an ATC, we repeated the test, this time falling from a bolt closer to the ground (20 feet).
In both cases, the force exerted on the top piece was higher when using a GriGri than with an ATC. When the foot falls were arrested in the first test (falling from 40 feet), the average maximum force on the bolt was 820 pounds with the GriGri as opposed to 435 pounds with the ATC. With less rope out (falling from 20 feet), the force exerted on the top piece was higher, although interestingly, the difference between the two devices was smaller: the average for the GriGri was 1030 pounds while the average for the ATC was 900 pounds. Note that these differences are less pronounced than what the Beal website found.
The significance of this for traditional climbing is that the gear used is weaker than a correctly placed bolt. Moreover, the strength of a traditional placement also depends on the nature of the rock, the shape of the feature the climber is trying to protect, the type of gear that is placed in the feature, and a host of subtleties that are dependant on the skill and experience of the leader. So while a traditional placement may be as strong as the gear is rated (generally 5 to 16 kN, or more simply put 1100-3600 pounds), in practice most placements can be weaker.
So the question that we need to ask ourselves is how good the gear is on the climb we are planning to do. If you are climbing on bomber gear in bomber rock, the difference between a GriGri and a plate is probably not that big of a deal. If you are climbing on sketchy gear in poor rock, then you’ll probably benefit from the softer catch a belay plate provides.
I’ve received a number of comments on this piece. A lot of people think that they can provide a soft enough catch with a GriGri with a well-timed jump. Keep in mind this will be difficult in a hanging belay situation or when tied in close to the anchor. I haven’t seen research with actual measurements on soft catches with a GriGri vs an ATC but if you are aware of some please send me a link.
Can I use a Sharpie to mark the middle of my rope?
For background, consider the number of people you know who have used Sharpies or other markers for their ropes. I personally know a number of professional guides who have done this for their institutional ropes. To my knowledge there are no reported rope failures attributed to permanent marker use.
I’ll confess at this point that I have used Sharpies on all of my ropes and have yet to notice a difference in wear. Using one of these ropes (which was heavily used and re-marked at least five times during its working life) I started with a simple pull test. This demonstrated that the marked region was stronger than the figure 8 at the end of the rope. Black Diamond carried out similar tests and posted them here: http://web3.bdel.com/scene/beta/qc_kp_archive.php#120308
I began to wonder if the ink even makes it to the core of the rope. I cut open the rope and found that the ink did not make it to the core of the rope.
Well what could happen if the ink did make it to the core of the rope? To find out, I marked and pull tested 10 strands. To minimize loss of strength due to knots, I wrapped the cord around a carabiner multiple times. In all cases I was unable to break the cord at the marked location.
There are a couple of caveats worthy of mention: the formula of permanent markers could vary or be changed, even within the same brand. Also, concerns have been raised about ropes cutting more easily over edges if marked – I did not test this for this this short piece. But if you are in the middle of a 10 pitch descent and your partner mentions that he marked the rope you are using with a marker, you can finish rapping down without worrying about it.
Here is Bluewater’s take:
(retreived 11/22/13 from http://bluewaterropes.com/home/FAQ.asp):
“What is the beta on marking pens?
Marking pens are fine to use on ropes as long as they are water based laundry markers. Years ago solvent based markers were the norm. Some of the solvents used in these old pens could reduce the strength of the sheath strands marked. These days most pens are water based so this is not as much of an issue as in years passed. We recommend a Sharpie “rub a dub” laundry marking pen.
Why does BlueWater not use factory middle marks on dynamic ropes?
Factory middle marks are ok until one end of the rope gets chopped off. Then the factory mark is no longer in the middle. Hmmm- look at the back of any telephone book here in the great Nation of America. If an end user gets hurts because their mark is no longer in the middle what would one expect to happen? We prefer the end user to make all marks so they are intimately familiar with which of the marks on their rope is the correct center mark. This can be accomplished by different styles of marking using a series of bands so the correct mark can be identified. A unique marking also helps to better identify ownership on your rope as well as the rest of your gear!”