Date: November 30th, 2006
Jim Ewing is a bud of mine and the head rope guru over at Sterling. We’ve been emailing back and forth about single-rope impact forces vs. half-rope impact forces (as well as the discussion on this blog) for the last few months. Single ropes are tested with a nasty (1.77 fall factor) fall with an 80kg weight, half-ropes are tested with a nasty fall with 55kg. This weight difference has always struck me as odd–I weigh the same (about 85K all dressed up for winter climbing) whether I’m climbing on a single or half ropes, so why is there a different test? Half-rope technique is to generally clip the strands individually, so the impact will normally be on one strand… Furthermore, many people assume that because the “published” numbers for half rope tests show lower impact forces then using a half-rope will result in lower impact forces on a piece of protection (never mind the test weight is different…). Fortunately, Mr. Ewing has access to a drop-test tower and the knowledge to use it. He completed the following tests over the last 24 hours (he also reportedly did some training in the in-house Sterling cave…), here’s the data from Jim on “certified” half ropes tested as single ropes:
_________________________________________________________________________
Here’s the total picture.
Rope A. 80kg-7.35kN, 55kg-5.39kN, published with 55kg-4.85kN
Rope B. 80kg-8.15kN, 55kg-6.23kN, published with 55kg-6.3kN
Rope C. 80kg-8.23kN, 55kg-6.25kN, published with 55kg-6.5kN
Rope D. 80kg-9.22kN, 55kg-5.88kN, published with 55kg-6.1kN
These drops were conducted without the regulation conditioning but complied with all other requirements and procedures. Relative humidity was 42%, temperature was 20ºC for 48 hours.
_____________________________________________________________
Jim also noted that his four test ropes were all new and from different manufacturers, so his data should offer a pretty good spectrum of what’s out there for half ropes tested as single ropes. This is the first solid data I’ve ever seen on half ropes tested as singles, thanks Jim!
Now the fun part: comparing single rope impact forces to half rope impact forces when tested as “single” ropes. Jim’s tests show half rope impact forces with an 80kg weight testing from 7.35kN to 9.22kN. Here are some numbers (taken directly from the BD and Sterling’s web sites):
BD “Joker” 9.1mm: 8.2kn
BD “Booster III” 9.7mm: 7.3Kn
Bd “Apollo II” 11mm: 7.7kN
Sterling “Nitro” 9.8mm: 9.0kN
Sterling “Pro”10.1mm: 8.6kN
Sterling “Mega” 11.2mm: 8.7kN
This range is from 7.7kN to 9.0kN; not a lot of difference from the Half rope range of 7.35kN to 9.22kN…
I draw five main conclusions from Jim’s data:
1. Half ropes likely do not offer significantly lower impact forces than single ropes in high fall-factor falls where one strand is clipped as is common.
2. Rope diameter alone is NOT a good indicator of impact force (some of the “fat” 11mm ropes offer lower impact force than the “skinny” single or half ropes).
3. The “published” impact numbers may not mean much (there’s a wide range between the published and actual in Jim’s data).
4. Terrain is more important for rope selection than impact force. If I’m heading up on a route with sketchy gear I may just use my standard single rope, simpler. A single rope with low-impact force may actually be better. But, for routes where the gear is all over the place then half ropes are likely better for less drag (and possibly less chance of both ropes getting cut…).
5. I’ve got a lot more questions than answers about rope stretch (elongation) with different fall loads–these fall tests are with a very harsh (1.77) fall factor. What happens with low fall-factor loads in terms of elongation and impact forces?
Thanks very much to Jim for working on this. I think this data is the kind we need more of in the climbing world–it challenges our assumptions about equipment in a good way. I don’t think there are many “absolutes” in climbing; the systems we use are surprisingly complex and sometimes very non-intuitive. The best we can do is to try and understand our gear as best we can, and then use what’s appropriate for the situation at hand. Even then we’re likely to get it “wrong” at least some of the time, so having a good margin for error is perhaps the most important part of the climbing process. In climbing we’re always trying to balance multiple different factors; speed vs. safety, speed to get to safety, going light to go fast, bringing enough gear to stay alive if the fast idea doesn’t work, not taking so much gear that progress stops in a dangerous place, backing up gear in case we fall vs. placing so much gear that we will fall, etc. Perhaps those of us involved in the “climbing education” business are placing too much emphasis on the “right way” and not enough on “think it through.”
WG
PS–There’s also a discussion on this going on at Rockclimbing.com.
Posted in: Blog
Date: November 29th, 2006
It’s no secret to regular readers of this blog (and thanks to those who have sent in comments on elbows, ropes and falling!) that I really don’t like George Bush and his crew of Neocon nutters. I’ve always felt they were taking the US down some sort of rabbit hole into an alternate reality where it was OK to treat people like, well, not people. Where it was OK to invade a country (Iraq) not because that country had done something to the US but because, well, because. Where deficits didn’t matter, corporate abuses didn’t matter, workers didn’t matter and the constitution was just a suggestion. I have frequently noted the Bush administration’s invocation of “national security” to justify blatantly un-American actions such as Guantanamo Bay, the suspension of Habeas Corpus, torture and all the things we generally associate with third-world dictatorships but are now somehow OK for the US to sanction. In short, I’ve felt that Bush is the closest thing to a World War II fascist (Hitler, Mussolini) the United States has ever seen. I don’t make that comparison lightly, or for shock effect. As soon as a country starts stripping individual freedom to preserve it something has gone seriously wrong.
This article in Slate does a much better job of explaining the Bush/fascism historical parallels than I can. End of political rant, gotta get one off every month or so…
Training: It’s been cold enough to discourage much outdoor training here of late, but I’ve been hiking, running the dog (getting a dog has done more for my aerobic capacity over the last five years than anything else in life) and doing some yogacizing. Thanks for all the elbow suggestions from various people, I’m doing pretty much all of ’em, let’s hope some healing results soon!
Posted in: Blog
Date: November 27th, 2006
This discussion on falling distances with respect to clipping position is down there somewhere in the comments column, thought I’d post it as a new entry. I’m getting some email on this as well, it’s been fun discussing it all, I hope the following helps people figure it out. Just for the record, it’s generally safer to clip at waist level than over-head.
Anon wrote:
Posted in: Blog
Date: November 24th, 2006
Anchors: Cordelette, Sliding X, or? A brief history of anchor building (with lots left out…)
When I started seriously climbing in the early 80s most of us weren’t thinking all that deeply about equalizing multiple pieces at belay anchors. A couple of slings of roughly the same length on each piece, good to go. Then we realized this wasn’t optimal, and started using the “sliding X,” basically a sling clipped in the middle to equalize two pieces at a belay or on-route (the X keeps the biner from sliding off the sling if one piece blows). Then some “smart” people figured out that if one pice blew with a “sliding X” that it would theoretically shock-load the remaining piece. Cordelettes, basically a long piece of 7mm cord, became all the rage ’cause you could clip multiple pieces together quite quickly, and with what was thought to be good equalization. The preferred material for cordelettes was first 7mm nylon, then 5mm Spectra, then Dyneema, then someone figured out that these types of fibers don’t stretch much which is hard on the anchors in a factor two fall, so it was back to 7mm nylon cord…
Some recent research suggests that cordelettes actually don’t do a very good job at equalizing multiple pieces. In fact, they do a lousy job, and for a reason that in retrospect seems, ah, pretty obvious: If the legs of the cordelette are at all different lengths then they will stretch differently. So if there are two pieces in an anchor, “A” and “B,” with the amount of cord going to “A” twice that of “B” then B will take almost all the force when loaded: less cord to B, less stretch, more load, especially as the cord or anchor point comes close to failing. The cord to A will come into play a tiny bit, but because there is so much more cord going to A the load on A will be relatively minimal… This seems very obvious when thinking it through, but I just took the whole cordelette concept for granted ’cause that’s what the “experts” said to use on belays. Less stretchy webbing isn’t any better, as it’s the relative amount of stretch that matters–if webbing only stretches two percent at load then the short leg will just stetch at 2 percent of it’s length vs. 2 percent of the long leg, same non-equalized loading situation. A cordellete will work great when all the legs are exactly the same length and the load comes from exactly the “planned” direction. My belays generally don’t work like that when climbing (some top-rope or rescue anchors do).
Now there’s also some new research that suggests the shock-loading problems with the “sliding X” aren’t a big problem; in fact, the main problem with the sliding X system is that there can be a lot of friction at the “X,” which reduces the effectiveness of the equalization system. Using a big anodized biner basically solves this. I really have to laugh about this whole subject, I can remember the epic arguments about the sliding X vs. the Cordelette; we were all arguing about the “wrong” factors. The problem with the sliding X wasn’t the shock loading, and the problem with the Cordellete wasn’t the 7mm cord… I actually thought the stretch in the cord would help equalize the various pieces, when in fact it does the opposite. This is why I’m a climber and not working on the space shuttle.
The solution to all of this is something called a “Duo glide.” This a rat’s nest of a knotted cordelette strung together in such a complicated manner that I am really likely to do it wrong in any but the most optimal of conditions. I played with it on my hallway coat rack and could get it right most of the time, but slowly. I don’t like it. Trango makes something called the Alpine Equalizer, which seems promising, but when I alpine climb I want gear that does multiple functions and is easy to deal with. It also requires an overhand knot to work to it’s full potential, and anyone who has tried to untie an overhand in webbing after it’s been loaded, especially in winter, well, good luck…
I’m going back to a sliding X with a big biner, backed up with a sling of about the right length to a third piece. If the belay is so shitty that I feel perfect equalization is in order then I might go for the duo-glide option, but realize I’m basically being an idiot for trusting my life and that of my partner to a dubious belay.
There are several epic discussion on in the internet about this, about the best is here.
I thought Donald Rumsefield was an idiot for talking about “unknown unknowns” and such. He’s still an idiot for other reasons, but in climbing there are a lot of “unknown unknowns.” Anchors should have solid gear tied together in such a way that even if everything in the anchor blows but one piece the system will still hold….
Training: Went climbing yesterday, the elbow is not happy today. I am thinking of cutting the arm off. Bit extreme, might try more physio first.
Posted in: Blog
Date: November 20th, 2006
The ice season is in full swing here–it’s been a bit of an odd November so far, very warm days (+8 Canadian here today, that’s about +50 US) alternating with good periods of colder weather. Most of the higher north-facing routes are “in,” some of the lower north-facing routes are “in,” and the rest is pretty random. It seems like air masses have been very localized; what’s true in K-Country isn’t for the Parkway, and even along the Parkway there is a lot of variety. The conditions pages are in good form.
Training (elbow and aerobics):
The elbow continues to annoy, I haven’t done much climbing in a while, it’s getting pretty aggravating. Some ice (well, not climbing, in plastic bags…), light gym workouts that don’t annoy the elbow, doing my best. My situps are going damn well, I’m in top form for dips and pushups too, but unfortunately these don’t apply to climbing all that well… I’ve been doing a lot of dog training too, beat the old “Chili Dog” record up to the first talus slope on Lady Mac from my house today, round trip 58 minutes (previous best time a little over an hour round-trip, done while training for the X Alps). I’d like to go alpine climbing as there are some new routes worth trying, but pulling ropes through a belay device is one of the things that hurts my elbow most. I’m thinking of going back to a hip-belay, but that might freak some of my partners out, grin. I do trust hip belays if done right, the first lead fall I ever caught was a near factor-two straight onto me and a hip belay. I don’t know who was more stunned that it worked, the leader or me, but it did… I’ve been doing a fair amount of Yoga as well, although I’ve been avoiding Ashtanga classes as I can’t do the “swing through” move to seated or back, too much strain on the elbow. Did a “Hot Yoga” class yesterday while in Calgary, bunch of nutters in a room with the heat cranked up to hallucination hot, pretty fun. Very different from the normal Ashtanga flow stuff I do, seemed good to switch it up. Initiatlly I was OK with taking a break from climbing, but now I’m seriously missing it, the feeling of ice flowing by the tools and good times out with good people is just a big part of my life. Whine whine, I’ll eventually heal ’cause I’m gonna lose it if I don’t get out climbing pretty quick.
Posted in: Blog
Date: November 15th, 2006
I’ve been working on a new slideshow for the Whyte Museum, “20 years of icicles.” Originally I had planned to mainly do the relatively recent history, but then I started thinking about the eras before I was climbing in the Rockies. I called a few friends from that era, and suddenly I had some amazing shots of the “early years” of waterfall ice in the Rockies, absolutely great stuff. So the title now should really be, “Almost 40 years of Icicles” in the Rockies, I’m really fired up to share some great photos from back in the day from various pioneers of waterfall ice climbing. The energy and excitement of those photos from the early 70s to mid-eighties is just too good not to share. When I look at these photos I just have to smile, these guys were somewhere between flat-out crazy and very gifted climbers, likely a lot of both. Thanks to everyone who has graciously shared their photos and stories with me (who knew that warm milk laced with sugar was the ultimate anti-hyopthermia conconction? Thanks Tim Auger), it’s gonna be a fun show.
Posted in: Blog
Date: November 12th, 2006
I’ve spent the last couple of Februarys in Norway, home of big ice and crazy potential. I really like the Norwegian vibe and the endless opportunities for big ice. My friend Andreas Spak has just produced a new Norway web page, it’s a bit rough yet but has some good info, check it out.
I also have some trip reports up on my old Gadfly blog pages, here. Spak’s other site also has some good info.
After a week of crazy warm weather (wet slides, falling ice climbs, etc) the ice is back on here in Alberta. Be careful on the ice, we lost a fellow climber and nearly two due to a slide a week ago. Another climber reportedly had to be rescued after the climb he was on in the Ghost fell down, leaving him precariously balanced on a small rock ledge he managed to somehow catch himself on. His partners went for help, but it was four hours before he was plucked from his stance, likely not so fun. Temperatures are back to “normal” now so collapsing climbs should be less of a problem, but there’s a lot more snow up high than the bare valleys would suggest.
WG
Posted in: Blog
Date: November 10th, 2006
The posts on clipping and falling distances have generated a lot of email. Some graph paper will help in working the various clipping situations; we’re all conditioned to think of the fall distance as twice the amount of rope above the last piece, but when clipping overhead the fall distance isn’t twice the amount of rope above the last piece… Ulimately a fall while clipping is roughly equal to twice the distance between the two pieces, regardless of where the climber falls off while clipping. Diagrams drawn to scale will help sort this out. My friend Bill B sent the following in, good points also–it’s not just starting point of the fall that matters, but also how belayers deal with over-head clips:
“I would consider a couple other factors here; 1. the climber will most always pull thru more rope than he/she needs, 2. the belayer will most always chuck out more slack than the climber will take (this is quickly adjusted for, but after the clip is made). Fall at the wrong moment before making the clip and the fall will certainly be longer than if you clipped at the waist. ” -Bill B.
Understanding the physics allows us to make better decisions about difficult clips. I’ve seen a few accidents recently that just didn’t have to happen, and a couple of other very close calls, I don’t think enough climbers have thought this through carefully.
-WG
Posted in: Blog
Date: November 9th, 2006
Finally back at home after the film festival and participating in the film maker’s seminar. The festival went really well, good fun, and the latest film we made, Aweberg, won a special jury award. The award reads, “This short film represents in a microcosm the spectacular, the audacious, and the pure play that is at the essence of mountain sports.” Thanks very much to the Banff Festival Jury for that, and thanks to everyone who worked on the film as well, it was a pleasure. I just accepted the award–any award for a film is definitely for everyone on the trip, a film doesn’t happen without a lot of people working really hard. Thanks. (A few people wrote asking if they could buy Aweberg–you can buy a pre-commercial DVD here).
The day we showed the film at Banff drew over 500 people, the biggest day-time show of the festival.
I saw a lot of great films at the festival and laid the kindling for several new film projects. The creative buzz is great.
I also took part in the film maker’s seminar, an excellent four-day seminar with Richard Else and Keith Partridge, two of the UK’s best film makers. They had some great insights on how to make better films, and the collection of seminar attendees was also very qualified. I learned a lot both from the Brits and the other people in the seminar, very worth the time although I’m now behind as usual on the mass of email etc…
Best,
wg
Posted in: Blog
Date: November 4th, 2006
As walked into the film maker’s seminar yesterday I found the way forward blocked by a crush of people along the path. You spend a lot of time at the Banff Festivals slowly moving forward through throngs of people, it’s just how it is, so I slowed to a shuffle and couldn’t help but over-hear a conversation about Andy Kirkpatrick’s slide show the previous night. It went something like this:
Head Scarf: “I saw that young British man last night, he had some nice stories but it doesn’t sound like he enjoys climbing very much.”
Large Garments: “Yes, it did seem a bit unhealthy. And such a pity about the language he used, it was almost intolerable.”
Head Scarf: “I really wish he wouldn’t use such blue language, it took away from his nice presentation.”
Andy had shown pictures from some of the worst sufferfests I’d ever seen, and all these women remembered was the language? I think Andy would be dissapointed… If you’re bored check out Andy’s site–I felt much better about my own obsession with climbing and flying after reading the articles on his site, I’m almost normal in comparison. Great site!
One of the best parts about writing a book that people really read is that they send you emails helpfully pointing out mistakes. Grin. Seriously, I do like getting the emails and a guy down in Colorado found a really good error in my Ice and Mixed book. Here’s a quote from our email exchange:
Colorado Guy:
pp. 179-180: The caption of Figure 13a says that clipping at waist level “reduces the distance of any potential fall.” This is a bit misleading. The distance, for both Figure 12a and Figure 13a is twice the distance between the last two anchors, plus rope stretch. It is true that in Figure 13a the climber falls with more rope out and therefore has more stretch, but the main reason for preferring Figure 13a is that the starting point of the fall is farther from the deck. If the deck is far away, clipping high actually provides the softer catch in case of a fall.
To which I responded:
“Ah hell, I just spent two hours working through this with paper diagrams to prove that you’re wrong, but you’re right, grin, good one. There are diagrams spread out all over my desk, my girlfriend Kim got into it too. The overall point of not clipping high overheard when close to the ground “stands” (as I have unfortunately personally tested), but my reasoning was very flawed. I find it very interesting that the total distance fallen when clipping will always be roughly the same, it’s the starting point above the ground that so obviously matters. A much more elegant and correct way to state the situation. Counter-intuitive but true. How does the following text sound to clear this up?”
“Clipping
Clipping bolts or other fixed gear while still close to the ground can be dangerous; if you fall while clipping you may hit the ground. Interestingly, it’s often safer to clip the first few bolts while your harness is level with the bolt rather than reaching overhead to clip the rope in. This seems counter-intuitive, but here’s how it works. First, if you’re clipping over-head you’ll generally put more outward force on the pick as you reach up, which often causes the pick to skate out and off the placement. Second, the total fall while clipping a bolt is always roughly equal to twice the distance between the last clipped bolt and the bolt you’re clipping (plus rope stretch). If you fall off while clipping a bolt above your head you’re more likely to hit the ground because you’re closer to it and have less vertical space to fall. If you blow a clip while clipping with your waist close to the bolt you’ll still fall the same total distance, but because you started the fall higher you’ll hopefully end up with your feet still above the ground. If you have a bomber hook then clipping overheard is often worthwhile, but if the climbing is tenuous wait to clip until your harness is level with the bolt.”
I’ll work on the above a bit, but do you think it more accurately states the reality of falling off while clipping? I have to keep the total words nearly the same for the next printing.
The point about making sketchy clips with your harness next to the bolt is still valid and the illustrations in the book are still accurate, but I got it right for the wrong reasons. If you can’t figure this out take some graph paper and draw situations where the climber falls off while clipping overhead and while clipping with the bolt at waist-level, it simpifies things when the rope and placements are all to scale. Having 10 total feet of rope pulled out to clip two bolts ten feet apart will result in a 20-foot fall; clipping the same bolt with your harness knot exactly beside the biner will also result in a 20-foot fall, you’ll just end up higher above the ground. Bizzare but true, I only burned about ten pieces of graph paper to figure it out, it will likely take smarter readers less graph paper. A corollary to all of this is that blowing an overhead clip while high on a route actually provides a slightly softer (same distance though) fall…
The writer also had another good point: Many climbers assume that a half rope system with one strand clipped into a piece (as it should be unless both ropes are clipped into all pieces) will result in a lower force fall than one taken on a “single” rope. I’ve heard this stated often as a good argument for using half ropes for ice climbing–seems logical to reduce fall forces on ice screws, so half ropes are “better.” I never questioned the basic belief that a half rope provides lower force falls–you can just look at the impact force chart’s on BD’s website, it’s obvious. Actually, it’s not, the weights used to test impact forces are totally different, I just never really thought this through… I’m now not so sure what to think, more research is required.
So thanks to the writer from Boulder for pointing all of this out, it’s interesting.
WG
Posted in: Blog
I’ve read your info regarding clipping and, while I didn’t pull out the graph paper, I did use a string demo and am not seeing your logic.
Here’s my scenario:
– assume a vertical face
bolt3 (30ft above ground – not clipped)
YOU (28ft above ground)
bolt2 (20ft above ground – clipped)
bolt1 (10ft above ground – clipped)
____ground_____________
If you overhead mis-clip 2ft from bolt3 (ie. 8ft above bolt2) then you’ll have 8+2+2=12ft of slack rope and a 24ft fall from 28ft above ground. (You better hope you got less than 4ft rope stretch!!). If you mis-clip at your harness then you have 10ft of slack rope and a 20ft fall from 30ft above ground.
Seems to be safer to clip from the harness at bolt height. What am I missing!?
Hi Anon, you’re definitely right that clipping at waist-level is often safer than clipping overhead. That’s the main point of all of this, so you’re not missing anything in my mind in terms of where it’s generally safer to clip. But your math is wrong in your scenario for total fall distance. I’ve written a few explanations below that I hope will help you understand…
In your scenario you don’t fall twice the distance of the amount of rope you have above the last piece. That’s the error I made as well when I wrote my book. Seems obvious that you would and that’s how we are often taught to think of lead falls, but it doesn’t quite work that way when part of the rope is “above” you. We actually end up the same distance below a piece as the amount of rope we had above the piece when we fell…
It’s funny, I too refused to believe the graph paper for some time until I really counted the squares and thought it through. In your example you correctly have 12 total feet of rope in the system above the last piece at 20 feet. So you’ll definitely end up with 12 total feet of rope below the 20 foot piece after the fall, right? What’s 20 minus 12? 8. If your harness starts the fall at 28 feet and ends at 8 feet how far did you just fall? 20 feet… It’s fun to run this scenario using a “long armed” climber who can clip 6 feet over his/her harness; Now there’s 16 (10 to the missed clip, six from the missed clip to the harness) feet of rope above the last piece and the climber will end up 16 feet below the last piece–four feet off the ground. But the fall is still 20 feet, the “extra” six feet of rope going from the climber’s harness to his attemped clip hand doesn’t increase the fall.
So in your scenario, you actually fall 20 feet and end up 12 feet below the last piece–the two feet of rope going from your harness to the clipping point doesn’t “double” or add to the fall distance. Count your squares on the graph paper, or with the string–the fall distance is exactly 20 feet (ignoring rope stretch, belayer feed, etc.) The KEY difference in the clip at waist and clip overhead scenarios is that the starting point for the fall is higher off the ground when clipping at waist level (safer). Belayers also tend to feed more slack than absolutely necessary, and climbers generally also pull more slack, which adds at least a few more feet of slack in the system when clipping overhead…
Just for fun and ’cause I’m a nerd, think of a climber who has a bomber piece at 100 feet above the ground. He climbs up another 20 feet, rattles in a sketchy piece, and starts climbing down to get back to his bomber piece. Unfortunately, just as he gets his harness level with the bomber piece he falls, the top piece blows, and he goes for a ride. How far is he going to fall? 20 feet? 40 feet? 80 feet? He has 40 feet of rope above the last piece now, our “classic logic” would tell us he’s going to go 80 feet… Nope, he’s going to end up 40 feet below the “bomber” piece because he had 40 feet of rope above it. Total fall 40 feet… This is just an exaggerated version of the clipping overhead scenario.
I’ve had a half-dozen discussions on this now. I expect a non-climbing math student would figure this out very fast, but as climbers we have a very strong, almost religious belief that fall distance equals twice the rope above the last piece. In the last two weeks I’ve had three major beliefs I hold about climbing seriously revised: fall distance, half-rope impact forces, and the use of Cordelettes…