Forum Index » Mountaineering & Alpinism » safe working load - rope question


Display Avatars Sort By:
MARK D
(bosrocker51) - F

Locale: Boston, MA
safe working load - rope question on 02/20/2010 13:49:15 MST Print View

I am totally new to mountaineering, despite years of ski patrolling, etc.. I'm looking for some guidance on safe working load limits on rope.

Regarding safe working load (SWL) I've seen different numbers used, like 10% of a rope rated at 5000 lbs is correct, or is it 20%, or is it 1/15th (about 7% - this is confusing. Any guidance is welcome. Obviously, the less strain you put on a rope the better, but how far can you push it, and what is a good standard to apply?

My main interest in this subject is to not die while rappelling and getting info for safe rappelling from a chairlift or short cliff. thanks.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
rope questions on 02/20/2010 14:27:24 MST Print View

The answer is: it depends.

Part of it depends on the type of rope and its intended use. For example, there are dynamic ropes that stretch and are used for lead climbing. There are static ropes that do not stretch very much and are often used for rappelling. There are kernmantle ropes and laid (twisted) ropes. Some ropes are intended to protect a leader fall for only some small number of tries, and then it should be retired. Some are good for only a few years after manufacture.

Often, when you buy a new rope, it will have a tag on it that spells out some or all of its specs.
--B.G.--

nanook ofthenorth
(nanookofthenorth) - MLife
need more info on 02/20/2010 14:47:02 MST Print View

from what you posted I'm a little confused - what are you doing with it?
Chairlift evac is different then glacier travel - you use the rope differently. Could you elaborate?
btw safe working load is a measure of the ropes strength in a static situation - a dynamic rope in a fall is quite diffrent

Edited by nanookofthenorth on 02/20/2010 14:48:58 MST.

Craig W.
(xnomanx) - F - M
Re: safe working load - rope question on 02/20/2010 15:03:06 MST Print View

If you're talking about a single person rappelling (and you're not taking falls on it), just get a good approved static rope. I have one of these for canyoneering/rappelling:

http://www.rei.com/product/793079?preferredSku=7930790014&cm_mmc=cse_froogle-_-datafeed-_-product-_-7930790014&mr:trackingCode=6D847AF1-E390-DE11-B4D4-0019B9C043EB&mr:referralID=NA

Under typical circumstances you'd be pretty hard pressed to make a 32Kn rope fail while rappelling unless you were trying to lower livestock over sharp edge.

Your question is a little vague though...do you know what you're doing?
Rappelling is a pretty straightforward task...I wouldn't be worried about the strength of a UIAA approved rope- I'd be more concerned with knowing knots, anchors, and climbing safety.

Edited by xnomanx on 02/20/2010 15:03:49 MST.

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
light ropes on 02/20/2010 15:15:45 MST Print View

This being BPL and all, are there lightweight ropes that would be appropriate for light scrambling, the occasional rappel while canyoneering, etc.? (I'm NOT interested in real mountaineering, just roping-in on the occasional scramble.)

For a static rope, what about this:

http://www.rei.com/product/751495

Or is 9.2KN simply not enough?

(What I know about ropes I could write on my palm...)

Edited by acrosome on 02/20/2010 15:20:43 MST.

Craig W.
(xnomanx) - F - M
Re: light ropes on 02/20/2010 15:28:47 MST Print View

That rope would be fine.
Many people use even lighter 8mm ropes for alpine climbing- running a twin/double rope while leading (two 8mm simultaneously/one doubled 8mm)and then rappelling on a single.

A single person rappelling really doesn't put much force on a rope if you're not trying to pendulum, bounce around, make sudden stops, etc.

As for a 9KN, 10.2mm rope, that's pretty much standard for rock climbing: taking a limited number of lead falls that place an enormous amount of stress on a system (a rope is rated for a certain number of falls of a certain force). I can't see what you'd be doing while simply "scrambling", rappelling, or canyoneering (activities that typically involve going down, not shock loading a rope after falling while going up) that would take one of these ropes to it's limit- they're made for far worse.

This article will explain a lot about ropes to non-climbers:
http://www.alpineexposures.com/pages/faq-climbing-ropes-explained-test-uiaa

There's a small link in it explaining fall factors: that will answer many questions and is essential knowledge for climbing safety.

Edited by xnomanx on 02/20/2010 15:31:13 MST.

nanook ofthenorth
(nanookofthenorth) - MLife
glacier roper on 02/20/2010 15:30:39 MST Print View

I think your looking for a glacier rope, 30-40m of 8mm double rope sold for glacier travel. If you are climbing with it and placing protection for the leader you NEED a dynamic rope. Even for simple glacier travel a dynamic rope is highly recommended. If the leader is just scrambling up, finding a good stance, and belaying the second you could go with as small a static rope as you could handle, I might sugest wearing gloves too.
I have heard of people using 5.5mm tech cord as a retrieval line for their dynamic rope.

nanook ofthenorth
(nanookofthenorth) - MLife
not a staic rope on 02/20/2010 15:34:06 MST Print View

Dean,http://www.rei.com/product/751495, is not a staic rope - it is a dynamic one. 9.2kn is the impact force of the rope. Rather then repeat what others have written better, could I suggest that you try any of the excellent books in the Mountaineers Outdoors Expert Series? Their one on alpine climbing is really excellent and should answer many of your questions.

Craig W.
(xnomanx) - F - M
Re: not a staic rope on 02/20/2010 15:43:17 MST Print View

This gets hard to explain on the internet...

If a rope is being solely used for hauling or lowering STATIC loads, a STATIC (non-stretching) rope is preferable- less stretch/bounce usually means more control.

If there is any chance a DYNAMIC load (sudden force) will be placed on a rope, a DYNAMIC (stretching) rope is needed- stretch means a softer catch and SAFER fall.

Imagine freefalling 10 feet on a static rope: jerking to a stop. You could break your back- thus the need for dynamic climbing ropes.

But where this becomes hard to give advice (and probably a bad idea to do so):
I don't know what a rope for "scrambling" is. What is "scrambling"? What does your style of "canyoneering" entail? Is there a chance for a fall? What sort of anchors are being used in the belay? Is there a belay anchor?

*****It's all too vague (and therefor probably dangerous) to give climbing/hardware advice over the internet. Nobody knows the experience level of those giving advice, nor the experience level of the audience.

Edit: And Dean, as Robert pointed out, the rope you posted is dynamic. I didn't notice you referred to it as a static. Crucial difference.

Edited by xnomanx on 02/20/2010 15:55:30 MST.

MARK D
(bosrocker51) - F

Locale: Boston, MA
rappelling rope - Safe Working Load on 02/20/2010 15:49:28 MST Print View

Wow - thanks for the replies so far. My primary interest is a static rope which is light & easy to carry, will support me and fit my Kong Robot or black diamond rappelling plate (it's gold...), and have a safe working load. If I bring this gear with me skiing, I will probably bring a 6 or 7mm rope and 1" webbing to make a sling with.

I currently have 8mm static rope - about 45 ft worth. I looked at Technora 5mm line, some 6 and 7 mm static line as well - I don't need (or want to carry) 10mm line or similar heavier rope. For a chairlift evac or rappelling down a 15 ft cliff in dry weather, I don't need 60 meters of 10mm line.

I do not expect to drag this line over sharp rocks, fall with it or anything else, just looking for some guidance on good rope that is safe for a 175lb guy with skis & boots on. So - what protocol do YOU use when determining safe working load? hmmm?

Edited by bosrocker51 on 02/20/2010 15:59:59 MST.

nanook ofthenorth
(nanookofthenorth) - MLife
rap rope on 02/20/2010 15:56:50 MST Print View

Hi Mark - sounds like you just want a line to rap off of when skiing gnarly terrain. Look at the accessory lines - 6,7mm? If you go for 8mm a dynamic 1/2 rope is more versatile. Bear in mind that knots in the rope decrease strength by 20-60% depending on the knot, so take that into account when planning your safe working load.
I use a 8mm dynamic for what your talking about, but I also use it on the way up and on glaiers. You could with practice leave the plate behind and just use a munter or a dufaldortz rappel (as in fixed lines into chutes).
Hope that points you in the right direction, not sure how comfortabule I feel giving spicific pointers online, a guide would be able to set you straight and might have some other better susgetions.
Cheers

Edited by nanookofthenorth on 02/20/2010 15:58:25 MST.

Craig W.
(xnomanx) - F - M
Re: safe working load - rope question on 02/20/2010 16:29:26 MST Print View

I'm not sure if a Kong or the BD device you have can safely use rope thinner than 8mm anyway- if that's what you carry, I'd stick with your 8mm.

nanook ofthenorth
(nanookofthenorth) - MLife
... on 02/20/2010 16:46:00 MST Print View

munter is lighter and cheaper and work on smaller ropes --- bring your gloves!

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: safe working load - rope question on 02/20/2010 17:48:35 MST Print View

First of all, you need to distinguish between industrial use in a commercial environment and personal use in the mountains.
* For commercial use you need to have a generous safety margin for two reasons: litigation, and careless workers. This is where safety margins are used.
* For personal use: you need to be sure the rope can take the load. This is hugely different. (And remember that dynamic loads are greater than static loads while abseiling.)

The next thing to consider is how and where you deploy the rope. I use 40 m of 6 (six) mm kernmantle for scrambling and abseiling (BD ATC descender) while WALKING in the mountains. The strength is perfectly adequate even as a single rope for how I use it (pack hauling, top roping). But this does NOT including lead climbing and dynamic falls! Nor does it include full-on canyoning (for which I use 10.5 mm static ropes).
And when I get home the rope gets spread out on the floor and I check every foot of it between my fingers, while cleaning and drying it. Then it is carefully stored in the dry/dark.

This rope will not die from the loads we put on it. It will probably die from abrasion over rock edges and embedded dirt. When it shows damage it will be replaced.

Would I recommend this weight rope to you? No. Nor would I recommend any weight rope to anyone. My wife and I are both experienced rock climbers and we know what we are doing. I strongly recommend you start by getting some training in rope-use and abseiling from a rock climber (not from an industrial rope-use teacher). And that training should happen in the mountains. Then, you make your own mind up.

Cheers

David Olsen
(oware)

Locale: Steptoe Butte
Re: safe working load - rope question on 02/20/2010 18:18:30 MST Print View

You need to check with the ski patrol organizations. They
do this stuff all the time and most ski areas provide the
rope anyway. Last one I had was 6 mil. and was used doubled
over the chair so it could be retrieved and wouldn't be
left to tangle in the works. This was 20 years ago and may
not be considered safe anymore, so I would
check protocol with your ski area. Your device may not be
the right one for this purpose.

Do you expect to lower a dog too?

Douglas Ray
(dirtbagclimber)

Locale: Pacific Northwest
Strong enough to rappel from? on 02/20/2010 18:49:45 MST Print View

I think this topic has been well covered in the posts above, but I'll throw in my two cents as someone who is bot a climber and used to rappel for a living.

Technically a rappel system only needs to hold your body weight, although I've read that someone did some tests and figured out that by bouncing and swinging around while hanging on the rope one can effectively double the force on it. So generally, I figure that I don't end up weighing more than 220lb,or 1kn, so rappel system only needs to cope with a 2kn load at most.

Knots and such can weaken a system by as much as 50% (actually more, but I just don't use weaker knots than that when my life is on the line). So that means in theory one could safely rappel on a single strand of 4mm line.

In reality you want to have margin for things to wear some in use, and looking at something the size of a boot lace that you are hanging from is scary, and trying to get enough friction to safely rappel on such a tiny cord would be very difficult. I've used webbing of that strength to build rappel anchors in the mountains, but that is a one-time use application. Rappelling on any cord smaller than 8mm tends to be troublesome with any sort of standard device.

I would say check with the makers of your rappel device and see what the minimum size they recommend is. I don't think I've ever talked to someone who has used anything smaller than 5mm cord to actually rappel on, and I think with something that small the only way to get enough friction would be with a supermunter knot, and the cord would need to be retired very often.

I'd worry more about creating friction and controlling your descent than the cord breaking. 6mm would be comfortable for me in the situation mentioned if I had a good way to make friction. Double strands can help a lot in this regard.

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
Static? on 02/20/2010 18:50:07 MST Print View

Interesting. That rope came up when I searched for "static rope" on rei.com. That'll teach me to trust them...

Well, I'm not the OP, but I think MY question was answered.

By "scrambling" I mean hitting the occasional terrain somewhere between hiking and mountaineering, as in the "75 Scrambles in Washington" guidebook. Class 3 or maybe low class 4. In other words, situations in which a timid hiking partner might appreciate a top belay. I want nothing to do with a climb that would require real protection or have a real risk of a significant, long fall. Also, I'm not really interested in truly technical canyoneering, but I have noticed that there are a LOT of canyon routes that only require a short rappel or two, and I'd like to access them. (I guess being able to use an ascender would be nice, too.) Despite my ignorance, I have rappelled quite a bit, both single- and double-strand. But I have always used military rappelling ropes, even when rappelling on my own. I've only ever used carabiners and figure-8 descenders as a rappelling device, and I'm quite comfortable with them. And I prefer a Swiss seat to a real rappelling harness. (Because I can easily make one on demand, and a short bit of rope is more multi-use than a harness.)

So, it sounds like an 8mm (or perhaps even smaller) static rope would be adequate, and still generate enough friction for rappelling?

I'll read more. Oddly, I do have a mountaineering book someone gave me as a gift once, as well as the Army mountaineering manual.

Thanks, All.

Edited by acrosome on 02/20/2010 19:01:11 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
How times have changed! on 02/20/2010 18:59:14 MST Print View

Almost forty years ago, I was an assistant instructor in an Army rappelling class, and all we had back then was a short equipment list. 150' lengths of (green) half-inch laid nylon rope. Swiss seat instead of a harness. Two carabiners per person. Leather gloves. Period. No modern rappelling devices. No kernmantle ropes.

--B.G.--

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
Army mountaineering on 02/20/2010 19:03:41 MST Print View

@Bob-

We are truly dinosaurs, Brother. That green twisted (whatever that is called, not kernmantle) nylon rope is exactly what I'm talking about! But you should SEE the new update of the Army mountaineering manual that just came out a couple of years ago: magic slippers, plastic mountaineering boots, all manner of exotic protection, etc.- all kinds of whiz-bang stuff.

Edited by acrosome on 02/20/2010 19:05:40 MST.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
reply to Dean on 02/20/2010 19:09:05 MST Print View

Say it isn't so!

Back in the day, all of our rappelling friction was on two carabiners, so by the time we had zipped down 100 feet or so, there was a very hot carabiner almost lined up with the forearm. I still have faint burn scars from that.

Dinosaur, indeed. This was near the DMZ in a faraway land.

--B.G.--