physics of Half rope method

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Francis

Trad climber
San Francisco
Topic Author's Original Post - Apr 12, 2009 - 09:33am PT
Happy Easter,

I have been obsessing on getting info about double ropes (aka half ropes not twin ropes). I get the reasons to use them and practiced it this last week using my two single ropes which are about 9.8. One is older than the other and is ready to be replaced...

Which leads me to questions about the diameter of half ropes and the logic or physics behind the ratings and fall safety of them. I probably am not going to articulate my question precisely but will try to.

Basically, it centers on why an 8ish rope is acceptable for half ropes. If and when you fall, are you still not falling on one rope, over a single edge? Does the physics of a fall change when you are using the Double rope technique? On your first piece, I am assuming it would be exactly the same as with a single rope as you have only one rope through one piece. If this is the case, then why would you be ok with having less of a fall rating?

Thanks climbing scientists!
Brutus of Wyde

climber
Old Climbers' Home, Oakland CA
Apr 12, 2009 - 09:45am PT
Here is a good place to start:

http://www.tradgirl.com/climbing_faq/advanced.htm#doubles

What I take away from this discussion is that half ropes have their place, and a leader always has the option of clipping both halves into a single, bomber, piece of pro (using separate carabiners) if facing long runouts, or the potential of death if a single-clipped strand would fail (such as your "first piece" scenario). Load limiters (such as Yates Screamers) also have their place in my toolbox of half-rope tricks.

You may take something else entirely from reading it, so I suggest a first-hand look.

Hope this helps.

Brutus
WBraun

climber
Apr 12, 2009 - 09:45am PT
Two 9.8 mm ropes are monsters. By the time you get to the end of a long pitch those ropes will pull you off.

I climb on a single 9.2 mm rope now.

Before that for over 10 years I climbed on a single 8.8 mm.
roy

Social climber
New Zealand -> Santa Barbara
Apr 12, 2009 - 09:56am PT
Hi,

My take as a double roping sometimes climbing engineer/scientist...

It's a trade-off. The fall on an individual rope is probably slightly riskier, but breaking a rope is very rare. Cutting the rope by running it over a sharp edge might happen but in that case you have a second rope waiting to catch your now somewhat slowed fall. If you're a wuss like me and closely space your gear then both ropes will catch you (word of experience here) giving better gear load distribution than a single rope.

The other advantages are: double length rappels; lower drag on wandering routes; being closely protected while pulling up the other rope to clip; backup in case of a damaged rope. The main disadvantage is the greater potential for a cluster and the need for greater belay skills.

Cheers, Roy

Steve Grossman

Trad climber
Seattle, WA
Apr 12, 2009 - 11:02am PT
Worth noting is the elongation under load for skinnier ropes. If you are using the double ropes traditionally to be able to spread apart your protection points with minimal drag then factor in the increased length of falls due to individual rope stretch when only one side of the system is loaded.
tradmanclimbs

Ice climber
Pomfert VT
Apr 12, 2009 - 11:06am PT
Skinny doubble ropes make total sense for multi pitch ice climbing. they make no sense at all for single pitch climbing. I use them for multi pitch rock as well simply because I hate the idea of dragging arround a heavy tag line. I have gotten totally spoiled with the option for full length raps and retrete whenever I feel the need.

The system is a pain in the butt though. easy to cluster, hard to belay properly. Still better than dragging a tag line for most of whAT I climb. If I climbed a lot of splitter cracks I would lead on a single and trail a line off the back of my harness. Doubbles suck in splitters. twice as much rope to get jammed against your feet.

I would say in the 11 years that I have been climbing on doubbles that 85% of the falls were caught on a single line. The other 15% were on both strands running through a single biner. It is nice to be able to place 2 pieces and clip one to each rope for a sketchy move but I have never actually fallen when I have rigged it that way.

Its nice in theory to speculate that you can provide a better belay by keeping red short while the leader clips blue but in real life it dosen't work that way. A Real fall in that situation would most likly resuly in a fair ammount of rope slippage while the belayer juggles fingers trying to brake the right rope. In reale life practice the belayer is more likly to feed the wrong rope and short you on the one you are trying to clip. then once you do get clipped you stand a decent chance of getting short roped on the other strand when you start climbing again.
System works great on ice where you don't keep the leader as snug as with rock. For hard rock climbing it is much easier to feed a single for fast desperate clips. Shoot out that slac and then reel it in fast when you hear the gate snap or the leader grunts, CLIPPED! If I am on an multi pitch climb and useing the half ropes if I have a line of bolts I will inform my belayer and treat the half ropes as twins and just clip em both to each draw. This is the easiest way to enshuer that you will get a decent belay and not get short roped or dropped.

I have concluded that doubbles are a PITA but I am a big chicken and I like the extra rope for retrete. I also like the rudundancy for cut protection when climbing in sharp nasty places. The price for being a chicken is that I must endure the doubble rope system on multi pitch climbs. If you are NOT a chicken then do yourself a HUGE favor and don't bother ;)

There are a few traverseing climbs arround where the doubbles really make it safe for your 2nd which is nice and a few where the doubbles really do help with the rope drag.

ec

climber
ca
Apr 12, 2009 - 11:35am PT
'practice' using two single ropes as doubles could lead to death as the impact force would most likely exceed what your body/pro could withstand. You might as well fall onto a static rope.
 ec
Brandon Lampley

Mountain climber
Boulder, CO
Apr 12, 2009 - 01:17pm PT
ec, why?

You're taking a fall on the single rope just like you would otherwise. Black Canyon climbers sometimes climb with 9.2 singles using double rope technique.

Now using 9.8's like twins would be NUTS! and I assume that's what you mean.
Tomcat

Trad climber
Chatham N.H.
Apr 12, 2009 - 01:27pm PT
I have clipped both to a single piece before I knew better.This can increase the load on the piece and stress on your body.

I love doubles and have climbed that way for 25 years.

The test weight for the half rope fall is lighter than a single rope weight,but similar to what I weigh.
ec

climber
ca
Apr 12, 2009 - 01:36pm PT
Brandon,
Yes, that's what I meant and this does happen quite often (clipping both ropes to that same piece)...the ropes aren't always alternated; that's when they become one BIG rope.
 ec
tradmanclimbs

Ice climber
Pomfert VT
Apr 12, 2009 - 01:48pm PT
It is perfectly fine to clip both strands of 1/2 ropes to a single piece of gear provideing that the gear is bomber and that you do not have the ropes widely seperated before or after that piece. If you plan on sepertaing the ropes dramaticly it is best to keep them seperate for the whole pitch.

The idea that your ropes will melt in half if both 1/2 ropes are clipped to a single draw or that the fall will be dramaticly harder is just a myth. Falls on 2 strands of half rope running through the same piece of gear feel just as soft and cushy as falls on a single rope. That being said you would be nuts not to take advantage of splitting the ropes if the gear is at all delicate. Additionaly if you had the ropes split by a large distance and twisted them arround each other and clipped them both to the same biner you could create a situation where you see some sheath melting. You would have to try really hard to create that type of situation. I have tryed pretty hard over the years and never managed to melt any sheaths. As long as the rope runs relativly straight and are relativle close to each other you can fall all day on them and it won't matter one tiny little bit that both strands are clipped to the same draw. I have tested this very thouroghly. I believe it was called Hang doggin BITD ;)

Contrary to pop belief the load placed on a single piece of gear clipped to a single strand of 1/2 rope is greater than the same fall on a single rope. (single rope has more material to absorbe energy than 1/2 rope) Where the 1/2 ropes come into plaY with sketch geAR situations is when you place 2 pieces of gear at roughly the same height and clip each seperatly to its own rope. This I believe does increase your safety dramaticly.
Ghost

climber
A long way from where I started
Apr 12, 2009 - 01:59pm PT
Which leads me to questions about the diameter of half ropes and the logic or physics behind the ratings and fall safety of them

No big mystery here. Falling on just one half rope is fine – you just can’t do it as many times as you can on a single rope. “Fall rating” is a measure of how many major (almost factor 2) falls a rope will hold before it breaks. In the real world, you can fall all day on one of your half ropes. Rope technology has evolved along with everything else, and ropes have become lighter and their diameter has decreased for the same strength.

And rather than having to choose between single, double, and twin, you can now have it both ways. Petzl is selling a rope (in North America, at least) which it claims is acceptable for use as either, and although I don’t know for sure, I expect other companies are as well. Petzl’s Dragonfly is an 8.2 mm rope (availabe in both 60m and 70m lengths) rated for 6 UIAA falls. Don’t know what the fall rating is when used as a twin is – probably over 20. I’ve been using them for two seasons now and have nothing but good things to say about them. We generally use them as twins, but if a pitch wanders we split them as doubles.

As to belaying and rope management, that’s just a matter of practice. You’ll suffer through a few clusterfuks in the beginning, but it soon becomes second nature.

Biggest drawback is weight – two skinny ropes are heavier than one fat rope, and create more drag -- and at the end of a long pitch, you’ll feel the difference. On the other hand, cutting your rappels by half is pretty nice. And there’s always the fact that if one rope gets cut, you’re not gonna die (well, unless you're rappeling at the time).
tradmanclimbs

Ice climber
Pomfert VT
Apr 12, 2009 - 02:06pm PT
Gohst, All 1/2 ropes are rated as twins. Read the directions next time you buy a new set. They even have little pictures that show it is OK. what they don't want you to do is seperate the ropes by a several meters and then stuff them both back through the same biner as this could cause the ropes to rub against each other at diferent speeds durring a fall possibly causeing heat damage to the ropes.

The big deal with the new Petzle and Sterling ropes is that they are rated as Doubbles, Twins and SINGLE.
ec

climber
ca
Apr 12, 2009 - 02:22pm PT
tradmanclimbs,
...of course, I was referring to the first post of using two single ropes in this manner...much different results than using halfs or twins...

 ec
Ghost

climber
A long way from where I started
Apr 12, 2009 - 02:24pm PT
tradmanclimbs: My bad. That's what I meant to say (as evidenced by the six-fall rating).

I'll go back and correct my post.

Thanks
tradmanclimbs

Ice climber
Pomfert VT
Apr 12, 2009 - 02:55pm PT
No worries... Its good to bring this stuff up as there seems to be a bit of myth associated with the doubble rope system. One of the biggest myths is that single strand of 1/2 rope has a lower impact force than a normal single rope. According to Sterling ropes this is NOT TRUE. A single rope has a lower impact force than a 1/2 rope because there is more material in the single rope to absorb energy. The skinny 1/2 rope can not dissapate as much energy and therfore transfers that energy to the pro. belay device and falling climber.
Tomcat

Trad climber
Chatham N.H.
Apr 12, 2009 - 03:20pm PT
The impact forces are similar.The melting is a myth.You don't clip them both to one piece because it increases the impact force felt by both the climber and the piece.That's not a myth.
Ghost

climber
A long way from where I started
Apr 12, 2009 - 03:24pm PT
Falls on 2 strands of half rope running through the same piece of gear feel just as soft and cushy as falls on a single rope

As someone who took repeated 50-footers onto a pair of half ropes running as twins (I had to do it. My country's future was at stake. Just ask Tami) (Well, that and there was a fairly large paycheck involved) I can confirm that you're not gonna die if you do this. I would say it was higher impact than a similar fall on a fat single, but I didn't get broken in half or anything.
Tomcat

Trad climber
Chatham N.H.
Apr 12, 2009 - 03:37pm PT
Right,and since the impact force is higher,and the protection experiences twice the impact force,it's not adviseable to clip them both.Most of the time it's not an issue because people tend to use doubles,or halfs,as intended,and split them,so what actually takes place is imperfect equalization,even when you get wiggy and clip them both to that piece at the crux.
Francis

Trad climber
San Francisco
Topic Author's Reply - Apr 12, 2009 - 07:10pm PT
Cool all very informative, thank you

...I just went on to the Uiaa sight and consulted their drop tests... they have them in written form and in picture form.

I must have a thick scull because I still cannot figure out why they would drop a lighter weight for the half ropes. You know I am going to the source and email them and see if I can get an answer from the horses mouth.

I will let you all know if I find anything of interest.

tradmanclimbs

Ice climber
Pomfert VT
Apr 12, 2009 - 08:16pm PT
They use a lighter weight because if they used the heavier weight the rope would break too easily. I do a lot of logging with old climbing rope and skinny rope works but it breaks a LOT easier than fat rope.
Tami

Social climber
Vancouver, Canada
Apr 12, 2009 - 09:04pm PT
Just confirmin' David 's( Ghost ) note :-D
Pakdong

climber
Apr 12, 2009 - 09:21pm PT
not that I have any design to go try it....what would be the problem, other than edge resistence etc..., of climbing on a single half rope?...say a 8.2mm. Since doubles are set up to hold falls on a single stand at a time, why not just climb on a single stand? If the fall factor isn't high, is there much issue? I guess that leads to the question..what exactly is a "Single Rope"

WBraun.... what circumstances did you climb a single 8.8mm for all that time?
WBraun

climber
Apr 12, 2009 - 09:22pm PT
Light

Don't fall though ....
blahblah

Gym climber
Boulder
Apr 12, 2009 - 11:27pm PT
I believe a lower weight is used to test a double rope because you will never take a factor 2 fall on one double--if you're in a factor 2 fall situation, you will fall on both doubles. So singles need to be able to withstand a more severe fall, even though many falls in a double system will be caught on just one rope. Hopefully no one is taking many > factor 1 falls on any rope system.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 07:27am PT
Useing a 1/2 rope as a single has its benefits and risks. Lots of folks do it for alpine climbing where falls are rare and weight is a huge issue. Skinny ropes are NOT as durrable as fat ropes. If you use your 1/2 rope as a single you could toast the thing pretty quickly. Once the skinny rope breaks down the impact forces will be even higher than they allready are which is higher than a single rope anyways. Ropes do break and cut easier when they are broken down. Definatly NOT recomended in any situation where you would be doing a lot of falling and ANY lowering. lowering toasts your rope way fast .

Even the skinny expensive single ropes wear out quickly from lowering and projecting. For sport cragging where weight is not an issue its silly to use super light expensive skinny singles. A nice inexpensive 10.2 will last longer and work just fine. If you can't carry an extra 16 oz of rope up to Wiamea with your 12 draws then I suppose you will have to cough up the dough for that expensive skinny single.

Stuff yer pack with with 14 ice screws, 3 ice tools, crampons, medium rock rack, bunch of pins, 8 screamers and a bunch of slings, water,food , 3 pairs of gloves etc.etc,etc, and that expensive skinny single starts to make a lot of sense..

Its got to be kind of nuty to use super skinny rope on walls. fatter ropes are stronger, last longer and offer more cut resistance.
August West

Trad climber
Where the wind blows strange
Apr 13, 2009 - 08:53am PT
I'm not as concerned with the high impact forces as I am with the extra stretch you seem to get with skinnier ropes. Sierra granite is pretty bomber and when it isn't, you always have the option of addng a screamer. But a rope with extra stretch just gives you that more chance of hitting a ledge and wiping out an ankle.

The Beal Joker is rated for twin, half, or single. I've been pretty happy using it as single for light weight multiple pitch. When my partner and I simul-climb easy routes, we usually use a single 8.8mm.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 09:13am PT
When we climb ice as a threesom we often bring up the 2nd and 3rd simo on a single strand each of 8.1 ice floss. Amazing how far a Top rope fall is on a single 60 or 70m strand of 8.1!! Its pretty effin exciteing to be climbing way the heck off the deck WI5+ and have the guy just above you pop off and go wizzing by spinning out into space with all those sharp points windmilling arround!!! It also makes you concentrate your swings when you see that skinny little rope just inches away from your razor sharp ice tool!! My partner managed to allmost slice one of my 8.6mm ropes in half with a single swing. She was following on both ropes at the time so in no danger.
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 09:33am PT
Basically, it centers on why an 8ish rope is acceptable for half ropes. If and when you fall, are you still not falling on one rope, over a single edge? Does the physics of a fall change when you are using the Double rope technique? On your first piece, I am assuming it would be exactly the same as with a single rope as you have only one rope through one piece. If this is the case, then why would you be ok with having less of a fall rating?

I'll repeat a comment here: half ropes are strong enough to catch any fall. But they don't recover as well and so won't catch as many, not enough in general to get a single-rope rating.

Skinny double ropes make total sense for multi pitch ice climbing. they make no sense at all for single pitch climbing

I've done various single pitches with double ropes for many years---just did one yesterday, in fact. Marginal pro opportunities with chances to place trinkets more or less at the same level but spaced horizontally provides a scenario in which double ropes are a significant improvement over a single.

But I'm biased, because at this point I only own double ropes. Except for splitters, I think they are almost always a better bet. Their biggest drawback is weight, which is noticeable at the end of long pitches.

Its nice in theory to speculate that you can provide a better belay by keeping red short while the leader clips blue but in real life it dosen't work that way. A Real fall in that situation would most likly resuly in a fair ammount of rope slippage while the belayer juggles fingers trying to brake the right rope. In real life practice the belayer is more likly to feed the wrong rope and short you on the one you are trying to clip. then once you do get clipped you stand a decent chance of getting short roped on the other strand when you start climbing again.

I don't think one ought to include incompetent belaying as a drawback of double ropes. It is true that the belayer needs a few rudimentary skills not needed by the single-rope belayer. Here is a hint to those considering the use of doubles: the belayer needs to watch the ropes as much as the climber, and has to develop the very minor skill of sometimes taking in a rope with the non-braking hand.

if I have a line of bolts I will inform my belayer and treat the half ropes as twins and just clip em both to each draw. This is the easiest way to enshuer that you will get a decent belay and not get short roped or dropped.

Personally, I never do this, but again I climb with belayers who know their job. I simply never clip both ropes to the same piece. If there is a really mission-critical placement, I consider it worth two pieces, and one rope goes into each. As for bolts, I've found quite a few bolted pitches that are handled better with doubles, for example



'practice' using two single ropes as doubles could lead to death as the impact force would most likely exceed what your body/pro could withstand. You might as well fall onto a static rope.

Right,and since the impact force is higher,and the protection experiences twice the impact force,it's not adviseable to clip them both

The theoretical increase in load from double-clipping is 40% (more precisely, the square root of two times the load, not two times the load.) On some big falls, this 40% or so increase might exceed the 12 kn UIAA maximum, which is why not all double ropes are rated as twins.

All 1/2 ropes are rated as twins.

This is false, if by rating one means the UIAA rating (and there is no other meaning as far as I know).

One of the biggest myths is that single strand of 1/2 rope has a lower impact force than a normal single rope. According to Sterling ropes this is NOT TRUE. A single rope has a lower impact force than a 1/2 rope because there is more material in the single rope to absorb energy. The skinny 1/2 rope can not dissapate as much energy and therfore transfers that energy to the pro. belay device and falling climber.

My memory of Jim's comments is that the loads are essentially the same. However, if properly clipped doubles reduce the various angles at intermediate biners, then the cumulative effect of carabiner friction will be less and so more of the rope will be available for stopping the fall, possibly leading to lower peak loads at the top piece. In reality, I'd guess there is no significant difference.

I must have a thick scull because I still cannot figure out why they would drop a lighter weight for the half ropes.

Welcome to a large and thriving community of numbskulls. I've never heard a good explanation for the use of a 55 kg weight rather than an 80 kg weight.




Sherri

climber
WA
Apr 13, 2009 - 09:42am PT
I got a pair of the PMI Verglass twin/double(rated as both) ropes last year and I love 'em, especially for multipitches where I don't want to drag a tag line.

Still working out the finer points of using them as doubles, so I appreciate the diaglogue here.

Last time I climbed with them, I clipped both ropes to one piece using separate biners(attached to one sling) and for some reason they turned into an auto-brake. As I moved up, the two biners would seat into each other and the rope would get pinched between them. Arrrgh. Thankfully, I was near the end of the pitch and the misery was short-lived.

I'd hate to have this braking action happen at a crux or something. Should I be using TWO slings, one for each biner to keep them from joining up?
Ghost

climber
A long way from where I started
Apr 13, 2009 - 09:45am PT
I've never heard a good explanation for the use of a 55 kg weight rather than an 80 kg weight.

Cuz it's easier to hoist the lighter weight back up to the top of the tower?

That always struck me as odd, as well. There's one reasonable explanation upthread (from blahblah), but still...
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 09:51am PT
Last time I climbed with them, I clipped both ropes to one piece using separate biners(attached to one sling) and for some reason they turned into an auto-brake. As I moved up, the two biners would seat into each other and the rope would get pinched between them. Arrrgh. Thankfully, I was near the end of the pitch and the misery was short-lived.

I'd hate to have this braking action happen at a crux or something. Should I be using TWO slings, one for each biner to keep them from joining up?


As I said before, there is almost never any reason to clip both strands of a double rope to the same piece. If you don't trust a single strand, you probably shouldn't be using doubles to begin with. The only time I ever do this is if I have two seconds following, one one each rope, and they both need the ropes to run through some piece for directional reasons.

Clipping both ropes to the same piece is best done slings of different lengths, so the two rope-end biners can't interfere with each other.
Sherri

climber
WA
Apr 13, 2009 - 09:55am PT
Thanks, rgold. I'll try the different length slings next time. (Yes, I had clipped both to the same piece for directional because I had two climbers following. How'd you know?!)



tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 10:09am PT
Rgold, I have bought 4 sets of 1/2 ropes in the last decade, all diferent brands and diamaters and every single one of them had a little child proof pictuer guide on the furnished reading material that showed both ropes clipped throuigh the same biner as being safe.

Sorry but unless you are climbing very poorly protected and tricky gear placements it is darn silly to bring 400ft of rope to a 60ft crag..

So you don't own a single rope and you are so used to the doubble rope system that you think it is dead easy. That is totally fine, I didn't know how clunky my old purple Kolflachs were untill I strapped on my new Nepal Extreems either. A few years ago I did a Seneca, Gunks, Cannon, cathedral loop with Alex. We climed the doubbles for about 10 days straight except for the driveing rest days. When we got back to VT and hit up Deer Leap we broke out the single rope for some trad cragging. WOW! what a pleasuer to suddenly have such a simple light system... I am so used to doubbles that normaly I don't notice the extra work either but on this day due to how imersed we were in climbing evey day I really noticed the difference.

So you are so used to it you feel the belaying and rope management with doubbles is really easy. So do I. Thing is though, many of the rope slaves that I tourture don't seem to get it as smoothly. Been short roped with doubbles more times that I can remember! Also seen some pretty interesing rope salad ( cluster tangles) over the years.

Big fat straight line of bomber modern bolts, damn straight I will treat my doubbles as twins. faster, easier and the ropes will run better.


I can give you a damn good belay with doubbles but I can do it better in most cases with a single. Think of all those times when the leader is out of sight and you are guessing which rope he is clipping and which one to feed out while you are trying the reel the other one in... Think most sport pitches where clips are super fast and the game of feeding out and reeling in is so precise.

All that being said you won't catch me on a multi pitch climb without my doubbles ;)




blahblah

Gym climber
Boulder
Apr 13, 2009 - 10:21am PT
rgold: I love reading your stuff and know that, as a general matter, your knowledge of physics applied to climbing is much greater than mine.
But I challenge your below statement:
"I'll repeat a comment here: half ropes are strong enough to catch any fall."
Why do you think that a single half rope is strong enough to catch even a single factor 2 fall? A single half rope would never have to do that when used as intended, and they are not tested with a weight that is heavy as (most) climbers. To spell it completely, I think a single rope will catch a factor 2 fall because of the testing that is done on a single rope; the testing on a half rope is not equivalent and is done with a weight that is significantly less than an average adult male climber and very much less than the weight of a heavy climber loaded with gear.
This concept is related to my above post explaining that a single half rope is never subjected to factor 2 falls when used as intended--I don't think most of you are getting it, and if you think a single half rope is strong enough to replace a single rope re: factor 2 falls, maybe you're right, but unless you've done your own testing you're just guessing.
Edit: I saw the response from rgold that (one) double rope can withstand several UIAA single rope drop tests. If so, that does address my concern.
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 10:24am PT
Rgold, I have bought 4 sets of 1/2 ropes in the last decade, all diferent brands and diamaters and every single one of them had a little child proof pictuer guide on the furnished reading material that showed both ropes clipped throuigh the same biner as being safe.

And most, if not all, of those ropes were not rated as singles because, when both clipped, the load in a UIAA test fall with an 80 kg weight exceeds 12 kn.

Sorry but unless you are climbing very poorly protected and tricky gear placements it is darn silly to bring 400ft of rope to a 60ft crag..

This will be news the the Brits, who will have to be notified that they have been darn silly for many years now. As for me, especially in my dotage, "darn silly" is probably on the gentle side of the possible criticisms and I thank you for your restraint.

Think of all those times when the leader is out of sight and you are guessing which rope he is clipping and which one to feed out while you are trying the reel the other one in...

As I suggested, (and as I'm sure you know) the trick is to look at the ropes in front of you, not at the leader, whether or not the leader is in or out of sight. This makes it simple to handle the ropes properly and with appropriate speed. Sounds to me like you need to upgrade to a better brand of belay slave.

Oh yeah, pedant that I am, I tried to ignore this for a while but my character defect has finally won out..."double" and "doubles" only have one "b."
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 10:25am PT
I have NO real scientific data as well but from a logging standpoint 1/2 rope breaks a whole crapload easier than single rope. You can still pull a pretty darn bik log out of the woods with 8.6mm rope but if it snaggs on something it breaks quick. Same situation with 10.6mm and you have to really mosh the truck to break the rope.
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 10:29am PT
The UIAA rating for half-rope logging is only for non-snagging applications.
ionlyski

Trad climber
Kalispell, Montana
Apr 13, 2009 - 10:34am PT
I don't think the advantage of double length rappels when using doubles or twins should be stated, when making the comparison between single vs double because most of the time what we're really comparing is "single with tagline" vs "double" techniques. The text books always highlight this advantage for doubles, as if you weren't planning to haul or pack a second skinny line with your single system.

RGold, I've paid attention to your contributions on this subject before and am trying hard to become better at belaying with doubles but I still can't look you in the eye and tell you that you won't fall farther. If I'm honest I know there are times too, as I'm paying out with one, whilst taking in with the other, that I wouldn't want you to fall at that exact moment. In general, if you're leading on doubles while I'm belaying you, you're going to have a bit more slack in the system than with singles. I realize you wouldn't climb with me anyway but I'm just being honest.

Arne

rwedgee

Ice climber
canyon country,CA
Apr 13, 2009 - 10:35am PT
In the photo you should have used slings, not draws to route the rope. I'd rather carry more slings than another rope any day.
Used the Mammut 7.7mm clipped as one, as designed, for a while for long ice routes for the advantage of long raps. They were just too skinny to handle(mainly tying/untying in at the anchor) with gloves on. Even a clove hitch was hard to get out. They were super stretchy with low impact as you would want for ice, horrible to rap on. It was like a bungee cord. No good in the Sierras as with that much rope you will get them stuck or pull rocks down rapping.
Even clipped as on one they were never equally tight in a fall due to whatever, if not simply the way they're positioned in the belayers glove.
ionlyski

Trad climber
Kalispell, Montana
Apr 13, 2009 - 10:40am PT
Hi there Tradman,
Say, where are you logging with ropes?
Arne
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 10:50am PT
Well then, I guess we have established that the Brits are silly:) They rock climb in the rain, drink too much while climbing, make WAY too much fuss over bolts and aparenty need 120m of rope to get up a 20m boulder;)

Wandering line of bolts like in your photo and sandstone to boot, of course I would seperate the ropes and use them as doubles.

There are Many situations where doubbles are safer and more practicle, especialy for protecting the 2nd. There are also Many situations where singles are more practicle, pleanty safe and easier to use. There are even situations where singles are safer.

I do All my multi pitch free climbing with doubbles. I do most of my single pitch ice climbing with doubbles though I do sometimes use a single 1/2 rope for single pitch ice or light alpine ice.

I do all my sport climbing and 1/2 pitch trad cragging with single ropes. I try to do all my Aid climbing with a fat single rope and tag line. I have done a few Aid pitches with the skinny ropes but don't really like it.

tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 10:55am PT
Arne, I cut all my own firewood and lug it out with an 86 F150. Got lots of old climbing rope so I use it for whatever. It is not ideal for towing things because of the streach but it gets most jobs done and its basicly free. It is also good for your climbing head to see how strong that stuff really is.
dirtineye

Trad climber
the south
Apr 13, 2009 - 10:57am PT
There is one problem that does not get mentioned much in these threads, and that is the intended use (by the manufacturere) of the doubles. IF the main purpose of the set is ice snow etc, then fine, skinny rubberbands are wonderful, like the pmi verglas.

BUT, take hose verglas on edgedy sandstone or other abraidy rock, and you can get into trouble. ( how you like my new vocab there Rgold? haha if two 'b's in double bothered you I hate to think what's going on in yer noggin right now!)

I'm speaking from the very real experience of seeing (after about 15-20 falls in the same spot) the verglas becoming severely damaged.


So, whatever you think about doubles, you really need to consider the kind of climbing they are inteneded for before just getting on any set on any surface.

I personally, (if I were going to get well adn be climbing that is) would be looking for some thin but not too thin (8.1 is a bit thin, 8.5 maybe a tad thick, hell I just wouldn't want to go outside those ranges though, for various reasons) would want to KNOW that my doubles were designed for ROCK, cause I don't do ice.

that said, I love doubles. they have so many advantages over a single it's just no argument for me. I did climb on mammut genesis 8.5, loved em, loved the catch, felt they were not hard to belay with, but they could use a little tougher sheath for rock. but then I think they are not rated as best for rock, by mammut themselves. One other thing I'd be after is uh, well I forgot, damned drugs. Oh well, someone will get it. Oh yeah, twin/double rating! I think that's cool, cause nto every pitch is calling for doubles, so teh ability to clip (ALL PITCH LONG mind you) as either doubles or twins (if yo udon;t like my terminology, too bad, twin means clipped together, double means seperately to me).

that's my bit on Doubles, except to add that beware if you are doing this for the first time: it's not the leader who has the most trouble, it's the belayer. so learn to belay with em and pay attention, cause that get's a lot more complicated than single ropes even thought about.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 11:03am PT
Arne, I think your honest assesment of your belaying skills with doubles is dead on for 95% of the people useing the system. I know that Myself i can give a really good belay with doubbles but still get caught in akward situations from time to time that simply would not happen with a single rope system.

My beef with the tag line system is simply if I have to lug it I may as well use it for climbing. Additionaly 2 skinnys are going to be lighter than one skinny and one fatty.
ionlyski

Trad climber
Kalispell, Montana
Apr 13, 2009 - 11:16am PT
My beef with the tag line system is simply if I have to lug it I may as well use it for climbing. Additionaly 2 skinnys are going to be lighter than one skinny and one fatty.

Correct. But the length of the rappel is the same. It's always touted as an advantage of using doubles, as if we were asking, hmmm, should I choose a set of doubles or one single rope?

Arne
Brandon Lampley

Mountain climber
Boulder, CO
Apr 13, 2009 - 11:34am PT
All sorts of technical speculation going on here. One thing thougn needs to be clear. ALL double ropes on the market today are NOT RATED AS TWINS. Some may not be because they didn't go through the twin certification process. But, some, like the 9.0 doubles from some manufacturers, have been through the twin tests, and FAILED because of high impact forces.

Clipping both doubles to a single piece after spearating them early in the pitch... This is a different scenario force wise than clipping them like twins from the get go.

Clipping your fat doubles like twins on a bolted pitch, no big deal. Bolts are strong. Clipping your fat doubles like twins on a straight tips crack pitch with rps and micro cams, not for me.
dirtineye

Trad climber
the south
Apr 13, 2009 - 11:53am PT
well I hope yo uare not referring to my post, because I did not mention clipping unrated for both as both. That could be bad, of course.


Also for the tech side, Rgold did good explanation of clipping two NOT creating the same thing as just doubling the effect of clipping one. Maybe he will post it again for your amusement.
PP

Trad climber
SF,CA
Apr 13, 2009 - 11:54am PT
I love double ropes it gives you alot of creative options when weird things happen. They worked really great on inverted stair case on Fairview.
Brandon Lampley

Mountain climber
Boulder, CO
Apr 13, 2009 - 12:07pm PT
No dirt, tradmanclimbs is sharing lots of cool practical observations, but also incorrect factual information.

Rgold has been clearing things up though.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 12:24pm PT
yer right , Some of what I say is probobly against the rules but in the practicle sense of how it actually works I feel that I am dead on most of the time. Why is it not safe to clip both of my 1/2 ropes to a single biner if the little pictuer on the card that comes with the ropes shows a pitcuer of both ropes running straight clipped to the same biner and a happy face. No skull and crossbones like the pictuer with the ropes all twisted to crap, seperated and then stuffed back into the biner. Regardless of what the pictuer says I seem to recall my partner clipping the bolts on Total Recall just like she was useing twins, then she greased off for a 20 footer. Sterling 8.8 maratrhons. resulting catch was light as a feather. Didn't yank me any more or less than catching simeler falls on single rope. Real life ain't a theory ;)
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 12:31pm PT
PP I like the system otherwise I wouldn't use it. I am just willing to concede that the single rope system has its merits as well. There must be a reason that the doubble rope system never really dominated the Yosemite scene where as in the east, doubble ropes have had a pretty strong showing.
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 12:32pm PT
Blah: In the last few years, I've read posts of several UIAA single rope drop tests applied to one of a pair of half ropes. Not quite factor 2, but close enough at factor 1.78. 80 kg weight, not 55 kg. My memory is that you get about three such drops before the half rope breaks, which is not enough to earn a UIAA single rope certification.

Edit: Half ropes do not break on the first UIAA single-rope drop test. Consider this in view of

Number of Rope Failures amongst German and Austrian Mountaineers and Climbers since 1968

by Pit Schubert

Because the fall on the Dodero-test-machine is much stronger than in practice, it is not possible (in practice no rigid falling mass, no strictly static belay) for a rope which holds one fall on the Dodero-test-machine to break in practice - not in knot, not in the running belay, not at the belaying device, only when the rope is loaded over a sharp edge, normally a rock edge. And this happens as the table shows very, very seldom.



tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 12:35pm PT
I posted that up thread with the unscientific disclaimer. they break!
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 12:48pm PT
As for the comparison with the tag line, I'm at a loss to see much of an advantage. The weight is about the same I think. The tag line could be used to haul up gear (its original use), but that seems unnecessary except on wall climbs. Seems like twins would make much more sense if you don't want the hassles of alternate clipping.

The main drawback of the tag line rappel system and, to a lesser but not insignificant extent, twins, is that most people set it up to pull the tag line (to prevent the uneven running that is typical if the set-up is to pull the main rope). This means that if the rappel rope hangs up after it releases from the anchor, the party will be left with only the tag line to try to extricate themselves, rather than with a rope that can be lead on with some confidence and rappelled on without high anxiety and extremely low friction.

As someone who had exactly this type of rappel snag happen a year ago, I wouldn't go anywhere even slightly remote with a single rope and a tag line.
rhyang

climber
SJC
Apr 13, 2009 - 01:14pm PT
So here's a (barely-related) question: does anyone have Edelweiss Dynamic 8.3's ? As I understand it, they are now rated as half ropes and twin ropes. But as of several years ago, they were only rated as half ropes. As far as I can tell, the older ones have the same impact force (5.8 kN as halfs), elongation, etc. as the current model.

Does anyone know if the current edelweiss dynamic 8.3's are simply the same ropes as before, just with new testing / marketing / labels as the previous model ?

I also have a set of pmi verglas 8.1's, but have only used them for ice climbing. They are also getting a bit old (bought in 2005), though they haven't seen much use. Wondering if I should just retire them in 2010 .. I can't see myself tr'ing on them.
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 01:26pm PT
rhyang, I don't know whether the ropes are different or not, presumably they have to be. What would have to have changed is not any of the stats you mentioned, but rather how many UIAA drops with an 80 kg weight are held. I think the standard is 5 drops. The earlier versions of the rope couldn't hold 5 drops and the newer, presumably improved versions can. Whether this is due to a change in construction or in, say, heat-treating I do not know.

Edit: My bad. I didn't read your statement carefully enough and thought you were referring to the ropes passing a single-rope test when used individually.
Jim E

climber
away
Apr 13, 2009 - 01:31pm PT
Half ropes are drop tested with 55kg on a single strand. Twins are tested with 80kg on two strands.

The addition of the 'twin' rating is probably due to the manufacturer deciding to have the rope tested as both. It's the 'in' thing.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 01:40pm PT
Jim. so glad you showed up! Didn't you tell us awhile back that a single rope has a lower impact force than a 1/2 rope? Also remember something about elongation being not what most folks assume?
Jim E

climber
away
Apr 13, 2009 - 01:43pm PT
I posted something, somewhere, about impact forces on half ropes being tested with 80kg. Will have to look around for it. Might be over at RC.com.



edit: here it is
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=1394069;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;page=unread#unread
rgold

Trad climber
Poughkeepsie, NY
Apr 13, 2009 - 01:50pm PT
Jim, it is here:

http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=1534536#1534536

This is a direct link to your post rather than a general link to the thread that you posted.
tradmanclimbs

Ice climber
Pomfert VT
Apr 13, 2009 - 01:55pm PT
Rgold, I agree with you 100% on the tag line system. The times that I have used that system, IC and aid climbing etc. I use one of my 1/2 ropes as the tagline. I know i can lead on it and use it for a rescue. The 1st time I went out west RR, Zion, Etc. in 86 we led on a 50m 11mm and we had a 50m X11mm tag line. THAT was HEAVY setup! We were cutting edge modern at the time as those 11mm ropes were the latest rage ;) Back home in the east I usually did multi pitch with a single 11mm X 50m, no tag line and just hoped that nothing went wrong. We allmost never rapped... We allmost allways hiked off the top.
murf02

climber
NYC
Apr 13, 2009 - 01:55pm PT
" As long as the rope runs relativly straight and are relativle close to each other you can fall all day on them and it won't matter one tiny little bit that both strands are clipped to the same draw. I have tested this very thouroghly."

This suggest that clipping both double ropes to the first piece off the belay would not only reduce the factor 2 on a single rope but friction and melt shouldn't be an issue as well?
rhyang

climber
SJC
Apr 13, 2009 - 02:03pm PT
Wow, thanks for that link. Totally debunks what I had believed about doubles and impact force =:-O

The dynamic 8.3's seem to be rated at 10 UIAA falls for both the new and old models. With the older (non-twin-certified) model, it sounds as though using them as twins on bolts is probably ok, but maybe not such a great idea if on trad pro ..
jbar

Social climber
urasymptote
Apr 13, 2009 - 07:32pm PT
rhyang - Not to be judged but I have an old 8.3 I bought to cut down on weight for an alpine trip I took years ago. Ended up leading a few sport routes and top roping a couple of climbs because it was all I had. Didn't take any extreme falls on it but it handled the use fine. Best I can remember it was rated at 7 falls so it may be different than the new one.
Dr.Sprock

Boulder climber
Sprocketville
Apr 13, 2009 - 08:38pm PT
here is a real simple math approach to the falling aspects,
might get you in the ball park.

if the lines twist and form a "braid" while falling, the straight fiber count approach goes out the window as the sheaths will bind at some point, right?

Mar'

Trad climber
Tustin
Apr 13, 2009 - 10:15pm PT
I took a hundred footer on overhanging ice on Papa Bear when it turned into a slush-fest and I got spit out on a pair of skinnies in the olden-days. I'd clipped into separate biners on separate single-length slings hitched to a single screw. The screw was in a solid hummock of blue ice. It was pointing UP at about 80 degrees, 40' below my high point. I never touched anything on the way down and the take-up of energy was a very curious experience. Gentle, yet dynamic. The ropes MUST have stretched at LEAST twenty feet. Overall, that fall was a very pleasant event. The ropes stretching then rebounding took a long time~ and so did the fall!

It was the rebound that kicked my ass! That was a LOT of force and fortunately I hit the wall squarely and perfectly flat against my back during my violent UPWARD vector. We didn't always wear helmets in those days, but Bruce Nyberg at the Rock+Ice had set me up with a slightly over-size hand-laid "Joe Brown" fiberglass shelled motorcycle style foam-laminate job. He said to get it over-size so with a ski-hat on the helmet wouldn't just sit on top of my head like a cherry on an ice-cream sundae.

Well, my head was part of my body in those days and the impact completely killed that helmet. The shell was not "broken", but it was permanently toast with a nasty fracture along the lower back portion and the inner dense foam liner was badly deformed.

When I stopped bouncing I was very strangely angry and yelled to be lowered! Bob Horton, who had just saved my life, kneeled in the snow with the shaft of one of my tools buried spike down about five feet from him. He'd unclipped from the anchor and jumped/run/fallen down the slope to take up the slack and I was dangling about 20' shy of the base of the ice.

When I got down I told Bob that it was his turn to lead!

I love double-roping and all it's advantages. I've never used one in Yosemite or Jtree though. For sure on some Tahquitz routes and in the mountains. I'd use a pair of 8s or on diceyer stuff, a single rated 9 with an 8.5.

adam d

climber
CA
Apr 13, 2009 - 11:11pm PT
Yikes Mar!

I've had a couple sets of Mammut Genesis 8.5 double ropes...they're great. I've done some simul mountain routes with one of 'em, a few times with each person carrying coils and ~30m between us, sometimes just doubled over and simuling on 2 strands of 30m of 8.5. It's nice to be light but still be able to rap 60m. After logging plenty of air time, especially in the Gunks on these ropes in a double setup, I've got a lot of faith in them. Getting caught by two ropes, each on some small piece of gear really increases my "go for it" above little pro. If the edges aren't too much of a concern and you aren't really dogging it, I find these doubles to be a great option for climbing in a party of 3, though on harder/sharper/more serious routes I revert back to leading on two singles or caterpillar style with two thicker ropes.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 05:51am PT
The biggest advantage pro wise with the doubbles is the ability to place 2 seperate pieces of pro and have each piece clipped to a different rope. No idea what the actual impact forces on each piece are in that scenario but they must be lighter than anything you could conjer up with a single rope.

Interesting to note that the monster ice whipper on a screw up post was both ropes clipped to the same screw. Everything worked out just fine. Every time these threads pop up someone proclaims that clipping both ropes to one piece will kill you. Read the directions when you buy the damn rope and please stop telling me that I will die if I follow them ;)
Tomcat

Trad climber
Chatham N.H.
Apr 14, 2009 - 05:57am PT
We use our doubles for all trad routes,unless we plan to toprope after,which happens about once a year.Tradchick learned to belay on doubles and is a master.No reason you shouldn't be able to manage someone clipping over their head while maintaining on the other line.

Tag lines,by comparison,seem moronic.10 mm plus 7 mm is 17 mm,but you have only one advantage here,rapping.8.5+8.5=17,but opens door to all half rope advantages,safer clips,wandering pro,double pro at crux,protection in event of rope getting cut,don't need a cordelette(gasp!),or PAS,can recover stuck rope,protect the second.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 06:07am PT
I totally agree that the double system is great for multi pitch and long single pitch. I merly contend that there are climbing scenarios where the single rope system is great as well.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 07:32am PT
Same trip but 2 different scenarios. I really wish we had a fat single for the Aid pitch.


I ended up climbing this pitch instead of jugging it but the ropes still got buggered up a bit on the sharp drilled angles.


May be hard to see in the small photo but that is 2 9mm Mammuts running through each draw.
August West

Trad climber
Where the wind blows strange
Apr 14, 2009 - 09:19am PT
So all you guys that are belay aces with double ropes, what is your strategy at stance/hanging belays? My partner and I climbed with doubles early in our career, quit, and then tried again for a season or two (much later and much more rope proficient). The place where we really got slowed down is when the leader is at a stance belay and the second is coming up moderate terrain. With a single, the second could run up the pitch arriving out of breath (we often lead in blocks). With doubles, the rope management made the second climb at a leisurely place. We've tried: stuffing both ropes into one bag, no tangles but extremely slow; and flaking over a sling, which is quicker initially, but eventually you lose all of your time savings when the inevitable tangles arrive. I know, some will claim we need better rope management skills, but when climbing with a single, if a rope picks up some pig's tail cork screw, not a big deal. With doubles, what do you do? Throw the ropes out? And doubles make the leading in blocks problematic. As a leisurely, fun, multi-pitch style, doubles worked fine for us and no real complaints. But for the hurry-up style, a lot of frustrations.

Unless the rap line does not come back down the climb, we usually just take a single skinny 70m (no tag) figuring we can make most raps and leave a sling or stopper if not.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 09:47am PT
August, your style is faster, simpler and easier. Us old fuddy duddys just like our security blankets. That extra rope gives us lots of options to make the climbing safer and retrete easier;)
rgold

Trad climber
Poughkeepsie, NY
Apr 14, 2009 - 10:53am PT
August, I'm not really a good person to reply because I'm not a big fan of the hurry-up style. Still, the issues you raise apply to those who prefer to travel at a more (ahem) stately pace.

If leading in blocks (something I never do), I think there are two solutions, neither of them fast: either switch ends of the rope or restack the pile. Trying to turn it over and have it run will be a disaster enough of the time so that it isn't worth it.

For long multipitch routes without good ledges for piling the rope, I have found the Metolius rope hook to be a superb rope organizer. While belaying, you can throw coils over the hook as fast as you can take in rope. The coils do not have to be specially sized as they do when flaking over a sling, the tie-in, or your feet, because with the hook you do not have to pull the coils out. Instead, you simply pick up the rope at the top of the coil and drop it---it automatically frees itself of any loops it might have wanted to capture had it been pulled. Absolutely no tangles and as fast to load and unload as you can handle the rope.

A little gimmicky but worth the time savings and handling ease in my opinion.
Ghost

climber
A long way from where I started
Apr 14, 2009 - 11:11am PT
Trying to turn it over and have it run will be a disaster enough of the time so that it isn't worth it.

We do that (flipping the ropes over from one daisy to the other) a fair bit, and rarely have any problems. However, we mostly move at fairly low speed, and have the time to sort out the rare tangles that do occur.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 11:18am PT
I either restack or retie. restack is best. It gets you warmed up again and the blood back in your fingers.
dustonian

climber
Apr 14, 2009 - 12:58pm PT
Two ropes are retarded unless you're wandering all over the place or climbing sharp crap or ice. Who wants to drag up a collective 17+mm of rope??!??! And then when you fall one little skinny bullshit rope catches you anyway.... fukkin genius!
Tomcat

Trad climber
Chatham N.H.
Apr 14, 2009 - 01:26pm PT
Guess that depends on how you are getting down eh?

We usually restack.Key to success is not getting the pigstails to begin with.Don't tie the ropes together when you rappel,tie separate stopper knots,and don't let the lower one run over the upper one when you rappel,look some time and you can see the troubles forming.On a steep route we'll often cut them loose if it's knott windy.
rgold

Trad climber
Poughkeepsie, NY
Apr 14, 2009 - 06:11pm PT
We do that (flipping the ropes over from one daisy to the other) a fair bit, and rarely have any problems. However, we mostly move at fairly low speed, and have the time to sort out the rare tangles that do occur.

I've been climbing for more than fifty years and I think I need rope stacking lessons. When I flip one of those piles, I get the mother of all Gordian knots half the time.

While I'm at it, would someone like to teach me how to throw rappel ropes? No matter what method I try, I seem to be able to magically create knots and tangles, not to mention snagging every nubbin, flake, crystal, and twig in the universe.
tradmanclimbs

Ice climber
Pomfert VT
Apr 14, 2009 - 08:14pm PT
Ain't that the truth!, i can't even flip over a stack of single rope without makeing salad and TWIGS! I effin hate twigs and sticks. They get in the middle of a pile of rappel rope and make a frickin ceasar salad out of the damn thing....... :)
Ghost

climber
A long way from where I started
Apr 15, 2009 - 06:44am PT
When I flip one of those piles, I get the mother of all Gordian knots half the time.

Rich, I'm certainly not advocating it, or saying "I do it all the time" -- only that in the last couple of years we've started to do it occasionally (against my instincts and over my protests) and it's actually been working out. There is sometimes some minor tangling, but nothing that can't be sorted out if one doesn't panic. I'd never do it if I was in a hurry though. That would be just begging for a disaster.

As to throwing rappel ropes, yeah, that's a whole other problem. Chickenheads, flakes, cracks, knobs, bushes -- none of which even existed on the way up -- seem to materialize for the sole purpose of snagging rappel ropes. And the wind, which has been calm for the whole day, suddenly starts to gust...

My personal bugaboo though, is the twigs that magically appear underneath my rope when I lay it on the ground at the foot of a climb. Bare ground, not a twig in sight. But start feeding out the rope and it's an instant snag-fest.
Ghost

climber
A long way from where I started
Apr 15, 2009 - 06:54am PT
Okay, here's a double-rope horror story. I told it on the "Squamish in the 70s" thread but it fits perfectly here:

Carl Austrom was a pretty good all-round climber at the time, but he did have momentary lapses of common sense, as hilariously (for me) shown on the second pitch of Zebra-to-Zion at Smith. Which isn't really in Squamish, but it's close.

I did a lot of my climbing on double ropes, and Carl decided he wanted to try it on Z-to-Z. It's a four-pitch classic on the main wall, which I'd climbed in the past and he wanted to lead. The first pitch traverses a long way rightward on big pockets, and as Carl moved across he placed gear -- some high, some low, wherever a pocket of the right size appeared. But he somehow hadn't quite got the concept of "one rope for placements on one side, one rope for placements on the other side" Or, in this case one for high, one for low. He just cruised along randomly clipping whichever rope he felt like clipping, crossing them over and under one another. When he got to the corner and headed up instead of sideways, he continued this pattern -- sewing up the crack and crossing the ropes crazily. He fought the increasing drag to the belay, and I followed.

By the time I got to his belay, the ropes were half piled and half hanging in the biggest snarled-up clusterfuk you can imagine. He, of course, was about to rocket off up the next pitch as soon as I clipped in.

"Carl, we gotta untangle this mess. It's gonna jam up something fierce."

"It'll be fine. It'll untangle as you feed it out."

"No, it won't. You'll get a little ways up and it's just going to be so tangled it'll never go through my belay device."

"Who cares? You can untangle it. It'll be fine."

And off he went. Got about 30 ft up, with me frantically trying to untangle and belay at the same time. He hit the 10b finger crux just as the rope snarl hit my device in an totally untangleable way.

"Slack!"

"Ain't no slack."

"SLACK!! SSLLAACKKKKK!!!"

"Not happening."

"AAAARRRRGGGGGHHHHH."

So he hung there off 10b finger jams, cursing and completely forgetting that dropping in a nut and sitting back on it would probably be the sensible thing to do, while I tied him off, untied myself, spent over ten minutes undoing the mess he'd created with his clipping, stacked things neatly, retied, put him back on belay, and told him he could now have some slack.

Funniest damn thing I ever saw while belaying. He had sewed the crack up below him, so he was in no danger, but he was so freaked by the immovable rope that he just clamped down on the rock and hung there, right on the crux, instead of taking a break.
tradmanclimbs

Ice climber
Pomfert VT
Apr 15, 2009 - 07:51am PT
Le Promonade IV WI 5+ 12-21-05 shortest day of the year.
Cold, single digits, getting dark, party of 3. Alden was doing all the heavy lifting. Bob and I followed the freestanding pillar one at a time so the ropes got pullled up seperatly. We thought we had them stacked properly for ther last pitch but as Alden is raceing up the last pitch of uber steep 5+ as darkness approaches the ropes become hopelessly tangled. Bob and I are working as fast as we can to get them unsnarled and stuffed through the belay device. Frozen numb gloved fingers and one of the worst rope salads ever. Neither one of us was attempting to belay, we both were useing both hands to try and untangle the mess and stuff it through the device.. Somehow we pulled it off.

I contend that every climber who pronounces themselfs an expert at flawless doubble rope belaying and rope management has more skeletons in their closet than they care to admit ;)
rgold

Trad climber
Poughkeepsie, NY
Apr 15, 2009 - 11:51am PT
I contend that every climber who pronounces themselfs an expert at flawless doubble rope belaying and rope management has more skeletons in their closet than they care to admit ;)

Well, that leaves me off the hook 'cause I sure don't claim to be no flawless expert.

I made a mess fairly recently (about a year ago), but it occurred because, in spite of my better judgement and in full knowledge of my inabilities, I tried turning over a stack. Had to untie ends to get the mess untangled.

I've had a few bad experiences with ropes flaked over the tie-in, when the action has made it impossible---for me---to properly graduate the loops while bringing up the second. Fact is, more often than not I can't get the loops properly graduated. However, I believe these flaking failures would also have resulted in analogous fusterclucks with a single rope.

The rope hooks seem to solve all the problems I've experienced, but I only bring them along on long routes.
Mar'

Trad climber
Fanta Se
Apr 15, 2009 - 12:39pm PT
When climbing in blocks, August— plan on swapping rope-ends, so you don't have to touch the you-know-what! It's a pretty quick way to go, if it's part of your routine. I don't know that it's not conventional— you're probably using a daisy anyway at change-overs.
tolman_paul

Trad climber
Anchorage, AK
Apr 15, 2009 - 02:48pm PT
No rope or roped system is full proof. Which is why that old dictate about the leader not falling is a good one to follow.

Single ropes have their place. They are the simplest and lightest way to belay. The down side is on wandering pitches they present additional rope drag, if you fall while clipping you face a longer fall then if you clip one rope at a time with a dual rope system, and they have no backup should they be cut over an edge. Oh, and should you need to do full pitch rappels, you need a means of pulling the rope.

Two rope systems have their place, and pitfalls as well attested in this thread.

I use both single and 1/2 ropes. They have their place. For the majority of the climbing I've done, a single rope has had more plusses than minuses. On routes with the potential or requirement for full length raps I've done them both with 1/2 ropes and with a single and a 1/2 rope as the pull line.

If you need to carry two ropes, give strong consideration to the second rope being capable of more than just retrieving your main line. Using a 10, or 9 something single and a 1/2 rope of whatever diameter as the pull/backup line makes alot more sense than a single and an overweight shoestring. The 1/2 rope isn't that much heavier than a static 7 or 8, but it is 10 times more useful should something happen to your main line.

I can understand why bachar solos, start at the bottom, don't fall, walk off the top. Pretty simple system.
August West

Trad climber
Where the wind blows strange
Apr 15, 2009 - 03:33pm PT
"When climbing in blocks, August— plan on swapping rope-ends, so you don't have to touch the you-know-what! It's a pretty quick way to go, if it's part of your routine. I don't know that it's not conventional— you're probably using a daisy anyway at change-overs."

For a single rope, we have gotten to the point where we can flake the rope on a sling and "flip" (or "roll" might be a better term) the rope over quickly without problems. Since I have had problems flaking double ropes over a sling, I wouldn't try this with doubles.

In the past, I have swapped rope-ends for leading in blocks (both untieing-re-tieing and, alternatively, tieing a double 8 on a bite and clipping a locking biner between harness and rope). But doubles are slower. And it brings up another issue with doubles: when the leader starts out, both strands appear to be parallel and separate. However, by the time the second gets up to the anchor, you find that the strands are twisted over each other (and this helps add kinks to the ropes). One would think that untieing and carefully re-tieing would solve this problem (at least for the next pitch), but it never quite seems to work out that way. (And yes, starting off the ground, I pull both ropes, all 60m, all the way through my atc device, to make sure they are parallel, before tieing in.)

I'm pretty happy with my 70m single or, occasionally, leading on a 60m and tagging a 8.8mm for rap line/emergency lead line. So I'm not very seriously considering going back to doubles. But every time somebody sings the praises of doubles (especially to climbers who haven't used them), I'm always like, "wait a minute..." And I am curious about those that have stuck with them long term (since most who try them seem to be like me in that they eventually go back to singles).

But each to their own. Not trying to talk anybody out of them, just wondering how some climbers claim to be happy with them...
tradmanclimbs

Ice climber
Pomfert VT
Apr 15, 2009 - 04:42pm PT
Im just a big chicken. Doubbles are more work but they offer more security.
Mar'

Trad climber
Fanta Se
Apr 15, 2009 - 11:38pm PT
Yeah— and it's a bad habit too! I've also been a 30 year addict of the 1-1/2 fisherman's bend to tie-in. Small, fast, neat and easy to get in and out of. I have a funny way of dealing with crossed lines— I do pirouettes as needed as soon as I start off— sometimes it works, sometimes it doesn't. It's just part of romancing the stone.

Whether you prefer doubles or not, it's best to have mastery of any technique that suites the occasion, regardless of general preferences. It really depends on your objective. I'm happy to use my single whenever it's appropriate, but my "desert island" rope would be a double.

I know people like Werner (including me), who've been leading on single-strand 1/2 ropes since the mid 80s. When you have no doubts, there is no right or wrong, no better or worse way.
Osmo

Trad climber
Calgary, Alberta
Apr 16, 2009 - 03:32pm PT
To tradmanclimbs re Apr. 12 1:48 and 2:55pm: sorry, I haven't seen what Sterling Ropes have to say, but THEY HAVE IT WRONG IF they say what you say they do, as they can't change basic physics. Given a specific fall situation, what happens is that the climber has a fixed amount of ENERGY when he hits the rope--whether he falls on a thin rope or a thick rope, each rope absorbs all that energy if it stops the fall: if it's a thin rope, it has a low K-factor (spring constant) and will stretch farther to absorb that energy--the impact (or peak) force occurs at his lowest point and the energy is the area under the rope-tension vs. stretch-length curve; but if it's a thick rope, it has a higher K-factor and will not need to stretch as far to absorb the same energy of the falling climber, because the rope tensions are higher at each stretch length. Again the impact force is the tension in the rope where the climber stops falling, and will definitely be higher in the thick rope than in the thin rope (same materials, etc. of course) because the forces must be higher since the distance is shorter; the common belief is common because it's correct. It's the same principle as used in all 'cushioning' materials, like crash pads: reduce the impact force by increasing the impact distance, by using a soft material, for example a thin (stretchy) rope. Osmo.
tolman_paul

Trad climber
Anchorage, AK
Apr 16, 2009 - 03:37pm PT
It's not quite as simple as saying the rope is a spring. Some of the energy is converted to heat, from the rope fibers running over themselves internal to the rope, and the rope funning across biners, rock etc.

The little ropes break after fewer falls (when used as singles) because there is less rope to take the heat, and more heat damage per fall.
tradmanclimbs

Ice climber
Pomfert VT
Apr 16, 2009 - 04:56pm PT
Osmo, jim from sterling did the drop tests on 1/2 ropes with the full 80kg weight and the numbers are right arround what you would expect for a single rope. That is for the 1st drop only. I understand that the numbers go up dramaticly after the 1st drop but jim did not post that info. Those super low impact forces that they advertise for 1/2 ropes are all done with a 55kg weight.
Osmo

Trad climber
Calgary, Alberta
Apr 16, 2009 - 06:46pm PT
One thing I didn't say before, because I was already going long, is that most falls are fairly low fall-factor, relatively dynamic, and so, in the elastic range of ropes, even small ones; and so that's what I was talking about. Someone else already said that ropes in the real world live a lot longer than the tests suggest, because the fall situation in real climbing tends to be much gentler than the tests, which are statically belayed and very severe.

Obviously the UIAA tests ropes to failure, and that means that their tests push ropes beyond the elastic, into the plastic range, where permanent deformation (stretch) and stiffening happen; in effect the rope becomes a caving rope. After the first drop, there's less stretchiness to absorb the fall energy, and so the peak (impact) forces leap up, and so does the per-drop damage to the rope (and anything connected to it).

The good thing about standard tests is that they are consistent and repeatable, but in order for them to be of any use, they MUST have an end; in other words they must push the rope to destruction, in a standard way, to tell the world exactly what the rope can take. Unfortunately, too many climbers interpret the "falls held" literally, in terms of their real world of climbing, and are ready to retire their good rope after a couple of modest falls, while the rope might readily handle 100 falls of that type.

The UIAA want everyone to be safe, while rope makers want to sell rope, so they would like climbers to presume that every fall is a worst-case fall and buy a new rope around the occurrence of the prescribed number of official falls (to be safe, you know...).

Meanwhile, climbers who don't want to be getting new ropes for every trip, need only keep aware of the kinds of falls they've been taking, and be realistic about what the official drop test results mean to them. A start would be for the new ropes to be labeled, "DROPS held" to keep buyers aware that "drops" does not, generally, mean "falls", by a huge margin.
Osmo
tradmanclimbs

Ice climber
Pomfert VT
Apr 16, 2009 - 07:37pm PT
Dude, what does all that drivel have to do with the simple fact that 1/2 ropes contrary to populer myth DO NOT HAVE SOFTER IMPACT FORCES THAN SINGLE ROPES?
Osmo

Trad climber
Calgary, Alberta
Apr 16, 2009 - 08:41pm PT
That's the point: they DO, as I see any number of guys on this forum have experienced. A THIN ROPE GIVES A SOFTER CATCH--this means a lower impact force than a thick rope, unless maybe it's a real bad (unusual) fall: high factor, big climber, and a very thin rope, so it gets pushed into the plastic range, where the force shoots up (a bit).

What made me post in the first place is that suddenly I see a bunch of innocent climbers being told to change their understanding (which is readily demonstrated: ie., true) that a thin rope gives a softer fall-stop--easier on the climber and easier on the pro., NOT easier on the rope of course, because it gets stretched more than a thick rope. And all on the basis of generally unrealistic test results, which almost never apply in a climbing situation.

Osmo
tradmanclimbs

Ice climber
Pomfert VT
Apr 16, 2009 - 09:00pm PT
Osmo, yer smokin that shite again. The numbers don't lie. if you fall on a single strand of skinny 1/2 rope your fall will be just as hard or harder than the same fall on a standard single rated rope.
tradmanclimbs

Ice climber
Pomfert VT
Apr 17, 2009 - 06:49am PT
This is one of the biggests myths surrounding the aura of the doubble rope system. The mear act of clipping a skinny rope to a suspect piece of gear does NOT magicly give you a green light. You can however use your doubble ropes to share the load over several pieces of suspect gear thus reduceing the load that each piece feels.

It has however been my experience that most double rope falls end up being caught by a single piece of gear clipped to a single strand of rope.
Osmo

Trad climber
Calgary, Alberta
Apr 17, 2009 - 01:20pm PT
Sorry Tradman; I thought you'd be interested in doing some good for the climbing community--that's what we should all be doing here, and it's what I'm trying to do; I also take it that you're a very experienced climber, so you should know the difference in shock loads of thin and thick ropes from feeling them yourself.

What I'm saying is, "Hold on, everyone--don't go off on a tangent, changing what you always 'knew' to be true because of some numbers that don't really apply to CLIMBING". They are numbers from tests designed to break ropes, and I haven't even seen the numbers you're talking about.

You would like us to believe that all a climber needs to do to soften a fall is lead on two ropes of a certain size instead of one?--no doubt a bundle of the same ropes would give a VERY soft fall. Everyone will see that this just doesn't make sense--you'd hit the end of the rope and stop dead, likely pull the pro, tear out the anchor, or tear out of your harness. Just consider bungee jumping: they use a very stretchy 'rope' exactly to minimize the impact force by absorbing the fall energy in the stretch distance.

I'm sorry to disagree with you, but I think what you're saying even goes against what even YOU have known until now, but you saw some test results and misinterpreted them as a new revelation that goes against what climbers have known for years, not only from physics, but from experience in thousands of falls.

Just trying to be constructive: the UIAA test system results do NOT apply to the vast majority of real-world climbing falls, as long as we don't go overboard at thinning down our ropes, and so pushing them to, or near, their breaking point.

Osmo
Brian Hench

Trad climber
Laguna Beach, CA
Apr 17, 2009 - 02:48pm PT
Does the equation used to calculate Impact Force correct for the fact that single ropes are drop tested using a 80 kg weight and half ropes are tested using a 55 kg weight? Can you directly compare the Impact Force rating that comes with the rope and say that the one with the lower impact force gives the softer ride?
tradmanclimbs

Ice climber
Pomfert VT
Apr 17, 2009 - 06:46pm PT
Brian look up thread and follow the link to jim ewings post. For as long as i have known about doubble ropes (since about 1985) we allways assumed that they had a softer impact force on the gear than single ropes. This was a combination of old wives tales (see Osmos posts) and the fact that the 1/2 ropes are tested with a lighter weight 55kg than the 80kg weight used for single ropes. That 55kg test gave some really light published force numbers.
Jim from sterling rope went ahead and tested some 1/2 ropes with the 80kg weight and big supprise to most of us he proved that the 1/2 ropes are not nearly as soft as we thought they were. This is important info for anyone who uses the doubble system for funky gear placements. You can't just clip a skinny rope to a crap piece thinking that your rope is extra soft and call it good. Your rope is not extra soft and will yank that crap gear just as fast as your old fat single rope. If the gear is crap you still should use screamers and multiple pieces clipped to seperate ropes unless you like to ignore facts and bury your head in the sand.
tradmanclimbs

Ice climber
Pomfert VT
Apr 17, 2009 - 06:52pm PT
Osmos, I feel the UIAA tests and breaking stuff is very helpfull. You have to know how to apply the results to climbing scenario. In this case it is clear to me that the information Jim posted would change the way I use and think about the doubble rope system.

ionlyski

Trad climber
Kalispell, Montana
Apr 19, 2009 - 10:26pm PT
Is there any advantage to building your protection "system" all on one rope? Multi directional pieces early in the pitch, protecting nuts and cams farther up the line from zipper effect and other nasties and so maybe losing some of that security because there are fewer pieces per rope in the double rope system?

That sounded moronic didn't it? Yes, it did.

Osmo

Trad climber
Calgary, Alberta
Apr 19, 2009 - 10:54pm PT
Hi Tradman; We're still waiting for the "facts" that you're talking about. In fact, the UIAA rope test results are almost completely useless to climbers, and I only say "almost" by habit, to allow for the slight possibility that someone might come up with some vague connection between those tests and climbing.

Convincing climbers to use a thick rope instead of a thin one, or clip in both ropes instead of just one, on manky protection, becomes a matter of dangerous misinformation if you're wrong.

The impact forces stated from the UIAA-type tests do not relate to climbing, unless you are habitually taking FF1.7+ falls on a completely static belay, through a rigid piece of protection. ARE you? Have you EVER taken one? Do you know anyone, or even ever heard of anyone, who does? Right: No, and you don't. And you also don't know anyone (including you and me) who knows how to "apply those results to the climbing scenario", because they don't apply, at all, in at least, say, 98% of climbing falls.

Why that's important is that the UIAA test setup is not just a severe extrapolation of a real climbing fall situation: the test pulls the rope right out of the elastic range and into the plastic (ie., destruction) range, where it behaves as a very different material and exhibits the distorted impact forces that you mentioned. The normal climbing protection system is intended to keep the rope in the elastic range: big enough rope, small enough climber, low-enough fall factor. As long as this is done, a rope is good for a huge number of falls, and thin ropes stretch more and produce lower impact forces than thick ropes, as has long been known by countless climbers (as well as the physicists).

Here are a 'coupple' of comments which I've borrowed verbatim from Climbing.com, on the UIAA rope tests:

"Falls held. The UIAA standard fall test is thankfully very severe, far outstripping almost any fall you might encounter in the real world.

Static and dynamic elongation. Dynamic elongation is measured on the first fall of the standard UIAA fall test. The higher the dynamic elongation percentage, the cushier your fall."

There you have it, and everyone knows that a thin rope elongates more during a fall (ie., dynamically) than a thick rope. But don't take my word for it.

By the way, Sterling Jim is obviously doing the right thing by testing every lead "rope" with 80kg, incl. half-ropes being used individually for leading. But again those tests tell climbers almost nothing (and all the numbers are irrelevant) except that the rope can withstand extreme abuse well beyond regular climbing falls. Keep in touch.

Osmo

tradmanclimbs

Ice climber
Pomfert VT
Apr 20, 2009 - 06:25am PT
cosmo osmo. Reading comprehenson skills. Jim had proven that single and half ropes have simeler impact numbers when tested with the same weight. That fairly clearly dbunks the old wifes tale that a skinny rope when used by itself is softer. Add to this the known fact that as ropes wear out their impact forces get higher it shouldn't take rocket science to figuer out that it is a good idea to use multiple pieces in situations where the gear is funky and the chances of a fall are high. With the Double rope system you can spread the working load over both ropes seperatly and therfore improve your chances of survival.

Your argument seems to be that skinny rope has such a soft impact force (old wifes tale) that you can stuff that Grey #00TCU behind an expanding flake and simply because you have your magic skinny rope you can just clip it and go. No need to worry about adding a screamer or backing it up with a piece clipped to the other rope. Heck eveyone knows these skinny doubbles are soft so i'm gonna just clip this one crap piece and go fer it dude....

By all means PLEASE DO because this is geting old and I actually have work to do today....

ionlyski

Trad climber
Kalispell, Montana
Apr 20, 2009 - 09:20am PT
It's only getting old because you guys are arguing instead of discussing. This is exactly the type of thread that should be continued to be discussed. If there is anything to learn here, I'll keep checking in for any little, new tidbit. It beats the off topic threads.

Cmon guys. You gonna ignore my post above? Is there an advantage to sewing up a pitch on one rope, in regards to preventing zipper or walking cams?
Arne
Francis

Trad climber
San Francisco
Topic Author's Reply - Apr 20, 2009 - 10:06am PT
This Just in from the UIAA themselves:

Dear Francis Baker

The half ropes are for being used alternatively one strand in a runner and
the other in the next runner. Therefore when falling the climber just fall
on one strand, so the UIAA has considered that one strand of half rope must
be able to withstand once the fall of a climber of 80 kg in fall factor 2 .
But doing just a test with one fall is not very convenient and reproducible
so the UIAA has searched for which mass, 5 falls are equivalent to 1 fall
with 80 kg. The following formula has been found by experimentation :

N x M 4 = Constant

where N is the number of falls withstand by the rope when a mass M is used.

Using this formula we find that withstanding 1 fall with 80 kg is equivalent
to withstanding 5 falls with 55 kg . ( 1 x 80 4 = 5 x 55 4 )



I agree that’s need some explanations!

Best regards,


Jean-Franck Charlet UIAA SAFCOM President"

So there you have it... I could blather on more, but most of it has been covered above.

have a fun, safe, adventurous climb!

f


tradmanclimbs

Ice climber
Pomfert VT
Apr 20, 2009 - 10:22am PT
Arne, if the climb is of the nature that a fall may likly result in the zippering of a significant ammount of protection then INMOP the doubble rope system is the best way to tackle this problem. the only advantage the single rope has in this area is that it is easier to transport to the cliff;)
dirtineye

Trad climber
the south
Apr 20, 2009 - 10:32am PT
Impact force felt by climber is NOT EQUAL to total force on gear.


Stop thinking that.

the top piece feels just as much force, only spread out over more time, with possibly a lower peak value, that could be possible.

Ask Rgold.

maybe I'm wrong, I don't think too well these days.
tradmanclimbs

Ice climber
Pomfert VT
Apr 20, 2009 - 10:36am PT
I am shure that you tech guys can explaine aLL that but shouldn't a rope with a softer impact force rateing also provide a softer load at the top piece?
del cross

climber
Apr 20, 2009 - 10:53am PT
Half ropes are stretchier if you just hang a weight on the end. But you can't extrapolate from this and say they give a softer catch in a climbing fall. Ropes are more complicated than that.

Sterling Jim showed pretty convincingly that half ropes and singles have similar impact forces in UIAA drop tests. Osmo is saying that you can't extrapolate from those results to real life fall situations. He is guided only by his experience and intuition. The counter-argument must rely upon some model of rope physics to extrapolate the test results. Can that model, whatever it is, be trusted?
tradmanclimbs

Ice climber
Pomfert VT
Apr 20, 2009 - 11:11am PT
osmo is just talking out his butt.
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 04:30pm PT
OK guys; now we seem to be getting somewhere- I don't mind the occasional jibe as I have a sense of humor, and 'sense' that Tradman is starting to feel constructive through all our back-and-forth; and in spite of his last remark--he seems to be quite a fun guy.

So, by the way, Tradman, definitely a rope with a softer impact force rating should provide a softer load at the top piece IF THE RATING IS CORRECT for the situation. In the case of the UIAA-type tests, a rope with a lower impact force providED a lower load at the top piece IN THAT TEST, since there is only one tension in a specific section of rope between 2 contact points; but that rating is NOT CORRECT for a climbing-fall situation and can not be 'infrapolated' (if you like) to climbing falls.

To Del: I'm not just going from experience and intuition, as I'm an engineer, and familiar with the basic physics of stretchy materials, which are well-documented: climbing ropes are made of typical stretchy materials.

This will be another long one--sorry, there's no other way, as there's a lot to say, as you said, "ropes are complicated". So get out a piece of paper and a pen, read carefully, and try to draw the graph I'll describe--I wish there was a way to include a sketch in this forum, so you wouldn't have to draw it yourself.

It's possible for a thin rope to overtake or even 'out-impact' a thick rope IN THE DROP-TEST, and that can be explained because the tension curves sweep upward in the plastic zone and since the thin rope is farther into the plastic zone, its curve is steeper and so converges toward the extension of the thick rope's curve, which has been above it from the onset of tension.
I know that sounds like B.S. but it's important; also it's easy to understand in graph form, with tension on the vertical axis and %-stretch on the horizontal--draw and label the 2 graph axes: both graphs start from the "origin" (viz. zero tension, zero stretch) and go up and right as (essencially) straight lines, with the line for the thick rope being above that for the thin rope--draw 2 straight lines angling up and right from the junction of the graph axes at different angles. At some point along the stretch axis, both ropes leave the elastic zone and curve steeply upward, but shortly after that, the upper curve (for the thick rope) STOPS, because the big rope has absorbed all the energy of the drop--draw a horizontal line across the graph, through the end of the upper curve; however, the thin rope is 'weaker', with lower tensions all along, and has NOT yet absorbed the drop energy at that % of elongation, and so it continues to stretch, plastically, and its graph continues right and upward toward the horizontal line representing the peak or impact force of the thick rope, and so could in some cases, reach or cross it, depending on the specific polymer, comparative rope cross-sectional areas, etc.

At some %-elongation (maybe say 20, and different for all materials), a vertical line crosses the graphs for both ropes (which should be the same material, as we're comparing rope sizes, not the materials) right at the point where they both change from straight to curved lines--draw a vertical line. All climbing falls should end to the left of this vertical line, and that is arranged by a suitable combination of climber size, rope size, and fall factor--you'll notice that the tensions for the thick rope are higher than for the thin rope throughout--those are the real-world climbing-fall impact forces that we've been talking about.
Meanwhile, the UIAA drop test is necessarily to the right, as they need to break each rope within a reasonable number of drops in order to be able to document its "ultimate strength".
The drop mass of 80kg is suitable for a typical climber, but the usual ropes tested for use as single lead ropes MIGHT NEVER BREAK if tested at typical climbing fall factors and setups, so they are instead tested in an extreme and unrealistic setup, with a static belay, rigid 'protection', and a fall factor of about 1.7-1.8. Because of the curving graphs beyond the climbing-fall (elastic) range, the impact force numbers from the UIAA tests have no relevance whatever to the climbing scenario, except that impact forces in climbing falls are MUCH lower, and "falls held" could realistically be rated much higher, quite seriously 100 or more.

As for hanging a weight on the end of each (thick or thin) rope, for sure the thin rope stretches farther, and that absolutely CAN be extrapolated to climbing falls, as both cases are in the elastic range of lead-ropes for normal climbing situations. Again, results from the UIAA drop-tests can not be extended to climbing, as those tests are beyond the elastic range of lead-ropes.

One really scary trend is that climbers are using thinner and thinner ropes, meaning to use them as doubles or twins, but occasionally someone will decide to misuse the "ropes never break" concept, and lead on just one of them as a single; and if he takes a major fall, then at some point in the circumstances: maybe 250pd climber, falling directly on a locked-off belay on a 6mm rope, possibly even a 7mm or so, the rope will snap and send him to the scree. Thinner ropes are stretchier if used as intended, and so will stop a falling climber more gently, but they also have lower energy-absorbing ability than thick ropes, and so if misused, they are more likely to fail in a severe fall.

Finally, the rope physics model (as I describe it) CAN be trusted, but no doubt everyone should feel a lot better if we had some data from climbing-realistic drop tests to back it up.
Jim Ewing was only doing his bit by providing the tests specified by the UIAA, PLUS extending them to sub-single ropes being used as single ropes, so he can't be faulted for that, and even the unrealistic UIAA test setup must be understood with some sympathy on the basis that I've already stated twice.

But now I propose a few simple drop-tests toward the "serious" end of the climbing-fall range, to provide some meaningful numbers for climbers (for the first time?): 80kg weight, whatever rope might be considered for leading singly on, fine, go ahead and use a static and rigid belay (as that may be achieved in real-world climbing), and a fall factor of perhaps 0.5! I think 0.5 is pretty high as falls go: lead out 75ft., place a final piece, then climb another 25ft. and fall off--50ft. fall on 100 ft. of rope. Data from such a test could be related to the real world of climbing.

Ideally, each rope would be tested for energy absorption at the top of it's elastic range, and the results provided to buyers in a graph form relating climber weight to maximum allowable fall factor, or such. Until we have that, climbers have little to go on except their experience and intuition, unless they deign to believe well-established physics.

Osmo
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 05:07pm PT
Hello Dirtineye; Impact Force (say Fmax) is generally taken to mean the maximum tension in the rope--that's the peak force that the falling climber feels, and it also reaches and pulls on, the top piece of protection unless the rope touches anything in between the climber and the pro., which would slightly reduce the force reaching the pro. The rope crab on the top piece acts as a poor pulley (I usually consider it about 50% from my own crude tests), so in that case, half of the tension on the climber's side gets to the belay side of the protection. As a result, the peak force on the top piece is Fmax + 0.5Fmax, or 1.5Fmax. That's another reason that climbers should be so interested in minimizing impact force: the protection gets hit harder by a fall, than the climber or the rope.

Osmo
dirtineye

Trad climber
the south
Apr 22, 2009 - 05:14pm PT
Osmo, you sould really confused. YOu ahve misuesed some terms. I'm not listnening any more LOL
Now, wait for Rgold to give you the correct explnaation, nad look for JIm ewing to show up and do the same.

Um, before I got wasted by chemo and other crap, I did indeed have a math/physics degree, and graduate school in math, so at least I know who to listen to, and that woudl be Rgold (professor of the very stuff we are discussing, and Jim ewing, rope engiineer, one of the few in the country actually working as a rope designer.

I tend to trust what they say over, um, the rest of the crowd, including me, thank you very much.

Beal has a good series of explanations of a lot of this impact force stuff if you care to look it up. I posted the links here years ago, and others also found it and liked it, so, this is not exactly new stuff you see.
del cross

climber
Apr 22, 2009 - 05:16pm PT
Osmo, I understand the basics that you painfully detailed. But you can't reasonably argue that half ropes are stretchier when you use that as a starting assumption.

And where did you get the idea that single ropes are out of their elastic range in drop tests? Did you just make it up? Actual drop test data shows the force vs. elongation curve to be pretty much a straight line.
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 05:55pm PT
Hello Francis: interesting explanation of 55kg from the UIAA--I take it the "4"'s in their equation are exponents?; that does work out about right.

I had my own theory about how they came up with 55kg.: something like 50 years ago, 11mm nylon ropes came to be accepted as a safe size for a single leading rope. Then somewhat smaller ropes were introduced, possibly for all the advantages we know of for the double/twin-rope systems: full-length rappels, greater immunity to rockfall and edge-cutting, and reduced drag through wandering protection. 9mm was accepted as a common size for such smaller ropes--who knows why?: 9mm is considerably bigger than half of an 11mm rope; possibly it was a compromise of accepting greater total weight and bulk for the stated advantages of two ropes, AND the possibility of occasionally leading on a single 9 (with caution). In any case, the UIAA deemed only the 11mm to be acceptable as a single rope, but the 9 was called a "half-rope", obviously not meaning that it is half the 'strength' of an 11, but rather that a 9 could be approved for leading on ONLY if used in a pair, to form a 'full rope'--the implication could be that both ropes would be clipped into protection, together, in "twin-rope" fashion, OR maybe the 9mm, not that much smaller than 11mm, was chosen on the basis of the double-rope system where the highest-clipped half-rope could sustain the entire shock of a fall without the second rope coming under tension at all.

At first, all the attention of testing was on the ability of a rope to withstand a fall without breaking: impact forces were not considered until later, although it must have been obvious all along, that the stretchiness of nylon and other synthetics was the key to the survival of a rope in a fall. A hemp rope can be very strong, but its lack of stretch makes it a disastrous choice for a climbing rope, as the impact forces must be extreme to make up for the static behavior, in energy absorption: the rope breaks in minor falls.

Anyway, a lead-rope was tested by dropping a standard 'climber-size' weight onto it in a standard configuration, but when it came to testing the half-ropes individually, someone must have noticed that it didn't seem fair to use the same drop-mass, since the rope was not intended to be used singly as a lead rope. It's obvious to me that if half-ropes are intended to be used in pairs for leading(twin-fashion), then an individual half-rope should be tested with a 40kg weight, so why 55kg? A bit of arithmetic reveals a possible explanation, although slightly convoluted: the cross-sectional area of a 9mm rope is 81/121 of that of an 11, and multiplying that by 80kg produces 53.55kg, which is close enough to round off to 55 for convenience. In any case, using 53.55 instead of 55 in your equation from UIAA produces an even better result, so that may be a verification of the trial-and-error method the UIAA used to decide on 55kg for 5 falls.

Keep in mind that this also demonstrates that smaller climbers can use smaller ropes, but big guys beware. 55kg would work for a 9mm rope of the same material as an 11 tested with 80, but ropes smaller than 9 could not be expected to withstand as many drops with 55kg.

Osmo
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 06:28pm PT
Sorry Del; I can't imagine your problem in seeing why a thin rope is stretchier than a thick rope--it's common sense to anyone who knows the (simple) physics inside out, but to others who don't, you can rely on the physics itself, and finally all this is supported by endless experience, which is in a sense,
'data'. Even the UIAA admitted to deriving an equation by experiment.

As for the elastic range, it's this simple, almost by definition: if it was in the elastic range, it would not break (at least, not in 5 drops) because it's not being damaged. The UIAA MUST damage the rope, so that it WILL break within a realistic number of drops, so that they CAN say something about comparing the relative ultimate strengths of various ropes.

I would like to see the "actual drop test data" you're talking about, whether it was a copy of a dynamometer printout, or an artist's concept for the rope maker, based on a couple of data points, or what. I'm not being combative here, at all, but I know that I'm a lot more 'piercing' when looking at evidence, than many people are, especially when they're trying to debunk me. I don't care a bit about winning anything--but I do want to get to the facts.

Furthermore the shape of the curve beyond the elastic range is a wildcard, and it could go on for quite a ways, or it could kink upward sharply and end quickly because the impact force reaches the break strength of the rope after very little additional elongation. For example, if the elastic elongation limit of a particular rope material is 20%, and the breaking elongation is 21%, that final 1% on the curve might hardly show up, and would be easy to miss, or ignore, or not admit, etc.

Can you refer me to the data you mentioned?--I'd like to see it, I might learn something, maybe not.

Thanks, Osmo
Dr.Sprock

Boulder climber
Sprocketville
Apr 22, 2009 - 06:30pm PT
Why can not a pro engineer post a chart online?

even brain dead me is always throwin down the many jpg's, word up?

not even some chicken scratch on a restaurant napkin for chrissakes.

but hey, the college was cheap, what, only 120 grand?

TradIsGood

Chalkless climber
the Gunks end of the country
Apr 22, 2009 - 06:34pm PT
dirtineye, It should be quite obvious that OSMO is right about the force on climber versus force on top piece of gear.

The only way they would be the same is if the rope tied to the climber was tied to the top piece. Assuming a belay is the only thing keeping the rope from accelerating (that happens with forces) is a force in the opposite direction. If the carabiner were "ideal frictionless" the peak force on the gear would be twice the peak force on the climber.

In the real world friction reduces that force to prevent acceleration of the rope through the carabiner.
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 06:46pm PT
Dr.Sprock; when someone has nothing useful to contribute, he becomes abusive to hide it, but it doesn't look good. I thought I saw something worthwhile from you a ways back, why not stick to that as a pattern? I didn't even try to put in a sketch, as I expected you to be able to follow my explanation, and I've never seen one from anyone else: have you ever contributed one?

Osmo
Osmo

Trad climber
Calgary, Alberta
Apr 22, 2009 - 06:53pm PT
Hello dirtineye; yes you seem to have some problems, sorry to hear it, and I will take your hint to look up what info Beal has about tests and impact forces. A person can waste a lot of time hunting for useful material, so a pointer is appreciated.

Osmo
del cross

climber
Apr 23, 2009 - 09:07am PT
> if it was in the elastic range, it would not break

Osmo, I expected you to say this. But I was using your own verbal picture in my response. You said that in drop tests "ropes leave the elastic zone and curve steeply upward". But this is not what is observed.

Now you say "the shape of the curve beyond the elastic range is a wildcard". Okay, fine. But if this new picture of yours were true for nylon ropes it would fail to explain the results of Sterling Jim's tests. To support your theory the force had better go up as you originally said.

Yes, a rope is damaged in a UIAA drop. It gets damaged in a normal fall too. Rappelling damages a rope. You are using too simple a model for a complex object. The "elastic range" is an idealization that doesn't match reality for a rope.


I think your original point might have some merit. But your anecdotal "data" and engineering background don't serve to get us anywhere.
Osmo

Trad climber
Calgary, Alberta
Apr 23, 2009 - 02:24pm PT
OK Del; apparently you just want to argue: I didn't claim to present any data, anecdotal or other; I'm still looking (and waiting) for SOME regarding the drop tests; and forget about my engineering background--that's bound to bother some people, but I thought it would give me a bit more credibility than only as another climber (which I am, and have been for a long time, and learning the whole time). But it bothers you, so forget it; I don't need it, as the stuff I've been talking about is well known and established, and can readily be looked up in any number of physics texts--I didn't claim to invent it, so if you don't like it, don't blame me for it.

And I never said anything about rope damage through friction, or using screamers, etc. which other people have mentioned, since those things are off the topic of impact loading of ropes, and would only cloud it.

I know about sheath damage in rappelling, and the value of screamers, and some other issues that are all topics for other threads, but when the UIAA specified their drop tests, they didn't specify screamers (for example), because they WANT the rope to break within a few falls, because it HAS to, otherwise there's little they could say about what the rope could REALLY take. And when those ropes fail, it's not because of sheath damage from rappelling, it's from excessive elongation resulting from progressive plastic damage from one drop to the next. That's what climbers want to avoid--if we have to fall, we'd like to keep our rope in the elastic range, ideally so it will rebound fully and be ready for the next fall, and the next, and the next.

You want a complex model?--and yet you're having trouble grasping the simple idea of elasticity; you're better off to tackle one concept at a time, and you know what?--as it happens, simple models generally work extremely well for representing real-world systems in spite of their apparent complexity.

Then you say, "But this is not what is observed." FINE, if that's true, let's have it: talk about "anecdotal"!--I have been looking, and waiting, and still have not seen any real 'observations' or data, except point-shots called impact forces--so what should we do? draw a straight line from the origin to the impact force and call it good for a representation of the rope's behavior during the test?! Sorry, that's no good: 2 points does not make a graph, and further, such a graph would clearly suggest that the small rope absorbed more energy than the big rope, while in fact the absorbed energies are much the same.

I'm still looking elsewhere, and also eagerly waiting for your claimed 'observations', including Jim Ewing's test results, which you say I can't explain--I've seen some of his numbers and was surprised of course, but after a little thinking, offered a viable explanation, unless some new information appears, which contradicts it.

So Del, what do you know? Have you seen a curve?: preferably drawn by a plotter immediately following a drop test? Maybe a bright-colored graph from a tag included with a rope? Anything? Let's have it. Please share it with me--all of us who are interested in ropes. Surely you wouldn't want to see all your friends continue to clip in only one of the ropes on manky protection, knowing that 'both clipped in' is easier on it?

Thanks in advance, at this point I'd even welcome being proven wrong about one thing--at least I'd be learning something new, but so far I'm getting mostly jibes and bickering from guys who don't like to be told about 'their' sport.

Osmo
Jim E

climber
away
Apr 23, 2009 - 07:01pm PT
What was/is the question? Seriously.
Dr.Sprock

Boulder climber
Sprocketville
Apr 23, 2009 - 07:22pm PT
One experiment is worth a million theories, so the best way is to go out back and hook up an anvil, and have at it.

and i do have a chart up on this thread, i forget what page.
did you see it?
it was two small circles and one
Jim E

climber
away
Apr 23, 2009 - 07:29pm PT
I use one of these...

and a drop tower.
Osmo

Trad climber
Calgary, Alberta
Apr 23, 2009 - 08:15pm PT
Hello Jim; good to hear from you; I sent a note to Sterling the other day, to get in touch with you.

We've been going at it for a few days here after another guy mentioned your 80kg half-rope impact force findings and started advising everyone to start clipping in both ropes or a big rope, to their questionable protection, to give it the best chance of surviving a fall. I could just feel the eyebrows snapping up throughout the forum at that advice, and said, now just hold on, we all know from long experience that thin ropes stretch more and give a softer catch, so what's going on? I went into the physics of stretchy materials to explain the high impact forces near breaking and how they do not relate to the real world of climbing in the elastic range: --sorry.

Anyway a couple of the guys have been very sensitive about being preached to, so I'm saying what we really need is some drop tests in the realistic fall-factor range. Several climbers in the various forums are agreeing that 1.0 is pretty extreme, never mind 1.78, and I suggested that even 0.5 is serious in terms of "common" climbing falls: say 25 ft. above a 75ft. final piece: 50ft fall on 100ft. of rope.

Have you done, or could you do, some such tests? This is the kind of data that climbers need. Just think, you could test the ropes and still sell them as new.

Thanks, Osmo
Osmo

Trad climber
Calgary, Alberta
Apr 23, 2009 - 08:25pm PT
Dr.Sprock; yes I saw your diagrams and that's what I was referring to as something worthwhile--definitely a cut above your last entry previous to this one. But no fear--I'm getting a bit tired of this too, and Sterling Jim may come to the rescue--let's see what he says about some real-world impact tests.

Osmo
Dr.Sprock

Boulder climber
Sprocketville
Apr 23, 2009 - 09:50pm PT
you can try and get into it from a rigorous approach, but it would be a model with many variables.

thats why i bet a lot of other people have not offered up a big scientific explanation, they know it is futile.

it would be like doing an analysis of a pile of wood blocks stacked in a pyramid.
you pull out a bottom piece, what exactly happens next?
too random to predict, although, believe it or not, some bored scientist on his lunch break developed a program that does just that.
but does it work in real life?
how would you know?
you would have to duplicate the exact model in real life to test it.

rope is sometimes woven, sometimes knot.
i imagine that the interaction of the core with the sheath would be a master thesis all by it self.

thermo, braiding action, core/ sheath, too much for my small brain.
thats why i head for the gym to try it out.



not only does the experiment win out over theory, it usually takes a hell of a lot less time to reach a conclusion.
tradmanclimbs

Ice climber
Pomfert VT
Apr 24, 2009 - 12:23am PT
Osmo, Obviously you did not understand my posts, INMOP if the gear is sketch and the liklyhood of a fall is high you should place multiple pieces of gear and clip them SEPERATLY to alternating ropes if useing the double rope system. You aparently sugested that just clipping one strand of 1/2 rope to a sketch piece provided a soft enough catch that other percautions were not needed.

I contested that clipping a single strand of 1/2 rope to a sketch piece was little diferent than clipping that same piece to a standard single rated rope.
tradmanclimbs

Ice climber
Pomfert VT
Apr 24, 2009 - 12:29am PT
I bet your hardest common climbing falls are the 10 to 15 footers on 20ft of rope blowing the 2nd clip.
Dr.Sprock

Boulder climber
Sprocketville
Apr 24, 2009 - 12:49am PT
OK, GRAPHS you want, charts you get.

here is a simple experiment to show the difference between ropes.

maybe used stuffed animals instead of humans.
see which head gets snapped.
someone i can tell experienced more g's than the other three.
but ya never know.
in todays economy, you might find volenteers.



healyje

Trad climber
Portland, Oregon
Apr 24, 2009 - 02:39am PT
Geez, talk about a bunch of knickers in a knott...

While I appreciate that our gear today are engineered products, I'm totally Edisonian in my approah to all this business. Thirty five years of climbing has taught me that 99.5% of climbing all happens well within the tolerance our gear and the very rare and deadly .5% are extreme edge cases. Now, that's not to say you shouldn't know about, be able to recognize, and avoid those edge cases, but I feel that today's climbing world is a pretty paranoid lot and heavily fixated on the 'rules' for this or that - i.e. 'always do this, never do that'. And I suppose in the context of the demographics involved with climbing today that's a reasonable deal - but it doesn't and never will reflect the reality of my climbing.

Over those years of climbing, I've climbed on a wide variety of ropes in doubles mode from 8.x to 11's to various mixed size combos. Typically when I depart from 'norms' or specs in my use of ropes (or screamers for that matter which I often pre-slice and label in a variety of ways), it generally means I'm on incredible sharp rock, really bad or technical pro, or both as in the case of a route I've been working the past two years. I'm usually operating in territory that's R-to-Xish, and often for more than one reason. The possibility of falling and somehow miraculously ending up with both ropes equally sharing the load is the very least of my concerns regardless of how or what I clip; but then I rarely if ever clip both ropes into a single piece as it's a pretty useless excercise. When I do, it's usually more about rope management and I use two biners end-to-end vs. side-by-side to avoid enabling that braking affect.

By and large if you're in territory where you absolutely better be on doubles - and sometimes one or both burly lines - then fall factors, loads on pieces, and body shock rank right up there with being hit by ligthning while I'm on a pitch. That said, you better really know the game well before you start bending and / or breaking the 'rules'. By 'know the game' I mean know your technologies of choice; have an intimate understanding of rock and pro; know how to perceive, rank and prioritize risk; and able to craft a consistently coherent and performant rope system as you go.

In the end though [for me] on rock, it's all way more a matter of constructive art than science and engineering, which again I appreciate, but personally never leave the ground because they have no sustaining relevance for me at that point - I'm almost exclusively operating on experience, instinct and intuition.
hooblie

climber
Apr 24, 2009 - 07:02am PT
i'm exactly in agreement with healyje. i have an armchair appreciation for the scientific method. lab guys and theoreticians, and most especially, well spoken presenters of distilled results earn a special place in my heart.

jack dorn drove me crazy with technical safety specs, 50lb greater breaking strength kind of stuff. i argued that technicals only went so far, that the real safety factor had to do with intelligence, experience, judgement, intuition, tempered ambition, self knowledge as to limits, SOP's, etc. in a nutshell, not over pouring your cup has little to do with the cup. his death was a tragedy but i can't think of one technical value that could be applied to the particulars of his end story.

that being said the real value of this kind of thread is the contributions to the knowledge base which makes possible our intelligent application of the experience of others.
after you've weighed all the data and employed the human factors, the critical moment is when you hunch your shoulders and DECIDE, huh, i think i'll go for it.
for the record, leading on double lines satified me on many levels but i almost always succumbed to the less rigorous; huh, one will due.
dirtineye

Trad climber
the south
Apr 24, 2009 - 11:14am PT
Here's a spot where that index of Ander's would come in real handy.

Hey ANders, if you are looking at this, how about dredging up the relevant rgold/jim ewing ed H and a few others threads n posts on this topic, which has been more than adequately addressed over the years, and linking them to this?


It's a shame to dilute the good stuff with repeated attempts to create nonsense and drive away the guys who are doubtless by now TIRED of saying the same stuff over and over, and having it bounce off, only to rear it's ugly head yet again year after year.
Osmo

Trad climber
Calgary, Alberta
Apr 26, 2009 - 03:08pm PT
I'm back, briefly I hope, as it's good to see a few other guys getting in again--they were likely afraid to get rolled up in the snowball that happened here over the last couple of weeks.

To Tradman, I understood your posts perfectly, unless they didn't say what you meant, but that would be YOUR problem: I never talked about diversity, multiple pieces, screamers, etc. because they were all off the topic of relative impact forces between thick and thin ropes. I'm also all FOR, and USE, all that stuff, BUT what we're talking about (and you're trying to wiggle out of it) is:

What IF?: you're leading on 2 ropes, and get in a sketchy piece, just before a tough section, and it's the only piece possible, and you have no screamer?! You said we should clip in both ropes to minimize the possible shock on that questionable piece, to give it the best chance of surviving if you fall off. I say clip in only one rope, because it's stretchier than two, and so will shock that piece LESS. And from what I've heard from several others over at least 3 of these forums, what THEY think is the same (as we've known since hemp ropes).

But I'm open to some real-world impact force tests as proof one way or the other. I think that's what most climbers (like healyje) would like to see, instead of speculation and technical explanations, and I haven't seen any yet--the UIAA test numbers are from fall factors 2-3 times higher than realistic. Maybe Jim Ewing is thinking about that right now. Let's hope.
tradmanclimbs

Ice climber
Pomfert VT
Apr 26, 2009 - 05:18pm PT
Osmo. I NEVER said to clip 2 1/2 ropes to a single sketch piece. I DID say that you can use the doubbles as twins when the gear is bomber and the line of climbing is relativly straight.

You keep saying that a single strand of 1/2 rope is a softer catch than a normal single rope and Jims numbers CLEARLY prove that wrong.
Jim E

climber
away
Apr 26, 2009 - 05:20pm PT
"Maybe Jim Ewing is thinking about that right now"

I can assure you... he is not.
Osmo

Trad climber
Calgary, Alberta
Apr 26, 2009 - 05:25pm PT
OK Jim, I get it--it's a weekend; maybe during the week, you'll think about it; you should.
Osmo

Trad climber
Calgary, Alberta
Apr 26, 2009 - 11:24pm PT
Hi Tradman; we can all read in your many posts that you advocated clipping both ropes on sketchy gear because "Your ("skinny") rope is not extra soft and will yank that crap gear just as fast as your old fat single rope"--you said it yourself, as quoted.
Then in your last post you went on to compound your confusing opinion by contradicting yourself in two consecutive sentences:

"I DID say that you can use the doubbles as twins when the gear is bomber...". Ie., you're admitting what we all know already: that you should NOT clip both ropes when the gear is NOT bomber: why?: it can only be because a 'rope' of two ropes has a higher impact force (in a real climbing fall--do I really need to keep repeating that?) than only one of those ropes, alone, does.

But then you go on to try to have it both ways in the next sentence to the effect that 'Jim's numbers CLEARLY prove that a single strand of 1/2 rope is NOT a softer catch than a normal single rope'. Here it is:

"You keep saying that a single strand of 1/2 rope is a softer catch than a normal single rope and Jims numbers CLEARLY prove that wrong."

So which is it, Tradman? You were obviously unsure of what to believe, but it's either one or the other, so just admit it, pick one, and let's move on.

In fact, we can't be sure of what if anything, Jim's numbers--the ones I've seen--mean for real climbing falls, as his UIAA-type test results are from drops in the range of 2 to 3 times the fall factors of real climbing falls--a serious discrepancy. I believe they mean nothing to climbers in this regard.

No worry, guys, if we can't get any realistic data for rope impact forces in climbing falls, I may be prepared to do some tests myself and report the results here; we should be interested in the fall factor range from 0.5 to 0.75 as the Tradman suggests himself.

Osmo
That Darn French Guy

Trad climber
Santa Clara, CA
Apr 27, 2009 - 01:26am PT
> why they would drop a lighter weight for the half ropes

Maybe because they technically would not pass at full load, until now? But it's OK because double climbers would not dream to factor-2 on 1 strand anyways? It's frequent to clip both on the 1st piece, then alternate.

*Twins: For some reason no-one seems to use twins, yet they're lighter, and less cluster-f*#ky since they both feed together. Are they that much worst than single ropes when angles change that you get horrible drag?

* Doubles have another drawback: you can twist them when clipping if you don't pay attention, and you loose all benefits of splitting them for drag reduction when wandering.

* Singles: With singles the real BS is you end up carrying 2 10.2mm ropes all the way to the top to rappel, after all, so no matter what singles become way heavier than having two doubles/twins. If you don't that other single will stay at the base, aka you brought it anyways. :\

* Caught: Are doubles less prone to get caught? I mean the weight/length is less so maybe they could coil over themselves less as they fall down?
Jim E

climber
away
Apr 27, 2009 - 05:55am PT
"It's frequent to clip both on the 1st piece, then alternate."

I read and heard this said a few times over the past year. I would like to point out that from an impact force perspective clipping both on the first piece is probably the absolute worst time to do so. At no other time in a pitch is impact force likely to be higher, even on a single strand.
Tomcat

Trad climber
Chatham N.H.
Apr 27, 2009 - 06:10am PT
So Jim,I have an unrelated,sort of,question that may beg an unscientific answer.Tradchick and I climb on doubles just about all the time,and one really noticable difference between them and our single is when I make a catch,the doubles obviously have more friction,thus catch easier.

Do you think the odds of success with a FF2 fall are better with doubles,just due to added friction in the system?

In my case it's when she is following,so the strands are pretty well equal.I've caught plenty of lead falls on doubles,and as Trad has mentioned I believe,often it's really just one rope doing the work,so maybe a little more effort then,but what is your opinion in the case of the dreaded FF2,and disregarding,for now,the orientation issue.
Jim E

climber
away
Apr 27, 2009 - 07:23am PT
I think it's a fair assumption that catching a FF2 would be easier with double. More friction in the device and more rope surface area for the belayer to grip. Impact would likely be higher of course but would not really be a concern if the anchor is good.
Tomcat

Trad climber
Chatham N.H.
Apr 27, 2009 - 07:28am PT
Thanks Jim.
rhyang

climber
SJC
Apr 27, 2009 - 08:31am PT
It's frequent to clip both on the 1st piece, then alternate.

I've never seen anyone do this.
That Darn French Guy

Trad climber
Santa Clara, CA
Apr 27, 2009 - 10:18am PT
Well I have... Of course once clipped, technically you're only supposed to get 1x fall factor unless you run out to the 2nd piece.

However if the only reason they're rated at 55kg is because they take long to recover, it is dubious excuse, 'cuz they could've rated them 80kg, with less falls required to pass.

My take is at the time the standard was set, they were meant for teenagers, not burly trad climbers wearing too much gear.
That Darn French Guy

Trad climber
Santa Clara, CA
Apr 27, 2009 - 10:18am PT
BTW, why no-one uses twins then? Why does it suck more?
tradmanclimbs

Ice climber
Pomfert VT
Apr 27, 2009 - 01:03pm PT
F*#K YOU OSMO! you are just twisting what I say arround. for the f*#king reckord from day F*#king one of this post I have said that you can use doubbles as twins when the gear is bomber but you should use them as doubbles when the gear is not bomber. I have also posted repetedly that a single half rope is NOt softer than a single single rope. what the f*#k ever....


Dont twist my sh#t arround MFCKER
rhyang

climber
SJC
Apr 27, 2009 - 01:17pm PT
Some people do prefer twins, and my PMI verglas 8.1's are rated as both halfs/twins. A partner in Cody, Wyoming brought some beal ice twins (7.7mm ?) that seemed to work ok, though they left fuzzy bits 'o sheath on my reversino on raps ..
dirtineye

Trad climber
the south
Apr 28, 2009 - 09:43pm PT
Gee that's odd... I could SWEAR that the times I've been caught on a single strand of mammut 8.5 genesis were softer FEELING than the times I've been caught on a normal fat single.

Hell the doubles are like rubber bands in comparison, but that's just how it felt to me.

But any way, it's funny how nobody has even mentioned (that I noticed anyway) the main reason for climbing on two ropes as opposed to one-- which is, if you drop one, you still have a rope, LOL. And if you think that's a joke, just try dropping your single sometimes, on a multi-pitch route, hehe.
Osmo

Trad climber
Calgary, Alberta
Apr 28, 2009 - 11:06pm PT
Keep your shirt on, Tradman; once again you seemed to contradict yourself, but OK, it seems you think that a thick rope (or 2 thin ones) gives a softer catch than one thin one, which (and I hope to prove it) everyone knows is B.S. Even Jim E. said so himself, 10 posts up re clipping both ropes on the first piece, and he's the guy who did those tests--maybe HE also feels they don't apply to climbing? I think we'll get to the bottom of this impact force stuff yet....
tradmanclimbs

Ice climber
Pomfert VT
Apr 29, 2009 - 04:09am PT
I ain't contradicting sh#t.
del cross

climber
Apr 29, 2009 - 02:44pm PT
Osmo, I understand where you're coming from. It makes perfect sense that if you have a material with some modulus of elasticity that a sample with a smaller cross section will be stretchier. But ropes are not homogeneous strands of nylon. They're made in such a way that a large part of their elasticity comes not from the material but from the nature of their construction. And elasticity isn't the whole story. Ropes don't just stretch like springs but more like critically damped springs, converting a fair amount of fall energy into heat.

Look at the specs for ropes from different manufacturers. You'll see that the impact forces and elongations are not necessarily the same for ropes of the same diameter. In fact there is really no correlation between diameter and the impact force and elongation (static or dynamic) ratings for single ropes. Some fat singles are stretchier and lower impact than some thin singles.

So what about half ropes? Jim Ewing's tests show that this appears to be true for them as well. This result is surprising to most climbers, myself included. It runs counter to common sense. Half ropes *feel* stretchier!

Your conjecture is that the UIAA test is so severe that it doesn't apply to the real-life fall behavior of ropes (half ropes at least). Maybe you're right, I don't know. But you just saying that it is so because of "common sense" and a simple physical model isn't convincing.
jstan

climber
Apr 29, 2009 - 03:10pm PT
At the risk of stating the obvious:

If you integrate the force displacement/stretch product for an 8mm and an 11mm rope and evaluate it at the same final value of stored energy you find the ratio of the stretches are inversely proportional to the rope diameters. So the stretch in an 8 mm rope is almost 40% greater than it is for an 11 mm if we assume all other properties of the two ropes are the same.

You travel an extra distance with the smaller diameter.

But our problem is we have not really defined “softness”.

If peak force defines “softness” we have to think some more. When a rope stretches more, the total amount of energy in foot pounds to be stored is increased by the product of the climbers weight times the length of extra stretch. To get an answer to this definition of softness we have to know the physical properties of the ropes and do the full calculation. To do this we need to assume how much rope is in the system and we need to include frictional losses over the biner. It may even be possible the relationship between the two ropes' peak forces will depend critically upon some of these assumptions.

So those with already prepared spreadsheets, assume away!

That Darn French Guy

Trad climber
Santa Clara, CA
Apr 29, 2009 - 05:01pm PT
BTW, does it matter if the ropes have different specs when climbing doubles?
Unlike twins it seems like you wouldn't care so much.

MTtools lists static/dynamic elongations and impact forces:

http://www.mtntools.com/cat/rclimb/rope/BealFlyerDynamicRope.htm

Impact force (softness?) and elongation seem independent of rope diameter:

Twins- 07.4mm: 36% elong 7.4kN
Single 09.4mm: 37% elong 8.2kN
Single 10.2mm: 38% elong 7.4kN
Single 10.5mm: 37% elong 7.4kN

Clipping doubles together increases impact force and reduces elongation:

Joker twin-- 9.1: 29% elong 9.5kN
Joker single 9.1: 37% elong 8.2kN
rgold

Trad climber
Poughkeepsie, NY
Apr 29, 2009 - 05:53pm PT
I'm with Curly on this one (ok, ok, a bit of an in-joke---I'm speaking of Del Cross here). Nowadays engineers model viscoelastic materials with combinations of springs and dashpots in either series or parallel or both, so the pure spring analogy is tempered with varying types of viscous damping. And that's just the material part. Ropes have different internal constructions, different sheaths, and the nylon is heat-treated in varying proprietary ways. Nor is it clear that, even from a Young's modulus perspective, that one can compare cross-sectional areas just by knowing the respective diameters. The actual cross-sectional areas are the sums of the the cross-sections of the fibers, which do not occupy all of the main circular cross-section and may themselves be of different diameters, depending on the manufacturer and the rope diameter.

Tests by Attaway seem to verify that the entire system, during extension, does behave in an essentially linear way, so there is a system stiffness that is well-characterized by a Hooke's law constant. (This is in contradistinction to some of the pure rope load-elongation curves, obtained by slow pulling rather than dynamic loading, that suggest linearity falls off at either end.) The relation between the system stiffness and the rope stiffness with accompanying damping coefficients is not clear, as far as I know, (and I really don't know very much!) Perhaps the answer lies in Pavier's rope model paper, which I have only perused.

All of this just adds up to saying, as Del has already observed, that a simple Young's Modulus argument may not be decisive.

I don't think Jim Ewing's tests are the first to suggest that there may be little difference in the maximum impact forces for different diameter climbing ropes. I believe that the CAI section on Materials and Technique found similar results. I also think we should all be grateful to Jim for the testing he is able to do on his own time, and be very restrained about demanding more results ever, not to mention right away. His work is pro bono in the interest of the climbing community, and it is unseemly to suggest that he is in any way obligated to do more.

How does one explain the subjective climber's sense that half ropes provide softer catches? First of all, one cannot discount the psychological effect of myth. How many people take exactly the same fall on a strand of half rope and then on a full rope? Mostly, I suspect that people are saying something like, "wow, that was softer than I expected..." whereas in fact what they expected was a softer catch. So I am not persuaded that some of the things that all climbers "know" are actually true.

I am also not persuaded that some of things "known" by engineers are actually true. We have the Tacoma Narrows Bridge, the Ford Pinto, the space shuttle Challenger, and Kansas City Hyatt Regency Walkway, for example, to remind us of their sometimes catastrophic fallibility. On the other hand, people who place all their faith in experimental evidence typically understand neither experiments nor theory. One needs both.

The CAI hypothesized that half ropes slip more through the belay device, thereby reducing peak impacts, but that doesn't seem to correspond to the vast majority of practical catches when little or no slippage occurs. However, I suspect that most belayers are not conscious of what the CAI calls "inertial" slippage, which occurs when the brake hand is drawn towards the belay device without any rope running through the brake hand. Since this is the first thing that happens and typically just precedes the moment of maximum impact force, it is conceivable that this type of slippage does play a role in reducing peak impacts with a half rope without the belayer even realizing it.

It also seems possible that half ropes, used properly, make fewer bends through all the intermediate carabiners, so that the ability of distant sections to participate in Hooke's law energy absorbtion is greater than it would be for a single rope. (Remember that friction is exponential in the bend angle, so that small differences could be significant, especially cumulatively.) Since the climber experiences system stiffness, not rope stiffness, and the bends around biners contribute to system stiffness, it seems plausible to me that the perceived softer catches are an artifact of straighter rope paths.

Another issue, by the way, is that it takes force to bend a rope over the top biner, and that too will detract from the full rope length's elastic capability. Smaller diameter ropes will need less bending force.

Finally, one might wonder if the subjective sense of softness for half ropes, even if it is not based on prior expectation, might be possible even though the impact forces are the same for half and full ropes. John has rightly asked what that subjective sense of softness actually is.

One claim I'd like to see documentation for is that the UIAA testing drives the rope into the plastic deformation range, making the results less relevant to smaller falls that are held elastically. Note in this regard that one has to distinguish between plastic deformation and the effects of damping, which might make the rope recover its initial length rather slowly, without however having undergone plastic deformation.

tradmanclimbs

Ice climber
Pomfert VT
Apr 29, 2009 - 08:04pm PT
RG, I would argue that precieved softness is just that, precieved. There is no way to prove or disprove the level of precieved softness. I do know from several decades of experience that most falls are softer than we expect them to be. Often we stress over how bad it would be to come off right here and then we do fall and its no big deal. WOW! that was soft and easy. Guess I will go up and send now,. This holds true regardless of the rope system be it Single , half or twin. This is a big part of Arno's Warrior way theory. My problem with the Just let go theory is that when I get cocky and lose my concerns about falling everything is just fine untill something goes wrong. I have learned over the years that while most falls are softer and safer than expected a few falls are much, much worse than expected but that is for a diferent thread.

Allmost Without ecxception the falls that felt hard to catch or really yanked me were either sport falls on the first or 2nd bolt or short trad falls close to the ground. 8ft fall on 20ft of rope kind of thing.

I did have one hard longer trad fall when gear ripped that felt pretty hard. 25ft fall on 50 ft of 10.6mm Sterling marathon rope, ripped 3 pieces. I felt that with doubbles I may have been able to keep the direction of pull correct so that the 3rd piece may have held. The first 2 pieces were gonners regardless of what I did short of an intrevention from god..

The point of all this is that I nor anyone else can prove that one fall FELT softer than the other unless there is a drastic diference in the type of fall. We can tell the difference between the feel of a factor 1 fall and a factor .15 fall but not the difference in in those same falls experienced with diferent rope systems. Especially if the events happen weeks, months or years apart and are not the exact same falls.

My last fall on doubbles was caught on a single strand of 8.8mm sterling marathon half rope. I had close to 100ft of rope out nd fell 10 or 12 ft. man that was one soft fall. My last real fall on a single rope was a bout 10 or 12 ft on 60 ft of 10.2mm Beal rope. That one felt really soft as well? which was softer? I honestly couldn't tell you.
Dr.Sprock

Boulder climber
Sprocketville
Apr 29, 2009 - 10:45pm PT
OK, see if this summary makes sense:


Long Fall 80 feet - 100 kg drop test:

8 mm static will stretch the least = 5.75 meters and 4.5 kN
then a 10 mm static = 8.25 meters and 4.8 kN
then a 11 mm dynamic = 8.75 meters and 4.10 kn
then a 8.8 dynamic = 11.25 meters and 3.54 kN



Short Fall 6 meters - 100 kg drop test

8 mm static 3.85 meters and 6.6 kN
10 mm static 4.2 meters and 7.3 kN
8.8mm dynamic 5 meters and 5.5 kN
11.0mm dynamic 5 meters and 5 kN
Dr.Sprock

Boulder climber
Sprocketville
Apr 30, 2009 - 08:42am PT
i think the small static line is kind of like clothes line, you know how when you pull on clothes line, and it stretches like crazy for a short time, then gets tighter than heck, right before it snaps.
i am afraid that is what we are seeing with the droop figures.

are the kN figures different at each end of the rope?
the harness has webbing, and the body absorbs energy, but the top anchor is solid, so there are some non linear things happening along that rope during stretching?


see, i was smart enuff to the grunts do all the work, all i have to do is mouse around. leaves more climbing time.
this took me 5 minutes to search:

(pdf is easiest on a 600 by 800)


http://209.85.173.132/search?q=cache:7pMKITus-3wJ:www.mra.org/services/grants/documents/Using_low_stretch_ropesFinal.pdf+a+comparison+of+stretch+forces&cd=1&hl=en&ct=clnk&gl=us
Osmo

Trad climber
Calgary, Alberta
May 5, 2009 - 12:04am PT
Wow, you guys!--what a lot of great discussion!

The rope is being dissected and it's obvious that there are a heck of a lot of angles to that simple four-letter word. On the other hand, I'm pretty sure that only very few of the characteristics and differences are significant. But in any case, as I said at least a couple of times before, when comparing impact forces in ropes of different sizes, they really have to be the same TYPE of rope: same polymer, same heat-treatment, same manufacturer, etc., so when we see a list of rope sizes and impact force/elongation combinations, we can only hope that the tester really cared to be fair by using only ropes of the same materials, as the numeric results quickly become impossible to correlate with each unrelated difference that's thrown into the mix.

As for effective cross-sectional areas, it's true that different ropes have different densities, and I think it may have been from Beal that I most recently saw a comment that a more accurate way to rate rope diameter is by weight per unit length, which I've considered for a long time, since seeing how some ropes were tightly woven while others were quite loose. Another practice used to address the same problem is to tension a rope somewhat while measuring--apparently you should know the approximate diameter of the rope and apply a tension proportionate to the X-section area.

I don't think Jim Ewing's tests need to be defended against perceived criticism, from me or anyone else: clearly he does the tests prescribed by the UIAA, which definitely have a good purpose, and I'm sure it's clear that I applauded his extending the 80kg tests to half ropes, plus who knows what other tests he does? And I don't think my comments to him can fairly be taken as any kind of a demand. A suggestion is another thing, and surely reasonable in view of the apparent confusion among climbers, about impact forces. And besides, it may be easy enough to rearrange a drop tower to investigate impact forces resulting from realistic fall factors--if so, what could be the harm in a suggestion like that? I think Jim E. can take care of himself. However, I was serious about doing some of my own testing, and will look into it as soon as the ice is out of the creek.

A lot of good comments also passed on the subject of 'softness' of catches. (One thing I noticed is that little if any mention was made of the two different views of a fall: that of the climber and that of the belayer, but I think most climbers realize that the major impact is on the protection, then on the climber, and finally on the belayer, unless there is no protection.)

In any case, it seems to me that there are two main components to the softness or hardness of a fall experienced by any component in that chain of protection: one is the peak force, and the other is the impulse, which is basically the product of the force and its duration.

It could be that a peak force seems softer if it takes longer to build up and then release, as in the case of a long fall with the same fall factor as a short fall. A couple of people have mentioned that falls that seem hard are commonly short ones--think of the difference between someone jabbing you with a finger, and then putting the same finger against you and pushing hard: the jab will likely get your attention more than the push, even at the same force. On the other hand, if there's any difference between the effects of the two impacts on protection, if a piece is marginal in respect of the impact force, the long fall/long impact duration is more likely to tear it out than is the brief impact.

The Psychological effect of myth is an interesting point, too, and worth considering, but then, just how does a myth get started? Is there a difference between BEING happy, and just THINKING that you're happy? Is there a difference between a soft fall-stop and just THINKING that it's soft? Although it may be true that very few people fall often enough to be sure of a fair comparison of impacts from different sizes of ropes in similar fall situations, I have no doubt that if you took a fall on a thin rope and expected a soft stop, but instead got a bone-jarring yank and hurt your back, you would realize that it was a hard stop, no matter what the rope looked like--so I just don't buy the "expected soft catch" concept very much.

And I assure you that whenever I say that "I" or "all climbers" "know" something, I'm always pulling someone's tail to some extent, because I'm well aware that it sometimes happens that things well-"known" turn out to be a bit less than completely true.

And that even applies of course to things "known" by engineers, though the Tacoma Narrows Bridge is possibly the only fair example mentioned, of engineering 'in discovery'--that's the thing about engineering, like ALL science: it's always developing and improving, and I doubt you could find an engineer anywhere, who claims to know everything.

The Ford Pinto was largely an issue of esthetics and quality control, and yet, I know a couple of guys who even now, many years and several cars later, still nurse fond memories of their old Pintos as the all-time favorite, so maybe the designers and even the Engineers, got something right on it; the space shuttle Challenger was a disaster, not of engineering, but of political interference, and the Hyatt Regency Walkway failure resulted from on-site exchange of materials by the contractor, rather than bad engineering.

True enough, experimental evidence and engineering are not separate fields at all, though some people who don't realize it, love to claim that they're unrelated. After reading some erudite comments on ropes in the last several posts, I suspect that I'm not the only engineer contributing to this forum anyway, though no one else is owning up to it.

And finally, someone mentioned Pavier's rope model, but unfortunately, I actually went climbing, and so haven't had much chance to look it up, and haven't found it yet--very interested to see what it is. I only hope it's very simple, as a simple approximation would almost certainly be adequate (and so, BEST) to describe the behavior of ropes as climbers see them. Unfortunately, such models tend to be overblown because they naturally become vulnerable to criticism if they neglect a number of characteristics, even if those are negligible in the overall performance of the device--the climbing rope in this case.
dirtineye

Trad climber
the south
May 5, 2009 - 02:27pm PT
Someone please throw in Impulse as a consideration in the GREAT Softness Percetion Debate, LOL.

And, don't you just think even a little that spreading the force out over a longer time would make it less JERKY?

THe way I used to understand it, Jerk was a term for third derivative, and had to do with, well the actuall jerk that you get when you yank on somethign hard and fast as opposed to long and slow. Seems like that would have application here as well.

tradmanclimbs

Ice climber
Pomfert VT
May 5, 2009 - 02:53pm PT
seems pretty clear that what we thought to be true is not. Clipping a single 1/2 rope to a manky piece is not a get out of jail free card. You do however have better tools with the 1/2 rope system for dealing with mank. easier to equalized with the 2 ropes and easier to have correct direction of pull. just don't kid yourself that the forces are automaticly lighter just because you are useing doubbles. You can MAKE the forces lighter by useing the system correctly.

Furthermore My pet peeve and the motovating factor for me throwing a bone in this debate is DON'T effin tell me that I am gonna die because I ocasionaly use doubbles as twins when the gear is bomber.
del cross

climber
May 5, 2009 - 03:43pm PT
Osmo, the Pavier paper is titled
"Experimental and theoretical simulations of climbing falls"
Here's a clip from it showing his rope model in schematic form:





While I'm posting pictures here are some drop test force/elongation curves (single ropes):






http://www.mra.org/services/grants/documents/Beverly_Sequential_Falls2.pdf




Woo woo woo woo!


Whitehorse Jeff

Trad climber
Fairfield, CT
May 5, 2009 - 03:58pm PT
In answer to the oft repeated question:" Why do they test half ropes singly with only 55kg", I was the American delegate (of the AAC) on the UIAA Safety Commission when the Half Rope Standard was put in place. Tests done at the time by Pit Schubert of the DAV (German Alpine Club) showed that any half rope that would withstand 5 UIAA test falls with a 55 kg test mass would also withstand one UIAA test fall with the 80kg mass. The argument presented to the members of the Commission at the time was that it would be impossible to get the lighter ropes which climbers (and guides ) wanted, to pass a harsher test, and that the real goal was to insure that a half rope would sustain at least one of the worst imaginable falls in the field, that being the fall represented by the UIAA single rope test. The repeated falls caught with the 55kg mass were accepted as the minimum repeatable test standard to insure this desired result. Over the approx 20 years that we've had the half rope standard , the Standard has proved to be high enough. (before the UIAA Standard was approved, people just climbed on half ropes without UIAA approval, assuming that both ropes would never be cut at the same time in the same fall, which has proved to be true in practice).
I accept that this reason may seem less than scientific to many. It was based on many tests carried out by the different certified UIAA test labs at the time, and as I remember was passed in near, if not total, unanimity by the voting members of the Commission, National delegates and Rope Manufacturers alike. There is one thing that encourages me at present as to the wisdom of this decision at the time-- rope manufacturing has made huge progress over the past 20 years, and this test still seems to hold up. Modern half ropes are much better than the ones I first used in France and Great Britain in the 70's.
rhyang

climber
SJC
May 6, 2009 - 06:51am PT
Very interesting.
That Darn French Guy

Trad climber
Santa Clara, CA
May 6, 2009 - 04:33pm PT
"any half rope that would withstand 5 UIAA falls with 55 kg would also withstand one UIAA fall with 80kg"

A-ha!
So a double rope *is* meant to catch a fall on a single strand.

The problem of that spec is everything is reported at 55kg: An 80kg person doesn't know what increase in force and elongation can be generated and IF IT IS STILL SAFE for his back.

Since we have ropes that are rated twin/double/single at 9.2mm, they shed some light there:

Joker:
55kg - elong 32% - force 6.0kN (double)
80kg - elong 37% - force 8.2kN (double)
+46% - elong 16% - force 37%

So can I expect to read a double's spec and say if it's rated 8kN at 55kg, then my max impact force for my 80kg ass will be a hefty 11kN?
del cross

climber
May 6, 2009 - 05:25pm PT
80kg? Did you gain weight, Dan?
Whitehorse Jeff

Trad climber
Fairfield, CT
May 8, 2009 - 10:01am PT
"The problem of that spec is everything is reported at 55kg: An 80kg person doesn't know what increase in force and elongation can be generated and IF IT IS STILL SAFE for his back."
The main concern is that the rope will hold one Factor 1.78 (or so) fall with an 80kg mass. My main point in leading is to avoid such severe falls, especially since even without a pack or a rack of gear I always exceed the 80kg mass weight. I accept that falling off is likely to be DANGEROUS for my back or other parts. I use a rope so as to still remain attached to the part of Mother Earth I am attempting to climb.I also accept that climbing is not really Safe and that falling off is often quite Unsafe. I don't mean to be flippant-- our activity (addiction?) is a "fine sort of madness" isn't it.
tradmanclimbs

Ice climber
Pomfert VT
May 8, 2009 - 01:37pm PT
Jeff we all know that climbing is dangerous but it seems to me that the origional thiought process was a bit skewed. Man these ropes break way to fast when we use the 80KG weight so we better make it lighter. That may not have been the intention but that is certainly how it looks.
Osmo

Trad climber
Calgary, Alberta
May 23, 2009 - 10:23pm PT
Things have been quiet on this thread for quite a while--everyone's cooled off. But quite a few guys have questioned the 55kg tests for half-ropes over time, and I'm not sure that they know yet, that there's a very good and valid reason for the 55kg. A comment like this last one from Tradman is a cute anecdote, but may only confuse them even more, as it's not true at all.

But "Francis" got the explanation straight from the UIAA about a month ago (Apr. 20, 2009), to the effect that the UIAA standards require a 'single' rope to hold at least 5 test drops before breaking; and they require a HALF rope to hold at least ONE drop in the same test, because it typically holds an entire fall on its own in double-rope climbing, when the second-last piece is some distance below the last one. Now here's the point: one is an awkward number because if the rope survives one drop but breaks on the second one, it could be that it BARELY held ONE, or it could be that it NEARLY held TWO, or anything in between. It would be nice to know a little more, since conditions, age, or manufacturing irregularities could push the result over the line at either end, particularly below the one-drop end. So the UIAA looked for a drop-weight that would abuse the rope the same amount in 5 drops as the 80kg would abuse it in ONE. That turned out to be about 55kg.

Now the testers can drop away, and have more data to compare between different ropes or different chunks of the same rope: if a particular rope never breaks on the 4th drop, and sometimes makes it to 7 or 8, they can say it's definitely a solid half-rope. But if it sometimes breaks on the 3rd or 4th drop, they may eye it suspiciously, and re-rate it as a twin or send it back to the lab for beefing up.
Chicken Skinner

Trad climber
Yosemite
May 23, 2009 - 10:29pm PT
Smartass answer. Shorter pitches.

Ken
old toad

Trad climber
yosemite, Ca.
May 24, 2009 - 08:58am PT
WBraun

I climb on a single 9.2mm rope now....

Werner, you don't need a rope!!!
jstan

climber
May 24, 2009 - 10:22am PT
And here I thought this was going away. This isn't about physics. It is about
whether you will need protection at the level of the UIAA drop test.

What seems to be happening here for simple technical rock is the UIAA is
counting on the other half rope as a backup for those cases where a half rope
fails a standard 80Kg. single drop test.

If so then anyone who actually needs protection at that level also needs to think
carefully as to whether the half rope setup is right for them. For now you have
to start worrying about placement positions and/or clipping as a twin.

For simple technical rock where you really are accepting these kinds of falls use
two singles. In alpine climbing where rope cutting and weight are issues and
there is not much protection to start with the logic might tend to weigh in on
the twin or half rope side where being able to rappel long distances is also a
big plus.

Bottom line, a purely technical rock climber whose eyes are not crossed can
make some use of this alpine technology.

If your eyes are crossed, think twice.

Seems to me.
jiimmy

Boulder climber
san diego
May 25, 2009 - 02:24pm PT
sounds like wisdom is .4mm
GreatLakes

Trad climber
Chicago, IL
Sep 10, 2010 - 06:54am PT
Being completely new to the sport and also an engineer....a certain calm comes over me when I explore the different ropes and techniques. I can't seem to find the answer to one question though. How do I tie a half rope system into my harness? I'm assuming two figure 8's would put a torque on the harness and could cause a dangerous situation. Please let me know what knots and how you tie in using half ropes and twin ropes if it differs. Thanks in advance for the insight.

I would also appreciate any names of reference books/websites that detail out the half rope system.
rhyang

climber
SJC
Sep 10, 2010 - 07:54am PT
You just tie in each rope (whether half or twin) to your tie in points the same way you tie in with a single. Though with half ropes you want to pay attention to left vs. right ropes being tied in the same way for both leader & follower. Not sure about reference books .. I learned from more experienced partners.
GreatLakes

Trad climber
Chicago, IL
Sep 13, 2010 - 10:27am PT
Top roping question: When taking my wife and kids out I’d like to top rope with two ropes.
1. Should I set up two separate anchor systems?
2. I weigh 230lbs so the rope is being punished when I’m in the air but does it really matter if I use a single(double), half(double) or twin(double) for top roping?

Leading:

3. When leading, why can’t I just use two singles while using half rope technique? If I stager the protection shouldn’t the load mainly be on one rope anyways?
taptaptap

Trad climber
mass.
Jan 14, 2014 - 10:41am PT

For the physics minded, the journal article about double ropes has been written:
B. Ernst & W. Vogel, "Determination of the redistribution shock load in climbing double rope system"
http://www.sciencedirect.com/science/article/pii/S1350630708001246
If you don't want to pay the big bucks for the article, see if you can get a free copy through your local library.

Regarding the question about the use of multiple "single" ropes, the question becomes one of finding a sweet spot where everything works OK. For ropes to work, they must simultaneously not stretch too much, must keep the force on the anchor & the deceleration of the arresting climber down to a dull roar, and not sever during fall arrest. The use of multiple "single" ropes will increase the force on and the deceleration of the arresting climber. If handled intelligently dual "single" ropes will PROBABLY work out without surprises for a top-rope situation where the anchors are reliable. BUT, it is possible that such a system will push things outside the sweet spot where everything works OK and challenge the anchor and/or the climber with unexpectedly high forces. Hence, no "sound practice" can recommend dual "single" ropes.
rgold

Trad climber
Poughkeepsie, NY
Jan 14, 2014 - 11:30am PT
It is worth noting that the article referenced appears, from the list of figures, to deal with one strand of a twin rope system failing. It does not (for good reason) consider the multitude of scenarios that might arise in half rope technique.
Big Mike

Trad climber
BC
Jan 14, 2014 - 06:12pm PT
First of all, thank you for the very interesting discussion. Lots of interesting info here.

I've been climbing for more than fifty years and I think I need rope stacking lessons. When I flip one of those piles, I get the mother of all Gordian knots half the time.

I got a little rope trick for anyone who has ever had this issue. I simply stack both ropes over my personal anchor,starting with really long loops, which each loop progressively shorter than the next. This way, the next loop you stack won't cross under the previous loop which is what causes snags.

So start with six or seven foot loops (or longer if you can) and work your way down to six inch loops by the time your partner reaches the belay. If you do this correctly the rope will flip perfect every single time. The most important part is paying attention to the length of the loops as you belay.

This trick works real nice for single ropes too.

Also never stack the ropes seperately. Treat them as one.
Big Mike

Trad climber
BC
Jan 15, 2014 - 08:15am PT
Bump
Doug from Hobart

Trad climber
Tasmania
Mar 4, 2014 - 10:33pm PT
I also use your "rope trick" Big Mike. Works well as long as you are careful with the stacking, otherwise you can end with a monumental mess.

On another note, I'm looking at getting a new set of half ropes. Currently using 8.0 mm Mammut Pheonixes which I've had for a few years and been very happy with, but they are about ready for replacement.
Pluses: at 42 gms/m they are the lightest ropes I've found; they've been pretty durable despite their thinness; less bulky in the pack.
Minuses: They do seem to tangle more easily than previous ropes I've used; fall rating is lower than other half ropes.
Anyone out there got any comments/suggestions? Anything new on the market I should look at?
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