Discussion Topic |
|
This thread has been locked |
JohnRoe
Trad climber
State College, PA
|
|
|
Topic Author's Original Post - Apr 9, 2010 - 11:04am PT
|
Hanging out on a clove hitch at a belay at Seneca last weekend (perfect weather) I was wondering about this...
Some people say that a clove hitch can slip under less-than-extreme loads (I think I've seen 1000lb quoted). I've never worried too much about that, but these statements are presumably based on biners made from round stock.
What about clove hitches on the newer I-beam biners (like this one: http://www.dmmclimbing.com/productsDetails.asp?pid=3&pid2=64). Would the non-convex profile of the I-beam make a clove hitch more or less likely to slip (or make no effective difference)? Any suggestions/data?
JohnR
|
|
Mark Hudon
Trad climber
Hood River, OR
|
|
If you're hanging off a power point on one clove hitch, why not simply tie another one directly up on one of the anchors. Two knots won't ever slide enough to make any difference.
|
|
steelmnkey
climber
Vision man...ya gotta have vision...
|
|
I've repeated that 1000lb quote in the past after reading it somewhere.
John Middendorf said he had personally done some testing and the 1000lb slip was a myth.
In any case, I've never had one slip.
|
|
apogee
climber
|
|
The AMGA perpetuated that statement (myth?) for many years. There were a lot of people backing up clove hitches because of it.
I've never seen one slip either- even ones that are sloppily tied eventually cinch down. In any case, in the application of attaching yourself to the master point, it's hard to imagine how you would create 1000 lbs of force on that hitch.
|
|
adatesman
Trad climber
philadelphia, pa
|
|
Clove hitches absolutely can and will slip under load prior to seizing. Here's a quick and dirty video I made of it a while back... Link to Youtube
Here's the force log that went with it:
Basically I took a length of 7mm accessory cord and hooked it up to the biners on the puller using clove hitches on each end. The cloves were hand tightened and left with 5 inch tails. Both cloves slipped prior to failure (lower clove seized and the cord broke there), with the upper one slipping 2 inches and the lower one slipping 1 inch prior to failure.
EDIT- Admittedly the majority of the slippage occurs at forces much higher than you get just hanging on it, but well within the realm of what can be generated if you fall on it.
|
|
apogee
climber
|
|
"...the majority of the slippage occurs at forces much higher than you get just hanging on it, but well within the realm of what can be generated if you fall on it."
Help my limited imagination understand how someone attached to a master point at an anchor with a clove hitch on a standard diameter lead rope could commonly generate 1000 lbs of force (or similar). Lead fall, steep wall, 30' out, no pro, factor 2 onto a static belay? OK, maybe, though pretty unlikely. Other suggestions?
|
|
kiwi
Trad climber
Olympia, WA
|
|
so does that mean I shouldn't aid solo with a clove? it looks like it might slide a little under load but not fail, providing more of a dynamic catch! anyone actually fallen on a clove? I've heard of people taking 40 footers onto them with no problem, but that was on here, no one I actually know.
|
|
adatesman
Trad climber
philadelphia, pa
|
|
You've got it, Apogee; monkeying around at a bolted belay with dyneema runners somehow manage to FF2 onto it. Not likely, but certainly possible. Dropping a pig on a haul line would be another candidate.
But my main point is that the slipping clove thing is not a myth; it can and does happen. Just not much of a concern for hooking yourself to the anchor since at those forces the slip is minimal.
|
|
rgold
Trad climber
Poughkeepsie, NY
|
|
Although the pictures look scary, one to two inches of slippage + tightening under high loads is of no concern. (You can get a few inches of tightening out of a figure-eight knot too, by the way.) In case the anchor is absorbing the impact of a factor two fall onto the belayer, slipping under tension will actually confer a benefit by absorbing some energy that would otherwise result in higher rope tension and so higher anchor loads.
Although a single data point is of no real value, I held a factor two fall onto the belay while anchored with a single clove hitch, which as far as I could tell afterwards did not slip at all.
I don't know what kind of cord was used in the video, but tests with climbing ropes have indicated that clove hitches in dynamic rope slip at much higher loads than clove hitches in static rope.
One also has to wonder about the ability of the short end on the upper knot in the video to rotate upwards freely; this enabled the upper knot to slip about twice as much as the lower knot and is not a feature of any anchor set-up, in which there is no short end and the strand in the position of the short end is typically weighted with a substantial length of rope.
None of this addresses JR's question though.
|
|
apogee
climber
|
|
"...that the slipping clove thing is not a myth; it can and does happen."
I'll defer to your research, but in the end, as always, it boils down to the judgement of using the right piece of gear or technique in the right place at the right time. To the OP's query, using a clove on a lead cord to tie oneself in at a master point is, in most cases, entirely reasonable.
Edit: After reading rgold's response, it appears my response is not really addressing the OP. Sorry about that.
|
|
adatesman
Trad climber
philadelphia, pa
|
|
I wouldn't call it 'research'; just someone asked about it a while back so I threw a piece of cord on the puller to show it in action (and put an end to the RC flamefest that was going on at the time arguing about whether it happens or not).
FWIW I've seen similar things using 10.something dynamic line as well, but don't have video or force logs of it. I agree with RGold to a point; some of it is due to tightening of the knot, but if you watch the pattern of the sheath you can see the unloaded end get sucked in as well.
EDIT- My apologies to the OP for the tangent as well. I think the closest thing to a I-beam biner I have is some CAMP Nano 23's... If you like I can throw some rope on the puller with those to see what happens.
|
|
mongrel
Trad climber
Truckee, CA
|
|
I always take test results that aren't precisely reflective of actual climbing situations with a big chaser of skepticism. For example, I like Dave's post, sounds exactly like what might happen at an actual real world belay station (I'd also be interested in different variations such as hand tightened as in a belay station with footholds or a ledge, hand tightened then actually body-weighted as in a hanging belay, and so on). But tests such as using 7 mm accessory cord aren't very relevant at all (unless you use that for a lead rope...?). Some situations, thinner cord locks better (prussik); others, it might lock up either better or worse or the same, due to the different geometry of rope bearing on biner stock.
|
|
Chiloe
Trad climber
Lee, NH
|
|
A few other points regarding realistic climbing vs. testing scenarios:
1) The testing results appear to involve continuous, gradually increasing force. What climbing situation could produce a similar force (thousands of pounds) applied slowly and continuously? I suppose we could invent one, like a huge block that slides off onto the belayer, but it's not a factor-2 fall. Drop tests would seem more realistic for evaluating clove hitch strength in anchors.
2) When I anchor with a clove hitch, the short end of the rope goes to me, and there's 58 meters or somesuch going off to the other climber or down the cliff. How on earth is a significant part of that going to slip, even if I manage to weight my end continuously with thousands of pounds?
3) Finally, as pointed out above, the clove hitch makes sense mainly as you tie off with your lead rope, which would be 9.2mm or more. Or two ropes, if you're using lighter doubles/twins. A clove hitch in one 7mm seems less obvious.
As for the OP question about how biner stock shape (or diameter?) affect a clove hitch, sounds like we don't know?
|
|
HighTraverse
Trad climber
Bay Area
|
|
A clove hitch relies upon friction around its anchor to hold.
Unlike a bowline for instance where the friction is rope-to-rope and the rope binds upon itself as it tightens.
Any 'biner other than circular cross section is definitely going to generate less friction with the rope in the hitch.
Only testing would reveal how much less. I've had a lot of experiences with half hitches in ocean sailing as well as climbing.
They will often slip briefly when shock loaded so the rate the load is applied is also a major factor. In fact if a flogging line is secured with a half hitch, it will frequently loosen the hitch so that the line pays out as it flogs.
With large diameter ropes and small 'biners I'm always concerned that the rope will work up into the gate area before it gets loaded. I don't know what would happen to the gate then if loaded. I try to avoid that situation. I think it could get very weird with wiregate 'biners
That may the the condition AGMA was concerned about with the loaded side of the hitch on the gate side.
Did the testing take this into account?
Clove hitch is a very handy knot. I'm always very careful how I use it especially in anchors. I want a Knot rather than a Hitch or a Bend as the primary anchor.
Remember it's intended use: fastened around a cylinder with a diameter significantly greater than the rope. When the rope is larger than the cylinder the bending forces in the knot tend to keep the knot loose and allow the knot to loosen if not continuously loaded.
I'm not surprised the 7mm rope held a high load.
|
|
Two Pack Jack
climber
The hills
|
|
I'm not a engineer studying this, but John Dill (YOSAR) says to tie in with an 8 everytime. With a couple seconds extra, and a little decent planning you will be stoked on an 8, because not only do cloves slip, but when they hold they have a much lower breaking point than an 8.
As for soloing, I always use a soloist or a gri gri. The soloist uses a big clove, dont know about slippage but it wolnt break nearly as easy b/c the larger cicrumfrance of the loop. Don't know how much safer these are, but I haven't died yet.
|
|
deuce4
climber
Hobart, Australia
|
|
Can't recall ever testing clove hitches specifically for slip. Did a lot of testing with hydraulic pullers on various stuff, but not clove hitches on carabiners. Maybe we did some tests in the context of the clove hitch on the silent partner, though. But probably not to 1000 lbs, as I wouldn't have wanted to damage my Silent Partner.
Were you thinking of our prussik tests we did with John Dill in Sedona? We tested various rope grabbing devices, and concluded that though Rock Exotica's Gibbs type device didn't shear ropes like the original Gibbs, Prussik knots were the safest for rescue.
|
|
JohnRoe
Trad climber
State College, PA
|
|
|
Topic Author's Reply - Apr 9, 2010 - 07:01pm PT
|
Textbook theory for a rope running round a rough surface says that the frictional force depends (exponentially) only on the total angle through which the rope turns - independent of the profile. But I'm pretty doubtful about the assumptions that go into that theory, in this case.
|
|
JohnRoe
Trad climber
State College, PA
|
|
|
Topic Author's Reply - Apr 9, 2010 - 07:04pm PT
|
ah, locker, i was waiting for that...
feel so much better now :-)
|
|
OR
Trad climber
VT
|
|
Ummmmm overthought I think.
|
|
caleb
Trad climber
asheville, nc
|
|
Hey there,
I would think with a biner of I-frame construction, as long as the negative space in the "I-beam" was less than the diameter of the rope, as is the case with most biner/rope combos, you wouldn't have much to worry about. If it were greater then I think you might have some issues. I'm imagining cloving an actual I-beam, like in a roof or something. I would think that would slip sooner. Allthough the clove's breaking strength increases to the strength of the line as the radius gets bigger, I can imagine that irregular shapes would negate this. On a post or a soloist, the radius is bigger but it's round, so zero problems.
Just a thought. I have absolutely zero "real" knowledge to base this on. Allthough it does make me wonder about that biner I cloved today on a roped solo. It was one of the newer, small wires. I had a heck of a time just getting the clove in my old fat 10.2 in there, let alone the smaller diameter of the biner as opposed to my rope. Anyway, just thinking out loud. Anybody here taken a fall while soloing onto a cloved piece that happened to be one of these smaller wires? Something I'm certainly thinking about now....
|
|
|
SuperTopo on the Web
|
Let us know!