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karups
Feb 27, 2008, 11:54 AM
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I'm interested in backing up top-rope anchors using a long piece of nylon webbing, e.g. to a tree pretty far from the edge. To double my range, I don't want to just use a water knot to create a sling. Rather, I want to create a loop at each end (one loop around the tree and the other for connecting to the master point with the other anchors)
What knot should I use to create such loops? It seems the only three knots recommended for webbing are the water knot, beer knot, and double/triple fisherman's. And the beer knot doesn't apply here.
The double fisherman's seems like it would do the trick, but I'm concerned about how hard it would be to untie after being weighted. (I haven't done it, so I just don't know.)
The only online reference I found mentioned using overhand or figure-8 knots for tying webbing to anchors (I presume the "overhand" referred to is the same as the water knot; but what about the figure-8 knot in webbing?).
I've also seen bizarre stuff like a Munter in webbing that is backed up by half-hitches. But I'd like some second opinions before I start trust my life to half-hitches. However, I do like the idea of knots like the Munter that can be tensioned down really well (e.g. if tying around a chock stone).
What do you think?
p.s. I apologize in advance if this just becomes a repeat of the "which knot is best for webbing" discussion. I'm primarily interested in any aspects that might be specific to this particular application. If the answer really is a unanimous "water knot", then that's easy enough.
(This post was edited by karups on Feb 27, 2008, 12:19 PM)
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binrat
Feb 27, 2008, 12:40 PM
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Some years ago I had the chance to test the following set up. It was tested on a slow pull machine with great results.
You already know the water knot, which is basically a overhand knot thats been traced with the other end of the webbing.
To great a relatively strong anchor, form a bite on the end of the webbing, then do an overhand knot on both parts of the bite at the sametime. This should create a loop at the end of the webbing with a knot looking simular to the water knot.
At the tree do a round turn (wrap the loop end around the tree 1 full wrap then back to the front)
Feed the non knotted end through this in the direction of the load. Make sure that the webbing is laying flat around the tree and not crossed over itself. The webbing coming from the tree should be straight towards the load, any deflection at the tree will lower the strength of it.
Next, at the load end repeat the overhand on a bite to the desired length of the webbing.
Remember that the strength is now around 12Kn+
Binrat
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swaghole
Feb 27, 2008, 12:46 PM
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Idealy, you should use a static line with a bowline (or doube bowline) for anchoring around the tree and a figure 8 on a bight at the other end for backing up the anchor.
I've never tried tying a bowline using webbing and I've never seen or heard about this being done. Maybe someone else has some input??
You could also tie a figure 8 on bight and loop the webbing aroung the tree the pass the webbing throught the loop of the figure 8. A figure 8 on a bight in webbing is fine - just leave long tails and dress it up properly.
(This post was edited by swaghole on Feb 27, 2008, 12:52 PM)
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rangerrob
Feb 27, 2008, 1:04 PM
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Actually, ideally you would watch someone experienced create this set up for you several times before doing it.
RR
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reg
Feb 27, 2008, 1:36 PM
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swaghole suggested static line - i agree. it's easier to work with IMO. i will loop or wrap the tree several times (3-5 times if i have the lenght) first. these loops create more then enough friction for the anchor to be solid as primary or back up. then with the remainder - after looping - i'll do a retraced 8 creating an 8 on a bight that captures the anchor side of the line.
i don't like the concept of a "backup" for your TR anchor. i think you should create a solid anchor that stands alone and/or any additional leads to the power point should be considered as part of the anchor and tensioned and joined equally to the PP.
i have several lenghts of 11mm static that i'll use in varing configurations wether from trees, B I G boulders or groupings of gear that i arrange to have two lines at the PP from independent anchors points - tensioned equally, usually sleeved with tape or otherwise protected over edges and two lockers or three non lockers, op&op. no "backups" - their not needed. 
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kevinwaldock
Feb 27, 2008, 2:03 PM
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i routinly use a fig 8 on one end, girth hitched round the tree then a fig 8 on the other end. like the others have said make sure there is long tails for yer knots, and place the girth hitch round the tree at the base of said tree. fig 8 i find are easier to untie then water knots. if there really stuck hit/roll on the rock to lossen it up. hope this helps
kevin
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blueeyedclimber
Feb 27, 2008, 2:51 PM
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I am curious what your main anchor is and why it is necessary to back it up. Not that there's anything wrong with that, but is the backup a necessity or is it purely for piece of mind? There are any number of ways to back it up to the tree, depending on what you have for equipment, but what's more important is you main anchor.
Josh
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microbarn
Feb 27, 2008, 2:55 PM
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kevinwaldock wrote: i routinly use a fig 8 on one end, girth hitched round the tree then a fig 8 on the other end. like the others have said make sure there is long tails for yer knots, and place the girth hitch round the tree at the base of said tree. fig 8 i find are easier to untie then water knots. if there really stuck hit/roll on the rock to lossen it up. hope this helps kevin
follow binrat's advice
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ja1484
Feb 27, 2008, 3:48 PM
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blueeyedclimber wrote: I am curious what your main anchor is and why it is necessary to back it up. Not that there's anything wrong with that, but is the backup a necessity or is it purely for piece of mind? There are any number of ways to back it up to the tree, depending on what you have for equipment, but what's more important is you main anchor. Josh
My thoughts exactly.
First, why is the backup necessary? Is there something suspect about the main anchor?
Secondly, I've found the easiest solution by far for top-roping setups is to just pick up about 100ft of 8mm Nylon cordage (sometimes you can find static rope on sale for even cheaper, and though it is burlier, it's also bulkier and heavier) and take it with you coiled on any top-roping trip. There won't be much in the way of natural features that can't be rigged with that. However, do be sure you have at least a double loop for all load-bearing portions of the anchor, as single strand knotted 8mm from most brands is about 8-10kN. You need it looped, at a minimum, to acquire sufficient strength. Hence why, again, some prefer to go with static rope.
(This post was edited by ja1484 on Feb 27, 2008, 3:52 PM)
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drfelatio
Feb 27, 2008, 4:03 PM
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swaghole wrote: I've never tried tying a bowline using webbing and I've never seen or heard about this being done. Maybe someone else has some input??
I've read about it being done on the anchor end of slacklines. I've used it a few times myself and didn't have any problems. It held up just fine and the rig tore down easily. Whether or not that information is relevant to TRing, I'll leave to higher authorities.
As for tying webbing around a tree, I've always just made an overhand knot several feet from the end of the webbing, then passed the end around the tree, and retraced the overhand. It can be a PITA to untie though...
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binrat
Feb 27, 2008, 4:47 PM
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to the OP:
If you are going to go with static rope then think about putting old 1"tubular webbing over it to protect it. At the load end simply tie a figure eight on a bite.
At the anchor end do a thing known as a tensionless hitch or "no knot". Prior to doing the hitch take out all the slack on the rope and construct the hitch by wrapping the rope around your tree 3-6 times. Make sure that the wraps are tight together and are dressed. Then do two half hitches around the rope going to the load. Then I always do a double over hand knot as back up ( that maybe overkill). Now you have a back up anchor with a strength around 20-24 Kn (depending on the rope)
Cracklover:
The one way that webbing fails is that it cuts itself by internal "pinching", and the way webbing maintains its strength in a knot is having the strands parallel to each other with max contact. If you properly dress the figure eight then it is good. Dressing the knot prior to loading does not always achieve this. It really has to be dressed and check while setting it.
Binrat
(This post was edited by binrat on Feb 27, 2008, 4:52 PM)
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altelis
Feb 27, 2008, 5:04 PM
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In terms of the figure 8 in webbing, this is what I remember learning (on my NOLS mountaineering trip)....
the figure 8 is just fine in webbing. the reason people prefer to use the overhand family of knots is that in webbing the overhand provides all the security of a figure 8 in rope and that the extra bends of the figure eight in webbing can make it a little harder to untie.
so, both are fine and an 8 is just a little overkill in webbing.
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Tree_wrangler
Feb 27, 2008, 5:33 PM
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Almost all of my anchors are like this....not so much "backed up" on natural pro, but requiring natural pro in concert with a couple pieces of gear to get a solid, equalized anchor point. It's not infrequent that I'll only have one or two good gear placements, so I'll bring in the closest tree, rock, whatever.....it's pretty usual that the best candidate is 30' or more distant.
I'd suggest ditching the webbing entirely and go with a static line as someone else suggested. I'd also suggest getting a piece long enough to use it to equalize your gear and natural pro into one anchor point, rather than just having it be a slackened leash to a tree.
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kevinwaldock
Feb 27, 2008, 5:47 PM
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Microbarn
soooooo why is it wrong to use fig 8 on a bight to girth hitch a tree with webbing? as long as the direction of load is alined it's good right? explain pls. thanks
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acorneau
Feb 27, 2008, 7:11 PM
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kevinwaldock wrote: Microbarn soooooo why is it wrong to use fig 8 on a bight to girth hitch a tree with webbing? as long as the direction of load is alined it's good right? explain pls. thanks
A tensionless wrap will be kinder to the tree (bark damage) than a single loop of 1"webbing. It also maintains full strength of the rope/cord/webbing whereas a girth hitch generally drops it in half.
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microbarn
Feb 27, 2008, 8:46 PM
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cracklover wrote: microbarn wrote: never use a figure 8 knot in webbing Why knot? Been tying fig 8s in webbing as long as I've been climbing, and never had a problem. And yours is the first time I've read that there might be. So... please explain. GO (edited to fix quotes)
My friend and I had a discussion about this in email a couple of years ago. Here is the text of one of his emails:
In reply to: See http://www.bwrs.org.au/research/ They tested 50mm flat webbing slings tied with an overhand knot. The webbing broke at 65% of its unknoted strength. They did observe the overhand knot roll over in rope, they did not observe that to happen in webbing. The abnormal figure 8 knot consistently rolled over in rope, so they stopped testing it.
The link doesn't work any more, but it seems to be present on the internet archive:
http://web.archive.org/...wrs.org.au/research/
It has been a while since I read it. Feel free to point out my errors, but these are my conclusions from the article and my experience.
A well tied flat overhand doesn't roll in webbing.
A figure 8 is very difficult to tie flat in webbing, and it rolls if it isn't flat.
The figure 8 has value as a tie in knot because of its ease in double checking. The Figure 8 is extremely hard to check in webbing
An overhand is very easy to tie and check.
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microbarn
Feb 27, 2008, 8:54 PM
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kevinwaldock wrote: Microbarn soooooo why is it wrong to use fig 8 on a bight to girth hitch a tree with webbing? as long as the direction of load is alined it's good right? explain pls. thanks
One poster above already mentioned that they are harder on the tree.
They are some of the worst knots for reduction of strength of the rope you are using. Frequently people assume a girth hitch that is tighter creating a sharper kink at the connection is better. This is actually a weaker configuration. If you are going to use a girth hitch, then the load bearing strand should be as straight as possible.
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