Rigging with slings

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Rigging with slings

Postby GoHighGoDeep » Jun 18, 2006 5:12 pm

Just thought I'd see what people out there thought about rigging with sewn slings/runners from natural anchors (trees, BFRs, etc.). I was rigging a pit recently and one of the people I was with was questioning the strength of my BD 10mm Spectra slings as an anchor around a tree, even though they're rated at 22kn (1kn = 224.81 ft/lbs).

Here's my thinking on this. Sometimes its a heck of a lot easier to sling a tree than attempt to fiddle with tensionless hitch around a tree, particularly if the tree is in an awkward place to rig. Using a biner and a fig-8 knot to connect to the slings, and having to work the knot out afterwards isn't really a big deal, especially if you're using fairly stiff, and/or large diameter caving rope...10 or 11mm.

I also use the same type of slings for climbing, and slinging trees for protection is a well accepted practice, following a couple of generally accepted guidelines: Tree is living, and it's over 3in in diameter. This is in a situation wherethe tree/sling would be put under a dynamic load that would probably well exceed any forces put on such a set up in a relatively static load situation, such as caving. That said, I would certainly be using a larger diameter tree in caving.

I'm not intending to get into a discussion of natural anchors and their pros/cons, etc. I'm more interested in thoughts/insights/facts regarding use of webbing/slings for rigging from natural anchors.
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Postby hank moon » Jun 18, 2006 5:18 pm

no problem using slings (done correctly, bien sûr!). But...the tensionless hitch habit is kinda silly sometimes, esp. if you have an 11 mm rope. Go with what works for the situation. Help save trees - use a bowline on a coil!

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Postby GoHighGoDeep » Jun 18, 2006 5:23 pm

Oh, I've definitly done that too! Rigging has got to be adapted to each situation... no magic bullet!
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Re: Rigging with slings

Postby mgmills » Jun 18, 2006 5:30 pm

GoHighGoDeep wrote:I was rigging a pit recently and one of the people I was with was questioning the strength of my BD 10mm Spectra slings as an anchor around a tree, even though they're rated at 22kn (1kn = 224.81 ft/lbs). . . .
I'm not intending to get into a discussion of natural anchors and their pros/cons, etc. I'm more interested in thoughts/insights/facts regarding use of webbing/slings for rigging from natural anchors.


I'd have no problem with that rigging. . . provided it was high enough on the tree to allow for an easy lip :-) . I've seen lots of in-cave drops to natural anchors rigged that way (especially in frequently done pull-down caves where the slings are left in place)

I've not seen too many people rig trees that way because it usually isn't that big of a deal to do a tensionless wrap. In thinking about it though it probably is easier to pad the tree using the sling. I always fight with the padding when trying to wrap the tree.

Another thought is that a lot of my friends like to use really big trees as rig points so you'd have to have a long sling to rig that way.
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Postby speloman » Jun 18, 2006 5:32 pm

I also see no prob with using slings. I tend to use webbing (doubled of coarse) with a Double Fig of eight on a bight on the main line. But I tend to rig with tensionless most of the time. I like tension less because it keeps the tension off the knot. But I like slings because they keep the rope protected and free of sap (If around a tree). If your going around any tree rock or any thing you should have protection around it any way. Plus webbing is cheaper to replace if damaged. Just make sure to Double up. (My opinion)
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Postby mgmills » Jun 18, 2006 8:57 pm

speloman wrote: I tend to use webbing (doubled of coarse) with a Double Fig of eight on a bight on the main line. . . . . Plus webbing is cheaper to replace if damaged. Just make sure to Double up. (My opinion)


Just curious about what kind of knot do you use to tie your webbing slings? The only problem with tied webbing slings is that I've seen knots in webbing slip. I was taught to tie webbing slings with a double laced waterknot with a long tail as security in case of slippage. I really like the sewn webbing slings and they really aren't that expensive.
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Postby speloman » Jun 18, 2006 10:26 pm

I use a Water Knott. Basicly a overhand follow thru and I do leave a long tail and sew the ends or tie a safety. I have found that sewing them work better. I have not noticed any slippage in the water knot but usually when you load it is a son of a gun to get undone if you want to untie them.
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Postby fuzzy-hair-man » Jun 18, 2006 10:57 pm

We use a Water knot and have never noticed any slipping. You could also put a couple of half hitches in the tail ends for extra security or tie a water knot (overhand knots) in the tails so it can't pull the tail through the knot. Never really been a problem though...

What sort of tape do you use ? 2" flat or 1" tube tape ?

Personally I find knotted tapes more reassuring that sewn slings. If the stitching isn't done right it isn't very strong, and if the stitching has worn then it is a problem. So I would think sewn slings would be less versatile(you cannot change the length), more prone to wear(at stitching), more expensive, but somewhat more convenient.

If you want some slings just cut some tape and make knotted slings.

My opinions only :oops: :grin:
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Postby speloman » Jun 18, 2006 11:36 pm

I use 1in tube webbing. I agree with Fuzzy hair man about the stiched slings. Though We use them on the mine rescue team we are very carful with them by inspecting them and have them backed up with 1in tube webbing. I guess it is a prefrance of the rigger and the users. I feel safe with stiched slings because I inspect them before and after use (as I would with any of my gear) and don't use them if they don't look right.
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Postby NZcaver » Jun 19, 2006 3:15 am

:exactly: I prefer tied tubular webbing over sewn slings as well, for the reasons already mentioned. :caver:

Fuzzy - I don't think I've seen 2 inch flat webbing used to anchor a rope before, it's pretty much always 1 inch (25mm) tubular. I also have some of that smaller 11/16ths (18mm) tubular webbing that climbers use, but I don't use it to anchor ropes.

The Water Knot (aka Tape Knot) is really about the only knot that should be used in webbing, and of course make sure you leave generous tails (or half hitches). There's also the Beer Knot, but that's not one you want to tie/untie very often (very time consuming). I believe the usual cause of a Water Knot loosening is when it's used in more of a climbers belay rope anchor configuration - ie moving around a lot without having been pre-tensioned first by the weight of cavers rappelling a pit.

I often anchor my ropes with webbing, mainly because I have lots of it in pretty color-coded lengths. Although sometimes I just use a tensionless hitch instead. A single piece of tubular webbing looped around a tree and properly tied should be no less strong/safe for normal loads than your average caving rope with a knot tied in it. Of course, doubling the webbing makes it stronger - and more importantly easier/more practical to work with (if you have enough length available).

You can pre-tie a loop of webbing, then wrap it around the tree clipping into the 2 halves at the front. Or you can do a wrap 2/pull 1 (or rescue wrap 3/pull 2) which has the added bonus that the Water Knot (if properly positioned) has very little tension on it due to the surface friction of the anchor rock/tree/etc. Just make sure the angle of the webbing clipped into the carabiner does not exceed 45 degrees (and preferably is less than 30 degrees).
Last edited by NZcaver on Jun 19, 2006 4:04 am, edited 1 time in total.
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Postby Ralph E. Powers » Jun 19, 2006 3:38 am

I myself have never known or heard of a properly tied and DRESSED water-knot coming loose or undone. Same with a figure 8 knot done in the same manner.
All knots; whether with webbing or with rope should be pre-tensioned before use. They should be dressed so that the full advantage of their strength can be utilized. One should be able to descend and ascend on said knot with confidence that it will hold even the weight of two (tandem) climbers.

It's just plain common sense.

As far as slings goes... I haven't used one in a while. I was initally taught that using a wrap three pull two was an excellent anchor around either a bomb-proof rock or tree. The (water) knot used on 1-inch tubular webbing should be at the back of the anchor. If there isn't sufficent webbing to wrap three then wrap two pull one is suitable.
But as of late I've relied on the tensionless knot for my rigging and will only resort to the wrap 3 pull 2 during (self) rescue rigs... which in-of-itself has been a extremely rare occurance.
Most of the rigs (here in Utah) are around bomb-proof rocks (no cracks anywhere) or around trees with greater than 6 inch diameter and of course they're living trees. Anything less would require a bolted anchor.

Unfortunately as most of the trees are usually shrub-oaks or stunted pines/junipers the rigged knot cannot be done very high and the rope tends to run on the ground til the lip of the drop. Here we pad heavily and where needed. I for one am somewhat envious of the cavers back east who have the luxury of tying their ropes at waist or head height to facilitate getting over the lips of the main drops. Here it's just not always possible. Still we manage. :grin:
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Postby NZcaver » Jun 19, 2006 4:21 am

Ralph E. Powers wrote:I myself have never known or heard of a properly tied and DRESSED water-knot coming loose or undone. Same with a figure 8 knot done in the same manner.
All knots; whether with webbing or with rope should be pre-tensioned before use. They should be dressed so that the full advantage of their strength can be utilized. One should be able to descend and ascend on said knot with confidence that it will hold even the weight of two (tandem) climbers.

It's just plain common sense.

:yeah that: Amen!

Along with that, I am constantly amused and/or irritated by those who say you must tie a backup knot after a figure-8 in order for it to "be safe". Wrong! But if your rescue team or whatever says it's true, then it must be... at least for those operate without their own brain. In one situation, I heard a so-called rock climbing instructor tell students that an 8 always needed to be backed up, but a Bowline didn't! A gentle suggestion that she may have the two mixed up met with vehement denial. :roll:

...I was initally taught that using a wrap three pull two was an excellent anchor around either a bomb-proof rock or tree. The (water) knot used on 1-inch tubular webbing should be at the back of the anchor. If there isn't sufficent webbing to wrap three then wrap two pull one is suitable...

Actually, the Water Knot securing the webbing for a W3P2 (or W2P1) ends up at the FRONT of the anchor, directly against the rock/tree/etc. The other strand(s) of webbing are what you clip into, leaving the one wrap with the knot in it against the anchor. :wink:
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Postby Stridergdm » Jun 19, 2006 7:52 am

No one apparently has mentioned one great advantage of using slings over a tensionless rig.

Speed.

How often have you rigged your rope and dropped it into the hole only to realize the position is all wrong, that it IS in fact rubbing on that rock you thought it would miss, etc.

So now you decide to move it.

Now, you can unclip the binner, unwrap the tensionless rig, find another tree or position, wrap it, clip it in, etc.

Or, while you're unclipping the rope, have someone toss a pre-rigged sling around the better tree, move the rope, and voila, you're ready to cave.

I mean after all, we're here to cave right, not rig?

(Oh, ok, I admit some of us enjoy just the pure fun of rigging, but really, it's all to get into the cave, right? :-)
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Postby NZcaver » Jun 19, 2006 1:21 pm

Stridergdm wrote:(Oh, ok, I admit some of us enjoy just the pure fun of rigging, but really, it's all to get into the cave, right? :-)

Cave? What cave? It's all about the rigging... :laughing:
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Postby Ralph E. Powers » Jun 19, 2006 6:26 pm

NZcaver wrote:
...I was initally taught that using a wrap three pull two was an excellent anchor around either a bomb-proof rock or tree. The (water) knot used on 1-inch tubular webbing should be at the back of the anchor. If there isn't sufficent webbing to wrap three then wrap two pull one is suitable...

Actually, the Water Knot securing the webbing for a W3P2 (or W2P1) ends up at the FRONT of the anchor, directly against the rock/tree/etc. The other strand(s) of webbing are what you clip into, leaving the one wrap with the knot in it against the anchor. :wink:


This gentle suggestion is met with humility and a :doh: yeah you're right... in the front so you don't pull the wrong one... sheesh.

As far as the speed goes... I'd rather take my time in ensuring the best possible rigging and rigging point and to be able to rappel/ascend without that worry on my mind. There's enough to worry about during the rappel and ascent without adding: "hmm, is that rig really going to hold okay?"
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