Improving rigging for descending?

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Improving rigging for descending?

Postby alfred » Nov 2, 2014 7:08 pm

Hi fellow cavers,

I'd need a couple of tips on how to improve (safety- and durability-wise) rigging when descending slopes and pits. I like my ropes very much so I'd prefer not to shorten their life too much by mishandling them.

I normally find trees or huge rocks nearby and throw my rope around one (it has a permanently tied eye on both ends, one to rig and one as safestop when descending) then circle it around enough to use a carabiner in the eyeloop and clip the "free" part I'd descend and pull onto.

Now, even if I don't plan to increase my caving difficulty level any soon, my thoughts are:

- would using a thimble (metal or plastic? I think the former would be rust-free, but I fear it may break under load and slice fibers in its way) be any better for the rope (spread the carabiner holding/pull on a wider area)?
- is rigging that way better than tying double fisherman's knots with the same end every time?
- if I'd use a webbing sling to rig the upper end of the rope, what would be the benefits since I think I'd still need to keep that end tied into an eyeloop?


Thank you very much


Alfred :cavingrocks:
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Re: Improving rigging for descending?

Postby caver.adam » Nov 3, 2014 9:20 am

Please look up "tensionless wrap" or "tensionless hitch" for rigging around a tree or rock.

I highly suggest getting a copy of OnRope http://onrope1.com/store/index.php?p=product&id=11&parent=3 to read about rigging.

Most people will also recommend taking a class or participating in a local club if you are so inclined.
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Re: Improving rigging for descending?

Postby caver.adam » Nov 3, 2014 9:22 am

If you decide to use webbing please look up the "wrap 3 pull 2" method. Also, you will need to know the "waterknot".

Once again OnRope will help with this.
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Re: Improving rigging for descending?

Postby caver.adam » Nov 3, 2014 9:24 am

And please, please, please, tell me you are climbing with a static rope specifically designed for rappelling and climbing? And using rated connectors (such as biners or screwlinks). Your comment about the thimble worried me. For recreation we use connectors rated to a minimum of 15kN. For industrial or rescue work they use a minimum of 22kN.
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Re: Improving rigging for descending?

Postby Tim White » Nov 3, 2014 12:57 pm

I think alfred is talking about something like this...
Image
Be safe,
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Re: Improving rigging for descending?

Postby alfred » Nov 3, 2014 1:35 pm

Thank you all for your answers.

Safety always comes first even in spare time, so I always do my best to stick to good measures in order to prevent injury or worse, so I appreciate your concerns.

I'm reading "Alpine Caving Techniques" by Marbach and Tourte. I've read most of "Life on a line" and I'll surely get a copy of "On Rope" whenever I can in the following months. Thanks again for the suggestion :)

I'm using a 10mm polyester rope whose minimum breaking load is around (a little over) 15x my bodyweight and 20kN carabiners with screwlock gate. As backup I've got a Prusik tied on 8mm cord.

I've read about the waterknot (and a few related knots) on "Life on a line" so I'm relatively familiar with that figure.

To Tim: yes, this is exactly the kind of thimble I was talking about, thanks for posting a picture of it.

As previously posted, I'm concerned about rope friction and localized stress/damage, so I was wondering how to minimize this when rigging around a tree.

Feel free to add anything you may find helpful.


Thanks again

Alfred
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Re: Improving rigging for descending?

Postby Chads93GT » Nov 3, 2014 2:48 pm

Tie a figure 8 in the end of the rope, wrap it around the tree3 times,clip it into the rope going into the pit and rappel. You are way overthinking this situation if you think multiple rigging around a tree will eventually ruin the rope. That being said, who is the manufacture of your rope? unless you weigh 400 pounds, a ropes breaking strength that is 15x your body weight really isnt that great.
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Re: Improving rigging for descending?

Postby alfred » Nov 3, 2014 3:05 pm

Hi Chad,

the manufacturer is Kingfisher and I messed up converting between measuring units, thus the min. breaking load is not 15x my bodyweight but closer to 30x.


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Re: Improving rigging for descending?

Postby GroundquestMSA » Nov 3, 2014 4:11 pm

I've not heard of anyone using a thimble in the eye of their rigging, but there's a lot I haven't heard of. Using the so called "tensionless hitch" mentioned by Adam and described by Chad is nice because it puts zero strain on your knot. It also allows you to lower the rope in an emergency by tying on a second rope (if needed) and using the tree as a friction device or in sequence with another friction device.

Ropes are made to be tied and used, and as long as you are using an appropriate knot and padding sharp rocks, I wouldn't worry too much about routine use damaging the rope.

I had some similar questions a while back on this thread: http://www.forums.caves.org/viewtopic.php?f=5&t=13027&hilit=+alternating+ends

And Hi! What part of the world are you caving in?
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Re: Improving rigging for descending?

Postby Chads93GT » Nov 3, 2014 5:07 pm

For the subject of the thimbles, I have seen them used at one place. Bridge day, by Extreme Rappels on their rappelling stations and on the dedicated ropes.I have not seen them used anywhere else in the SRT realm. Ive always thought they were rather pointless.
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Re: Improving rigging for descending?

Postby NZcaver » Nov 3, 2014 5:40 pm

Chads93GT wrote:For the subject of the thimbles, I have seen them used at one place. Bridge day, by Extreme Rappels on their rappelling stations and on the dedicated ropes.I have not seen them used anywhere else in the SRT realm. Ive always thought they were rather pointless.

Permanent eyes are an option you can select when ordering some ropes. They are particularly popular on short lengths of rope used for fall prevention because they are neat, compact, fast to clip/unclip and relatively idiot-resistant. I have a short lanyard with ends that look like this -

Image

Not so common in full length ropes, especially those used for caving and climbing. Knots are cheaper.
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Re: Improving rigging for descending?

Postby GroundquestMSA » Nov 3, 2014 5:49 pm

alfred wrote:the manufacturer is Kingfisher


Is it a braid on braid construction, or a kernmantle rope?
Besides strength and durability, low-stretch is important for SRT. Braid on braid ropes are popular with arborists, but not with cavers. I don't know if they're unsafe, I've never used one.
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Re: Improving rigging for descending?

Postby alfred » Nov 4, 2014 9:33 am

Thank you all for your insights.

I'm caving in Europe and my rope is braid on braid. I don't know why it's not popular but as farbas stretch and strength are concerned, it looks good to use in SRT in my opinion.

I'm quite paranoid but I prefer to tie knots myself rather than getting pre-looped sewn ropes unless it's a reputable manufacturer.

On knots being tied permanently on the rope, I've read in "Life on a line" that they make rope locally weaker since it holds that position for a long time, however that's concerning only if you untie the rope after it was kept knotted for very long.

Hence, permanent knots as figure-8 and double fisherman's as used in safestopping the descent or for Prusik loops shouldn't be affected since they're supposed to stay that way until they're put out of duty.

I asked about rope damage on rigging thru friction around a tree multiple times since some oaks have a very rough bark, so been wondering if padding with a fabric around the bark would help anyhow.

By th way, how are you padding rope against sharp rocks? Is it effective even on wide angle (80-90 degrees) bends?


Thank you very much
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Re: Improving rigging for descending?

Postby Chads93GT » Nov 4, 2014 12:08 pm

We put pads around trees to protect the trees from the rope, not protect the rope from the trees. Nylon ropes will cut limestone in half over time.

We pad lips as well to protect the rope from bedrock.

I never leave knots permanently in rope. I always untie them and coil them up for storage, or put them in a rope bag, however you store your ropes.
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Re: Improving rigging for descending?

Postby NZcaver » Nov 4, 2014 8:11 pm

Chads93GT wrote:We put pads around trees to protect the trees from the rope, not protect the rope from the trees. Nylon ropes will cut limestone in half over time.

We pad lips as well to protect the rope from bedrock.

I never leave knots permanently in rope. I always untie them and coil them up for storage, or put them in a rope bag, however you store your ropes.

Yes to all of this. I always untie after each use, and retie the ends once bagged and ready to go for next time.

Also, bear in mind that we (US cavers) most commonly use 11mm rope which has greater strength and more durability than the 9-10mm ropes which may be more common in European caving. Therefore different rigging methods may need to be used. Wrapping a tree with a tensionless hitch should not cause abrasion problems with thinner rope, but you would be wise to add a few more wraps for extra friction than you would when using thicker rope. It is true that knots can have a more dramatic effect on the breaking strength of a thinner rope versus a thicker one, but with the appropriate knots in modern ropes suitable for caving it should not be a big cause for concern. One advantage of a tied knot over a sewn eye is that it will absorb a shock load better and is actually less likely to fail in this instance. So if you are concerned about a rebelay blowing out or something similar, you might want to stick with knots.
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