rescue knots

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Postby chh » Nov 10, 2006 2:46 pm

RescueMan wrote:What these tests indicate to me is not so much to avoid girth hitches (though the symmetrical hitches, as I suggested earlier, are superior), but to avoid anything but nylon (or polyesther) in ropes, cordage, and slings.


While I would agree with you for rescue purposes (the origin or this thread) I use my 10mm spectra slings quite often and like them quite a bit. However, I never girth them, and on the very few occassions where I'd had a need to join them I used either 2 carabiners opposite and opposed, or a symmetrical hitch. I've been tempted to use the tech cord for anchor building, but in the end remained with my nylon cordage even though it is bulkier and heavier. I don't think that the spectra/dyneema/dynex/whathaveyou is inherently bad, though I DO think proper usage is key. The stuff certainly isn't "idiot proof". I've used some of the even skinnier slings, mammuts and edelweiss's super skinny ones and they are slick, but I've only used them for specific purposes. I hung from them once at an anchor and untied the rope and I'll tell you, rated to 22kn or not, having your A$$ hanging a couple hundred feet off the deck on what looks like shoestrings made me pucker a little even though there wasn't any chance of them rubbing across a sharp surface or being shock loaded or anything.

Also I think what we are also finding out is that the spectra/dyneema stuff might degrade a little faster than nylon. And for people who are used to dealing with fairly burly (relatively speaking) 9/16, 11/16, and 1 inch webbing, the life span of a 6,8, or 10 mil sling is going to be less. You just can't treat the two materials the same. But this isn't exactly rocket science. Skinnier stuff generally needs to be replaced more quickly no matter what kind of material your dealing with, be it slings or ropes.

This conversation might be a little silly here as I only really use my spectra slings when climbing. Due the nature and quantity of gear I take on a traditional climb, the 10mm slings are what I feel comfortable using given their weight and bulk savings. When vertical caving, however, I'm generally only dealing wtih 11/16" or 1" webbing as I don't have to carry so much. I have used spectra slings for rigging applications before and redirects and felt comforatable with the use there as well though they are few and far between. For the most part, it's nylon.

But you know, when in doubt, nothing comforts quite like nice fat nylon :-)
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Joining rescue ropes

Postby kip » Nov 30, 2006 11:08 pm

Hey this is an old topic but seen as my name is on it I should clarify a few points.

Single sheet bends with tails tied into a loop (see pic) are the bomb when joining 2 ropes for SRT use. Very compact and secure and undo like you wouldn't believe.

Double sheet bends are superb for many rigging applications when quick and easy are the call. They are very handy when used with throw bags as it easy to form the knot with the bag still tied on the end of the rope.

Figure eight bends are the best I still find for for joining 2 rescue ropes as you get a nice streamlined little number that you can (in essence) forget about, but a double sheet bend with a rethread would probably work fine as well (not tried though).

Strength? who cares; show me some authoritive reliable and consistant data that proves one particular knot tied correctly and used appropiately is dangerous over another one of similar fit. If the safety of your system is safe or not safe by the 10% shown in a test on a piece of rope that you are not holding then you have probably lost the plot. What matters is suitability, security and solution. Is it suitable for the task (figure eights been side loaded for example are not), is it secure enough for the application (bowlines in water for example with out a tie off) does it provide an appropiate solution (alpine butrterflys on traverse lines are a good solution for side loading needs).

We have recently done some testing on the sheet bends and other knots and it confirmed our very worst fears, if you subject a piece of rope to loads it was not designed for it breaks.':rofl:'


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Re: Joining rescue ropes

Postby RescueMan » Dec 1, 2006 11:51 am

kip wrote:Strength? who cares...What matters is suitability, security and solution.


Well said, but you've got the three S's a bit wrong. By your definitions, suitability (is it appropriate for the application) and solution (does it offer a suitable solution to the problem) are one and the same.

The three S's are:
Suitability - appropriate for its application (which includes ease of untying)
Security - will it stay tied in the application (does it require backup)
Stability - will it retain its form (not collapse) in the application

- Robert
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Re: Joining rescue ropes

Postby kip » Dec 1, 2006 4:32 pm

RescueMan wrote:
kip wrote:Strength? who cares...What matters is suitability, security and solution.


The solution is really a thinking process it might be suitable and secure but does it provide a solution to the problem (the kind of enigmatic thinking, deeper head scratching, can it be solved differently etc) hence no use of use of stability (which i feel is covered under security as a collapsed knot is quite possibly not secure).


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Re: Joining rescue ropes

Postby RescueMan » Dec 1, 2006 4:53 pm

kip wrote:hence no use of use of stability (which i feel is covered under security as a collapsed knot is quite possibly not secure).


Ah, but stability and security are entirely different qualities and both must be understood in order to determine suitability.

As an example: there are no more secure knots (doesn't untie itself) than the overhand, the figure-8, or any of their variants. Yet the "offset overhand bend", now commonly used to join rappel ropes for a pull-down in rough terrain, has been shown to "roll" under load (the offset figure-8 bend even more).

In this application, those otherwise extremely secure knots become unstable (sometimes fatally so).

You might say that "suitability" encompasses all the other qualities, since a knot that's dangerously insecure or unstable in a particular application is certainly not "suitable".

But, in order to make a determination about suitability, one must understand BOTH the concepts of security (will it stay tied, even in unloading cycles or washed by a moving current) and stability (will it retain its form even when dragged against a rock face or under unsual loading).

And, if a knot is "suitable" for a given application, then it can be considered a "solution" to the problem at hand. Those concepts are synonymous.

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