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slacker_jon
Nov 21, 2006, 7:11 PM
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I've posted this question on a slacklining forum before, but didn't get a good reply. What are the strongest knots to use to make a loop at the end of a rope (intended purpose for a final backup of a highline)?
I have seen the double overhand recommended for high-spec accessory cords and have also heard the double water-bowline cited as a stronger than theaverage knot? Thoughts?
Also, could the strength of the connection be increasd by first running the rope through a figure of 8 and then knotting it to add friction and therefore reduce the force on the knot?
Hopefully there will never be any reason to test this as I incorporate redundancy into my highlines before the rope would which 'should' come into play first if a mainline breaks - but having read that the average knot weakens a rope between 40-60% it seems that I could increase my level of redundancy by finding the right knot for the job.
Cheers,
Jon
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microbarn
Nov 21, 2006, 8:04 PM
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I found this knot works well
http://i1.tinypic.com/sg3dpf.jpg
double bowline backed up with a figure 8 backed up with a 13x fishermans backed up with a double bowline backed up with a overhand.
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devils_advocate
Nov 21, 2006, 8:45 PM
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I have never had a 8-13xFM-2d-OH fail on me. Never. Two words: Uber Bomber
BTW: not sure about your 40-60% figure. Most of the testing I've read put's it more around 20-30% for climbing knots.
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slacker_jon
Nov 21, 2006, 9:17 PM
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Where do I begin to tie it and where is the final loop?
Any idea as to the origin of the knot also?
Cheers
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slacker_jon
Nov 21, 2006, 9:54 PM
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In reply to: I have never had a 8-13xFM-2d-OH fail on me. Never. Two words: Uber Bomber
Seems nice and simple - where does the 8-13xFM go - around all the line coming out of the line end of the 2s-OH's? - or around just the one important line?
If you could post a picture it would be much appreciated!
You seem very sure of this knot - where do you normally use it? How important is it to have that many turns in the FM's also.
Thanks - Jon
(This post was edited by slacker_jon on Nov 21, 2006, 9:57 PM)
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seankirsch73
Nov 23, 2006, 5:45 PM
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"Mountaineering:Freedom of the Hills" book has the specs on each knot typically used in rope work.
The rope looses its strength the tighter the rope has to bend in the knot... ie knots like the bowline. The tighter the bend the more the outside of the knot has to carry the load.
The 4:1 rule is a good example to go by. A double figure 8 would be a pretty strong knot.
The best would be a friction knot where the anchor was at least 8X the diameter of the rope, and uses friction to hold it in place instead of the actual knot. A backup knot can still be tied, but is merely to hold it in place and does not actually hold any of the weight.
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microbarn
Nov 26, 2006, 3:42 PM
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your question has been answered before. So, if this isn't enough information then you should do a search.
Mountaineering freedom of the hills is a good starting point. It won't give you the specifics that a search could reveal.
If you are tying the knot in webbing, then use an overhand follow-through. Make sure the webbing is flat the entire way through it.
If you are using static or dynamic climbing rope, use a figure 8 on a bight.
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marktanguay
Nov 27, 2006, 2:29 PM
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yeah simple is always better. the more complicated you make it, the more apt, you are to screw things up.
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watchman
Nov 28, 2006, 3:32 PM
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Unsure if you already are doing this, but you should be using tandem prussiks for your highline, with just about any properly tied off knot after that. If you blow through a set of prussiks, things have gone so terribly wrong that your final tie off knot probably wont matter too much.
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slacker_jon
Nov 28, 2006, 6:00 PM
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Could you explain a bit more. Would you use a prussik or a kleimheist? What thickness of cord would you use and how many turns etc? I've seen prussiks used on some of the Dan Osman video's fastened part way down the jump line...
For the record, on one of the Patagonia adverts Dean Potter has his back up rope tied up with a Fig8 (not sure if it's in-line?).
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mountainmack
Nov 28, 2006, 6:57 PM
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Hey slacker - as you probably know any time you put a knot in a rope (or webbing) you reduce its strength. Following that logic the strongest knot to place is the "no knot-knot". Seriously, it is an excellent knot if you have a worthy tree or other such anchor to rely on.
To tie a "no knot-knot" you just wrap your line around the tree several imes (at least four) until the force on the working part of the rope cannot pull the rope away due to the friction of the wraps. Of course you should tie the free end of the rope off to the working end as a back up but it can be slack looped (drooped) to the tie off as it is only a backup and not part of the knot.
Keep the wraps as low as possible on the tree to reduce leverage on the root structure and be sure the tree is "bomber" to begin with.
Good luck and play safe.
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stymingersfink
Dec 9, 2006, 3:56 AM
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in another topic I posted a link to an international knot guild, I don't remember what topic it was but it was only in the last week.
When surfing their boards i found an interesting topic of bowstring knots, with the postulate that with the forces that bowstrings undergo it is suprising that such a simple knot can be so strong. You'll have to check it out for yourself...
IGKT
bowstring knot
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