/ Cam resling knot question

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Cheese Monkey - on 04 Nov 2012
I'm going to overhaul my old WC Friends this week for something to do. I would buy new ones but I simply can't afford it.

I really like the doubled sling idea on the new Dragons and my main goal is to emulate this. The problem is the hole on the stem will not fit any reasonable sized cord doubled.

What I have thought is threading it with cord and tying it off with a bowline/OH/fig8.Then threading one strand through the loop created by the knot and then joining the two strands as normal.

This makes two short loops, and when one is unclipped it makes one big loop. Genius you say!

Any issues with this? I don't like the extra knot, and I'm not too keen on the unusual loading on it by the rethreaded strand. I will probably use a bowline to save a bit on cord length.
I'm planning on using 5.5mm dyneema cord. Is it going to be substantially weakened by this knot compared to 7mm nylon?
Cheese Monkey - on 04 Nov 2012
In reply to Cheese Monkey: Having just thought about it the knot will be loaded the same way it would be by belaying/anchoring from the rope loop, so no worries there. I've answered all my own questions, other than the knotted dyneema but I'm not massively worried about that
Ian Parsons - on 04 Nov 2012
In reply to Cheese Monkey:

While not fully grasping the layout that you describe - which is probably my fault, not yours - I think you do indeed need to be absolutely certain that the knots are going to work. When these ultra-strong 5.5mm cords first appeared about 25 years ago it was discovered, when using them to make slings, that a triple fisherman's knot should be used instead of the usual double; as far as I'm aware that's still the recommendation. (I can't remember whether they were dyneema back then or something else, although these are probably all brand names for the same thing.) It wasn't that a double fisherman's would break - it simply wouldn't stay knotted; I well recall first watching one untie itself like two snakes parting company at about 5kN! My point is that this demonstrates how a knot that is suitable for normal climbing rope may not be for dyneema. Because the latter isn't used as main climbing rope any test results relating to its performance with end knots - bowline, fig-8, overhand, etc - is less well-known; I've certainly never come across any, but more importantly, have you? Of course the "undoing itself" procedure takes time, and it's entirely possible that in a fall - as opposed to a slow pull on a test-rig - the peak load would have come and gone before the knot had time to pull through, but with a particularly high loading - factor 2, perhaps - and in the absence of specific data, you end up relying to some extent on guesswork.
Steve Clark - on 04 Nov 2012
In reply to Cheese Monkey:

I think there's some info on this on the needlesports site.

You need more cord than you'd think. 1.25m per cam to allow for the knot.

It's also a pain to cut/seal dyneema. You need to cut the core short and seal over with the sheath. They won't melt together like nylon.

Steve
Cheese Monkey - on 04 Nov 2012
In reply to Ian Parsons: Yeah I know about tying it off with a triple. Theres no possible way for the bowline to come undone, I'm just more concerned about overall strength. Like you say it is a bit of guesswork but you can't predict everything I guess. Maybe ill just lob off onto it backed up haha
Cheese Monkey - on 04 Nov 2012
In reply to Steve Clark: I've thought about this and I've got plenty of regular 6mm cord of lower quality to get the length right and i'll get lengths cut to order so I don't need to faff
Dan Lane - on 04 Nov 2012
In reply to Cheese Monkey:
> (In reply to Ian Parsons) ...Theres no possible way for the bowline to come undone...

You couldn't be more wrong...Bowline's slip with regular climbing rope, they're even more likely to slip (and come completely undone) with slick, slippy dyneema!

I'll not be climbing on your cams!

Have you considered sending them back to Wild Country to be re-slinged properly?
Ian Parsons - on 04 Nov 2012
In reply to Cheese Monkey:
> (In reply to Ian Parsons) Yeah I know about tying it off with a triple. Theres no possible way for the bowline to come undone, I'm just more concerned about overall strength.

Ah - I think I've just worked out what you mean. As long as you end up with the two ends joined with a triple fisherman's, then yes - the bowline, fig-8 or whatever is captive so can't come undone; it may slip a bit but unless that has the potential to generate a melting level of heat - which I would think unlikely given the short lengths involved - that shouldn't be a problem. As far as knot strength is concerned you're quite right in comparing it with clipping back into the rope loop when belaying, and while the alpine butterfly, for instance, is specifically used in various situations to prevent the "incorrect" loading of alternative knots, it's quite common - when threading and knotting a single cord one-handedly, for example - to connect the two ends of a sling with an overhand tied in both strands together which gives a similar configuration; the usual worry in this case, as with the joined ends of abseil ropes, isn't that the knot might break but that you've left long enough ends to prevent the knot "unrolling" and coming undone, which can't happen if those ends are securely joined. Clear as mud!

Cheese Monkey - on 04 Nov 2012
In reply to Dan Lane: I'm not asking you to climb on them... The only way I can see for the bowline to come undone is if the triple fishermans comes undone, and if that happens it hardly matters. If you'd read my OP you would see that I cannot afford a professional resling
Kevster - on 04 Nov 2012
In reply to Dan Lane:

Sounds like a plan to me, can't be too expensive?
martinph78 on 04 Nov 2012
In reply to Cheese Monkey: Having watched this video I'll never be knotting a dyneema sling. Not sure if it's relevant to dyneema cord or not?

http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

Personally I'd just tie some 6mm cord with a double fishermans and be done. Extend it with a draw if needed.


Richard88 - on 04 Nov 2012
In reply to Cheese Monkey: Iv just reslung some friends... All you need to do is get some 12lb fishing wire (or something similar thats thin and strong) and what ever sling length you want to use. I used a 30cm as i find any longer and the cams dont rack tidy. Wrap the fishing line round the sling a few times, thread the line throgh the friend and pull the sling through. You'll be suprised at how easy the sling goes through.
Hope that makes sense?
wivanov - on 04 Nov 2012
In reply to Cheese Monkey:
> I'm going to overhaul my old WC Friends this week for something to do. I would buy new ones but I simply can't afford it.
>
> I really like the doubled sling idea on the new Dragons and my main goal is to emulate this. The problem is the hole on the stem will not fit any reasonable sized cord doubled.

Honestly, looking at all the posts about this it sounds like it's not worth all the faff (I like that word). Tie them off with a short piece of cord or webbing and use your alpine draw to extend when necessary. Tried and true.

Are you REALLY gaining so much with the doubled sling?
BenTiffin - on 05 Nov 2012
In reply to Dan Lane: Depends on the age of the cams. I seem to remember that like DMM Mamba's, WC will not resling cams over a certain age no matter what condition they are in.
jkarran - on 05 Nov 2012
In reply to Cheese Monkey:

I can't visualise what you're describing but whatever it is I'd use a much more stable knot than a bowline to form your loops.

I re-slung mine by pushing a loop of 6 or 8mm Mammut stitched sling (I forget which, they are pretty rare) through the original sling holes then I clip both loops. They can potentially be extended by forming a larksfoot at the cam and only clipping one loop. Personally I can't be arsed, I just stick a longer draw on them.

10mm slings would work reasonably well and those are common.
jk
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Dan Lane - on 05 Nov 2012
In reply to Cheese Monkey:

I read the OP to suggest you cannot afford new cams, there was no mention of not being able to get them re-slung.

I'm completely lost as to what you plan to do with the cord now. care to post a picture once you've done one? It might make a bit more sense (to me anyway!)

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