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 Post subject: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:06 pm 
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Apparent there isn't such a topic...

a) in joining 2 ropes of same diameter:
ie, when rapping on half ropes.
- Which knot do you use,
- Why do you use said knot?

b) in joining ropes of different diameter:
ie, 10,2mm sport rope with a 8,5mm half rope. probably to abseil.
- Which knot do you use, and why?

I use a reef knot and 2 x fisherman on either side.
This seem to work fine for any combination of diameters.

Yet I feel there must be a better system.


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:07 pm 
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Like such....


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:13 pm 
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I'm sure we've had a long discussion (probably more than one) about this, but here goes:

Overhand knot for same diameter. Needless to say it must be neat, like all other knots. To prevent any paranoia that it will flip over itself like the EDK (the overhand is not the EDK, using a figure 8 is), I simply tie another one behind the first one making it impossible to flip. It is easy to untie, small and is less prone to get stuck.

I'd use a double fisherman for different diameters.

Doesn't a reef knot simply fall apart with different diameter ropes? I know you make a fisherman either side, but it sounds like the making of a bfk :mrgreen:


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:29 pm 
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shorti wrote:
it sounds like the making of a bfk :mrgreen:


Exactly my point.
Having made it for so many years, it is hard, but time, to change.




shorti wrote:
I'm sure we've had a long discussion

I'm sure too, but couldn't find it.


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:49 pm 
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Location: Stellenbosch
Real Name: Nic Le Maitre
Hi

A great knot to join ropes (of the same diameter) is a variation on the EDK. Tie it as usual (overhand using the tails of both knots) and pass the tails of the knot through the loop again. When it is pulled tight it has a flat side like an EDK but crucially will not roll out as an EDK can. I'd still advise tying it with long tails.

The best knot to join ropes of differing diameter is the sheetbend: http://www.cibolasar.org/minilessons/knots/knots2.shtml (scroll down a bit)

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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 4:52 pm 
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Real Name: Lee de Smidt
There are hundreds of ways to bend ropes.

If there is going to be a constant tension on the rope (abseiling) a sheet bend works best for 2 different diameter ropes. Make sure to tie your fishermans either side of the knot though. Under a jarring load the knot will work itself loose, hence my precursor.

I once tied a sheet bend to the anchor line for a hard bottomed rubberduck before going for a surf. With the jarring of the swell the knot worked itself loose and I had to rescue the boat off the rocks half a mile away and then recover the anchor.

I've always just used a re-threaded figure eight but threaded from the other direction like a tape knot with a double fishermans for safety. Sure there is a name for it...


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 5:27 pm 
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Real Name: Lee de Smidt
Flemish bend

http://www.animatedknots.com/fig8join/index.php


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 6:10 pm 
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Found a nice article: http://www.needlesports.com/advice/abseilknots.htm

Their conclusion:
"As a result of all these findings we are convinced that what we term the Double Overhand is the best knot (if not the safest) to use when joining two ropes together for abseiling"


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 Post subject: Re: Joining 2 ropes
PostPosted: Mon Apr 16, 2012 7:05 pm 
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What Nic said.

It's affectionately called the double death knot.
It has all the good properties of the Euro Death Knot (simple, and lies flat so can be pulled over edges) but none of the bad (it can't 'capsize')

Of course a knot like this is technically not a 'full-strength' knot for dynamic anchor and rescue scenarios, but is perfect for abseiling.


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 Post subject: Re: Joining 2 ropes
PostPosted: Tue Apr 17, 2012 6:52 am 
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Location: Stellenbosch
Real Name: Johann Lanz
I have always been fairly casual about the knot I use (probably not a good thing) and have used various ones. Probably time to be more deliberate about it. But my casualness is based on an assumption (often dangerous, I know) that the tension on the ropes is actually very minimal when abseiling. Think about it. Its only your weight. Can you really picture your own weight pulling a knot (any knot) out? So can an EDK (one-sided overhand bend has a better ring about it) actually capsize at anything like the kind of tension likely in abseiling? I would think not. Does anyone know at what tension a capsize can occur? Then I have also read that once capsized, the knot is actually stronger. So as long as your tails are long enough, this is not a problem. Is this true? What do we mean by long? I would imagine a foot is adequate. A capsize will actually only use a few centimeters of tail, will it not?

So my take on it is that an EDK with foot long tails is entirely safe (although I would probably still feel better and so pander to the below by making them a little longer). Anything else (including fisherman backups) is mere window dressing to make the abseiler feel better, but is at best superfluous and at worst actually mis-information. But I don't know if this applies to Nick and Ant's suggested variation to the EDK. In this context it is interesting that a figure of 8 tied in the same way as an EDK (which on the surface appears safer because of its size), is actually a less secure knot. Often simpler is better.

Thinking about this has made me consider under what conditions an abseil would exert high tension - if this would ever occur? The only one I can think of is that if you let go somehow and slid down the length of the rope to be arrested by the knots tied in the end - and even then, the stretch in the rope would be huge and the tension on the knot probably not that high. Are there any other situations?

In the interests of being more deliberate about this, I would appreciate other's thoughts on this, especially the idea that anything additional to an EDK is superfluous.

The one great little safety trick for abseiling, for anyone who may not use it, is the short prussik sling below the abseil device, clipped to a harness leg loop. I consider this essential, simply for its usefulness. It allows you to have hands free at any point.


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 Post subject: Re: Joining 2 ropes
PostPosted: Tue Apr 17, 2012 9:36 am 
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Real Name: Nic Le Maitre
Hi

The thing that makes the EDK and other knots capsize and roll out is cyclical loading rather than peak loading. This is where the load comes on and goes off repeatedly, like for instance when you are doing an abseil where the cliff is not completely vertical or overhanging but rather has several ledges. As you reach each ledge your weight comes (mostly) off the rope and then comes back on again producing cyclical loading and rolling out of the knots.

It is therefore better to use knots that do not have the tendency to roll out even of they take 5 seconds longer to tie. Personally I'd only use a knot I know to be 100% safe rather than one I have reservations about but it is up to you.

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 Post subject: Re: Joining 2 ropes
PostPosted: Tue Apr 17, 2012 10:51 am 
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Real Name: Johann Lanz
Seemingly some good information on capsize of EDK: http://user.xmission.com/~tmoyer/testing/EDK.html

Pertinent points: that it takes a large weight to roll the knot the first time (at least 450 kg), as long as it is tied and tightened well. If its tied sloppily it rolls at a much lower weight (90 kg), for the first roll. But then subsequent rolls require increased weight to roll it - that is it gets tighter after each roll, and in all of the tests run (except 1) it reached breaking of the rope weight before the knot rolled right through. The 1 that rolled through was different diameter ropes 11mm and 8mm and was soaked in a bucket before the test - and it still took 630kg to roll it through.

Based on the above, I can't help thinking that you're pretty safe abseiling on this. Probably much safer than doing a lot of other things.


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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Apr 20, 2012 12:09 pm 
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I use an overhand with another one right behind it, with about 30cm of tail. Quick to tie, simple I.e. hard to get wrong when you're tired as you often are when doing repeated raps. As Shorti points out, it's less likely to get stuck because of the asymmetry of the knot when running over an edge. And AFAIK, the 2nd overhand prevents any possibilty of it rolling over


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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Apr 20, 2012 2:10 pm 
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I use a Double Fisherman's

The knot is small and can easily be pulled over edges without snagging

:afro:

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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Apr 20, 2012 2:47 pm 
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It looks like different diameters should also be fine with the overhand knot. Am I right? I'll try it tonight and see if there's anything obviously wrong with it.

Mario, I think you've just been lucky you haven't got your ropes stuck :mrgreen:


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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Apr 20, 2012 2:59 pm 
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Real Name: Nic Le Maitre
I'd be very wary of using just an overhand to join them. Knots with ropes of differing diameters tend to behave very differently. Either the double EDK or the two tied one behind one another would do, otherwise just practice the sheetbend

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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Apr 20, 2012 4:17 pm 
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Hey shorti,

Clearly I'm not climbing enough! :cyclops:

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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Aug 24, 2012 1:24 pm 
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... picking up on an old thread here.

Nic or Ant, any chance you could post a pic of a double death knot? Thanks.


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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Aug 24, 2012 3:51 pm 
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Location: Stellenbosch
Real Name: Nic Le Maitre
First tie an overhand with both ropes
Attachment:
P8240003.JPG
P8240003.JPG [ 119.3 KiB | Viewed 2542 times ]


Take the tails of the ropes through the loop again
Attachment:
P8240005.JPG
P8240005.JPG [ 121.4 KiB | Viewed 2542 times ]


Tighten the knot
Attachment:
P8240007.JPG
P8240007.JPG [ 115.08 KiB | Viewed 2542 times ]

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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Jan 30, 2015 1:09 pm 
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Real Name: Nic Le Maitre
http://www.gudelius.de/spst.htm

Some non conventional rope joining knots. I particularly like the last one. All the advantages of the double fisherman, with a flat side, and easy to undo.

Image

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 Post subject: Re: Joining 2 ropes
PostPosted: Fri Jan 30, 2015 3:06 pm 
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Real Name: Stephen Martindale
Das Knoten ist aber schön!

For those who don't want to sift through the article, here's a summary of the details on Nic's knot:
  • The article examines three knots and appears to be a report written by a researcher working for or in connection with Edelrid, in Germany.
  • The pictured knot is called a „Doppelter T-Spierenstich” or a "Double T-Fisherman's Knot" presumably because it is a double-fisherman's tied in a 'T'-shape
  • The tests report that it held under a load between 2100 to 2800 daN (21 to 28 kilo Newtons) which is more than your body will withstand and, according to them, 15% higher than a tested EDK.
  • The knot kept its form under a realistic load (6-7 kilo Newtons) and could still be untied afterwards
  • They tested with Edelrid ropes of the same diameter (10.5 mm) and different diameters (10.5 mm / 8 mm) which is fairly representative of the ropes we use on the hill.
  • They left 45 cm tails on all knots. This knot 'used' up to 6cm of that, under load. (The EDK used up to 15 cm due to rolling)
  • They did not test periodic or intermittent loads. (I would assume they didn't shock load it either.)
  • Their only criticism is that the knot is hard to tie.


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 Post subject: Re: Joining 2 ropes
PostPosted: Sat Jan 31, 2015 10:49 am 
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Nic Le Maitre wrote:
http://www.gudelius.de/spst.htm

Some non conventional rope joining knots. I particularly like the last one. All the advantages of the double fisherman, with a flat side, and easy to undo.

Image


Hello Nic

Have you tried to tie this knot?
do you find it easy to tie?

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 Post subject: Re: Joining 2 ropes
PostPosted: Sun Feb 01, 2015 7:08 pm 
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Real Name: Nic Le Maitre
It's not hard, just makes your brain work a bit because one half is the "wrong way around"

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 Post subject: Re: Joining 2 ropes
PostPosted: Sun Feb 01, 2015 8:26 pm 
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Real Name: Duncan
Thanks Nic

I landed up trying it and it is easy and nothing complicated. i'm not sure it will be that easy to untie though.

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Don't cut that which you can untie. Traddies are hard core, they can hang on their nuts.


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