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.

Like such....

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

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





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

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)

_________________
Happy climbing
Nic

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...

Flemish bend

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

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"

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.

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.

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.

_________________
Happy climbing
Nic

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.

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

I use a Double Fisherman's

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

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Super Mario

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

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

_________________
Happy climbing
Nic

Hey shorti,

Clearly I'm not climbing enough!

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Super Mario

... picking up on an old thread here.

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

First tie an overhand with both ropes


Take the tails of the ropes through the loop again


Tighten the knot

_________________
Happy climbing
Nic