Safety Margin Issues with Ropes > EDK vs Double Fisherman

Koen,

Although I was hoping people wouldn't bring this up at the same time creating a lot more information for people to digest (I guess the note in my post didn't work), I respect your opinion a great deal from the posts you've made to this group and will reply to your post.

> I find it difficult to swallow that a double fishermans knot should > be a beginners first choice over an EDK... apart from pure strength > there is no benefit whatsoever:

If you read the entire post as well as the paper it is addressing, you might be surprised to find how little the WLL is on the new ropes being used by the new methods. So to me the strength is a very important factor in managing the risk of failure across the range of ropes and methods promoted in canyoneering at the moment.

Have you tried the fishline experiment? The EDK relies on a lot more on friction for its strength than the double fisherman, and the sheaths of the new ropes have a different friction coefficient than the ropes they are replacing.

I would feel a lot more at ease in this regard if someone was actually testing these new ropes to get actual knot strengths and roll-over loads. The test results in the paper are surprising.

> - difficulty in dressing (try finding anything simpler than an EDK !)

True - a definite plus for the EDK

> - difficulty in untieing

True, but at least this takes place at the bottom after everyone is done. It is a bigger issue the smaller the rope diameter, and the larger the rappel weight (person + equipment). If you are a big guy using skinny ropes, there is a way to address it by adding a knot. It also doesn't stop one from continueing through the canyon, though it would make rope management a pain.

> - hangs up more during rope retrieval

This is the most important difference from a safety point of view. There is a difference, but I don't think it's as large as others have stated. The large difference measured in that paper only applied to artificial 90 degree edges. The actual canyon tests showed significantly smaller differences. Also, this problem doesn't involve chance of immediate injury/death.

> - eats up more rope

Could you explain. I'll need more time to test myself, but I would think they are roughly the same, and any difference is probably smaller than the varience in rope lengths as bought.

> - death trap when dressed incorrectly...

This is true of any knot.

> oh yes that happens: I came > across such knots four times already in real life canyon situations. > The first three times I tugged on them out of habit, they came loose > before anything nasty happened.

I'm curious, but was the problem of it just being loose (not tightened enough) or was it incorrectly tied? I think most of the tests have shown that an equally loose EDK is much weaker than a double fisherman to make a fair comparison.

> I should have known because I have won many beers with double > fishermans knots: I tie 3 of them on different rope and people can > look (not pull) at them for a minute to try to figure out which is > the bad one. It's near impossible to tell.

The caveat is they can't pull it. But this is a good point. Do not rely on just a visual when checking other people's double fisherman. This configuration (reversed knots) isn't possible using the method I learned to tie the knot. In addition, part of dressing the knot when tied this way would immediately show that kind of mistake if it was possible. But a good point when checking other's work.

> Much simpler learning an EDK: everybody knows it already (it's the > very first knot anyone can make, at age 6 ), it's just a matter of > pointing out its potential weak points.

These are good points. I'd be fine if someone showed the true strength (or more accurately strength degradation) of these knots with the new ropes.

> It should be well dressed, with a decent "tail" and 4 tugs on each > end to make it snug. That's it, like that it won't fail on a rappel > on any normal mountain/caving/canyon rope. The kind beginners use ? > Koen

Just to make sure, you do mean with a second, backup EDK knot, right?

And by normal, do you include the new Blue Water ropes designed for canyoneering?

Steve Newcomb Tucson, AZ

> It should be well dressed, with a decent "tail" and 4 tugs on each
end to make it snug. That's it, like that it won't fail on a rappel
on any normal mountain/caving/canyon rope. The kind beginners use ?

Just to make sure, you do mean with a second, backup EDK knot, right?
And by normal, do you include the new Blue Water ropes designed for > canyoneering? >

No, no second backup knot - just a correctly tightened one. You can't correctly tighten an EDK by just pulling on all strands together, two in each hand. A tug should be given on each strand separately, big difference. Someone once told me "if you don't trust a knot, use another one" . One could argue that a double EDK actually is one knot though.

I don't view the spectra/dyneema core ropes suited for beginners because they have no margin for fall-related error (not knot-related). I always understood that as long as the sheat was in "classic" material there is no need for special knots ? You won't see me attach a pure dyneema cord with an EDK for instance, way too slippery.

But you touch a real problem... people see "pro, rescue use" and high strength values so automatically think those are the way to go. They're not, they're lightweight, actually very fragile ropes which put a lot of stress on anchors.

Koen

While I was digging up dirt on the clove hitch that I use, I came across an instructional video on the EDK&Double fishermans in case it was of any interest to anyone out there.

http://www.youtube.com/watch?v=m7VU4-ei30s

Me? I use another knot so let the 2 knots go at it



--- In Yahoo Canyons Group, "Steve Newcomb" <sanewcomb@...> wrote:
Koen,
Although I was hoping people wouldn't bring this up at the same time > creating a lot more information for people to digest (I guess the note > in my post didn't work), I respect your opinion a great deal from the > posts you've made to this group and will reply to your post.
> I find it difficult to swallow that a double fishermans knot should
be a beginners first choice over an EDK... apart from pure strength
there is no benefit whatsoever:
If you read the entire post as well as the paper it is addressing, you > might be surprised to find how little the WLL is on the new ropes being > used by the new methods. So to me the strength is a very important > factor in managing the risk of failure across the range of ropes and > methods promoted in canyoneering at the moment.
Have you tried the fishline experiment? The EDK relies on a lot more on > friction for its strength than the double fisherman, and the sheaths of > the new ropes have a different friction coefficient than the ropes they > are replacing.
I would feel a lot more at ease in this regard if someone was actually > testing these new ropes to get actual knot strengths and roll-over > loads. The test results in the paper are surprising.
> - difficulty in dressing (try finding anything simpler than an EDK !)
True - a definite plus for the EDK
> - difficulty in untieing
True, but at least this takes place at the bottom after everyone is > done. It is a bigger issue the smaller the rope diameter, and the > larger the rappel weight (person + equipment). If you are a big guy > using skinny ropes, there is a way to address it by adding a knot. It > also doesn't stop one from continueing through the canyon, though it > would make rope management a pain.
> - hangs up more during rope retrieval
This is the most important difference from a safety point of view. > There is a difference, but I don't think it's as large as others have > stated. The large difference measured in that paper only applied to > artificial 90 degree edges. The actual canyon tests showed > significantly smaller differences. Also, this problem doesn't involve > chance of immediate injury/death.
> - eats up more rope
Could you explain. I'll need more time to test myself, but I would > think they are roughly the same, and any difference is probably smaller > than the varience in rope lengths as bought.
> - death trap when dressed incorrectly...
This is true of any knot.
> oh yes that happens: I came
across such knots four times already in real life canyon situations.
The first three times I tugged on them out of habit, they came loose
before anything nasty happened.
I'm curious, but was the problem of it just being loose (not tightened > enough) or was it incorrectly tied? I think most of the tests have > shown that an equally loose EDK is much weaker than a double fisherman > to make a fair comparison.
> I should have known because I have won many beers with double
fishermans knots: I tie 3 of them on different rope and people can
look (not pull) at them for a minute to try to figure out which is
the bad one. It's near impossible to tell.
The caveat is they can't pull it. But this is a good point. Do not rely > on just a visual when checking other people's double fisherman. This > configuration (reversed knots) isn't possible using the method I > learned to tie the knot. In addition, part of dressing the knot when > tied this way would immediately show that kind of mistake if it was > possible. But a good point when checking other's work.
> Much simpler learning an EDK: everybody knows it already (it's the
very first knot anyone can make, at age 6 ), it's just a matter of
pointing out its potential weak points.
These are good points. I'd be fine if someone showed the true strength > (or more accurately strength degradation) of these knots with the new > ropes.
> It should be well dressed, with a decent "tail" and 4 tugs on each
end to make it snug. That's it, like that it won't fail on a rappel
on any normal mountain/caving/canyon rope. The kind beginners use ?
Koen
Just to make sure, you do mean with a second, backup EDK knot, right?
And by normal, do you include the new Blue Water ropes designed for > canyoneering?
Steve Newcomb > Tucson, AZ >

On Jul 26, 2007, at 6:16 PM, desertres wrote:

> Me? I use another knot

Ohh please, do tell. This ought to be good.

-Bill

Me? I use another knot so let the 2 knots go at it > Desertres, I was looking through some pictures I took of the rigging you left behind in the socal canyon the helicopter rescued you from. Can you enlighten me with the names of the knots you used there. Photos section- "name that knot"

That rigging was originally a single rope setup. Knot block was figure 8 on a bight, rope join was the carrick bend. I say orginally because you saw it after the rescue and time in the canyon so there must have been quite a tangle in the ropes yes?.

I didnt use the carrick after that, so you'll have to guess again as to what knot I use. Smart and witty try though. Im impressed with how you have grown as a person these years.

-- In Yahoo Canyons Group, "Steve" <scabourne@...> wrote:

> Me? I use another knot so let the 2 knots go at it
> Desertres, > I was looking through some pictures I took of the rigging you left > behind in the socal canyon the helicopter rescued you from. Can you > enlighten me with the names of the knots you used there. Photos > section- "name that knot" >

--- In Yahoo Canyons Group, "Listserve.w" <listserve.w@...> wrote:
> On Jul 26, 2007, at 6:16 PM, desertres wrote:
> Me? I use another knot
Ohh please, do tell. This ought to be good.
-Bill >

Ought to be good as in lame or as in good? I only bring this up because it interests me as to how you perceive "inexperienced" people. For me, no matter what the "skill level" of a particular person, I am always rooting for that person to make it through their obstacle. As opposed to this 'good' for them that it didnt work out attitude, because they are 'inexperienced' aka 'dont use what I use'. Isnt it sadness if they dont make it past an obstacle in a healthy way, rather than 'justice'? Or is there a perfect canyoneering technique?

Anyways, the knot I use is long 1452. Its an untested(besides myself) knot to my knowledge but has worked for me and others that have descended on it for those raps. Some negatives, some positives like any other knot. Negative is large & doesnt pull like the EDK, positives are easy to untie and doesnt deform. Difficult to check, likely to confound someone who hasnt seen it. webbing,all kinds of rope, its all been done...anyways, its untested at huge loads so....is the Knut hitch and I use that as well on other situations.