Double Fisherman's Knot

[EV]

Does anyone know - or guide me to - how much of a fall a double fisherman's know will withstand? Just curious is all.

[DPS]

I read somewhere the strength rating of knots expressed as a percentage of the unknotted rope's strength. I believe a double fisherman's knot was something like 75%-80%. Hope that helps.

[hollyclimber]

Here is what I want to know...

Some people, like Lambone just the other day, always seem to know the ratings of everything (ie how many kilonewtons until you get to the center of the tootsie roll pop).

How do I find this stuff out? For example, I had someone tell me all this info about using flat overhand knots and how safe they are etc. If I want to go and look up this data to validate it, where do I go?

Or, if you threw away the paper that came with your #2 camalot, and you wanted to read all the geeky fine print, same question...where to go.

By the way, if anyone thinks that a .5 camalot wouldn't fail under a "normal" 80 foot fall, you should see the shred of a camming device that I got to see at the pub last weekend. Crazy sh*t. Freaked me out big time.

[Bronco]

Good for you holly. I am the same way. Thirsty for geeky climbing tech data. No easy answer for the all consuming resource but, I believe your mind is the best tool on your rack and the only ways to develop your arsenal is experience and reading. Reading is the safer way to learn initally, experience will come.

I cruise the climbing section of used book stores I have come across and buy every techincal climbing manual I find. I don't necesarily read them from cover to cover, but get familiar with the content and refer to it when questions come up. Freedom of the Hills is the best if you are only going to have one. Hope this helps.

[hollyclimber]

But is there like a Bible of these research results? Do I trust a spreadsheet on TradGirl.com? Who conducted the test? Was it scientific?

You know what I am saying here. Maybe it is because I am an accountant, and for that work I have to be 100% sure of what my source is and the degree of authority I can give it, but I want authoritative data.

When a guide spouts off data on the EDK, where are they getting it from? Tradgirl?

[Lambone]

I use the Fishermans if I am top-roping something with two chords, or fixing...

But the overhand is way quicker for rappeling. Plus the whole less likely to get stuck thing... $.02

[EV]

Holly: Petzl.com has great technical info.

Sometimes I'll do an internet search for, say, girth hitch and get some incredible info that way.

[Cpt.Caveman]

Mine always seems to hold when I rappel

[forrest_m]

holly - well, it's the internet, so you have no 100% guarantee. the tradgirl stuff all names its sources, i.e. if you look at the spreadsheets, they have explanations of where they come from, mostly testing performed by the poster him/herself. you implied earlier that you trust the breaking strengths given on the camalot tag, so i guess you consider the black diamond catalog authoritative? most manufacturers have this kind of stuff on their website.

i have read that the uiaa has done a bunch of knot testing, but as far as i know, the raw data were published in academic-type papers. probably in the library.

if you want to have a 100% guarantee of testing accuracy, i guess you should go do the tests yourself. (some of the tradgirl test were done by a guy with a strain gauge a comealong, and a bunch of retired ropes of various diameters.)

[summitseeker]

I use both knots, but typically prefer the EDK. One thing worth mentioning is that it is _not_ a good idea to use the EDK with two different diameter ropes. In this situation, I prefer to use the DF or perhaps even better, the figure-eight-follow-through (tails opposed -- some call it the flemish bend) with a fisherman's stopper knot on each tail. Of course, both of the latter are more prone to hanging up.

[This message has been edited by summitseeker (edited 10-17-2001).]

[This message has been edited by summitseeker (edited 10-17-2001).]

[Dru]

...MUCH more prone to hanging up...

but agreed, when using 2 ropes of wildly different diameters (like 10mm lead rope and 7mm rap line), gotta go with something a bit better than the EDK. I usually go with straight DF in that situation, least bulk.

[forrest_m]

the double fish vs. overhand (aka Euro Death Knot, or EDK) question has been debated at great length on rec.climbing by people who actually have access to testing equipment. the latest "consensus" is summarized in the FAQ at tradgirl.com

http://www.tradgirl.com/rc/faq5.htm#rappel

which includes a link to some spreadsheets of testing, discussions of failure mechanisms, etc.

the argument basically comes down to this: the double fishermans is unquestionably far stronger than the EDK, especially if tied poorly. however, the EDK is by far strong enough for rappelling, and has other advantages (primarily that it is less bulky and the knot rotates upwards when pulling the ropes so your ropes are less likely to get stuck). some people say: i want the strongest knot, period. some people say that reducing the risk of a stuck rope is worth the reduction in strength. you make the call.

tech geeks of the world unite.

[Dru]

Euro Death Knot!!!!

[David_Parker]

Different knots have different "stregnths". Most knots are significantly weaker than the actual rope and thus the weak link in the system. The double fisherman's is probably as close or even stronger than the rope. So depending on the situation, this may be the preferrd knot. It also works well when using different diameter ropes. But its is not easy to untie after being weighted and is slow to tie/untie. It can be overkill in many situations so other knots are prefered. It is not ideal for rapping if the rope getting stuck is possible. Seems like other people seem to agree in above posts.

[mattp]

Sitting here at work, most of us agree that the EDK is plenty strong. Out in the mountains, I find that something like half my climbing partners balk at it when I start to tie the ropes together that way. Clearly, they are clueless babies ;-) but I accomodate their juvenile insecurity every time. So far, I have very rarely had the DF cause a completely stuck rope when the EDK would not have done the same (such as pulling the rope into a crack or bush) but it does happen.

[Terry]

One of my first 'interesting' climbing weekends revolved around the use of the double fisherman vs. the water knot. Two parties headed up to Washington Pass for the weekend. We did the Beckey route on Liberty Bell and got our ropes stuck on the last rappel using a DF knot. Luckily some guys were one pitch up on the N Face of Concord. They lowered a rope down to us, we tied on our rope, they pulled our rope up and managed to free the knot. The whole time this was going on, there was a raging debate going on between two of my partners about how screwed up it was to use the DF and why the hell didn't we use the WK since it was less likely to get jammed. The two guys arguing were classic character types - one ironworker construction superintendent the other a mechanical engineer. Very enjoyable interaction with lots of yelling.

We got our ropes down, people cooled down and we headed back to the car and drove down the road to Burgundy. Burgundy was still thought of as an aid route in those days, the only guide book was Beckey's original guidebook - I wish I had kept that one. Three of us did the route, me and the two knot-tying protagonists. My feet were killing me from EBs that were way too tight and I basically demanded to go first on the last rappel so I could get the damned shoes off. After the debacle the previous day we were using the water knot. I set up a double biner rappel, backed off from the anchor and dropped over the edge, and to my surprise was basically falling - the knot had come untied.

For some reason it was my day. I reached out (it was slow motion) grabbed a rock horn and my feet landed on a small ledge. My partners both peered over the edge very slowly and looked like a couple kids at Christmas time. I flipped the ropes up to them, asked them to please tie them together and resumed my descent in a more controlled manner. Nothing was ever said between the knot-tyer and me. The obvious failing on all our parts was not to examine the knot. Having said that, I use the DF for all rappels nowadays.

With over 20 years of climbing I've had just as many ropes get caught without the knot being an issue as I've had get caught by knots- in cracks that neck down, by protruding crystals, or over sharp edges. Speed is not an issue in my opinion whether its the time it takes to tie or untie the knot. It's not calf-roping and the thirty seconds difference in tying the rope isn't important when you're going to trust your life to the knot.

Holly was the .5 Camalot failure on the 'nipple' pitch of Zodiac? I heard about it from a friend in Tacoma at lunch yesterday.

Terry

 

[Wallstein]

quote:

---

Originally posted by hollyclimber:

But is there like a Bible of these research results? Do I trust a spreadsheet on TradGirl.com? Who conducted the test? Was it scientific?

You know what I am saying here. Maybe it is because I am an accountant, and for that work I have to be 100% sure of what my source is and the degree of authority I can give it, but I want authoritative data.

When a guide spouts off data on the EDK, where are they getting it from? Tradgirl?

---

That spreadsheet on Tradgirl.com came from Tom Moyer. He has worked for BD for years. He also works the Search and Rescue team around the area. He is authoritative. The same numbers that are printed about BD stuff comes from this guy.

 

[Terry]

Forest,

Good story. If it hasn't already been done, "Epics" would be an enjoyable new thread. Sorry about the confusion on my part. My point was broad and well hidden. This discussion is mirroring the one between my two climbing partners way back when. I acknowledge the poorly-tied knot doesn't have much to do with which is best but it certainly cemented in my mind which I prefer. Personally, I can tie the DF in the dark with my eyes closed and can feel to be sure it's correct. Others may be able to do the same with EDK.

We got a single rope stuck on Prussik last year on the first rap. No amount of pulling, flicking, or weighting would budge it. I climbed back up the WRidge and found the rope caught on one crystal just below the anchor. I moved the rope and had my partner test it and it slid fine once it was away from rope grabbing rock.

Terry

[summitseeker]

At risk of being anal:

> One of my first 'interesting' climbing

> weekends revolved around the use of the

> double fisherman vs. the water knot.

Note that a water knot is not the same as an EDK (sorry if you didn't mean that they were). The EDK is an overhand (tails together) and the water knot is an overhand-follow-through with tails opposed. I don't know the strength of a overhand-follow-through when tied in cord/rope -- I certainly use it for tying webbing together, though, as do most/all of us I imagine.

I love talking about knots.

[summitseeker]

Oh, and:

> The double fisherman's is probably as close or even stronger than the rope

Is it *really* possible for a knot to be stronger than the rope? My guess is no.

[David_Parker]

Someone should try this. Take a section of old climbing rope and tie a double fishermans knot so the rope loops around a big tree. Then loop the rope around your trailer hitch and pull until the rope breaks. If the rope breaks elsewhere than at the knot, then I guess the knot is stronger than the rope. Try this with different knots. I'll bet someone has already done this and has beta. But I do think some knots CAN be stronger than the rope.

[summitseeker]

This discussion of knots and rope strengh peaked my interest, so here's an interesting article on rope care (from a rope manufacturer):

http://www.lehighgroup.com/CARE.HTM

It contains the quote "Knots reduce the breaking strength of rope as much as 40%; energy which is normally spread over the entire length of the rope directs itself to the knot."

There are many such articles.

One other thing that's worth mentioning is that failing to properly dress a knot can reduce its strength by as much as 50%!

[Matt]

The University of Calgary has an amazing rock gym and in their gym they have (or used to have) a knot buster. On a visit I witnessed all kinds of rope and webbing get pulled apart and it is truly eye opening. The knot is always the weakest link in a good rope. Usually the rope melts where the knot is tied. The knots shrink down and "eats" the rope. In a climbing system, however, usually a karabiner will blow before the rope will. The only thing wierder looking than a fried figure 8 is an oval that's been stretched out.

It makes sense when you think about it. As a knot tightens it bites down on itself, eventually biting all the way through.

The Euro Death Knot vs. Double Fishermans is a good debate. Without a doubt scariest and most dangerous part of climbing is rappelling. I noticed a lot of the more experienced climbers have posted on this subject. Thank you all.

[This message has been edited by Matt (edited 10-18-2001).]

[crazyjizzy]

David Parker:

As you all know, I am one hill-billy juke mother fucker, and I have broke more old climbing ropes with trucks, cats, and tractors than I can count. They typically break either at one side of the knot, or at the hitch, shacle, or clevis. One time we were tryng to yard an old alder down with four parallel rope tied to D4, and they all broke essentially simulateously, with a report that sounded like a bomb.

[forrest_m]

Terry - while I appreciate the story, I’m not sure what bearing it has on the EDK vs. DF debate. Maybe I’m misunderstanding, but it sounds like your partner(s) tied the knot incorrectly, not that the knot failed. In many alpine situations, speed is safety, and not spending a lot of time retrieving stuck ropes is an element in that safety. Stuck ropes happen! Here’s a story of my own:

Me and Daylward were descending from doing the first ascent of the North Face of Mt. Marcus, in the Waddington Range. We had planned for a one-day push, but got caught out and spend the night shivering on a ledge. We rapped through the morning until we got halfway down the headwall that had been the crux of the route on the climb, and we were rapping the most direct line, so reclimbing it would be a major aidfest. Halfway down the overhanging wall, at a fully hanging belay, the ropes started pulling, but shortly after we lost the second end, they hung up. We started pulling for all we were worth – difficult at the awkward station – but no dice. After trying every trick we knew, we attached prusiks onto the ropes and alternated standing in slings, to pull on it as hard as we could. We had climbed on a pair of 8.5mm ropes, and being concerned with safety above all else on this remote climb, had joined them with a DF knot. The thin rope just stretched and stretched. Finally we gave up in defeat, putting our weight back onto the anchor and wondering if we had pulled enough rope to be able to protect whoever had to prusik the rope. I gave the stubborn cord one more yank, and suddenly, magically, it fell free.

We finally figured out what had happened. Instead of being lodged in a “rope-eater”, the edge of the DF knot must have hung up on an edge, or a couple of edges, so the rope was stuck but not jammed. When we stepped out of our slings that were on the stretched rope, it must have rebounded back and over or around whatever it had been hung up on. We got very, very lucky.

I have had to reclimb pitches/jumar or prussik the rope only three times (I’m not counting the many times I’ve scrambled up a little ways or had to cut the end as irretrievable). Twice it was a flailing end that jammed in a crack or wrapped itself around a block, but once it was that big fat DF knot jammed into a constriction where the EDK would’ve slid right through. A 33% lower chance of stuck ropes sounds like a worthwhile tradeoff to me. God knows, with all the shitty rap anchors out there, the chance of my overhand knot breaking is hardly the most worrisome part of rappelling for me…