"double fisherman" vs. bends to join two lines?

The double fisherman, or blood knot, really is an inferior knot to use for this purpose. By definition a knot ties to itself, think bowline or overhand. A bend is used to join two ropes together. This is where rock climbers are embarrassingly short on knot knowledge....
...I'm posing this to the climbing community in part because I don't know how these have been overlooked or if they have been used, perhaps there is a reason climbers don't prefer bends.

(Rarely followed)Guideline #2: Don't be a doofus

Dylan Dwyer wrote:The double fisherman, or blood knot, really is an inferior knot to use for this purpose.

It is strong and secure. Fairly easy to tie, hard to screw up. Can be difficult to untie, doesn't roll over edges and obstructions. This may not be perfect, but it isn't even remotely close to "inferior."

Dylan Dwyer wrote:This is where rock climbers are embarrassingly short on knot knowledge.

As with most things involving knowledge, there is a spectrum from wise to ignorant, and climbers are no different from other groups in this regard. I might add that one doesn't have to be a sailor like Lee and Jim to know a lot of knots, and it may be worth adding that you should be careful about bursting through doors already long open---there may be plenty of embarrassment to go around.

Dylan Dwyer wrote:Here's the sheet bend

As Jim says, the ends have to be fixed or "seized," otherwise it will get you killed rappelling, since it fairs poorly under cyclic loading and unloading. The typical climbing method is to fasten both ends with a single or double overhand. What this produces is a double sheet bend inside a fisherman's or double fisherman's knot, so a pretty bulky alternative, but one that, along with the ordinary square knot finished in the same way, was used by many climbers (including me) for a while, since both knots had the advantage of being easily untied after loading.

A double sheet bend backed up by double overhands is still a good way to join a very thin reepschnur to a fat climbing rope.

Dylan Dwyer wrote:Or my favorite, the Carrick Bend, essentially two interlocking bowlines. It is strong, won't roll and most importantly, bends will untie easily when needed.

This is a classic example of a little knowledge being a bad thing. The double carrick bend is about as bad a choice for a climbing knot as a good knot can be.

First of all, it was never meant for thin soft ropes, it is a cable and hawser knot. In thin soft ropes it capsizes and swallows a lot of tail in the process, making seized ends highly desirable if not absolutely essential, meaning that, as with the sheet bend, you've already got a fisherman's knot with another knot inside it. Secondly, the double carrick bend is kind of hard to tie, you have to hold one loop together while weaving the other end through, and sooner or later this will prove to be a problem in severe conditions. Thirdly, it is easy to tie incorrect versions that hold together as an unweighted knot but which pull apart under load (the free ends have to emerge from diagonally opposite positions in the knot). The result is a bulky knot that doesn't roll over obstacles. It isn't even entirely clear that it is a high-efficiency knot in thin ropes---not really an issue though because among the various appropriate alternatives, strength differences are irrelevant since all are plenty strong enough. It is relatively easy to untie, but this is the only advantage in a host of decisive drawbacks for climbing.

You didn't mention, (but Jim did) the flemish bend, which is still a worthy competitor for fisherman's knot. Personally, I've found it about as hard to untie after loading as a double fisherman's, but others have found it to be easier.

For most rappelling applications, the EDK or flat overhand is by far the best alternative. It is easy to tie and untie, it doesn't have dangerous variants that could easily be tied by mistake, and it decreases pull-down resistance. An optional single overhand backup decreases capsizing potential, especially with ropes of unequal diameter. (This is not a significant problem for ordinary loads but might be a consideration for rescue loads and perhaps for sodden ropes.) For joining lines meant to be fixed for periods of time and subjected to substantial load variations, the double sheet bend backed up by double fisherman's remains an excellent choice.

Perhaps it should also be noted that there are at least two other "flat" knots that will decrease pull-down resistance. One of them is just a flat single or double fisherman's knot, which means that most climbers already know how to tie it.

To sum up.

1. For ordinary rappelling, the EDK has the most advantages and the fewest disadvantages.

2. The double fisherman's and flemish bend vie for second and third place, with ease of untying and higher pull-down resistance being the issues.

3. The double carrick bend is just plain out. Too many and too serious drawbacks.

4. Most of the other alternatives have to be enclosed in a fisherman's knot, so why not just use a fisherman's knot? Answer: high loads or long-term loading might dictate putting something inside the fisherman's knot that won't weld. The double sheet bend is probably the best interior option for these cases. Increased pull-down resistance will be one consequence one has to live with.

Does anybody else join two ropes together with a figure 8 follow through ? That's what I use for raps.

That's a flemish bend.

Colt2056 wrote:Does anybody else join two ropes together with a figure 8 follow through ? That's what I use for raps.

Yes, I do. I know there are other options but after the approach in, then the climb followed by a rap that requires two ropes, I puss out and use a knot that I can be sure I tied correct.

thank you for all the answers to my question. didn't mean to come off ignorant and dickish but whatever, my question has been thoroughly answered. i like the idea of simplicity and ease of spotting errors by using a few knots on the rock. another idea that i had of why we don't use bends had to do with loading and unloading so i'm glad that was answered

Doug S wrote: Also, I think the proper name for the EDK is an "offset overhand bend".

Maybe, but the best name is EDK!

Bill Czajkowski wrote: Maybe, but the best name is EDK!

Yep.

Dylan, I want to point out one thing if you're experimenting with rappel knots (er... bends). Don't try the offset figure 8. Although it may seem hard to believe, the figure 8 actually "rolls" or capsizes under much smaller loads than the EDK. I'm not referring to the flemish bend. I mean the offset figure 8. Check out this link.

Be safe :)