What is the safest rappel?

So, I just read this article on rock and ice...http://www.rockandice.com/climbing-news/climb-safe-what-is-the-safest-rappel-knot

In it, Kolin Powick, explains that a double fisherman's is stronger then an EDK but that obviously a fisherman's has a higher chance of getting stuck on something. He also says he still uses EDK with a long enough tail. Whenever I do a multi-pitch route I tend to use the EDK as well because it is fast, strong, and easy to untie. Should, after leaving a long tail, I tie a backup over hand on the tail? Is it worth having a backup on something like that or does it make more room for error as far as the rope getting stuck when pulling?

Thanks

The key message in this article is that there's no reason to worry about the EDK. IMO that includes needing any sort of second knot behind it - you don't.

I have to wonder why we're seeing this year old (3/20/15) article from R&I getting posted again. Could it be they are trying to undo the damage done by the much more recent (3 weeks ago) piece of bullsh:t that mistakenly called the flat-8 knot an EDK, and otherwise confused the two knots while altogether ignoring the large body of evidence damning the flat 8? In case anyone missed it, here's that more recent piece of shoddy writing:
rockandice.com/climbing-acc…

I've always doubled my EDK's, dressed them evenly, pulled them tight and left a foot or more of tail.

I use the edk, no issues with it.

Gunkie,

I think you are on point with the reason for the article.

I also agree about your EDK answer.

To answer the question in the subject line, the walk-off.

Alicia Sokolowski wrote:To answer the question in the subject line, the walk-off.

Right on.

If that option isn't available, rap as they describe in the various books. About the rope getting hooked on something, I doubt the knot matters, but the rope-tossing method and rope-pulling method might matter. Perhaps someone could study these factors instead of seeing which knot is strongest.

Jon Nelson wrote: .... About the rope getting hooked on something, I doubt the knot matters, but the rope-tossing method and rope-pulling method might matter. ....

JON... I think that the Knot Matters.... EKD will go over an edge, Fishermans will knot....the other stuff matters also.

http://www.mountainproject.com/v/rock-and-ice-claims-edk-failure-and-that-edks-need-to-be-reinvestigated-/111719456__4#a_111776441

a walk off

Well dressed and tightened strand pair ~by strand pair. Then, no backup is needed.

But I see more and more of my partners also tying a backup which is ok.

The Blueprint Part Dank wrote:a walk off

Depends on the walk-off. I've done some walk-offs with sketchy, exposed, or dirty/slippery terrain.

There's a cliff, Bon Echo, near here (Ottawa, ON) where rappels are disallowed (except at a couple specific locations) due to the access agreement with the provincial park the cliff is in. This means most of the descents are by some of the various gullies. These are mostly damp, dirty 4th-class descents. I don't know of anyone who has been hurt rappelling there, but I do know of at least one gully descent slip resulting in injury (broken either collar bone or shoulder, or maybe both).

Guy Keesee wrote: JON... I think that the Knot Matters.... EKD will go over an edge, Fishermans will knot....the other stuff matters also.

Yes, it is possible, and I hear people saying it all the time. But based on what evidence? I've never had a fisherman's get stuck, so I just think it is a minor thing, whichever way it goes.

I agree that the EDK is easier to tie and untie, but the OP's question was about safety.

I used to poo-poo the back-up prussik on brake hand.... but now I like it.

Russ Keane wrote:I used to poo-poo the back-up prussik on brake hand.... but now I like it.

I was ice climbing, and had to do a very short rappel and was about to skip the prussik, but threw it on. A chunk of ice hit me, I got stunned, and ended up catching on the prussik. Since then, I've always backed up my rappel device with a prussik no matter how short the rappel.

Hey Jon,

I am a religious user of the EDK, and recently have started using a backup (habit picked up from work, I know it's completely unecessary) but I have seen the fishermans get caught in a place where the fishermans wouldn't have. It's why I changed over to the EDK.....

I'm a desert sandstone climber and I think that the patina flakes in a place like Red Rocks or Zion make a big difference. Nothing worse than being stuck way up on a wall with a stuck knot preventing you from getting to the ground.

Just my opinion and observations, not looking to start any kind of argument....

Sam Keller wrote:Hey Jon, I am a religious user of the EDK, and recently have started using a backup (habit picked up from work, I know it's completely unecessary) but I have seen the fishermans get caught in a place where the fishermans wouldn't have. It's why I changed over to the EDK..... I'm a desert sandstone climber and I think that the patina flakes in a place like Red Rocks or Zion make a big difference. Nothing worse than being stuck way up on a wall with a stuck knot preventing you from getting to the ground. Just my opinion and observations, not looking to start any kind of argument....

That's nice to know, thanks. And you're right, a stuck knot is terrible.

It seems I was just being a bit too skeptical of the jam-avoidance claims. It would be nice though to have some rigorous tests done.

Jon Nelson wrote: Yes, it is possible, and I hear people saying it all the time. But based on what evidence? I've never had a fisherman's get stuck, so I just think it is a minor thing, whichever way it goes. I agree that the EDK is easier to tie and untie, but the OP's question was about safety.

Oh, there is evidence all right. For instance, have a look at

citeseerx.ist.psu.edu/viewd…;jsessionid=30D5C36D2971CB837FD5B522D701FB1F?doi=10.1.1.630.3563&rep=rep1&type=pdf

starting on Page 22. Note that it isn't simply a matter of the knot hanging up; the double fisherman's knot can be a lot harder to pull down too even if the knot isn't actually hanging somewhere. Also note that the testers plain threw out what I'd call the Flemish Bend and they all the "rethreaded figure-8" due to poor performance.

rgold wrote: Oh, there is evidence all right. For instance, have a look at citeseerx.ist.psu.edu/viewd…;jsessionid=30D5C36D2971CB837FD5B522D701FB1F?doi=10.1.1.630.3563&rep=rep1&type=pdf starting on Page 22. Note that it isn't simply a matter of the knot hanging up; the double fisherman's knot can be a lot harder to pull down too even if the knot isn't actually hanging somewhere. Also note that the testers plain threw out what I'd call the Flemish Bend and they all the "rethreaded figure-8" due to poor performance.

The link is to a report of the Bushwalkers Wilderness Rescue Squad of Sydney. Thanks rgold for finding it and posting.

It is a long report, largely about knot strength. In one part, they looked into different knots going over an edge.

Page 22 that you mention shows the set-up for a "hard edge", which is a rope going over a 90 degree edge, pretty much following the perimeter, a situation we generally can and do avoid while rapping. They find that the EDK does better in this case.

Do you have the link to the results on "Sheet E"?
(Which would be the ones of interest, as they concern an actual rock edge.)

I think many people worry more about knots jamming into cracks. And I'm curious if anyone has done a reliable study on that. This study didn't address it.

Double fishermans can and does get caught. It's happened to me a couple of times, the more memorable being a the top rap of the biggest route I'd ever climbed at the time (1976), Wallface. I was wigged out by the enormity of the whole outing, and having to ascend the stuck rap rope (my partner holding fast on the other end) for 150 feet of terrifying exposure... shiver...waiting for it to bust free and drop me at any moment. Scared me so bad I didn't climb again for two months.