Different rappel knot

I searched the forum but found no reference to this knot as an option for joining rappel ropes:
the Flat Double Fisherman's knot

In 2002 Eldrid tested this against the EDK and three nested overhands, and the FDF knot won for several reasons:
-doesn't capsize
-held 15% greater load than the EDK
-uses less rope
-easy to untie after loading

Here's the link: gudelius.de/spst.htm

It's nearly as compact as the EDK, but it has several confidence-inspiring qualities.
What sayest thou, climbing community?

True.
Typical rappel ropes don't see more than ~800 lbs.
They didn't test any poorly tied knots in the linked study, but in this study a sloppy EDK rolled at 200 lbs (perversely, I sometimes think about that while simul-rapping with my partner on 8.3mm strands)

xmission.com/~tmoyer/testin…

Everyone that uses the EDK has to be fastidious about how they tie it, and the notorious name probably helps reinforce that.
I just like the idea of a knot that removes the possibility of capsizing without increasing the chance of getting snagged on the pull.

The main plus for the EDK is the spring effect, especially when the tails point in the pull direction. Looks like you still have this but with a larger knot.

Any testing to compare the "pullability" of the EDK vs the flat double fisherman's.

A previous thread on the subject.

It's actually not bigger if you are in the habit of backing up the EDK:

EDK w/o backup
EDK w/backup
FDF

This is a 10.3mm rope, and although I wrenched on these knots they would be smaller after rapping. I'm not sure whether the EDK or the FDF would tighten down more.

Solution in search of a problem IMHO. The unbacked EDK is plenty strong and small and easy to tie/untie.

I've always used a figure 8 follow WITH double fishermans backups for rappel or a triple fishermans knot by itself...never had a rope stuck once. I've had someone else tie the EDK, but never myself. After reading all the comments on the previous thread I'm almost convinced though. Guess I'm lucky to not have a knot stuck yet?

Kevin,
You may be right. Long enough tails on a EDK mean that even if it does capsize, it won't end up rolling off the ends. Failure at the rap anchor is pretty much final, though. Confidence is nice.

The funny thing about this is that I often choose to tie in using a double bowline: a knot that is notorious for slipping under load, can't easily be double-checked at a distance, and can easily be tied incorrectly -- not confidence-inspiring qualities...

Greg, Thanks for posting this. I have a link to this doc on the EDK which I really like. The part I like is the pull down testing they do with a scale. The EDK creates a "spring" effect when going over an edge which is the magic behind why it is less prone to get stuck. They show that tails first will provide even more spring. I noticed the Flat Fisherman's is more symmetrical so there is no tails first for that knot. I wonder how it would compare to the EDK in their pull test. I know we are getting to a fine point here but I like this kind of stuff.

If I tie the flat fisherman's knot in the field, do I need the electronic calipers to dress it properly? that would be a no go for me :-)

To see knots rolling under slow pull, look at the very end of this movie clip.

I'm with Kevin.

The EDK is my preferred knot for rappelling.

Rick,
Since the electronic caliper's batteries could possibly go dead, you should instead take along this handy fool-proof analog caliper:

That will look great on my rack! Should double as a nut tool. So when are you going to pull out the scale and test the knot over an edge?

My guitar shop doesn't have the right tools for measuring rope drag...

Interesting info, but isn't this just making a version of the wheel that is more round?

Guilty as charged.
They that know me well are not surprised.

After practice tying the EDK (backed up) and the Flat Double Fishermans a few times, back and forth, I see very little difference in speed and I actually think the Flat Fishermans is easier to inspect. If the Flat Double Fishermans provides an extra margin of safety, and, in my opinion is less prone to being miss tied and would better tolerate an undressed knot, why not use it?

Rick,
-My thoughts exactly.

This is an apples to oranges comparison. If you're using an EDK with a backup, you shouldn't be using an EDK at all. The EDK is fine for the job as long as you pay attention.

Clyde wrote:This is an apples to oranges comparison. If you're using an EDK with a backup, you shouldn't be using an EDK at all. The EDK is fine for the job as long as you pay attention.

For me, after I blow a 1 hour approach and make it 2 hours, get off route a couple times on the climb and set up my rappel after 9 pitches, I need that extra margin of safety and something that may not rely so much on being tied perfectly.

Ohhhhh.... I think I just lost potential climbing partners.

Interesting discussion / analysis.

Clyde - it is my understanding from Leuben and an AMGA guide that the EDK with backup, as shown above by Greg, is the standard - the recommended knot.