Thanks for sharing this testing with us - nice to see new data on this
somewhat (still) controversial topic. I disagree with your statements that
the EDK is difficult to untie after loading, or that the TFK is easy to tie
(compared to the EDK) - this hasn't been my experience. The DT-FK seems
easier to tie than the TFK to me. I will try these other knots out,
though...
Some questions based on your report:
Why are all of the knots (when correctly tied) not "absolutely safe?" Your
report states they are all safe up to a load of around 1500 daN. I haven't
heard of a rappel scenario that will produce that kind of load - have you?
If you haven't heard of one, can you imagine it?
Why is "needs carefully tieing" a disadvantage of the EDK? Don't all of the
knots need careful tying? Were tests done with carelessly tied knots, or
were they all tied carefully? Do you have any data that shows the other
knots don't need to be carefully tied?
hank
"Hank Moon"
- Nate
Give it another try, dude.
--
*********************
L. Michael Boos
CH-8001 Zuerich
*********************
to e-mail remove 4 dots from left to right
"Hank Moon" schrieb
"Michael Boos"
- Nate
> "Hank Moon"
> > Don't all of the
> > knots need careful tying?
> See Hank - that's an important and ignored part of the deal. The answer
is
> no.
> This has been done, as you know. Posted here, archived on tradgirl.
hank
> "zwei Mal Umschlagen habe ich brigens schon erlebt, als sich mein
damaliger
> Seilgenosse mutwillig in die Endknoten krachen lie?".
> (I saw two turns of an EDK, when my former buddy carelessly jumped into
the
> knots at the ends of the ropes)
> No, all knots for climbing should be tied carefully . We did not tested
> carelessly tied knots.
hank
DMT
"Hank Moon"
Funny how some of the others had the same names as in Tom's test, though.
Confusion here is bad, and this guy's page just seems to pile more of it on.
Why? Is there some ingenious knot design contest going on here? What is
the point?
The recent accident in Zion also nicely supports my point about the danger
of the confusion over all these knots. This guy thought he was tying an
EDK, but he wasn't.
There are more examples, but let me better explain my perspective with an
analogy. I design equipment for an extremely high volume production line -
computer disk drives. Factory yield drives everything I do. A 0.1% yield
loss can cost 100's of thousands of dollars. If I was a some sort of
authority in the climbing world, like UIAA, I would look at blessing a knot
much in the same way as I bless my designs. Nobody gives a rip about the
nifty, cost effective and reliable features of my design - all they want is
yield. Now, let's look at knots. UIAA has blessed the EDK. My two
examples and Tom's tests show that the knot can easily be screwed up,
thereby yielding injuries and death in the field. Now - how has the triple
fisherman's, as depicted in Freedom of the Hills, yielded in the field?
- Nate
> > I will try these other knots out,
> > though...
> Sounds fun - because I haven't seen any of those knots ever used for rapping
> except the EDK. The casual reader should observe that his triple
> fisherman's isn't.
What is fun, is that there are a couple of other knots, low profile
like the EDK, that might be worth a look see.
However, based on his data, I still think the EDK is the knot for me.
> See Hank - that's an important and ignored part of the deal. The answer is
> no.
> This has been done, as you know. Posted here, archived on tradgirl.
> A look at the yield of different knots across thousands of climbers in
> thousands of situations with just as many different ropes makes it clear to
> me. EDK and its stepchildren just haven't fared well, IMO. These lab
> experiments are academic.
I think the point is that there are more low profile knots similar to
the EDK to choose from.
I read (and reread and reread) that story in the ANAM. And, the
rangers I talked to who where "on scene" said they doubted that the
story was accurate. Feller stopped mid rappel. Retied for some
reason, then the knot failed. Sounds dubious to me, at the very
least. I rap on EDK's all the time, never a problem.
I think you've got it wrong. I think the feller was tying an in-line
figure eight (cow's tail?). May not have finished knot, or left the
tail too short and it rolled (I talked both with SAR who saw the
configuration and folk doin' the FA on the rope set up).
But, no good examples of actual instances where a properly tied EDK
has failed. Unless you know of another?
I think Tom's results show that the EDK works well as a rappel knot.
Any knot which is "screwed up" can have fatal results in a rappel.
Shoot, how many folk blow it on rappel by not feeding their rap device
correctly?
Beauty of the EDK is that it is a very simple knot to tie and untie,
and to visually check prior to rappel to see if its tied correctly.
How many folk have hung their ropes up on rappel due to a large volume
knot? I've seen it done a few times. Especially a barrel type knot
like the double or triple fisherman's. Hard to tell from documented
ANAM type data how many folk perished due to tryin' to free a stuck
rappel line. I've had more than a few friends who have taken enormous
risk by "bat manning" or soloing up to free a barely stuck rope hung
up on the knot. And others who were lucky they had a spare rope to
rap from, leaving the stuck rope end*** out of reach (cut short,
tied all their slings together with the piece that they were able to
pull down). Scary.
And, Josh's posted results from testing show, no movement in the EDK
below 1500 daN? Works for me. Further support for my use of the EDK.
And, the other knots are interesting alternatives that I think folks
hadn't looked at.
Brian in SLC
"Brian in SLC"
I do not discount the whole "a barrel knot hangs up" argument - but I do
discount that it's a good one. There are plenty of well known ways to make
your rope pull clean. In fact, I don't discount the EDK as a worthy knot -
every test seems to prove it. However, as I mentioned, I'm looking at yield
in the field.
- Nate
Jost: I am astounded that you have presented on your own WWWeb site
results for a knot that is NOT what you have previously shown & argued
for--the "triple fisherman's knot" [sic--this is a name already attached
to a known knot, like the grapevine, but w/1 additional wrap]!!!???
How can you look at these photos and write that you don't tie knots
carelessly--when in fact the tested "TFK" is quite different from what
you elsewhere have shown!? --i.p., from what this very WWW page shows
at the bottom.
NOTE THAT THE LOADED ENDS DON'T BOTH PASS THROUGH THE FIRST-ENCOUNTERED
OVERHAND FORM, BUT INSTEAD ONE SIDE TURNS AROUND THE PAIRED ENDS.
I.e., in the left image, the blue rope makes the first-enc.'d
OH form, and the red rope bypasses this, entering it only
after making a loaded turn. In the right image, it is the
black&white rope that makes the first overhand, and the
multi-hued rope. (I could see this knot pulling apart, in
slick hi-mod rope of (pure) Dyneema/Spectra, Vectrus,
or even polyethylene--maybe.)
Further, NOTE THAT THE EDELRID VERSION HAS EFFECTIVELY NO *FLAT* PROFILE
--the low-profile/flat side to enable smooth flow over a surface, and so
doesn't really qualify as a true "side-oriented" bend! After all, THAT
is the quality that gets us into consideration of such bends as the EDK
in the first place!
This is truly amazing, and sheds some light on how well folks (don't) pay
attention to knots! Egads, ... ! (I'll have to hurry up and meet my vow
to provide to you images of some real side-oriented bends, including a
simply improved EDK and a couple of versions of your "TFK" (the initial
overhand can assume a couple of forms).)
Thanks for the work, but, hey, this is a pretty surprising discrepancy
to arise from those who should be intimately familiar and focused with/on
this knot.
------------
To respond to the question about "Aren't all knots tied carefully?",
no, they aren't, really. So climbers and other life-critical users
have some that are dummy proof in other ways--i.e., that work in different
forms. Just scrutinize the many images of the ubiquitous fig.8 loopknot,
and you'll see what I mean. (E.g., the book _On Rope_, 1st ed., p.33,
which is the cover page for the chapter on Knots, shows a non-symmetrical
form of the knot, and beside it a slipped-out-of-orientation Yosemite Bowline!
Abseil bends are occasionally tied by tired climbers in dim light at the end
of a trying day; it is helpful then that the knots used are in some ways
dummy-proof (possibly with use of a back-up). The EDK & Side-Oriented Fig.8
work poorly if the parallel parts slip out of *parallelism*, and in hasty
tying, esp. of the latter knot, this can easily happen. "Leave ends long"
is a tacit admittance of that, and of the fact that the behavior of the knot
depends on how tightly it is drawn up before loading. (Anglers knots, e.g.,
require specific, pretty severe (e.g. approx. 40-60% strength) tensioning
before use, to get into proper/strongest form).
--dl*
====
> thereby yielding injuries and death in the field. Now - how has the triple
> fisherman's, as depicted in Freedom of the Hills, yielded in the field?
I'll use either the EDK or the DF depending on the
situation.
-Mike
<which rappel knot?>
I recommend skepticism of tests, even peer reviewed ones. Even when the
methodology is faultless and bias is given minimal rein, they necessarily
focus on one question at a time. When setting a rappel there are usually
many things to consider. Granted, the knot must not fail.
Here is how it worked for someone like me, who is willing to contract out
some of his thinking: a climber who is highly intelligent and has tons of
field experience put me on to the EDK and I have used it happily but
carefully ever since.
Andy Cairns