Strait Bend Testing?

[rickc]

I am interested in any testing results anyone knows of for the Strait Bend (pg 72 of the Apprentice). My specific use for this knot would be to join two 8mm to 11 mm nylon climbing ropes. The joined ropes would be used for rappelling. Typical forces are less than 1000 lbs force but with considerable possible jerking as the line is loaded and unloaded. I am unhappy wih the knot currently beiing recommended by many in the climbing community and am looking for a knot with a good lead, is relatively easy to untie after loading, is reasonably strong, and is secure under load cycling.
Thanks for your help in advance.
Rick C

[allene]

Originally Posted by rickc

I am interested in any testing results anyone knows of for the Strait Bend (pg 72 of the Apprentice). My specific use for this knot would be to join two 8mm to 11 mm nylon climbing ropes. The joined ropes would be used for rappelling. Typical forces are less than 1000 lbs force but with considerable possible jerking as the line is loaded and unloaded. I am unhappy wih the knot currently beiing recommended by many in the climbing community and am looking for a knot with a good lead, is relatively easy to untie after loading, is reasonably strong, and is secure under load cycling.
Thanks for your help in advance.
Rick C

I just found some references on the topic and put them on my site. The strait bend is the same as an alpine butterfly pulled straight. (It is the alpine butterfly with the loop cut). Link This article is probably of interest as it deals with climbing knots in general. It says that the knot retains 61 to 72% of its strength on page 15.

I found other articles and they are indexed here http://L-36.com/rope_articles.php

Allen

[benz]

Hi,

Before I retired from climbing, the strait bend was what I used exclusively for rappelling. The overhand everyone else was using tends to roll, and people would end up leaving ridiculously long tails, or tying another overhand in the tails, to feel safe. I thought it better safety to have a decent bend properly tied.
I put it in one or Rock and Ice's tech tips in '05 or '06, I forget presicely when.
The Zeppelin bend is also very good, and will cause your climbing buddies some eye-popping concern.
Tie carefully,
Ben

[Brion Toss]

Hi,
Grand question. As noted above, the Strait Bend is stronger than some bends (it retains about 60% of the strength of conventional synthetics), and is more secure than some other knots that climbers use. It also, as you noted, has a superior lead, so the ends are less liable to snag on things. It shares these traits with some other bends, notably the Ashley Bend and the Zeppelin Bend. Given an adequate safety factor, security and lead are the most important qualities, so this family features my favorite bends.
Unfortunately, non of the formal tests I've conducted have been with dissimilar rope diameters or materials. Informally, my experience is that these bends seem to be every bit as secure as a Double Sheet Bend, but I wouldn't want to rappel on different diameters without further testing.
By the way, it's not exactly true that the Strait Bend is an Alpine Bend with the loop cut. I think it's more accurate to say that the two knots are structurally analogous, in the same way that the Bowline and Sheet Bend are. The knots are tied in different ways, for different purposes, and usually loaded quite differently.
Fair leads,
Brion Toss

[allene]

Originally Posted by Brion Toss

By the way, it's not exactly true that the Strait Bend is an Alpine Bend with the loop cut. I think it's more accurate to say that the two knots are structurally analogous, in the same way that the Bowline and Sheet Bend are. The knots are tied in different ways, for different purposes, and usually loaded quite differently.
Fair leads,
Brion Toss

There are obviously two ways to load an Alpine Bend. Pulling on the two rope ends and pulling on one rope end and the loop. When I linked the article, I thought that the test was done by pulling on the two ends of the rope but I see now that it was the other way around. My mistake.

Here is another article that tests what they call "Alpine Butterfly Knot (to tie ropes together)". Link The interesting thing in this test is that mostly the knot didn't break. The line broke at the attachment to the test fixture. This is a pretty good example of the frustration of trying to find good data on the strength of knots. But as they said, the knot is very strong.

You might also be interested in knot #28 in this 1975 publication. Link

Allen

[teknocholer]

First of all, while I have done some rappelling, it has always been with a doubled rope or a single top-anchored rope, not with joined ropes, so my comments are not based on experience.

The article that Allene links to places a lot of emphasis on ease of retrieval. and less on the absolute strength of the knots being investigated. This makes sense, since most ropes used by climbers and cavers have very large factors of safety, and a snagged rope could be a serious problem. However, the knot Drohan finally recommends doesn't have much going for it but decent lead. (I note that the Wikipedia article on the Overhand Bend says that American climbers have referred to this as the European Death Knot.)

Since lead is considered so important, I wonder if the Tucked Sheet Bend, aka Binder Twine Knot, is worth investigating. That's the knot this link http://www.hudson-family.net/knots/knots.html calls the Locking Sheet Bend.

Pros:

- near-perfect lead in one direction, and presents a fairly slim face to any possible snags.

- stronger than the Overhand Bend

- probably more secure than the regular Sheet Bend under jerking loads, but it should be backed up by tying overhands with the ends around the standing part.

- easier to untie than an Overhand Bend or a Double Fisherman

Cons:

- more complicated to tie than the Overhand

- must be tied facing the right way

Anyone want to do some testing? In the lab or on the rock face, your call.

[Dan Lehman]

Originally Posted by rickc

I am interested in any testing results anyone knows of for the Strait Bend (pg 72 of the Apprentice). My specific use for this knot would be to join two 8mm to 11 mm nylon climbing ropes. The joined ropes would be used for rappelling. Typical forces are less than 1000 lbs force but with considerable possible jerking as the line is loaded and unloaded.

Why ask for (often dubious) test results, when you have all the means to do your
own testing --YOUR particular paired ropes, you body mass, and the ability to tie
up a 2-to-1 crude pulley system (using a 'biner) to increase applied force. Indeed,
your own non-pullied mass is approximately itself double the forces to be expected.
And yet it's common for folks to ask for some break test, which is hardly relevant
to the act of abseiling!

cf the discussion of a better analysis of the common abseil-ropes joint, and some
alternatives that are also *offset*, here : http://www.rockclimbing.com/cgi-bin/...set%20fig .9;

I am unhappy with the knot currently being recommended by many in the climbing community and am looking for a knot with a good lead, is relatively easy to untie after loading, is reasonably strong, and is secure under load cycling.
Thanks for your help in advance.
Rick C

Let me guess --you don't say-- that the "knot currently being recommended by many"
is the infamous "EDK", better named "offset water knot" (i.e., a water knot, aka ring bend,
aka --to some-- and (double) overhand knot, loaded in the *offset* manner --both ends on one side).
And it fits the task arguably better than any other : easily/quickly tied (rappelling comes
sometimes at late hours with fatigue, or pressure from approaching weather), compact
and **offset** --making for easy flow over rough surfaces, less prone to snag--, and, to
your particular question, it's an asymmetric knot enabling it to work better with
unequal rope diameters, properly orienting those ropes in the knot.

The [offset water knot] everyone else was using tends to roll, and people would end up leaving ridiculously long tails, or tying another overhand in the tails, to feel safe. I thought it better safety to have a decent bend properly tied.

"Tends to roll"?? To my awareness, there are no reports of failure of this knot, beyond
one of dubious accuracy of some fellow followed by two women. One might consider
the popular and regular usage of the knot for decades to constitute sufficient testing.
Then, again, one can yet wonder if there is some vulnerability awaiting tickling!? But
if you can tie these other suggested knots --none of which is offset, so lacks that benefit--,
you can surely learn to tie the offset water knot to advantage!

The Zeppelin bend is also very good, and will cause your climbing buddies some eye-popping concern.

Firstly, are you entirely comfortable with the comparatively *airy* (i.e., gaps in the knot)
zeppelin being immune to snagging and being pulled open? --no, not in use, but in the
pull-down of rope, which though unlikely (immediately) fatal, would surely be a major
disappointment (leaving one rope untied well up the wall).
As for impressing your partners, while that can have its element of fun, it has obvious
drawbacks, practically (mutiny comes to mind). There is comfort in the familiar.

... these bends seem to be every bit as secure as a Double Sheet Bend, ...

!!
Considering Dave Richards's testing which found this as well as the single sheet bend
AND single fisherman's knot to slip (at relatively high loads --way above what even obese
climbers would generate), I'd not cite it as a model of security; it is i.p. hardly so secure
when slack, esp. in the kermantle ropes at issue here.

it's not exactly true that the Strait Bend is an Alpine B[utterfly] with the loop cut. I think it's more accurate to say that the two knots are structurally analogous, in the same way that the Bowline and Sheet Bend are.

??! That's exactly the relationship between butterfly bend & eyeknot ; whereas, with
the other two, the match is inexact in that the sheet bend is typically recommended
with tails (resp. standing parts) on the same side --not what results from eye cutting.

The interesting thing in this test is that mostly the [butterflyknot didn't break. The line broke at the attachment to the test fixture. This is a pretty good example of the frustration of trying to find good data on the strength of knots. But as they said, the knot is very strong.

Again --to emphasize--, for rappelling, one is NOT NOT NOT concerned with strength
(unless you're using dental floss?)! You cannot make a knot weak enough in normal
abseil ropes to be at all a risk in strength. (But this dubiously got datum nevertheless
captures the imaginations ... .)

The breakage at the bollards cited in the Bushwhackers report sure surprises, but it
can be conjectured to have this basis : the knot was tested as the joint forming a round
sling in one rope; the sling was relatively short (because of test-device stroke), and
the compression of the knot in loading made a significant imbalance between forces
on the two sides --knotted & straight-- of the sling such that the knot was protected
from actual high-as-there-were forces. --something I'd have expected with the
grapevine (dbl.fish.) bend, but that report found the former feeds out more material.

I wonder if the Tucked Sheet Bend, aka Binder Twine Knot, is worth investigating. That's the knot this link http://www.hudson-family.net/knots/knots.html calls the Locking Sheet Bend.
Pros:
- near-perfect lead in one direction, and presents a fairly slim face to any possible snags.
- stronger than the Overhand Bend
...

No, the "lead" isn't so good; you can verify the benefits of an **offset** end-2-end knot
but pulling it around a sharp corner (of a desk, e.g.); non-offset knots can hang up.
And "stronger ..." is in a practical sense false : no knot will be breaking, so = strength.

I question its low-load & when-slack security --thinking that the bight (U-part) is liable
to pull out.

When doing multiple rappels all in a row, the rope you must pull on alternates, so the lead would be alternately fair and foul.

Why ... ? It has been argued to pull the haul line if that is the smaller line conjoined
with the climbing rope (to make the retrievable, twin-strand abseil line), as the end-2-end
joint would be placed to snug against the rap-ring upon *slippage* got by virtue of differing
rates of flow through the abseil device --and one can't pull the knot through the ring.
You retrieve the two tied together : why would you set them up any differently than the
prior time, and want to pull in the opposite manner (?) (There could also be a question
about which rope you would rather have stuck, if that happened, and which in hand.)

--dl*
====

[Dan Lehman]

[snipped from Reply, over quota ...]

This one, sadly, resonates as true. It's a patronizing, even contemptuous motivation, like teaching people pidgin English, because they aren't intelligent enough to handle real English. Those climbers, by and large, are not stupid; they just aren't familiar with knots. And even really simple knots can be --and are, sometimes-- tied incorrectly. So climbing instructors are perpetuating inferior knots for everyone, for no good reason.
Rising nobly above this situation, I would stick to the question, of what is a good bend, and this can be answered with hard data. I'm a bit overextended on tests at the moment, but if anyone out there wants to pester someone into doing tests, you are looking for both strength and security.

It's a tough question, at times : to choose the *safer* path and guard against possible
mistake can be seen to protect ignorance from being overcome. OTOH, one can point
to mistakes happening. (I recall being amazed at RC.com folks not comprehending the
diff.s between square & granny & thief & whatnot/grief !) Some SAR (et al.) folks insist
on a "back-up"/"safety" knot --to make any failure overcome two tyings.

But it's also arguably presumptuous to claim to know better than what has been used
now for many decades by thousands and thousands of rockclimbers. How much testing
are you going to do, to achieve that frequency? --though done w/o special notice to
the particular form/geometry of the knot, still, with such numbers, it's hard to think that
varieties escaped some use.

For the latter, note that many knots can be "dressed" in more than one way, most often in how the ends lay inside the knot. With the Strait Bend, for instance, they lie alongside each other, and either one might be "on top."

Indeed, as my RC.com reference at the top shows, even the TIED offset water knot
can be *dialed* into differing orienations, where at one extreme the thin line loops back,
and the other extreme it arcs forwards with the thicker rope looping : does that matter?
(unlikely, re security & flyping, at expected loads). The butterfly --known earlier as
the "lineman's loop"-- was specified to have its eye legs (tails, were it end-2-end)
crossed a particular way, by discovers Wright & Magowan (1928); but it is seldom
presented in this way, usually with the simpler ends/legs-abutting orientation. Similar
variations exist for Ashey's bend (#1452) & #1408 & the zeppelin.

Back to those usually urged "ridiculously long tails" of the infamous "EDK" : yes, that
has the likeness of saying "oh, that street's perfectly safe at night --just wear a flak vest
and carry an AK-47". Rather than leave such material in case ..., my urging is to DO
something with it --and tying off the thinner (if ...) tail around the other, with an overhand
snugged to the main knot, puts use in the structure, preventing the feared rolling,
rather than being there (at some remove) to somehow nip it in the bud should it occur.

But back to my early point : for all the loading this knot will see in practice, each person
has the ability to do meaningful testing, loading, bouncing, knocking about their own
knotted ropes, variously tied. And I think that just focusing on the "EDK" and tying it
purposefully will be the right course --advance past superstition, and decline the novelty
knots conjectured as somehow better.

--dl*
====

ps: Re Tom Moyer's testing, one can see that even with the offset fig.8, the more
risky knot --more vulnerable to flyping--, it took some load to flype it.
(I see his note

Dan Lehman has also proposed some variations of the overhand to me that look very promising. They keep the asymmetry and are all probably much harder to flip than the overhand. If I get any spare time I will test these and post the results.

Spare time has been too scarce, in a decade --and counting !

[benz]

Hi Dan,

I won't insult you by suggesting that you've never done a long series of rappels and thus don't know why the pulled rope alternates--I'll just say that I forgot the discussion was about ropes of different diameters. I find the very best way of doing long routes (and descending therefrom via rappel), is to lead with two 3/8" ropes: no issues of different diameters to tie or cause troubles with the rappel device; no trail line to manage, and an alternate pull on each successive rappel makes for maximum eficiency in my opinion.
If as you suggest the EDK need be backed up by tying the smaller rope around the larger, we no longer have a perfect bend--we have one that requires a back-up and the extra bulk that that entails.
If you have not seen an EDK roll a little as it is weighted, I congratulate you on having partners who draw it up most carefully as they tie it: not all my partners have been so fortuitous.
I have no idea how long the EDK has been popular in Europe, but in Yosemite I did not begin to see it until the late nineties. Before that I can testify that the popular knot in those parts was the double fisherman.
I would not call all the above-named bends novelty knots: most have existed for longer than climbing has been popular, and the climbing world still has much to learn from the sailing and rigging world. And they've taught us sailors nome neat tricks in their turn.
My favorite bend for rappel ropes is still the Strait Bend, and while I'm indifferent to what other climbers wish to tie, it is the one I will always use. Does a nice job with docklines, too.
Climb safely,
Ben

[Dan Lehman]

Originally Posted by benz

Hi Dan,
I won't insult you by suggesting that you've never done a long series of rappels and thus don't know why the pulled rope alternates--I'll just say that I forgot the discussion was about ropes of different diameters.
//
an alternate pull on each successive rappel makes for maximum eficiency in my opinion.

But you could edify (for all of the readers)!
I still can't imagine why, and will note that it entails ensuring, each time that
the knot is on the proper side of the rap-ring/sling for the altered order.
Or is there some issue with torsion & kinking/rope-handling?
(But, yes, the OP is concerned w/thick-thin ropes.)

If as you suggest the EDK need be backed up by tying the smaller rope around the larger, we no longer have a perfect bend--we have one that requires a back-up and the extra bulk that that entails.

That's just a particular way of seeing this knot as compound or not --one could argue either way. As for bulk, it remains a compact small knot (the added overhand being in the thinner (or more flexible) line, and being half of what has been suggested by one of the above references --of repeating the base knot). And in either of these cases, one at least has a smooth-*flowing* *offset* knot.

To the question of the need for that, and of rope-pulling problems in general, I've seen the on-line discussions garner testimony such as Moyer's that there have been few if any problems (using whatever), and of those that occurred, a different knot wouldn't have mattered. .:. a big "YMMV" situation.

If you have not seen an EDK roll a little as it is weighted, I congratulate you on having partners who draw it up most carefully as they tie it: not all my partners have been so [careful].

But there is something inconsistent with remarking that as simple knot as the EDK cannot be assuredly tied while urging that a rather non-simple Butterfly bend be used instead! To my mind, it is better to retain *extant technology* (here, the overhand) and infuse in its use the purpose of its parts --being offset (and easily/quickly tied), being drawn snug with special focus on the part making the initial choke (where the thinner line should be) which is the line to be tied-off around the other's tail, for surety.

I would not call all the above-named bends novelty knots: most have existed for longer than climbing has been popular, and the climbing world still has much to learn from the sailing and rigging world.

Those I had in mind would be the butterfly & zeppelin end-2-end knots --though the former, in eyeknot form, was known 1928 even in one climbing source and regurgitated by Phil Smith's ca. 1960 book, and the latter seems to have surface ca. 1970 (its history w/airships being doubted), neither has been of much note in any practical application. And, of course, Ashley's quite like knots #1452 & #1408 (and the more slack-secure #1425!) saw daylight of published knots by 1950, but are scarce "in the wild," to my awareness. The cordage of sailing and climbing differs. Sailors have no qualms about using a bowline w/o further precautions; climbers had better add some security!

My favorite bend for rappel ropes is still the Strait Bend, ... it is the one I will always use. Does a nice job with docklines, too.

Ben, why not Ashley's #1452, 1408, 1425 or the zeppelin? It struck me as odd to use the butterfly in a situation when its asymmetry wasn't necessary (for tying) --go for a symmetric knot!
As for butterfly orientations, what looks best to me I think is crossing the tails, where --from the perspective of the knot w/tails UP, standing parts entering with first crossing UNDER their collars --and so then being horizontally parallel--, to have the LOWER line's tail be oriented adjacent to its standing part, the other tail crossing behind it. This makes the lower line's overhand take a *pretzel* form, and the other's a sort of *minimal timber hitch* form. The curvature of both lines into the knot looks good, and it seems to retain the easiest form to untie.

--dl*
====

ps:

... is to lead with two 3/8" ropes ...

Oh, how yesterday !! Hip, modern climbers are much sharper, able to discriminate between fractions of a millimeter --"Would a 9.4mm be okay, or should I carry a heavier 9.8mm ... ?!" !! (Older climbers cannot resolve as fine as even a whole millimeter, let along fractions thereof.)