Strait Bend Testing?

[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.

[benz]

I like that locking sheet bend, with the exception that it only has a good lead in one direction. When doing multiple rappels all in a row, the rope you must pull on alternates, so the lead would be alternately fair and foul. Another factor in trying to sell new knots to climbers, is that lots of them are really dumb, and a euro death knot is the only one they can understand. Any bend that requires thought and care in tying is liable to be mis-tied, especially in rain or snow or darkness, with possibly fatal consequenses. So change comes slowly, because climbing instructors want to teach the easiest possible bend and so lose the least amount of students later on.

[Brion Toss]

[quote=benz;6082 ... climbing instructors want to teach the easiest possible bend and so lose the least amount of students later on.[/QUOTE]
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. 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."
Fair leads,
Brion Toss

[teknocholer]

Here are some sites with tests of the Overhand Bend (EDK) and some alternatives:

Tom Moyer http://user.xmission.com/~tmoyer/testing/EDK.html prefers a Figure 8 follow-through with safeties.

This site http://www.needlesports.com/catalogu...9-9c9e00a60c7f has some tests on the EDK (which they call simply Overhand) and the EDK with a backup Overhand Bend (which they call a Double Overhand).

This site http://www.gudelius.de/spst.htm has a couple of interesting alternatives, tested by Edelrid. The one he calls the Triple T-Fisherman's Knot looks especially easy to tie.

All agree that the Flat Figure 8 is dangerous and should never be used.