A concern about the Arborist Splice

[RonReese]

For the life of me, I can't seem to get the slack out of the cover in the eye. The eye looks pretty good, but when I "milk" the cover in the eye from one side of the eye to the other, it bunches up some. Boy that's frustrating! I thought I was keeping tension on the cover and the core as I buried them, but something's happening.

Since I haven't stitched it yet, I presume it's possible to "unbury" and re-bury and try to deal with the tension better??????

[NickfromWI]

Originally Posted by RonReese

For the life of me, I can't seem to get the slack out of the cover in the eye. The eye looks pretty good, but when I "milk" the cover in the eye from one side of the eye to the other, it bunches up some. Boy that's frustrating! I thought I was keeping tension on the cover and the core as I buried them, but something's happening.

Since I haven't stitched it yet, I presume it's possible to "unbury" and re-bury and try to deal with the tension better??????

Ron...you're not talking about the 16 strand splice any more, are you? Sounds like double braid probs to me.

When there's a tiny bit of tension, is there still excess cover? If so, then there's a prob. If it only happens when the eye is slack, that might be normal...I'd have to see it. Just think how rope can be milked when there's no tension on it...is it like that?

love
nick

[RonReese]

Very astute, Nick, of course from your posts that I've read, that's pretty SOP for you.

I'm sorry, I was splicing Velocity again, which is double braid. I "unburied" the splice and re-buried it. I had to use one of Brion's tricks of "skewering" the rope and pulling out the slack. I think I finally got what I wanted.

Originally Posted by NickfromWI

"...Just think how rope can be milked when there's no tension on it...is it like that?..."

Impressive insight Nick, I think that's exactly what's happening - well now anyway. I think before I tightened it, the cover did have a bit of slack in it, but it's better now. I think you're right; it does seem to be a normal milking thing.

[Dan Lehman]

Originally Posted by Brion Toss

Hi again,
Dan, neither stitching nor whipping will add significant compression to add to the handcuff effect. Whipping might apply more, but even if so, whipping can be chafed away. In any event, both methods provide security through shear strength, not compression.

Maybe I'm thinking of a different whipping than is commonly employed?
Tying extended Strangle or perhaps (Dbl.) Constrictor knots in strong material enables
a good deal of tightening to be done (a man can easily pull with 60-100+ # force on the
ends). This I'd think would give good assurance against low-load shifting.

As for how we know if invisible stitching is intact, you may as well ask how we know if the buried tail of the splice is intact; of course they almost certainly are okay, as they can't be chafed externally, or degraded by UV.

What is "invisible stitching"? Don't you have to bring the thread to the rope surface both
as a methodological necessity but also in order to bind the sheath--the point of it?! And
if so, then that thread's vulnerable. (As for knowing about the bury, well, what possibly
can happen to it?)

We might as well ask why ANSI requires ...

Indeed! And the answer might be something like learning how sausage is made, not
terribly attractive. I think that Tom Dunlap (arborist) and some others have some insights
to some of the motivations behind some rules, and IIRC, they don't all seem so compelling.

The strength of arborist rope might seem needlessly high, but there are a couple of compelling reasons for it: shock loads can easily multiply a person's weight (which could easily approach more like 300lbs at times, what with all the gear that arborists take aloft);

Ah, not with diet, then.
Or maybe durability was part of the formula. (Paolo Bavaresco found some interesting
diffferences in residual strengths of various lines--some seemed to lose a lot, others not
so much.)

--dl*
====

ps: I seem to be queried for re-logging in a many steps en route to making a post,
even though I logged in once or twice (or ...) previously and got the jolly "Hello, Dan Lehman"
greeting!? Homeland Security in on the operation?

[RonReese]

Originally Posted by Dan Lehman

Maybe I'm thinking of a different whipping than is commonly employed?
Tying extended Strangle or perhaps (Dbl.) Constrictor knots in strong material enables
a good deal of tightening to be done (a man can easily pull with 60-100+ # force on the
ends). This I'd think would give good assurance against low-load shifting.

It is claimed that splices retain up to 100% of the rope's strength. That kind of strength retention, as explained by Brion, SherrillTree, Samson Rope, One Rope 1, comes from the integrity of the splice rather than the whipping or stitching method. Most seem to readily admit that whipping/stitching only serves to keep the splice from slipping at very low or no loads or from mishandling.

If the splice itself maintains nearly 100% of the rope's strength then a good, strong, tight whipping or the best stitching isn't going to make it 110%.

In fact, such tight whipping could diminsh the strength of the splice by creating stress concentration at the whipping. This is a commonly known phenomenon in structural materials and design.

Originally Posted by Dan Lehman

What is "invisible stitching"? Don't you have to bring the thread to the rope surface both as a methodological necessity but also in order to bind the sheath--the point of it?! And if so, then that thread's vulnerable. (As for knowing about the bury, well, what possibly can happen to it?)

I would think that stitching does expose a small portion of the thread to abrasion, but whipping is totally exposed, 360? around the splice. But it's a bit of a moot point since the stitching/whipping does not add strength to the splice.

Originally Posted by Dan Lehman

Indeed! And the answer might be something like learning how sausage is made, not terribly attractive. I think that Tom Dunlap (arborist) and some others have some insights to some of the motivations behind some rules, and IIRC, they don't all seem so compelling.

LOL! Well maybe. But I like sausage, and whether the means is attractive or not, doesn't change the palatability of sausage.

But really, we're just expressing opinions and I'm not sure what those opinions are based on. In my field, engineering, I commonly see things being done a certain way because they've always been done that way and nobody knows any other reason for doing it that way.

Sometimes that approach is successful, but in some cases it breaks down because it's been a bad practice all along, and nobody knew it until it showed up one day.

FOR EXAMPLE - I was hired to interface a computer to a fire test laboratory. They test the flammability properties of all kinds of materials. The idea was to computerize the data collection and calculations which I did. Well, except for one calculus based calculation which I had worked on for hours and couldn't get the same answer they got. Finally, with the "top dogs" and technical staff present, I asked them to show me how they calculate this one parameter. As soon as they showed me, I took a deep breath and said, "You know that's not correct don't you?" They didn't even hesitate to admit that they knew it was inaccurate, but that's the way they had always done it. I asked what they wanted me to do and they said make the computer calculate it the way we do. I was done in five minutes and they were happy.

So until we put our splices and stitching and whipping opinions and/or practices to a real test on a tensile machine, we're just doing what we think makes sense to us with little support other than our experiences in the field that may not ever approach critical loads like a tensile machine would.

[NickfromWI]

Would you guys splice some things, then whip and stitch in a variety of ways to have them sent to me and broke tested?

love
nick

[RonReese]

Originally Posted by NickfromWI

Would you guys splice some things, then whip and stitch in a variety of ways to have them sent to me and broke tested?

love
nick

I'm interested.

1- What kind of machine will you be performing the tests on?

2- In addition to testing whipped and stitched splices, could I persuade you to test some splices that haven't been stitched or whipped? Or, have you already done that?

3- How much rope do you need per splice?

4- Could you test a splice in each end of a rope? As I think about that though, that would place a heavy load on the rope - twice and the rope may fail superficially.

5- How many could I send you?

Since a splice has a larger cross-sectional area than the rope, it almost makes you wonder if the splice could actually be stronger than the rope????

[Dan Lehman]

Originally Posted by RonReese

It is claimed that splices retain up to 100% of the rope's strength. That kind of strength retention, as explained by Brion, SherrillTree, Samson Rope, One Rope 1, comes from the integrity of the splice rather than the whipping or stitching method. Most seem to readily admit that whipping/stitching only serves to keep the splice from slipping at very low or no loads or from mishandling.

If the splice itself maintains nearly 100% of the rope's strength then a good, strong, tight whipping or the best stitching isn't going to make it 110%.

In fact, such tight whipping could diminsh the strength of the splice by creating stress concentration at the whipping. This is a commonly known phenomenon in structural materials and design.

Lots of things are claimed, but often those claims are shown to not hold water. IIRC,
a recent arborist posting about a new "Grizzly" stitch-splice (eye) revealed a vendor claim
that it was stronger than a splice in the same material (so obviously that splice wasn't
100%). But I've not said that whipping was supposed to replace the splicing, only that it
seemed a better/surer method to guard against low-load (and otherwise) shifting. Yes, it
IS exposed--precisely my point about its inspectability, and also re use in an application
where the material is readily viewed--, but the adjacent turns of tight whipping resist
abrasion pretty well. Compared with something called "invisible" of much less material,
it seemed preferable.
Yeah, it might be that in a pure one-time break test that the point of whipping becomes
the point of weakness; on cyclical non-break loading, it might be that an unwhipped splice
yields, ultimately, whereas the whipped one endures. And which testing more accurately
models usage? You should be nowhere near the break strength in use!

In my field, engineering, I commonly see things being done a certain way because they've always been done that way and nobody knows any other reason for doing it that way.

And partly that's why I sometimes raise a question--to try to learn, to see the rationale/basis.

So until we put our splices and stitching and whipping opinions and/or practices to a real test on a tensile machine, we're just doing what we think makes sense to us with little support other than our experiences in the field that may not ever approach critical loads like a tensile machine would.

Again, the tensile machine is one measure of one aspect and not likely the most important
one. The Fisherman's knot is common in commercial-fishing/-marine use; on the tensile
machine, many other bends will test stronger, but after several months of usage, the other
knots might well suffer more damage from being knocked about, run though pot haulers,
whatever, and tested X months later, not fare so well. So, which knot was "stronger"?

----------
Nick, to your testing offer, we need more details:
1) what size specimen, & how constructed (e.g., eyes at each end, 4-7' span)?
2) where to send (etc.) (who's doing the testing?)

I don't expect to splice anything like above, but I might like to see how a seized eye tests.

Thanks,
--dl*
====

[Brion Toss]

Hi Dan,
My apprentices are currently preparing some splices to be destruction-tested. We do that sort of thing fairly frequently. We have also run cyclic loading tests on occasion. I would be happy to send along the results. This next batch will be broken by New England Ropes, but you can likely find several test facilities in any major city. Typically the samples should have at least 5ft. between the ends of the splice tails, to minimize the distorting effects that the two splices might have on the rope. And typically the eye circumference is a bit over 2ft., so they can fit onto the machine's pins. I'll look to see if we have saved any results from past tests. The most recent one was on some 5/8" Vectran, as I recall, and it broke in the high 90's, but I'll have to dig the file out for specifics.
As for the whipping vs, stitching question, experience in the field and on the testing machine confirms that stitching works just fine. You ask how invisible stitching could hold well. Reasonable question. Because the rope has opposing diagonal weaves, there's always a layer under the surface. So if I stitch such that the thread disappears between two sets of surface yarns, it will always pick up the layer beneath, as long as the stitch has any length to it. And I believe you are mistaken in saying that stitching puts less material into the rope; a whipping has 6 or 8 frapping tucks through the rope, and sometimes only 2, whereas one can stitch as many times as one wants -- though I usually say 6 to 8 is fine. Not only that, but those stitches can be made at a wide variety of angles, and can travel linearly and radially, intersecting the core in more places. As for inspectability, again, why would you need to inspect it, any more than you would need to inspect the "invisible" buried rope tails?
And yes, you could say that the splice is stronger than the rope, but then you could say the same thing about a Bowline or any other knot; there's more mass in the knot, plus you have the two parts of the eye, so that's twice as strong as the rope. Unfortunately, the bowline, and to some extent even splices, distort the rope, weakening it. The goal is not to have a strong splice --- that's easy --- but to avoid having a weak rope. Hence tapers, core/cover balance, and a general effort to minimize distortions.
I recently spoke with the developer of the Grizzly stitch splice. It's a wonderful thing, but as even the developer pointed out to me, it does have some significant limitations, including the size and type of rope you can use it on. No magic bullet here.
I do my best to have viable reasons for doing things the way I do, though of course it is always so easy to fall into dogma. For instance, for years I was emphatic about the need to taper any splice. And it almost always does make a significant difference in rope strength, as well as being less likely to chafe than a square-shouldered finish. But destruction tests on 3-strand ropes consistently showed that untapered splices were stronger.
Fair leads,
Brion Toss

[RonReese]

One more question if I may, that has puzzled me for some time. I notice that some ropes are described as spliceable on one end. How is it that a rope can only be spliced on one end, and I guess one shouldn't buy such rope by the foot or something?????

Thanks,
Ron