Splice Whipping--an Experiment

[moray]

What good is a whipping on a splice? Is it just a showy gimmick or does it really contribute something to the integrity of a splice? I decided to do some simple experiments to find out.

First some background. I have been experimenting with ropes and knots and (especially) splices for over two years now, and the simple experiments I report here are a small extension of that work. There is a long thread of mine on ArboristSite called "Splice Squeeze Force" that is most relevant to what I describe here.

On the Samson Web site you can find a PDF file on lock stitching and whipping procedures for finishing splices. Interestingly, the lock stitching instructions and diagrams are entirely sufficient for anyone to follow correctly, guaranteeing a good result. The whipping instructions and diagrams are another story. They are vague and ambiguous--they don't even tell you which end of the splice should receive the whipping! There is no indication as to how tight the whipping should be, or even whether tightness is a good thing!

Samson also publishes explicit splicing instructions for various types of ropes. For Class 1 12-strand rope like the Tenex I report on here, the instructions clearly say the splice must be lock stitched to finish it. The double-braid instructions also call for lock stitching. Neither calls for whipping. One is left with the strong impression that Samson doesn't think much of whipping, but they tossed off some sloppy instructions so that anyone who wanted to could make a pretty whipping.

I mention all this because it is interesting, not because Samson's disregard for whipping has anything to do with my own opinion. It will turn out that their disregard is probably justified, but we won't know that until we do the experiments.

 

[moray]

The picture shows one of my rigs from the experiments on splice squeeze force. The rope is 3/8 inch Tenex Tec (Samson) with a specially treated open end. There is another layer of tape under the one you see, applied when the rope had swallowed a full-diameter buried core of the same rope. That inner layer of tape essentially holds the rope open; the outer layer of tape just holds the loose yarn ends back out of the way. The idea is to have a permanently open end that allows easy insertion of various cores but will never interfere with an experiment by squeezing down on the core. Quick and dirty, but it works.

For the whipping experiments there were 4 tests--two with whipping and two with stitching. Each test involved one treatment at one of the two locations marked by arrows. The buried core in every test was 12 inches of the 3/16 inch Amsteel Blue shown. The points "E" and "T" are, respectively, about 1 inch from the end of the bury and the throat of the splice.

The actual test in each case consisted of measuring the force needed to pull the core out of the Tenex.

 

[moray]

This picture shows a whipping at "T" ready to test. I did my best to make the whipping tight (probably at least half as tight as the absolute maximum I could have managed), and I did my best to make an identical 6-wrap whipping at "E" for a subsequent test. I wanted a middle-of-road tension in the whipping because I figured that would be a good match for what an average person might do. I toyed with the idea of building some sort of jig to give me a measured uniform tension in the whipping, but since no one else actually does it that way there seemed little point in going to the trouble.

For the two stitching experiments, I used some really weak sewing thread, previously measured several times at 2 pounds test. There were 4 stitches, all in the same plane and close together (by "stitch" I mean one needle pass through the diameter of the rope). The final exit point and intial entry point were right next to each other so I simply tied the ends together with a square knot. Even though the stitches were snug, there was minimal tension in the thread. As with the whipping tests, one stitching test was done at "E" and the other at "T".

 

[moray]

Here are the results, in pounds:

Whipping at "E" 4
Whipping at "T" 18

Stitching at "E" 10
Stitching at "T" 80

Two facts jump out. One, a whipping or stitching at the throat was much more effective than the same treatment near the end of the bury. Two, very few stitches of very weak thread were much more effective than more wraps of a tight whipping.

Even though the stitching and whipping aren't directly comparable, it is easy to see that a significant number of stitches of very strong yarn (Samson calls for 12 stitches of the rope's own yarn, or equivalent) will be far more effective than any amount of whipping. Consider the rest of the balance sheet:

1. Stitching is fast, easy to apply and requires no skill.
2. A whipping, with all its exposed surface, is more vulnerable to being cut.
3. A whipping becomes looser and less effective when the rope is tensioned and shrinks in diameter.
4. A whipping is an unknown quantity--you don't really know how tight it is so you don't know how hard it is squeezing the core.

In spite of all of the above, I frequently use whippings in applications where they really perform a useful function, but as you can guess, I never use them on my splices.

One could criticize this tiny experiment for being too tiny to draw any meaningful conclusions. I agree. But the more extensive related experiments on splice squeeze force which I reported on ArboristSite are entirely consistent with the results above, and tie everything together with a coherent mathematical theory. But evidence rules! It would be great if someone else would do some experiments of their own and report the results here.

 

[pantheraba]

Moray,

Thanks for taking the time to post on this..it is an interesting topic. I have taken a splicing class from Nick and he taught the stitching to us beginners. Your results make sense to me...I'll be watching to see where the discussions go.

 

[Blinky]

YEah... but whipping looks very cool.

 

[lumberjack]

Whipping or stitching in and of itself can only hold x amount. Putting it at the end of the bury is near that ammount.

Putting it at the throat tensions the outside line, causing it to suck down on the inside line (chineese finger trap).

That's my take on it.

 

[moray]

Exactly right, lumberjack.

Mathematically, it turns out the squeeze force or Chinese finger cuff effect, works in an exponential fashion. Translation: each extra inch of bury adds a fixed percentage to the holding power of the splice. That's why the holding power of the stitching at the throat is multiplied by all those percentage increments to give greatly increased splice strength. The holding power grows inch by inch just like a bank account grows year by year due to compounding interest.

 

[MasterBlaster]

Hey Moray, do you know David Bragg? He lives in Appleton...

 

[moray]

No, that would have been a real long shot. I live a good hour west of Appleton...

 

[MasterBlaster]

He has a small tree service.

 

[moray]

I actually do like whippings. I like putting a pull-loop in the ends of my climbing ropes, and a whipping is an excellent and pretty way to do it. Once the pull-loop is in place, the rope can easily be pulled over a crotch or through a pulley. A retrieval ring, as shown, can be attached to the loop for retrieving a two-ring false crotch--a method that has never failed me. The connection is very strong--easily able to support my weight.

To make this rig, first pull about 4 inches of core out of the rope with pliers and snip it off; then milk the cover back into position. You now have a 4-inch pocket in the end of the rope. Make the loop out of any suitable cord by tying a bowline and cutting the ends short. Push the knot end all the way to the end of the pocket. Install the whipping between the rope end and the knot (Arrow points to the knot). Done.

 

[MasterBlaster]

A pull-loop in the ends of your climbing ropes? Where did you come up with that?

 

[moray]

Hah! I can't tell from your question, MB, whether you mean "What kind of bone-headed numbskull dipshit idea is that?" or maybe "That's kind of cool."

My own idea. It has saved me tons of trouble in many scenarios.

 

[NickfromWI]

Moray- That's a swell idea. I've spliced small reeving eyes ropes before, but that's usually with the cover of the rope. I like your loop+knot+whipping idea.

If you made the loop just a bit bigger you could girth hitch the ring off an on rather than having that extra piece of string you used to tie the ring to the loop...but then you'd have a longer, annoying loop at the end of your rope.

Cool!

love
nick

 

[jamie]

Moray

My take of standard whipping (wraps around the rope like samson suggest) is that the technique is historical and was to help seal the end of old ropes, simply to stop them fraying. It would be cheap and easy to replace, i'm pretty sure you couldn't melt the ends of hemp cotton or sisal.

The lock sticth that samson advises is to help hold the splice together at super low loads. The whipping over this lock stitch was to provide a cheap and easily replaceable cover to protect the lockstitching (in my opinion).

Yale created the whiplock where the whipping and the lock stitch are combined into one neat package that is easy to inspect and still looks good.

Back to my original point on historical whippings. have you tried searching for moku whipping? or french whipping? those early sailors had a lot of free time.

Jamie

 

[moray]

Moray- That's a swell idea. I've spliced small reeving eyes ropes before, but that's usually with the cover of the rope...

This is over my head. I looked up "reeving eye" in Ashley, but that doesn't seem to fit what you're saying. Do you mean just a small eye you cook up from a few cover strands to use as a pull loop? Hmm... never thought of that.

 

[Wagnaw]

I like moray's idea with the little loop. Less likely to get snagged when pulling it around a tree, and with the knot he used to connect the ring, he could always make it real close to the little loop.

Cool idea.

 

[moray]

...The lock sticth that samson advises is to help hold the splice together at super low loads. The whipping over this lock stitch was to provide a cheap and easily replaceable cover to protect the lockstitching (in my opinion)...

Back to my original point on historical whippings. have you tried searching for moku whipping? or french whipping? those early sailors had a lot of free time.

Jamie, I think your historical point is well taken. The Ashley book has tons of drawings of unbelievable splices and whippings and what have you, but they are way beyond my pay grade.

You raise two interesting points. Protecting the stitching with a whipping would unquestionably work. I'm just not sure how big an issue that is. I'm starting to fool around with some stitching experiments right now to further explore this.

The "super low loads" idea is to be found all over the place, but I think it is misleading. No splice is going to fail or slip at low load. A hollow-braid splice (e.g. Tenex) is easy to pull apart by hand (low load) if it is not stitched. It comes apart not because the load is low, but because it is 100% unsymmetrical--all the load is on the core leg of the eye. Even though it is unlikely--maybe nearly impossible--to load an eye that way in normal use, stitching the throat can protect the splice if this should ever happen. How strong must the stitching be? In my experiments on splice squeeze force, I determined that the splice force ratio (to coin a new term) for 3/8 in Tenex is about 40:1. What this means is that for a standard length splice, each pound of holding force you supply at the throat is multiplied over the length of the splice by a factor of 40, giving 40 pounds total holding power. Thus just 3 stitches of my crappy 2-lb. test thread can support a 240-lb. load!

I don't worry much about a completely unsymmetrical load on my eyes, but I do put in typically 10 or 12 stitches of 70-lb. test polyester yarn. This is much weaker than the yarn recommended by Samson, but still represents tremendous overkill for the worst possible loading scenario.

 

[Al Smith]

Back to my original point on historical whippings. have you tried searching for moku whipping? or french whipping? those early sailors had a lot of free time.

Jamie

That would fall under the catagory of "marlinspike seamanship " Very old school fancy work using "white line " It's almost a lost art now of days .I did a little of it in my sea going days which were much after the hemp rope days but before braided line was thought of for anything but a clothes line .

 

[jamie]

Mr Smith,
I like all the 'old skool' (gotta be down with the kids) whipping and that. I feel it adds a touch of class, individuality and character to modern splices. Why lose the decorative elements. I've spoken to independant comercial splicers and they were telling me core dependant ropes (Vectran etc) are beginning to get 'spliced' using wedges and eyes (like a hook and eye combo on the end of a winch wire). that is all off topic though.


Moray,
I'm not sure about how much protection the lock stitching recieves from the whipping. My opinion is that Samson tell you to do it out of good practice and offering complete instructions.
You may be right about asymetrical loading but i'd be much happier using a splice that has been whipped locked or lock stitched. When i do locked brummels on tenex i always whiplock the buried tail down for two reasons;
1. in case the tail manages to come out and unbraid
2. I can add a little extra to the splice with some tidy whipping.

Back to your original post. I'd never expect whipping alone to hold a splice at anyload no matter where it is applied to the splice. I'd only ever apply lock stitches or a whiplock to the throat as that is where the rope braiding is least disturbed.

What is your Ashley book?
I've often thought about small splices in the tail end of climbing ropes for sending gear up but it's easier to send em up on a slip knot

Jamie

 

[Al Smith]

I have a chunk of 5/8" some type braided line ,about 100 feet . It says on the reel non splicable so I "served " [whipped ]an eye on the end for a wire pulling rope .It holds just fine ,never had a bit of trouble with it comming apart .

Now I would not trust such a thing for a life safety line of some sort but for it's intended usage it suffices . I'll get a picture of it when I get a chance .

 

[Al Smith]

Oh,while I'm thinking about ,some of our safety lanyards which are factory assembled come with a "shrink tube " type of thing over the ends of the eye splices .Perhaps a more modern method of serving or at least doing one in the same .

 

[rfwoodvt]

...but I think it is misleading. No splice is going to fail or slip at low load.

Can't agree with you on this one completely.

Over time with the loading and unloading of the eye you will see the tail creep out if it is not stitched. The reason is exactly what was mentioned regarding unequal loading. That sort of back and forth motion can work the tail out.

I ran into this with my early brummel eyes. I figured since it was self locking there was no need to stitch the tail. After a while the tails all crept out. Now I know better.

I also see this happen with polypro rope splices that have not been stitched.

Peace!

Rick

 

[moray]

...Over time with the loading and unloading of the eye you will see the tail creep out if it is not stitched. The reason is exactly what was mentioned regarding unequal loading. That sort of back and forth motion can work the tail out.

I ran into this with my early brummel eyes. I figured since it was self locking there was no need to stitch the tail. After a while the tails all crept out. Now I know better...

Very interesting report, Rick. This is a failure mode I was not aware of. I knew knots could swallow their tails over many load cycles--I've had it happen to me. I read an interesting experiment on water knots tied in 1-inch nylon webbing. Under repeated load cycles both tails were observed marching through the knot at about .001 inch per cycle. I never ran into the creep failure mode you mention because I always stitch my eyes...

From now on I'll say it this way: "Unless the throat of a hollow-braid splice is stitched, the splice can creep apart over many load cycles, or come apart suddenly due to highly unequal loading." Thanks for your input!