Author Topic: Method to increase the security of adjustable hitches  (Read 4631 times)

Valentine

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Method to increase the security of adjustable hitches
« on: October 17, 2013, 10:21:49 PM »
I was looking for an adjustable hitch that can hold securely against heavy strain and shock on stiff/slippery rope, with a preference for a form that could be extended with extra wraps to hold in more demanding situations while avoiding difficulties with cinching and untying after loading. Not finding one that would hold on some slippery twine I have (think heavy-duty dental floss), I devised an arrangement of several cow hitches tied along the standing part. This holds on that twine and everything else I've tried (even without any initial tightening) given enough cow hitches. To improve efficiency of rope use, I use a taut line (the ABOK #1857 version) to secure the last link and ensure that the entire length of the knot can hold tension if needed, resulting in a knot I have called the chained lark hitch in my references (because the knot I've found that it most closely resembles is a lark's head chain from macrame). A similar setup should also work for other adjustable hitches. My question to the community here, since I lack testing equipment and enough experience with knots to judge for myself, is is this knot actually secure against major shocks and strain to a large percentage of the rope's breaking strength, especially on difficult rope? I'd like to have some feedback before I use it to secure something consequential.

The photo is a chained lark hitch tied in some 3mm paracord that won't hold a taut line. The lower view shows how the alternating loops of the cow hitches cause the standing part to bend back and forth. Under load, the magnitude of the bending decreases away from the eye as stress is transferred to the standing part.


Sweeney

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Re: Method to increase the security of adjustable hitches
« Reply #1 on: October 19, 2013, 09:08:34 PM »
Welcome to the forum Valentine.  You specify an adjustable hitch but it's not clear how you want to adjust it - the pictures imply more of an adjustable loop arrangement. It might help if you can be more specific as to the application you have in mind.

Barry

NotSure

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Re: Method to increase the security of adjustable hitches
« Reply #2 on: October 19, 2013, 09:41:36 PM »
Hi Valentine and welcome!

That's an interesting idea you have there, and performs as one would expect from, basically, multiple Bell Ringer loops linked together... Not bad. And it's a very good slider as well, when you need it to be, that is.  ;) Many people use less than this arrangement in their Trucker's Hitches (for a Bell Ringer type of sheave), so I would hazard a guess that this should be plenty strong and secure enough for most loading you throw at it...

Here's a friendly suggestion though, try using standard half-hitches instead (aka Clove Hitches). It's generally accepted that these are superior, security-wise, in comparison to the cow/lark hitch. When I tied this with clove hitches, it seems to slide just as easily.

Yes, I find most types of ropes won't hold a taut line hitch. At least not very well, IMO. It's actually a minor pet peeve of mine that that particular hitch has such a foot hold with so many instructors as THE slide and grip knot to use when there are so many better options out there. >:(

Strength-wise, as in approaching rope breaking strength numbers, (if that's what you're after) I think you're better off with a style of hitch that slowly starts to squeeze the standing part in a series of round turns first (as opposed to starting off immediately by pinching and applying pressure to the standing part with nipping turns). Slide and Grip knots like the Icicle Hitch, Well-Pipe Hitch and Sailor's Gripping Hitch are what I'm referring to specifically. I could be wrong though, as I haven't done any serious testing to confirm this theory... Usually I'm only concerned about a knot's strength rating when it comes to fishing. Then it's a bunch of other (permanent) knots that would come to mind, mind you, they're not slide and grip either.

As for security and grip on slippery stuff, the Gripping Sailor's Hitch is unrivaled in that regard. Well that's my personal opinion anyway. There's only a single tuck when you've finished tying it, so it's an easy enough procedure to simply un-tuck it and add more wraps to increase the grip if needed, then you can finish it up with the same tuck again. Easy-peasy.

Well, food for thought.

Cheers!
« Last Edit: October 19, 2013, 11:47:55 PM by NotSure »

Dan_Lehman

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Re: Method to increase the security of adjustable hitches
« Reply #3 on: October 20, 2013, 04:41:55 AM »
Here's a friendly suggestion though, try using standard half-hitches instead (aka Clove Hitches).
It's generally accepted that these are superior, security-wise, in comparison to the cow/lark hitch.
When I tied this with clove hitches, it seems to slide just as easily.
"Friendly", yes, but I think also unwise : the security
wanted here is against slippage; the security asserted
for the clove vs. cow is I presume for end hitches, and
against coming untied.  So, the test is that of which
resists slippage : tie each in opposite ends of some
lines and pull --which slips vs. the other?
 ;)

Okay, I just tried this, using some slippery nylon
binding cord (commercial fishing stuff) about 4mm?
Got both to lose/win --even, mid-test, retightening
the losing one to be then winning!?  --which is to
point out the vagaries of tying/setting.  I should
point out that I got rather quick slippage, IMO,
which is discouraging : oh, had 5 of the half-hitch
nips and then a closing rolling hitch --which I put
in matching clove/cow orientation of its finish.


--dl*
====

Valentine

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Re: Method to increase the security of adjustable hitches
« Reply #4 on: October 21, 2013, 06:28:29 AM »
You specify an adjustable hitch but it's not clear how you want to adjust it - the pictures imply more of an adjustable loop arrangement. It might help if you can be more specific as to the application you have in mind.
The loop goes around (or is tied around) a fixed object, and the standing end is attached to something to be held under tension. The knot slides along the standing part to adjust the line's length to provide proper tension in the manner of a taut line. It can, of course, be used as an adjustable loop, but I'm more interested in its use as a hitch.

That's an interesting idea you have there, and performs as one would expect from, basically, multiple Bell Ringer loops linked together... Not bad. And it's a very good slider as well, when you need it to be, that is.  ;) Many people use less than this arrangement in their Trucker's Hitches (for a Bell Ringer type of sheave), so I would hazard a guess that this should be plenty strong and secure enough for most loading you throw at it...
Thank you. Securing a block-and-tackle-tensioned load that still needs to be adjustable (kind of like a Trucker's Hitch) is something I was considering using it for.

Strength-wise, as in approaching rope breaking strength numbers, (if that's what you're after) I think you're better off with a style of hitch that slowly starts to squeeze the standing part in a series of round turns first (as opposed to starting off immediately by pinching and applying pressure to the standing part with nipping turns). Slide and Grip knots like the Icicle Hitch, Well-Pipe Hitch and Sailor's Gripping Hitch are what I'm referring to specifically. I could be wrong though, as I haven't done any serious testing to confirm this theory... Usually I'm only concerned about a knot's strength rating when it comes to fishing. Then it's a bunch of other (permanent) knots that would come to mind, mind you, they're not slide and grip either.
Getting an adjustable hitch to hold to near the rope's breaking strength is mostly an academic exercise since I don't expect to encounter a situation where I would load it that heavily. I was getting at the idea of an adjustable hitch that would break at the knot sooner than it would slip, or that it would only slip at close to that load. As for the superior strength of round vs nipping turns, I agree in general, but I don't think it would be a big problem in most rope types for the chained lark hitch. If you look at the loading of the knot, the most heavily-loaded nipping turn is the one next to the loop, so under symmetric loading the tightest curves would only be subject to half the load carried by the whole knot. The nipping turns carry successively less load as they transfer stress to the standing part, which is is bent progressively less severely as its stress increases away from the loop. The chained lark hitch may not be as strong in this regard as certain fishing knots, but I'd guess that it shouldn't reduce strength severely in non-monofilament rope (though turn tightness at the loop is not much more severe than the loop of the Rapala knot, which is supposed to be pretty strong in monofilament, so it might be decent for that too).

As for security and grip on slippery stuff, the Gripping Sailor's Hitch is unrivaled in that regard. Well that's my personal opinion anyway. There's only a single tuck when you've finished tying it, so it's an easy enough procedure to simply un-tuck it and add more wraps to increase the grip if needed, then you can finish it up with the same tuck again. Easy-peasy.
Indeed, but when I tried it, it gripped the standing part so tightly that it ceased to be (easily) adjustable. Since the repeated cow hitches of the chained lark hitch don't constrict like that, it remains easy to adjust even after loading, at the expense of needing more turns to develop comparable grip strength. I was aware going into the development of the chained lark hitch of slide-and-grip climbing knots, but I shied away from them for two reasons: I had seen warnings that they did not hold as well when both the gripping and gripped rope were of the same diameter, and they tend to require (or so I had heard) careful snugging up to grip effectively, which imposes a penalty to the ease of tying and untying that grows with the number of wraps (I value ease of untying fairly highly, which is a reason why I prefer the #1857 version of the taut line over other simple adjustable hitches). Neither concern was overwhelming, but I thought I'd look elsewhere first. A gripping sailor's hitch could certainly be used in place of the chained lark hitch's taut line, with the cow hitches' share of the load reducing the tendency of the gripping sailor's hitch to squeeze too tightly. Something to consider, I suppose.

Here's a friendly suggestion though, try using standard half-hitches instead (aka Clove Hitches).
It's generally accepted that these are superior, security-wise, in comparison to the cow/lark hitch.
When I tied this with clove hitches, it seems to slide just as easily.
"Friendly", yes, but I think also unwise : the security
wanted here is against slippage; the security asserted
for the clove vs. cow is I presume for end hitches, and
against coming untied.  So, the test is that of which
resists slippage : tie each in opposite ends of some
lines and pull --which slips vs. the other?
 ;)
Okay, I just tried this, using some slippery nylon
binding cord (commercial fishing stuff) about 4mm?
Got both to lose/win --even, mid-test, retightening
the losing one to be then winning!?  --which is to
point out the vagaries of tying/setting.  I should
point out that I got rather quick slippage, IMO,
which is discouraging : oh, had 5 of the half-hitch
nips and then a closing rolling hitch --which I put
in matching clove/cow orientation of its finish.
--dl*
====
Thank you for checking this out. I had actually considered using repeated half hitches instead of cow hitches, and in my own (rather limited) investigations, cow hitches seemed to hold marginally better on the rope I was using. This seemed to be related to how each loop sat next to its neighbors. With cow hitches, each loop bends the gripped strand in opposite directions, which causes the sliding action through the knot to be shifted out of alignment with the external stress, which should enhance the friction in each loop. With half hitches, it seems that this does not work as well. Successive loops counter rather than reinforce the bending caused by their neighbors, so I would expect the friction enhancement to be less, though as you found, it doesn't seem to be a dominant factor. I do prefer the flat chainlike look of repeated cow hitches (it is a macrame knot after all) to the spiral of repeated half hitches, but that's less important than an actual difference in grip strength. On a different topic, did you check how easily the knot adjusts after tightening different amounts? It seems to me that it may be preferable to only tighten the stopper knot because while tightening the repeated hitch section can help grip, it also makes it harder to adjust the position of the knot. Relatively loose loops, as in the image I posted, still increase the knot's security without impairing adjustability. And (IMO at least), it's less work to tie a few extra loops than to snug up a long sequence of cow hitches for the same security. I think it took something like seven (loose) cow hitches to get it to hold securely in that slippery twine I have (17 loops in the whole knot, and it adjusted easily).

NotSure

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Re: Method to increase the security of adjustable hitches
« Reply #5 on: October 21, 2013, 03:47:20 PM »
... A gripping sailor's hitch could certainly be used in place of the chained lark hitch's taut line, with the cow hitches' share of the load reducing the tendency of the gripping sailor's hitch to squeeze too tightly. Something to consider, I suppose. ...

Now that is a fantastic idea! Wow, what a difference this makes. Not even a full cow or clove hitch is needed, in fact, just a single bell ringer before the sailor.

Now the bell ringer takes enough of the load off of the sailor's hitch so that it doesn't over-tighten itself anymore. This modification alone not only makes the hitch even easier to repeatably adjust than an icicle hitch, it also makes the sailor hitch easier to untie. Also, I find that the extra gripping wraps are no longer needed and a regular sailor may be tied to the same effectiveness.

Whether to tie the bell ringer in a cow hitch or a clove hitch fashion before the sailor hitch, I am still undecided about. Truth be told, I don't notice a difference either way under various loading configurations... So, I personally lean towards the clove hitch style, but only because I find it simpler to keeping wrapping all the loops over the standing parts, until the final tuck.

In my favorites list, I have taken to calling this "new" form as the Adjustable Sailor's Hitch.

Thanks for this idea/suggestion, Cheers! :)

EDIT: Bah! After further experimentation, I do still need those gripping wraps. :-[
But at least the Bell Ringer in front of a Gripping Sailor's Hitch does seem to solve the locking up problem.
« Last Edit: October 22, 2013, 02:34:09 AM by NotSure »

Valentine

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Re: Method to increase the security of adjustable hitches
« Reply #6 on: October 24, 2013, 09:56:43 PM »
Not even a full cow or clove hitch is needed, in fact, just a single bell ringer before the sailor.
I'd be careful there. I expect the extra turns of this kind of reinforcement to take percentages of the load based on the rope material, and I would expect that the threshold for over-tightening the gripping sailor's hitch is a specific load that depends on the rope and particulars of tying and dressing. This leaves the possibility that enough of a heavy load could transfer through a single loop to constrict the gripping sailor's hitch, especially on slippery rope.