Securing a sheepshank in dyneema synthetic line.

[Cactus Red]

I use dyneema synthetic line on both our vehicle winches. Winchs only meet the rated pull on the first wrap of the drum, so shortening a line is often required. One option is using a pulley block, or a sheepshank can be used to shorten it to the correct length. Since dyneema is super slick, a normal sheepshank will slip under high tension. My big winch is rated to 15,000 lbs pull, and having things come apart at that kind of tension is not ideal.

The line shown is 3/8" dyneema rated to 17,600 lb capacity. The item passed thru the loop is a Cinch Bone made from aluminum with a 0.75 dia at the small dia.

I've used the method shown with good results. The line will kink, but does not melt or fray, and the kinks come out on the next normal use. It also comes apart easily once tension is released.

Do any of you see anything wrong with this type of setup?

[Dan_Lehman]

Winchs only meet the rated pull on the first wrap of the drum,
so shortening a line is often required.

Sorry, but this seems to be an egregious non sequitur :
it begs the question, How is it at all of benefit to weaken
the line with a knot so as to avoid weakening the line
at the winch?!
    

Since dyneema [HMPE] is super slick, a normal sheepshank will slip under high tension.
My big winch is rated to 15,000 lbs pull, and having things come apart at that kind of tension is not ideal.

First of all, I just don't trust a sheepshank to work, period.
I have used it in my knots-stressing pulley set-up when
running to the floor (stepping to load pulley to stress knot-line)
and needing further pull (rather than re-tying ...), but that's
not a critical, high-risk application (170# on 8mm? laid old, firm,
poly-Dac line).  HMPE typically comes in 12-strand construction
which IMO is more compressible and more scary about having
a simple round-turn nip stay uncapsized.  (FYI, there is (was?)
on-line a amazing video of a double bowline, stoppered slipping
in 5/32" 12-strand HMPE --the material in the eye just *flowed*
out around the double turns of the knot!!
>>> www.youtube.com/watch?v=ZFRQcExLA34
I would expect at least similar action in the sheepshank.)

I've used the method shown with good results. The line will kink, but does not melt or fray, and the kinks come out on the next normal use. It also comes apart easily once tension is released.

Do any of you see anything wrong with this type of setup?

Is there no way to remove excess line at the winch and then
begin its wrapping with a nearly taught line?  (Eh, I guess that
this would be problematic with how to handle the mass of excess
with the winch turning --I'm thinking of a capstan where the
tail is hauled off manually while the capstan's friction enables
the high-force hauling.)
Or, what should be easier to do, working the shortening at the
"business end* of the line, making an eyeknot for securing to
whatever (or having a hitch with the excess in the tail)?!
(In light of the Brion Toss video's double bowline behavior,
I'd recommend the water bowline --a similar one, but
with the extra round turn reversed (so, unlike a clove hitch
but like the cow hitch), was tested to rupture by Toss
(and is another video).)


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ps:  I've finally untied that jammed anglers loop !   

[Cactus Red]

Thanks for the reply!

Interesting video! I know the stuff is slick, but all of my winch lines aren't that clean, and I've not experienced that type of flow with the pin in place.

The preferred method to shorten a line is by using a pulley to double the line back to the vehicle. Unfortunately, even that isn't sufficient at times to use the bottom wrap. So, we have to come up with an alternative at times.

On my Warn M15000 winch, the first layer pulls at 15000, the second at 13900, the third at 11400, the fourth at 9700. The main 7/16" dia winch line I use is rated to 22,000 lbs, so even if I lose 20% strength, I can achieve 100% of the pulling power of the winch. The 3/8" extendsion shown falls below the maximum pulling power of the winch at a 20% loss by a small margin.

It's also pretty rare that the winch is ever loaded to 100% of it's capacity. We try to avoid that if possible.

One of the other problems with adding a layer to a winch drum is having line cleave through a layer and jam the line in the winch. Using an extension, pulley or both to make the line the right length keeps that from happening.

I suppose a vehicle winch could be used as a capstan if there was a clear, clean way to keep the line from fowling. In my Dodge Power Wagon, the winch is mounted between the frame rails, and access to is it quite limited.

The sheepshank comes apart easily, I'm not sure anyother know would do the same under that type of pressure.

Mark

[Dan_Lehman]

On my Warn M15000 winch, the first layer pulls at 15000, the second at 13900, the third at 11400, the fourth at 9700. The main 7/16" dia winch line I use is rated to 22,000 lbs, so even if I lose 20% strength, I can achieve 100% of the pulling power of the winch. The 3/8" extendsion shown falls below the maximum pulling power of the winch at a 20% loss by a small margin.

But what is this "20% loss" ?!  --that's a high rating for knotted
traditional rope ; it's unheard of (but for splices) in the modern
"hi-modulus" materials of HMPE, aramids, & others --more likely
it is the residual/knotted strength, not the loss!!  (In some
testing Toss had done, 40% was the highest figure; that's about
as high as I've seen, too, with some of my own eye knots.)

One of the other problems with adding a layer to a winch drum
is having line cleave through a layer and jam the line in the winch.

In some big-ropes cases, and maybe more so with elastic rope,
the build-up of force sufficient to crush the drum can be trouble(!).
So, there are some devices designed to mitigate that build-up.

Using an extension, pulley, or both to make the line the right length keeps that from happening.

Actually, using a pulley would halve the take-up on the object,
and potentially double the need for feed into the winch, yes?!
(pull in 20', move object 10')

The sheepshank comes apart easily,
I'm not sure any other knot would do the same under that type of pressure.

Bowlines should.  (And by "bowlines" I mean eye knots with
similar structures.)  I'd try that "cow" version of the water bowline
and reeve the "rabbit goes around the tree..." collaring on
both the SPart AND the matching eye-leg (so, at least a 3rd
pass of the tail through the nipping loops of the cow base.


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[Cactus Red]

Dyneema has been tested by several companies that provide it to the 4x4 market, and find it's knotted strength to be 80% of it's original. Those are the figures posted at any rate. One of those companies, Viking Offroad is very, very particular about posting proper load limits for the equipment they sell, and does it's own testing to assure that. They are also one of the few that lists products by the minimum breaking strength acheived, and that's the only way it should be done IMO. With no set standards for the 4x4 market on equipment like there is for overhead hoisting, it's a very gray area on ratings.

Indeed, using a pulley halves the line speed and doubles the amount of force applied to the moving object. That's a basic mechanical advantage of 2:1, and while that can be handy for a seriously stuck situation, I use the pulley more frequently to keep the winch operating properly on the first wrap. Re-rigging is frequently required if the length of pull exceeds the room on the spool. Dyneema tends to melt if cleeved between wraps under high tension. It's expensive, so taking care of the line is an economical decision as well as a safety issue.

The next time I shorten a line with the sheepshank and pins, I'll try to remember to mark the knots with a piece of tape or something. I honestly can't tell you if it creeps or not - I'm never close enough to watch it under tension, and never will be from a safety stand point. I've got a GoPro, I guess I could do a test pull with that capturing the line and see what actually happens.

Perhaps I should add a second half hitch to the sheepshank to lock it as well.

Mark

[Dan_Lehman]

Dyneema has been tested by several companies that provide it to the 4x4 market,
and find it's knotted strength to be 80% of it's original. Those are the figures posted at any rate.

This is blatantly incredible : Oregon U. did studies of the ropes
for possible forestry use and found knot efficiencies/strengths
similar to what I've indicated --40% would be among the high.
And it's quite plain to see that 80% is a too-high figure for MOST
KNOTTED ROPES !!!

One of those companies, Viking Offroad is very, very particular about posting proper load limits for the equipment they sell, and does it's own testing to assure that. They are also one of the few that lists products by the minimum breaking strength acheived, and that's the only way it should be done IMO.

Viking tests with splices not knots.  (Damnably frustrating,
Google with "knots viking ..." brings up the site which then by
computer/browser & also on-site Search("knot") returns nothing!)

All of these winch-line products I'm seeing show products
with spliced eyes; I see NO mention (even) of knots.

Please provide such information as you find it (but I think
that you have simply misunderstood).

To re-state for emphasis :
1) 80% of tensile strength is HIGH for ANY cordage,
though attainable; for fishline, well, there's a bunch
of confusion to sort through on test methods and so
on, but it might be more usual.

2) LESS THAN 45% is to be expected for hi-modulus
lines --and that is a surprise (and with lower figures,
from either breakage or slippage, to be considered),
so bears emphasis!


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[Dan_Lehman]

I use dyneema synthetic line on both our vehicle winches.
Winchs only meet the rated pull on the first wrap of the drum,

This is going off-topic, but with regard to the emphasized (bold)
aspect I find the information given by one winch-line maker
to be contradictory --to wit:

The orange heat covering should go all the way across the drum
and it is very important to always have a full layer of rope on the winch drum
while winching to assure the winch line stays attached to the winch.
The friction from the wraps are what keep the rope attached to the winch.

[ www.masterpull.com/how-to-install-winch-line/ ]

!?

Seems to me that the particular method of attachment to the
winch drum will indicate if wraps are needed --by some of what
I'm seeing in winch lines pics & descriptions, the attachment
can be rather slight, needing wraps for friction.  (But were an
eye simply attached to something, then ... no.)


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[TMCD]

ABOK 1155 is the best Sheepshank one can tie IMO, it secures with Marline Hitches instead of HH. It's probably going to be ten times more secure than a regular Sheepshank in real world applications IMO.

I don't see anything wrong with using that cinch bolt or toggle though, just don't keep using it in the same place on the rope.

[X1]

ABOK 1155 is the best Sheepshank one can tie

Why ? ABoK#1156 and ABoK#1157 and much more secure, I believe, without being much more complex.

[TMCD]

ABOK 1155 is the best Sheepshank one can tie

Why ? ABoK#1156 and ABoK#1157 and much more secure, I believe, without being much more complex.

Ashley himself says this edition is the safest of the bunch. Of course ABOK 1156 & 1157 are beefed up in the middle using the Tom Fool's Knot and Handcuff Knot, so I guess they are just as secure...but Ashley never makes that claim about those knots like he does 1155.

The Marlingspike Hitches in 1155 render it very secure by trapping the line. I just tested a Marlingspike Hitch as my center knot in the Trucker's Hitch and it worked great when substituting it in the Bellringer's Knot.

[X1]

  The tensioned nipping loops at the ends of #1156 and $1157 ( that Ashley calls "half hithes" - they are not proper hitches, because both their ends are tensioned ) trap the dounle line better than the Marlinespike hitch ! ( where some portion of the nipping forces is wasted in the form of friction forces inside the overhand knot-looking nipping structure ). That is the lesson of the bowline and the Gleipnir.
  Another alternative for a safe Sheepshank would be #1166, with those Pretzel-liooking nipping structures. A Tom foul s or a Handcuff knot at the middle would dissipate the tensile forces acting on the bights that penetrate the hitches even further.

[Dan_Lehman]

I don't see anything wrong with using that cinch bolt or toggle though, just don't keep using it in the same place on the rope.

Even after I posted what was wrong?


 

[Cactus Red]

Seems to me that the particular method of attachment to the
winch drum will indicate if wraps are needed --by some of what
I'm seeing in winch lines pics & descriptions, the attachment
can be rather slight, needing wraps for friction.  (But were an
eye simply attached to something, then ... no.)


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Even a wire rope is not attached to a winch drum in a manner that will allow it to take a load without a minimum of 5 wraps. All winches that I'm familiar with, and I've seen virtually every one made for vehicle use at one time or another, use a small screw to fix the end to one side of the spool. It's not ment to hold anything at all, the wraps on the drum hold the line by friction. I use a minimum of 8 wraps on my winches with synthetic line. I suppose one could splice a line around the drum, but that is not an accepted practice.

[X1]

   Why does one have to attach the one end of the rope ON the drum of the winch, by 5 wraps (that consume a considerable length of material), and not simply connect the two ends, tie a sling - a closed loop - around two large diameter drums/pulleys ( the one being attached somewhere else. the other pulled by the drum of the winch ) ?
   I plan to measure the absolute and/or relative strengths of various bends, by connecting the four ends of two short pieces of rope ( around 1,25 m / 4 feet each) by the two bends I want to compare, pass the sling around two large diameter drums, and then pull those drums to opposite directions by a hydraulic car/truck jack. This way one consumes less material, while kreeping the symmetry of the configuration, so the friction on the surface of the drums will play no role in the measurment. Is there anything flawed in this procedure ?

[Cactus Red]

That will work, but by that method, you must remember that the force applied is halved. If you use a 20 ton jack, each knot will only get 50% (actually less) of the load. The structure will have to be well engineered to withstand the stress applied. A true hydralic ram system with proper strain gages would be the only way to know exactly what amount of tension is acheived.

One of my freinds tested winches using a massive calibrated gage several years ago for the Overland Journal. For testing bends Dyneema, you would need similar equipment.
http://youtu.be/5QQqz0vF0KQ