Synthetic winch rope

[flyingwil]

That is correct... it should be put on "under moderate" load. Pending brand and mounting attachment, some manufactures recomend installing by attaching the winch to an anchor and spooling it under the load of the rolling vehicle in nutral on a flat surface, while others say hand tight. It depends on the eye attachmant to the winch drum.

 

[ntsqd]

It's worth noting that a snatch block can help you create loads far greater than your winch is rated for so if you plan to use one (or more) of them you could need a serious rope.

The tension in the line is the same as the max pull of the winch regardless of how many blocks you use. It's not intuitive, but it is the truth.

 

[Halboo]

Synthetic is better than steel cable in almost all respects. (I am referring to "proper" UHMWPE ropes, not webbing or other types of synthetic that you sometimes see on winches).

Advantages:
Safer - harmless if it breaks

I don't know where you heard that but it's not true.
Twice during my Navy years I saw serious damage done by synthetic lines which had parted.
It ain't as dangerous as a busted steel cable, which I've also seen, but you still wouldn't want to be in it's way if it snaps.

 

[ntsqd]

In my experiments with the 1/4" Amsteel I saw evidence that it does contain some energy, and therefore does indeed snap back. As stated, not like steel cable can, but it does happen.

The single failure in actual winching that I've seen (over a sharp rock & the sleeve slipped, parted b4 the load could be let off) the presense of a jacket on the line caused it to simply drop to the ground. It might have recoiled a foot at the most.

 

[paulj]

I've wondered about using synthetic winch rope or extension with a hand winch like a come-along or hiLift jack. I balk at the idea of carting along 50' of heavy chain.

But there seem to be two issues:
- whether the synthetic has low enough stretch
- whether there is a way of adjusting the starting and incremental length.

I once saw a picture of someone like Bill Burke using a chain knot to shorten a line. There are some sliding knots that might be used to grab the line are different points.

paulj

 

[ntsqd]

I've no worries about the stretch. We moved an 8k lbs truck (in park & wheels chocked) with the 1/4" stuff b4 it broke. (Pulled on it with an 8274.) I would eyeballically estimate the stretch to be at or under 1%

One of the goals of my experiment with the 1/4" stuff was to find out if any of the various climbing knots that I know of would work on that type of line. They won't, at least none of medium-large catalog of knots that I'm familiar with would live.
Basically a knot's bends are too tight and they create stress risers in the line. It would appear that the stress takes the form of very localized heat when under load. The parting points looked like they'd seen a propane torch and they were always from inside one of the knots.

A splice, even a simple lateral weave splice (picture the Redart Super Strap), is the only way it will not fail under load.

 

[SEREvince]

FWIW there are companies that offer "combination" winch lines that offer the heat resitance of the aramid on the drum and the cost saving of the amsteel for the bulk of the length.

As far as UV resistance, as was stated earlier that these lines were made for marine applications, which probably is the harshest evironment possible as far UV exposure.

I'll probably throw a cover on mine, just to keep the road grime off.

 

[craig]

Lots of interesting info here. A few thoughts popped into my head as I read through the varying replies:

- The reason rope is generally safer than cable is because it stretches less than cable. It would be better, not worse, for use with a hand winch. Chain would be the best though.

- winchline.com now sells a really big rock strap that is very low stretch. This might make a nice lightweight substitute for the heave chain we are all carrying around.

- Rope stores *very* little energy. Most of the time the energy gets stored in the other components of the rigging. The tree strap being the most common "stretchy" item.

- I've almost been decapitated by a cable. I was near a rope when it broke recently. Hands down, the cable was way way way scarier. Use the same caution you do with cable with rope, and you'll be the safest yet.

- winchline.com is owned by a marine netting company and they know the line characteristics very well.

- Our group did a tech session at winchline.com last month and you can tie a knot if it is the right type. In fact, one of our club members is in the Coast Guard and he tied a rope on a recent snow run and it held for many more pulls that day. The key is to find a knot that doesn't have a lot of kinks in it.

- Re-splicing is really easy. Read the doc on the winchline.com website and you won't have to worry about tying a knot.

- A regular old knot that kinks the rope decreases its strength by 50% or more.

- Worm drive winches run a lot cooler than planetary winches

-

 

[ntsqd]

FWIW the knot I used, the "Grapevine" as I know it, is known for it's low loss of rope strength and is commonly used in climbing gear.

Didn't matter. Failed in the knot.

 

[craig]

I'll ask my friend what knot he used, and ask Jon (winchline.com owner) what knot they showed us at the tech session.

As you found, I'm sure that the knot will always become the weakest point regardless. The right knot was enough to get us home though. Next time, I'll splice it in the field though. It's a pretty simple process.

Craig

 

[Lynn]

If you want to learn the Grapevine knot, it's also known as a double fisherman's knot, and is illustrated here.

WRT knot strength, you can find a lot of different theories and speculation, as well as different charts with different numbers. My 'Alpine Search and Rescue' text states that there have been many lab tests, but there has never been a documented case of climber's ropes breaking at the knot. They have all failed due to some other reason, like poor rope maintenance, or, more often, the rope passing over a sharp edge and getting cut. Ropes under tension cut very easily, even by rocks you wouldn't think of as sharp.

Granted, the text is pretty old, but the point is valid: Know your knots, sure, but don't put too much analysis into the knot and neglect the more common causes of rope failure.

Personnaly, I would suggest that a figure-8 bend (tie a loose figure-8 in one rope, then follow it through with the other rope from the opposite direction, then tighten it down) MAY be SLIGHTLY stronger than the double fisherman's. But that's JMHO

 

[Lynn]

Oh, also IMHO, the figure-8 is easier to untie after it has been loaded...

 

[ntsqd]

Oh, also IMHO, the figure-8 is easier to untie after it has been loaded...

Tried one. Actually a Figure-8 Follow-thru. It failed faster than the Grapevine Knot. Of the knots I tried the Grapevine did the best, but it still wasn't good enough.
I was taught that the Grapevine's second main attribute is that it doesn't easily come apart after it's had a load applied. So there are places where it should be used and places where it should not be used.

Until real world testing shows me a knot, that I can remember how to tie, that works I consider poly winch lines to be only spliceable and not knotable. That's not to be an ogre about it, it's just the most conservative approach.

Taking a pencil and carefully worming it thru the line truly perpendicular to the line's direction and following it thru with the line's end, then repeat 4-5 times about an inch apart (in 1/4" line) made a fast, simple, and thoroughly ugly "splice" that worked better than any knot that I tried.

Somewhere I still have that spliced piece. It too did fail, but not in the splice. It failed in the eye created by the splice. Which brings up a point that hasn't yet been made. That same minimum bend radius that makes or breaks a knot also applies to what you loop the line around. In steel cable you can get away without a thimble. It does ugly things to the cable, but the cable will live for a while. I do not consider this possible with poly line. You MUST use a thimble or some other means that won't allow a sharp corner in the line.

 

[craig]

My friend, in the Coast Guard, that tied the knot gave me the following info when asked what knot he used...

The knot was a square knot, aka a reef knot with a figure 8 on each bitter end so that the line wouldn't slip too far... these would all work nicely... http://www.realknots.com/knots/bends.htm and stop any of those with these http://www.realknots.com/knots/stoppers.htm

In a pinch, I hope it helps.

 

[ntsqd]

At the suggestion of a friend I tried that knot too and it also failed.

However, since I am not accustomed to doing so I didn't use any stopper knots and that may make the difference.