Terminating Amsteel

M

Mike_Maas

Location
S.E. Wisconsin
What do you think the approximate percentage of strength loss is in terminating 3/8" amsteel with the following methods:
1. Bowline
2. Stopper knot (through 3/8" hole in steel plate), overhand knot.
3. Stopper knot, figure eight.
4. Splice to a rope snap, no thimble.
5. Direct eye to eye splice (no thimble or ring).
 
This sounds rhetorical. I'm guessing Mike can answer his own question... long time Mike. Good to read you.

I have no idea about the splices but I'm guessing strength loss for those knots will be high, like in the 40% range. Just a guess though. I'm also wondering if they would slip rather than break.

If I had to terminate Amsteel I think I would go with a bury splice.
 
Splicing maintains 90% of the strength.

I believe that amsteel actually looses upwards of 60% when knotted because of how self abrasive it is.

Now everyone run out and treat the numbers I've said like gold and rig something huge!!!
 
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Splicing maintains 90% of the strength.


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That's a general guideline, it depends on the splice. Locked Brummels aren't as efficient for instance, rope construction is another factor.
 
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Splicing maintains 90% of the strength.


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That's a general guideline, it depends on the splice. Locked Brummels aren't as efficient for instance, rope construction is another factor.

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For practical purposes a good splice is close enough to be considered 100%, don't you think?
For the locking brummel, couldn't the lock be put closer to the end of the splice(do a nice bury then the lock, follwed by a short bury) to reduce the loads on the lock and increase the strength?

How about two splices attached to each other, eye to eye? That would create a bend at the attachment point the diameter of the rope, which would be the weak point.
For the guys who water ski, that's how they lengthen and shorten the rope using sections of rope with an eye on each end, then girth hich them together.

I don't know anything about stopper knots. Anyone aware of testing on stopper knots? Intuitively I'd guess they are strong, but intuition is only as dependable as the dummy having it.
Thanks for your interest.
 
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What's your application Mike?

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I'm using a winch line that splits into two leads about 15 feet from the end. It gets used sometimes with a single lead, and others with a double, like a balancer, to pull loads straight.

I'd like to avoid heavy hardware along the line that might become a projectile if the line breaks, and then a way to quick connect the 15' leads to the winch line, and a way to connect the ends to the load.

I also thought it would be interesting to see how people are using Amsteel as far as terminating ends and knotting it.
 
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When I broke 1/2" amsteel with splice on 1 end and clove hitch at other end it broke at the knot at 15,000# Rated for 34000#

http://www.youtube.com/watch?v=JxTPHNMr9S8

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Eye opening.
Bottom line, don't knot Amsteel Blue and expect to get a high breaking strength.

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I don't agree with the exact sentence.

what else in half inch knotted still gives you 15,000 lbs? I'm sure there is some synthetic fibers, but not too many, right?

how about my 1 inch amsteel. 101,000lbs. so certain knotts might reduce it to 50,000 lbs. Should I not knot it? I think 50,000 is still plenty overkill if things are lowered correctly.
 
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When I broke 1/2" amsteel with splice on 1 end and clove hitch at other end it broke at the knot at 15,000# Rated for 34000#

http://www.youtube.com/watch?v=JxTPHNMr9S8

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Eye opening.
Bottom line, don't knot Amsteel Blue and expect to get a high breaking strength. Dyneema is an extraordinary product for certain applications.

What's your application Mike?

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I take the 34000# breaking strentgh and use 5-1 safety factor= 6800# then reduce that by 50% for loss of strenth for knots and 10% for splice and come up with a safe working load of 3000#. This is 5x less than were it broke.
I am very comfortable with this and using it in a knotted use.
 
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I believe that amsteel actually looses upwards of 60% when knotted because of how self abrasive it is.

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With dyneema/amsteel, the prob with knotting is not self abrasiveness, it's slipperyness. When pull tested, normal knots in dyneema just slip right open. It's not really "break" testing. It's "come apart" testing.

For your application, Mike, you're talking about what to do to create the "Y," right? If so, I'd "side splice" another line in with a locked brummel. One splice, should work. I don't like the "bury then put the lock further down" idea. Sounds like you're adding extra funkiness to the splice for no benefit.

If you don't like the side splice idea, I'd put an eye in the end, then splice 2 eye slings to that eye.

Hardware sling-shotting isn't a concern. This stuff barely stretches 2-3% at breaking. The rope just sorta drops to the ground when i breaks. But I feel ya on getting rid unneeded hardware. Better safe that sorry.

love
nick
 
what other ropes/fibres will produce this sort of breaking strain? Yale, New England?
I was thinking of making a (single) eye sling for rigging out of 1/2" amsteel.
Would a timber or cow hitch reduce the strength more than that clove hitch??
 
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With dyneema/amsteel, the prob with knotting is not self abrasiveness, it's slipperyness. When pull tested, normal knots in dyneema just slip right open. It's not really "break" testing. It's "come apart" testing.


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Really? That can't be true for all knots.

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For your application, Mike, you're talking about what to do to create the "Y," right? If so, I'd "side splice" another line in with a locked brummel. One splice, should work.

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How strong would two splices hitched together be? I'd like the option of removing one or both of the legs.

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I don't like the "bury then put the lock further down" idea. Sounds like you're adding extra funkiness to the splice for no benefit.

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The idea is to let the bury take the load. By having the lock on the front end, it takes the load like a knot. If the bury works up to the lock, the lock takes the whole load, right?
It seems to me the lock should be as far to tail aas possible, or maybe at both ends?
 
Mike- there's a great article by brian toss from several years ago- I think I can find it. it's in a sailing magazine where they did a bunch of testing on a bunch of different knots in high-modulus ropes. Most conventional knots slipped, some broke. It usually involved tying stopper knots in the ends of the lines. Let me see if I can find the article.

Assuming you want to occanially ditch the other leg of the Y, I'd start experimenting with knots. You could splice an eye in the main line, then girth hitch a 20' strand of rope to the eye when you want the splitter, but we know that the "drag-around end" of the wich line, which in this case would have a splice on it, would get trashed from being drug over the dirt, rocks, sidewalk, etc.

So my suggetion, Discover the best knot. If it were me, I'd probably start with a double-looped version of the sheetbend and see how that does. Yes, you'll be drastically reducing strengths of the rope- but as you've noted, you have a huge margin for error here, so you'll be fine.

I must respectfully disagree with your thoughts on why the "scooted-down-locked-brummel" would work. Your thoughts assume that the load is happenning on the eye-side of the splice, but it gets pulled from both ends- so you're moving the knot away from the piece and toward the anchor, but the piece and the anchor are holding the same amount of force. We'd have to do some testing to come up with anything inclusive.

I like this thread!

love
nick
 
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