NickfromWI
Participating member
- Location
- Los Angeles, CA
Norm- do you think amsteel would prusik to itself? I've never tried, but it is slippery stuff...
Terminating Amsteel
- Thread starter Mike_Maas
- Start date
NickfromWI
Participating member
- Location
- Los Angeles, CA
Oh- one reason I don't like the prusiking idea: we know that spectra has very low heat tolerance. If a prusik bites down tight, then slips while under load, that could damage the rope right there.
In this application, I don't think it'd be the end of the world. I'd keep hauling with it until the line just straight-out broke.
love
nick
In this application, I don't think it'd be the end of the world. I'd keep hauling with it until the line just straight-out broke.
love
nick
- Location
- Bethel, Connecticut
We broke the end of our amsteel once and quickly tied the snap back on with a triple fisherman's knot. We broke the amsteel again 6 months later near the midpoint, the knot did not fail.
knudeNoggin
New member
[ QUOTE ]
I take the 34000# breaking strentgh and use 5-1 safety factor= 6800# then reduce that by 50% for loss of strength 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.
[/ QUOTE ]
You've slightly over-reduced: take the weakest link,
but don't add the weakenings (i.e., that 50% figure subsumes
the 10% splice loss). And thus you'd get 3,400#. But don't
assume 50% for HMPE (or, I think, other high-mod) cordage;
25% is safer!
As Nick states, a key first problem with HMPE is slipperiness.
Somewhere on this forum (either Rigging&Roping or Climbing)
Brion Toss posted some videos of his testing some eye-knots
in 5/32" HMPE 12-strand line, and --amazing to see-- a stoppered
double bowline just slid right down its eye, collapsing the eye
to the pin and the breaking !! It was as though the stopped-off
tail bight (that rabbit out of hole around tree back into hole part)
was a fig.8 rappel device being pulled down through turns of
the line! He then tested a sort of Water Bowline I suggested,
and that held, but broke at what he guessed (w/o measure)
was a low load. (Btw, his 2000 Sail article is rather scarce of
details, basicly saying Don't Knot. A follow-up Practical Sailor
article was, well, laughable, w/some similar results and some
major questions.)
Subsequently, we arranged to have several (5) of my *own*
eye knots tested, in blue urethane?-coated 12-strand Dyneema
SK-75 (the strongest present form, or was). The results were
sobering/humbling (IM*H*O) : the range was about 33%..42%,
scarcely better than an Overhand-knot-in-the-line breakage!
In absolute figures, this was 13_431#-rated 5/16" Endura-12
coated breaking at around #5_000.
(boo)
Well, heck, at least I solved the slippage problem!
But I didn't solve the untie-the-knot problem, as those knots
are darn tight. (Maybe w/a spike and some grunting ... ; but
I've not wanted to do that before further eyeballing analysis.)
*knudeNoggin*
I take the 34000# breaking strentgh and use 5-1 safety factor= 6800# then reduce that by 50% for loss of strength 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.
[/ QUOTE ]
You've slightly over-reduced: take the weakest link,
but don't add the weakenings (i.e., that 50% figure subsumes
the 10% splice loss). And thus you'd get 3,400#. But don't
assume 50% for HMPE (or, I think, other high-mod) cordage;
25% is safer!
As Nick states, a key first problem with HMPE is slipperiness.
Somewhere on this forum (either Rigging&Roping or Climbing)
Brion Toss posted some videos of his testing some eye-knots
in 5/32" HMPE 12-strand line, and --amazing to see-- a stoppered
double bowline just slid right down its eye, collapsing the eye
to the pin and the breaking !! It was as though the stopped-off
tail bight (that rabbit out of hole around tree back into hole part)
was a fig.8 rappel device being pulled down through turns of
the line! He then tested a sort of Water Bowline I suggested,
and that held, but broke at what he guessed (w/o measure)
was a low load. (Btw, his 2000 Sail article is rather scarce of
details, basicly saying Don't Knot. A follow-up Practical Sailor
article was, well, laughable, w/some similar results and some
major questions.)
Subsequently, we arranged to have several (5) of my *own*
eye knots tested, in blue urethane?-coated 12-strand Dyneema
SK-75 (the strongest present form, or was). The results were
sobering/humbling (IM*H*O) : the range was about 33%..42%,
scarcely better than an Overhand-knot-in-the-line breakage!
In absolute figures, this was 13_431#-rated 5/16" Endura-12
coated breaking at around #5_000.
(boo)
Well, heck, at least I solved the slippage problem!
But I didn't solve the untie-the-knot problem, as those knots
are darn tight. (Maybe w/a spike and some grunting ... ; but
I've not wanted to do that before further eyeballing analysis.)
*knudeNoggin*
Norm_Hall
New member
- Location
- Wauconda, (Chicago),IL,USA
[ QUOTE ]
Norm- do you think amsteel would prusik to itself? I've never tried, but it is slippery stuff...
[/ QUOTE ]
I haven't done it either.
I have some 7/16's" and some 5/16's" dyneema SK75. I'll try it and see what happens.
Norm- do you think amsteel would prusik to itself? I've never tried, but it is slippery stuff...
[/ QUOTE ]
I haven't done it either.
I have some 7/16's" and some 5/16's" dyneema SK75. I'll try it and see what happens.
- Location
- Federal Way WA
Samson rope markets Amsteel to the logging industry partly for its ease of repairing. In the winch configuration you are describing, why not keep a wire fid on hand and an appropriate length of amsteel for the spider leg and sinmply pull a full diameter bury for at least 3 and 1/2 fid lengths? It would only take a minute to splice and could be pulled out as soon as you were done. (Imagine the splice on a loopie or whoopie sling)
The remarks about the amsteel slipping rather than breaking are right on. In fact, Samson found used dyneema to break at a higher tensile than new. The trouble is the friction from slippage. If you have to use a knot that you would need to be able to untie, I would go with something from the bowline family, accounting of course for the high percentage of tensile affected by a bowline. Of course, the higher base tensile of amsteel should negate the cons of tying the knot. The biggest problem I have had with amsteel has been gettin knots untied when i have chosen to use them.
The remarks about the amsteel slipping rather than breaking are right on. In fact, Samson found used dyneema to break at a higher tensile than new. The trouble is the friction from slippage. If you have to use a knot that you would need to be able to untie, I would go with something from the bowline family, accounting of course for the high percentage of tensile affected by a bowline. Of course, the higher base tensile of amsteel should negate the cons of tying the knot. The biggest problem I have had with amsteel has been gettin knots untied when i have chosen to use them.
knots are much easier as the diameter of amsteel goes up. I've pulled hard on our 1" amsteel and many times I think to myself, "oh man, this is going to be hard to untie". But I've always been able to do it by hand, it always impresses me. When pulling that hard, I'm had to beat the knot with a hammer or maul to get the bowline to loosen up on 3/4" double braid, but the 1" amsteel i can always do by hand. Is it the material or the size?, I don't know.
Lumberjack
Branched out member
[ QUOTE ]
...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#...
[/ QUOTE ]
Why do you reduce it 10% for the splice if you're already reducing it 50% for a knot on the other end?
...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#...
[/ QUOTE ]
Why do you reduce it 10% for the splice if you're already reducing it 50% for a knot on the other end?
Norm_Hall
New member
- Location
- Wauconda, (Chicago),IL,USA
[ QUOTE ]
Is it the material or the size?, I don't know.
[/ QUOTE ]
It's the weight of the load and what the rope is rated for.
If tying a bowline in 3/4" DB and having a hard time untying it, it's being waaayyyy overloaded.
Allmark's formula will keep him and his equipment safe, and his ropes in working order for many years to come.
Is it the material or the size?, I don't know.
[/ QUOTE ]
It's the weight of the load and what the rope is rated for.
If tying a bowline in 3/4" DB and having a hard time untying it, it's being waaayyyy overloaded.
Allmark's formula will keep him and his equipment safe, and his ropes in working order for many years to come.
[ QUOTE ]
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).
[/ QUOTE ]
I have done some crude testing on Amsteel as part of an article on soft shackles. Basically I connected two soft shackles to a link of Amsteel that had eye splices on the ends. One eye was a tuck and stitch, one was a Brummel. The soft shackles were of different type. I pulled with a manual winch that had 100:1 advantage and was using 1/8 inch Amsteel, a scale model if you will. The Amsteel broke on the link center, away from the splices so my answer to what you are getting at is to use eye splices and tie things together with soft shackles. They are soft so your concern about them flying and hurting someone is less vs steel shackles. From everything I know and hear, splices are stronger than the line they are made of. I have heard the 90% number but I don't believe it. The only point where an eye splice could possibly be less strong than the line it is made of is at the point in the line where the bury ends if the taper is too abrupt. I wrote several web pages on all this including the testing and how to make soft shackles. You might find it interesting. http://l-36.com/soft_shackle_intro.php
I have also tested a bowline on Amsteel and it slips out. Based on the testing I did, and eye to eye splice would be as strong as the line it was mad of. In other words, the line would break other than at the splice.
Allen
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).
[/ QUOTE ]
I have done some crude testing on Amsteel as part of an article on soft shackles. Basically I connected two soft shackles to a link of Amsteel that had eye splices on the ends. One eye was a tuck and stitch, one was a Brummel. The soft shackles were of different type. I pulled with a manual winch that had 100:1 advantage and was using 1/8 inch Amsteel, a scale model if you will. The Amsteel broke on the link center, away from the splices so my answer to what you are getting at is to use eye splices and tie things together with soft shackles. They are soft so your concern about them flying and hurting someone is less vs steel shackles. From everything I know and hear, splices are stronger than the line they are made of. I have heard the 90% number but I don't believe it. The only point where an eye splice could possibly be less strong than the line it is made of is at the point in the line where the bury ends if the taper is too abrupt. I wrote several web pages on all this including the testing and how to make soft shackles. You might find it interesting. http://l-36.com/soft_shackle_intro.php
I have also tested a bowline on Amsteel and it slips out. Based on the testing I did, and eye to eye splice would be as strong as the line it was mad of. In other words, the line would break other than at the splice.
Allen
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