Why knots are not recommended in Amsteel or similar lines

[swoody126]

I had some extra amsteel left over from some loops I made and just quickly tied the ends together to test some new straps. I managed to sit in the hammock for about 10 minutes until it came undone and the weak point was where the knot was in the amsteel. One bruised elbow & ego later, I was getting up off the ground and making a mental note to not do that again!

for those of us who used to water ski, we remember the slipricity of the ole SKI ROPE

whenever we would break an original unit, we would always try to just tie it back together, to finish out the day

and the knot almost always failed

butt(pun intended, since that's what we are landing on) the water is way softer than falling to the ground, in the middle of the night

some of us went to the hardware store & bought the hollow fid & spliced a new eye on them, which is similar to what we are doing w/ the AMSTEEL and it worked

Hmmmmmmmm???

yeahbut - look at the requirements for climbing. Strength is not listed as they just use big enough ropes. Hammockers looking for ultralight are also pushing for minimum rope sizes.

according to the information in the OP, as long as we stick to the proven sound method of splicing the 7/64" AMSTEEL, there shouldn't be any worries

i, personally, am willing to risk my 260# butt on the 95% rating of the splice

AND... I WILL REMEMBER to avoid the temptation to tie a knot in the slippery stuff

MANY THANKS FOR THE LINK

sw

[Detail Man]

Amsteel is slippery by nature and doesn't hold knots well. Climbing ropes are designed to hold a knot. Ropes are rated at the number of recommended falls and a kilonewton rating. Most dynamic climbing ropes (9-10mm) are rated around 9 kN (about 2000lbs). Static rescue ropes (11-13mm) are rated around 29 kN (about 6500 lbs). Even still knots derate the ropes significantly.

[Mouseskowitz]

In the paper there are two tables of knot strengths. Table 3 is of knots in traditional rope, Table 4 is many of the same knots in Amsteel. There are two differences that make knots worse in Amsteel.

First is the slipperiness as several have already mentioned. If you really want to you can put a cover on the Amsteel or buy rope with a Dyneema core to make that a non-issue. The real problem lies in the fiber type. Dyneema ropes are made from Ultra High Molecular Weight Polyethylene (UHMW-PE). The nature of this fiber makes it so you need a 8:1 bend radius to maintain the full strength of the rope. So, a 1/8" line would need a radius of 1". A traditional kernmatle rope only needs a 3:1 radius. The radius requirement is where most of the performance difference in the charts comes from. And as Rain Man has already pointed out, you can also run into this problem with hardware.

I'm going off of memory for the radius numbers, so if I'm wrong please correct me. I hope this clarifies some of the rope's properties.

[Bubba]

Thanks for the info. That's really useful to have quantifiable results and not just heresay.

[michaeldoe62]

I just recently started using amsteel. Glad I read this. Thank you!

[Mouseskowitz]

I'm glad this helps clear stuff up.

[SilvrSurfr]

I'm glad this helps clear stuff up.

I'm sure it won't stop people from using knots with Amsteel, but it gives me peace of mind and confirms what I already thought.

[keg]

...
But don't forget, hardware can weaken ropes just as much or more. A really sharp bend over an edge or hardware with a small diameter can be worse than a bad knot. Even dynamic forces can permanently weaken a rope.....

True. I had 1.75 zing it ridge line on my tarp fail in the middle of the night where the dutch hook was.

[Firetruck]

This is the first time i've seen this post. What's ironic is I was looking up how to determine loads on a rope with the forces placed on it in a hammock just this morning. http://www.youtube.com/watch?v=EZNSoSIurQ8

My hammocks have 7/64 amsteel whoopie slings. I'm over 300# and have concerns as to how long this stuff will hold me. Thought about going to 1/8.

BTW the formula didn't help a bit. I done gragiated from the 6th grade ya no.

[Rob In AL]

Firetruck, the last time I was on a scale (about 3 weeks ago) I was #319. I use the 1/8th Amsteel Blue and tie off with a quick release half-hitch (after winding up the excess between 2 carabiners - like a block & tackle) and have had no problem with slipping nor have I seen any sign of the material being overstressed.

Just my $0.02

Rob

<edit> I found some 1" webbing that I *think* is poly, not nylon. Regardless, it doesn't stretch much if at all. I bought enough to make combination tree straps and suspension lines. That hammock has an Amsteel ridgeline held on with bowlines. Failure there being more nuisance than hazard