Load Testing Results

[Seaworthy Lass]

PS Evans, are the strength of dyneema and knots in it temperature dependent? On deck in summer it may easily reach 40+ degrees C for long periods.

Knots that are completely buried like the Duncan may well heat up more internally and fail more rapidly as temp rises.

Just tossing around ideas.

[estarzinger]

Ok, the 'fishing knots" . . .

All these tests in 7/64" amsteel (single pulls, except the two knots which slipped where I did three just to confirm)

Two old reliable's as benchmarks:

Figure 8 = broke at 900lbs
Water Bowline = broke at 900lbs

EStar = broke at 960lbs (given the single pull that is on the edge of significant/not significant stronger than the above two)

Orvis = slipped at 790lbs
Uni = slipped at 973lbs (range from 860 - 1110lbs)
Trilene = broke at 1090lbs

I was surprised when the two slipped. I always thought of fishing line as the 'most slippery' but this amsteel with polished stainless pins appears to be even more slippery.

I am truly skeptical of anyone claiming knots 'holding near line strength' in amsteel. The only ' near knot like structure' that I have tested that clearly scores well beyond 50% in amsteel is the multiple (5x) brummel (without bury) - I tested it at 80%. But it is really more like a 3 strand splice than a true knot.

As to heat . . . here is some data from Samson (for their dyneema mooring lines). Looks like 50C and below is no problem at all (the breaking strength of HMPE fiber decrease by
8% at sustained 50 C).

[Seaworthy Lass]

Originally Posted by estarzinger

Ok, the 'fishing knots" . . .

All these tests in 7/64" amsteel (single pulls, except the two knots which slipped where I did three just to confirm)

Two old reliable's as benchmarks:

Figure 8 = broke at 900lbs
Water Bowline = broke at 900lbs

EStar = broke at 960lbs (given the single pull that is on the edge of significant/not significant stronger than the above two)

Orvis = slipped at 790lbs
Uni = slipped at 973lbs (range from 860 - 1110lbs)
Trilene = broke at 1090lbs

I am truly skeptical of anyone claiming knots 'holding near line strength' in amsteel. The only ' near knot like structure' that I have tested that clearly scores well beyond 50% in amsteel is the multiple (5x) brummel (without bury) - I tested it at 80%. But it is really more like a 3 strand splice than a true knot.

As to heat . . . here is some data from Samson (for their dyneema mooring lines). Looks like 50C and below is no problem at all.

Attachment 74088

Very interesting results. The Trilene and Duncan (=Uni) performed the best then, but not by much. Did you use the standard 5 turns in the Duncan (and rewind it to enclose the loose end before applying the load)? More or less turns may make a difference (see my post a couple back).

Did you have a chance to test the water bowline with a yosemite finish rather than the tuck you used? It would be great to know if this is the best option if a knot is needed that can be untied.

Thanks for the heat data.

I will give you some peace now as it has gone midnight here. You can see I am keen on knots .

[estarzinger]

^^

I did the uni with the standard 5 turns. And the water bowline I tested just above was the standard (unmodified) version.

This stuff is so easy to splice, I don't see many places for a knot. But right now, if I had to use a knot, I would use the Estar, because it is simple and does not use up miles of line (like the Trilene). If I needed a fixed loop that could be untied I think I would use the figure 8, again because it is so quick and easy. I would not expect to be able to untie it if it was ever loaded beyond about 500lbs. I guess I am saying it is possible to overstate/overvalue the importance of the single metric of breaking strength. This amsteel is so strong that 50% is usually way more than enough so other considerations come into play, like the ability for me to tie it in the dark when I am tired.

[estarzinger]

I am looking for some 4,500lb (that's the jackline reg minimum) 1" polyester webbing . . . anyone have a good source? None of my usual places seem to carry it. I can find nylon, but not polyester?

[estarzinger]

Just as an aside . . . while I was looking for webbing, I noticed this at Sailrite . . . it's in their instructions for DIY jacklines (using nylon tubular webbing). . . . . its with V92 thread and I have to say that given my testing to date I would guess that pattern would probably not hold 4500lbs.

sailrite.jpg Views: 127 Size: 178.7 KB ID: 74093" style="margin: 2px" />

[thinwater]

Originally Posted by estarzinger

I am looking for some 4,500lb (that's the jackline reg minimum) 1" polyester webbing . . . anyone have a good source? None of my usual places seem to carry it. I can find nylon, but not polyester?

I bought a different product from these guys once (industrial). Excelent quality. See P022.
Polyester Webbing

Also these folks. They sell by the foot. Never used them, but I would start there.
1" Polyester Webbing | 1 Inch Polyester Webbing | 1 In Poly Webbing

[thinwater]

Originally Posted by estarzinger

Just as an aside . . . while I was looking for webbing, I noticed this at Sailrite . . . it's in their instructions for DIY jacklines (using nylon tubular webbing). . . . . its with V92 thread and I have to say that given my testing to date I would guess that pattern would probably not hold 4500lbs.

Hmmm.

The tether instructions and video are with 2" webbing. Maybe, as the stretch is 1/2 and the width is double. He does about 12 stitiches each pass, and goes over it ~ 4 times. With 50 stitiches at the tail, 50 stitiches at the throat, a relativly short join and about 30 pounds (gotta be conservative with DIY)... fail at 3000 pounds. If you do a few more passes it could pass.

The jackline instructions don't have a video. But given what we saw with the 2 inch webbing, even with the same stitch count, fail at 2000 pounds at best. However, given the long join and the stretch differencial (only the tail stitches will bear much load) I think more like 1200 pounds. There are only about 25 stiches carrying the load. Do a drop test and the mass wouldn't even slow down.

Make one like that, pull it, and send Sailrite the results. That would be a real public service, as more folks than just Sailrite customers read those instructions. And if not a climber (knowing what strong gear looks like) and before looking into the subject, I would have believed them.

This is frightening. At the very least the instructions need to explain the importance of stitch count. What I see--just a picture--is useless.

[estarzinger]

^^ Thanks.

Just to check my instincts . . . I replicated that sailrite pattern (using nylon webbing and V92 thread, as they did). It broke at 1100lbs. I did it in polyester webbing, and it broke at 1230lbs, not sure if that is a significant difference, but does tend to support our theory that the stretch riser in nylon makes the longer patterns less effective.

Originally Posted by thinwater

Hmmm.

I think more like 1200 pounds. There are only about 25 stiches carrying the load.

Great Guess!!

on polyester webbing . . . i found these guys . . . http://www.countrybrookdesign.com/we...ed-1-inch.html . . . .I think this is the webbing that Wichard is using on their pre-made jacklines. There is not a tensile listed, but I think its 5300lbs (based on some of their other webbing). I have e-mailed to ask.

[estarzinger]

mmmm . . . here is West Marine's pre-made jackline. It is polyester, but there is almost no stitching at all at the stress riser' point. It's probably not going to hold anywhere near 4,500lbs either.

[thinwater]

Originally Posted by estarzinger

^^ Thanks.

Just to check my instincts . . . I replicated that sailrite pattern (using nylon webbing and V92 thread, as they did). It broke at 1100lbs. I did it in polyester webbing, and it broke at 1230lbs, not sure if that is a significant difference, but does tend to support our theory that the stretch riser in nylon makes the longer patterns less effective.


Great Guess!!

on polyester webbing . . . i found these guys . . . Webbing Polyester Reflective Red 1 Inch . . . .I think this is the webbing that Wichard is using on their pre-made jacklines. There is not a tensile listed, but I think its 5300lbs (based on some of their other webbing). I have e-mailed to ask.

How scary is 1200 pounds breaking?

First, let's assume that was a 1-time, day one value. Let's use 800 pounds as more realistic, after some use and sun. Also, ESTAR is not the worst seamstress.

Break out Pythagoras. If we assume that polyester webbing stretches 3% at 20% load, then an 800-pound load causes 3% stretch. If we build the triangle, this will mean a 2.6' deflection at the mid-point of a 20-foot jackline. Consequently, only 2*(800*2.6/10)=416 pounds of latteral force are required to snap the jackline.

How much of a slip? The jackline will absorb about (assume ideal spring--it will be less than this) 2.6*0.5*416=540 ft-pounds. That is equivalent to a 2.5-foot fall for an average guy, or a 8 knot stumble, not including your mass moving down hill or the wave chasing you. Better not have any slack in the tether. This is cutting it very thin, but most likely they have not had any failures.

[estarzinger]

Spinlock appears to be using bar tacks, that look to be up to mountain climbing standards.



Wichard appears to be using 'down zigzag' that looks to me like it will peel from the stretch riser at the 1 ply/2 ply interface. But I can't find a picture of the full stitching pattern. They may have some bar tacks near the end that I can not see.

[thinwater]

What is really disturbing about bad stitiching, is they could have reached a certain, no question mark 75% (3000 pounds, or nearly 3x as strong) with an overhand loop! I've probably taken over 1,000 falls on overhand loops in 1" webbing; very common for top-rope anchors.

The DIYs that simply tie jacklines are not so dumb. While they are technically below the limit, they would catch any realistic fall, and after some wear, allowing for poor manufacture, and figuring that knots handle UV better than thread, they may be ahead of most chandlery gear.

[estarzinger]

I just tested the West stitching pattern, and it failed exactly as ThinWater suggested - not enough strength at the peel point. That is assuming we can really see the stitching and there really are no bar tacks at the end. So, using v92 thread, I just replicated west's stitching and tested it against a much more compact '5 bar tack' pattern (making bar tacks using my zig zag set to smallest stitch length). The west stitching peeled away progressively from the 1ply/2ply join at 2140lbs. The 5 bar tack pattern still held and had not broken even the first bar tack.

[JPA Cate]

Originally Posted by thinwater

What is really disturbing about bad stitiching, is they could have reached a certain, no question mark 75% (3000 pounds, or nearly 3x as strong) with an overhand loop! I've probably taken over 1,000 falls on overhand loops in 1" webbing; very common for top-rope anchors.

The DIYs that simply tie jacklines are not so dumb. While they are technically below the limit, they would catch any realistic fall, and after some wear, allowing for poor manufacture, and figuring that knots handle UV better than thread, they may be ahead of most chandlery gear.

Tom,

Thank you very much for your input into this thread. The combination of your and Evans' thoughts, and experience, is extremely enriching for the rest of us. It's wonderful.

Ann