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estarzinger

Rope/knot/splice load testing

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Allen, I consider the normal brummel to be 1, and the 5 brummel to that repeated 5 times, so it would be 10 pass thru's (5 each way). I don't know if there is any "official definition", but I believe that is also how Brian defines it. The 5 brummel (defined that way) was 80% strength.

I think this is right. I see Brion quoted on page 3 of this thread talking about a soft shackle as having a half brummel. 10 pass throughts takes up quite a bit of space so the single brummel and a short bury becomes more interesting. I look forward to hearing the results when you get back to your test jig.

 

Allen

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^^ I tested a single brummel with a 9x bury (no taper). It failed with relatively little force. The failure mode seemed to be that the bury slipped and the locking action of the brummel unbraided the short section of bury so what I ended up with was a line with a fork in it with half the strands on each side of the fork. I would assume that this means the strength of a single brummel is dependent on the amount of line left over in the tail. Perhaps lock stitching would have helped.

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Tested one (EZ Splice) this morning on 1/2-inch DB. 2640 pounds as a straight splice. Needless to say, the rope looked fine.

 

Could the method work? Possibly, it is not that different in some ways from a sewn splice. Build it from metal and screw the pins in. But I'm betting the rope damage would cause early failure, and nylon would be a joke (not enough points per inch).

 

I've seen constructions like this on commercial products. Like heat-shrink, folks think it looks "production" and like that. They think a knot looks cheap. And I'm sure if you tied your 20' pontoon box on the lake with 5/8" DB and used these it would hold. So would clothes line. But perhaps that last comment was prejudicial.

 

Breaking strength of Home Depot/Lowes nylon rope? I've not been able to find BS on-line, only ridiculously low working loads (~ 500 pounds for 1/2-inch), suggesting BS of 2500-5000 pounds. If that is the case, then the splicer will cause the rope to break before the pins pull.

 

http://www.ropekingusa.com/products.asp

That strength sounds about right, I've always assumed that they quote safe working loads around the 1/6 to 1/10 the breaking load...

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Thinwater, in your lifeline chafe testing . . . you might consider running a stainless wire back and forth a bunch in a test stanchion hole - both to 'roughen up' the hole, and also set a wire chafe benchmark. Wire does break strands at the lifeline exit holes after some flex fatigue.

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^^ Yes, I thought about that. I'm going to do some runs both with and without that torture prep. You know how it is, one variable at a time. But since that seems to be responsible for failure, that is something that will be tested. In fact, the little bit of testing I did this afternoon pointed to the obvious; rope doesn't abrade much on polished SS. Thus, the importance of prepping the holes before switching to fiber cannot be understated. We know this to be true about wire-to-fiber halyard conversions. I know it from my own mis-expereince with a Kevlar halyard over 20 years ago!

 

But I'm going to test the holes smooth before I mess them up!

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I think it was mentioned a while back, but did you ever test a core-core splice on a polyester double braid? Or a core/cover splice on a dyneema core line?

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@Estar. I have tested the short splice after the brummel and it just rips apart. I don't think a short splice is going to hold so I started thinking of other ways to get a stronger halyard setup without a splice. What I thought of was based on a stopper knot that for the life of me I can't remember the name and cannot find it in Ashley. It is a little like half a quad fisherman's knot. There is a Youtube video of it but they just call it the stopper knot. I initially saw it on another youtube video which I think was about the Volvo Ocean Race but I can't find that video either.

 

I tested it against the Estar knot and the Estar knot broke. I would be interested in seeing this tested with your setup. Looks a little like a hangman's knot as well. Describing how to tie it, take the line and go through the ring (in this case a soft shackle) and back along the standing part. Then make four loops around both strands back toward the ring. Then pass the end back up through the center of the loops and dress the knot. I think it is important to get the loops tight before the pull so that the soft shackle is not sucked into the knot. I also would suggest the variation in the second picture that might be less likely to slip and also gets the tail out of the way as I would cut it after the small stopper and fuse it.

 

The idea is that although a fisherman's knot slips, in this arrangement it is only taking 1/2 the load. It's construction does not subject the line to a tight initial bend so should be stronger than other knots. I have mixed feelings on the variation. It might cause problems so I would test the first picture first and go to the second if it slips. My testing was with Lash-It which does not always transfer to thicker line.

 

Allen

 

halyard_knot.jpg

 

halyard_knot_variation.jpg

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I tested a range of thimble designs. The loads quoted are all when a wall of the thimble started to distort sideways. They have already collapsed and elongated to some degree by this point.


There were two surprises. First is how poor the conventional open galvanized thimble (as used on many anchor rodes) is. Both the 5/16" and 1/2" sizes distorted at only 57% of the tensile of the appropriate size nylon 3 strand line. Second is how relatively good the closed nylon thimbles were (compared to the galvanized). They distorted at slightly higher load, and bounced back to near their original shape when the load was taken off. The open stainless thimble distorted at essentially 100% of the line tensile, so is "good enough". The clear winner is the closed stainless thimble (aka a sailmakers thimble). It was the only one which exceeded the nylon tensile strength - giving a safety margin for nylon and allowing for use with higher strength lines.


The pic is of the thimbles after the test


post-8534-0-07190900-1394809793_thumb.jpg

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What I thought of was based on a stopper knot that for the life of me I can't remember the name and cannot find it in Ashley. It is a little like half a quad fisherman's knot. There is a Youtube video of it but they just call it the stopper knot. I initially saw it on another youtube video which I think was about the Volvo Ocean Race but I can't find that video either.

 

I just tested that in 1/8" amsteel - slipped at relatively low load - 1000lbs (40%) - it then internally heated up and broke.

 

post-8534-0-80300200-1394811493_thumb.jpg

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What I thought of was based on a stopper knot that for the life of me I can't remember the name and cannot find it in Ashley. It is a little like half a quad fisherman's knot. There is a Youtube video of it but they just call it the stopper knot. I initially saw it on another youtube video which I think was about the Volvo Ocean Race but I can't find that video either.

 

I just tested that in 1/8" amsteel - slipped at relatively low load - 1000lbs (40%) - it then internally heated up and broke.

 

post-8534-0-80300200-1394811493_thumb.jpg

 

comparing your and my results over time . . . it may be that lash-it is below the linear scaling effect. We know that dyneema fishing line is - that is its behavior with knots is different than 'sailing size' amsteel. And it may be that lash-it is somewhere just below the linear boundary.

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I think it was mentioned a while back, but did you ever test a core-core splice on a polyester double braid? Or a core/cover splice on a dyneema core line?

I have a bench length limitation that makes it hard to test double braid splices - its possible to do, but I worry that the results will be distorted.

 

I have looked at 'core to core' polyester splices with no cover bury at all - which test about 67% of line tensile - roughly similar to a knot.

 

The core/cover dyneema splice would depend on the polyester cover as a clamp and would (I think) be limited by the tear strength of the polyester. The knot testing suggests that would be max 50% of line tensile - so again similar to a good knot.

 

So, without actually doing the testing directly, I would say we have directional information to suggest both splicing ideas would be about similar to a good knot. But I have certainly been surprised before here and that could be wrong.

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What I thought of was based on a stopper knot that for the life of me I can't remember the name and cannot find it in Ashley. It is a little like half a quad fisherman's knot. There is a Youtube video of it but they just call it the stopper knot. I initially saw it on another youtube video which I think was about the Volvo Ocean Race but I can't find that video either.

 

I just tested that in 1/8" amsteel - slipped at relatively low load - 1000lbs (40%) - it then internally heated up and broke.

 

 

Let me make sure I understand. It slipped but the failure was not that it slipped out but rather that it broke. Therefore the second version would not help. Did it break at about the same load it slipped at? That means the Estar knot is still the best short of a splice, which is too long. I can't recall if the Estar knot or that other one which cannot be tied to a padeye is stronger. I could use either around the soft shackle.

 

Regarding Lash-It. I have certainly noticed that our results have been different. I guess I will have to go back to using Amsteel. It is just so hard to break with my winch and honestly a little scary.

 

When I did my test, I did see a small amount of slip but then it stopped slipping and the Estar knot on the other end broke.

 

Allen

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What I thought of was based on a stopper knot that for the life of me I can't remember the name and cannot find it in Ashley. It is a little like half a quad fisherman's knot. There is a Youtube video of it but they just call it the stopper knot. I initially saw it on another youtube video which I think was about the Volvo Ocean Race but I can't find that video either.

 

I just tested that in 1/8" amsteel - slipped at relatively low load - 1000lbs (40%) - it then internally heated up and broke.

 

 

 

Let me make sure I understand. It slipped but the failure was not that it slipped out but rather that it broke. Therefore the second version would not help. Did it break at about the same load it slipped at? That means the Estar knot is still the best short of a splice, which is too long. I can't recall if the Estar knot or that other one which cannot be tied to a padeye is stronger. I could use either around the soft shackle.

 

Regarding Lash-It. I have certainly noticed that our results have been different. I guess I will have to go back to using Amsteel. It is just so hard to break with my winch and honestly a little scary.

 

When I did my test, I did see a small amount of slip but then it stopped slipping and the Estar knot on the other end broke.

 

Allen

Yes, I had a relatively long tail on it (you can see in the photo). I kept pulling it while it slipped and it broke before the tail slipped all the way thru. It was pretty warm - I may have pulled it on the fast side. I think it would have slipped the whole way and not have broken if I had pulled slower. It did break at the same as the slipping load (remember that slipping loads are somewhat variable with pulling speed).

 

The palomar tested a little (3-5% of tensile) stronger than the Estar - it was not statistically significant, but I suspect it was real (eg that it is in fact a bit stronger).

 

I am not sure if the coatings on amsteel and lash-it are the same - I suspect the coating has an influence on slipping vs holding/breaking.

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Yes, I had a relatively long tail on it (you can see in the photo). I kept pulling it while it slipped and it broke before the tail slipped all the way thru. It was pretty warm - I may have pulled it on the fast side. I think it would have slipped the whole way and not have broken if I had pulled slower. It did break at the same as the slipping load (remember that slipping loads are somewhat variable with pulling speed).

Then maybe the variation would help as it should stop the slipping. I have not tried it though and my setup is down right now.

 

Allen

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I think it was mentioned a while back, but did you ever test a core-core splice on a polyester double braid? Or a core/cover splice on a dyneema core line?

I have a bench length limitation that makes it hard to test double braid splices - its possible to do, but I worry that the results will be distorted.

 

I have looked at 'core to core' polyester splices with no cover bury at all - which test about 67% of line tensile - roughly similar to a knot.

 

The core/cover dyneema splice would depend on the polyester cover as a clamp and would (I think) be limited by the tear strength of the polyester. The knot testing suggests that would be max 50% of line tensile - so again similar to a good knot.

 

So, without actually doing the testing directly, I would say we have directional information to suggest both splicing ideas would be about similar to a good knot. But I have certainly been surprised before here and that could be wrong.

 

Mostly I'm curious about the polyester double braids because some of them say to use a core-core splice for optimum strength. This seems really odd to me and I can't figure out how that would be superior to adding the cover strength to the splice.

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Mostly I'm curious about the polyester double braids because some of them say to use a core-core splice for optimum strength. This seems really odd to me and I can't figure out how that would be superior to adding the cover strength to the splice.

Which ones? Never heard of that except for core dependent line.

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A thimble alternative I have used on many occasions--no failures, but that doesn't mean they were at full load--is to use either tubular nylon webbing or Dyneema sleeve over the line in the eye. I'm particularly apt to do this if the shackle has a rough profile. I've done this on anchor rodes, topping lifts (did one today) and halyards. One advantage, of course, is that it can be used without fear of falling out, for example if a knot is used, but a splice that stretches (nylon) presents a similar challenge. It does a good job of absorbing wear and does lengthen the radius just a bit, perhaps enough to maintain greater than 50% strength. Let clunky, lighter, and not prone to scratching anything. Perhaps a good middle-of-the-road answer.

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^^

 

It depends a bit on the application, but for splicing to chain (directly spliced to the last link) I have never seen any chafe. I used to cut my splice open each year, inspect it and redo it, but I never saw any sign at all of chafe so I now pretty much just leave it alone.

 

My feeling is that the thimbles are important for bend radius purposes with double braid line, but for line which you unlay in the splice (like 3 strand or 8 brait) it is not important (if the strands are less than or equal to the chain diameter, which they usually are).

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Re. Chain, that was climbing rope on avery light boat (Stiletto 27). Ordinarily I would splice and there is no chafe, only link corrosion.

 

There are other apps. Headboards (can't fit thimble if sharp). Direct tie to drilled holes. Bridles. Anytime a thimble might be suggested...'but not quite.

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Then maybe the variation would help as it should stop the slipping. I have not tried it though and my setup is down right now.

Allen

I will give the variation a try (have some time tomorrow). But I think it will still slip.

 

I am not sure why you are looking for a new knot? We have the polamar, estar, water bowline, and figure 8 which don't slip. And the first two bump up quite close to the 50% "dyneema knot limit". If you want to go stronger than that, we have the multiple brummel. And if you want to go stronger we have the bury splice. That would seem to provide a solution set to your application, depending on what trade-offs you want to make.

 

As we know well from the bends, simply finding a no-slip knot is hard, and looking for one that is better than 5o% is (IMHO) fruitless.

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Mostly I'm curious about the polyester double braids because some of them say to use a core-core splice for optimum strength. This seems really odd to me and I can't figure out how that would be superior to adding the cover strength to the splice.

Which ones? Never heard of that except for core dependent line.

 

Sirius 500 from Robline. 32 plait cover, 8 plait core, polyester core/cover.

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Sirius 500 from Robline. 32 plait cover, 8 plait core, polyester core/cover.

Interesting . . . Do you have a link to splicing instructions for that? I would have thought the normal core to core splice would not work with an 8 plait core - does the 8 plait have a hollow center (it does with some 8 braids and not with others)?

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Then maybe the variation would help as it should stop the slipping. I have not tried it though and my setup is down right now.

Allen

I will give the variation a try (have some time tomorrow). But I think it will still slip.

 

I am not sure why you are looking for a new knot? We have the polamar, estar, water bowline, and figure 8 which don't slip. And the first two bump up quite close to the 50% "dyneema knot limit". If you want to go stronger than that, we have the multiple brummel. And if you want to go stronger we have the bury splice. That would seem to provide a solution set to your application, depending on what trade-offs you want to make.

 

As we know well from the bends, simply finding a no-slip knot is hard, and looking for one that is better than 5o% is (IMHO) fruitless.

 

I guess I think the 50% limit is only a limit because we have not found something stronger. It just seems to me that if we can constrict the standing part without asking it to make any bends, and not have a large load on any part that does have a bend, that we can exceed that limit. Perhaps I am missing something. I don't have any ideas past this so it is not an endless quest.

 

Allen

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I guess I think the 50% limit is only a limit because we have not found something stronger. It just seems to me that if we can constrict the standing part without asking it to make any bends, and not have a large load on any part that does have a bend, that we can exceed that limit. Perhaps I am missing something. I don't have any ideas past this so it is not an endless quest.

 

Allen

I would suggest the 50% limit is a physics based limit. Samson says (with dyneema) the bend radius curve applies to any bend radius more than around 10 or 20 degree deflection. I would think it hard to make a knot with all bends less than 20 degree deflection (this is what the brummel multiple tuck splice and the bury splice accomplish), and we know the radius on these deflections will be 1:1, so the curve says about 50% will be the limit.

 

Even putting aside the 20 degree deflection limit . . . Trying to bury the sharper bends inside the knot, to reduce the loads on the sharper bends, is also problematic given the slipperiness.

 

So, I think this (50-55%) is a real knot limit and not just a failure of imagination. Looking for strong knots is ages old, and we have tested the best prior art with none breaking the limit. The slipping issue is newer and not as well studied, so there is probably new ground to be found in no-slip knots (like the estar) but I personally just don't see how they will be stronger.

 

If you want to look for stronger, I think you need to look at tuck splices. There are all sorts of more sophisticated tucks than the brummel, and I am sure you could develop one that is short and near 100%. It would just be more work to make.

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I guess I think the 50% limit is only a limit because we have not found something stronger. It just seems to me that if we can constrict the standing part without asking it to make any bends, and not have a large load on any part that does have a bend, that we can exceed that limit. Perhaps I am missing something. I don't have any ideas past this so it is not an endless quest.

 

Allen

I would suggest the 50% limit is a physics based limit. Samson says (with dyneema) the bend radius curve applies to any bend radius more than around 10 or 20 degree deflection. I would think it hard to make a knot with all bends less than 20 degree deflection (this is what the brummel multiple tuck splice and the bury splice accomplish), and we know the radius on these deflections will be 1:1, so the curve says about 50% will be the limit.

 

Even putting aside the 20 degree deflection limit . . . Trying to bury the sharper bends inside the knot, to reduce the loads on the sharper bends, is also problematic given the slipperiness.

 

So, I think this (50-55%) is a real knot limit and not just a failure of imagination. Looking for strong knots is ages old, and we have tested the best prior art with none breaking the limit. The slipping issue is newer and not as well studied, so there is probably new ground to be found in no-slip knots (like the estar) but I personally just don't see how they will be stronger.

 

If you want to look for stronger, I think you need to look at tuck splices. There are all sorts of more sophisticated tucks than the brummel, and I am sure you could develop one that is short and near 100%. It would just be more work to make.

My hope was that all the bends would be on a part of the knot taking 50% of the load and that there would be no bends on the part taking 100% of the load. In terms of slipping, I would think that the load on the tail that I am suggesting get tucked would be fairly light and there should be some stopper knot that would prevent if from passing through the tight loop. Feel free to put your favorite non slipping stopper knot on the tail. Perhaps a single half hitch is not enough. It might also help to try and lock up the knot like you do on the soft shackles before doing the final test. I could see loading up the halyard with its winch after tying the knot but probably not more than that.

 

But your point about tucked splices is good. I will look at that. Looking at the Samson web site, I only see tuck bury splices that take up 36 diameters -- a little long. I will keep looking.

 

Allen

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You might also look at some amount of sewing. Sewing down the tails seemed the best way to 'fix' the double fisherman' from slipping, but it still did not break the 50% strength limit.

 

For tucks, take a look at the splices for 8 and 12 strand anchor brait. They are tucks and well short of 36 diameters long. I would have guessed about 10 diameters. The 8 strand one usually tucks two strands together, so there are 4 tucked 'pairs'

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Sirius 500 from Robline. 32 plait cover, 8 plait core, polyester core/cover.

Interesting . . . Do you have a link to splicing instructions for that? I would have thought the normal core to core splice would not work with an 8 plait core - does the 8 plait have a hollow center (it does with some 8 braids and not with others)?

 

The core is hollow if I understand your meaning correctly. You can scrunch it up and run a fid down the middle easily.

 

I don't have a link, I searched all morning and can't find where I read about the core-core splice for it. I swear it was in one of Robline's catalogs, I'll look some more. A few places that carry Sirius also have that recommendation in the product description. I was thinking about sending you some splices in the Sirius to test for me, I'd really like to do a cover/core splice if I'm not losing too much strength. I have it in both 8mm and 6mm.

 

I'll keep digging!

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Maybe it's just something that got lost in translation lol. Looking at Robline's splicing instructions, there is no way I would do their high-tech splice on Sirius...

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[snip]

If you want to look for stronger, I think you need to look at tuck splices. There are all sorts of more sophisticated tucks than the brummel, and I am sure you could develop one that is short and near 100%. It would just be more work to make.

On that subject Hampidjan suggests that this splice: http://www.hampidjan.com/media/pdf/Dynex_Tuck_splice_with_head.pdf is:

 

...absolutely the best splice for Dynex ropes as it will never slip and it gives the highest retaining strength possible to

achieve with splice.

 

It would be interesting to see that tested.

 

They also offer a "quick and dirty" splice without comment on its strength: http://www.hampidjan.com/media/pdf/Dynex_Shoemakerssplice_wih_head.pdf

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can scrunch it up and run a fid down the middle easily.

I was thinking about sending you some splices in the Sirius to test for me, I'd really like to do a cover/core splice if I'm not losing too much strength. I have it in both 8mm and 6mm.

 

I would be happy to pull your splices. It is an interesting line construction and I would be curious to see how it performed.

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Allen, so here is an improvement for you. A hybrid knot/tuck

 

I tied your noose knot, tightened it up to slip load on the soft shackle, and then locked the tail with a single Brummel. It is still pretty short. Did not slip. Broke at 70% (1770lbs). Broke at the loop (which is the first loaded deflection).

 

This sort of hybrid is probably also a solution to your search for a bend (although the brummel may be more difficult to do in a bend application, but if so, you could use another sort of tuck)

 

post-8534-0-37073300-1394914074_thumb.jpg

 

post-8534-0-56292000-1394914085_thumb.jpg

 

I first tried just sewing down the tail, but my sewing broke.

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Regarding tucks, I think the first thing I would try would be to seperate the 12 strands into 4 groups (of three). Take two of the groups thru the same hole, in opposite directions, of the standing line, and one pik below that the other two groups thru a hole at 90 degrees to the first. Repeat four times. That would not be too hard or too long.

 

The first tuck that p32 linked to above would be certainly 100% strength, but very very fussy to do in the small size line we are dealing with here.

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Thinwater, in your lifeline chafe testing . . . you might consider running a stainless wire back and forth a bunch in a test stanchion hole - both to 'roughen up' the hole, and also set a wire chafe benchmark. Wire does break strands at the lifeline exit holes after some flex fatigue.

 

Got started today (haven't run the wire yet):

  • Heat shrink lasted seconds. A total waste of time.
  • Other tubing (clear vinyl and airline) were better, but still failed in minutes.
  • Either nylon or spectra set-up to float last for hours (7 cycles per second, remember--this would rupture a PDB rope in 10 minutes) with visible change. I need to try them fixed to the line, but that may not be practical; the fit may be too tight. Spectra non-floating is running now.
  • Spectra is hard-wearing, but it's hard to fuse the ends after cutting, compared to nylon. This is essential if it rigged floating.
  • For retrofit, a double wrap of Sunbrella is darn hard wearing and would be easy to replace.
  • I'll be testing Maxijacket and RP25 in a ew days. Gotta give 48 hours for fair drying.

How would you inspect under the chafing gear? just slide the line to one side a few inches. But honestly, after what I saw dragging the line back-and-forth through a rough drilled whole for 850 cycles, I'm not too worried about it. In fact, I put the nylon and spectra against a grindstone (floating) for an hour with similar results; zero wear inside or out.

 

In a few days, perhaps tomorrow, I will drag SS cable though there ~1000 cycles, see what the cable and hole looks like, and then use that hole as a test bed.

 

Any other testing ideas related to lifeline chafe? I'm planning to get samples of every rope I can think of an work my way through that, but thatis a separate project.

 

Fun stuff.

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^^ leather?

 

Strength test before and after chafe? To know when it is really time to change a line out, and to know if the wr2 cover makes up for its lower strength.

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^^

With effect chafe protection there was zero wear in each case, so except for some flex fatigue, there was no wear at all.

 

Leather? Anything thin enough to fit the gap wouldn't be very hard wearing or long hold up to rain and sun. We're talking about 2 layers of Sunbrella as an upper limit if 1/4 line is used in a 10mm hole., I don't know what could be identified as a uniformly available material.

 

I'll have to get some WR2. But personally, I'd favor 6mm single braid over 5mm with a cover I can't count, and spot protection where needed. I do know that while the Amsteel is quite abrasion resistant, it did get enough damage in 20 minutes on a semi-smooth hole to convince me that a cover could fail. I think long term it is probably the best value, balancing cost and lifespan. But I'm a cruiser.

 

Have you ever played with NE Rope's dyneema chafe sleeve? It is in fact tubular webbing with a much denser weave than any rope cover I have ever seen. The stuff is tough, wearing much better than Amsteel; I need more replicates.

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^^ figure 9 in this paper (http://www.bethandevans.com/pdf/abrasion_and_fiber_fatigue_in_high_performance_synthetic_ropes_for_ship_escort_and_berthing.pdf) is interesting related to your work. It shows a significant difference in abrasion result depending on braid angle.

 

No, I have never used the dyneema chafe sleeve. The only place I use a chafe sleeve is were my dyneema check stays bang on the aft spreader edge when they are not in use. I just added 6" of polyester cover there, which has done the job perfectly.

 

Re leather - yes, I forgot you were dealing with such a small gap. I was thinking that if the leather was "water formed" in place on the stanchion it would act as a bushing, covering cutting edges.

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Allen,

 

Here is your noose, with an estar stopper knot (the only non-slip stopper we found).

 

One sample, broke at 55%, broke at the loop. So, excellent for a knot, but not as good as the hybred I showed a couple posts up. Can't tell for sure with just one pull, but I would guess this one is a bit stronger than the estar.

 

It did not slip much, and I am not even sure the stopper was necessary. It may be a "non-slipper" with just the tail taken thru the loop and no stopper knot. But the stopper might be more necessary if it was tied to a shackle rather than another piece of amsteel. We would need some testing to determine all the slip characteristics.

 

post-8534-0-56385000-1394977864_thumb.jpg

 

post-8534-0-96810000-1394977882_thumb.jpg

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^^ Thanks for doing this test. That is one fancy stopper knot!

 

That is very encouraging as breaking at the loop is probably as strong as this can get with a knot that tightens up the loop. I assume that the hybrid prevented the loop from fully constricting and that is what accounts for its added strength? If it were just turning radius I would expect these two versions to be the same. That is a very clever hybrid, a really sweet idea.

 

I am assuming that on the hybrid that you would need access to both ends of the line? I can't figure out how to do it with one end. Unfortunately I don't have access to the other end of my halyard as it has 3/8 Tenex over it spliced into the Amsteel half way and removing it and re-doing the splice takes is a real chore. It could be done but is a real pain.

 

I wonder if, instead of tucking the tail through the eye, what if we buried it in the line. That would bulk up the eye and the bury should not slip as it would be inside the nose after you tighten up the loop. The burn would be using the length inside the noose so would not add length to the knot. The only reason to do this would be if it added strength. There might be an issue with how things tighten up though. I guess one could also just burn a section of line inside the part that was going to be the knot and just make that part of the line stronger. It would make the knot bigger by 40% I assume. The only issue I see with these approaches is that the relative turning radius would be worse with a given size soft shackle. To address that, one could put a cover over the soft shackle to make a larger turning radius for the loop. Doing just the added cover over the soft shackle might be an easy improvement just by itself if it is a turning radius issue.

 

On the question of a stronger bend. Perhaps a quad fishermans knot with the tails tucked between the two nooses would be stronger as there would be no turning radius and the tails would be held by the tightening of the two nooses toward each other. Could always add the stopper knots and really prevent the tail from slipping.

 

 

Allen

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I wonder if, instead of tucking the tail through the eye, what if we buried it in the line.

Just tried that . . . works very well.

 

broke at 76%, at the end of the bury - which I had just snipped off at an angle - a better taper would be stronger, but also longer.

 

I ended up with 5cm of bury beyond the knot, after it was all tightened up to breaking load. Not sure if that is too long for you. It could be shorter, but I am not sure how much.

 

post-8534-0-18055400-1394990247_thumb.jpg

 

post-8534-0-86420800-1394990261_thumb.jpg

 

I did use both ends to make the brummel on the prior hybrid, but I suspect it would not be hard to come up with an easy 'one-end tuck' that would work as well.

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Looks like the splice kept the loop from tightening. That probably helped. If I did the math right, the bury is short so might just be holding because of the knot. I wonder about starting the taper right after the knot. But no matter what, this is encouraging.

 

Allen

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Wire Cable. I did as suggested and ran a standard un-coated lifeline cable for 1 hour.

  • The damage to the cable was greater than with Amsteel! Within 10 minutes there was significant wear on the wires, and by the end of the test there were dozens of broken wires, more due to wear than fatigue, but some of both.
  • The wire ate a groove about 1/2 wire diameter into the tubing.
  • The is certainly a bit of a burr on the tubing now, about equivalent to a freshly drilled and un-finished hole, and the wear on the Amsteel is about what I saw on an un-finished hole, which is to say several times faster than the steel cable and potentially serous.

Clearly there are many variables, but there is no question that the holes require attention if bare cable has been used. Better yet, stanchion holes should ALWAYS be polished before switching to fiber. From what I am seeing, that is well worth putting in the instructions, and inspectors should examine the line, at least on the uppers, for signs of excessive wear. Any grooving of the stanchion holes is a very serious sign, near positive proof that there is an internal problem (the burr is most likely worse on the inside, out of sight).

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  • 7 hz
  • 4cm stroke
  • 1 kilogram

I played with more force, but depending on the surface you can start building heat, and that introduces another variable. At this load I can replicated the fuzzing I see in my running rigging, though I'm sure at higher loads things change. However, the heat build-up represents a practical limit in accelerated testing past which we cannot go; if I do more than a certain amount of work on the surface, I risk heat effects, whether I chose high speed and high load, or low speed and heavier load.

 

For example, I've used everything from wood to grindstone as abrading surface, and certainly the mode of failure changes. But generally the rank-ordering does not (some times it does), which makes me feel the results probably have a fairly wide range of applicability, at least in like-to-like comparisons. But it is important to remember that different surfaces cause different sorts of wear; a grindstone is not just faster than wood, it is different. Generally I've been using wood with polyester line, as it seems more reasonable; if you have a grindstone-like situation, you need to fix the situation! Lifelines are different. Reality is SS and drilled holes. The motion should also be different, but this is what I've got.

 

One thing I cannot do, is wear clean through lines. Because of the low force and short stroke, as soon as I get through the cover, things start to bunch-up and time values get very distorted, depending on the construction. So long as I stop at a pre-determined point, whether DB or SB, the times are quite repeatable.

 

---

 

So, does the lifeline abrasion look similar to what you have seen caused by sharp stanchion holes, or is it different in appearance? It is surprisingly hard to get dyneema to wear. As I mentioned in my blog post, polyester seems to wear about 20-100 times faster. Against wood, in this motion, I'll be retired before it wears (a few days, anyway).

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^^ I also tested the dyneema sleeve fixed to the line so that it moved through the hole (before and after the wire cut the groove). Very impressive, outwearing Sunbrella by about 50x. I ran it for over an hour, by which time the hole had stopped being sharp!

 

And this is why the specific motion probably matters. If the edge is, in effect, a low quality knife, if you want to cut the line you need to use just the right strokes. Otherwise, the knife is dull before you get very far. But for comparison purposes, it probably makes little difference.

 

The cross-braid motion article got me thinking, where does that rolling under high load thing happen on sailboats. Spinnaker halyards came to mind. I can see how accelerated internal wear, combined with external wear, could cause failures that didn't make sense. But if you think of the chute rolling side-to-side, internals wear could be major. I wonder if a products like RP25 and Maxijacket can hold the fibers in place, reducing movement? I think that may be part of the point. Cats don't really roll down wind, and we use A-sails that roll less, so I've never learned about the problem.

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I really enjoyed this thread. I spend most of my reading today on pages 3 and 4. There was a lot of discussion on jackline strength and that basically it is about impossible to get to 4500 lbs pulls strength. In the absense of reading the pages up to this point, has Estar or anyone else considered making the jacklines with two looped ends from 3 pieces of webbing? One piece would form the primary length between the looped ends and each looped end would be made from a separate piece the length of the loop plus twice the length of the sewn area. These ends would be folded over to look like a "U" and the primary webbing length would be sandwhiched between the "U". The stitching would go through all three layers of webbing/ This would create a stitch loading similar to the continuous loops discussed that mountain climber use, as well as industrial lifting straps.

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  • 7 hz
  • 4cm stroke
  • 1 kilogram
  • So, does the lifeline abrasion look similar to what you have seen caused by sharp stanchion holes, or is it different in appearance?

I would be curious about much more load, much shorter stroke - don't know if you can accomplish that.

 

Here is a photo of a cut lifeline (from a german boat)

 

post-8534-0-56567200-1395019979_thumb.jpg

 

 

 

making the jacklines with two looped ends from 3 pieces of webbing?

That's an interesting idea . . . it is a little like the parachute reinforcement technique, particularly if the 'folded over loops' had staggered ends. I am not sure if it would work or not . . . I have good intuition about knots and splices but thinwater has much better intuition about these sewn webbing joints than I do. I could test it if you would like?

 

Personally, If I were making a pure webbing jackline (eg one with no dyneema cord reinforcement), Given what I now know, I would definitely make it as a sling. That seems to be by far the best structure (in loading both the webbing and the stitching evenly), and is essentially what all high load commercial lifting strops are and what all climbers use. And it is not much more work than making the loops at the ends - it only takes one 'high strength' join (sewing the two ends together) plus some long zigzag sewing down the length to hold the two parts of the sling together except for the ends.

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Estar - haven't read all ten pages so apologies if this is a repeat, but was wondering about avoiding the need for using jackline end loops at all, by cleating the webbing to bow and stern cleats? A few figure 8's over the cleat body, ending with a locking hitch seems to lie pretty well if you take the time to lay it down right. This gets away from the stitch issues, just not clear if the cleating adds a new weakness? Probably depends on cleat geometry.

 

BTW we use 1.5" diameter spliced Amsteel Blue for hauling dead right whales up soft sand. 90 ton breaking strength is what we found was needed by trial and much error. Big track laying caterpillar test rig....see first image in http://www.int-res.com/articles/feature/d096p175.pdf When we did the math for the weight of equivalent hard shackles we stuck with eye splices and cow hitches if need be.

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  • 7 hz
  • 4cm stroke
  • 1 kilogram
  • So, does the lifeline abrasion look similar to what you have seen caused by sharp stanchion holes, or is it different in appearance?

I would be curious about much more load, much shorter stroke - don't know if you can accomplish that.

 

Here is a photo of a cut lifeline (from a german boat)

 

attachicon.gifcut lifeline.jpg

 

Interesting, and different from the normal chafe mechanism.

 

I wonder if a heavy weight, a pendulum, and a suitable edge would be more similar in function than a sawing motion, if the cutting is caused by rail meat (was it, do you think?). That actually, would not be too difficult to set up; a few hundred pounds, swinging under a porch, with limit pin that determine how far the line slides across an edge. Should the edge be sharp or rough? How to keep it uniform? One thing I like about would is that I could slide up a fresh sawn edge for each test, very easy, always the same. Perhaps a fresh saw cut on a steel angle, using a port-a-band, with stops about 2 inches apart?

 

So long as the chafe gear can roll, separate from the line, there will be no important wear. I wonder how RP 25 would fare?

 

Guess I'll find out. Suggestions welcome.

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Estar - haven't read all ten pages so apologies if this is a repeat, but was wondering about avoiding the need for using jackline end loops at all, by cleating the webbing to bow and stern cleats?

We have done no cleating testing (yet). Sometime here I need to bolt a cleat to my bench. But I suspect, with webbing, there is no strength concern with cleating (the bend radius' would all be good) but there may be a slipping concern.

 

On our own boat I cow hitch the front of the jacklines and cleat the back end (with lots of figure 8's as you suggest) and I find the cleated end slips (but only on passage over several days) and I think a loop/lashing would be preferable. There may be a structural way to stop this slipping, like a tug boat hitch . . . I have never really focused on it, just recleated it tighter.

 

We at least have big cleats, but a lot of race boats do not.

 

As I have said a couple times . . . I depend on and trust my work station hard clip points much more than jacklines . . . I think the normal jackline setup is over emphasized/rated as, as implemented on most boats, while it will keep you attached to the boat, it will not keep you on board. There are better jackline systems/implementations, like near centerline ones, which will keep you on board, but they are rarely used.

 

, if the cutting is caused by rail meat (was it, do you think?).

There were 5 guys doing the full hike . . . All dumped in the water when it broke.

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^^ I think I can rig up a pendulum with a heavy weight that could simulate the side-to-side sawing. I can use a fresh sawn steel edge, perhaps just dulled with a file. I will need to limit the angle (90 degrees would be too much) to perhaps 30 degrees to keep the cutting mechanism similar. Perhaps the results will be no different than the oscilating test, but I will see. Chafe guards, too.

 

How much weight, I wonder. They don't have their full mass on the line, so perhaps 150 pounds. Hell, I might modify a swing!

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^^ It was easier and more complete to write a quick blog post. 4 pictures.

 

http://sail-delmarva.blogspot.com/2014/03/wire-cable-vs-stanchions.html

 

Interesting results.

 

Most stanchions that I've seen have a ferrule inside the hole. It would be interesting see how results compare when that is there. It would reduce the sharp edge. Here is a photo of a pile of stanchions from Minney's and you can see the ferrules:

DSC05778.JPG

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^^ Estar's point is that whether the edge were smooth to start--certainly many are but some are not--fiber lines are always retrofits, which means something has been in there wearing on the hole for years. Best case, it was coated line, worst case--I tested this--is bare cable, which will make the edge plenty sharp. The case of line breakage that peaked Estar's interest (the photo is a number of pages back--gotta follow the whole thread), the one he posted photos of, was cut on a stanchion with a ferrule just like you posted, that had been rubbed sharp by cable.

 

I can tell you that if the edge is smooth there will be no significant wear. Amsteel is tough.

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^^ I think I can rig up a pendulum with a heavy weight that could simulate the side-to-side sawing. I can use a fresh sawn steel edge, perhaps just dulled with a file. I will need to limit the angle (90 degrees would be too much) to perhaps 30 degrees to keep the cutting mechanism similar. Perhaps the results will be no different than the oscilating test, but I will see. Chafe guards, too.

 

How much weight, I wonder. They don't have their full mass on the line, so perhaps 150 pounds. Hell, I might modify a swing!

On that point, an interesting IRATA video here: http://www.irata.org/pdf_word/High_speed_video_300fps_82.61_kg.wmv

 

And here:

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^^ Thanks for the post. It is not very different from what I proposed, and now I see it is the wrong test. The sawing is too exaggerated. For example, if the pendulum were restrained within an oversized hole, the rope would rope inside a chafe guard, without really sawing action. Thus, the surface should be a stanchion hole (rough hole drill in SS tube). I will use a similar angle, perhaps 30 degrees, since a sharper angle might introduce new factors.

 

Aluminum is also wrong, at least for Dyneema; it would just dull the edge! Heck, it dulls SS after a few trials and must be resharpened (redrilled). I think we have all learned this about Dyneema; you need a knife with very hard steel and a very sharp edge. Scissors, unless you find a very good pair, don't live more than a few cuts, and ruining good scissors is foolish.

 

I'm going to build a small pendulum, as described above, And test some of the same materials.

 

---

 

Estar, I can see no reason to investigate the 3mm WR2 size; if only the core can be counted, it's too small to pass the strength requirement, am I correct? Though personally (cruiser looking for a long-term answers) I would go 6mm + chafe guards, I gather that the 5mm size meets the requirement and the cover should protect the core. As a climber, I've used plenty of 5mm high-tech cord and believe in that size.

 

--------

 

And BTW, in the videos they did it all wrong. You don't cover the rope, you pad the edge. I've done this sort of access any times, bot climbing and industry (distillation towers). A door mat over the edge would wear for years and is much simpler to rig. This same point applies to boats; pad the edge on the dock with carpet or rubber if it is very aggressive. This is the same reason the best chafe guards float; under pressure, anything that moves cuts.

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Estar, I can see no reason to investigate the 3mm WR2 size; if only the core can be counted, it's too small to pass the strength requirement, am I correct?.

.

Yes, the 3mm wr2 is too small - does not pass either the US or ISAF regs for any vessel size. The 5mm size has a 4mm core and only passes ISAF minimums for vessels under 8.5m (28'). You need the largest 7mm size (with 5mm core) for any vessel over 28'.

 

You could test the 5mm stuff, if the 7mm is to strong to break. The question at hand is whether a 5mm single braid would be 'better', in reserve strength after xx amount of use (actually, the wr2 really needs to be equal after 175% use to account for its price premium).

 

I personally think the 5mmm (with 4mm load bearing core) is pretty wimpy. The 7mm stuff is decent. I would trust it. But again, the relevant question is if 7mm single braid would be 'better'.

 

Related to that ship chafe paper - Do you know of any source that shows the braid angle/tightness for the various dyneema single braid alternatives? That would be interesting info to have.

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^^ To be specific, "better" than what? Should we compare 5mm WR2 to...

  • 1/4" Amsteel
  • 3/16" Amsteel
  • 3/16" Amsteel with dyneema chafe guard
  • Something else?

The problem is I don't know how to strength test. If they are near full strength the dog bones would need good bury splices, and we don't have that much pull length. The alternative, is to wear them until they are measurably thinned a certain amount, which may be valid. Generally, in chafe testing a combination either wears like iron or falls apart. There is often surprisingly little middle ground. The pendulum videos showed that. My testing seems to divide cases into...

  • Severe damage in less than a minute.
  • Visible damage, generally not too more than a failed cover, in 20 minutes.
  • Hours and hours.

It's rather like a drill: slices through, it does something and then dulls or the surface hardens like drilling SS with no coolant, or it does nothing at all, like drilling ceramic. It's like that. Visual might be enough.

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^^ To be specific, "better" than what? Should we compare 5mm WR2 to...

  • 1/4" Amsteel
  • 3/16" Amsteel
  • 3/16" Amsteel with dyneema chafe guard
  • Something else?

I would suggest test 5mm wr2 vs 5mm ENDURA 12. I think that is the best apples to apples comparison to test the 'design' issue: single braid vs double braid. Those would both be SK75, and I presume similar braiding qualities. NER could not complain about such a test. Testing vs amsteel might bring in other uncontrolled factors (like them measuring diameters and strength differently).

Generally, in chafe testing a combination either wears like iron or falls apart. There is often surprisingly little middle ground. The pendulum videos showed that. My testing seems to divide cases into...

 

Well I guess it will be best to test some and see what happens. You are suggesting either they will both cut thru pretty easily, or they will both wear like iron and neither show much, It happens to fall in the middle ground, then you (or I) could pull test them to determine residual strength.

 

I would expect the wr2 cover to be more wear resistant than than the single braid - but how much? Does it make up for the fact that the single braid is 50% stronger/has strength to burn before it gets down to the wr2 strength?

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^^ To be specific, "better" than what? Should we compare 5mm WR2 to...

  • 1/4" Amsteel
  • 3/16" Amsteel
  • 3/16" Amsteel with dyneema chafe guard
  • Something else?

I would suggest test 5mm wr2 vs 5mm ENDURA 12. I think that is the best apples to apples comparison to test the 'design' issue: single braid vs double braid. Those would both be SK75, and I presume similar braiding qualities. NER could not complain about such a test. Testing vs amsteel might bring in other uncontrolled factors (like them measuring diameters and strength differently).

>Generally, in chafe testing a combination either wears like iron or falls apart. There is often surprisingly little middle ground. The pendulum videos showed that. My testing seems to divide cases into...

 

Well I guess it will be best to test some and see what happens. You are suggesting either they will both cut thru pretty easily, or they will both wear like iron and neither show much, It happens to fall in the middle ground, then you (or I) could pull test them to determine residual strength.

 

I would expect the wr2 cover to be more wear resistant than than the single braid - but how much? Does it make up for the fact that the single braid is 50% stronger/has strength to burn before it gets down to the wr2 strength?

 

OK, but I'll through in Amsteel too, since that is a user option. I wouldn't expect Endura and WR2 to be very different. Some will also depend on how much the core floats inside the cover. I will also test smaller Amsteel with a separate cover. I'm guessing that the separate cover will float and give different results from covered line. I can tell you right now, that a floating dyneema sleeve would last for days or weeks, not minutes or hours. But some won't like how it looks. Then again, the covered cores may last so well as for any difference to be academic. That is actually likely, but I don't know, since the covers are MUCH thinner and looser than the NE sleeve.

 

How do we break them? Dogbones, with proper buries, will be too long. These dog bones will be nearly 1 meter, no?

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post-19172-0-31877300-1395181247_thumb.jpgGreat minds tend to run in the same ruts, it appears. I've been working on an untiable bend, and have come up with a structure somewhat analogous to what Allen has been testing (attached, I hope). Will send samples to Evans. In the shop I've tested it to breaking in kite string; no slippage, and it was untiable, even in that teensy line, after significant loads. I've also tested it against lock Bowlines, and the Bowlines lost. We'll see what the machine says.

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There are two parts coming out of the bottom. As for what the knot is, in the first picture here, I've put the ends through each other, making a false locked Brummel (it comes apart when you pull on the standing parts), then take the ends through each other's holes, so each end makes a 360. Next picture, the ends have been passed around their standing parts, then through the hole in the middle. Next the ends are tucked under the turns formed around the standing part. Finished knot in previous post. Pretty fast to make.

post-19172-0-78364300-1395196244_thumb.jpg

post-19172-0-88170700-1395196255_thumb.jpg

post-19172-0-20840000-1395196263_thumb.jpg

post-19172-0-78364300-1395196244_thumb.jpg

post-19172-0-88170700-1395196255_thumb.jpg

post-19172-0-20840000-1395196263_thumb.jpg

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brian, 1190lbs (48%) in 1/8" amsteel. That's good for a knot, and it is untiable, but I expected more from a 'hybrid'.

 

The weakness appears to be that the load pulls on the side of the pass-thru's and thus comes on only half the stands. If you can modify it so that the load on the pass thru's is more "in line" I believe it would test much higher.

 

It is certainly untiable. I think it is the only amsteel 'knot' I have been able to untie by hand (without a spike) after being taken to breaking point.

 

No-load:

post-8534-0-20732400-1395235419_thumb.jpg

 

Broken:

post-8534-0-93791900-1395235432_thumb.jpg

 

untied:

post-8534-0-87516900-1395235443_thumb.jpg

 

BTW, I am going to test some 'knot substitutes' for making loops - including the clamptite wire claimp tool (to make wire whippings), and the ez-splice. I tried to get some of the splicenuts but could not figure how/where to get them. I could find no retail outlet in the US and when I tried to get them from their website it has a 'fatal error' when you submit the address page. Perhaps they are pretty much out of business? Anyone know? Any other such things I should test? I honestly don't expect any of these to do better than a simple knot, but I could always be surprised, that's why we test.

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post-19172-0-81480600-1395276078_thumb.jpgpost-19172-0-80642100-1395276109_thumb.jpg

 

 

I am glad to hear that the hybrid was fairly strong, as well as untiable. But now that my brief, achieving-the-Grail euphoria has passed, I agree that an even stronger knot would be better. So try this: take the ends around, as in the previous knot, but make 3 passes. Leave a generous amount of length in the passes. Then simply bend the ends together. In the second picture, I show a simple Surgeon's Knot. I used this for a kite string test, and it held, and it was untiable after the break.

If that bend doesn't work, perhaps Ashley's or another would.

The logic here is that the extra pass results in decreased load on the final knot, and that the length of the knot means that the angle of the ends, on the way to the knot, is relatively shallow; this might result in more even loading of the fibers at the tucks.

If this knot works, its sheer simplicity would make it most attractive, even if it was only as strong as the previous knot. For my test, I made only a cursory effort at fairing; the turns equalized as the loads came on.

Another approach would be to have the ends going in opposite directions. This would entail a half-twist of the turns, but would make for a fairer lead to the knot at the finish.

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^^ brian, a bit better - 1340lbs (54%) . . . but I think our target for a 'hybrid' should be about 70%.

 

Half the strands broke at one of the pass thru loops, opening the loop

 

It a slippery. I tried your Surgeon's Knot and it slipped. I ended up with a zeppelin which held. I did get it untied but it took a spike to get it started.

 

Despite it being a bit weaker, I think I like the first one better. . . . more compact and easier to untie.

 

post-8534-0-82576800-1395336279_thumb.jpg

 

post-8534-0-98255800-1395336288_thumb.jpg

 

While we are looking at hybrid's . . . the diamond knot is currently the weak point of the soft shackles.. If we could find a better hybrid it would strength the soft shackles. We need to strengthen the area where the two lines enter the diamond - perhaps burying the tails into themselves at that point would work.

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[snip]

While we are looking at hybrid's . . . the diamond knot is currently the weak point of the soft shackles.. If we could find a better hybrid it would strength the soft shackles. We need to strengthen the area where the two lines enter the diamond - perhaps burying the tails into themselves at that point would work.

 

I've often wondered about that last pass that takes us from a Carrick bend to the Diamond knot and it's effect on strength. So I wonder is it possible to bury the ends before making that pass and just leave us with a Carrick bend with buried ends? All my cordage is on the boat otherwise I'd tie one.

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Okay,

Next iteration, two more tuck points. Start as for the first knot, then tuck each end back through the standing part a short distance (4 diameters or so) outboard of the first tuck. Then pass each end around the standing part, through the new eye, and hitch as before. I'm hoping that, by spreading the load,the effect of the off-angle pull will be lessened.

post-19172-0-35636300-1395348213_thumb.jpg

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post-19172-0-95915400-1395348243_thumb.jpg

post-19172-0-56169500-1395348263_thumb.jpg

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IMGP0123.jpg

 

Ask and yea shall receive. Try this out. It is basically a double line version of the halyard hybrid you tested for me on #940. Looks nice too because there are no tails.

 

Allen

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I will test Allen and brian's hybrids over the weekend - Allen, that looks very nice, but I can't quite figure out what you did? Is it a diamond or a 'noose'? - a photo just as you are tucking the tails, with the knot still loose, would be helpful for me.

 

On another, topic loop making hardware . . .

 

The EZ Splice is a piece of plastic with two holes drilled in it and a dozen stainless steel nails. You stick the rope thru the holes and then nail it in place. It actually looks and feels pretty impressive, but in 1/2" nylon line it broke at 36% of line tensile, when a bowline would go to 70%.

 

post-8534-0-04977800-1395354853_thumb.jpg

 

The Clamp-it is a tool for wrapping wire tightly and neatly around things. It is primarily designed as a hose clamp replacement. The mfg does not make much of its potential for making loops in rope but does mention it in passing. The problem with these wire clamps in nylon, is that as the rope loads up it gets thinner, and thus slips out from the clamps, at 12% of 1/2" nylon tensile. In the picture below, the loop has collapsed, and the tail now starts slipping out It would probably do much better in lower stretch line - I will test that later.

 

post-8534-0-71699500-1395354876_thumb.jpg

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^^ I took a couple of turns with both tails, then tucked then through the turns aka "stopper knot" or triple fishermans. Then I ran the shackle body through so that all the single strand, after the bury in the body of the shakcle, was showing below the knot I just made. I tucked each end inside one of the strands. Then I pulled and tightened up the knot which sucked these buried ends inside the knot. I need to go do some things so if this isn't clear, I can do a write up this evening.

 

Allen

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I will test Allen and brian's hybrids over the weekend - Allen, that looks very nice, but I can't quite figure out what you did? Is it a diamond or a 'noose'? - a photo just as you are tucking the tails, with the knot still loose, would be helpful for me.

 

On another, topic loop making hardware . . .

 

The EZ Splice is a piece of plastic with two holes drilled in it and a dozen stainless steel nails. You stick the rope thru the holes and then nail it in place. It actually looks and feels pretty impressive, but in 1/2" nylon line it broke at 36% of line tensile, when a bowline would go to 70%.

 

attachicon.gifez4w.jpg

 

The Clamp-it is a tool for wrapping wire tightly and neatly around things. It is primarily designed as a hose clamp replacement. The mfg does not make much of its potential for making loops in rope but does mention it in passing. The problem with these wire clamps in nylon, is that as the rope loads up it gets thinner, and thus slips out from the clamps, at 12% of 1/2" nylon tensile. In the picture below, the loop has collapsed, and the tail now starts slipping out It would probably do much better in lower stretch line - I will test that later.

 

attachicon.gifct2w.jpg

 

EZ Spice. Yup, that's even a little less than what I saw, with some rope tearing and some pins pulling through. I suspect it would be considerably worse on nylon, since in my test it was clear the lead pin went frst. I can only guess some folks hate the look of a knot.

 

Clamp-it. I'm trting to get good advice on siezing, because I'm no good at it. Like you example, my tests slide at low figures... though considerably better than that! I can also tell you that seizing in nylon are laughable; the line gets so skinny under load they have no chance.

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IMGP0123.jpg

 

Ask and yea shall receive. Try this out. It is basically a double line version of the halyard hybrid you tested for me on #940. Looks nice too because there are no tails.

 

Allen

That is seriously elegant. I hope it tests well!

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I can do a write up this evening.

Please . . . I think this may be a real step forward, solving the two weaknesses of the diamond, while looking real nice.

 

I am in meetings all tomorrow, so will not get back to this until Saturday.

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^^ The second one I made, and captured with a series of photos, didn't work. I modified the instructions to allow for more line so the bury part of the splice can be longer. You need enough bury so that the splice holds together as you tighten up the knot. It came apart on this try but I think the pictures still show how to make the thing. You might have to fiddle with the knot to get the right amount of line showing for the splice.

 

By the way, this knot is 60% larger than a diamond knot. I don't k now if that is good or bad.

 

http://l-36.com/strong_soft_shackle.php

 

If it is strong, I will re-do the pictures and post the page. For now it is not indexed.

 

Allen

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That's cool. I hope it works out stronger. Is something like that patentable?

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Meeting break . . .

 

 

Allen, first the good news . . . 221% (5530lbs in 1/8" amsteel), so we are on the right track.

 

But the bad news . . . it has two flaws . . . first it is not a stable knot under load. I am not sure exactly what it did but it looked like it turned itself inside out. Second, it is hard to get adequate buries - I even used a few inches more line that you suggested - and the failure here was actually a bury pull out.

 

here you can see the knot deforming

 

post-8534-0-82716300-1395428033_thumb.jpg

 

and here is the final failure mode

 

post-8534-0-87243000-1395428060_thumb.jpg

post-8534-0-83338900-1395428083_thumb.jpg

 

. . . more in next post

 

 

 

 

 

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So, I quickly looked for a way to make longer buries easier and for something that was stable under load, and think I found one. Full details here. Summery below:

 

This one breaks at the noose bend radius at 233%, so we are at a fundamental strength limit. I think this one is also generally easier to make.

 

post-8534-0-93454700-1395428262_thumb.jpg

 

post-8534-0-31709300-1395428275_thumb.jpg

 

post-8534-0-03237200-1395428287_thumb.jpg

 

post-8534-0-78166100-1395428297_thumb.jpg

 

The only drawback I can see to this one is that it is not as easy to tighten by hand.

 

. . . ok, back to the business meetings :)

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^^ that is a good one. I was trying to think of how to make the bury involved in the knot. That provides added bury length without extending too far into the body of the shackle. This is a winning design. It looks easier to tie than what I came up with although I might point out it is only slightly stronger :-)

 

To get stronger, you need to bulk up the body of the shackle where the eye goes and increase the bend radius. But the splice does that if it extends past the knot.

 

Allen

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^^ I am looking at the pictures of your test on the design I did. It looks like the splice is not inside the knot. Is that because the knot capsized or was it just not spliced right? I think it is important that the splice be inside the knot.

 

Allen

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So to put that another way am I right in saying that we've gone from the Diamond knot breaking in previous tests at ~42% of theoretical (which is 4 x the material strength) or therefore .42*400 = 168% of material strength to breaking at ~58% of theoretical? If so that's a major gain.

[snip]

This one breaks at the noose bend radius at 233%, so we are at a fundamental strength limit. I think this one is also generally easier to make.

 

[snip]

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Leaping back from our current breakthrough to something that was discussed several pages/weeks ago...safety lanyards. A lot of that discussion centred on using dynamic rope lanyards (to limit shock loads) and we then travelled a winding path looking at sewn terminations.

 

I can't remember whether we covered this specific issue though, so here it is: http://www.escalade.com.au/rescue/media/lanyard_tests_v6.pdf

 

That testing suggests that the material used contributes a relatively small part of the shock absorption and that the single most important factor is that the terminations are knotted not sewn. Indeed my reading of the results suggests that you can get fairly acceptable shock load results with a knotted semi-static lanyard, although clearly a knotted dynamic lanyard is better.

 

Further the knot of choice, at least at the karabiner/clip appears to be the barrel knot which appears to deliver marginally better performance than the figure of eight. It would also seem to suggest that knots need to be opened, inspected and remade at regular intervals, particularly after shock loading, in order to maintain the benefits they bestow. It would also appear that to be really safe in repeated loading you shouldn't use an overhand knot and your rope should be 11mm...

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We've talked a bit about knots heating up. Here's some video of a load test with infra-red imagery as well:

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^^ I am looking at the pictures of your test on the design I did. It looks like the splice is not inside the knot. Is that because the knot capsized or was it just not spliced right? I think it is important that the splice be inside the knot.

 

Allen

They were inside at the start and then it turned inside out. I agree that the bury needs to be inside, particularly if it is short. I am pretty sure I tied it per your instructions. The strength is good, but the instability would scare me in application.

 

With the 'overhand/loop stopper', the question is if there is anything we can do to make it easier to tighten by hand. Perhaps just bending the buried sections back and forth would help, or smashing them with a hammer. You might give it a try as you have more experience tightening up these sorts of knots.

 

 

So to put that another way am I right in saying that we've gone from the Diamond knot breaking in previous tests at ~42% of theoretical (which is 4 x the material strength) or therefore .42*400 = 168% of material strength to breaking at ~58% of theoretical? If so that's a major gain.

 

[snip]

This one breaks at the noose bend radius at 233%, so we are at a fundamental strength limit. I think this one is also generally easier to make.

 

[snip]

Yes, we have just essentially obsoleted all prior soft shackles. No matter which of the two designs, or a third further improved one, we have made a significant gain in strength (moving from about 160% to 230%) while in fact making them easier to tie. The diamond was always both the weak point and the hardest thing for new people to figure out. It will be interesting to see how long it takes the guys who are selling these things to catch on.

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