Stopper Knot for Dyneema

[thinwater]

My understanding is that this has not been tested for pull-through strength in Dyneema? Maybe I'll do that.

[Seaworthy Lass]

Originally Posted by thinwater

My understanding is that this has not been tested for pull-through strength in Dyneema? Maybe I'll do that.

That would be great.
I have not seen this stopper used for dyneema before, let alone read of any load tests.

SWL

[Jim Cate]

SWL, in an application such as yours, I'd maybe think about using a toggle spliced into the end rather than a stopper knot. A short length of hardwood dowel or Aluminium round stock would be adequate.

Jim

[Seaworthy Lass]

Originally Posted by Jim Cate

SWL, in an application such as yours, I'd maybe think about using a toggle spliced into the end rather than a stopper knot. A short length of hardwood dowel or Aluminium round stock would be adequate.

Jim

Hi Jim
That is an excellent suggestion. If the knot starts slipping I will replace the dyneema and do this.

For now I will just watch it. There were decent tails left, room enough for another one of these knots to be stacked on, but it is performing well at the moment, so I will simply observe. Whipping the end of the tails is on my "to do" list though .

SWL

[olaf hart]

Originally Posted by Seaworthy Lass

Hi Jim
That is an excellent suggestion. If the knot starts slipping I will replace the dyneema and do this.

For now I will just watch it. There were decent tails left, room enough for another one of these knots to be stacked on, but it is performing well at the moment, so I will simply observe. Whipping the end of the tails is on my "to do" list though .

SWL

I am quite taken by these, just make a button out of hmwpe and a dyneema loop with a soft shackle end....

Button Shackle

[Juho]

Here's another thought on how one could add friction to figure 8 (and still be able to untie it).

(1) Tie a loose figure 8. (2) Twist an extra loop. (3) Working end through the loop. Tighten partially from the working end, then the rest from the standing end. If you want more friction, repeat steps (2) and (3). The knot is not very pretty, but it could work (enough friction, can be untied).

Another unrelated comment. In your transom use case it could be useful to have a stopper knot that can be easily made to an exact position in the rope, or whose position could be adjusted afterwards. But if it is permanent, then maybe jiggling few minutes with the rope is not a problem.

[Seaworthy Lass]

Originally Posted by olaf hart

I am quite taken by these, just make a button out of hmwpe and a dyneema loop with a soft shackle end....

Button Shackle

The buttons could be made easily in aluminium. I think more easily than machining a toggle. The principle is the same and if well made they should give the same "high strength" as soft shackles made with the button stopper. Load testing data to date shows around 230% line strength for these.

My theory is that close to 260% line strength is actually achieveable is the noose is correctly sized. I think current instructions tend to make the noose undersized, weakening strength. I am making nooses large enough to fit 6x line diameter. 8x may possibly be better. It would be nice to have this tested.

SWL

PS The main drawback of using buttons and toggles is that the soft shackle is no longer entirely soft, one beauty of the knotted versions.

[olaf hart]

I can’t see myself ever using 260% of dyneema line strength...

I suspect in time these things will be made with ordinary Polyethylene or Polypropylene core

[Seaworthy Lass]

Originally Posted by olaf hart

I can’t see myself ever using 260% of dyneema line strength...

I suspect in time these things will be made with ordinary Polyethylene or Polypropylene core

If strength is an issue, it is often simply easier to bump up line diameter than fuss with design. Not always though. I have just made a soft shackle for someone wanting to attach a block. SWL of the block was 3200 kg. Using 8mm dyneema and a "high strength" soft shackle design using a button stopper gives a SWL of around 3100 kg. A close enough match. Had a diamond stopper been used, SWL would have been around 2300 kg. I would have needed to use 10mm dyneema, which is 50% more expensive, and the soft shackle would have been longer, which was undesirable. It is also a diameter I struggle to work with. I was very thankful I didn't need to go to 10mm.

As well, the quest for improvement is an enjoyable and satisfying challenge .

SWL

[estarzinger]

stoppers . . . .

(in bare dyneema) The key knot design feature to eliminate/reduce slipping is to have one strand pressed against another (inside the knot) being pulled in opposite directions. Simply adding turns and tucks (surprisingly) does not do much to reduce slipping - that was the initial recommendation of the knot tying guild when I first started looking into these knots and they were astonished when my testing showed that the triple fisherman slipped and even adding further turns and tucks did not stop it. Note: in low strength applications this is all pretty irrelevant because the 'slipping' (in 'good' conventional stopper knots) only occured at decently high absolute loads.

As mentioned above, an aluminum toggle is really the best practice solution (if you are focused on strength and safety and reliability). And a rubber coated aluminum toggle (which is dead easy to DIY and inexpensive) does NOT generate more impact damage than a properly rock hard stopper knot (I tested diamond and buttons in impact). It may be that a double coated aluminum actually has less impact damage but my testing was not statistically conclusive than that but I can say it is not more. The primary reason not to use aluminum toggle would be aesthetic - which is certainly valid on a yacht - but I guess I personally am more of a 'form follows function' sort of guy . . . eg I feel beauty and aesthetics (usually) come from the best functionality (like bare aluminum hulls ).

[Rorzech]

What is a friction ring that replaces a block ? Isn't abrasion the main downfall of Dyneema ?

[Juho]

Originally Posted by estarzinger

(in bare dyneema) The key knot design feature to eliminate/reduce slipping is to have one strand pressed against another (inside the knot) being pulled in opposite directions.

The knot that I presented in post #14 tries to follow this principle as much as possible. First two strands are put next to each others (for the whole length of the knot). And later the end loop of these two strands is forced to go around another strand (the standing end of the knot), thereby forcing these two parallel strands to move in different directions. A similar technique could be used also in other knots than this basic figure eight variant.

[ImaginaryNumber]

Originally Posted by estarzinger

stoppers . . . .

(in bare dyneema) The key knot design feature to eliminate/reduce slipping is to have one strand pressed against another (inside the knot) being pulled in opposite directions. Simply adding turns and tucks (surprisingly) does not do much to reduce slipping - that was the initial recommendation of the knot tying guild when I first started looking into these knots and they were astonished when my testing showed that the triple fisherman slipped and even adding further turns and tucks did not stop it. Note: in low strength applications this is all pretty irrelevant because the 'slipping' (in 'good' conventional stopper knots) only occured at decently high absolute loads.

Evans, would you further elaborate what you mean by "one strand pressed against another (inside the knot) being pulled in opposite directions"?

As mentioned above, an aluminum toggle is really the best practice solution (if you are focused on strength and safety and reliability). And a rubber coated aluminum toggle (which is dead easy to DIY and inexpensive) does NOT generate more impact damage than a properly rock hard stopper knot (I tested diamond and buttons in impact). It may be that a double coated aluminum actually has less impact damage but my testing was not statistically conclusive than that but I can say it is not more. The primary reason not to use aluminum toggle would be aesthetic - which is certainly valid on a yacht - but I guess I personally am more of a 'form follows function' sort of guy . . . eg I feel beauty and aesthetics (usually) come from the best functionality (like bare aluminum hulls ).

Can you provide further directions for making rubber-coated aluminum toggles?

Thanks for all your testing and development.

[estarzinger]

Originally Posted by ImaginaryNumber

Can you provide further directions for making rubber-coated aluminum toggles?

hmmm . . . there is no real complication. The easiest, with like 95% of the benefits is to buy a meter of very common 6061 rod (sometimes called round bar) - you can get almost anywhere, home dyi shops, ace hardware, McMaster-Carr, etc; cut it into perhaps 3cm lengths with a hacksaw; use a file to round the ends/edges; get a bottle of (one of the many brands of) rubber dip (like just for example - https://www.boomkool.com/products/pe...paign=promoted or https://www.amazon.com/Rubberized-Pl...p/B000VS2HMK); then dip the 3cm piece first, let dry, eye splice the dyennema tightly to the center of the toggle, and then dip again and let dry (gives both a double thickness of dip and locks the dyneema in place).

^^ those common rubber dips can possibly get a bit slimy if they accidentally soak in something like diesel or wd40. That is not a common probably on board (more so in the commercial environments I have been working) You can over dip them with a urethane paint and that will (usually) prevent the issue. Or there are better liquid rubbers which are more chemical resistant but harder to find.

I use 7075 aluminum (or sometimes stainless), and I lathe the pieces (so there is a bit of a groove in the middle to hold the dyneema and the ends are completely rounded), and a rubber coating which is used as a truck bed liner for pick-up trucks.

As to diameter of the rod - you want it to be at least 1.2x the Dyneema diameter (after any lathing/grooving if you make any).

Evans, would you further elaborate what you mean by "one strand pressed against another (inside the knot) being pulled in opposite directions"?

I have not done much work in this area in quite a while. Really all I can say is that when I was testing this, both I and the 'knot experts' (like the knot guild) were surprised that adding extra loops and turns and tucks did not do much to stop slipping (in bare dyneema). I identified a few knots which did not slip and many had this common design/constructional trait of one strand ending up against another being pulled in opposite directions and being constricted/crunched against each other as the knot tightened under load.

I did not really explore it much, because splices are really the best solution for bare dyneema, even quick and dirty tucks or brummels (without bury); and if a knot was necessary I did find a solution in each knot category which did not slip. There were some standard well known fixed loop knots which worked, in noose knots a couple of the fishing ones worked, but the estar (modified buntline) seemed better (more compact and easier to tie) for many applications, none of the standard stoppers worked but the estar stopper worked did, I really never found a totally satisfactory bend which did not slip but there are some quick and dirty tuck splices which are good and two estar noose back to back worked fine (although with lower strength than the tucks)

............

[Pyxis156]

Originally Posted by estarzinger

The easiest, with like 95% of the benefits is to buy a meter of very common 6061 rod (sometimes called round bar) - you can get almost anywhere, home dyi shops, ace hardware, McMaster-Carr, etc; cut it into perhaps 3cm lengths with a hacksaw; use a file to round the ends/edges; get a bottle of (one of the many brands of) rubber dip (like just for example - https://www.boomkool.com/products/pe...paign=promoted or https://www.amazon.com/Rubberized-Pl...p/B000VS2HMK); then dip the 3cm piece first, let dry, eye splice the dyennema tightly to the center of the toggle, and then dip again and let dry (gives both a double thickness of dip and locks the dyneema in place).

^^ those common rubber dips can possibly get a bit slimy if they accidentally soak in something like diesel or wd40. That is not a common probably on board (more so in the commercial environments I have been working) You can over dip them with a urethane paint and that will (usually) prevent the issue. Or there are better liquid rubbers which are more chemical resistant but harder to find.

I use 7075 aluminum (or sometimes stainless), and I lathe the pieces (so there is a bit of a groove in the middle to hold the dyneema and the ends are completely rounded), and a rubber coating which is used as a truck bed liner for pick-up trucks.

As to diameter of the rod - you want it to be at least 1.2x the Dyneema diameter (after any lathing/grooving if you make any).

Thanks for this Evans, I am getting ready to make a new batch of soft shackles for my anchor snubbers and have used stainless toggles in the past, but am going to try your method above.

One question, do you think that machining a groove in the middle of the toggle is necessary / helpful if one applies the rubber in the manner you describe? Seems like the first coat of rubber would give the dyneema something to bed into, and the second would help lock it all in place?