Stopper Knot for Dyneema

[estarzinger]

Originally Posted by Pyxis156

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?

I don't think it is necessary (for yachting applications) with the double rubber dipping and a decently tight splice.

But there is a theoretical/potential failure mode of the toggle getting whacked out of the splice (in say a violent flogging) and the groove would prevent/minimize that - I've never seen it or heard of it actually happening.

[stnick]

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[ImaginaryNumber]

Originally Posted by estarzinger

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, thanks for your suggestions. I hope you don't mind a few more questions.

Is there any particular trick to making the noose tight around the toggle (other than turning a groove into the middle of the toggle and/or coating the loop/toggle with rubber coating)? Do you whip the noose to ensure that it stays tight?

When using aluminum for the toggle (vs stainless steel), I take it you prefer the strength of 7075 vs the corrosion resistance of 5086? Maybe 7075 has sufficient corrosion resistance when used in above-water applications? I think 6061 is somewhat between both 7075 and 5086 in strength and corrosion resistance.

I'm surprised that you found that a rubber-coated aluminum toggle caused no more impact damage than a tightened button knot. What sort of a test do you use to come to that conclusion? I assume it was the end of the toggle that was most apt to cause damage. How did you shape it? Was it just lightly chamfered at a 45* angle, or did you make it a full hemisphere? [edit: Oops -- I see you answered my question -- you used a fully rounded end]

Finally, have you ever described online your line/knot test bench setup (other than, perhaps, on your now defunct website)? Or can you direct me to a generic DIY test bench site?

Thank you.

[estarzinger]

Originally Posted by ImaginaryNumber

Is there any particular trick to making the noose tight around the toggle (other than turning a groove into the middle of the toggle and/or coating the loop/toggle with rubber coating)? Do you whip the noose to ensure that it stays tight?

No "particular trick". Sewing (lock stitching) is proper procedure, every splice is sewn in the commercial environment. Whipping is optional - more for finished looks than functionality. You could use some sort of friction hitch on the toggle (inside the loop) but I have not found it necessary (and it would possibly decrease the strength a little) - A simple properly done loop drawn tight with the tucks/bury pulled very smoothly will do the job.

When using aluminum for the toggle (vs stainless steel), I take it you prefer the strength of 7075 vs the corrosion resistance of 5086? Maybe 7075 has sufficient corrosion resistance when used in above-water applications? I think 6061 is somewhat between both 7075 and 5086 in strength and corrosion resistance.

Rubber coated I do not think there is much corrosion concern, so Yes, I go for strength. But unless you are pushing the edge of the application strength, any of the aluminum alloys you mention will be fine.

I'm surprised that you found that a rubber-coated aluminum toggle caused no more impact damage than a tightened button knot. What sort of a test do you use to come to that conclusion? I assume it was the end of the toggle that was most apt to cause damage. How did you shape it? Was it just lightly chamfered at a 45* angle, or did you make it a full hemisphere? [edit: Oops -- I see you answered my question -- you used a fully rounded end]

I had a commercial lab do this testing. Impact testing is a not too uncommon procedure. They had a machine which 'flailed' the toggles - against two different surfaces ( a malleable one and a brittle one) Under constant flailing loads they compared the relative size of the divots in the malleable surface and compared the breaking load for the brittle surface under increasing flailing loads.

A soft shackle stopper that has been fully loaded is in fact quite hard - knock it on a table and it should sound like a rock.


Finally, have you ever described online your line/knot test bench setup (other than, perhaps, on your now defunct website)? Or can you direct me to a generic DIY test bench site?

If you do a search you can find commercially available equipment which does pull tests. It is all quite expensive, and if you build it yourself it is significantly cheaper, or there are certainly good labs which you can pay per pull to do the testing - I seem to remember I did a break-even calculation for SL which suggested if you were planning to more than perhaps a hundred pulls it was cheaper to roll your own.

The only expensive item really is the load cell and there is an extremely wide range of capabilities and costs for them depending on what exactly you want to be able to do. To create the pulling load an electric screw drive is best, but hydraulics are cheaper, ( look for auto body puller rams) you just have to be prepared to rebuild it because the repeated shock load when high modulus rope breaks will kill the seals and surfaces. The actual bench can easily be made out of I beam (I used aluminum but steel is cheaper).

...........

[hpeer]

I’d love to see a couple of pics of these these toggle thingies.

Pics of a link?

[ImaginaryNumber]

Thank you, Evans, for the added information.

Originally Posted by hpeer

I’d love to see a couple of pics of these toggle thingies.

Pics of a link?

One of the CF members, Benz, has a company which sells non-rubber-coated toggled soft shackles.

[hpeer]

Thank you. Helps to clarify. Not what I was imagining.

[estarzinger]

^^ btw I am NOT pushing toggle use (over stopper knots).

The toggles are perhaps easier to use with gloves (volvo race used them for that reason), and they are better if you are trying to create an overall extremely high strength/ high-reliability design . . . but for general recreational marine use, a stopper knot design is typically easier (once you learn how to tie the stopper) and just fine.

[fugue137]

Originally Posted by Juho

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.

Good explanation! I saw a talk by Vishal Patil that touched on this, partially confirming it and also pointing out the importance of another crucial factor: rope twist reversals. Here's a blurb:

https://news.mit.edu/2020/model-how-strong-knot-0102