An easy enhanced soft shackle

[Pilgrimtex]

The Diamond knot shackle is 135% the strength of the the dyneema line you use to make it. The Button knot shackle rates at 235% strength. This is because of the added thickness from burying the bitter ends.
The Diamond knot is easier to tie so many sailors settle for the lower strength. It's also what WM sells for $28.00 for a 1/4" shackle.
I have tried to learn the button knot to the point of throwing my Samsung pad across the cabin. I have serious PTSD.
Out of my frustration: I came up with the "Walter Knot" LOL.
You get the strength of the Button Knot with the simplicity of the Diamond knot.
the secret is after making the Diamond knot. Run the bitter ends back through the knot to come out the base of the knot. Leave 2 loops at the top of the knot. It will look like rabbit ears. Continue the usual tightening of the knot. I use a 6:1 purchase using blocks. When the knot is sufficiently tight you can pull on the bitter ends to reduce the size of the ears if you want. Next cut the two ends the same length enough to bury and that's it.

 

[Jackdaw]

OK.. but why use a knot so much stronger than the underlying line? The line will break first anyway with either of the knots.

 

[Jackdaw]

Got it! Cool!

 

[Pilgrimtex]

There is also a proper way to load a soft shackle. In the pic. Notice how the knot is oriented to the load. This places the least amount of strain on the knot base.

 

[colemj]

I was like you the first time I tried to tie a button knot. I spent 2-3 days attempting to get it and failing. Then my brain suddenly shifted (I think I actually felt and heard it do so!) and everything was obvious and easy. After that, I tied a bunch of them almost instantly.

Evens Starzinger came up with a very easy way to make a soft shackle that involved only an overhand knot on the end. It is dead-simple to make, but requires almost twice as much line as all the others. I think he called it "improved soft shackle" or similar. He took down his website, so the instructions aren't available there anymore, although you could probably search for it.

I don't worry much about the strength of the knot because all the applications I use the shackles for generally have much lower loads than the strength of the line used in the shackle. I look for cheap cutoffs and ends of dyneema whenever I'm in chandleries and pick up any odd 1/4" or 5/16" for shackles. With 8,000-13,000lb breaking strength, my needs are covered. Even if the knot was half the strength of the line (which it never is), it is usually still much stronger than any load they are used for.

Mark

 

[AaronD]

Not to dissuade anyone from trying @Pilgrimtex knot, which sounds like a good solution. But if you're looking for Evans' method, I believe it's #4 at
http://www.balancecommunity.com/slack-science/comparison-soft-shackle-methods. But Evans' instructions were much better than the description there. I have a copy archived - I'm not sure I should post them publicly, but if anyone wants them, PM me and I'll send them by email.

I discussed just a bit more at https://forums.sailboatowners.com/i...w-two-lines-or-one.183445/page-3#post-1353263.

 

[genec]

Obviously the soft shackle offers the advantage of allowing for a bit of movement... but ultimately isn't a hard shackle stronger?

 

[AaronD]

Obviously the soft shackle offers the advantage of allowing for a bit of movement... but ultimately isn't a hard shackle stronger?

Actually, probably not. UHMW Polyethylene (sold as Dyneema / Spectra / etc.) is much stronger than steel (especially 316 stainless) of the same diameter. For example, 1/4" Amsteel Blue (Samson's brand) has a rated breaking strength of 8600 lbs; and that's for a single line - since a soft shackle is a loop, they usually break well above line strength (120%-230%, depending on the design and knot used). Whereas Wichard rates their 1/4" stainless shackle (model 1403) at a breaking strength of 2200kg = 4840 lbs.

But - safe working loads for soft shackles are usually more conservative than for hard shackles (that actually applies to most if not all fiber vs metal comparisons - e.g. standing rigging). So a normal safe working load of a soft shackle might be 20% of breaking strength. For the 1/4" example, assuming soft-shackle with a good knot and a breaking strength at 150% of line strength, we'd get 8600 * 150% * 20% = 2580 lbs SWL. Wichard rates their 1403 at 680kg = 1496 lbs (~31% of breaking strength). You can play with those assumptions, but I think you'll generally find that safe loads are at least equal to that of a hard shackle of similar thickness.

But - the hard shackle will always be smaller, which can be a deciding factor in some applications (the loop has to fit over the knot, so there's a limit to how small you can make a soft shackle). Also chafe: UHMW fibers are surprisingly resistant to chafing (see @thinwater's experiments), but you still probably want to stick with steel in locations that might see significant abrasion.

 

[genec]

What about UV protection? A soft shackle needs some sort of cover for protection... a hard metal shackle does not.
Here is a link from Practical Sailor talking about "coating" soft shackles.
http://www.practical-sailor.com/issues/37_49/psadvisory/UV-Protection-for-Dyneema_11591-1.html

 

[AaronD]

What about UV protection? A soft shackle needs some sort of cover for protection... a hard metal shackle does not.
Here is a link from Practical Sailor talking about "coating" soft shackles.
http://www.practical-sailor.com/issues/37_49/psadvisory/UV-Protection-for-Dyneema_11591-1.html

Oooh - good point about UV. I live here in the Pacific NW, where any day with enough sun to even think the word 'UV' is grounds for communal celebration. And except for a short few months in the summer, my boat spends most of her life parked in the shop, so I can't say that I've put much thought into UV on my soft shackles.

But I should probably replace the ones on my jacklines (those are important!), and get a bottle of UV protectant. Thanks for the advice!

 

[genec]

When I kept my boat in San Diego... UV was one of my bigger worries... plastic got brittle, varnish just vanished, and I wondered about UV resistance for both the boat and myself.

In the PNW, I worry about rain intrusion and mold, and that damn green stuff that grows everywhere. (even on the rear view mirrors of my truck...) sigh. I think I saw the sun yesterday... but I'm not sure. I forget what it looks like.

 

[colemj]

Dyneema is very UV stable. There is no problem with uncoated or uncovered dyneema in the tropic sun. Our trampoline is laced with it and we live mostly in the tropics. We also have several soft shackles and runners out in the rigging. None of the dyneema has shown any signs of UV degradation. Racing boats routinely use uncovered dyneema running rigging, and lots of boats use it as standing rigging.

Mark

 

[Pilgrimtex]

Untreated dyneema retains 60% strength after 5 yrs in extreme sun conditions like Arizona, New Mexico. If a concern go up one size. Dyneema lifelines should be replaced after 8 yrs as a rule.

 

[genec]

Dyneema is very UV stable. There is no problem with uncoated or uncovered dyneema in the tropic sun. Our trampoline is laced with it and we live mostly in the tropics. We also have several soft shackles and runners out in the rigging. None of the dyneema has shown any signs of UV degradation. Racing boats routinely use uncovered dyneema running rigging, and lots of boats use it as standing rigging.

Mark

When I was a racing crew on a J-105, we always "skyed" our dyneema halyards to prevent exposure to UV after the races. By "sky" I mean we would attach a line to the shackle end of the halyard and pull the halyard into the mast to reduce UV exposure. Yup, the line was uncovered for half it's length, "to save weight aloft."

 

[Pilgrimtex]

I've made the Evans knot and don't care for it. I actually took it apart and still have the shackle with the two spliced loops. I did not feel it was up to the the task and didn't like the the wrap around the base.
This is just my opinion.
The reason the Diamond is not as strong is in the thickness of the neck.
If someone has the equipment to test my knot I would love to know the results. For now my knot's strength is theoretical based on the data from the button knot's neck thickness.

 

[colemj]

Untreated dyneema retains 60% strength after 5 yrs in extreme sun conditions like Arizona, New Mexico. If a concern go up one size. Dyneema lifelines should be replaced after 8 yrs as a rule.

Or just replace the shackle every couple of years - $1 worth of line and 15min of time.

In our applications, the shackles are way stronger than necessary just because the dyneema would be too small to easily work with if sized for the loads. Probably many applications on most boats are this way.

Scary how many quality SS shackles we have had fail or about to fail after 5yrs...

Mark

 

[colemj]

That will be a piece of cake and not much of a test for a 1/4" soft shackle. We have been anchoring our 40' (heavy) catamaran on a 3/16" soft shackle for a full year now. A couple of 50kt blows and heavy fetch, as well as 30kts for weeks and it looks like new. Being a catamaran, we anchor in shallow water and the shackle spends much of its time dragging around in sand and rubble. Still looks like new.

Mark

 

[Al Schober]

Just two comments: A) soft shackles are good things. B) learn the button knot. It's NOT that hard. Put the two fixed ends in a vise and work with the free ends.

 

[genec]

That will be a piece of cake and not much of a test for a 1/4" soft shackle. We have been anchoring our 40' (heavy) catamaran on a 3/16" soft shackle for a full year now. A couple of 50kt blows and heavy fetch, as well as 30kts for weeks and it looks like new. Being a catamaran, we anchor in shallow water and the shackle spends much of its time dragging around in sand and rubble. Still looks like new.

Mark

Wouldn't abrasion, in the case of using these shackles for some part of the anchoring system, be an issue?

 

[colemj]

Dyneema is more abrasion resistant than high carbon steel. One of its common usages is in chafe protectors for other rope types - also in cut and abrasion resistant gloves. Our shackles show no wear after a year of dragging through sand and rubble. If we regularly anchored in sharp rocks or coral (who would?), then I might have more concern. Even just cutting this stuff is tough to do - I keep a special ceramic knife for this purpose (cuts it like butter). A regular steel knife needs to be sawed back and forth and the dyneema often frays as it cuts.

But the thing to remember is that a soft shackle costs $1 and 15min of time. I keep several around and can just replace one at any sign of weakening, or just on a routine basis.

Mark