New and improved double soft shackle

[allene]

This version double soft shackle is stronger, easier to make, and easier to use than previous versions. It also does not constrict the sheets. What is not to like?

The idea of the double soft shackle is that you can fasten it to the sheets ahead of time and then very quickly attach it to the clew ring. I have used them for sheets and for tack lines when I wanted a way to connect a line fast under race conditions. You can see in the second photo below that the large loop can be quickly put over the stopper knot where the slightest sheet load will close the loop securing the shackle.







The center knots are basically a double bowline and a tripple fisherman's knot. The stoppers are diamond knots. I tried many variations of the center knots, each variation being stronger than the previous.

My estimated breaking force for my 7/64 test version was 1,900 pounds based on the stretch of the 7/16 XLS line that went around the winch with a weight pulling on the winch handle. Sorry I am not more calibrated that that. The line is rated at 1,600 pounds but I had a test section of line in the setup and it did not break so the shackle is not as strong as the line it is made of.

I wrote up my work including instructions on how to make it on my web site http://L-36.com/soft_shackle_8.php

Allen

[Dan Lehman]

What is not to like?

Firstly, the knot misnomers : a fisherman's knot is an end-2-end joint
composed of opposing overhand hitches abutting and locking; and so the
nomenclature adds to this "double", "triple" where the components are, resp.,
double o.s, triple o.s --and in this scheme of things, you show but ONE
component, which is a quadruple overhand ; in fact, you've tied a strangle
knot (hitch) --and a triple strangle as the single contains one overwrap,
unlike the overhand. (Spare any WWWeb justification, this is older than that.)

Now, substantially vs. pedantically:
The complexity of making, and the breaking in the center knots.

Occam's Razor suggests that, since the right side of the presented structure
didn't break (i.e., the eye+diamond knot stopper), there need be no further
knotting to this! Simply pre-tie the line in this manner, to then loosen, reeve
the eye-end through the ring, and re-attach around the stopper's throat.
This makes a uniform four-strand connecting structure, not 2-vs-4 as shown
(where the break came in the knotted "2" side).

Beyond this admittedly *loose* simple structure of a ring of doubled HMPE
connected with eye+stopper, I can think of various other ways of much the
same sort of thing, with the same or similar finish, but with some added
engagement to reduce the *looseness*. E.g., putting a larkshead/girth hitch
around the sheets with the stopper knot centered in this, and then reeving
through the ring to bring the eye (perhaps merely the bight end) through
the sheets and then around the stopper.

--dl*
====

[allene]

Dan,

I am not completely following what you are saying but let me respond to what I think you are getting at. Clearly this is not a fisherman's knot but half of one with another knot. I think you may be pointing out that the combination has a name but I am not completely sure what you are saying. It was not my intention to invent a knot but rather to have something strong and tested.

As far as pre-tying and using a larkshead to attach the sheets, that was what my previous designs were. You can look up my older posts. Those designs had three shortcomings that this design solves. First is that they constrict the sheets which is a strength concern for the sheets. Second is that it is more difficult to attach than this design, although that is minor. But it turns out that this design is stronger by about 50%. With the larkshead the failure is at the larkshead and at a force about 2/3 the force that this design yields. With a smaller stopper loop, the failure would be at that end but with a larger size stopper, the failure moves to the larkshead.

Finally, of the three designs I have come up with, two use the larkshead to attach the sheets, and this one is the easiest to make, has the least shortcomings, and is strong.

If you go to the article I posted on my web site, you can see the other three designs that I have posted.

Allen

[Dan Lehman]

Originally Posted by allene

Dan,
I am not completely following what you are saying but let me respond to what I think you are getting at. Clearly this is not a fisherman's knot but half of one with another knot. I think you may be pointing out that the combination has a name but I am not completely sure what you are saying.

Yes, the "half" is a strangle --and one can attach "knot"/"binder" or "hitch" depending how much you want to advance some nomenclature : the knot is typically promoted for being tied around something to bind it (such as for whipping, where a multiple strangle can work quite well, in slick material!), but also tied around another strand as a securing of an end --lightly or heavily loaded (the "Barrel knot" is one name at used to denote a noose employing this).

A nice aspect of using "strangle" (which is a double overhand ) is that the modfiers "double", "triple", ... will match the visible "overwraps" that give it such security.
(Whereas, as I remarked, a "dbl.fish" has 1 overwrap, the triple, 2, and so on --mismatching.)
(So, for rockclimbers, who often use dbl./trpl., going with "Grapevine (bend)" which begins with strangle (single) components, one gets the nominal matching.)

As far as pre-tying and using a larkshead to attach the sheets, that was what my previous designs were. You can look up my older posts. Those designs had three shortcomings that this design solves. First is that they constrict the sheets which is a strength concern for the sheets. Second is that it is more difficult to attach than this design, although that is minor.

You seem to mistake what I'm recommending : simply have a single doubled-line structure in which you have at the fold-back point your "Brummel"ish small *eye*, and the two ends joined by the diamond knot or other stopper (Ashley's, e.g. ?) ; and so the use entails first loosening & separating the join of eye around stoppered end, and then reeving the eye through the clew and re-attaching it.
Which puts the nature of the connector the same as you have above --a twin line w/stopper being connected to the eye. At the clew end (well, this joint would be able to shift position, hitching to nothing), the twin line simply loops through it, knotless.

You have 2 twin-strands spanning the connection, with a turn around the clew and the sheets --no more/less compression than above (identical), and more material throughout than any of your designes (double the doubled strands).

But it turns out that this design is stronger by about 50%. With the larkshead the failure is at the larkshead and at a force about 2/3 the force that this design yields. With a smaller stopper loop, the failure would be at that end but with a larger size stopper, the failure moves to the larkshead.

But in your earlier design you have full load on the doubled line which forms the larkshead (oddly, in British climbing circles, this has become "larksfoot"!?), in contrast to having the doubled line essentially being stopper-connected to form a circle of twinned line --halving the load on any twin-lines part.


Now, I referred to my suggested structure as "loose", by which I mean that it isn't *hitched* in place; its only security is in the well-fit small eye choking the stoppered end, and I think that that's adequate (for loose jostling around ; certainly for full tension). If this is a concern, one can I think arrange for some more knotted structure to include a hitching of your connector to the sheets (this seems to be desired by you), and then one will again reeve the eye-end through the clew and bring it back to the sheets-end for ensnaring the stopper (which, e.g., could be positioned as the crossing arc of the larkshead --just to show an idea), perhaps preferably after doing some knotting or just turning through the sheets (thereby offloading some force before choking the stopper).

Working in such slick material as HMPE, though, takes some care in choosing a hitch (perhaps a *doubled* larkshead --i.e., where the "arcing" part is a full round turn, to try to give some frictional security-- ; sometimes called "bull hitch" (stronger than "cow")).
But, then, your systems --all-- seem to involve a pre-tied larkshead + stopper second piece of line on the clew, which I'd think is vulnerable to loosening and falling off! !?

As for constricting the sheets, I should think that their mere turning around the thinner twin strands of the HMPE connector would be as much damaging --maybe only showing on one spot vs more generally, but ... "weakest link", still. .:. minor difference, overall.

Cheers,
--dl*
====

[Dan Lehman]

AND ... , to present a further idea, though one that seems
to miss some of your design goals (in having connector at
clew only, and bringing the sheets to that, vs. having the
connector piece attached to the sheets initially, and all
being brought to the clew),

... consider you on-the-clew larkshead + stopper.
Make that longer, of adequate size (strength & length)
so that the attachment process is as follows:

1) reeve stopper end through the eyes of the sheets;

2) bring stopper back to the clew end;

3) loosen the larkshead (around clew);

4) reeve stopper end through clew (CAN this be done, always?!);

5) and now tuck the stopper out between the *center* of the
larkshead (i.e., between legs & between arcing part & clew),

6) and then cinch tight the larkshead to lock all.

Were the clew too small to receive the stopper, the stopper
could be just tucked out through the hitch directly --but then
the hitch is taking full load vs. half, though I think it might be
a little stronger so oriented.
(NB: there is no brummel'd eye in this.)

--dl*
====

[allene]

I am thinking you are suggesting something similar one of the variations I have on my web site but with the sheets where I show the pad-eye:


Let me clarify the application of the double soft shackle. The idea is that you have a jib out on a pole and a single sheet on the clew. You want to take the pole off, add a second sheet, and gybe. You are trying to attach a sheet to a sail that is already flying. You want to basically lasso the stopper knot that is attached (and stitched so it won't come off) to the clew. This needs to be a single hand exercise.

Another application is attaching a foot line to the tack. Again, you want something very fast. Because the shackle and eye are not bent, they do not have to be adjusted or milked around any curves.

These double soft shackles are very fast to attach. Faster than a standard stainless shackle. You cannot say that about anything you have to thread through the clew and put over the stopper knot.

Allen

[allene]

Originally Posted by Dan Lehman

in fact, you've tied a triple strangle ... hitch

Thank you Don, I have corrected my writeup to reflect that the knot is a tripple strangle hitch.

For your reference, here are the other double soft shackles designs I have posted both of which had problems solved by the design in this thread.



The problem with the above shackle is that it falls off the sheets if you don't hold it on. It also constricts the sheets although not as much as the design below.



Note that the one above with the fisherman's knot in the center would break the stopper knot that attaches to the ring. If a larger stopper knot is used to increase the strength, it breaks the shackle eye at the stopper knot. If an even larger stopper knot is used to increase the radius in the eye, then it breaks at the larkshead hitch. The largest issue I have with this design is the constriction of the sheet line.

And again, the easiest to make is the one in this thread because it is so well behaved when being tightened to lock the knots.

Allen

[Brion Toss]

Hi,
The good folks at New England Rope have sent me a length of their 12-strand Spectra, 5/16", to give to you for some destruction-testable shackle fabrication. Contact me at rigging@briontoss.com with an address to send the piece to, okay?
Fair leads,
Brion Toss