Knot in Lifesling bridle?

[k7cej]

My yacht club recently conducted Lifesling training based on the syllabus of The Sailing Foundation in Seattle. We chose to test our hoisting tackle at the dock but with a live, wet sailor. Even after two hours of classroom training, nobody got it exactly right the first time!

To review, the rig consists of 150' of 3/8" polypropylene braided line, one end tied to the boat and the other formed into a loop passing through the D-rings on the arms of the U-shaped buoy. The loop is supposed to be large enough so that after pulling the MOB up to the boat as high as possible and cleating the line off, a hoisting tackle can be shackled into the loop at the rail. Thus during hoisting, the standing part is unloaded and the loop acts like a sling; as the strain is taken, the ends of the buoy come together, holding the MOB even if unconscious.

My question relates to the knot used to tie the loop. To follow this you will need to see the picture:

The upper line is the standing part going to the boat; the two lower sections are the loop. The right-hand part ot the loop passes through the knot and is seized (stitched, in this case) to the left hand part of the loop. When the hoisting strain is on the loop, the knot can upset, putting 1/2 the load on the seizing. FWIW, during our practice the 5 Lifeslings were all rigged this way but the seizing were all different and two came mostly undone during the hoist.

Two questions:1. Does anyone know what kind of a knot this is?
2. What is the best way to rig this gear.

Inasmuch as I think this an inappropriate way to make the loop, I am looking at making a continuous loop with an end-for end splice, and tying the standing part to the loop with a double sheet bend (with the bitter end securely seized to the standing part. Since the lines all showed abrasion just from one hoist, I plan to use a more robust line for the loop like 12-strand Spectra or perhaps NER Flightline.

All comments appreciated.

[k7cej]

Sorry, but I misidentified the leads in the picture. The standing part is to the left, with the bitter end seized to it by stitching. The Lifesling loop is the upper line and the one to the left. I am still unhappy with the security of this setup during hoisting.

[Brion Toss]

Hello,
What they've done is a bizarrely upset Single Sheet Bend. Without intact stitching, the whole thing would come apart; with intact stitching the knot serves to keep the sling ends from pulling sideways on the stitches. You are right, it is not an appropriate arrangement, nor a durable one. What Lifesling appears to be counting on is that their product will not require much if any use.
As for alternatives, a Brummeled Spectra fork would not require a knot, and be much stronger. Spectra would still float. A better grade of Polypropylene, of the same configuration, would also be fine.
Meanwhile there are a lot of Lifeslings out there with this arrangement. Sooner or later, one of them will fail (if it hasn't happened already). Rescue equipment should be better than this.
Fair leads,
Brion Toss

[mikeb]

The two Lifeslings I have use "D" Rings that are stitched into webbing that goes around the person in the water under their arms and is part of the flotation - you hook into the D Rings with the Block and tackle to lift the person out of the water.

The floating line is not intended to be used as a lifting device but only to get the person up to the boat. Your floating retrieval line should be threaded through the D Rings.

Maybe Lifesling has changed the way it is built - I find that hard to believe on this part. The instructor should have know the proper use.

[k7cej]

The training syllabus from The Sailing Foundation (the inventors of the Lifesling) as well as their videos show the hoisting tackle being hooking into the loop of line connecting the D-rings. The reason is simple; after pulling the MOB as close up as possible by hand, the D-rings will still be about 1' above the water and out of reach from the deck of most boats. They recommend that the loop be of a size to just reach the rail.

After further thought, I have decided to make a continuous loop out of 1/4" spectra single-braid using a locked brummel and bury. I will then splice the retrieval line around this loop. This way, if one forgets to uncleat the towing line before starting the hoist (as 4 of 5 of our practice class did), one has a couple of feet of hoist before the fouling threatens to bust something.

It's one thing to know in theory how to do something, and entirely something else to actually do it correctly. To all of you out there with unused Lifeslings, I heartily recommend that you actually practice at least hoisting a wet body onto the deck. You may be surprised at how hard it is to get it right the first time.

[Dan Lehman]

Originally Posted by k7cej

The training syllabus from The Sailing Foundation (the inventors of the Lifesling) as well as their videos show the hoisting tackle being hooking into the loop of line connecting the D-rings. The reason is simple; after pulling the MOB as close up as possible by hand, the D-rings will still be about 1' above the water and out of reach from the deck of most boats. They recommend that the loop be of a size to just reach the rail.

And I apologize for only musing that ring-loading should be anticipated -- for
you said that exactly this loading is expected! (And above confirmed that.) And
it is this loading that has rendered the original Bowline into what surprised you.
But that was a Bowline with its tail most unfortunately stitched -- both in terms
of immediate performance and esp. with regard to this advice to size the eye
per rail-height from water level! (The tail should've been stitched to itself,
and thereby the size of the eye could be adjusted per boat (presumably one
won't be hollering "Wait a moment, don't go under yet, I'm adjusting the eye ... !").)

With a well-seized (both where and how strongly done) tail,
the Bowline will work -- it will become a Lapp Bend on ring-loading .
Though, hmmm, it might do some slipping on the hoisting; maybe that was
what motivated the peculiar stitching point -- to arrest this slippage of the
former S.Part, but at the expense of loading the stitching.

I'd prefer Ashley's #1029, which is an Overhand-based eye knot, the
tail brought through the Overhand's "spine" to turn around its "belly" and back
out the spine; this knot has good behavior in any loading. And the tail is
naturally well positioned for seizing (as is the Bowline's if taken to the right
part!). Or make the #1029 base a Dbl.Overhand (Strangle form), for greater
security. Were it laid line, one could just tuck the end a few times vs.
seizing.

Brion, you want a splice? -- for maximum strength? (This is over-rated; security, yeah.)
Have you tested eye splices by ring-loading them?! (I'm wincing at the thought.)

Frankly, I find the suggestion that one should somehow secure the tackle
to the eye baffling -- that eye that is bearing the MOB mass should be closed,
no?! As for hauling up someone unconscious, I'm wondering how that goes,
how the unconscious one manages to be into the device in the first place,
and all.
Or how far this rescue device can be thrown -- is it weighted?
curiouser & curiouser!

After further thought, I have decided to make a continuous loop out of 1/4" spectra single-braid using a locked brummel and bury. I will then splice the retrieval line around this loop.

Remember that this joint might be what needs to move through the D rings,
or which comes into contact with your spliced-to-sling eye (which sounds rather
unkind to the materials). Going out of your way with HMPE for a "stronger"
thinner(?) line might eat away at the strength of the attachment to it (small
diameter rope against rope)!?

To all of you out there with unused Lifeslings, I heartily recommend that you actually practice at least hoisting a wet body onto the deck. You may be surprised at how hard it is to get it right the first time.

I'm more inclined to recommend that the device's serious shortcomings --if they
come with the bowline stitched as was yours, and a regular vs. left-handed Bowline--
be brought to the attention of the USCG and maybe CPSCommision. Consider the
intended use, and : "two came mostly undone during the hoist." !!!

I heard long ago of some supposed Bowline failure for a climber rescue when his
tie-in was used qua sling, ring-loaded ; that struck me as something too far-fetched
for SAR folks to do, but maybe not. Here we see the same knot taken in the same
bone-headed way, with an end stitching that is appalling; and the USCG "approved it"
(money under the table, good ol' boy buddies at the bar doing business, or just some
pretty lax analysis ... ?).

--dl*
====

[Dan Lehman]

Originally Posted by Brion Toss

Hello,
What they've done is a bizarrely upset Single Sheet Bend.
Without intact stitching, the whole thing would come apart ...

Whoa! I'm surprised at this from you, Brion, for what they have is a bowline
caught in just the whiz-bang Overhand-noose tying method you've presented
in Rigger's Apprentice (p.65, Fig.3-24 (though, as your artist has it, sooo
snug an Overhand, it might not capsize)) ! Sheet bend? => Bowline, an eye knot.
If the stitching fails, this structure of PP should capsize into a Bowline, though with
no assurance that the capsizing stops at this point -- could flow (with loose collar)
into a Pile Hitch noose (as I've often seen, in trawler heavy mooring lines).

On the first (mis)description, it was a so-called Eskimo Bowline, similarly contorted
by the stitching.

As for alternatives, a Brummeled Spectra fork would not require a knot, and be much stronger.
Spectra would still float. A better grade of Polypropylene, of the same configuration, would also be fine.

But HMPE (is Spectra emerging again, vs. Dyneema --thought USMil. had consumed
the lot for vests, a rumor) is more costly, and I'm guessing that handling the line is
considered desireable -- think thickness. How can you critique the grade of PP?
Heck, first time I've seen it in 12-strand, anyway. (Looking over commercial-fishing
stuff, there seems a good bit of PP that is much better at UV resistance than much
of what is about more casually (I've got some black fat 1/4" laid stuff outside in
sometimes-sun for 5? years w/o much sign of degradation).)

One could simply tie the Bowline correctly/better. Make it Ashley's so-called "left-handed"
variety -- to better resist spilling if ring-loaded (all load in eye, knot essentially
joining ends, thus) -- and seize/stitch the tail to the right part, an eye leg. Alternatively,
make the "rabbit-goes-around-tree-&-back-into-hole" maneuver with the tail around the
S.Part-side leg of the eye, and then seize the the end to the S.Part (this gets you an
extra diameter in the central, nipping loop, for strength boost & security).

I think that this knot should be able to be *abnormally* loaded -- ring-loaded,
as I mentioned above, and any other way. No telling what some circumstance might
put on it in a rescue situation, snagging who-knows-what. And in this regard, splices
will be inferior to knots, I think -- they're directionally optimized.

In the meantime, if you feed some slack from the lower eye leg back into the knot
as shown, you should be able to capsize the structure into more recognizable form
of the Bowline; a seizing at the point that the tail exits the nipping loop should prevent
it from distorting into what you found.

--dl*
====

ps: "bitter end" : hmmm, this was originated allegedly to denote the "end"
of the line at the bitts, as opposed to the other end; that sense is degraded
by current usage wanting "the very end". Occam's Razor leaves "end"
to serve amply well here.

[Brion Toss]

Originally Posted by Dan Lehman

Whoa! I'm surprised at this from you, Brion, for what they have is a bowline
caught in just the whiz-bang Overhand-noose tying method you've presented
in Rigger's Apprentice (p.65, Fig.3-24

Of course a Bowline is structurally analogous to a Sheet Bend, with the former being a loop, and the latter a bend. When distinguishing between the two I look at how things are loaded. In this case, as I understand it, the part that goes up and the one that goes right connect out of frame at the harness, forming a loop. Hence, I think, your identifying the structure as a Bowline. But it wouldn't be, exactly, because what should be the standing part is going off to the harness. I was looking at it as a bend, thinking in terms of the stitching failing. Granted, it would also be a weird, side-loaded bend, so maybe we could call this a Bowline-like or Sheet Bend-like structure.




[/quote]But HMPE (is Spectra emerging again, vs. Dyneema --thought USMil. had consumed
the lot for vests, a rumor) is more costly, and I'm guessing that handling the line is
considered desireable -- think thickness. How can you critique the grade of PP?
Heck, first time I've seen it in 12-strand, anyway. (Looking over commercial-fishing
stuff, there seems a good bit of PP that is much better at UV resistance than much
of what is about more casually (I've got some black fat 1/4" laid stuff outside in
sometimes-sun for 5? years w/o much sign of degradation).)[/quote]

There are some polypro's I might trust here, but I've seen too many brittle bits on Life Slings. As someone pointed out above, the poly is not meant to pick the person out, but it should be able to, I think, or at least not part before the lifting line is attached...

[/quote]One could simply tie the Bowline correctly/better. Make it Ashley's so-called "left-handed"
variety -- to better resist spilling if ring-loaded (all load in eye, knot essentially
joining ends, thus) -- and seize/stitch the tail to the right part, an eye leg. Alternatively,
make the "rabbit-goes-around-tree-&-back-into-hole" maneuver with the tail around the
S.Part-side leg of the eye, and then seize the the end to the S.Part (this gets you an
extra diameter in the central, nipping loop, for strength boost & security).

I think that this knot should be able to be *abnormally* loaded -- ring-loaded,
as I mentioned above, and any other way. No telling what some circumstance might
put on it in a rescue situation, snagging who-knows-what. And in this regard, splices
will be inferior to knots, I think -- they're directionally optimized.[/quote]

I agree that there are a number of better ways to tie this knot, but I still would prefer a splice, partly because of maximum strength, but mostly because it doesn't matter how much load comes on which leg(s); capsize is impossible.

[/quote]ps: "bitter end" : hmmm, this was originated allegedly to denote the "end"
of the line at the bitts, as opposed to the other end; that sense is degraded
by current usage wanting "the very end". Occam's Razor leaves "end"
to serve amply well here.[/quote]

Oh, I don't know. It has been used as the end of a rode secured to a ringbolt in the chain locker, for instance, as well as the end that gets belayed to the bitts. I like the distinction, because it removes confusion about which end we are speaking of.
Thanks for the thought-provoking take on this, Dan.
Fair leads,
Brion