Soft shackles

[Ceirwan]

Thanks for the detailed reply. Sounds as if it might be worth looking at for my Hunter 490 - the loads aren't terribly high, half the shrouds are tensioned wit lanyards already and Dyneema stays would be much easier to store over winter.

For that type of vessel I would imagine they're ideal, especially if as you say you already tension with lanyards. It will be an easy job for you to change.

If you read this post:
http://forums.sailinganarchy.com/index.php?showtopic=168133&p=5090255

This guy got around the problem of getting the exact length of shroud correct by using lashings from the eye on the Dyneema, directly onto the bottle screws. That way he can also tension the rig much tighter.
He sailed single handed from the Netherlands to the UK this way so I guess its working well.

 

[nigelmercier]

Having now read the very interesting article, I'd like to understand the box at the foot of Page 25 where it says "Each tail was .... spliced into a loop ..."

 

[snooks]

Having now read the very interesting article, I'd like to understand the box at the foot of Page 25 where it says "Each tail was .... spliced into a loop ..."

If you have a look on page where it tells you how to tie the knot, you'll see I leave 28 cm of line to tie the diamond knot. Justin, from English Braids, tied the knot with considerably longer lengths of line, almost double in fact. The reason for this was so that he can splice a loop in each tail from the knot, after tying the knot, and then use the tensile test machine to tighten up the knot by threading the spliced loop in the shackle into one end, and the two spliced loops from knot end into the other end of the tensile test machine. 1/4 tonne load was then applied to tighen the knot.

After learning about this, I did my own variation by just tying the ends from the knot together into a loop, then applying tension with one of my yacht's winches, until the knot becomes small, very tight, and practically solid.

 

[vyv_cox]

A word on the splice, which provided you have a fid could not be easier. The end of the rope is simply led back through the hollow centre of itself for a length of around 6 - 9 inches to form a loop. This is remarkably strong, as Snooks says sufficient to pull heavy loads in the tensile tester. I know a successful racer of dinghy catamarans who uses Dyneema spinnaker sheets without shackles, splices them to the sail each time he rigs.

 

[nigelmercier]

Re: Soft shackles [Video]

Thanks Graham and Vyv, tension loops now understood. If I may now go back to how much line is required :

You'll need around 11in/28cm of tail to tie the knot in 5mm (so 22in/48cm of the total length) Less with thinner (3mm requires around half), more with thicker, then 2 x (1.4 x the loop circumference) ...

So the initial 28cm in Step [1] on Page 22 is for the knot, I assume leading to two 28cm lengths (A & B) in Step [1] on Page 23. So there is 48cm remaining (100 - 2*28), which divided by 2 (as doubled inside) then by π gives a diameter of 7cm, close enough to the 6mm to allow for the knot loop.

What I don't get is where 2*1.4 (presumably √2) comes into it?

 

[snooks]

Re: Soft shackles [Video]

Thanks Graham and Vyv, tension loops now understood. If I may now go back to how much line is required :

So the initial 28cm in Step [1] on Page 22 is for the knot, I assume leading to two 28cm lengths (A & B) in Step [1] on Page 23. So there is 48cm remaining (100 - 2*28), which divided by 2 (as doubled inside) then by π gives a diameter of 7cm, close enough to the 6mm to allow for the knot loop.

What I don't get is where 2*1.4 (presumably √2) comes into it?

OK I've worked out where I went wrong...DOH!

I said: "You'll need around 11in/28cm of tail to tie the knot in 5mm (so 22in/48cm of the total length)" this should have been 56cm leaving 44cm...but I actually used 52cm for my calculation.....

I did π x D = 6 x 3.14159 = 18.8

18.8 x 2 = 37.7

52 (the incorrect length left)/37.7= 1.37 which I rounded up to 1.4

HOWEVER

I actually had 44cm left (100 - (2 x 28))

π x D = 6 x 3.14159 = 18.8

18.8 x 2 = 37.7

44/37.7= 1.16

So for a 6cm ID I'd need to increase the length by 1.16

The increase is a 'safe' factor to increase the πD figure by to allow for: the loop around the line AND the reduction of length in the line length as the outer line expands to accommodate the line inside it. As you make larger loops the 1.2 decreases, but if you make smaller loops 1.4 works well.

I have a shackle in front of me with a 35mm ID which was made from an 86 cm length of (5mm) line – the shackle loop is made from 30cm of line.

3.5cm (D) x 3.14 (π) x 2 = 21.98cm or 10.99cm x 2

But I know it's taken 30 cm of line to make that.

30/21.98=1.36

My 1.2/1.4 was a rough ready-reckoner. My method in YM did away with the fine detail in order to encourage readers to give it a bash, without out the need for precise measurements or the need for buying fids etc.

If you want to be precise, l-36 has a calculator on their page: http://l-36.com/soft_shackle_howto.php

The eagle-eyed will notice they use shorter tails to tie their knot. I increased the length of the tails so they could be knotted together and pulled tight with a winch...because as we found out, the tighter the knot the stronger the shackle. :0)

Sorry for the confusion.

 

[GHA]

Re: Soft shackles [Video]

I just pinch a set of mole grips onto each tail, wrap it round the jaws and pull as hard as I can on each one. Might not set it all the way or reach full strength but seems to work OK, something else will break a long time before the soft shackle goes.

 

[vyv_cox]

Re: Soft shackles [Video]

I just pinch a set of mole grips onto each tail, wrap it round the jaws and pull as hard as I can on each one. Might not set it all the way or reach full strength but seems to work OK, something else will break a long time before the soft shackle goes.

That was pretty much what I did for the article but I then melted the tails off very close to the knot. In the tensile tester the ends were drawn into the knot, which collapsed upon itself, resulting in the poor failure load. Graham initially made his up the same way but left the tails longer, giving a far better failure load. Justin's shackle, tensioned to 1/4 ton, had twice the strength of mine even though the tails were cut off short.

 

[Kerenza]

Re: Soft shackles [Video]

I use 5mm vectran soft shackles with 6mm eyed and tapered sk 78 sheets on my racing 42ft. The outer cover is further covered at the winch position with 15mm soft braid stripped from old sheets, to make it easy to handle and grip in the winches. We also have bungee in the last 20 cm of the empty cover which has a toggled on it and is 40cm long. When the sheet goes over the pole, if set very high and gets tight, it self regulates at the first turning block and in an emergency will just let go. Not much sheet in the cockpit now.
All this is so simple to do with dyneema.
Our experience is don't use a single shackle on the clew. It's impossible to release the lazy sheet for any reason.

I have just replaced my rod rigging and of choice would have gone soft. Unfortunately it all came down to cost. Soft was three times thee price with standard rod terminals.

We use a low friction ring to bring the sheet in to the mast when necessary. All dyneema and controlled from the cockpit.

Long soft shackle to hold the sheet out at the toerail when necessary.

Dyneema Cunningham with soft eye.

Kite sheets and guys all 10mm dyneema for ease of handling with soft eyes, but still use quick release shackles (at massive cost) as soft shackles don't undoo quickly enough.

 

[nigelmercier]

Re: Soft shackles [Video]

OK I've worked out where I went wrong...DOH! ...

Thank you, although I'm still a little confused by "So for a 6cm ID I'd need to increase the length by 1.16" as I thought this was 6mm?

I wonder if using a diameter in trying to emulate a steel shackle is worthwhile anyway. Personally I would prefer to work with the circumference. It would also make more sense to me if this was marked out from the middle of the line, rather than measuring the knot from the end.

 

[jamieo]

Re: Soft shackles [Video]

I'd made a few of these myself with some dyneema I bought off eBay (pretty cheap) and using the instructions from http://l-36.com. With very little experience it was pretty easy, although I found a different you tube video that explained how to tie the diamond knot easier.

What I hadn't tried was using a winch to tighten the knot - something I'll give a go. Maybe I'll try splicing the two tails from the knot together to make a loop and then should be easy to pull the whole thing tight between two winches.

I did all of this with uncovered dyneema. I did buy a couple of lengths of covered dyneema to try and to also have a go at learning to splice it. But the cover is so dense, it's very hard to work your way through to get at the dyneema core. Any advice or tips?

Has everyone else been making soft shackles with uncovered dyneema?

Cheers,
Jamie

 

[snooks]

Re: Soft shackles [Video]

Thank you, although I'm still a little confused by "So for a 6cm ID I'd need to increase the length by 1.16" as I thought this was 6mm?

To make a shackle with a 6cm ID with 5mm Dyneema, I'd have to increase your required internal circumference by a ratio of 1.16 to allow for the shortening of the rope and the spliced loop before the knot, so for 6cm ID shackle the in 5mm line the length I'd need is:
Total line length = The length needed to tie the knots + the length to splice the shackle.

=-=-=-

The length needed to tie the knots = 28cm x 2
The length to splice the shackle = 2 x (diameter of shackle required x π x the ratio for the extra line)

Diameter of shackle required = 6cm
The ratio for the extra line = 1.16

=-=-=-

2 x 28cm + 2 x (6 x π x 1.16).

I wonder if using a diameter in trying to emulate a steel shackle is worthwhile anyway. Personally I would prefer to work with the circumference. It would also make more sense to me if this was marked out from the middle of the line, rather than measuring the knot from the end.

But unless you know how long the circumference is you won't know where the middle of the line is :0)

I measure 28cm, i.e. one length needed to tie the knot (and mark it), add on the circumference required multiplied by the ratio, then fold the line in half and cut the line where the first line finishes.

As commercial soft shackles were sold by diameter, it mades sense for us to follow suit.

 

[snooks]

Re: Soft shackles [Video]

I'd made a few of these myself with some dyneema I bought off eBay (pretty cheap) and using the instructions from http://l-36.com. With very little experience it was pretty easy, although I found a different you tube video that explained how to tie the diamond knot easier.

What I hadn't tried was using a winch to tighten the knot - something I'll give a go. Maybe I'll try splicing the two tails from the knot together to make a loop and then should be easy to pull the whole thing tight between two winches.

I did all of this with uncovered dyneema. I did buy a couple of lengths of covered dyneema to try and to also have a go at learning to splice it. But the cover is so dense, it's very hard to work your way through to get at the dyneema core. Any advice or tips?

Has everyone else been making soft shackles with uncovered dyneema?

Cheers,
Jamie

There is no strength in the braided casing of covered dyneema, so using uncovered is fine. If you wanted to cover the final shackle for more abrasion resistance you could use the braided casing from an off cut of 8-10mm braid on braid line.

If you want to winch them tight (which I'd recommend) watch the video in post #1, just before the end you'll see that just a single fisherman's knot (two overhand bends in each end) does the job admirably and uses a minimal amount of line. :0)

 

[jamieo]

Re: Soft shackles [Video]

There is no strength in the braided casing of covered dyneema, so using uncovered is fine. If you wanted to cover the final shackle for more abrasion resistance you could use the braided casing from an off cut of 8-10mm braid on braid line.

If you want to winch them tight (which I'd recommend) watch the video in post #1, just before the end you'll see that just a single fisherman's knot (two overhand bends in each end) does the job admirably and uses a minimal amount of line. :0)

Ok so take all the covering off the Dyneema that you use to make the schackle and later cover it with covering from a thicker line. Now I understand why it wasn't easy - stuffing 2 cores in a 5mm cover

 

[SimonD]

Re: Soft shackles [Video]

Soft shackles would seem to offer significant advantages in securing the pick up chain to a mooring buoy. Or am I missing something?

At present, I either have to obtain a length of 10mm chain and get a loop welded to one end. This allows the chain to be passed through the loop and the ring on the top of the mooring buoy (if you see what I mean). This does away with a shackle, but creates the need to find a welder.

The alternative is to shackle the chain to the buoy. However, the shackle looks pretty weedy, can come undone or simply rust away.

So, would a soft shackle (or even more than one) be a third way? Maybe pass the chain through the mooring buoy loop and secure it back on itself with a soft shackle or two?

 

[Seajet]

Re: Soft shackles [Video]

SimonD,

I don't quite see why you can't find the right size shackles for your pickup buoy - it may require two to suit buoy & chain - and as for undoing, all shackles on moorings should be thoroughly moused with ormiston wire or similar.

However pickup buoys shouldn't take any load - except on those brief occasions in strong winds / currents before the proper chain can be brought aboard and made off - so a simple bit of strong line tied - and the ends whipped secure - would do.

It is not completely unheard of for pickup buoys to be cut off though, for malice or theft reasons.

If however the pickup buoy may be likely to chafe in any way, on a drying mooring seabed or barnacles under the main buoy - if pickup wraps around it - then yet again the chafe resistance of steel schackles would be a benefit.

 

[bbg]

Re: Soft shackles [Video]

Although I believe soft shackles have their place, I do not think it would be appropriate in this application. No need for a soft shackle for something that will be permanently attached.

As Seajet says, either use a short piece of strong dyneema (I would splice it with a hard eye, not tie it - splicing dyneema is REALLY easy) rather than knots.

Or, better still, a properly moused shackle. That is not an application where the softness and weight savings of a soft shackle really offer any advantages.

 

[Birdseye]

How many of those already on youtube actually:

Test commercially available soft shackles?
Tested to find out which design of soft shackle is strongest?
Tested to find out which knot is strongest?
Tested the shackles they have made?
Tell you how to make the strongest soft shackle?

We have, and we do.

Good for you Snooks. I have made two of them following your video. In four attempts at the crown knot only one has come out looking right. I'm going wrong somewhere in the last two stages before you start tightening the knot but I'll be damned if |I can work out where.

Thanks anyway. Please do more of the same sort of thing. Ignore the know alls on here - they dont know much most of them.

 

[snooks]

Good for you Snooks. I have made two of them following your video. In four attempts at the crown knot only one has come out looking right. I'm going wrong somewhere in the last two stages before you start tightening the knot but I'll be damned if |I can work out where.

Thanks anyway. Please do more of the same sort of thing. Ignore the know alls on here - they dont know much most of them.

The bit where you may be coming unstuck is making sure the ends of the Carrick Bend pass around the outside of the legs of the splice in the direction that the lines are going around the knot. So if you look at the knot from the top, the ends continue around the outside of the knot in an anti-clockwise direction. These are steps 4/5/6 on pg 23 of the July issue.

Keep at it, before you know it you'll have a handful of them and you'll be replacing all the rattly metal ones :0)

 

[Birdseye]

Thanks Graham. Must have watched the video a dozen times but I still wasnt clear whether the two ends went round the outside in the same direction or in opposite directions.

Anyway I now have another problem . Having bought a second piece of 5mm dynema off Ebay ( where else) I cant for the life of me open it up enough to get the snake to swallow its tail so to speak. And the rope is quite sticky / non slippy.