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Old 19-11-2019, 09:26   #106
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Re: HR shackles can explode

There’s many ways to splice a loop in Dyneema but this is the strongest and fastest and easiest for the win
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Old 19-11-2019, 09:44   #107
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Re: HR shackles can explode

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There’s many ways to splice a loop in Dyneema but this is the strongest and fastest and easiest for the win
yes, exactly. That's the best practice technique.

I do two very small things differently, but they are just preference and don't make a huge difference to tested strength.
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Old 19-11-2019, 22:45   #108
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Re: HR shackles can explode

Ok, here’s the first test, using the existing 12mm Dyneema core/Polyester cover line with the two Colligo Enhanced Static Lashing Blocks and the 5mm SK78 Dyneema loops double folded into 8 strand baskets.

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At the top I used an 8mm Dyneema soft shackle to attach to the running backstay toggle fitting (as this is temporary I didn’t want to hassle with putting the basket loop around the pin as I’ll do for the final solution).

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At the bottom I attached the basket loop directly to the 14mm bow shackle that’s in the chainplate. I used an 8mm Dyneema soft shackle to create the becket for the standing part of the purchase line. In the final solution I will eye splice the standing end into the block.

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The line is covered and has a fair bit of friction, so even when I fully tensioned the system the blocks still turned, despite the 4 strands pressing on each side of the rim.

Fully tensioned you can see that the basket loop at the bottom is twisted 90 degrees. I’m not sure if this is an issue. And the pin of the hard shackle is slightly off angle to the chainplate hole; also not sure if that’s a problem or not.

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Overall, seems easy to use the ESLBs as not-static. Maybe no need to strip the cover on the tensioned portion?

To test when static, I lashed the ESLBs in place and tensioned again. Still could apply full tension, but line noisy in the blocks and you can see they wanted to turn. If static, then needs the slipperiness of no cover.

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That’s the top block. Bottom one was similar.

Hmmm, some good thinking required about static vs dynamic. I’m leaning towards dynamic, acknowledging that it probably means more wear on the basket loops. Still, can cover them in Dyneema to mitigate.
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Old 19-11-2019, 22:47   #109
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Re: HR shackles can explode

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just FYI, just for your interest ....



It would be interesting to break test the full assembly, and see what goes first.. I have tested various size Antal and harken rings with various strops, but not colligo’s.


I’m going to break test the basket loops. I’m going to resplice one as a bury loop with lock stitching and leave the other with the Brummell lock. A local rigging shop will do the test.

Which one will go first? At what load? Stay tuned.
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Old 20-11-2019, 06:01   #110
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Re: HR shackles can explode

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Originally Posted by fxykty View Post
Ok, here’s the first test, using the existing 12mm Dyneema core/Polyester cover line with the two Colligo Enhanced Static Lashing Blocks and the 5mm SK78 Dyneema loops double folded into 8 strand baskets.

Attachment 203451

At the top I used an 8mm Dyneema soft shackle to attach to the running backstay toggle fitting (as this is temporary I didn’t want to hassle with putting the basket loop around the pin as I’ll do for the final solution).

Attachment 203452

At the bottom I attached the basket loop directly to the 14mm bow shackle that’s in the chainplate. I used an 8mm Dyneema soft shackle to create the becket for the standing part of the purchase line. In the final solution I will eye splice the standing end into the block.

Attachment 203453

The line is covered and has a fair bit of friction, so even when I fully tensioned the system the blocks still turned, despite the 4 strands pressing on each side of the rim.

Fully tensioned you can see that the basket loop at the bottom is twisted 90 degrees. I’m not sure if this is an issue. And the pin of the hard shackle is slightly off angle to the chainplate hole; also not sure if that’s a problem or not.

Attachment 203454

Overall, seems easy to use the ESLBs as not-static. Maybe no need to strip the cover on the tensioned portion?

To test when static, I lashed the ESLBs in place and tensioned again. Still could apply full tension, but line noisy in the blocks and you can see they wanted to turn. If static, then needs the slipperiness of no cover.

Attachment 203455

That’s the top block. Bottom one was similar.

Hmmm, some good thinking required about static vs dynamic. I’m leaning towards dynamic, acknowledging that it probably means more wear on the basket loops. Still, can cover them in Dyneema to mitigate.
The twisted loop and shackle: replace both by a single soft shackle. You can sand the metal plate to reduce chafing. I sometimes use a step drill bit to taper the hole, then finish with a Dremel drum sander.

On static vs dynamic: I would remove the cover from the Dyneema. Even if that stops the turning, it still means there is less friction than before. You can then reduce it further with a little block to keep the loop open
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Old 20-11-2019, 06:32   #111
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Re: HR shackles can explode

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Originally Posted by fxykty View Post
I’m going to break test the basket loops.
awesome.

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Originally Posted by s/v Jedi View Post
The twisted loop and shackle: replace both by a single soft shackle. You can sand the metal plate to reduce chafing.

I am guessing/hoping there is a stainless bushing in that toerail hole where the bow shackle goes? You would need to knock the bushing out to follow Jedi's suggestion - not hard to do, and his suggestion is a good one but it may involve more 'boat modification' than you want to do. If so, there is a pretty easy way to configure a lashing there to remove the twist.

Since it has not broken or deformed yet, it is probably not a huge issue.... but that shackle to toerail attachment is not totally 'proper' as is - I guess the hole is too big for the pin and it is point loading. If you leave the shackle it would be proper to bush down the hole (or upsize the shackle pin) so that it is a close fit thru the hole and thus not point loading.




On static vs dynamic: I would remove the cover from the Dyneema. Even if that stops the turning, it still means there is less friction than before.

yea, I would strip the cover also - less friction, lighter, less aero drag what's not to like. A very little less UV but not a huge amount less and if you coated the stripped portion with something like maxi-jacket it would be as good as the cover.
Nice job working thru this so far. I personally think I would have just gone for a Karver block but that would have been the easy/expensive solution (and you would still have had the toerail/shackle pin issue)
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Old 30-11-2019, 23:53   #112
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Re: HR shackles can explode

Almost done, still waiting for bushings to be fabricated that will fit over the shackle pin to fill the current chainplate hole. Also, once we re-rig and change the SS wire running backstays with Dyneema, the running backstay will be spliced directly through the upper Colligo blocks in the same way as the standing part of the purchase is spliced to the lower block.

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Upper block is attached to the bottom of the running backstay, to a toggle fitting. The block needs a shackle as the space in the toggle pin was not enough for the ends of the basket loop. 10mm HR is good enough for now (no open ocean passages before the re-rig).

Lower block is attached to the 14mm 316 SS bow shackle fitted through the chainplate hole.

I’ve covered each of the the basket loops and the eye splices with Dyneema cover, all four strands together and sewn whippings holding the ends of the cover. I haven’t installed spacers like the Ropeye or Ino-Rope blocks have got as I want to see how it works without first. No need to complicate if not necessary.

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I stripped the cover from the purchase line just for the section under load in the purchase. The
Dyneema core slips easily on the large diameter Colligo blocks - even under full load there is no sound from the system and no apparent extra friction relative to the Harken Air Blocks with roller bearings that were there before.

First test was today, sailing to windward in 25 knots and a 2m wind chop. We were double reefed main and full jib and ran full tension on the running backstays. Given the failures of the previous gear we put about 1500kg of winch tension through the 2:1 purchase - that’s pretty much full strength on a 10” handle on a 53 ratio winch. Winding in the running backstays was completely smooth. The Dyneema core slid on the blocks, which were held tight by the basket loops and spliced eye. There’s only about 20cm of line movement out of the bottom block from the time tension starts through to not being able to wind more on.

So far, so good.

Simple and reliable system with easily inspected parts, and costing about 20% of the equivalent roller bearing blocks.

Still waiting for the break test - hopefully this coming week it will be done. Meanwhile, all my basket loops started with a Brummel locked loop and 60x bury.
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Old 01-12-2019, 01:29   #113
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Re: HR shackles can explode

That just looks sexy! Good job


Matt
Quote:
Originally Posted by fxykty View Post
Almost done, still waiting for bushings to be fabricated that will fit over the shackle pin to fill the current chainplate hole. Also, once we re-rig and change the SS wire running backstays with Dyneema, the running backstay will be spliced directly through the upper Colligo blocks in the same way as the standing part of the purchase is spliced to the lower block.

Attachment 204131

Upper block is attached to the bottom of the running backstay, to a toggle fitting. The block needs a shackle as the space in the toggle pin was not enough for the ends of the basket loop. 10mm HR is good enough for now (no open ocean passages before the re-rig).

Lower block is attached to the 14mm 316 SS bow shackle fitted through the chainplate hole.

I’ve covered each of the the basket loops and the eye splices with Dyneema cover, all four strands together and sewn whippings holding the ends of the cover. I haven’t installed spacers like the Ropeye or Ino-Rope blocks have got as I want to see how it works without first. No need to complicate if not necessary.

Attachment 204132

I stripped the cover from the purchase line just for the section under load in the purchase. The
Dyneema core slips easily on the large diameter Colligo blocks - even under full load there is no sound from the system and no apparent extra friction relative to the Harken Air Blocks with roller bearings that were there before.

First test was today, sailing to windward in 25 knots and a 2m wind chop. We were double reefed main and full jib and ran full tension on the running backstays. Given the failures of the previous gear we put about 1500kg of winch tension through the 2:1 purchase - that’s pretty much full strength on a 10” handle on a 53 ratio winch. Winding in the running backstays was completely smooth. The Dyneema core slid on the blocks, which were held tight by the basket loops and spliced eye. There’s only about 20cm of line movement out of the bottom block from the time tension starts through to not being able to wind more on.

So far, so good.

Simple and reliable system with easily inspected parts, and costing about 20% of the equivalent roller bearing blocks.

Still waiting for the break test - hopefully this coming week it will be done. Meanwhile, all my basket loops started with a Brummel locked loop and 60x bury.
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Old 01-12-2019, 01:40   #114
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Re: HR shackles can explode

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That just looks sexy! Good job


Matt
Yes, nice to see these developments on CruisersForum
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Old 15-12-2019, 17:08   #115
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Re: HR shackles can explode

Had a call from the rigger who break-tested my loops. I don’t have photos yet but here are the numbers. I used 5mm SK78 Dyneema, which has a breaking strength of 2800kg, to make the loops.

Each loop was pulled to break as a loop, so the load was distributed over two strands. Nominal strength should be 5600kg. Is adding each strand’s breaking strength the correct calculation for loop strength?

Loop A, with Brummel locked end for end splice (tails turn 180 degrees in the splice before getting buried, no lock stitching). Broke at 2168kg. This is 38% of the loop nominal strength.

Loop B, with cross over end for end splice (lock stitched). Broke at 3408kg. This is 61% of the loop nominal strength and over 50% better than the Brummel lock splice.

Both of these figures are quite a bit worse than I expected. Sigh.

I’m using the loops in a basket configuration, with 4 strands per side, eight strands total.
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Can I extrapolate the break figures to allow for the additional strands, less a fudge factor of -30% to allow for unequally weighted strands? This would yield 6070kg (8672kg -30%) for the Brummel lock version and 9542kg (13,632kg -30%) for the cross over version. For my running backstays either one of these is sufficient.
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Old 15-12-2019, 17:43   #116
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Re: HR shackles can explode

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Is adding each strand’s breaking strength the correct calculation for loop strength?

For a nicely spliced loop in bare dyneema over smooth surfaces with decent radius I normally budget 190-195% of line strength (eg a 5% ish loss vs 200% two legs full strength). For a basket loop, with 4 legs holding load, I normally budget 340-360% of line strength (eg a 15% ish loss vs 400% four leg full strength). And as I mentioned above for an 8 leg, around a 30% loss.

Loop A, with Brummel locked end for end splice (tails turn 180 degrees in the splice before getting buried, no lock stitching). Broke at 2168kg. This is 38% of the loop nominal strength.

Loop B, with cross over end for end splice (lock stitched). Broke at 3408kg. This is 61% of the loop nominal strength and over 50% better than the Brummel lock splice.

Im not surprised at the 180-degree Brummel result - that is the 'knot level' result I expected; but the end to end splice is low -you should be able to do better than this, I would have expected 5000. Will be interested to see break pictures. And would be interested to know the diameter of the puller shackle/pins the rigger used. You can reduce the strength here by #1 pulling the lock stitching really tight (distorts the weave under load), #2 doing poor/short taper on bury - each of those can produce a 20% loss if really done poorly, and more like 2% if done nicely. And you can get up to a 50% loss if the puller pins/shackle are too small diameter.

Can I extrapolate the break figures to allow for the additional strands, less a fudge factor of -30% to allow for unequally weighted strands? This would yield 6070kg (8672kg -30%) for the Brummel lock version and 9542kg (13,632kg -30%) for the cross over version.

I would 'extrapolate' to 10k for the end to end version . . . . . ((3408/2)/.95)*8*.70 = 10k
nice job getting them tested - few people do that.
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Old 15-12-2019, 17:57   #117
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Re: HR shackles can explode

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nice job getting them tested - few people do that. btw there is a bunch of related material in my friction ring thread but it is a long read.

Thanks for your comments, very helpful. This has been an interesting process.

The end for end splice may have been weakened for both reasons you cite. I did pull the the lock stitching snug (I’m not familiar with lock stitching so this was my first attempt) and I tapered the last 30% of the buried tail.
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Old 15-12-2019, 21:57   #118
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Re: HR shackles can explode

Yes, thank you @Breaking Waves, this level of racing/technical knowledge is rarely seen here on the forum (although it's coming, step by step, as cruisers move to this type of equipment and techniques - and also maybe as old racers or performance sailors slow down and go cruising...).

And thank you to @fxykty too, for providing the real world practical examples, not just specs copied from a tech sheet.

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Old 16-12-2019, 06:51   #119
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Re: HR shackles can explode

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I tapered the last 30% of the buried tail.
30% is generally fine.

The highest 'leverage' (in terms of strength gain) area of the taper is the very tip and last couple cm.

Ideally, the tip will have been thinned down to one strand, and then that strand cut in half, and then that half fanned out and cut at a 45-degree angle (all this over about the last cm of the taper). You are ideally aiming for zero 'bump' here (between taper end and no taper start), any bump will produce a stress riser which reduces strength. In the real world, often, riggers are not so concerned with the last couple % of strength and they do a faster/dirty taper, but even then a tip wth 2 full strands with squared-off ends would generally be considered too coarse.

Dyneema is interesting to work with because (generally) it rewards doing the basics (don't disturb the weave, don't create stress risers, don't have bends, do have equal length legs) extremely carefully and penalizes sophisticated/complexity (generally things which 'should in theory' create extra strength but in actual practice make doing the basics more difficult). I was rather forcefully reminded of this principle in that LFR thread I linked above.

After you do a bit of sailing, I will be curious to hear how those Colligo rings work-out using the outer groove. People have been fussing around trying to accomplish that for a while with varying success. The Colligo system looks simple and elegant.
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Old 17-12-2019, 12:42   #120
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Re: HR shackles can explode

Here are the broken loops. Reminder, both loops were made from 5mm SK78 Dyneema with 72x buried tails with 30% one strand at a time taper. Nominal strength of the 5mm is 2800kg, so a loop should be 5600kg or a bit less for the splice say 5000kg. The machine used to break them has 19mm pins.

The first loop broke cleanly at the Brummel splice, which used two locks and had the tails turn 180 degrees, at 2168kg. Obviously a clear weak spot.
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Close up of the break. Very clean, right at the 180 degree bends out of the Brummel locks.
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The second loop also broke at the splice, but not cleanly, at 3428kg. Actually, one of the strands is still intact.
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This loop used a traditional cross over with lock stitching and it looks like I pulled the lock stitching too tight, given the bunching of the cover on one side of the break.
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For my purposes with the loops doubled over twice for eight strands total either option provides enough strength.

BW’s advice on doing these splices is spot on. They’re not difficult, but details matter.
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