Blue Wave Dyneema Terninals vs. Splice

[KP44]

Originally Posted by Breaking Waves

The question in play here is not the value of dyneema, but how you plan to/how best to attach it to the chain plates and mast.

You certainly don’t want to splice it directly to most chainplates and tangs, which have holes with sharp edges and very small D/d. And even most U bolts and pad eyes would have quite small D/d.

Most typical thimbles would crush under shroud/stay tension - if going thimble you really need a closed or solid one.

Good points. I have used stainless thimbles except a few non critical with nylon. No chafe yet and no stretch (after initial) and no sign of failure. But you're right about the need for excellent thimbles.

If I had known about dyneema, I certainly would have done my lifelines with dyneema rather than having new ones fabricated.

[witzgall]

Originally Posted by Breaking Waves

These terminals provide an alternative. They are not ideal. But they are both versatile and simple.

So I guess the question is, are they good enough, even if not the very best solution? Would it be good enough to replace the existing rigging with Dynemma terminated with these?

In my mind one of the biggest issues would be how to deal with stretch over time, if the only adjustment range is afforded by a traditional turnbuckle.

Chris

[Jim Cate]

Slight thread drift warning!

Whist reading this thread I began wondering if anyone has used a combination of dead eyes plus a rigging screw on shrouds? One would use the dead eyes to adjust the length of the shroud initially, not under load, so that the rigging screw was near its max extension. The rigging screw then is used to supply working preload to the shroud. If then creep or structural stretch exceeded the adjustment length of the screw, a simple adjustment at the dead eyes would "reset" the length and the screw would again supply the working tension.

The dead eyes could be simple and only involve a few parts because of not being adjusted under load. And in the situation where one is replacing wire rigging, the rigging screws are already there and strong enough for the job.

Jim

[model 10]

I found a broken wire in one shroud, made a replacement from Spectra and used a dead eye and a turnbuckle. I used the dead eye to get it as tight as possible by hand, then used the turnbuckle. It took several hundred miles to stay taught. There was still some thread left in the turnbuckle.

[fxykty]

Colligo doesn’t recommend dead eyes and lashings for larger boats (their website indicates around 40 feet), presumably for higher permanent tension. But I like the combination of dead eye and lashing plus turnbuckle for rough and fine tuning. That starts getting pretty tall though and increases the expense. Something to consider.

[unbusted67]

Originally Posted by Jim Cate

Slight thread drift warning!

Whist reading this thread I began wondering if anyone has used a combination of dead eyes plus a rigging screw on shrouds? One would use the dead eyes to adjust the length of the shroud initially, not under load, so that the rigging screw was near its max extension. The rigging screw then is used to supply working preload to the shroud. If then creep or structural stretch exceeded the adjustment length of the screw, a simple adjustment at the dead eyes would "reset" the length and the screw would again supply the working tension.

The dead eyes could be simple and only involve a few parts because of not being adjusted under load. And in the situation where one is replacing wire rigging, the rigging screws are already there and strong enough for the job.

Jim

I was thinking the same thing as a read this. Seems like the way to go.

[Breaking Waves]

Originally Posted by Jim Cate

combination of dead eyes plus a rigging screw on shrouds?

I don't see any real technical concern with that but it does add height and hardware. I might comment that terminating deadeye lashings properly with Dyneema is slightly tricky because of how slippery the material is - there are several approaches which work well but an unresearched DIYer might do something which 'looks good' but does not, in fact, hold solidly.

I guess I would say it is not really necessary, as you really should be able to make your shrouds so they are pre-stretched to the right length, right at the top of turnbuckles. That is not so hard if you are careful/precise. You then have the full turnbuckle to take care of creep, which should not be huge if you have sized the (dia of the) stays correctly.

The ability to prestretch repeatability to a decent load is a really useful component of DIY dyneema stays, which is often overlooked. There are I guess rather more 'got yua's' to DIY dyneema than DIY 1x19 w/staylocks - it's certaintly not rocket science but is easier to end up not quite perfect.

[Benz]

Originally Posted by Dockhead

But isn't the point of these, as someone else commented above, to easily integrate rope rigging with already existing rigging screws, forks, eyes, etc. which were provided for wire rigging? Seems elegant to me; a thimble would't actually work without other hardware, for this purpose.

Sorry for the delay in responding; I've been at sea for a couple days.
I guess they would fit the look better, especially if you already have wires swaged to a threaded turnbuckle stud. I don't think I would bother with them for a new construction--I'd just get a turnbuckle with a clevis on top that would fit a thimble.

[EEC]

Originally Posted by Jim Cate

Slight thread drift warning!

Whist reading this thread I began wondering if anyone has used a combination of dead eyes plus a rigging screw on shrouds? One would use the dead eyes to adjust the length of the shroud initially, not under load, so that the rigging screw was near its max extension. The rigging screw then is used to supply working preload to the shroud. If then creep or structural stretch exceeded the adjustment length of the screw, a simple adjustment at the dead eyes would "reset" the length and the screw would again supply the working tension.

The dead eyes could be simple and only involve a few parts because of not being adjusted under load. And in the situation where one is replacing wire rigging, the rigging screws are already there and strong enough for the job.

Jim

I did this on my back stay because it has a ssb antenna spliced into it, causing it to slowing stretch (not sure if you would call it creep?). Every couple months I tighten the turnbuckle a little bit and then after 2-3 times on the turnbuckle I slack the stay right off, re tighten the lashing and then I’m back at the top of my threads on the turnbuckle.

[gruffa]

Is it hard to re-splice a dyneema shroud that has stretched too much?

[gruffa]

Here's a pic from the Blue Wave brochure just for the basic rope eye terminal.
They also recommend the safe work loads not exceed 1/5 of the breaking loads listed.

[Benz]

Originally Posted by gruffa

Is it hard to re-splice a dyneema shroud that has stretched too much?

No, it's easy.

[ggray]

You are probably right about being easy, but I'll bet you will have to "lose" a good bit of length.

You would with any type braid, but I suspect dyneema more.

I end for ended a halyard I had made from Warpspeed (covered amsteel) and when I dissected the old eye splice, I was amazed with what I found. The amsteel that became the core of the splice had been so compressed by the amsteel surrounding it that the surface was rock hard and covered by sharp peaks from the inner surface of the braid. So I think a new splice would need to be made from line further from the old splice.

[Benz]

Originally Posted by ggray

You are probably right about being easy, but I'll bet you will have to "lose" a good bit of length.

You would with any type braid, but I suspect dyneema more.

I end for ended a halyard I had made from Warpspeed (covered amsteel) and when I dissected the old eye splice, I was amazed with what I found. The amsteel that became the core of the splice had been so compressed by the amsteel surrounding it that the surface was rock hard and covered by sharp peaks from the inner surface of the braid. So I think a new splice would need to be made from line further from the old splice.

Sorry I missed this earlier.....having an exchange with me is always slow motion
To your comment: being compressed doesn't affect the strength at all. Those sharp peaks are just where the bury got squished into the standing braid. I quite often unpick a pre-stretched splice and re-do it an inch or so further along and pre-stretch it again. The guys I work with, who've been experimenting with Dyneema since the 90's, haven't found this to be bad practice, and they've broken scores of samples of all sorts of stuff in all sorts of configurations overt the years.

[Breaking Waves]

Originally Posted by Benz

I quite often unpick a pre-stretched splice and re-do it an inch or so further along and pre-stretch it again.

You do 'clean' work, that helps The concern with this would be someone snagging/pulling/distorting strands/braid. That would effect strength. Would not matter so much in the bury portion, but if the standing portion of the splice got distorted it could be significant.

being compressed doesn't affect the strength at all.

Just to be a little more precise . . . the relatively low compression in a typical halyard splice will not affect effective strength. Halyards tend to be sized for stretch rather than strength, so operate at low % strength range.

But Dyneema is actually quite sensitive to compression, relative to other fibers. It is one of the major 'weaknesses' of the fiber (along with heat sensitivity) compared to other fibers. You just need a pretty decent compression force to see it - note than Samson has (apparently) seen compression damage on long term cow hitched tow line eyes.

breaking waves