Dyneema brands, standing rigging, UV and chafe

[seandepagnier]

Originally Posted by s/v Jedi

The shackle isn’t more reliable than a chainplate.

Actually, it is. chainplates often fail, but shackles rarely do. Furthermore, the shackle can be a size larger and the weight difference is minimal compared to oversized chainplates.

I recommend a high strength low friction ring with the backstay spliced around the ring and each bottom leg splices through the ring. If the ring fails, everything stays connected because the eye splices are linked.

The ring will probably not fail as it is only in compression right?

Also, the line is weakened going through the ring like that because of the turn radius. Normally there are multiple lashings.

[fxykty]

Originally Posted by seandepagnier

Actually, it is. chainplates often fail, but shackles rarely do. Furthermore, the shackle can be a size larger and the weight difference is minimal compared to oversized chainplates.


The ring will probably not fail as it is only in compression right?

Also, the line is weakened going through the ring like that because of the turn radius. Normally there are multiple lashings.

Chain plates often fail? That statement needs factual support rather than some anecdotes. My own anecdote that chain plates don’t fail often is based on the fact that insurance rigging renewal standards don’t require chainplates to be changed with every rig change.

Regarding the LFR, it is in compression and can be upsized well beyond the working and break loads of the mast backstay fitting. Upsizing it will also provide larger bend radius for the two leg eyes - well beyond the 1:1 that is now accepted as full strength. I really don’t think you have to worry about the LFR causing any weak points in the system. With Dyneema sized for stretch the most likely weakest parts of your backstay will be the three points of attachment to the mast and hull.

[seandepagnier]

Originally Posted by fxykty

Chain plates often fail? That statement needs factual support rather than some anecdotes. My own anecdote that chain plates don’t fail often is based on the fact that insurance rigging renewal standards don’t require chainplates to be changed with every rig change.

I guess I stand by my point that it is lighter weight and cheaper to oversize a shackle than a chainplate. Shackles will bend a bit before failure, and chainplates are more susceptible to crevice corrosion being near the water and encounter salt water more, and often having one side not open to oxygen. I have read numerous accounts of chainplates failing.. but I will accept that the risk can be minimized, though and perhaps a valid argument is with the load shared on two, unlikely either will fail, and if one did, the other may fail immediately after, as well as not have sufficient tension anyway if the split is too wide.

Regarding the LFR, it is in compression and can be upsized well beyond the working and break loads of the mast backstay fitting. Upsizing it will also provide larger bend radius for the two leg eyes - well beyond the 1:1 that is now accepted as full strength. I really don’t think you have to worry about the LFR causing any weak points in the system. With Dyneema sized for stretch the most likely weakest parts of your backstay will be the three points of attachment to the mast and hull.

The 1:1 is "full strength" because it's actually 50% strength shared on two lines correct? Since the splices are 90%, this ends up not being the weak point anymore.. is this correct? It is not difficult to get 1:2 or slightly better here so it seems not an issue.

Ok, fair enough, but regardless there is no longer redundancy as if either leg of the split backstay fails it will release. I guess this is more likely from accidental chaffing than anything else? Would it not be better to make eye splices through the LFR for either leg instead? What about an oversize LFR that all 3 eye splices can share on the ring part and lashings going around the ring to secure them all? Maybe this is a bad idea?

[s/v Jedi]

Well, it’s simply not true. Shackles fail more often than chain plates and on serious boats, all chainplates are oversized appropriately.

The solution I proposed is solid and far superior to a shackle as single point of failure because even when the lfr would fail, which it won’t, all parts of the backstay would still be in place because the three splices are linked together.

Compare that to your proposal to have three eye splices with thimbles and shackle them together. You can’t keep a straight face claiming it is better

I have had multiple shackles fail, never a chainplate.

[Jim Cate]

I have had multiple shackles fail, never a chainplate.

Me too, Nick! In this case I think Sean is quite mistaken.

Jim

[seandepagnier]

Originally Posted by s/v Jedi

Well, it’s simply not true. Shackles fail more often than chain plates and on serious boats, all chainplates are oversized appropriately.

The solution I proposed is solid and far superior to a shackle as single point of failure because even when the lfr would fail, which it won’t, all parts of the backstay would still be in place because the three splices are linked together.

Compare that to your proposal to have three eye splices with thimbles and shackle them together. You can’t keep a straight face claiming it is better

I have had multiple shackles fail, never a chainplate.

I continue to ponder this an appreciate the feedback. Consider the heat treated dyneema is not intended to make the turn through the low friction ring.

I can't claim one way is better, its not so simple as that. You claim to oversize the chainplate. Have you checked the cost of even normal 316 metal? It is very expensive to oversize, and there is a large weight penalty. Do you know a good source for 316? It will cost me $200 plus shipping just to replace 4 chainplates. I can get titanium at this price as well, but the titanium fasteners are another $200. I dont think its advisable to use stainless fasteners in titanium is it?

I have seen a lot of cases of chain plates fail from crevice corrosion. How did your shackles fail?

What about an oversized ring and splice all 3 lines around the outside, then use lashings around the ring to seize them all? Would I need to fill the space inside the ring?

I agree the ring would not fail as it is in compression. I think the main issue is chafe through either leg which is more likely to occur at the deck level, and one of the main reasons for splitting the back stay is redundancy. With your proposal there is no longer any redundancy from one of the legs cutting through somehow, such as the lashings which are more vulnerable. I don't think it's reasonable to give up redundancy here but so far there is no obvious solution that doesn't have issues.

[s/v Jedi]

Originally Posted by seandepagnier

I continue to ponder this an appreciate the feedback. Consider the heat treated dyneema is not intended to make the turn through the low friction ring.

I can't claim one way is better, its not so simple as that. You claim to oversize the chainplate. Have you checked the cost of even normal 316 metal? It is very expensive to oversize, and there is a large weight penalty. Do you know a good source for 316? It will cost me $200 plus shipping just to replace 4 chainplates. I can get titanium at this price as well, but the titanium fasteners are another $200. I dont think its advisable to use stainless fasteners in titanium is it?

I have seen a lot of cases of chain plates fail from crevice corrosion. How did your shackles fail?

What about an oversized ring and splice all 3 lines around the outside, then use lashings around the ring to seize them all? Would I need to fill the space inside the ring?

I agree the ring would not fail as it is in compression. I think the main issue is chafe through either leg which is more likely to occur at the deck level, and one of the main reasons for splitting the back stay is redundancy. With your proposal there is no longer any redundancy from one of the legs cutting through somehow, such as the lashings which are more vulnerable. I don't think it's reasonable to give up redundancy here but so far there is no obvious solution that doesn't have issues.

No, you must have the wrong picture on my proposal because it has full redundancy, while your proposal has the shackle as single point of failure.

Have you seen the chainplates of a Sundeer 64?

[seandepagnier]

Originally Posted by s/v Jedi

The shackle isn’t more reliable than a chainplate. I recommend a high strength low friction ring with the backstay spliced around the ring and each bottom leg splices through the ring. If the ring fails, everything stays connected because the eye splices are linked.

I had thought you meant that the lower legs were both the same line passing through the ring.

To be clear, you are suggesting each leg has an eye splice through the ring? I dont see how the ring can fail in any case. Sorry for my confusion.. this does sound better.

[s/v Jedi]

Originally Posted by seandepagnier

I had thought you meant that the lower legs were both the same line passing through the ring.

To be clear, you are suggesting each leg has an eye splice through the ring? I dont see how the ring can fail in any case. Sorry for my confusion.. this does sound better.

From my comment #60:

I recommend a high strength low friction ring with the backstay spliced around the ring and each bottom leg splices through the ring. If the ring fails, everything stays connected because the eye splices are linked.

[seandepagnier]

the splices for each leg will have a tight turn radius unless it is a very large ring which has a higher cost. You claim 1:1 is enough but I would prefer at least 3:1

In any case, these low friction rings are also expensive... has anyone made their own?

[Benz]

Originally Posted by seandepagnier

the splices for each leg will have a tight turn radius unless it is a very large ring which has a higher cost. You claim 1:1 is enough but I would prefer at least 3:1

In any case, these low friction rings are also expensive... has anyone made their own?

It will cost you far more to make your own and anodize it than to pay for one. I've never paid more than $14 for an LFR--what exhorbitant prices are you seeing?

[s/v Jedi]

Originally Posted by seandepagnier

the splices for each leg will have a tight turn radius unless it is a very large ring which has a higher cost. You claim 1:1 is enough but I would prefer at least 3:1

In any case, these low friction rings are also expensive... has anyone made their own?

A 1:1 radius is used all the time (check soft shackle applications) and there are no problems reported.

I’m not sure on what kind/size boat we’re talking, but with this $45 ring you get 3:1 with 8mm Dyneema: https://www.velasailingsupply.com/an...rge-40-x-76mm/

[seandepagnier]

Originally Posted by Benz

It will cost you far more to make your own and anodize it than to pay for one. I've never paid more than $14 for an LFR--what exhorbitant prices are you seeing?

The idea is to take aluminum bar stock and turn it on a metal lathe. Once the ring is made, simply anodize it myself. See below, the price ($45 plus shipping) is quite high, though I believe there are alternative options for cheaper especially if 2:1 is acceptable.

Originally Posted by s/v Jedi

A 1:1 radius is used all the time (check soft shackle applications) and there are no problems reported.

What I found: " Calculation, Colligo experience, and PS testing all agree that an efficiency factor of about 1.4:1 is required to make up for inefficiencies and resist wear."

I also find people looping spliced dyneema through tangs with 0.5:1 and "no reported failure" and sticking dyneema through the hull and using a stopper knot instead of a chainplate. I also find people on youtube (free range sailing) pulling the low slip rings in tension on either side with no dyneema looping around it, depending on the aluminum itself not to fatigue in tension.. with no reported failures. Lots of people wrap the lashings around a shackle which also is outside of the recommended radius even by colligo 1.4:1 standards and they proudly report it as the correct method. I think because they are using line with 26500 breaking strength and it only needs to hold 2000 it's easy to blow away most of the safety factor and still have something that holds (for how long who knows)

I'm trying to avoid doing something like this and maybe in the process I end up saying stupid stuff here as I learn . I won't be planning do breaking tests myself.

I think the low slip ring is the way to go regardless.. thanks.

[Benz]

Originally Posted by seandepagnier

The idea is to take aluminum bar stock and turn it on a metal lathe. Once the ring is made, simply anodize it myself. See below, the price ($45 plus shipping) is quite high, though I believe there are alternative options for cheaper especially if 2:1 is acceptable.


What I found: " Calculation, Colligo experience, and PS testing all agree that an efficiency factor of about 1.4:1 is required to make up for inefficiencies and resist wear."

I also find people looping spliced dyneema through tangs with 0.5:1 and "no reported failure" and sticking dyneema through the hull and using a stopper knot instead of a chainplate. I also find people on youtube (free range sailing) pulling the low slip rings in tension on either side with no dyneema looping around it, depending on the aluminum itself not to fatigue in tension.. with no reported failures. Lots of people wrap the lashings around a shackle which also is outside of the recommended radius even by colligo 1.4:1 standards and they proudly report it as the correct method. I think because they are using line with 26500 breaking strength and it only needs to hold 2000 it's easy to blow away most of the safety factor and still have something that holds (for how long who knows)

I'm trying to avoid doing something like this and maybe in the process I end up saying stupid stuff here as I learn . I won't be planning do breaking tests myself.

I think the low slip ring is the way to go regardless.. thanks.

Sooo, you have access to bar stock, a lathe, and an anodizing bath? Then you should by all means make your own. Most of us can't get a suitable piece of bar stock bought and shipped for less than $45, and many of us don't have lathes at home, nor a metal bandsaw that big, and precious few of us have an anodizing bath. But yeah, if you have all those things handy already, it will be cheaper to make your own, especially if you don't value your time very highly.

Sorry--I hope I don't sound sarcastic. I just can't fathom it being cheaper to make a ring than to buy it unless one has a machine shop surrounded by free scraps and a good deal of free time to machine them.

[seandepagnier]

Originally Posted by Benz

Sooo, you have access to bar stock, a lathe, and an anodizing bath? Then you should by all means make your own. Most of us can't get a suitable piece of bar stock bought and shipped for less than $45, and many of us don't have lathes at home, nor a metal bandsaw that big, and precious few of us have an anodizing bath. But yeah, if you have all those things handy already, it will be cheaper to make your own, especially if you don't value your time very highly.

Sorry--I hope I don't sound sarcastic. I just can't fathom it being cheaper to make a ring than to buy it unless one has a machine shop surrounded by free scraps and a good deal of free time to machine them.

It just so happens I have access to a machine shop with a metal lathe, and a metal bandsaw as well as being surrounded by free scraps and a good deal of free time Even still it may not be worth the effort... I was curious if people made these for any tips.

Sorry.. my other friend has a metal lathe on his boat as well as lots of scrap metal... I've seen boats with drill presses, even washing machines! Of course even smaller boats often have 3d printers these days, though I limit myself to only one. Thought it was not that rare considering some people have scuba compressors, dish washers and tig welders on their boats.