Thinking of changing over to dynema shrouds on my 26-ft trailer sailer as it will reduce my rigging time considerably. At the moment I take the shrouds off every time just to stop them scratching the deck, the windows and generally being a pain. They are still a pain and are prone to kinking and twisting the lower terminals whilst raising the mast.
I'm wondering if I am over simplifying things or whether perhaps I could simply swap over to dynama by purchasing an upper t-terminal with a ring, one low friction doughnut ring and one shackle per shroud.
I know I will have to watch out for chafe but that is not too hard on a trailer sailer where you take the mast down after every sail.
I attach a couple of pictures of the relevant fittings and arrangement; part of the arrangement being a screenshot from the Free Range Sailing Youtube videos a couple of years ago when they re rigged a Clansman in Tasmania. I probably run a bit more tension in my shrouds than the (Masthead Rigged) Clansman as my rig depends entirely on the swept back shrouds for forestay tension.
I'm particularly interested in the arrangement for attachment to the chain plates as it appears that they use a shackle but then also a low friction ring above the shackle before the tensioning loops going to a second low friction ring all in turn before the actual shroud. It seems to me that the bottom low friction ring is redundant and one could simply use the shackle. I'm also unsure from the slightly fuzzy screenshot of the video whether the tensioning dynama loops go directly around the upper low friction ring which would result in almost a point load or if there is another c-shaped load spreading semi-circle facing downwards in which the turns of the tensioning dynema sit?
I will also have to sort something out to prevent chafe where the uppers go through a hole in the spreaders but I think that will be fairly straightforward.
Any and all comments gratefully appreciated.
Hi Jules,
My greatest fear of Dyneema rigging is if a spinnaker sheet or jib sheet gets caught or suddenly pulls hard against the shrouds, that it may chop straight through it if the point load and speed of the sheet exceeds the 145 degree melting point of Dyneema it could bring the mast down rather suddenly.
On my TS, the only wire rigging that seems to get slight kinks in it is the forestay, which can't be Dyneema for obvious reasons. I've learned to be careful in my prep for raising the mast so that the stays are pre positioned to not get caught or twist before raising the stick. With the 9.5m mast, raising solo, I get one shot at it without it causing problems so it's gotta be right.
I do use Dyneema in my backstay and am watching so see how it wears and behaves. It's different on a TS as upi know as they don't spend their life in the sun and on the water.
DM
Dyneema's on sale at RoadTechMarine also:
www.roadtechmarine.com.au/rtm-clearrance-sale-june-24/c/rtm-all-cs-jun24?utm_source=web&utm_medium=banners&utm_campaign=clearancejun24utm_content=csjun24
Jules I think what your looking at is a modern take on a deadeye. If The Lower shackle was to replace the low friction ring it would not be as low friction when used for tension adjustment, also has a tighter bend which maybe a stress point. I can't see any reason why you can't use rigging screws or whatever you already have to tension/adjust the proposed dyneema rig. At a guess I imagine each time you rig the boat there would be a stretch in time with the dyneema, where SS remains awkwardly stable
I use Dynex Dux on my little cat
I am a little dubious of its ability to not stretch every time we go out. Maybe it is me, but it seems less stiff than SS wire.
I have the same T ball ends in the mast. I use sailmakers thimbles and a shackle at the base.
Oh and turnbuckles don't seem to work that well on Dux. The amount of stretch is more than turnbuckles can handle on my little thing.
I tried dynema as halyards about 10 years ago. Because I read about it being stronger than steel for the same weight etc.
Unless its a better material now I found it did stretch. And it was impossible to fasten it in any way I could find with spices / knots etc.
My tests were simple - I put it the dynema length with the splice/knot I was testing between my two main sheet winches and cranked on the winches a few times. It always visibly stretched and I couldn't find a spice or knot that didn't eventually slip.
Maybe there's a really good way to secure it but I couldn't find it. Whereas Swages and wire were bullet proof.
Dyneema's great for the right application once you know how to splice it, but i wouldn't use it for standing rigging. i know people who've tried, and yes, it definitely stretches (too much) and is prone to failure at chafe points.
There are various ratings for dyneema the most common of which is probably sk78 but for standing rigging dm20 is necessary.
There is obviously also genuine licensed Dyneema from Europe or somewhere and Chinese stuff of unknown quality which may or may not decide to use the trademark Dyneema illegally.
Thanks for the comments everyone. I would ask those that say they experienced stretch whether they know if they used DM20 grade or perhaps whether it was just the more common sk78 which I have on my life lines on my larger boat.
I used Dux - the proper stuff - it works pretty well, but I feel that there may be some constitutional stretch every time I go sailing, which would not happen if the mast stayed up and the rig stayed stressed.
Select to expand quoteKankama said..
I used Dux - the proper stuff - it works pretty well, but I feel that there may be some constitutional stretch every time I go sailing, which would not happen if the mast stayed up and the rig stayed stressed.
The DUX specifications say it's sk75 with < 3% stretch or creep or whatever you want to call it whereas most places say use DM20 for standing rigging which has virtually no stretch or creep or at least is below 1%.
theriggingco.com/products-by-category/colligo-dux-dyneema/
The stuff RTM is currently selling branded Robline at 60% off appears to be genuine Dyneema made in Eastern Europe having a stretch of <0.7%. They get it from Ronstan and I'm currently awaiting a call back from the Ronstan technical guy.
You can of course upsize to avoid the problem but then you get windage.Bit confusing.
"It seems to me that the bottom low friction ring is redundant and one could simply use the shackle."
I watched the Free Range Sailing refit. From memory, I'm pretty sure they used the two low friction rings so they could re-tension the shrouds at sea using the Frapping (is that the right word?). Turnbuckles don't have enough travel in them. As others have pointed out, the dyneema will creep (permanently stretch under load) though it will stabilize after its initial creep (according to the internet). Using it on a TS would be an interesting experiment, but you might get tired of adjusting the stays for creep every time you raised the mast. My Cygnet has SS shrouds and an SS forestay, but it is a really simple gaff rig. It is designed for convenience, which suits SS, as you know everything will stay the right length every time you raise and lower the rig.
I have stainless rigging on my TS. I have worked out ways to stop the rigging rubbing on the fibreglass when the mast is down/towing etc. I would be reluctant to remove rigging each time as l would be worried it introduces opportunities for error. Not to mention the time. Having said that a positive might be the extra attention you give the rig when removing installing it each time.
Nothing against dyneema. I use it for the keel cable and its a no brainer.
Thanks for that Jules - that is a bit of a bugger if I got the wrong stuff, I can't remember but I think I got it from Stron rope in Sydney. I thought DUX was the Dux nuts.
So what you are saying is that the Road Tech stuff would be way better than what I have now. It is pretty cheap and I could knock up some replacement stays for not too much money or time. The Dux can be re-used on the big boat as steering cables. My veclock ones are 22 years old and should really be replaced, not that they did anything wrong.
So what do you think I should do Jules?
Ok so the tech guy from Ronstan (who are the agents for the dyneema that is sold at RTM) rang this morning and I had a good discussion with him and he also sent me some tech information. He definitely sounded like he knew what he was talking about and named a few well-known racing boats as well as foiling moths etc that use dyneema.
According to him DM20 which seems to be recommended at various places on the internet as the standard to use for standing rigging is an old standard and has largely been replaced by the sk.. ratings.
As far as the sk ratings are concerned sk78 is better than sk 75 but the Rolls Royce is sk99 which is currently used by various racing personalities and classes that he rattled off to me. The stuff that is stocked by RTM is sk78 and he said that was a big improvement over sk75 and may well suffice.
The sk78 currently on sale at RTM is said to be less than 0.7% creep but I'm not exactly sure what that translates to in real life. If you read up on creep a more precise definition of creep talks about a certain percentage of creep per 10% of breaking strain. I wonder therefore whether the point zero seven percent is for the first 10% of breaking strain (and therefore if the 25% of breaking strain that I believe is recommended when using Loos tensioning equipment) is more realistic does this translate to 1.75% stretch. All of this of course is for the unadulterated line itself and not the splice which would obviously take quite some time to bed in.
The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning in the first few sails but he wasn't too keen on that idea which presumably subjects the material to tighter point loads and tighter bends. That's all I used on my lifelines which are now three years old on my big boat. On a trailer sailer mind you I'm wondering if that really matters when you can inspect it every sail and can upsize the line a bit without creating undue windage.
I'm not looking at particularly long lengths so if I'm going to go to the trouble I will definitely get the sk99 which is not normaly stocked at RTM but they can get it if a whole roll is purchased. Presumably that won't be 60% off.
Creep will be an enormous pain in the arse with standing rigging so I want to avoid it.
Select to expand quoteKankama said..
Thanks for that Jules - that is a bit of a bugger if I got the wrong stuff, I can't remember but I think I got it from Stron rope in Sydney. I thought DUX was the Dux nuts.
So what you are saying is that the Road Tech stuff would be way better than what I have now. It is pretty cheap and I could knock up some replacement stays for not too much money or time. The Dux can be re-used on the big boat as steering cables. My veclock ones are 22 years old and should really be replaced, not that they did anything wrong.
So what do you think I should do Jules?
By the sounds of my information from Ronstan this morning (see my above post) it sounds like you could benefit from sk99. I haven't checked prices yet but on a small boat with narrow diameters if you don't want a lot then presumably it won't be prohibitive.
Thanks Jules
At that price I think I could do two things - I could increase the diameter of the stays on my little cat. At the moment it is 5 or 6 but for that money I could increase everything to 8mm. Then I also get the benefit of reduced creep from the DM20. Bugger about the 3% of the dux. I guess I confused the increased strength of the Dux with increased stiffness. (Reduced creep)
The Brummel splices are not hard to do so I would do the splices. I think it is very important to taper the splices properly. Although a locking brummel looks like it should hold in its own it won't at a high enough load. I am thinking of stitching the splice a fair way along its length to help keep it in the same position. This guy has some great videos on breaking splices and other joins in hight tech rope. Well worth a look. And read the top comment from a guy at Marlow ropes
Select to expand quoteKankama said..
Thanks Jules
At that price I think I could do two things - I could increase the diameter of the stays on my little cat. At the moment it is 5 or 6 but for that money I could increase everything to 8mm. Then I also get the benefit of reduced creep from the DM20. Bugger about the 3% of the dux. I guess I confused the increased strength of the Dux with increased stiffness. (Reduced creep)
The Brummel splices are not hard to do so I would do the splices. I think it is very important to taper the splices properly. Although a locking brummel looks like it should hold in its own it won't at a high enough load. I am thinking of stitching the splice a fair way along its length to help keep it in the same position. This guy has some great videos on breaking splices and other joins in hight tech rope. Well worth a look. And read the top comment from a guy at Marlow ropes
cheers
Phil
Thanks Phil
When talking about creep it's interesting to just run the percentages because 1% creep, which sounds very little, amounts to 70 millimeters on a short seven meter run which is clearly way too much for a shroud. Obviously on bigger yachts the problem is much more severe. Again however we don't even know the standard of measurement of the creep that manufacturers are referring to. ie Is that 10% load or 30% load?
Regardless it looks like sk99 is the go and upsizing can only help the creep issue.
Despite all the exhortations to the contrary this little test and the comments to this video are interesting as well.
"The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning "
Please be very very careful knotting dyneema where is is subject to loads as it is very slippery stuff and will not hold a knot aside from perhaps a buntline hitch which is recommended. Definitely not a bowline . It was only last month that as has been the case in the last seven years I had the 6mm double braid Polyester/. dyneema keel rope replaced with the antifoul. A new guy stripped off the Poly and knotted the dyneema . It gave way when the 250 kg. Keel jolted out of the keel box first time. The outer poly gives the knot grip .
Select to expand quoteBananabender said..
"The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning "
Please be very very careful knotting dyneema where is is subject to loads as it is very slippery stuff and will not hold a knot aside from perhaps a buntline hitch which is recommended. Definitely not a bowline . It was only last month that as has been the case in the last seven years I had the 6mm double braid Polyester/. dyneema keel rope replaced with the antifoul. A new guy stripped off the Poly and knotted the dyneema . It gave way when the 250 kg. Keel jolted out of the keel box first time. The outer poly gives the knot grip .
Thanks
Contrary to what the Ronstan guy told me seems that DM20 is not an outdated measurement according to the Marlow site anyway. See here:
www.marlowropes.com/innovation/dyneema-rope/dyneema-tech-info/
The stretch graphs are interesting as is the claim (if you expand the DM20 line by hitting the plus to the right of it) that DM20 has virtually zero stretch. Wonder if they achieve this by pre-stretch whilst heating as is discussed elsewhere on their page under this link.
I sell and work with Amsteel (Dyneema) in 3mm and 5mm, we also use SK99 dyneema in kitesurfing lines. Brumel splices work very well, and I always double Brumel, more for my own peace of mind than necessity as lives could be lost in our applications. It holds brilliantly and I've never had a splice break or slip. The amount of stretch as the splice beds in is significant, depending upon how long a tail you leave within the weave. It can be "worked out" to some degree but there is still significant settling as the loads apply.
I have used Dyneema for my life lines in the past but opted to go back to wire on my latest boat due to the abrasion at the stanchions with the Dyneema. I find it super easy to work with but creep is real and in kite bridles where we measure creep in millimeters, we always mirror replace lines on both sides of a kite for symmetry.
It is great stuff but I find it works in some applications better than others, so situational I guess. 
DM 
This is some work I've done with 1.5mm Dyneema for a customer. Factory sew the tail into their splice, mine is the lower splice in the pic.
Select to expand quoteBananabender said..
"The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning "
Please be very very careful knotting dyneema where is is subject to loads as it is very slippery stuff and will not hold a knot aside from perhaps a buntline hitch which is recommended. Definitely not a bowline . It was only last month that as has been the case in the last seven years I had the 6mm double braid Polyester/. dyneema keel rope replaced with the antifoul. A new guy stripped off the Poly and knotted the dyneema . It gave way when the 250 kg. Keel jolted out of the keel box first time. The outer poly gives the knot grip .Select to expand quotejulesmoto said..
Ok so the tech guy from Ronstan (who are the agents for the dyneema that is sold at RTM) rang this morning and I had a good discussion with him and he also sent me some tech information. He definitely sounded like he knew what he was talking about and named a few well-known racing boats as well as foiling moths etc that use dyneema.
According to him DM20 which seems to be recommended at various places on the internet as the standard to use for standing rigging is an old standard and has largely been replaced by the sk.. ratings.
As far as the sk ratings are concerned sk78 is better than sk 75 but the Rolls Royce is sk99 which is currently used by various racing personalities and classes that he rattled off to me. The stuff that is stocked by RTM is sk78 and he said that was a big improvement over sk75 and may well suffice.
The sk78 currently on sale at RTM is said to be less than 0.7% creep but I'm not exactly sure what that translates to in real life. If you read up on creep a more precise definition of creep talks about a certain percentage of creep per 10% of breaking strain. I wonder therefore whether the point zero seven percent is for the first 10% of breaking strain (and therefore if the 25% of breaking strain that I believe is recommended when using Loos tensioning equipment) is more realistic does this translate to 1.75% stretch. All of this of course is for the unadulterated line itself and not the splice which would obviously take quite some time to bed in.
The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning in the first few sails but he wasn't too keen on that idea which presumably subjects the material to tighter point loads and tighter bends. That's all I used on my lifelines which are now three years old on my big boat. On a trailer sailer mind you I'm wondering if that really matters when you can inspect it every sail and can upsize the line a bit without creating undue windage.
I'm not looking at particularly long lengths so if I'm going to go to the trouble I will definitely get the sk99 which is not normaly stocked at RTM but they can get it if a whole roll is purchased. Presumably that won't be 60% off.
Creep will be an enormous pain in the arse with standing rigging so I want to avoid it.
Its not too hard to take a brummel splice appart and shorten it up a bit, so thats an option if they end up too long. Ive also taken appart bury splices to replace chafe guard with no issues. This was on highly loaded sheets (Brindabellas jib sheets) so should work on trailer sailer rigging.
Select to expand quotejulesmoto said..
Despite all the exhortations to the contrary this little test and the comments to this video are interesting as well.
?si=ZygEX5vQNRKv7ph_
OK that video should be required viewing for those new (like me) to the subject.
Select to expand quoteJonE said..julesmoto said..
Despite all the exhortations to the contrary this little test and the comments to this video are interesting as well.
?si=ZygEX5vQNRKv7ph_
OK that video should be required viewing for those new (like me) to the subject.
And then you watch this example one. Not impressed with tying bowline behind back either. We used to practice tying bowline one handed in the dark for when changing headsail on a pitching deck in the dark .
www.sailingchandlery.com/blogs/hints-and-tips/dont-tie-bowlines-in-dyneema-rope
I quoted the wrong video! I meant the one about tapers. Looks like the sins to avoid, in order, are:
1. Tail too short - this was actually quite stunning how easily the brummel failed.
2. Eye too tight -didn't know about this.
3. Not tapering.
Looks like I'm going to be buying some more bloody dyneema to re-do some strings.
Select to expand quoteJonE said..
I quoted the wrong video! I meant the one about tapers. Looks like the sins to avoid, in order, are:
1. Tail too short - this was actually quite stunning how easily the brummel failed.
2. Eye too tight -didn't know about this.
3. Not tapering.
Looks like I'm going to be buying some more bloody dyneema to re-do some strings.
This video is excellent as are the comments including the one from the Marlow guy.
Select to expand quotejulesmoto said..
Ok so the tech guy from Ronstan (who are the agents for the dyneema that is sold at RTM) rang this morning and I had a good discussion with him and he also sent me some tech information. He definitely sounded like he knew what he was talking about and named a few well-known racing boats as well as foiling moths etc that use dyneema.
According to him DM20 which seems to be recommended at various places on the internet as the standard to use for standing rigging is an old standard and has largely been replaced by the sk.. ratings.
As far as the sk ratings are concerned sk78 is better than sk 75 but the Rolls Royce is sk99 which is currently used by various racing personalities and classes that he rattled off to me. The stuff that is stocked by RTM is sk78 and he said that was a big improvement over sk75 and may well suffice.
The sk78 currently on sale at RTM is said to be less than 0.7% creep but I'm not exactly sure what that translates to in real life. If you read up on creep a more precise definition of creep talks about a certain percentage of creep per 10% of breaking strain. I wonder therefore whether the point zero seven percent is for the first 10% of breaking strain (and therefore if the 25% of breaking strain that I believe is recommended when using Loos tensioning equipment) is more realistic does this translate to 1.75% stretch. All of this of course is for the unadulterated line itself and not the splice which would obviously take quite some time to bed in.
The thought occurs to just use a bowline rather than a splice to avoid constant re-tentioning in the first few sails but he wasn't too keen on that idea which presumably subjects the material to tighter point loads and tighter bends. That's all I used on my lifelines which are now three years old on my big boat. On a trailer sailer mind you I'm wondering if that really matters when you can inspect it every sail and can upsize the line a bit without creating undue windage.
I'm not looking at particularly long lengths so if I'm going to go to the trouble I will definitely get the sk99 which is not normaly stocked at RTM but they can get it if a whole roll is purchased. Presumably that won't be 60% off.
Creep will be an enormous pain in the arse with standing rigging so I want to avoid it.
Hi Julian, when I tried out dyneema for halyards bowlines were my first choice, since a lot easier than a splice. They slipped and loosened quite readily. If you can imagine tension on then tension off repetitively. The most success I had was an amateur standard (mine) splice and then impregnate the splice with epoxy.
With 3 and 4mm dyneena if you don't want to use a bowline a figure 8 loop saturated with epoxy would be a good alternative. Just a straight figure of 8 loop in 3mm does not seem to pull through.
Select to expand quoteRamona said..
With 3 and 4mm dyneena if you don't want to use a bowline a figure 8 loop saturated with epoxy would be a good alternative. Just a straight figure of 8 loop in 3mm does not seem to pull through.
It is interesting to hear that people are using knots in conjunction with epoxy.
I only use a figure eight knot as a stopper knot. Are there other uses for it? Most importantly in standing rigging? Also I think I would be using 5 mm for. standing rigging.
Actually I've done a lot of googling and I am getting rather annoyed at the accuracy of information about creep available for various brands. Marlow for example says that their DM20 should be used for standing rigging and that it has NO creep. When one looks at their own specifications however in the same document the creep is given as "less than 1%". 1% is a hell of a lot in standing rigging. Some people are claiming 0.7% for SK78 which is supposed to have more stretch than SK99 let alone dm20.
Furthermore a graph is necessary as 1% is meaningless unless it is given in relation to a percentage of breaking strain or safe working load or something AND that particular percentage happens to correspond with what you intend to use for your standing ringing.
