Ropes for Single-Line Reefing. Dyneema?
- Thread starter DJE
- Start date
Birdseye
Well-Known Member
Neeves commented that
"The internal ropes on our Selden system were all 12mm - pretty massive, I'm not sure why they were so large. We replaced all of them with 10mm dyneema. We replaced all the external ropes with 10mm dyneema. In fact all our sheets and halyards are 10mm and we do not find them uncomfortable to work with. The 6mm dyneema, or any 6mm rope, is far too thin to work with by hand and needs tails, and we have found 10mm is fine. If we were doing it again - I'd consider everything with 6mm dyneema, it would be plenty strong enough, but have 10mm tails.
Our clutches (that took the original 12mm lines, work perfectly with the 10mm tails (I suspect the clutches might have been undersized to start with)."
Our experience was with replacing the wire halyards on a 36 footer with 10mm dynema sourced from EBay. The rope proved to be a bitch to splice because the cover was so tight but the job was done eventually. The rope itself is more difficult to handle being slippy so it takes extra winch turns and since our clutches were properly sized for the previous rope tails, the smaller dynema isnt always gripped that well if the load isnt heavy. In summary, a vaste improvement on the nasty wire rope halyards but our dynema isnt handling friendly. So chose your rope with care. It isnt all the same.
"The internal ropes on our Selden system were all 12mm - pretty massive, I'm not sure why they were so large. We replaced all of them with 10mm dyneema. We replaced all the external ropes with 10mm dyneema. In fact all our sheets and halyards are 10mm and we do not find them uncomfortable to work with. The 6mm dyneema, or any 6mm rope, is far too thin to work with by hand and needs tails, and we have found 10mm is fine. If we were doing it again - I'd consider everything with 6mm dyneema, it would be plenty strong enough, but have 10mm tails.
Our clutches (that took the original 12mm lines, work perfectly with the 10mm tails (I suspect the clutches might have been undersized to start with)."
Our experience was with replacing the wire halyards on a 36 footer with 10mm dynema sourced from EBay. The rope proved to be a bitch to splice because the cover was so tight but the job was done eventually. The rope itself is more difficult to handle being slippy so it takes extra winch turns and since our clutches were properly sized for the previous rope tails, the smaller dynema isnt always gripped that well if the load isnt heavy. In summary, a vaste improvement on the nasty wire rope halyards but our dynema isnt handling friendly. So chose your rope with care. It isnt all the same.
charles_reed
Well-Known Member
When I fitted single-line reefing I started out with UHMWPE, which has gradually extended to the leech lines on my two conventional reefs.
My main is 32m2, on a 31' boat - hence the need for 4 reefs.
Whilst the thinner, low hysteresis rope has reduced the amount of friction and effort used to put in the reef, by far the most significant improvement has come from replacing ordinary plain-bearing pulleys with carbon-filled, ball-bearing ones.
In practice, because the single-line reefing results in x4 the length of rope to the reef distance taken in, the limiting factor, for me, is the immense length of string you have to stow in the cockpit when you reef.
The rope diameter will be governed by the minimum size of rope your jammers will work on - I had to change mine when I came down from 10mm braid to 8mm UHMWPE, as the efficiency of a jammer drops dramatically with smaller rope.
In practice UHMWPE seems to have about twice the lifespan (I'm referring to high UV areas) of conventional polyester and it's gradually replacing all the halyards and control lines on my boat - TCO of UHMWPE is about 55% of using braid-on-braid polyester. Only spinnaker and genoa sheets left to replace.
I'd support Jonathan's comment about the relative discomfort of handling UHMWPE compared to polyester - the hard-racing variety is thoroughly unpleasant to handle, slips easily and is kink-prone - the softer cruising type does wear more quickly with jammers·
In its present form your question is a trifle too simplistic to answer.
Your graded reductions in frictional resistance will come in a) using very low friction blocks (I use Harken carboblocks), b) by minimising changes in direction of effort (lines not led back to the cockpit have about 30% of the friction) c) by using thinner rope. UHMWPE rope also has at least twice the lifespan of polyester braid on braid. Against this your jammers have to be far more efficient (I have to use Lewmar ring rather than simple jammers) and you need to have stowage space for the extra line with which you'll end up.
I use UHMWPE rather than the trade names of Dyneema or Spectra - one can find both on occasion at very competitive prices (especially in 100m lots from English Braids).
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Neeves
Well-Known Member
I've been cautioned against using dyneema for spinnaker halyards, not enough give (and possibly unnecessary anyway). In a big gust, on racing yachts, the lack of stretch has led to failures (edit - sorry do not recall what failed close edit) - that sudden shock load. Noting that on a serious racing yacht everything is minimalised and maybe failure is a result of underspecifying - an uncommon issue on most cruising yachts.
Sorry for drift - simply a caution, something to think about, to the previous post.
Jonathan
Sorry for drift - simply a caution, something to think about, to the previous post.
Jonathan
thinwater
Well-Known Member
Interestingly, I've been told that Dyneema is preferred for that application because less stretch = less movement = less chafe. I doubt that gusts are a factor--they don't come on that suddenly--but the shock load of a chute that has collapsed and then refilled is another matter, perhaps 10x over the working load, like and anchor chain snatching tight.
Of course, under specifying is almost certainly the main factor. Personally, if I ever fly the chute within 2% of the breaking strength of my halyard I'll probably wet myself.
Of course, under specifying is almost certainly the main factor. Personally, if I ever fly the chute within 2% of the breaking strength of my halyard I'll probably wet myself.
thinwater
Well-Known Member
I meant pictures of the specific installation. Sewing I get.
Daydream believer
Well-Known Member
The problem with reef lines is that chaffe in the same spot under load can be a nuisance & make changing dynema expensive
My main - about 33m2 on a 31 ft boat has 3 reefs & the first 2 are single line . never used the third reef but that is done on a 2 line basis for safety in event of a line break
Most important thing is friction & your ropes are far too thick
Next & most important is to dump all the in boom gubbins it does nothing for friction & can go wrong at a critical moment.
Single line reefing will work just as well without it on a sail size you are talking about
My main - about 33m2 on a 31 ft boat has 3 reefs & the first 2 are single line . never used the third reef but that is done on a 2 line basis for safety in event of a line break
Most important thing is friction & your ropes are far too thick
Next & most important is to dump all the in boom gubbins it does nothing for friction & can go wrong at a critical moment.
Single line reefing will work just as well without it on a sail size you are talking about
thinwater
Well-Known Member
Also (for polyester lines--it does not help as much with Dyneema) try Maxijacket by Yale. It reduces wear on docklines and such by 3-10 times. Honest, I've tested it side-by-side and on chafe machines. I would use it on a chafe-prone halyard or reefing line in a heartbeat. I've been using it on docklines and furler lines for years. Great on splices too.
There are rope companies that sell it in smaller cans than Yale.
There are rope companies that sell it in smaller cans than Yale.
bbg
Well-Known Member
If the chute is flying within 2% of the breaking strength of the halyard, the halyard is VERY light.
6 mm dyneema halyard would not be within about 10% of breaking strength for an 80 m spinnaker at 35 knots wind speed. I expect the kite would blow out before the halyard breaks.
Of course you could keep getting heavier kite material and heavier halyards until the failure point becomes the mast.
Woodlouse
Well-Known Member
Generally speaking the weak points for a kite are the sail and the pole. Unless there's quite severe chafe in the system I'd expect the halyard, guys and sheets to be the last things to break.If the chute is flying within 2% of the breaking strength of the halyard, the halyard is VERY light.
6 mm dyneema halyard would not be within about 10% of breaking strength for an 80 m spinnaker at 35 knots wind speed. I expect the kite would blow out before the halyard breaks.
Of course you could keep getting heavier kite material and heavier halyards until the failure point becomes the mast.
Neeves
Well-Known Member
I don't know why but in the back of my mind its the sheaves (clutch?) that might fail, though in my, expensive, experience you simply blow the spinnaker out starting at the head.
Jonathan
Jonathan
bbg
Well-Known Member
Mostly agreed. I would hope that the last thing to break would be the boat. And a long time before that, the mast.
thinwater
Well-Known Member
That isn't quite what I was worried about.
Daydream believer
Well-Known Member
One of our club squibs sank & was lost in a race this year, never to be seen again, when the spinnaker just pulled her over.
The crew could not release the cleats on the sheets or halyard. On my boat the halyard cleat gave up the ghost & all was saved, as the spinnaker was dropped in the drink
In most of my experience ( i used to do fore deck on racing boats) the biggest cause of breakage is chaffe. I have had a brand new sheet wear through on a shroud on a single 60 mile reach & halyards very close to failure a number of times because of the side ways pull on the mast sheave
The crew could not release the cleats on the sheets or halyard. On my boat the halyard cleat gave up the ghost & all was saved, as the spinnaker was dropped in the drink
In most of my experience ( i used to do fore deck on racing boats) the biggest cause of breakage is chaffe. I have had a brand new sheet wear through on a shroud on a single 60 mile reach & halyards very close to failure a number of times because of the side ways pull on the mast sheave
Woodlouse
Well-Known Member
The next weak point is most likely to be deck fittings. I'm not sure in this age of modern fibres whether I'd expect a rope to break before a rig, I guess it depends what the rope is attached to. It should be very difficult to compromise a hull though.
thinwater
Well-Known Member
I don't get this withing for breakage thing (or I may misunderstand). If your fittings are not strong enough to easily put the mast in the water, they are not NEARLY strong enough to withstand fatigue. Unless something is in terrible shape, there is always enough strength for a knockdown or pitchpole. For it to be otherwise is atrociously unsafe.
Bish
Member
Hi David, I’m having a new main fitted on our 391 tomorrow and I was considering reducing the single line reefing to 10 mm in an effort to minimize friction also. Just wondering where you landed with your project as when I tested 10 mm in my Lewmar clutch, it wouldn’t grip. Assume you have the same clutches?
DJE
Well-Known Member
In the end I got a rigger to do it. He put new sliders inside the boom and replaced all the rope with Cruising Dyneema. It is a bit better but still far from friction-free. We have now learned to live with it - we have a few marks on the reef lines so that we can pull them in to the correct position early when taking in a reef (which stops the tangles at the end of the boom). And if I can get to the end of the boom when shaking out a reef I pull through some slack to next mark before pulling up the sail. Otherwise it is just a matter of grab a winch handle, grunt and sweat! At least the reefs come down easily the work is in shaking them out - but the weight of the mainsail must be a significant factor.
(We have a new main too which can be flattened to delay the need for a reef.)
https://www.englishbraids.com/cruising-dyneema - But I don't know if you can get this in Australia!
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Bish
Member
Thanks for the update David. Yes my primary issue is having to go forward to pull out some slack when shaking out a reef I have so much friction in my system that there's no way I can winch it out with the halyard. I did note the other day that the rope inside the mast end of the boom has fuzzed up and swollen noticibly, that must be introducing a fair bit of friction.In the end I got a rigger to do it. He put new sliders inside the boom and replaced all the rope with Cruising Dyneema. It is a bit better but still far from friction-free. We have now learned to live with it - we have a few marks on the reef lines so that we can pull them in to the correct position early when taking in a reef (which stops the tangles at the end of the boom). And if I can get to the end of the boom when shaking out a reef I pull through some slack to next mark before pulling up the sail. Otherwise it is just a matter of grab a winch handle, grunt and sweat! At least the reefs come down easily the work is in shaking them out - but the weight of the mainsail must be a significant factor.
(We have a new main too which can be flattened to delay the need for a reef.)
Cruising Dyneema® - But I don't know if you can get this in Australia!
I'll pursue this further in the new year and replace the rope. I'm considering using Dyneema without a poly cover, I'm thinking that it should offer less friction- like this kind of thing: Dynamic Line. My backstay is made with this type of Dyneema and it's quite smooth and slippery to touch. As long as it works in a jammer, then it may be worth trying. I got a third reef built into this new main, so I need to install an extra run in the boom for that anyway. I'll do it all at the same time. Good idea putting some marks on the reef lines, I'll try that in the interim as an aid.
I've only had two short sails with the new main btw, but I love it. Finally I have a sail I can shape and control properly, the boat's pointing a lot better too.