Swallow Yachts Association
Swallow Yachts Forum => Technical => Topic started by: Craic on 15 Jan 2010, 14:06
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You may have heard already that the grey Dyneema plait is the new IN material for shrouds. As tough as steel but way lighter in weight. Doesn't stretch BTW, and doesn't scratch the paint or gelcoat while trailering.
The other benefit is that you can easily make the shrouds yourself while steel shrouds have to be ordered from and be made by a sailmaker.
Only, you have to splice it. The splicing technique itself is very simple http://www.spliceright.com/?page_id=17 , but ending up with shrouds having exactly the intended length is tricky.
My shrouds ended up almost 2" shorter than anticipated. Because, part of the splice is that you have to tuck the loose end for the length of 50 x the diameter into the center core of the standing part of rope. Through this the standing part is widened by the thicker core and shortens therefore as it is plait woven material.
However, once you have figured out and given the right extra length allowance, its amazingly simple and the result is excellent.
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Claus, I hadn't come across Dyneema before (Rip van Rogers? - I do try to stay awake to new developments, even though I qualified as an old fogey some while ago). I've googled it, so know a bit more, like its molecular structure, and use in body armour and fishing lines. Neither of the two on-line chandleries I usually use stock it as such (lots of expensive blocks specially designed to attach to it). Can you possibly help with some links to sources splicing know-how etc?
Being an unstayed mast sailor I don't have shrouds in mind, but strong slippery line has a putative junk-rig sailor pricking up his ears/eyes!
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...Can you possibly help with some links to sources splicing know-how etc? ...
Michael,
that splicing link I gave above is very good. Otherwise, where exactly you yourself can buy the stuff I do not know. I got some at the Klassieke Schepen boatshow and subsequently found that also my my local chandlery stocks it. Keep googling!
C.
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Hi, Claus, Michael.
Oh, I just love string!
Try English Braids http://www.englishbraids.com/ to choose a suitable material - they also make the trad-looking stuff I use on the Four Sisters - then look up
http://www.englishbraids.com/component/option,com_google/Itemid,46/id,1/view,advanced/
for a stockist near you.
For knots and splices, Ashleys book of Knots....or just raid your local branch of Waterstones, Amazon etc. Loads of titles.
Word of warning - Dyneema and other slippery stuff can be tricky to deal with. Make sure you use the right knot or splice for the material you are using and one that doesnt reduce the breaking strain too much.
Michael. For all that stuff you need to thread through your euphroe pre-stretched polyester is more supple and a whole lot cheaper!
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Thanks, Claus and Tony. More research clearly needed. Tony's links have identified a canal-side stockist fairly near here, so I'll go and investigate. Also, Mailspeed Marine are en route to my dentist, whither I am bound next week.
Tony's comments have triggered an internal search for a punch line which starts, "Euphroe if you want to...", but I can't get any further and anyway it sounds more like cricket than sailing. Best forgotten.
Levity aside, I should explain that for the majority of junk-rigging, all the well tried modern ropes are fine and I wouldn't go looking for anything else. However there are are a few applications where fairly fine, strong and inherently SLIPPERY "string" is helpful. Polyethylene rope (= cheap washing line, agricultural binder twine etc) is usually suggested, but it's yucky stuff to look at and handle and I want to avoid it if I can, so what I've read about Dyneema sounds intriguing. Obviously slipperiness is not usually a desirable attribute, and the rope makers have understandably spoiled the party from this point of view by using braided non-slip coverings. I'll have a look 'outside the box', eg at fishing line. Meanwhile if anyone comes across any 2 - 4 mm Dyneema application where its slither is untamed, I'd love to hear about it.
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Michael, have you tried kite flying web sites? I have found dyneema up to 250k breaking strain, could be worth a try to see what is around.
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Michael,
you must be looking for the 8-strand plaited 100% Dyneema, not the stuff braided with other material.
The plaited is so slippery few knots will hold at all, it must be spliced, but is very simple to be spliced.
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Hi, Claus.
Neat bit of splicing there. Is it an 8-strand backsplice (wow!) or a tube splice – ie tucked back through the weave a few times so it is gripped hard when put under tension?
I dont trust my skill in back splicing enough to make hard eyes around a thimble. Mine always stretch and let the thimble drop out, even with pre-stretched polyester. Much prefer to use a scaffold knot. It jambs up really tight on the thimble, being a slip knot, and has never failed to stay in place. You cant untie it, though, after its had a bit of tension on it. Have to cut it away.
Have never used HMPEs like Dyneema (ideal for standing rigging) so couldnt vouch for the knots ability to stay put – or how much the splice would slacken when tensioned. Practically no stretch in the actual rope but there must be a little slack to take up as the splice beds down?
Whats your experience with Dyneema stays?
Anyone out there having trouble working out what rope to use where?
My simple rule of thumb is:-
Have nothing to do with natural fibre ropes. They cost a bomb, believe it or not, look great for 10 minutes, cut your hands to ribbons then start to rot, smell, and fall apart.
(If you disagree - good luck to you. See you on the next lee shore.)
Instead, use the following:
Mooring and anchor
- Nice stretchy NYLON (a polyamide) Sinks, so good for anchor warps but not so good with mooring lines.
Haliyards
- Un-stretchy PRE-STRETCHED POLYESTER (expensive)
Sheets, reefing lines, etc
- Ordinary POLYESTER (cheaper)
Floating lines. e.g. Long shore lines, tow or rescue lines.
- POLYPROPYLENE (dirt cheap – good ol' B&Q!
Ultimate in Posh Boat standing rigging.
- Zylon (PBO or P-PHENYLENE-3,6-BENZO-BISOXAZOLE)
I know the latter sounds like something you might take for high blood pressure but it is a whole 20% stronger than Dyneema, Vectran or Spectra and so is much, much stronger than steel rope weight for weight.
Cost per metre? If you need to ask ... you cant afford it! It will never be seen on any boat of mine!
More info on normal ropes:
http://www.classicmarine.co.uk/Articles/Reference%20rope.htm
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.. Is it an 8-strand backsplice (wow!) or a tube splice – ie tucked back through the weave a few times so it is gripped hard when put under tension?
I dont trust my skill in back splicing enough to make hard eyes around a thimble. Mine always stretch and let the thimble drop out, even with pre-stretched polyester. ...
Tony,
the splice depicted is the one from the link above @ spliceright.com .
The shrouds were tested between tree and towbar hitch, the eyes loosened only insignificantly, certainly not enough for the hard eye to drop out.
Go for it, it's great.
C.
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Sorry, Claus.
Didnt read your original post thoroughly enough. (Ive got my lenses in now!)
I will get myself some forceps and have a go.
Cheers!
By the way - hows the tree?
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I've never used dyneema or any other super rope. I was interested in Tony saying he likes a scaffold knot to hold an eye in place. I would think that any of the fishing tackle knots might work well in dyneema for forming loops and eyes. They are designed to hold monofilament fishing lines which I would think are as slippery as dyneema.
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Slippery may not be the only problem, on one of the technical sites they stress that small radius pressure points can weaken dyneema. I would think any knot constitutes a small radius pressure point, hence use a thimble and long splice.
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Hi.
Had a go at the Dyneema –type eye splice using some nasty slippery plaited polyethelene I had lying about and a pair of snipe nosed pliers. Hooked it around the obligatory tree, tied the other end to a tommy bar (round turn and two half hitches) and heaved away until, with a loud snap, I found myself on my back with my legs in the air in the shrubbery.
Guess where it broke?
Thats right! At a half hitch.
Impressed, so had a look at the Splice Right kit – Only 92 Oz dollars(!) as advertised with gold plated Dyneema shears? Special splicing tweezers? Bit of PTFE? Gas powered hot knife? Snazzy bag to put it all in?
No thanks!
I will get by with Artery forceps (£3.50 from the Fishing tackle shop) a fag lighter and my good old Swiss Army knife. (You can buy at least a couple of metres of Dyneema with $92 Australian!)
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Thanks Claus. I seem to have it base over apex.
Do you mean more like this?
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Tony,
yes, the wrong one is wrong and the one with the question mark is the correct one.
A bit tight when you have to get the hard eye of the shroud end you have done first through the strands, but it does work. The needles are so smooth they help widening the gap in the strands.
The hollow needle splicing tool is also great for burying the loose end inside the standing part, you just tuck it in and slide it on inside the standing part, loose end in tow.
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Hi Guys. What is the problem with clapping on a seizing, either using a thimble or to form a small 'naked' loop? I'm not scoring points here, but asking because I'd like to know! It's my preferred method with braided rope anyway, and if you take a bit of care, use fine whipping twine and put on the extra frapping etc turns (my copy of "Marline Spike Sailor" hasn't surfaced yet after our move, and I can't remember all the jargon), the result is v neat and v strong. Isn't it?
I got some grey plaited 100% Dyneema from Mailspeed Marine yesterday (LOVELY stuff in the slippery stakes!), and I've tried a seizing. It works fine, and round a thimble there would be no kinks or v small radii to weaken the rope. As a hitch a constricter knot also seems to hold, especially if one uses two riding turns.
On the subject of breaking strains, isn't it true that for most uses in our kinds of sailing, ropes parting because of overload is almost never a practical issue? (Shrouds are an obvious exception with special considerations, and I know this is where Claus came in in the first place, until I caused a diversion!) Halyards and sheets are the thickness they are for ease of handling, not because they need to be anything like that strong. The Newlands were entirely logical in this respect with their practical attitude to the jib sheet once the loading had been greatly reduced by using club booms on the Storms etc.
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Hi, Michael.
Nothing wrong with a good, tightly whipped seizing, so long as the whipping twine bites deep enough into the material in use to make sufficient friction, thus keeping it all together. (As you point out, the frapping turns are important in this respect).
The only problem with Dyneema is that it is both hard and slippery, making this difficult.
If it holds, great, but the amount of grip the whipping has on the Dyneema can only change for the worse.
The beauty of the splice that Clause uses is that as the tension increases the splice grips ever harder! With enough bury there is also a much larger area of frictional surfaces in contact – which is why splices of all kinds are generally preferred to the equivalent knot or seizing.
Why do I still use a scaffold knot when making a hard eye?
Three reasons. No tools required; it takes only seconds to tie; I trust it to work.
However, where it REALLY matters (eg anchor chain to warp) I take my time and use a splice!
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Tony, all points taken with thanks. I must add a scaffold knot to my repetoire.
Emphasising that shrouds are a special case (I must look up the etymology, if it is known, of the use of the word shroud in this particular nautical context), in other rigging situations I still think a sense of proportion is needed - horses for courses, to mix a metaphor or two. If Dyneema is ten times stronger than polyester, and putting a bowline in it halves its strength, it is still five times stronger than polyester! In any case, as I indicated before, my personal use of Dyneema will be limited and specific, and I doubt if sudden failure of a luff-hauling parrel would ever be catastrophic in its consequences
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Question for Claus. How do you finish off the other end of the shroud, down at the bottom? I think they generally use a modern deadeye system. How do you fix to that, as you cannot form another eye in the other end the same way can you?
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Question for Claus. How do you finish off the other end of the shroud, down at the bottom? I think they generally use a modern deadeye system. How do you fix to that, as you cannot form another eye in the other end the same way can you?
Julian,
you can have hard eyes on either side, surprisingly you can widen up between the strands enough to squeeze the hard eye done first through.
Though,
I think the hard eye is not even necessary. The next shrouds I'll do I will leave the hard eyes out.
Good luck,
C.
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I have just got some dyneema shrouds for my BayCruiser and I am intrigued by the whole idea of non-metallic rigging. Regarding the splicing kit at the start of this thread, the special splicing tools are just locking forceps, which you can get from most toolshops eg
http://www.axminster.co.uk/product-Electro-Locking-Forceps-20071.htm
Has anyone used the modern deadeye system rather than hard eyes and lanyards or rigging screws?
http://www.precourt.ca/
Or the dyneema soft shackles, which seem a good idea but amazingly expensive. £24 each on ebay!
BTW I did a google search on dyneema shrouds and it came up with this threaad as the first hit!
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Following on from the last, have a look at this mind boggling way of doing an eye splice in dyneem when you can only get at one end of the rope. I think I can just about figure it out, but I don't have the nerve to try. They call it the Moebius splice with good reason
http://www.precourt.ca/brummel_splice.pdf
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Following on from the last, have a look at this mind boggling way of doing an eye splice in dyneem when you can only get at one end of the rope. I think I can just about figure it out, but I don't have the nerve to try. They call it the Moebius splice with good reason
http://www.precourt.ca/brummel_splice.pdf
Julian,
there is a trick.: You do not put in the hard eyes before you have prepared BOTH ends of the shroud. That way it is much easier to pull the second end through the strands of the first end.
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Just to report back after more practical sailing experience this year.:
The Dyneema shrouds were a complete success. I have full confidence now after somel heavy weather sails with full crew sitting on the gunwhales. I had marked all splicings to check for slip, but none occurred. The hard eyes are sitting tight. No major chafing.
I have it on all boats now, and the splicing gets quicker with more practice.
When we were in Venice, most other boats had it as well.
Recently I used some leftover to replace the steel wire of our garage door opener which had broken, perfect.
Go for it!
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I would agree with Claus. I have had dyneema all season and had no problems at all. They are a positive benefit when de-rigging to tow home. It is much easier to coil up the dyneema and stow them out of the way than wire, which always kinks and uncoils. Also, when I messed up coming alongside a pontoon at Bucklers Hard, I saved myself from falling in by doing a complete 360 degree pirouette round a shroud, much to the amusement of my daugthter. If I had been clutching wire, I think I would have cut my hand and fallen in.
I still have a wire forestay and am wondering whether to change that to dyneema. Obviuosly not a factor on the balanced-jib Byaraiders. what I would really like is to have a dyneema forestay with those neat little plastic deadeyes you can get from Precourt, but they are so expensive for two bits of plastic I can't bring myself to do it.
http://www.precourt.ca/
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In connection with shroud tension and lanyards, I learned that the mast of a recent BR (2010) fell down because his original (polypropylene ?) lanyards broke in a gust. I thus changed mine with Dyneema lanyards. Do some of you have more experience or comments on their behaviour in both material on the long run? Thanks
Guy
BR Catchando Bay
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... Do some of you have more experience or comments on their behaviour in both material on the long run? Thanks
Guy
BR Catchando Bay
Guy,
lanyards breaking in a gust, mast coming down, the horror.
Could have many reasons. Chafe, splice, too few turns due to forward mast rake?
It is not so much the lanyard material that matters -PP is fine BTW- but how it is done, and how it is maintained. I myself am using 2-3 mm Dyneema core material with a woven outer, and 4-5 turns min. I find material with a woven outer is slicker so it spreads the load better between the turns. No absolute need for Dyneema really, more important is an even spread of the load.
Lanyards are a consumable BTW, Cheap, and simple to replace.
I know the boats come with spliced PP lanyards, as is good boatbuilder practice. But today most people cannot splice, so they shy away from cutting the original lanyards off in order to use new material with a bowline knot instead. Wrong respect.
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Thank you for your helpful comments, Claus .
Yes, several reasons could account for the failure of these lanyards. However and even then, the alerting signs are not always obvious and I wonder if PP is really enough here. I experienced myself the breaking of the collar ( same PP) securing the gaff on the mast, after some excursions. Here also it might have been due to too much torsion on the gaff or some mishandling of mine but I changed this now for Dyneema and I sleep better. Nevertheless, I understand from your posts that the way these Dyneema ropes are fixed is of importance as well.
Guy
BR Catchando Bay
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Guy,
you can use shoelace or sewing thread for lanyards. As long as you give enough turns i.e. loops to build up a combined tensile strength of the lanyard connection which -at least- matches the tensile strength of the shroud.
Different with your single collar rope. There you cannot do loops. I have seen that break a few times, usually where it has been rubbed thin by edgy hole rims of the steel jaws. No big deal.
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An old thread, but I have just made my first two splices in dyneema. I can confirm that it is really quite easy and yes, it did come out shorter than expected, by about 5cm, but that just means a slightly longer lanyard on the forestay. I used the instructions for forming an eye splice from a gliding site, which does away with threading the full length through, but still has the load tightenting the eye.
http://www.keepitsoaring.com/LKSC/Downloads/dyneema%252Fspectra-splicing-manual.pdf
I also did it just using a normal Swedish fid. When I buried the long tail, I just did it in two inch sections, coming out the side of the braid each time and then going back in. Hard to describe but easy to do. I have posted some photos on my blog at
http://daisygracebaycruiser20no1.blogspot.com/2012/02/dyneema-forestay.html