Dyneema Shrouds and Splicing

[Craic]

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.

[Michael Rogers]

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!

[Craic]

...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.

[Tony]

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!

[Michael Rogers]

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.

[Edwin Davies 2]

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.

[Craic]

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.

[Tony]

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

[Craic]

.. 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.

[Tony]

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?

[Julian Swindell]

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.

[Edwin Davies 2]

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.

[Tony]

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!)

[Craic]

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[Tony]

Thanks Claus. I seem to have it base over apex.
Do you mean more like this?