I would have thought that would be fine - it's a good question.

I always thought V12 was lower streatch and stronger than D12 but this seems not to be the case looking at the data on the Marlow site.

http://www.marlowropes.com/public/pageManager.cfm?page_id=156 - http://www.marlowropes.com/public/pageManager.cfm?page_id=15 6

Why choose V12 over D12 or vice versa?

What is the % extension & breaking loads of halyard wire compared to the V/D12?

Also - why is Vectran so much more expensive when it seems it has similar properties? (I guess they don't have similar properties ...)

It's becoming common in some high performance development classes such as International 14's and 12ft Skiffs.

The advantages are that it's lighter, and sometimes stronger. It's also cheaper by the metre, and you save money have terminals or eyes fitted. And it's easier to cut if you get trapped.

The disadvantages are that for equal breaking load the string will have a bigger diameter, and therefore greater windage. The string is not UV resistant, so needs to be replaced every 6months if you leave your mast up outside. The string is not wear resistant, and often wears out where the string passes through spreaders. The latter two problems can be overcome to a certain extent with an "outer" but this again increases windage.

D12 is dyneema,lighter and a bit more chemical resistant than V12 which is vectran. Other than that - pretty similar.

I only used V12 because I had a load of it left over from making a decent jib halyard (the supplier needed two attempts to get the length right and sent double what I needed)

It's certainly dead easy to put eyes in - just needs a fid (or a modified chopstick in my case) and some whipping twine.

UV isn't a problem if it's inside the jib luff -though I guess I'd better worry about the halyard which is out there on the mast rain and shinem (50% strength loss over 3 years apparently... and it would be nasty if it snapped!

Nick

I  think   I had 5 or 6mm  vectran   put on the 14.  This  approx 4 years ago so  ropes have developed  but the reason for  this was  2 fold,   it not just breaking strain but  the   elongation under load  that counts   and you  need to go up to  6mm to get the same  as dyform for your forestay.  The other advanatage at least  it gives you some leeway  if the forestay is left out in the sun.

Given the chemical attack issue is not that big why pay double for vectran?

Dyneema, in common with most ropes, suffers from creep - that is, it will stretch not merely when initially subjected to a load but also over time, whereas Vectran is much more creep resistant.

So for things that are (or should be) frequently adjusted, Dyneema is fine, but for standing rigging which needs to maintain its length throughout a race, use Vectran.

I'd have thought that Vectran would be great inside a jib luff, so long as the diameter was well-chosen, but it is probably harder to tell when it has been damaged (we replace wire if there are any loose strands, after all), so catastrophic failure could be more of an issue (it's easier to cut than wire too, after all).

That's not what the data on the marlow site says ... they both extend about 3% at 50% max load ....

Explain ...

Here, I've looked up a definition for you:

Creep
the dimensional change with time of a material under load. At room temperature it is also called cold flow.

Which is what I said in the passage you first quoted.

Basically, if you pull on a metal spring it will extend a certain % then stop (if at room temperature). If you pull on plastic, it stretches intially (which is what Marlow are quoting you), then apparently stops but actually continues to elongate slowly as time passes. Not significant for short durations, but I guess that over the course of a race your Dyneema standing rigging could creep enough to lose some of its tension. With Vectran that's much-reduced.

In their tech data sheets they give extension % v load graphs.

In none of their data is there any mention of how this extension changes over time.

I am sure you are correct because when I have tried D12 for trap lines they have felt quite spongey compared to V12 - but that's not creep anyway

If D12 extends to 3% at 50% load; any idea how much further it will extend over time with continued 50% load?

It does say on the V12 data sheet "will not creep" ...

Here's what vectranfiber.com say about Vectran:

In experiments on yarns and small braids,minimal creep was observed with loads up to 30% of ratedbreaking load.These tests ran for as long as 10,000 hours at ambient temperatures

I've just read, however, the assertion that provided Dyneema is loaded less than 50% of its rated strength, it won't creep significantly, so maybe the distinction between Vectran and Dyneema is not so important for us. Detailed creep figures tend to be closely guarded trade secrets though, apparently.

All ropes need to be stretched repeatedly, of course, before the fibres align and the rope finds its effective final length (hence your boingy trapeze ropes, I'd suggest, Rick), and it needs to do that every time you coil or uncoil it - maybe a better reason not to use rope in your jib luff. I'd also be concerned about the rope cutting under load - steel wire is much more resistant in that respect.

Nick: why don't you just flake your jib down onto the foredeck? Saves the twisting you get by rolling. I never remove my jib from the boat - leave the halyard and tack attached, flake it and shove the cover over it. Saves all that taping, and I doubt it suffers any more than if it is continually taken off, put in a bag and lugged around/sat on/buckled etc.

Interesting ... seems that Vectran may be over spec'ed for us then. It's almost double the price so I guess it's only really justified in parts of the standing rigging. i.e. Shroud adjusters etc ...

I'm using Holt Ultra-line (allegedly Vectran) for my lowers, but have taken to referring to it (when talking to my non-technical - but pretty - crew) as 'the stretchy non-stretch stuff'.

I keep tightening them up, but to be fair, maybe the fibres are still aligning!

Rick, here's an experiment to try:

Pull the core out of a fairly thin dyneema rope, say 3mm or less.  Tie one end to a beam in your garage ceiling or somewhere similar.  Use the other end to suspend a heavy object (lawnmower, road trailer axel etc!) about 1" above the ground, swinging freely. If you leave it overnight, when you come back in the morning the heavy thing will be resting on the floor because of the creep.

This is why dyneema is useless as standing rigging.

(edit): I'm now ready to be proven wrong and shot down in flames!

Synthetics have been tried and discarded on Swift Solos for the main stays. The creep makes it really hard to duplicate rig tension settings. It is still being used on the cap shrouds as the creep issue is much less critical here and there are weight savings.

The guys in the Tris that are using synthetics have started using Dynex Dux. Limited creep, good uv resistance, easy to splice, good abrasion resistance and inexpensive. They are using it on rotating rigs which don't have a problem with creep as they run with slack rigging anyway to allow mast rotation. The rope can be obtained here http://www.precourt.ca/ - http://www.precourt.ca/  

Cheers    

the solution there is to attach an old bit of 3 strand to the end of your jib halyard when the boat is ashore then pull the halyard up. now all your nice expensive string is hidden inside mast/under cover so UV isnt a problem. you can get your halyard back when you want to sail by pulling on old bit of 3 strand. obviously you wouldnt leave the old bit of string on when you were sailing as it would add too much weight and windage.

Stick to wire, or PBO if you have the funds to burn.

Keep the V212/D12 for high-load running rigging. works great for kickers, downhauls, trapeze wires, etc.

It's a synthetic cable that is covered with a pvc sheath to protect it. Very light, very strong, and virtually no stretch or creep. I think the numbers I've been quoted are something like 1/5th the weight of wire with about 2 or 3 times the strength.

The only problem with it on dinghys at the moment is the terminators, which are quite beefy stainless "compression joint" things. Vary cool stuff though.

http://www.oceanyachtsystems.co.uk/PBO.html - http://www.oceanyachtsystems.co.uk/PBO.html

Polybenzoxazole. A really strong, low stretch, low creep, lightweight fibre.

It's woeful at sharp turns and sunlight though.

Just let you know that I've used vectran on my first i14 :

4 mm for the forestay

3 mm shrouds and caps

4 mm lowers

My Cherub has know the same. It has been a hassle to get them strech but after a few time its fine know.

Advantages : far easier to change by yourself, cheeper than cable, ligher

Disadvantages : strech at the beginning and presumly all its life but slower, not obvious to check, can be damage by flapping on the road.

So it is possible. Still big question marks over damage (cutting) of standing rigging in my mind. Guytoon mentions trailing - hadn't thought of that one, but then, a wire thimble doesn't take kindly to a scrape up the M1 , we've found.

Aside: I always thought the loads on the shrouds were higher than on the forestay, so if 3mm sufficed for the shrouds I'd try less on the forestay.

Actually, I've been using 2.5mm V12 (Vectran) 2:1'd on my 3000 jib halyard for a season no probs. Haven't noticed the tension going off over time, but maybe after all this talk I should measure before and after racing?! (But how will I know if it's the rigging or the hull creeping?)

You thought right.

Right, but anyone who's serious about their racing should be doing this anyway.

Being serious and being idle clearly don't mix . Maybe I don't really want to know there's a problem...

How are you going to repeat rig tension setting? Have you measured how it changes?

Yes I can see replacing all the stays with vectran is a poor idea, just due to creep.  You can keep on retensioning the forestay (we do that on the 3k whenever the jib goes up!) but the mast would slowly rake forward!

But using V12 for the forestay only, seems like an increasingly good idea on my boat.

Thanks for the input people.

Until someone protests you Nick - the 3k rules specify wire (of the original diameter even...).

Dumb rule then. Needs dumping.  What do they say about adjustable vectran lowers?

It's meant to avoid everyone rushing out and wasting £££'s on things that make you 0.00001% faster.

Adjustable lowers: anything supplied as built is OK and may be adopted by others. That said, I've yet to feel any benefit...