Lets talk about rope....

savoir

Super Anarchist
4,914
201
There wasn't much point in mentioning SK90. So far no retailer is claiming to stock it. The only maufacturer I am aware of claiming to have it in production is Samson. FSE Robline, Liros, New England, Maffioli, Yale make no mention of it.

That will probably change in a couple of months.

 

markvannote

Member
376
27
Newport, RI
There wasn't much point in mentioning SK90. So far no retailer is claiming to stock it. The only maufacturer I am aware of claiming to have it in production is Samson. FSE Robline, Liros, New England, Maffioli, Yale make no mention of it.

That will probably change in a couple of months.
In reality, all the manufacturers are testing and deciding if it is worthwhile to offer SK-90. It is a definite improvement on SK-75 but if the performance is worth the extra cost is the debate. For most applications, until you get to maxis, AC, Volvo, SK-75 is more than sufficient to the point of the sheets getting too small to handle if you went to a realistic break strength.

Thanks.

Mark

 

NED28

Member
There wasn't much point in mentioning SK90. So far no retailer is claiming to stock it. The only maufacturer I am aware of claiming to have it in production is Samson. FSE Robline, Liros, New England, Maffioli, Yale make no mention of it.

That will probably change in a couple of months.
GM does market it. the lines are DSK90 Ultra and DSK90 Race (both website and in seahorse jan'10)

but you're totally right that for anyone but EB the line doesn't make sense yet

 

TheTwister

New member
34
0
I have become confused as well. I used to think that for any kind of static application (ie. halyards) Vectran was required as any kind of spectra would creep.

Now I am reading that for most boats <40ft you probably won't be able to load the line enough for creep to show, or long enough if you are just going around the cans. Is this true, and at what point would you start using vectran.

It seems that for most people spectra is the better choice as if you cannot tell the difference in terms of creep it is much more durable, and here I have been wasting money on vecran halyards!

Would be interested in what people think.
It is true that in most applications on your average sailboat creep does not present itself as a huge problem. That being said, Dyneema stretches more than Vectran which is why Vectran is a good solution for jib and main halyards. Hampidjian (Dux) and Maffioli (Ultra) both have processes which heat the material while under tension which changes the molecular setup of the fiber in a way which I cannot site off the top of my head which affects it's stretch characteristics but mostly increases tensile strength upwards of 15-20 percent as well as compacting it. For the same diameter you typically have more fiber which makes a rope with less stretch. I do not know that anyone has actually compared the stretch characteristics between Dux or Ultra as compared to Vectran.

Back to my original point which is your standard Dyneema jib halyard will stretch more than Vectran. Also, Vectran double braid is typically less money than a Dyneema double braid.

Thanks.

Mark
Looking at the #'s it would seem that vectran and dyneema stretch about the same, am I mistaken? I always though the difference was creep.

 
Yeah, I spent a couple weeks trying to get some 3mm D12 Max 90 quoted in the U.S. -Marlow's distribution isn't very robust here. APS can now sell it, but it's over $3/ft., and the D12 Max 78 was just over $2.50/ft. Based upon breaking strength/section area, the 90 is close to DUX's numbers. Really tough to get more than that as a comparison though.

 

NED28

Member
Looking at the #'s it would seem that vectran and dyneema stretch about the same, am I mistaken? I always though the difference was creep.
check the seahorse articles, and see if this answers your question (after all 3,3% elongation vs 3,4% is way differerent
wink.gif
), but/and also many more differences

Fibre property summary sheet.jpg

 

TheTwister

New member
34
0
Looking at the #'s it would seem that vectran and dyneema stretch about the same, am I mistaken? I always though the difference was creep.
check the seahorse articles, and see if this answers your question (after all 3,3% elongation vs 3,4% is way differerent
wink.gif
), but/and also many more differences

So I still don't understand why anyone would use vectran for halyards on a 30ft boat when it seems that spectra does just as good a job, and wears better

 

Daimond

Super Anarchist
4,118
0
SF Bay Area
Looking at the #'s it would seem that vectran and dyneema stretch about the same, am I mistaken? I always though the difference was creep.
check the seahorse articles, and see if this answers your question (after all 3,3% elongation vs 3,4% is way differerent
wink.gif
), but/and also many more differences

So I still don't understand why anyone would use vectran for halyards on a 30ft boat when it seems that spectra does just as good a job, and wears better

An example

On my 22 footer with a jib halyard length of approx 30' from head to sheet stopper a creep of even 1/4" requires someone to get off the rail and into the cockpit to make an adjustment, many times while the sail is under a pretty big load= lost righting moment and cluster F in cockpit. Someone else can do the math put I'm thinking a 1/4" in 30 feet is not that uncommon in spectra cored lines. Cruising no problemo.

 

TheTwister

New member
34
0
Looking at the #'s it would seem that vectran and dyneema stretch about the same, am I mistaken? I always though the difference was creep.
check the seahorse articles, and see if this answers your question (after all 3,3% elongation vs 3,4% is way differerent
wink.gif
), but/and also many more differences

So I still don't understand why anyone would use vectran for halyards on a 30ft boat when it seems that spectra does just as good a job, and wears better

An example

On my 22 footer with a jib halyard length of approx 30' from head to sheet stopper a creep of even 1/4" requires someone to get off the rail and into the cockpit to make an adjustment, many times while the sail is under a pretty big load= lost righting moment and cluster F in cockpit. Someone else can do the math put I'm thinking a 1/4" in 30 feet is not that uncommon in spectra cored lines. Cruising no problemo.
I understand that if the line creeped you would need to make adjustments. However what everyone seems to be saying is that creep is a funtion of A)Load B)Time. And a 30 footer seems unable to create enough load to significatly strain the line (say 5/16" would be smallest without being hard on the hands), also a beat to windward wouldn't be enough time to creep the line significantly.

 

Bruno

Super Anarchist
3,960
136
As a non-engineer, 1% on a sixty foot length, it's about 7", 1/2% about 3.5". Both significant numbers. The most consistently useful answer I've seen to the above issue is oversizing though I am now convinced that I should stretch (or have stretched) critical lines to 40% to set them, based on advice elsewhere in this forum.

 

Steam Flyer

Sophisticated Yet Humble
45,577
10,271
Eastern NC
 

 

So I still don't understand why anyone would use vectran for halyards on a 30ft boat when it seems that spectra does just as good a job, and wears better
 

 

An example

On my 22 footer with a jib halyard length of approx 30' from head to sheet stopper a creep of even 1/4" requires someone to get off the rail and into the cockpit to make an adjustment, many times while the sail is under a pretty big load= lost righting moment and cluster F in cockpit. Someone else can do the math put I'm thinking a 1/4" in 30 feet is not that uncommon in spectra cored lines. Cruising no problemo.
 

I understand that if the line creeped you would need to make adjustments. However what everyone seems to be saying is that creep is a funtion of A)Load B)Time. And a 30 footer seems unable to create enough load to significatly strain the line (say 5/16" would be smallest without being hard on the hands), also a beat to windward wouldn't be enough time to creep the line significantly.

I dunno if it's set, stretch, or creep, but on my 23'er we have to re-tension the main halyard (1/4" aramid) after 30 minutes or so of sailing to windward. Once it's re-tensioned, it seems to stay good all the rest of the day. That's a PITA and it's an even worse PITA that I have to keep it covered or the sun will melt it away like a vampire in the movies.

Instead of converting my genoa halyard(s) to hi-tech line I have just left them as wire/rope. Old school, but they don't need to be re-tensioned.

Ever.

And they're paid for ;)

FB- Doug

 
Last edited by a moderator:

NED28

Member
Couple of thoughts on the replies above

  • Creep vs Elongation: if I understand correctly: Creep is a function of time and load and reversible (when you take the load of there is no more creep), considering the race time (day of W/L races) and loads on typical 30-35 foot racers creep should be non-existent for most of us. Elongation is the irreversible lengthening of a strand of rope. this happens over a long period of time (probably unnoticable during a day's racing) and results in a permanently longer strand of rope. This is also why typical lines are pre-strectched at the factory. The numbers in the table I posted earlier refer to elongation.
  • Creep in halyards in first windward leg: maybe you've already tried or disproven this, but I have found on numerous occassions that if the halyard tension drops this has nothing to do with the halyard material, but with the quality/state of your stoppers. When we left the halyard on the winch there was no tension drop any longer (which has its own annoying side effects).
  • Vectran vs Spectra: Here in NL the typical store only has Polyester rope or Dyneema (and let me restate that Spectra is not the same as Dyneema), so I have never seen or touched Vectran and have no idea of the cost. But knowing how some people make buying decisions: Could it be that on the typical yacht people use Vectran rather then Spectra or Dyneema because of price? Same why we wouldn't (yet) buy SK90 for our round-the-cans racer but rather SK75 as the price difference is so much greater then the noticable added benefit to us

 
Last edited by a moderator:

Need4speed

New member
40
0
Spectra/Dyneema are a polyehthylene and they are NOT EXACTLY the same.

Dyneema comes in 3 grades - SK75 / SK78 / SK90 (plus older versions as SK60 / SK62 / SK65)
Fixed it for you!

Interesting (older) article: http://www.sailing.d...SK78-Part-1.pdf and http://www.sailing.d...SK78-Part-2.pdf

or check Seahorse jan'10 issue page 42 on SK90

Unfortnate i did not re-new my Seahorse subscription when it last expired.... can anyone post this page 42 from the January 2010 issue??

 

savoir

Super Anarchist
4,914
201
It is as interesting as it is disappointing to read opinions suggesting that Dyneema and Spectra are not the same stuff. How can it be that none of the self appointed experts on this subject are capable of some form of data backup ?

Spectra 900/1000/2000 = Dyneema SK60/75/78 The only difference is the name of the manufacturer.

What suckers they all are !

 
Last edited by a moderator:

Christian

Super Anarchist
Couple of thoughts on the replies above

  • Creep vs Elongation: if I understand correctly: Creep is a function of time and load and reversible (when you take the load of there is no more creep), considering the race time (day of W/L races) and loads on typical 30-35 foot racers creep should be non-existent for most of us. Elongation is the irreversible lengthening of a strand of rope. this happens over a long period of time (probably unnoticable during a day's racing) and results in a permanently longer strand of rope. This is also why typical lines are pre-strectched at the factory. The numbers in the table I posted earlier refer to elongation.
  • Creep in halyards in first windward leg: maybe you've already tried or disproven this, but I have found on numerous occassions that if the halyard tension drops this has nothing to do with the halyard material, but with the quality/state of your stoppers. When we left the halyard on the winch there was no tension drop any longer (which has its own annoying side effects).
  • Vectran vs Spectra: Here in NL the typical store only has Polyester rope or Dyneema (and let me restate that Spectra is not the same as Dyneema), so I have never seen or touched Vectran and have no idea of the cost. But knowing how some people make buying decisions: Could it be that on the typical yacht people use Vectran rather then Spectra or Dyneema because of price? Same why we wouldn't (yet) buy SK90 for our round-the-cans racer but rather SK75 as the price difference is so much greater then the noticable added benefit to us
Few corrections:

Elongation is just another word for getting longer - can be either temporary (elactic) or permanent (plastic)

Creep is the PERMANENT plastic deformation (think clay or play dough)

Stretch is temporary elastic deformation (think rubber band)

Spectra and Dyneema are two different brand names of the same chemical rope material.

Vectran has about the same stretch as SK75 Dyneema and much less creep. It is price wise close. Dyneema has better UV and abrasion resistance. Choice of one vs the other obviously depends on the application. An example: My main halyard is a 2:1 Vectran with (at the working end) a Dyneema tip - this way I have the low creep Vectran but with the exposed parts running over the sheave and the main shackle (when hoisted or stored) in Dyneema. Works wonders. I had problems with a pure Dyneema halyard hence the switch.

SK-78 is getting close to Vectran in terms of Creep - but still not as good

SK-90 Don't know about creep as it hasn't been released but the expectation is that it is not better than SK-78 as the emphasis of SK-90 over SK-78 was breaking strength increase more than anything else. Would also expect a bit less stretch as it is really just a heat treated 78 (a'la DUX but done before braiding) - expect a bit more constructional stretch due to the construct.

At lease that is my $ 0.02

 
Russ,

don't nerd out too hard, a lot of the data we might obtain from this is specific to material/brand/braid, etc.

- initial "stretch" isn't stretch. It's the application of load to align a suboptimal structure. How much a length stretches depends on it's construction, to include the weave and splices. Maybe better called set-lengthening.

- stretch is what happens to that optimal structure that can be undone - elastic

- creep is what happens to that optimal structure that cannot be undone -plastic

Dyneema does all of these things, you can spend money to have some of them done for you (see Dux 75) to eliminate variables

Vectran and other aramids tend to not do the latter two, but will still set a fair bit.

You could certainly go about determining a standard value for all lines based on an arbitrary length, which some people might find useful, I'd be down for a Miller quotient.

All of you, whatever you do, taper your splice, or I will be able to tell you exactly where your line will fail.

Couple of thoughts on the replies above

  • Creep vs Elongation: if I understand correctly: Creep is a function of time and load and reversible (when you take the load of there is no more creep), considering the race time (day of W/L races) and loads on typical 30-35 foot racers creep should be non-existent for most of us. Elongation is the irreversible lengthening of a strand of rope. this happens over a long period of time (probably unnoticable during a day's racing) and results in a permanently longer strand of rope. This is also why typical lines are pre-strectched at the factory. The numbers in the table I posted earlier refer to elongation.
  • Creep in halyards in first windward leg: maybe you've already tried or disproven this, but I have found on numerous occassions that if the halyard tension drops this has nothing to do with the halyard material, but with the quality/state of your stoppers. When we left the halyard on the winch there was no tension drop any longer (which has its own annoying side effects).
  • Vectran vs Spectra: Here in NL the typical store only has Polyester rope or Dyneema (and let me restate that Spectra is not the same as Dyneema), so I have never seen or touched Vectran and have no idea of the cost. But knowing how some people make buying decisions: Could it be that on the typical yacht people use Vectran rather then Spectra or Dyneema because of price? Same why we wouldn't (yet) buy SK90 for our round-the-cans racer but rather SK75 as the price difference is so much greater then the noticable added benefit to us
Few corrections:

Elongation is just another word for getting longer - can be either temporary (elactic) or permanent (plastic)

Creep is the PERMANENT plastic deformation (think clay or play dough)

Stretch is temporary elastic deformation (think rubber band)

Spectra and Dyneema are two different brand names of the same chemical rope material.

Vectran has about the same stretch as SK75 Dyneema and much less creep. It is price wise close. Dyneema has better UV and abrasion resistance. Choice of one vs the other obviously depends on the application. An example: My main halyard is a 2:1 Vectran with (at the working end) a Dyneema tip - this way I have the low creep Vectran but with the exposed parts running over the sheave and the main shackle (when hoisted or stored) in Dyneema. Works wonders. I had problems with a pure Dyneema halyard hence the switch.

SK-78 is getting close to Vectran in terms of Creep - but still not as good

SK-90 Don't know about creep as it hasn't been released but the expectation is that it is not better than SK-78 as the emphasis of SK-90 over SK-78 was breaking strength increase more than anything else. Would also expect a bit less stretch as it is really just a heat treated 78 (a'la DUX but done before braiding) - expect a bit more constructional stretch due to the construct.

At lease that is my $ 0.02

Ted and Christian

You two win the prize for most correct and clear answers. I think people don't realize when comparing line materials, that the most important data point for high-load rigging which you need to have stay a consistent length once the load is applied is the materials yield stress. That is the point at which the material will begin to plasticly deform. It took a while for me to realize that this is really what is bothering me about how the technical information for line is marketed. My hypothesis is that if you were to compare yield stresses of the different materials, it would become very apparent which lines to use for given applications.

 


Latest posts



Top