Rope Stretch

[Gixer]

Hey all,
In the real world is there a noticeable difference between 5% and 8% stretch in braid on braid rope.
I guess it depends in what you’re using the rope for so lets say reefing lines.

 

[thinwater]

Hey all,
In the real world is there a noticeable difference between 5% and 8% stretch in braid on braid rope.
I guess it depends in what you’re using the rope for so lets say reefing lines.

Please specify "at X% breaking strength." 15% is common, but 10% and 20% are sometimes reported. How much it stretches depends on how hard you pull. Some chandlers are not good at stating this.

By real world, I assume you mean a casual sailor with polyester sails of indeterminate age. The answers for a racer or performance sailor will be different.

At 10-15% BS, 8% is probably double braid nylon and that is too much stretch. Settings will change as the wind rises and falls.

5% at 15% BS is a lot for polyester double braid. 3% would be more typical, and is suitable for most purposes (though some sailors prefer much less, for good reasons I won't get into).

But we need to know % BS.

 

[William_H]

Stretch for reefing lines will not be such a concern. The clew line of it stretches might leave the foot a little loose so too much camber. Likewise the tack reefing line if it stretches might leave the luff a little loose. Both of these can be fixed by winching in bit tighter. But probably not a concern. I use 6mm braid for reefing successfully. (21ft boat) A lot of sailing with reef in.
on the other hand I use a dyneema jib halyard (hank on jibs) and it is dismaying to find that it stretches noticeably. I have to retension after a while to keep luff tight. ol'will

 

[dunedin]

Stretch for reefing lines will not be such a concern. The clew line of it stretches might leave the foot a little loose so too much camber. Likewise the tack reefing line if it stretches might leave the luff a little loose. Both of these can be fixed by winching in bit tighter. But probably not a concern. I use 6mm braid for reefing successfully. (21ft boat) A lot of sailing with reef in.
on the other hand I use a dyneema jib halyard (hank on jibs) and it is dismaying to find that it stretches noticeably. I have to retension after a while to keep luff tight. ol'will

Not sure I would agree with that. Good sail shape is critical to sailing upwind in a blow, and need a very tight luff to act as a “full on cunningham” to keep the maximum depth forward of mid point, and clew tight outwards and close to boom to avoid excessive depth.
A sail that goes slightly baggy will increase heeling, reduce speed and reduce pointing ability - resulting in a slow and uncomfortable route to windward. We have often noted that with well reefed sails we can get a VMG up to twice that of a similar sized boat with baggy genoa (no foam luff) and poorly reefed mainsail. Means we are enjoying a short sail and then an hor in the sunshine, whilst they get pasted for a longer time.
PS. We have cruising dyneema for all our reef lines, and due to strength can be a bit thinner which makes less friction.

 

[ithet]

PS. We have cruising dyneema for all our reef lines, and due to strength can be a bit thinner which makes less friction.

I have been looking into new reef lines myself and think there is a bit of a myth developing. Amazingly standard Marlow Doublebraid polyester is stronger than any of the so called cruising dyneemas I have found - including Marlow's own D2 Club. The dyneema does have less stretch and is lighter.

 

[dunedin]

I have been looking into new reef lines myself and think there is a bit of a myth developing. Amazingly standard Marlow Doublebraid polyester is stronger than any of the so called cruising dyneemas I have found - including Marlow's own D2 Club. The dyneema does have less stretch and is lighter.

Ropes are generally sized for handling and grip, with breaking strength rarely a major factor outside superyachts. So the less stretch and less weight of cruising dyneema suit reefing lines.

 

[ithet]

Ropes are generally sized for handling and grip, with breaking strength rarely a major factor outside superyachts. So the less stretch and less weight of cruising dyneema suit reefing lines.

Yes that's as maybe and I noted so, but I was addressing the (often repeated here) comment about going down in size with cruising dyneema and keeping same strength, which is not necessarily true.

 

[thinwater]

I'm pretty sure the OP is gone.

 

[Neeves]

Yes that's as maybe and I noted so, but I was addressing the (often repeated here) comment about going down in size with cruising dyneema and keeping same strength, which is not necessarily true.

I think many use the word 'dyneema' and mean cruising dyneema because they are actually unprepared to pay dyneema prices and 100% dyneema is difficult to handle. Many are also cavalier with data, absence of data or attributing some component of data to a product that is far from the 'real thing'. Its the internet - make allowance.

Better - quote where the discrepancies lie and maybe the perpetrators of misleading data will withdraw and the forum would be more useful (if less argumentative).

If you pay for quality Dyneema - it is what is says on the box.

Jonathan

 

[Neeves]

I'm pretty sure the OP is gone.

You may be correct but possibly the OP has other immediate priorities, there is no demand that an OP sits waiting for replies and no demand that OP's comment on replies (which is unfortunate as some put effort into replies - and I am sure are grateful for feedback).

The OP might have had the answer he was looking for.....

Equally the OP might have been intimidated - by the knowledge thrown at him.



In answer to the OP - in the real world the difference is 3%. If you are a perfectionist or take some effort to tune your sails - 3% is important, especially if you know how to tune sails and take pride in getting the best from what you have. For many 3% is irrelevant.

My advice would be - if you are on a swift learning curve and have ambitions to race - worry about that 3% difference (you will not win if you take the 8% option). Otherwise - don't worry about it - as you can re-tension a halyard and re-trim a sail without loss of a place (in the race) simply by turning a winch handle.

But especially - save your money.

Jonathan

 

[Gixer]

I'm still here.

I was doing more research from the first response with regards to stretch and X% breaking strength. Liros don't seem to quote this so I'm struggling a bit, also there seams to be a difference it what the levels of Liros is called.

Thank you Neeves - You've answered my question

 

[dunedin]

The thing with something like a reefing line, is it often tends to go quite a long way from the end of the boom to the stopper.

We want the sail reef eye within about 40cm in from the boom end and 10cm above the boom - ie working length 50cm. But from there to the stopper is at least 10 metres, probably more.
So 3% stretch on 10m is about 30cm - some of that can be winched on tight, but 30cm variability on a 50cm working length can impact the sail shape.

PS. In Liros terms it is Dynamic Plus, I think, that is the cruising dyneema. For some odd reason, the steel green colour is claimed to have better wear resistance. That is what we have on jib furler and main halyard, the original white on reef lines etc (builder seemed to use a single reel so originally all ropes unhelpfully the same colour)

 

[ash12]

You may be correct but possibly the OP has other immediate priorities, there is no demand that an OP sits waiting for replies and no demand that OP's comment on replies (which is unfortunate as some put effort into replies - and I am sure are grateful for feedback).

The OP might have had the answer he was looking for.....

Equally the OP might have been intimidated - by the knowledge thrown at him.



In answer to the OP - in the real world the difference is 3%. If you are a perfectionist or take some effort to tune your sails - 3% is important, especially if you know how to tune sails and take pride in getting the best from what you have. For many 3% is irrelevant.

My advice would be - if you are on a swift learning curve and have ambitions to race - worry about that 3% difference (you will not win if you take the 8% option). Otherwise - don't worry about it - as you can re-tension a halyard and re-trim a sail without loss of a place (in the race) simply by turning a winch handle.

But especially - save your money.

Jonathan

Plus the forum just becomes more and more of an encyclopaedia

 

[Gixer]

Sorry if it took me a while to get on here and post a reply. Between homeschooling, working, housework and family issues I've been a bit busy the last few days...

On the + though, my yacht club have managed to get my boat back in the water!

 

[ash12]

Honestly it’s no problem, people have real world responsibilities that take precedence. Glad to hear she’s back in the water. Hopefully be able to get out there soon!

 

[thinwater]

Sorry if I offended. It's just funny how threads grow.

I am puzzeled that no one has clarified at "what % BS." I have seen both 10 and 15% used in catalogs, as though there was a standard. But I'm not sure there is, so it needs to be stated. Like cloth weight: is it per yard or sailmaker's yard? You need to say.

 

[Neeves]

Sorry if I offended. It's just funny how threads grow.

I am puzzeled that no one has clarified at "what % BS." I have seen both 10 and 15% used in catalogs........

That maybe because some, like me, are not sure what you mean by 'what % BS' . I'm not afraid to show my total ignorance or unwilling to guess to provide an answer - as the guess might then be adopted as gospel.

Jonathan

 

[thinwater]

That maybe because some, like me, are not sure what you mean by 'what % BS' . I'm not afraid to show my total ignorance or unwilling to guess to provide an answer - as the guess might then be adopted as gospel.

Jonathan

Break strength.

 

[Neeves]

Break strength.

I actually thought it was Break Strength, I'm not being picky as I guessed that's what was intended but UTS? or even Ultimate Tensile Strength - but %BS?

Break Strength is seldom quote, for --- anything, Minimum Tensile (or Minimum Break) Strength is quoted, sometimes Ultimate Tensile (or Break) strength is quoted but not always - so someone would need to test to derive BS - but I simply don't understand what %BS means in the context of your post. So I'm not surprised you are puzzled as if I were the OP, or anyone with my lack of understanding - I'd have no idea what you are looking for.

Sorry

Jonathan

I know that some use Forum, not necessarily this one as entertainment (I believe The Lounge serves that purpose). Members come here in the hope of having a question answered, or learning something from some of the posts (and offering answers, advice and random bits of information). I don't think people normally come here to be interrogated nor answer cryptic puzzles (we have normal life for that ).

So I think I might have devined to what you are alluding - and I think you have some of the answers, or at least an observation - which because you know what you are talking about - you could actually post.

 

[thinwater]

I said break strength in my first post (#2). I did. You are being pedantic (which I say only in jest because we are friends). Yes, I agree that it would be better if we were as specific as possible.

Obviously stretch is a percentage is a percentage of SOMETHING, since there are no units. Minimum tensile strength or any other measure of breaking strength works, so long as it is stated.

• The largest chandlery in the US (West Marine) quotes breaking strength.
• Jimmy Green quotes LBL (Liros Breaking Load)
• Defender Marine uses average tensile strength.

... so I was not being random or vague, only guilty of using the vernacular. I would have been happy with any measure. What does not work for me is "working stretch" and similar, since working load is ill defined for textiles (since there is no fatigue limit, there are many opinions).