Broken jib sheet questions

[poiu]

Originally Posted by Dockhead

Totally bizarre. Even if chafed at that spot, it should have had a huge reserve of strength.

I have never heard of such a case and can't imagine why it happened other than, perhaps, a defect in the rope. That kind of deflection angle is no problem at all. Have you checked for any sharp edges where the rope might have been chafing unbeknownst?

If it were my boat, I think I would check carefully for sharp edges, then just replace the rope and forget about it. I have a lot of dyneema rope on my boat, but I use double braid polyester for my sheets -- 18mm so one size down from yours. These are under a lot of load, and I like for them to be fat and easy to handle. The bulk of a larger rope is also a certain proof against chafing -- more material which can be sacrificed.

But that much diameter is not needed for the winch, so if you wanted to go to something smaller and dyneema cored, that wouldn't be any problem other than cost. The racers on here (paging Exile) will tell you that you actually need dyneema sheets, for sail trim -- so that the sheet doesn't stretch and spill wind. IIRC you have the same sails as I do (it was you who introduced me to my sailmaker!), and I guess that could be a valid point, since the carbon lam sails are pretty low stretch.

Marlowbraid 20mm has an average breaking strength of 11 (!) tons; you could go to something like 16mm D2 Racing 78 which has the same strength. 16mm sheets handle fine and will be fine on your winches. They will be vastly lighter, less windage, easier to handle, and will run better through the blocks. 11 tons seems like massive overkill to me, but you could do 18mm dyneema if you wanted even more.

Note that with dyneema you don't want to use knots, because the cover pulls off, so you can't use bowlines. You will want spliced soft eyes and soft shackles, or one of another of the various attachment methods, which the racers on here will know about better than I do.

The cost of dyneema sheets of that size will be pretty huge, which is a good reason to stay with double braid, however.

Thanks for your tips.

There is no chafe and no sharp points. I have ruled those issues out.

Interesting that dyneema can't be knotted. I didn't know that.

It's looking like I will just have to put up with it as hopefully a one off failure, though I don't believe it really. Also to mitigate further damage on new sheets with end to ending and regular shortening. The shortening of course won't be so easy with dyneema sheets if I can't knot it, so that might swing the decision of what type to go for.

[poiu]

Originally Posted by Snowpetrel

What chemicals do you put on the Deck? Ever sprayed the block with lubricant? This might have weakened the line locally.

Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app

No chemicals, anywhere, just water. I suppose it is possible a spill during storage may have occurred. I can't rule that out, but nothing I am aware of.

[44'cruisingcat]

Hard on the wind in 16 knots, sheet loads would be getting pretty big. Apparent wind speeds up around 24 knots?


With 6 year old rope shouldn't come as too much of a shock when it breaks. I broke a 14 mm jib sheet that was only 3 years old, in similar conditions.


Which reminds me, about time I replaced them again...

[poiu]

Originally Posted by 44'cruisingcat

Hard on the wind in 16 knots, sheet loads would be getting pretty big. Apparent wind speeds up around 24 knots?


With 6 year old rope shouldn't come as too much of a shock when it breaks. I broke a 14 mm jib sheet that was only 3 years old, in similar conditions.


Which reminds me, about time I replaced them again...

Good point about apparent wind, I'd overlooked that. So the sheet loads would be about 1,300 kg instead of 700 kg. A lot higher, but still a fraction of the 8,000 to 11,000 max load.

I'm surprised you think it OK for a 6 year old sheet to break at such a low load especially when not particularly high miles have been done.

[Dockhead]

Originally Posted by poiu

Thanks for your tips.

There is no chafe and no sharp points. I have ruled those issues out.

Interesting that dyneema can't be knotted. I didn't know that.

It's looking like I will just have to put up with it as hopefully a one off failure, though I don't believe it really. Also to mitigate further damage on new sheets with end to ending and regular shortening. The shortening of course won't be so easy with dyneema sheets if I can't knot it, so that might swing the decision of what type to go for.

You CAN knot dyneema, of course, but it works badly. Here's a good resource:

http://www.neropes.com/Resources/sail_reprint.pdf

According to this test, a bowline in a piece of 12mm double braid reduces strength by 45%, and for a spectra/polyester rope (which will have similar qualities to dyneema/polyseter rope like you will be looking at) -- 60%. Note that a splice in double braid reduces strength by 12%, but a splice in the high tech rope -- 0%. So the same piece of high tech rope, spliced, will be 2 1/2 times as strong as the same piece of rope, knotted. This is why you don't use knots with high tech rope.


I'm just about to buy new sheets myself, and so I'm going through the same process. Cost of ownership of dyneema sheets is undoubtedly far higher, as the cost of acquisition is not only much greater, but you will also have to pay for new splices (unless you can do them yourself) every time you shorten them.


I am looking for dyneema rope like the new D78 Grand Prix, which has got Technora in the cover, so much more chafe resistant. This might extend the shortening/end-for-ending cycle. Still don't know which way I'm going to go, however. With my new blade jib, there is some rubbing on the shrouds, which makes me a little leery of spending too much on the sheets.

[poiu]

Originally Posted by Dockhead

You CAN knot dyneema, of course, but it works badly. Here's a good resource:

http://www.neropes.com/Resources/sail_reprint.pdf

According to this test, a bowline in a piece of 12mm double braid reduces strength by 45%, and for a spectra/polyester rope (which will have similar qualities to dyneema/polyseter rope like you will be looking at) -- 60%. Note that a splice in double braid reduces strength by 12%, but a splice in the high tech rope -- 0%. So the same piece of high tech rope, spliced, will be 2 1/2 times as strong as the same piece of rope, knotted. This is why you don't use knots with high tech rope.


I'm just about to buy new sheets myself, and so I'm going through the same process. Cost of ownership of dyneema sheets is undoubtedly far higher, as the cost of acquisition is not only much greater, but you will also have to pay for new splices (unless you can do them yourself) every time you shorten them.


I am looking for dyneema rope like the new D78 Grand Prix, which has got Technora in the cover, so much more chafe resistant. This might extend the shortening/end-for-ending cycle. Still don't know which way I'm going to go, however. With my new blade jib, there is some rubbing on the shrouds, which makes me a little leery of spending too much on the sheets.

Just a thought on splices and shortening. I was told by my rigger that I couldn't splice old double braid rope, rather he refused to do it saying it wouldn't be possible as the rope has gone too tight. I can't do my own braid/braid splices yet so have to rely on this advice, but this means if you go for a spliced end that you won't be able to shorten.

How about this: strip back the cover of a double braid sheet and put in a single braid splice. The single braid will be thinner and subject to lower stresses around the car sheave, plus it is the strongest rope, especially in dyneema. Stripping it back will make the loop small and flexible. Put a brummel spliced loop on the end of it a sacrificial length of single braid dyneema and cow hitch it on (or eye to eye for slightly better strength). The cow hitch will lose only 15% of rope strength and the eye 10%, so should be an acceptable loss. This is the section that goes through the car and to the clew and therefore which is most loaded and subject to fatigue stresses and the only bit that should need replacing regularly. This could be a short section. maybe 4 or 5m long as when running or even reaching the loads are much lower and there should be less worries about damage to the main double braid rope running through the car sheave.

[zeehag]

Originally Posted by poiu

I'm sorry if you think I am making a big deal out of it. I think I am giving it the attention it deserves.

I do think it important to understand what is going on otherwise it will only happen again and to loose 90% of my line strength again in little time is not good enough for me.

Think again about keeping old line unless you know you don't have line like mine that has been damaged such that its strength is 90% lost. If you do then those lines are pretty much useless and in fact dangerous if you use them to protect your boat or your life.

rodlmffao. have you been sailing since 1955? ALL lines are reusable in a situation , and all lines are able to perform other duties than the ones YOU assign to them.
and so you will buy new line to use for lashing stuff to your topsides in a blow.
you will buy brand new line to use for dinghy painter...
you will buy brand new lines for sail cover gaskets in a bigger blow..
you will buy brand new line for.. all other non stressed jobs....
you are going to buy brand new line for whatever use you deem necessary??
that is absurd, sorry.
not all lines are subject to the abuse that one has undergone.
when you are actually out in an ocean sailing your boat, you are gonna pull into a service station to purchase lines when your current one pops?? usually one sees only the outer sheathing rupture. UNLESS there is a source for a good cut such as yours have exhibited. or unless the abuse has been ongoing for some time, this aint happening. i have not once seen this occur with my own lines--and i have owned my own boats since 1990. i have been sailing since 1955.

i would be looking for the source of the cut in the line. what do you have on your boat and where is it that would offer such a nicely cut line.
was the line in use in its current usage when you received the boat?? coulda been a problem with previous owners methods..
is it at a shroud?? is it a friction when sailing of the line on a shroud?? if so, best be changing out that shroud. looks like an ill done knife cut, so there is something either eating your lines or cutting them.you need to find this source.
OLD line can do this with chafe.
was it ruptured then cut by a slamming on the rigging? if so, may be you need to addressing sharp edges
did you wash your lines in something??
whatever was done to that fail line should be removed and replaced with whatever it is you need to use to make sure the next one does not do this again. or your methods need to change, so as to prevent this from happening again.
i have not seen a line CUT like that except from chafe--severe chafe. stop doing whatever it is you do with your lines to cause this. slapping halyards can do this in a severe wind situation. yes even ONE storm can do this to your halyards. sheets-- whatever chafes em is the culprit. look to the shrouds for barbs. look for causes of chafe in your rig.
sheets befouling on rigging CAN do this, but i have yet to see this. i prevent mine from chafing while i am sitting idle.
wind is not your friend.

if the cut is from chafe, your next use for this line will have a different chafe spot.
chafe is important to address BEFORE you have fail at sea.
or at the dock.
if the rupture was caused by the age iof the line, you can reuse that line in another stress free situation--sail cover gaskets and lashing items in a blow...

if you used a chemical to clean em, you goofed. donot do that again.
replace the line and reassign the old one to other uses.

funny how the old fashioned uncomfortable natural lines never did this crap. took forever to chafe one that badly. they were 3 strand. hard to kill. didnt creep or rupture and lasted many years.

sun damages everything as well, doesnt matter where ye are. sitting in sun many years even without use makes things fail.

and then, this COULD have been a fail point in the manufacturing of the line.
many possibilities but only 1 truth.
find it.
fix it.
re assign those lines to other duties, such as lashings or painters.

[poiu]

Originally Posted by zeehag

rodlmffao. have you been sailing since 1955? ALL lines are reusable in a situation , and all lines are able to perform other duties than the ones YOU assign to them.
and so you will buy new line to use for lashing stuff to your topsides in a blow.
you will buy brand new line to use for dinghy painter...
you will buy brand new lines for sail cover gaskets in a bigger blow..
you will buy brand new line for.. all other non stressed jobs....
you are going to buy brand new line for whatever use you deem necessary??
that is absurd, sorry.
not all lines are subject to the abuse that one has undergone.
when you are actually out in an ocean sailing your boat, you are gonna pull into a service station to purchase lines when your current one pops?? usually one sees only the outer sheathing rupture. UNLESS there is a source for a good cut such as yours have exhibited. or unless the abuse has been ongoing for some time, this aint happening. i have not once seen this occur with my own lines--and i have owned my own boats since 1990. i have been sailing since 1955.

i would be looking for the source of the cut in the line. what do you have on your boat and where is it that would offer such a nicely cut line.
was the line in use in its current usage when you received the boat?? coulda been a problem with previous owners methods..
is it at a shroud?? is it a friction when sailing of the line on a shroud?? if so, best be changing out that shroud. looks like an ill done knife cut, so there is something either eating your lines or cutting them.you need to find this source.
OLD line can do this with chafe.
was it ruptured then cut by a slamming on the rigging? if so, may be you need to addressing sharp edges
did you wash your lines in something??
whatever was done to that fail line should be removed and replaced with whatever it is you need to use to make sure the next one does not do this again. or your methods need to change, so as to prevent this from happening again.
i have not seen a line CUT like that except from chafe--severe chafe. stop doing whatever it is you do with your lines to cause this. slapping halyards can do this in a severe wind situation. yes even ONE storm can do this to your halyards. sheets-- whatever chafes em is the culprit. look to the shrouds for barbs. look for causes of chafe in your rig.
sheets befouling on rigging CAN do this, but i have yet to see this. i prevent mine from chafing while i am sitting idle.
wind is not your friend.

if the cut is from chafe, your next use for this line will have a different chafe spot.
chafe is important to address BEFORE you have fail at sea.
or at the dock.
if the rupture was caused by the age iof the line, you can reuse that line in another stress free situation--sail cover gaskets and lashing items in a blow...

if you used a chemical to clean em, you goofed. donot do that again.
replace the line and reassign the old one to other uses.

funny how the old fashioned uncomfortable natural lines never did this crap. took forever to chafe one that badly. they were 3 strand. hard to kill. didnt creep or rupture and lasted many years.

sun damages everything as well, doesnt matter where ye are. sitting in sun many years even without use makes things fail.

and then, this COULD have been a fail point in the manufacturing of the line.
many possibilities but only 1 truth.
find it.
fix it.
re assign those lines to other duties, such as lashings or painters.

Zee,

Thanks for all your suggestions.

There was definitely no chafe and no sharp edges in the area, so I am at a loss to know what snapped the line. I will put it down to fatigue combined with maybe a defect and UV damage. That's just my best guess. I shall retire them. As they have failed I will not keep them. They are yours if you come to the Easter Carib, though I wouldn't use them for anything but wrapping up Christmas presents (large presents).

[Dockhead]

Originally Posted by poiu

Just a thought on splices and shortening. I was told by my rigger that I couldn't splice old double braid rope, rather he refused to do it saying it wouldn't be possible as the rope has gone too tight. I can't do my own braid/braid splices yet so have to rely on this advice, but this means if you go for a spliced end that you won't be able to shorten.

How about this: strip back the cover of a double braid sheet and put in a single braid splice. The single braid will be thinner and subject to lower stresses around the car sheave, plus it is the strongest rope, especially in dyneema. Stripping it back will make the loop small and flexible. Put a brummel spliced loop on the end of it a sacrificial length of single braid dyneema and cow hitch it on (or eye to eye for slightly better strength). The cow hitch will lose only 15% of rope strength and the eye 10%, so should be an acceptable loss. This is the section that goes through the car and to the clew and therefore which is most loaded and subject to fatigue stresses and the only bit that should need replacing regularly. This could be a short section. maybe 4 or 5m long as when running or even reaching the loads are much lower and there should be less worries about damage to the main double braid rope running through the car sheave.

That should work, but why such complexity? The car sheave is just no problem whatsoever for any type of rope. It should not be a wear point at all. Sheets wear out at the attachment points to the clew, which is why we shorten them, and anywhere they rub against anything. You will create a new stress point with such an arrangement. I think it is much preferable to have single unspliced lengths of rope where possible -- much less to go wrong.

If you're going to go with Dyneema, I think I would just splice an eye at the end of each sheet, and enjoy life for a couple of years. Then if you see any signs of wear or stress, then cut off the eyes and whip the ends, and splice in new eyes on the other ends, which will not have been stressed so will not be any problem to splice. By the time THAT end is worn out, you will want to replace the rope anyway, probably. But I bet you could cut off a bit more and resplice the original ends for a third life -- dyneema doesn't fuse together under strain the way polyester does..

[Dockhead]

Originally Posted by poiu

Zee,

Thanks for all your suggestions.

There was definitely no chafe and no sharp edges in the area, so I am at a loss to know what snapped the line. I will put it down to fatigue combined with maybe a defect and UV damage. That's just my best guess. I shall retire them. As they have failed I will not keep them. They are yours if you come to the Easter Carib, though I wouldn't use them for anything but wrapping up Christmas presents (large presents).

Definitely ditch that old rope

If you can't figure out what went wrong with it, then you can't know what to expect from it in the future, either.

I would burn it, probably, if I were you.

[Alberg 34]

If the line just snapped it was either an extreme load or a MFG defect. There are also some places that sell (what are called seconds ) Replace with good quality lines Most lines will show wear telling you that they need to be replaced

[poiu]

Originally Posted by Dockhead

That should work, but why such complexity? The car sheave is just no problem whatsoever for any type of rope. It should not be a wear point at all. Sheets wear out at the attachment points to the clew, which is why we shorten them, and anywhere they rub against anything. You will create a new stress point with such an arrangement. I think it is much preferable to have single unspliced lengths of rope where possible -- much less to go wrong.

If you're going to go with Dyneema, I think I would just splice an eye at the end of each sheet, and enjoy life for a couple of years. Then if you see any signs of wear or stress, then cut off the eyes and whip the ends, and splice in new eyes on the other ends, which will not have been stressed so will not be any problem to splice. By the time THAT end is worn out, you will want to replace the rope anyway, probably. But I bet you could cut off a bit more and resplice the original ends for a third life -- dyneema doesn't fuse together under strain the way polyester does..

My suggestion was made with the assumption that the rope is being weakened by running over the car sheave and this is something to get protection from. As I discovered and posted in my previous posts, running over a small sheave massively degrades wire and I believe also to a slightly lesser degree synthetic rope. With large safety margins in sheet sizing there is no reason for the sheets to last for a very long time if protected from this damage as well as chafe, abrasion and UV.

[Cheechako]

That 65mm sheave seems pretty small diameter to me. for a sheet that big and a 66 ft boat. I definitely wouldn't use Dyneema on a sheet . Due to pleasure of handling.

[Dockhead]

Originally Posted by poiu

My suggestion was made with the assumption that the rope is being weakened by running over the car sheave and this is something to get protection from. As I discovered and posted in my previous posts, running over a small sheave massively degrades wire and I believe also to a slightly lesser degree synthetic rope. With large safety margins in sheet sizing there is no reason for the sheets to last for a very long time if protected from this damage as well as chafe, abrasion and UV.

Well, for a definitive answer we should ask some of the experts on here (which I am clearly not), but I don't think that reasonably sized genoa car sheaves are the source of even the slightest wear or stress for sheets. I presume you have the jumbo Selden ones, like mine probably? Remember rope and wire are two different things entirely. Polyester fibers are 1000's of times more flexible than stainless wire.


P.S. I just got a nose bleed from the first proposal for dyneema sheets for my boat -- 16 pounds per meter (!!!). 4x the price of 18mm Marlowebraid.

[accomplice]

I had the same thing happen to me 15 months ago -- a large, double braid (5/8") sheet parted where it went around a sheave in the genoa car. After bringing the sail back under control and tying a now-shorter jib sheet to the clew, I set about trying to figure out how and why this could happen, and why there.

What I observed was that on most points of sail in a good breeze, the jib sheets not only stretch, but stretch by an amount that varies with an amplitude of up to several inches. The way our boat is setup, the sheets go from a cockpit winch back to a turning block at the stern, forward on deck a genoa car, and then up to the clew. The distance from the winch to the turning block to the car was about 30 feet, with another 5 to 20 feet to the clew. Watching a point on the sheet where it passed over the sheave, it would move forward and back several inches. There was enough strain on the jib sheets that they were noticibly thinner. We had been on the same point of sail, a beam reach, for over 48 hours. The wind was in the high teens.

What I believe happened was that although the line hadn't chafed, that the sheave was of large diameter, that the line working itself back and forth, under strain, pressing hard against the sheave gradually weakened until it parted. I do not know whether it was a process of work hardening, where the continued flexing made the fibres more brittle, or whether there was heat buildup internal to the line, or what mechanism was at work, but I do know it parted in the middle of the line, at the car, not the bowline on the clew.

I asked my sailmaker (Mack) their opinion about the sheets, and in particular if I should use a less stretchy higher-tech line. Their response was something to the effect that there were large, and varying forces acting on the rig/sail/sheets, that when the sheets stretch they were absorbing that extra energy would otherwise be taken up somewhere and that I should stick with double braid.