Two broken jib sheets within 5 minutes of each other!

[danstanford]

Best race start of the year right on the line on time and second over from the boat end of the line, and bam the port jib sheet snapped somewhere around the block on the job track. I was pinned and unable to tack due to the boat to starboard so we fixed the sheet, got up some speed, tacked and bam the starboard sheet broke. Admittedly the sheets looked a little worn but certainly nothing terrible, and we were sheeting hard in 12 to 15 knots with my big new jib, but wow what a shock!
I certainly do understand that things fail eventually and almost always at the worst times, but I am absolutely shocked that the other sheet failed within minutes of the first.
This is certainly a warning to look at the other lines, some of which look worse than these sheets did.

Dan

 

[jviss]

At least you can say the sheet material, or perhaps the wear pattern, are very consistent.

How about some background? What make, how old, exposed to UV a lot, etc.? What did the failure point look like - signs of chafe?

Thanks.

 

[dlochner]

Well, that will catch your attention.

 

[danstanford]

At least you can say the sheet material, or perhaps the wear pattern, are very consistent.

How about some background? What make, how old, exposed to UV a lot, etc.? What did the failure point look like - signs of chafe?

Thanks.

And I can say that I don't favour one tack over the other! I am not sure how old the sheets are as I have only had the boat for three years, but they may be original for all I know and the boat is a 2007. The outer covers looked fine and they weren't stiff or looking bleached out. They do see steady UV but only for the 5 months a year that they are on as the boat is covered all winter. I pull the jib sheets out of the blocks and coil them on the pulpit whenever I wash the deck and I never noticed any chafe as I coiled them.
Dan

 

[31seahorse]

"Oh, Sheet !!!! There goes the other one! I can't understand it; they can't be more than ten years old. They just don't make things to last!"

 

[dlochner]

Sounds like the core failed. There can be a lot of internal friction inside the core that can cause failure. The point of highest friction will be where the sheet goes through the fairlead, here it makes a fairly sharp bend at the point of its maximum tension. The stretching and working of the rope heats the core, a strand or two start to fail and then the last straw (strand) gives way and the sheet can no longer carry the load. The core of the rope carries most of the load, the cover is just there to protect the core and keep it warm.

The easiest way to extend the life of the sheet is to end for the end the sheets periodically. This will change the location of the maximum load and reduce the fatigue factor in a specific part of the line. Another option is to increase the size of the sheave that the sheet goes around. A larger diameter will make for a gentler bend and less stress and point loading on the sheet.

 

[danstanford]

"Oh, Sheet !!!! There goes the other one! I can't understand it; they can't be more than ten years old. They just don't make things to last!"

Good one Sea, I sure wish I knew what was going to be next....because there are a lot of 10 year old things on this boat!

 

[Jackdaw]

Headsail sheets on non-overlapping rigs take a lot of strain and wear. They turn at the deck at tight angles, and upwind are often trimmed in the same place, creating additional wear.

 

[kloudie1]

Additionally, we don't know the material that the sheets were made of.

 

[Pirate Dave]

Replace them!!!! Those lines sound like pieces of sheet

 

[Ron20324]

I see boats on my dock with the furling drum line cleated down, then the sheets are taut- dragged over the blocks and shrouds and whatever. I believe the sheets "take a set", having been bent at the same place for ... 10 years? I leave all my lines slack when at the slip.

 

[danstanford]

Pieces of sheet puns aside, these lines did not look bad though I take everybody's points about how they should have proactively been replaced. In fact, I have been upgrading lines according to risk management starting with my jib and main halyards.
Is no one else amazed at the chronology of the failure? This was twice or thrice weekly activity for these sheets since I have owned the boat and certainly no where near what should be termed abusive for them. Probably an actuary would have predicted the second failure and I would have replaced both today anyway, but I was blown away by the fact that they failed on successive uses in a huge lifespan.

What should I replace them with?

Dan

 

[jviss]

What should I replace them with?

I'm partial to New England Ropes Sta-set double braid. Ten or twelve years max if you leave them out during hte season (UV exposure), and end-for-end them annually.

 

[pateco]

 

[JRacer]

Brings back fond memories of the day that the bottom pintle on my J/24 rudder broke on the starting line. Was a known design weakness in the early boats at the time. 3-2-POW, boat rounds up and tacks. Fortunately I had carved a big enough hole between me and the only boat, a Cat 22, to weather. We miss his stern by inches and are now running parallel to the line and aimed squarely at the RC boat going full speed. Ease sails, in a panic, and miss the stern of the RC. I rode back to the dock straddling the rudder holding it upright with my feet and legs while one of the crew held the tiller. An exciting day, for sure!

 

[Jackdaw]

A good medium-tech Class-2 line for sheets is Sampson MLX. Low stretch and decent hand (a tricky combination).

 

[kloudie1]

I agree, either New England Sta-Set X or Sampson MLX .. both fine..I use the Sta-Set X .. I don't race (anymore) and the stuff does fine for me.. It stays in the sun year 'round ..

 

[SG]

Dan, I don't know what line material that you have. I've heard of hi-tech (not polyester) lines which get washed in chlorine bleach that become "toast" -- look great, but lost strength. High tech lines are tough, but don't like some chemicals.

What lines were you using?

 

[JohnShannon]

Did you just switch to a brand new big hi-tech jib? That will alter the stress picture. The newer sail fabrics have less give, so something else has to give.

 

[JohnShannon]

Another thing to consider, the stress on your sheets is sort of knowable. In the case of a jib sheet you can crank on your winch with say 50lbs of force, your linebacker child maybe 100lbs. Then the winch is a 40X or 50X means that you put 2000 lbs of tension on the sheet, your child using the big winch is at 5000 lbs.

A mainsheet is way less, you can pull 50 lbs so that is the stress on the line. If you have a 6x purchase then you are pulling on the boom with 300 lbs. Again dynamic loads will be more. I bet you could use stout twine for many mainsheets.

If you start looking at line you will find specs for stretch and breaking strength but this doesn't tell the whole story. Some of the new hi-tech line is what you might call "brittle" incredible strength but prone to destruction with shock loads.

New England rope ( i believe) had a nice little video showing a modern hi-tech line being loaded to 14,000 lbs before it popped. Then took that same line and dropped a 200 lb weight through 6 ft and it popped. Then they introduced their "hanging rope" or arborists rope and showed that it could absorb that kind of shock even though ultimate strength was lower.

So what, sadly it is hard to know, you end up going with the recommendation of the line supplier they split it down into causing, club racing, grand-prix racing with $$ amounts commensurate.

I am at present wondering about my main-halyard it is composite wire/rope the rope is Amsteel super strong super hi-tech. But in operation there is a halyard lock, a swaged on ball on the wire that engages something at the top of the mast. So in operation the super-hi-tech line is loose under no tension at all? and there is 8" of wire between the lock and head of the mainsail that is in tension. So I am wondering why that choice again it would seem stout twine/wire combo might have worked.