[Amel Yacht Owners] Genoa sheet broke under sail - looking for recommendations for replacement [1 Attachment]


Thomas Peacock
 

I’ve never had a jib sheet break, but have had them fray over the years. Last year we replaced our sheets with New England Ropes Regatta single-braid 12 strand, 5/8 inch (16 mm), breaking strength of 12,400 pounds (5600 kg). 

It’s a great rope, very nice on the hands. Not sure of its availability in Europe. About 5.30 US$ per meter.

My sense is that there was something peculiar in your sheet, rather than having an understrength line, but I’m way out on a limb on that. Did it fail at the bowline, or elsewhere? A knot tends to be the weakest part of any line.

Tom Peacock
SM 2000 #240  Aletes
Rock Hall, Maryland


On Aug 9, 2017, at 5:17 PM, svperegrinus@... [amelyachtowners] <amelyachtowners@...> wrote:

[Attachment(s) from svperegrinus@... [amelyachtowners] included below]

Hello, our jib sheet broke during a gust to 39 knots apparent while close-hauled under full genoa, while sailing from Delos to Kea.  The breaking point was the block on the car on the genoa track.  No evidence of chafe was found on the broken line nor on its twin on the starboard side.

Brand: Alpha Ropes
Model: Cruiser 24 Kmix
Breaking strength: 5,500 kg / 12,125 lb
Core: Braided 16 strand HT Polyester core
Cover: 24 braid mix HT Polyester / Cordura
Date installed: April 2014, reversed March 2016
Miles sailed: 15,000
Genoa size: 54 sq m

This line was very easy on the hands, but was not much appreciated here in the Med where winds are continuously variable because it was rather stretchy, requiring constant winch adjustment.

On the other hand, not sure if the replacement should be a less stretchy rope, as it seems it would be harsh on the hardware?  Or is that not a factor?

Comments, suggestions, questions much appreciated in advance.  Best,


Peregrinus
SM2K N. 350 (2002)

At anchor, Vourkari, Kea





svperegrinus@yahoo.com
 

Thank you Bill, Bill, Paul and Tom for your recommendations.

The port jib sheet broke at the block on the car on the genoa track, 1.96 meters away from its whipping and 1.6 meters away from the tension point on its knot at the sail clew.  The wind gust went from about 15 knots apparent to 39 knots apparent in about one minute.  The boat remained perfectly under control even as it leaned heavily.

Looking at how well the cover looks, I am reminded the section of the rope that includes the break point was never used until we reversed the lines in March 2016; i.e., it only had 16 month's use.   The reason is that these jib sheets were a couple of meters too long, to the point I can actually whip the failed end and continue using the broken sheet perfectly OK from a length perspective (not that I am going to!).  For the first two years of use, the section that broke never had any tension applied to it and it stayed largely in the shade, and mostly dry.

For the time being, we are using as replacement one of the old jib sheets we discarded back in 2014.  It is white with speckled red and I suspect it might be an Amel factory original.  It is very rough, but as we already sailed about 4 hours with it, it is grippy on the hand and feels more substantial than the silky Alpha Ropes that broke.  

BTW, Alpha Ropes recommends the "Cruiser 24 Kmix" for jib sheets, so we were using a line advertised as fit for purpose.

 Cheers,

Peregrinus
SM2K Nr. 350
At anchor, Vourkari (Cyclades)





---In amelyachtowners@..., <peacock8491@...> wrote :

I’ve never had a jib sheet break, but have had them fray over the years. Last year we replaced our sheets with New England Ropes Regatta single-braid 12 strand, 5/8 inch (16 mm), breaking strength of 12,400 pounds (5600 kg). 

It’s a great rope, very nice on the hands. Not sure of its availability in Europe. About 5.30 US$ per meter.

My sense is that there was something peculiar in your sheet, rather than having an understrength line, but I’m way out on a limb on that. Did it fail at the bowline, or elsewhere? A knot tends to be the weakest part of any line.

Tom Peacock
SM 2000 #240  Aletes
Rock Hall, Maryland


On Aug 9, 2017, at 5:17 PM, svperegrinus@... [amelyachtowners] <amelyachtowners@...> wrote:

[Attachment(s) from svperegrinus@... [amelyachtowners] included below]

Hello, our jib sheet broke during a gust to 39 knots apparent while close-hauled under full genoa, while sailing from Delos to Kea.  The breaking point was the block on the car on the genoa track.  No evidence of chafe was found on the broken line nor on its twin on the starboard side.

Brand: Alpha Ropes
Model: Cruiser 24 Kmix
Breaking strength: 5,500 kg / 12,125 lb
Core: Braided 16 strand HT Polyester core
Cover: 24 braid mix HT Polyester / Cordura
Date installed: April 2014, reversed March 2016
Miles sailed: 15,000
Genoa size: 54 sq m

This line was very easy on the hands, but was not much appreciated here in the Med where winds are continuously variable because it was rather stretchy, requiring constant winch adjustment.

On the other hand, not sure if the replacement should be a less stretchy rope, as it seems it would be harsh on the hardware?  Or is that not a factor?

Comments, suggestions, questions much appreciated in advance.  Best,


Peregrinus
SM2K N. 350 (2002)

At anchor, Vourkari, Kea





Alexandre Uster von Baar
 

Good morning Francisco,

Sorry to read about your issues.
5.500kg / 12.000 lbs breaking point seems a bit small to me, but I am not an expert.

Mine was changed in 2013, I did not find the invoice, all I remember I paid a little over $1000 for it (one line going from one side to the other), the breaking point is 36.000 lbs, I beleive made of dyneema with a cover which is repairable. Same diameter as the original one.

Sincerely, Alexandre
SM2K #289 NIKIMAT
Port de Plaisance de Gustavia, Saint Barthélémy, FWI



--------------------------------------------

On Wed, 8/9/17, svperegrinus@yahoo.com [amelyachtowners] <amelyachtowners@yahoogroups.com> wrote:

Subject: [Amel Yacht Owners] Genoa sheet broke under sail - looking for recommendations for replacement [1 Attachment]
To: amelyachtowners@yahoogroups.com
Date: Wednesday, August 9, 2017, 4:17 PM


 









[Attachment(s) from
svperegrinus@yahoo.com [amelyachtowners] included
below]


Hello, our jib sheet broke
during a gust to 39 knots apparent while close-hauled under
full genoa, while sailing from Delos to Kea.  The breaking point was the
block on the car on the genoa track.  No evidence of chafe was found
on the broken line nor on its twin on the starboard
side.

Brand:
Alpha RopesModel:
Cruiser 24 KmixBreaking
strength: 5,500 kg / 12,125 lbCore:
Braided 16 strand HT Polyester coreCover:
24 braid mix HT Polyester / CorduraDate
installed: April 2014, reversed March 2016Miles
sailed: 15,000Genoa
size: 54 sq m
This
line was very easy on the hands, but was not much
appreciated here in the Med where winds are continuously
variable because it was rather stretchy, requiring constant
winch adjustment.
On
the other hand, not sure if the replacement should be a less
stretchy rope, as it seems it would be harsh on the
hardware?  Or is that not a factor?
Comments,
suggestions, questions much appreciated in advance. 
Best,

PeregrinusSM2K
N. 350 (2002)


greatketch@...
 

This is WAY more information on jib sheets than any sane person could want...  but we are sailors, so by definition our sanity is suspect!

Let's refresh our memory about what the original factory spec for Super Maramu Jib sheets was from Amel:

16mm (~5/8 inch) polyester double braid.  Nothing fancy.  Amel used low-stretch exotics on their boats where it mattered, and avoided them where it did not.  

Line of this type, at best, has a typical breaking strength of 16,000 lbs, and 41 meters of it will cost about $350.  There is no need for the strength (and cost!) of dyneema in this application.  The reason to spend money on exotics like dyneema is they allow you to downsize the line, keep the strength and lose the weight, OR keep the size and reduce stretch to a bare minimum.  Neither is something we really care about in this application.

Just to put us in the ballpark for what we need, Harken has published a formula for estimating the genoa sheet load based on sail size and wind strength.  

SL = SA x V2 x 0.00431
   SL = Sheet load in pounds
   SA = Sail area in square feet
   V = Wind speed in knots.

For a 700 square foot genoa, fully out, in 40 knots of wind, the predicted sheet loads are about 4800 pounds.  50 knots bumps this up to 7500 pounds, and I very much doubt the sail itself is strong enough for much past that.

It is important to understand that jib sheets are not (usually) selected based on breaking strength.  They are selected for ease in handling, and for most boats, anything that is big enough to handle comfortably is way, way, more than strong enough.

Certainly if you want to use something bigger than this because it is comfortable to handle, go ahead--it's not a huge deal. But understand that bigger lines do have a cost other than just money.  The extra weight means the sail take more wind to "fly" and it will cut the boat's light air performance.  

Anytime a line breaks in the middle, we can assume there was a reason other than simple load.  It might have chaffed or damaged in some way, there might be a manufacturing defect, it might have come tight against a sharp edge.  I can say this with confidence, because even the best tied bowline will reduce the strength of the line by at least 40%, and will ALWAYS be the weak point.  With exotics (dyneema, spectra, etc) the knots are an even tougher problem.  The lines are "slippery" and don't take to the crushing loads in a knot well at all.  To keep anywhere near the full strength, they need to be spliced.  If you tie a knot, it's likely you don't have any more real world strength than you would have had with a polyester double braid!

For what it is worth, I do not use a bowline on my jib sheets, rather I use a single length, and larks head the line to the clew of the sail.  It is not any stronger, but it never hangs up on the shrouds on a tack.  You can't always do this with exotic lines because they can be slippery enough they slide under heavy load.

Bill Kinney
SM160, Harmonie
Bar Harbor, Maine.


svperegrinus@yahoo.com
 

Hello Bill Kinney,

Thank you for your detailed and informative post.

My broken line is 16mm polyester double braid.  Alpha Ropes states its breaking strength is 12,125 lbs.

This line broke at 39 knots apparent on a 54 sq m sail, so, per Harken's:

581 sq ft * 39kn ^2 * .00431 = 3,809 lbs

So my Alpha Ropes broke at 1/3 of its rated breaking load.

Possible causes you mention:

Tight against sharp edge: it broke at the turn of the block on top of the genoa car track.  This is an unmodified factory original Amel track car and block, used in several hundred Super Maramus.

Chafed or damaged: the cover on the broken line looks smooth and good as new.  Its twin on the other side looks smooth and good as new.  No detectable chafe.

Bowline:  the failed line broke 1.6 meters away from the tension point on its knot at the sail clew.

I am afraid this leaves "manufacturing defect" as the only other choice from your e-mail.

Oh well!  I guess no more Alpha Ropes for this boat!

Best,


Peregrinus
SM2K Nr. 350 (2002)
At anchor, Kea




---In amelyachtowners@..., <greatketch@...> wrote :

This is WAY more information on jib sheets than any sane person could want...  but we are sailors, so by definition our sanity is suspect!

Let's refresh our memory about what the original factory spec for Super Maramu Jib sheets was from Amel:

16mm (~5/8 inch) polyester double braid.  Nothing fancy.  Amel used low-stretch exotics on their boats where it mattered, and avoided them where it did not.  

Line of this type, at best, has a typical breaking strength of 16,000 lbs, and 41 meters of it will cost about $350.  There is no need for the strength (and cost!) of dyneema in this application.  The reason to spend money on exotics like dyneema is they allow you to downsize the line, keep the strength and lose the weight, OR keep the size and reduce stretch to a bare minimum.  Neither is something we really care about in this application.

Just to put us in the ballpark for what we need, Harken has published a formula for estimating the genoa sheet load based on sail size and wind strength.  

SL = SA x V2 x 0.00431
   SL = Sheet load in pounds
   SA = Sail area in square feet
   V = Wind speed in knots.

For a 700 square foot genoa, fully out, in 40 knots of wind, the predicted sheet loads are about 4800 pounds.  50 knots bumps this up to 7500 pounds, and I very much doubt the sail itself is strong enough for much past that.

It is important to understand that jib sheets are not (usually) selected based on breaking strength.  They are selected for ease in handling, and for most boats, anything that is big enough to handle comfortably is way, way, more than strong enough.

Certainly if you want to use something bigger than this because it is comfortable to handle, go ahead--it's not a huge deal. But understand that bigger lines do have a cost other than just money.  The extra weight means the sail take more wind to "fly" and it will cut the boat's light air performance.  

Anytime a line breaks in the middle, we can assume there was a reason other than simple load.  It might have chaffed or damaged in some way, there might be a manufacturing defect, it might have come tight against a sharp edge.  I can say this with confidence, because even the best tied bowline will reduce the strength of the line by at least 40%, and will ALWAYS be the weak point.  With exotics (dyneema, spectra, etc) the knots are an even tougher problem.  The lines are "slippery" and don't take to the crushing loads in a knot well at all.  To keep anywhere near the full strength, they need to be spliced.  If you tie a knot, it's likely you don't have any more real world strength than you would have had with a polyester double braid!

For what it is worth, I do not use a bowline on my jib sheets, rather I use a single length, and larks head the line to the clew of the sail.  It is not any stronger, but it never hangs up on the shrouds on a tack.  You can't always do this with exotic lines because they can be slippery enough they slide under heavy load.

Bill Kinney
SM160, Harmonie
Bar Harbor, Maine.


greatketch@...
 


One defect that can cause a relatively low load failure with double braid is an imbalance between the core and the cover.  With double braid line both carry the load, more or less equally.  If at some point during manufacture, or in handling afterwards, one becomes "slack" relative to the other, the load is no longer properly shared and premature failure can happen.

This does not happen with exotics, where the core is low stretch, high load material and the outer braid is just a sun and abrasion cover that has no significant contribution to the strength of the line.

Bill Kinney
SM160, Harmonie
Bar Harbor, Maine.