Halyard Failure

[billknny]

Looking for thoughts on preventative maintenance for high tech halyards.

A bit of background. The boat is a J-105 in day charter service on San Francisco Bay. Used a lot (4+ days per week) and usually in our heavy winds (15-25 knots). The line in question is the main halyard, and I believe it was Yale's Vizzion of uncertain age, but more than 2 years.

We inspect the running rigging regularly, and have found that chafe has been a reliable indicator of need for replacement. Until now...

The halyard parted while hoisting the mainsail. Investigation found that it broke at the point where it is usually clamped in the rope clutch. There was no sign of external chafe or any damage to the cover at all, but... the line's core was totally crushed, and brittle with no tensile strength at all.

The scary part is that we had guys up the mast on this halyard three days before--with safety lines, of course, but still...

So my question... Is this something we should expect, but just have seen before? Should we put high tech halyards on a replacement interval irrespective of the physical inspection?

[Brion Toss]

Hi,
That is indeed scary. If the halyard is indeed Vizzion, it is a composite core, with non-structural polyolefin as filler for Vectran, which takes all the load. This halyard makes sense when you (a) want to save money, (b) still want HM performance, and (c) want a fatter, easier-to-handle line. But if you, say, replaced an all-HM core with this blend, and didn't change the diameter (because of "a", above), you'd have a halyard that was at best only half as strong as it used to be. And if, as so often happens on go-fasts, the original, all-HM core rope wasn't exactly oversized, you'll be putting a horrendous load on a relatively weak rope.
This is all speculation, of course, but you could confirm at least some of this by, wait for it, running the numbers on halyard load, and comparing the result with the strength of the rope you have.
It is not likely that the clutch is to blame, else you would have seen more chafe on the cover. But one other variable is how much tension is placed on the halyard by the crew; overtensioning would make things even worse.
So I don't think that a replacement schedule, by itself, would necessarily help, if the problem is that the rope is not up to the loads. Please get back to us about this.
Fair leads,
Brion Toss

[billknny]

The Vizzion that failed was 3/8", which compares reasonably well with the 9mm Spectra that is the boat designers spec. So I don't think it is a simple undersize issue.

I find it hard NOT to blame the clutch, since the core looked so bad ONLY in the area of the clutch. It literally crumbled in my hands, while a foot away it was fine. The fact that the cover looked unaffected is a mystery of the universe.

As for the crew possibly over-tensioning: this boat is in charter service. Whatever could possibly be done wrong has, I am sure, been done.

The part I find disturbing about this is that nobody would have condemned this line with a visual inspection. I obviously need to revisit my assumption that the cover tells me what I need to know about the condition of a high tech core

Originally Posted by Brion Toss

Hi,
That is indeed scary. If the halyard is indeed Vizzion, it is a composite core, with non-structural polyolefin as filler for Vectran, which takes all the load. This halyard makes sense when you (a) want to save money, (b) still want HM performance, and (c) want a fatter, easier-to-handle line. But if you, say, replaced an all-HM core with this blend, and didn't change the diameter (because of "a", above), you'd have a halyard that was at best only half as strong as it used to be. And if, as so often happens on go-fasts, the original, all-HM core rope wasn't exactly oversized, you'll be putting a horrendous load on a relatively weak rope.
This is all speculation, of course, but you could confirm at least some of this by, wait for it, running the numbers on halyard load, and comparing the result with the strength of the rope you have.
It is not likely that the clutch is to blame, else you would have seen more chafe on the cover. But one other variable is how much tension is placed on the halyard by the crew; overtensioning would make things even worse.
So I don't think that a replacement schedule, by itself, would necessarily help, if the problem is that the rope is not up to the loads. Please get back to us about this.
Fair leads,
Brion Toss

[Brion Toss]

Originally Posted by billknny

The Vizzion that failed was 3/8", which compares reasonably well with the 9mm Spectra that is the boat designers spec. So I don't think it is a simple undersize issue.

Even a covered 9mm rope with Spectra core will be about three times stronger than the same diameter Vizzion. I don't see that as "comparing reasonably well." In addition, the polyolefin filler fibers in the Vizzion won't be able to do their job (keeping the Vectran fibers from slicing each other) very well while being crushed by a clutch. I'm sticking with the idea that the rope is not up to the loads.
Fair leads,
Brion Toss

[allene]

Originally Posted by Brion Toss

Even a covered 9mm rope with Spectra core will be about three times stronger than the same diameter Vizzion. I don't see that as "comparing reasonably well." In addition, the polyolefin filler fibers in the Vizzion won't be able to do their job (keeping the Vectran fibers from slicing each other) very well while being crushed by a clutch. I'm sticking with the idea that the rope is not up to the loads.
Fair leads,
Brion Toss

3/8 Vizzion 4,300 pounds. 9mm Amsteel Blue 19,600 pounds. Not close.

That said I have been thinking about the clutch and how it holds. It puts pressure on the rope over some length or area. The friction over that length has to hold the load. The more square inches involved, the less force in pounds per square inch has to be put on the rope. Different clutches work in different ways but it might be worth looking at the clutch to see if the load is being spread correctly. If there is some part not doing its job such that the contact area is reduced that would greatly increase the crushing force on the line. The extreme example would be a knife which would have very low contact area and cut right through the line.

The other point is that straight spectra is not very good in a clutch because it has slightly less than half the friction for the same force from the clutch. It is recommended that it have a cover over the part in the clutch.

[Brion Toss]

Originally Posted by allene

3/8 Vizzion 4,300 pounds. 9mm Amsteel Blue 19,600 pounds. Not close.

I was assuming that the Spectra was in a cover; just the core of that rope would be about 3x stronger than the Vizzion. True, there might be something wrong with the clutch, but there wouldn't need to be.

Fair leads,
Brion Toss

[Dan Lehman]

Originally Posted by billknny

Used a lot (4+ days per week) and usually in our heavy winds (15-25 knots).

The line in question is the main halyard, and I believe it was Yale's Vizzion of uncertain age, but more than 2 years.

The halyard parted while hoisting the mainsail. Investigation found that it broke at the point where it is usually clamped in the rope clutch. There was no sign of external chafe or any damage to the cover at all, but... the line's core was totally crushed, and brittle with no tensile strength at all.

Did you examine the rope at some point(s) AWAY from the break?
--perhaps at any other point that might be thought to have some
higher-than-usual stresses?

Brion's question hits to the point of whether the line was overloaded,
and that should be something you guys can well figure per specs of
the boat. My take is that were we talking rockclimbing line here, the
frequency of usage would dictate retirement within a year, from use
in *leading* --moved to top-roping, where forces are much less--;
I'm unaware of what any like usage considerations obtain for yachting
uses. I do recall that in some flexing testing done by a climber for
the modern H-M materials (Kevlar, HMPE, Vectran) that were being
brought into climbing cord (typically 5-6mm accessory cord) the
Vectran cord proved not-so-good in strength in esp. with flexing.


Btw, in hoisting the main sail, wouldn't one expect the sheath alone
(polyester, in Vizzion) to be strong enough?!


--dl*
====