8mm spectra goes BANG. Sun degradation?

[toddedger]

Looking at the picture, that doesn't look like 12 strand dyneema braid to me. It looks like 12 strands of two, leading me to suspect that it was a blend of something.

Those of you with halyard breaks a foot from the end sound like you might have a tapering problem inside the splice. Hi load bending over a sheave with a not smoothly tapering tail in the splice could cause a major weakness

[Sailmonkey]

That looks exactly like our topping lift failure.

There was no real load on the 1/4” spectra, just 8 years of south Texas sun exposure. One day I went to the boat and found the boom Laying in the dodger. Exactly the same fraying and fuzzy.

I still have the line, I use sections of it for lashing inconsequential things.

[betwys1]

Spectra or Dyneema etc., are they Sun-degraded?

Not exactly, they have excellent UV resistance.
Trouble is these HDPE lines among their many virtues have a problem: lowest melting point of the synthetics - so get 'em hot, and watch 'em break!
See https://www.premiumropes.com/rope-advice/rope-materials
for example.

[s/v Jedi]

Originally Posted by betwys1

Spectra or Dyneema etc., are they Sun-degraded?

Not exactly, they have excellent UV resistance.
Trouble is these HDPE lines among their many virtues have a problem: lowest melting point of the synthetics - so get 'em hot, and watch 'em break!
See https://www.premiumropes.com/rope-advice/rope-materials
for example.

Exactly, they are just as UV resistant as polyester. Looking at the pictures I also think it’s not normal 12-strand Dyneema, probably a blend.

Where the low melting point comes into play is where the line is working in high tension, like the halyard sheave, winch, rope clutch etc. At those points an outer protective braid works well.

I never had any of the failures described and have used Dyneema intensively since 2004. I use Samsom Amsteel Blue, most of it 1/4” and add a 3/8” polyester braid from Yale cordage where needed. I also have 3/8” Amsteel Blue for runners that have been unprotected, in the tropics, are still good and were installed in 2004.

I also used lines with a blended core and had mixed results with that. They call them things like “Cruising Spectra” etc. and people think they get Dyneema

[Strung]

320kg - 700lb dinghy

Really?

[wingssail]

Originally Posted by toddedger

Those of you with halyard breaks a foot from the end sound like you might have a tapering problem inside the splice. Hi load bending over a sheave with a not smoothly tapering tail in the splice could cause a major weakness

This is the most interesting comment I've seen on this thread, as it is the only one with a hypothesis that fits my situation.

I will closely inspect the tapers where my splices end.

[jacksprat]

I have just had personal experience with this problem. The topping lift on my 26 ft twin keeler just snapped due to sun degradation. It was 8mm double grade line. In future I will be using the old 3 strand laid rope wherever I have ready access to the sheaves and when they are not of a too small radius. I know full well that this type of rope can jam between the sheave and cheeks.

[sails4fun]

Double Braid high strength line with a Dyneema Core is designed to be used as a double braid.
Core design is different than the 12 strand line that is single braid.
Performance will be affected when the cover is removed and the core is expected to do a job that is not part of the design.


So -when you want to use a single braid - buy a single braid.
Don't think you are going to get the same performance from a core removed from a double braid - even if the diameters are the same and the material is the same.

[Simi 60]

Originally Posted by Strung

320kg - 700lb dinghy

Really?

Yes really.
4.2m wide body , high side aluminium dory with electric and pull start 30hp, battery, auto bilge pump and usually 40litres of fuel.

[Simi 60]

Originally Posted by toddedger

Looking at the picture, that doesn't look like 12 strand dyneema braid to me. It looks like 12 strands of two, leading me to suspect that it was a blend of something.

8mm spectra as the thread title says

Those of you with halyard breaks a foot from the end sound like you might have a tapering problem inside the splice. Hi load bending over a sheave with a not smoothly tapering tail in the splice could cause a major weakness

I'd expect some weakness, like 10 or 20% loss (made up numbers) but in our situation we are talking about a 95% reduction.

[Kelkara]

Are you sure it was Spectra and not Vectran?


Vectran has similar strength and stretch properties to Spectra, but is much less UV resistant. the cover of the double-braid add considerably to the UV protection of the Vectran core ... so if you were using it without the cover, that might explain it.