second Dyneema failure

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gminkovsky
Posts: 211
Joined: Wed 01 Nov 06, 19:58
Your Country: USA, Long Island Sound

second Dyneema failure

Post by gminkovsky »

I have recently experienced my second failure of Dyneema rope. The first one was my main halyard that I described a few years ago. The second is my Board Downhaul line.

My board is somewhat difficult to dislodge initially. So often, I put the downhaul line on a winch and give it a light tug. Then I pull by hand. When the line is on the winch it touches and rubs on the rope clutch. So the cover had MINOR wear. Well, the line just failed with a minor pull.

I think that if Dyneema has compression damage and the cover gets minor damage, the rope is shot! Even a little UV kills the dyneema fibers inside.

For now, I tied the two parts with a sheet bend - works fine, but I will replace the line during winter.

I am very disappointed in this material. I never had this kind of failure with plain polyester, nylon or other high-tech rope.
Mika Harju
Posts: 218
Joined: Thu 02 Nov 06, 13:19
Your Country: Finland, Turku

Re: second Dyneema failure

Post by Mika Harju »

gminkovsky wrote: I think that if Dyneema has compression damage and the cover gets minor damage, the rope is shot! Even a little UV kills the dyneema fibers inside.
Dyneema has excllent UV resistance. This is from Dyneema Technical Specification:
Optical properties.
Dyneema® fi bers are visually opaque.
The fi ber is invisible to an UV-light source due to the low
UV absorption coeffi cient in combination with no
fl uorescence or phosphorescence.

http://www.dsm.com/products/dyneema/en_ ... loads.html
Mika Harju
DF1000 Racing #8
gminkovsky
Posts: 211
Joined: Wed 01 Nov 06, 19:58
Your Country: USA, Long Island Sound

Post by gminkovsky »

What are other reasonable explanations for the failure of my main halyard and the board downhaul line?

Both had compression loads over a short line span. However, my downhaul never had any significant overall load on the part of the line that failed! My halyard had damage to the cover. The downhaul had very slight chafing - nothing that would make me even consider replacing the line.

Both ropes look like cotton balls torn apart with loose fibers sticking out.

It almost looks like the cover is what had all of the strength, and the core is just filler that does not provide any load bearing. I see plenty of ropes like that sold in home improvement stores.
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