Dyneema versus wire.

[ex-Gladys]

How easily does dyneema cut? I ended up with some cast-off dinghy halyards in an unknown high-tech fibre a while ago, and despite being only about 4mm diameter they were a bugger to cut with a knife.

Pete

They would probably have been kevlar. Dyneema is only low modulus poly(ester?)

 

[macd]

They would probably have been kevlar. Dyneema is only low modulus poly(ester?)

Dyneema is Ultra-High Molecular Weight polyethylene (UHMwP), also known as high-modulus polyethylene, (HMPE). No idea what that means (although Wiki has a good stab at it).

(Unbonded) Kevlar isn't so bad to cut with scissors providing the blades are super-sharp and the fibres are under tension. I imagine Dyneema is similar, but it's a while since I had a go at it.

 

[GHA]

They would probably have been kevlar. Dyneema is only low modulus poly(ester?)

Dyneema is a bugger to cut as well, you'll get there with a brand new stanley blade pretty quickly but it's tough stuff. One of the uses is for cut resistant gloves..

http://www.dsm.com/products/dyneema/en_GB/industries/cut-resistant-gloves.html

 

[vyv_cox]

I have been testing Dyneema recently, amazing stuff. I cut quite a bit of it at the time, not easy but not terribly difficult.

 

[MagicalArmchair]

Thanks for resurrecting the thread! I am looking to do the lifelines on Triola and I was going to get a rigger in to make up wire without the plastic shielding (for fears of crevice corrosion). I was worried having bare wire would look a bit grim, now seeing this, I reckon Dyneema would be a better bet. Now to learn to splice...

 

[GHA]

. Now to learn to splice...

Splicing isn't too bad, bit fiddly the first couple of times you do the modified brommel.
Hollow fids are handy to have onboard but 12 strand 5 or 6mm you can do just with a stubby pencil and some pvc tape.

 

[MagicalArmchair]

Thanks for that, any preference on colour? White will get mucky pretty quickly, and I would have thought black would be more susceptible to UV?

 

[vyv_cox]

Thanks for that, any preference on colour? White will get mucky pretty quickly, and I would have thought black would be more susceptible to UV?

Dyneema seems very little affected by UV. My genoa sheets have been attached using the same Dyneema shackle for about five years now, in Greece. They are exposed to sunlight for about six months of each year. No deterioration that I can detect.

 

[rgarside]

Thanks for that, any preference on colour? White will get mucky pretty quickly, and I would have thought black would be more susceptible to UV?

I used grey [sometimes referred to as carbon]

 

[MagicalArmchair]

I need to measure the diameter of my current lifelines - is the accepted diameter 5mm for lifelines in Dyneema?

Galley swab below pointing at the current set up.

 

[macd]

I need to measure the diameter of my current lifelines - is the accepted diameter 5mm for lifelines in Dyneema?

If you check out the link in post #11, you'll find all you need to know and probably much more. From memory, the recommendation is 4, 5 or 6mm, depending on size of boat.

 

[vyv_cox]

5 mm Dyneema that I tested recently was failing at over 3 tons load.

 

[macd]

5 mm Dyneema that I tested recently was failing at over 3 tons load.

That's encouraging, Vyv. The 5mm stuff in rgarside's link (post #15) is specc'd at 2.6 tonnes, so the same ballpark.

Out of interest, what's the manner of its failure, and how would that compare with stainless wire?

 

[vyv_cox]

That's encouraging, Vyv. The 5mm stuff in rgarside's link (post #15) is specc'd at 2.6 tonnes, so the same ballpark.

Out of interest, what's the manner of its failure, and how would that compare with stainless wire?

It goes with a bang! A tensile overload that looks very like a multi-strand wire failure. Lots of individual strands of varying length.

 

[GHA]

Out of interest, what's the manner of its failure, and how would that compare with stainless wire?

At a guess , for the application being discussed, it would be a bent and twisted push/pullpit or maybe the lashings.

 

[PuffTheMagicDragon]

For what it's worth...

Anyone who is likely to take part in Offshore Racing, Category 2, should bear in mind that ISAF Offshore Special Regulations no longer allow the use of Dyneema (or similar lines) for lifelines. These are now required to be in stranded stainless steel wire with synthetic lanyard lashing being allowed as long as the secured gap is not longer than 100mm and that these are renewed annually. Note also that "All components of the lifeline enclosure system shall have a breaking strength no less than the lifeline".
Regarding the minimum diameter of the wire:
8.5m to 13m .................... 4mm
above 13m ....................... 5mm