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Old 07-01-2019, 16:50   #1
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Polymeric Standing Rigging and Lightening Strikes

There have been a number of discussions concerning stainless steel versus UHMWPE (Spectra, Dyneema) use for standing rigging. One possible concern that I`ve thought about is the relative performance in the case of a lightening strike to the mast. The polymeric rigging will melt/decompose/burn at much lower temperatures than what would damage steel. On the other hand, the polymeric rigging is essentially electrically nonconductive.

Does anyone know how polymeric rigging fares in lightening strikes?
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Old 12-01-2019, 16:55   #2
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Re: Polymeric Standing Rigging and Lightening Strikes

Is it common for polyester lines and halyards to melt in a strike? If not, I suspect Dyneema rigging would fare fine as well. Has anyone measured how hot a mast gets when it's struck? How long does it stay hot? If it's raining, as is common during lightning events, perhaps the water would bleed off some of the heat.
Maybe Practical Sailor can put a stayed pole out until it gets struck, then destruction test the stays.
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Old 12-01-2019, 17:26   #3
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Re: Polymeric Standing Rigging and Lightening Strikes

Dyneema is a DSM product based on ultra high molecular weight polyethylene. However, like other polyethylenes it is not a good electrical conductor, which is why polyethyelene is often used for dielectric or electrical insultion purposes.

http://dynamicarope.com/wp-content/u...eema-Fibre.pdf
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Old 12-01-2019, 17:38   #4
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Re: Polymeric Standing Rigging and Lightening Strikes

Reducing lightning damage is all about getting the strike to flow out of the boat with low resistence. The mast and wire rigging are major paths for the strike. What happens when you remove the wires? Does a wet rope stay provide a higher resistence path that can heat up? Does the cone of protection still exist with rope stays for the boats occupants? It would be good to hear of some real strikes on rope boats to see what type of damage really occurs.
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Old 12-01-2019, 18:02   #5
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Re: Polymeric Standing Rigging and Lightening Strikes

Unless the chain plates are grounded--something I've never seen--I don't see them carrying much current. Additionally, compared to an aluminum mast, stainless is a very, very poor conductor. You would never try to conduct charge off the mast with stainless rigging. Because Deneema is non-conductive, there is less danger of heating along the strand. The charge should go down the mast.


I Googled "tower guy lightning" and several variants and found nothing useful, but they always have grounding down the mast.



Lightning is known for being quite unpredictable and defying rules.
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Old 12-01-2019, 18:31   #6
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Re: Polymeric Standing Rigging and Lightening Strikes

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Originally Posted by thinwater View Post
Unless the chain plates are grounded--something I've never seen--I don't see them carrying much current. Additionally, compared to an aluminum mast, stainless is a very, very poor conductor. You would never try to conduct charge off the mast with stainless rigging. Because Deneema is non-conductive, there is less danger of heating along the strand. The charge should go down the mast.


I Googled "tower guy lightning" and several variants and found nothing useful, but they always have grounding down the mast.



Lightning is known for being quite unpredictable and defying rules.
Surprised you've never seen chainplates connected to a lightning ground. Mine are. ABYC says to connect all large metal objects. If the chainplates are not connected to a lightning ground then you have the chance of the flow jumping to the water from the chainplate or bolts and doing damage.

While the wire maybe higher resistence than the mast, lightning is such a high voltage that it will flow through the wires, and pretty much anything metal.
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Old 12-01-2019, 23:58   #7
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Polymeric Standing Rigging and Lightening Strikes

High voltage doesn’t flow through anything to any degree, it flows over. As on the outside of the conductor not the inside.
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Old 13-01-2019, 02:06   #8
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Re: Polymeric Standing Rigging and Lightening Strikes

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Originally Posted by AKA-None View Post
High voltage doesn’t flow through anything to any degree, it flows over. As on the outside of the conductor not the inside.
Does that mean it is unlikely to damage synthetic rigging ?
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Old 13-01-2019, 23:23   #9
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Re: Polymeric Standing Rigging and Lightening Strikes

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Originally Posted by Paul L View Post
Surprised you've never seen chainplates connected to a lightning ground. Mine are. ABYC says to connect all large metal objects. If the chainplates are not connected to a lightning ground then you have the chance of the flow jumping to the water from the chainplate or bolts and doing damage.

While the wire maybe higher resistence than the mast, lightning is such a high voltage that it will flow through the wires, and pretty much anything metal.
So are mine
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Old Yesterday, 10:38   #10
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Re: Polymeric Standing Rigging and Lightening Strikes

It is hard to appreciate the power of lightning- it doesn't really act like regular electricity with which we are most familiar. That lightning bolt just jumped across thousands of feet of air which is generally considered a pretty decent insulator. It doesn't care much about conductivity. It's hot, like 30,000 degrees F- not much difference between melting metal and plastic at that temperature. The associated temperature is so great that the resultant air pressure change creates a sonic boom (thunder).
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