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Old 28-12-2019, 13:40   #46
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Re: Lightening...again

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Originally Posted by daletournier View Post
Almost no effort.

I've read much over the years on lightning, and I, like the poster above said, it's a "mystery ".

My boat has Marelon throughhulls so not bonded like many suggest.

Theres things I see that make me not sure what we know is correct, I've seen boats correctly bonded with ground plate etc get hit and I've seen non grounding boats get hit.

I figure in my situation a chain attached to my bow roller which is attached to my forestay theoretically gives a path of least resistance if I got hit, of course some will argue that path of least resistance attracts lightning while others would say it's a form of bonding doing away with the potential difference between mast and the water making the boat invisible to lightening? ( dont know if I worded that correctly).

Anyway, interested in thoughts.
My understanding, from little research is that grounding the boat might reduce the damage from a lightning strike, but at the same time might increase the probability of it happening.
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Old 28-12-2019, 19:12   #47
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Re: Lightening...again

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Originally Posted by Montanan View Post
From https://www.sailingscuttlebutt.com/2...tning-strikes/


Lightning Facts: An Analysis of Lightning Strikes
Published on February 19th, 2015
The odds of getting struck by lightning are about one in a million. But if you own a boat, the odds of it being struck by lightning are significantly higher – about one in a thousand. However, not all boats are created equal when it comes to lightning.

A just-released analysis of 10 years of insurance claims by Boat Owners Association of The United States (BoatUS) shows that certain boats are significantly more at risk than others. But which ones? And, what can you do if you’re caught on open water? BoatUS has some answers:

Let’s first state the obvious: It’s a no brainer why monohull sailboats with their tall masts pointing to the sky have significantly more lightning claims than powerboats – 3.8 chances per 1,000 versus a 0.1 chance in 1,000 for bass boats-runabouts-pontoons. The national average for the probability of a boat lightning strike claim for all types of boats and sizes is 0.9 chance per 1,000.

Size matters: It’s also not a stretch to understand why larger boats of all types – which present a larger target to the skies – are struck more often than smaller ones. A boat 40-65 feet in length has 6 chances per 1,000 while boats 16-25 feet have just a 0.2 chance per 1,000. Increasing the height of a sailboat mast from 35 to 45 feet nearly triples the odds of being hit.


Location matters, too: Where boating populations are dense and lightning is common, strike insurance claims are high. Six of the top 10 states in terms of frequency of lightning claims – Florida, Mississippi, Louisiana, Alabama, South Carolina and North Carolina – all lay within the thunderstorm hotspot in the Southeast and midsection of the country. Heading west, the frequency of lightning claims falls to about 1 chance in 10,000 along the Pacific Coast, or about 1/10th the national average.

The effect of two hulls: A multihull sailboat is almost twice as likely to have a lightning claim as a monohull. Why sailing cats get hit more is unclear, although theories include lack of a keel, more wetted surface, larger footprint, the dockage of cats at the outside edges of a marina, and higher average mast height.
Well, count me in with about five strikes immediately around me. I have always been at the helm which is not a coincidence. During a lighting storm underway the owner is usually at the helm.

My mast is ungrounded and sits upon a rotating ball joint which is a good insulator and dry. The dyneema lines would be very poor conductors even when wet.

Electrically the wires up the mast are quite thin, insulated, and certainly wouldn't conduct a large amount of juice.

Logically I think all of these elements combined make my mast a very poor choice for a direct strike versus simply striking the ocean directly. And this is my point.

Ultimately, the strike goes into the water so it is my experience that a very poor conductor arrangement might make your vessel safer. Perhaps instead of recommending grounding the mast and rigging we should all be doing the opposite.

It is not as if the lightning didn't attempt to use my vessel. Since my hands in a storm tend to be wet and I am using touching the well grounded wheel I have received several jolts large enough to sting my hands. Further the florescent cabin lights begin to glow. Once, the glowing didn't stop and I discovered the breaker managed to turn itself on. I can't explain that.

Despite jolts large enough to sting my hands I suffered zero electronic failures. This said I still kept backup computer and cell phone which both had maps and GPS inside the oven as an insurance policy.
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Old 28-12-2019, 19:35   #48
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Re: Lightening...again

1. Not all lightning strikes are created equally. Don't quote me on this but something like 50 or 60% have a peak current of less than 15,000 amps. While strikes with peak currents in excess of 200,000 amps have been recorded. 15,000 amps for a few microseconds is probably doable, 200,000 going to do some serious damage.


2. Don't think that you will find any knowledgeable people that would agree that grounding your mast increases the likelihood of being struck. Taking your mast down will decrease your probability of a hit, but then you are just a funny looking motorboat. But if you have convinced yourself otherwise it is a free country/world, have at it. Just don't add me to your guest list.


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Old 28-12-2019, 20:24   #49
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Re: Lightening...again

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Originally Posted by hernandobeach View Post
#1 Lightning is nature's version of a difference in potential. It is a charge (most are positive but some are negative)
Actually, no, most (95%) lightning is called "negative", as the charge in the bottom of the cloud is negative and the charge at the ground/sea is relatively positive. While this seems trivial, the rare "positive" lightning can be many times more powerful and far from the storm. NOAA has a quick description:
https://www.weather.gov/jetstream/positive
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Old 01-01-2020, 16:47   #50
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Re: Lightening...again

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Originally Posted by 44'cruisingcat View Post
My understanding, from little research is that grounding the boat might reduce the damage from a lightning strike, but at the same time might increase the probability of it happening.
My understanding as well. When we were doing the new Seawind build, they offered a grounding and lightening damage reduction system. At the time, they also furnished Aussie based study that said probably increased chance of being struck if in a lightening storm, vs being ungrounded. Which is why i chose not to have installed.
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Old 02-01-2020, 18:38   #51
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Re: Lightening...again

Thanks for that link, cyan.
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Old 03-01-2020, 05:21   #52
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Re: Lightening...again

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Originally Posted by pbmaise View Post
... My mast is ungrounded and sits upon a rotating ball joint which is a good insulator and dry. The dyneema lines would be very poor conductors even when wet.
... Perhaps instead of recommending grounding the mast and rigging we should all be doing the opposite...
ABSOLUTELY NOT!

Unfortunately, nothing on your boat is well insulated, ungrounded, or isolated, when it comes to lightning.


The dielectric strength of air is approximately 3 kV/mm. Its exact value varies with the shape and size of the electrodes, and increases with the pressure of the air.
Although air is normally an excellent insulator, when stressed by a sufficiently high voltage (an electric field of about 3 x 106 V/m or 3 kV/mm), air can begin to break down, becoming partially conductive (dielectric breakdown). Across relatively small gaps, breakdown voltage in air is a function of gap length times pressure. If the voltage is sufficiently high, complete electrical breakdown of the air will culminate in an electrical spark or an electric arc that bridges the entire gap. Lightning is an example of an immense spark that can be many miles long.

Excerpted from “ JetStream”, the National Weather Service Online Weather School: https://www.weather.gov/jetstream/
“Lightning” ➥ https://www.weather.gov/jetstream/lightning_intro


“... many positive strikes occur near the edge of the cloud or from the thunderstorm's anvil from which a strike can occur MORE THAN 25 MILES AWAY from precipitation...”
https://www.weather.gov/jetstream/positive (thanks for the link, cyan)

“... Lightning can strike be more than 10 miles away from location of rainfall...”
https://www.weather.gov/jetstream/lightning_safety



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Old 03-01-2020, 06:46   #53
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Re: Lightening...again

I assume that attaching a copper line to connect an aluminum mast to the water is a temporary setup when lightning is expected.

Wouldn’t this lead to galvanic corrosion if left in place for any length of time?
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Old 03-01-2020, 07:46   #54
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Re: Lightening...again

For years I have used tinned copper lugs for the mast connection. Coat the connection with a compound intended for aluminum wire (Alnox). Check it every 5 or so years, add some more Alnox, but looks fine before/ after.

The remainder of the system is copper or silicon bronze.


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Old 03-01-2020, 08:44   #55
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Re: Lightening...again

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Originally Posted by BigNut View Post
No one has mentioned the EMP effect. We lost electronics that were not on or even connected to the electrical system - laptops, wireless mice, drone, and the weirdest thing I still have no explanation for: 2 popcorn air poppers, both unplugged. (I still can’t think this one through, and I was too embarrassed to report them to the insurance company. It just seemed ridiculous)
Things don’t fail all at once either. It is good to wait before finalizing with the insurance company.
All that damage is from sympathetic transient voltage spikes, not EMP.

Most damage done by lightning is this type of damage rather than a direct strike.

Short of hiding everything in a sealed metal box there is no way to protect against it.
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Old 12-05-2020, 07:30   #56
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Re: Lightening...again

Jeff Thayer has the best discussion I've heard about lightning: https://www.59-north.com/onthewindpo...90-jeff-thayer

Since you have an hour to kill...

...now go buy some aluminum foil...

...but don't feel smug in your expensive aluminum yacht.

And you might show some love for 59-north.
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Old 12-05-2020, 07:56   #57
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Re: Lightening...again

If you get a chance .. check out the Talos Lightning Detectors at:

https://www.pmt-fl.com/talos/lightni...talos-sfd-1000

Can detect lightning up to 25 miles away .. ask for the Cruiser Forum Discount. Provides Situational Awareness ..
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