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Old 21-06-2017, 19:15   #16
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Re: Copper ground plate lighting electrode

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Originally Posted by russell1952 View Post
I put 2 ground plates on my cat one for the SSB radio and one on the other hull for protection, they get some growth but comes off easily. The function of the plate is not to conduct lightning to ground but to lower the electrical potential difference of the boat so it is less of a target.
On my boat the function of the lightning bonding and ground plate is to give a clear path to the water for a lightning strike.
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Old 21-06-2017, 20:18   #17
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Re: Copper ground plate lighting electrode

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Originally Posted by captainwireman View Post
Will the copper in the plate prevent marine growth or does it need regular cleaning? How about securing a length of bare copper wire under the waterline and securing this to the standing rigging backstays?
I was thinking of making up a heavy gauge wire long enough to attach one end to the base of the mast and the other end attached to a steel plate to drop over the side if in a lightning storm. Would this be effective to protect the boat if hit by lightning? Any suggestions or ideas? Yes, No. Better ways?
Thanks
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Old 21-06-2017, 20:31   #18
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Re: Copper ground plate lighting electrode

I know of a number of classic wooden boats with copper "ground planes" on the bottom. Some as large as 4'X4' with a threaded copper lug in the center to attach a 1/4" single strand wire that led to the main electrical buss. All electronic devices using R/F energy to transmit or receive were grounded to this buss. The boat owners claimed greatly improved performance and that this was common practice on vintage boats.
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Old 22-06-2017, 00:00   #19
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Re: Copper ground plate lighting electrode

The average lighting strike produces between 5000 and 50000 amps with a average of 20000 amps, it will not matter what sort of ground you have it will be destroyed if hit, the function of a ground plate is to reduce the chance of being hit.
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Old 22-06-2017, 00:28   #20
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Re: Copper ground plate lighting electrode

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Originally Posted by russell1952 View Post
The average lighting strike produces between 5000 and 50000 amps with a average of 20000 amps, it will not matter what sort of ground you have it will be destroyed if hit, the function of a ground plate is to reduce the chance of being hit.
Others disgree with your statement
Striking Lightning Facts - Seaworthy Magazine - BoatUS
Quote:
. The general consensus is, you can't do much to keep your boat from being struck. The ultimate act of God, remember, though God seems to have it in for sailboats and doubly so for multihull sailboats. But lightning protection systems can help to minimize the damage if your boat does get struck,
Marine Lightning Protection Inc.
Quote:
. This standard is based on the simple concept that a boat should be protected the same as a building, with the lightning conductors on the outside rather than through the middle of the boat.
Modern Lightning Protection On Recreational Watercraft - Seaworthy Magazine - BoatUS
Quote:
. This is a basic concept that surprises many boaters: A lightning-protection system is not designed to prevent a lightning strike, but rather to provide a safe discharge path for the lightning
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Old 22-06-2017, 06:11   #21
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Re: Copper ground plate lighting electrode

Hundreds of tall structures are the recipient lightning strikes each day and the protective lightning system (lightning rods and down conductors) safely conducts the strike energy to ground. The very short duration (on the order of one millionth of a second) of the current flow is what reduces this to a manageable problem.

Don't think any knowledgeable individuals would buy into the idea about the ground plate maintaining the ships potential/ mast tip at the same level as the surrounding ocean surface and thereby reduce the probability of a strike.

Location and relative height of the structure to its surrounding is the single biggest determination of the likely hood of a strike.
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Old 22-06-2017, 11:03   #22
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Re: Copper ground plate lighting electrode

Hello to all,
Commenting on-line about lightning, and lightning and boats, isn't as controversial as "guns" or even "anchors", as there actually is peer-reviewed scientific research / data, test results, etc. available, as well as actual real-world officially-compiled statistics published about sailboats and lightning!!

(why, so few sailors will read these papers / articles, and some that will refuse to believe the facts...well, that's a mystery to me....but, oh well, that is life!)

Paul gave you all direct links to articles written for sailors (and lots of info from a company designing protection systems), all based on the definitive work done by the Univ of Florida, and their continued research from their Lightning Research Lab....
If you read these articles, and the supporting material, you will quickly see that it isn't some "black art", but actual science...
Yes, mother nature is unpredictable....but you can still protect yourself from injury and protect your boat from damage (and even have some protection for electronics), even if you take a direct strike, by following the simple rules/procedures...

BTW, while I'm usually loath to promote businesses as sources of factual info, in the case of "Marine Lightning Protection, Inc.", I'm making an exception....they are good people, design and sell good products....and even if you never buy anything from them, read their website, you'll learn a LOT!
Their founder, Dr. Ewen Thomson did the original and definitive research on "lightning and boats" 25 years ago (when a professor at Univ of Florida)...

I'm not going to attempt to re-write Beth's words here (she's a great writer!)....I'm just going to reinforce the direction that Paul gave you all....go and read those articles, papers, sites....



FYI, I've taken a direct strike to the masthead and VHF antennas of my current boat, and except for destroyed VHF antenna and damaged VHF Radio, SSB remote tuner, and a few other minor devices, no major damage....BUT...
But, I rewired all electronics (and all mast wiring) and did a complete electronics upgrade at that time, as I wasn't going to trust the mostly 6 - 7 yr old electronics after the strike!!
{Also, I've take direct strikes to my ham radio tower at home, with no damage at all....and every year I take many, many (~ 100 each summer!!) direct strikes to my ham radio repeater tower (1368' above ground), with no major damage (phones lines blown out twice in 25 years, but that's a phone company issue)...}
Many cellular phone towers (even though most are 150' high or less) get struck multiple times a year, with little to no damage...
Fact is, if you can afford the time and money, you can do a lot to protect yourself, and your boat, from damage....(and even some protection to your electronics)



Read those articles and papers...
Fair winds...

John
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Old 22-06-2017, 11:11   #23
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Re: Copper ground plate lighting electrode

Quote:
Originally Posted by russell1952 View Post
The average lighting strike produces between 5000 and 50000 amps with a average of 20000 amps, it will not matter what sort of ground you have it will be destroyed if hit, the function of a ground plate is to reduce the chance of being hit.
Some statistics show that sailboats with lightning protection get hit more often than those without but the damage to the ones with lightning protection is far less.
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Old 22-06-2017, 11:24   #24
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Re: Copper ground plate lighting electrode

thomm,
Those statistics you mention about sailboats with lightning protection systems getting hit more often, are contrary to the published findings of insurance companies and scientific researchers...which clearly show a slight advantage in having a lightning protection system, not a huge advantage by any sense, just very slight advantage.
Quote:
Originally Posted by thomm225 View Post
Some statistics show that sailboats with lightning protection get hit more often than those without but the damage to the ones with lightning protection is far less.
Can you cite where your statistics come from??

Thanks.

John
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Old 22-06-2017, 11:30   #25
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Re: Copper ground plate lighting electrode

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Originally Posted by ka4wja View Post
thomm,
Those statistics you mention about sailboats with lightning protection systems getting hit more often, are contrary to the published findings of insurance companies and scientific researchers...which clearly show a slight advantage in having a lightning protection system, not a huge advantage by any sense, just very slight advantage.
Can you cite where these statistics come from??

Thanks.

John
I'll try and find where I read that.

I was thinking about it during this squall/storm I was in last month even though Bristol says in it's ad for my boat that the stays are "grounded." I have seen no wires going from any of the stays say to the keel.

I have also removed the diesel that was in my boat and all the "grounds" that used to go to the engine and out to the prop etc now just go back to the battery negative.

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Old 22-06-2017, 11:48   #26
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Re: Copper ground plate lighting electrode

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Originally Posted by ka4wja View Post
thomm,
Those statistics you mention about sailboats with lightning protection systems getting hit more often, are contrary to the published findings of insurance companies and scientific researchers...which clearly show a slight advantage in having a lightning protection system, not a huge advantage by any sense, just very slight advantage.
Can you cite where your statistics come from??

Thanks.

John
I found several that said that. Here are two articles that explains that argument (of going without protection)

Also I found stats that said multihulls get struck almost twice as often as monohulls. (last link)

Lightning Strike! - SailNet Community

(in the link below it's in the section How Do We Protect Ourselves)

http://www.frugal-mariner.com/Lightn...your_boat.html

Striking Lightning Facts - Seaworthy Magazine - BoatUS
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Old 22-06-2017, 13:18   #27
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Re: Copper ground plate lighting electrode

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Originally Posted by Diesel Bill View Post
I was thinking of making up a heavy gauge wire long enough to attach one end to the base of the mast and the other end attached to a steel plate to drop over the side if in a lightning storm. Would this be effective to protect the boat if hit by lightning? Any suggestions or ideas? Yes, No. Better ways?
Thanks
I was wondering about this as well. In my case, trailer sailor, I'm normally not out in "storms." So never really thought about lighting protection or what not. However, I am taking a two week vacation and sailing the Gulf of MX (MS barrier islands). I will have a slip, save for a couple of over nights off the islands. Nevertheless, if I'm in a slip or anchored out, would this help? Hurt? What is the best thing to do if a lighting storm moves in?
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Old 22-06-2017, 13:49   #28
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Re: Copper ground plate lighting electrode

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Originally Posted by russell1952 View Post
The average lighting strike produces between 5000 and 50000 amps with a average of 20000 amps, it will not matter what sort of ground you have it will be destroyed if hit, the function of a ground plate is to reduce the chance of being hit.
Plus one
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Old 22-06-2017, 14:39   #29
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Re: Copper ground plate lighting electrode

My boat has been struck twice (thanks BoatUS) and I been struck once while working on a boat. That boat was on the hard and I was working on a grounded hull valve. The sky was blue, with just a few dark clouds on the horizon. The very first sound of thunder, I was getting thrown across the forepeak. There was a green arc coming off my wrench to the hull valve. The arc stretch 3 feet, as I was slam across the boat. My heart was beating so fast, felt like it was coming out of my chest. I looked around the boat and found a hot beer, to calm my nerves. When I came off the boat a hour later, one of the yard workers ask if I was on the boat when it was hit. Said he saw it hit the mast, then the boat shed. Boats can be hit/damaged many different ways, electromagnetic pulse (EMP), from lightning hitting the water, thru a shore cable connected to the boat or the most common antenna/mast hit. A ground plate would only help a close water hit to enter the boat. We're talking about energy that can travel over 5-7 miles thru air, where it wants to go is where it's going.

I've also seen a boat sink 30 sec after being struck. As an electrical engineer and boat owner who has seen the damage, I'm going to follow this tread. I'm in the camp, my boat is grounded to lead keel and engine, no ground plate, no static dissipater, everything that can be disconnected is, also I verify boat's grounding system annually.
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Old 23-06-2017, 11:01   #30
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Re: Copper ground plate lighting electrode

thomm,
Not going to dredge up lots of discussion here, as it will just breed controversy...and might get out-of-hand...
Besides I got a LOT to do today!!

But, in a nutshell, my reading of these links is similar to the recommendations from many boat manufacturers, where because of legal liability hedge and make statements about "different schools of thought" and "some studies have shown", etc...

The fact is that these articles hedge when it comes to using/recommending the long-established, scientific research and recommendations....
Quote:
Originally Posted by thomm225 View Post
I found several that said that. Here are two articles that explains that argument (of going without protection)

Also I found stats that said multihulls get struck almost twice as often as monohulls. (last link)

Lightning Strike! - SailNet Community

(in the link below it's in the section How Do We Protect Ourselves)

Protecting your boat from lightning.

Striking Lightning Facts - Seaworthy Magazine - BoatUS
The facts are easy to see in the Univ of Florida studies, as well as that done for BoatUS, etc. (and numerous studies / real-world data, from shore-side radio / phone towers, etc.), that proper grounding / lightning protection does not increase the likelihood of getting struck!!
Rather it provides a slight (very slight, depending on your interpretation) advantage in slightly reducing the likelihood of a strike...

Yes, I understand that this contrary to what some think and contrary to some info presented on-line....but, this is nonetheless true!


Again, I'm not going to debate this here....I've been doing this (debating lightning and grounding) for ~ 40 years on land (and dozens of years at sea), and while as I said earlier, this isn't as controversial and "guns" or "anchors", it still gets heated at times...


Fair winds...
And, thanks for pointing me to more weird articles....

John
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