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Old 06-02-2007, 08:48 AM   #1
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I have been thinking about and studying the topic. Here it has not been discussed recently.

Some sources say, "Lightning strikes somewhere on the surface of the earth about 100 times every second." ...OK boat in conductive salt water, linked to ground, stick in the air, stick in the air is likely metallic, stick in the air is the highest point in 12.5 NM in any visible direction, saying: "Pick me, Pick me" ......just asking for it.

Other Sources state that a typical cruiser has a fair to high probability of being struck at least once.

Surveyors often are called upon to inspect vessels damaged by it.

Some statistics say about half of the boats take some form of defensive measures.

What do you think, and do as a precaution?

For life, electronics, and vessel?
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Old 06-02-2007, 12:08 PM   #2
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Good luck - Here is study done in Fl several years ago. Nicely done by a Professor and he got paid for it.

http://www.thomson.ece.ufl.edu/lightning/

Still way to much hype for me to fully grasp it for a small boat. About the only sure thing that you can do is wrap all spairs in foil and when something goes you will have a spair.

I hope that you find something new.
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Old 06-02-2007, 12:28 PM   #3
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I have never been struck by lightning in a yacht ...... and I don't want to be. On the other hand, when I was third oficer on an 80,000 ton bulk carrier we were struck by lightning off the coast of Liberia.

There was an almighty bang, as if an explosion had taken place, and then nothing. That was it. Of course, the steel hull conducted the charge directly to earth/ground but we suffered no damage whatsoever except for both magnetic compasses. Prior to the strike their error had been maximum 5 degrees (after compensating for variation). After the strike they could be anything up to 180 degrees out. Of course the error was not constant either so they were totally unusable. We were on our way to Baltimore where we shipped new compasses on arrival. Thank God the gyros didn't go south on us too.

Makes you think though! What would you do. You are well out at sea. The compasses stop working for one reason or another and your GPS goes south. Nothing to indicate the course being steered. What would you do? Now I am digressing from the topic but it is worth considering.

As for me, I have a portable VHF, GPS and a compass which I keep in a metal box (Farraday's cage) and hope they will not become damaged. I have never used them yet but I also keep haevy cables which I clamp to the shrouds and keep the other end in the sea in the ope that any charge will dissipate that way.

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Old 06-02-2007, 02:10 PM   #4
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When we were in Singapore on Exit Only, our Privilege 39 Catamaran, there were five yachts struck by lightning in a single week in the Singapore Straits. Most of them lost all their electronics with the strikes.

It was a scary place to sail, and we were plagued by frequent thunderstorms until we arrived in Northern Malayasia - Langkawi. Although we have never been struck by lightning, we do carry two static electricity point discharge devices on the top of our mast. I don't know if they really work, but they make me feel better being up there.

I read in a cruising guide that each year, one out of a thousand boats get struck by lightning in the Bahamas. I can believe it, because there are afternoon thunderstorms nearly every day when I have cruised over there.

We always avoided lightning by changing our course when we were near a giant cumulonimbus cloud that was sending fingers of lighting down to the water. We found that by keeping a good watch, most of the time we could keep our distance from those monster thunderstorms. We made it more than 33,000 miles around the world without getting struck. I hope our good fortune continues.

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Old 06-02-2007, 03:18 PM   #5
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A friend of mine in Florida is a marine surveyor for insurance companies. He runs into this often especially with small non metal boats. The general rule is if there is a threat of a thunder storm don't go out or as soon as you hear the warning head to shore. Yes if your the tallest object around you take the chance of getting struck. The best thing to do is to make sure everything electrical is grounded properly into your boats protection system. If caught at sea the general rules apply. I am sure most of you file a float plan before departing on long trips just in case.
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Old 06-02-2007, 03:47 PM   #6
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Rather than reproduce it here, this is a link to our lightning strike: http://www.cruiser.co.za/hostmelon29.asp

sv Watermelon had a good bonding system, and was grounded.

We were on the Gulf of Thailand side of peninsular Malaysia, an area that we later learned is one of the worst places for electrical storms.

As I say in my log, I figured we were due to be hit. When we were sailing up the Pacific coast of Costa Rica, another place known for its hurricane season rain and lightning, we were in some horrendous electrical storms. Peter, with a more sanguine personality than mine, would say, "there's nothing we can do but ride it out. We'll see what happens." Although several times in our trip up and back down again we were in violent electrical storms with lightning crashing all around us, the lone sailboat in the area, we were not hit by lightning.

We met many boats that season that had been hit by lightning, the worst a trimaran anchored near Punta Arenas. Their mast was apparently not grounded, and so the lightning traveled down the shrouds to exit from the chain plates to the water, blowing holes in both amas on its way out, nearly sinking the boat. Everything electronic on their boat was destroyed by the lightning.

We saw a neighboring boat in a Malaysian marina get hit by lightning - the owners had left the boat and did not return in the time were were there, so I don't know what, if any, damage occurred on the boat.

Considering that in all the years we've been on the water in our boat, one lightning strike in all that time indicates that it is less likely than people fear. It makes me a bit sceptical of advertisements for lightning prevention gear for sailboats. I followed Lynx's link and it seems to confirm my own thoughts. To quote:

"Even if a device were effective in diverting the attachment spark, it would not be a good idea to mount it on the masthead as the attachment spark may start elsewhere on the boat or crew. The likelihood of lightning attaching to the masthead is a safety feature as far as the crew is concerned."

We've heard of boats who lost all their electronics even though they did not sustain a direct hit. Again, that doesn't surprise me that much. Peter figures that the electrical current in the water traveled to our SSB radio through the ground, for example. And the Man Overboard light, which was connected to nothing and was just hanging in our lazarette by a nylon line, was evidently damaged by the electical field. I still regret Peter's decision to replace our SEA ssb radio with an ICOM. I still believe that the SEA radio was better.

I've read of a boat that was sailing when it was hit by lightning (well, I think that was when they were hit), but every boat we've met that was hit by lightning was anchored or in a marina at the time of the incident. I wonder what that tells us?

I found the linked article to be very informative. Got any more, Lynx?
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Old 06-02-2007, 07:12 PM   #7
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I have been told that the best (and only) defense against lightning strikes is a:

GOOD INSURANCE POLICY!

Also, I hear that carbon fiber masts are particularly attractive lightning rods these days.
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Old 06-02-2007, 09:10 PM   #8
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Now I am totally confused. The grounding system in my boat was fully bonded by the original owner. There is nothing 'lightning specific' aloft but in the marina there is a connection from the bonding, directly to the seawater. I have never totally understood the physics behind lightning protection mainly because I have not really bothered to research it as well as I could have.

Darwin is Australia's, and one of the world's lightning hotspots with over 3000 hits at the Darwin Airport in one day last wet season. Yet, there has not been a case of a pleasure yacht taking a strike within Darwin harbour for just over 18 years.

A friend on a 32' catamaran copped a bolt off Mooloolaba about six years ago and lost most of his electronics. My attitude therefore is that lightning strikes are extremely rare and the microwave oven makes a good faraday cage (I think).

So I will sail on in blissful ignorance but will continue to toast both Neptune and Thor in the hope they will jointly recognise that I am a decent bloke, and worth protecting.

Salut Neptune (for the water)

Chin chin Thor (for the air) and, because he was so thoroughly grounded,

Campai Buddha.

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Old 06-02-2007, 11:26 PM   #9
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Greetings,

Every year I lose radio contact with some Mobile Maritimes as a result of Proximity Strikes - at least 20 - majority occurring in Lightening Alley - The Southern Malacca Straits into The Singapore Straights.

Besides losing the HF Radio - the VHF and most Electronics are damaged - Read :-

http://www.thomson.ece.ufl.edu/lightning/S...tion%20with%20a

This study , although done in Florida concludes that it is the electronics on board that are at the greatest risk from Proximity Strikes.

No deaths or injuries to crew as a result of lightning reported from cruising yachts to my knowledge in the last ten years. We have as many as a thousand cruising yachts in the waters of Malaysia - Singapore - Thailand alone, Thousands more in Northern Australia - Indonesia - Philippines.

Richard
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Old 06-03-2007, 12:55 AM   #10
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Here's my thinking with respect to lightning strikes and sailboats...now that I've been thinking about it.

Electrical Conductivity (S•m-1)

Silver 63.01 × 10^6 Highest electrical conductivity of any metal

Copper 59.6 × 10^6

Aluminium 37.8 × 10^6

Seawater 5

Drinking water 0.0005 to 0.05

Deionized water 5.5 × 10-6

So, Seawater is approximately 7 orders of magnitude less conductive than your typical mast and as such it provides excellent insulation. The surrounding air can achieve a high level of electrical conductivity through ionization to form a plasma when in the presence of a strong enough electric field. Therefore, it would seem that the only reason lightning would strike a boat would be that it has provided a less resistive path to ground than the surrounding water. Such a case would be in shallow water, at anchor or operating RF equipment (or all the above).

My understanding is that boats in a marina typically have a much lower likelihood of being struck by lightning because there are a large number of sailboat masts, electrically grounded by shorepower, all acting like lightning rods. The large number of lightning rods in a given area reduce the local electrical potential by slowly drawing current from the atmosphere and preventing the sudden discharge of electricity through a single ground source and lightning strike.

Therefore, I would theorize, that being at anchor in shallow water without neighboring anchored sailboats would greatly increase the probability of being struck. So, if you find yourself in a strong electrical storm, either find your way to a marina, or sail out to deep water and turn-off all of your RF equipment…don’t drop anchor.

Of course, I could very well be completely wrong
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Old 06-03-2007, 01:13 AM   #11
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Therefore, I would theorize, that being at anchor in shallow water without neighboring anchored sailboats would greatly increase the probability of being struck. So, if you find yourself in a strong electrical storm, either find your way to a marina, or sail out to deep water and turn-off all of your RF equipment…don't drop anchor.
Now, that fits in with those circumstances we've experienced. Where we were hit by lightning, we were the only boat at anchor in the bay.

Those many times we were sailing through HORRENDOUS electrical activity all around us, we weren't hit.

One of the boats that got hit by lightning in Costa Rica was just a tad bit anti-social and had moved far from the group of anchored boats to be "alone". Oops!

So the answers, I guess are: keep sailing, and don't stop until you can find a lot of boats to mingle with.
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Old 06-04-2007, 08:07 AM   #12
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Some more info:

Lightening protection for sailing boats.
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Old 06-04-2007, 09:56 AM   #13
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JeanneP - Sorry, no more like that one on Lightening. As I recall, the author said that you could email him. That might get you something.

When I was in Bimini Bahamas last May a boat had the VHF fried during a storm. No other boats there mentioned anything. The said that a blue glow was on the mast head.

I have seen the lightening protection wiring on buildings melted before. It would seam that a little protection is of some help but I do not think that we could put something big enough to handle a major storm. Really a bit confusing.

Yes, the Mircorwave would be a good place to put something to protect it from lightening if it is unpluged. A metal box is also a good place or wraping it in aluminum foil.
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Old 08-01-2009, 05:43 PM   #14
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Anyone have recent findings/information on this topic?
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Old 08-02-2009, 01:20 PM   #15
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This subject has popped up recently on several different cruising/sail forums. Here is a reply I made concerning boats and lightning. . .

Actually, lightning is very well understood in the scientific community. How it forms and how it reacts is also understood. The University of Illinois and others have many detailed scientific papers available on the subject. Exactly where and when lightning will strike is a variable as it is part of Mother Nature and there is a reason she is called "Mother Nature" and not "Father Nature."

As to lightning and boats, the issue comes in two parts - 1. Prior to the strike; and 2. During the strike.

Part 1. concerns how to reduce the probabilities of lightning striking your boat. Lightning is a two part event. The ionized "leader" sweeps an area below the generating cloud and an opposite "leader" sweeps back and forth up from the surface of the earth. When they connect a pathway is opened and the energy is discharged. To a boat the ground/earth "leader" is of most interest. As this "leader" oscillates around it reaches up "x" distance into the atmosphere. Whenever this leader encounters a vertical object like a tree, house, telephone/power pole, or the mast of a boat it can reach further up into the atmosphere and has a better chance of making a "connection." [same thing as tall men in a bar full of good looking women].

So, reducing the "electrical" apparent height of your boat is good. This can be done with static dissipators such as the Forespar Lightning Master. (Which is a copy of the static wick principle used on airplanes and airliners). The sharp small "spikes" of the device "bleeds" off ions as they build up and electrically reduces your mast height to equal that of the ocean. However, to do this it must have a "significant" and good ground to the ocean. That translates to 4 square feet of flat plate copper in contact with the ocean and 2/0 welding cable between the mast and the plates submerged in the ocean. A static dissipator will not dissipate if it is not connected with the ocean.

So the result of part 1. is to electrically make your boat height equal to the ocean. If you are anchored close to shore or in the close vicinity of other "unprotected" masts/boats your probability of being hit is significantly lower than theirs. If you are out in the middle of no-where/ocean by yourself you are now "even-steven" with the ocean as to getting a hit.

Part 2. is what can you do to prevent/minimize damage to the boat and its contents during a strike. Again, the 4 sq ft. of copper joined with significant sized welding cable to the mast(s) will provide a highly desirable pathway for the lightning's energy to get directly to its only objective - earth ground. If the mast(s) are not sufficiently well-grounded then the lightning energy will try to find an alternate path to the ocean. If the mast is not available to the lightning, then it will travel down the shrouds/stays to the bonding system and set up a "field" inside the boat that will "fry" most electronics and has been known to heat metal thru-hulls sufficiently enough to melt them out of the hull and you are left with 1.5" holes for the ocean to enter. Lack of any grounding to the ocean and you can end up with holes blown through the hull.

Side note: while your boat is floating in the water it is grounded. When you boat is "on the hard" (out of the water) it is not grounded and any lightning strike to your boat or to a neighbors boat will fry your electronics or other fine metal objects or more serious damage. It is advisable if you are going to leave your boat on the hard, in an area with probable lightning, to drive a copper or steel grounding stake into the ground beneath your boat and hook up a significant sized wire from it to your masts or boat grounding system.

There are many other esoteric factors available to folks wanting to get the "whole story" such as positive versus negative forms of lightning, high frequency vs low frequency lightning, etc. but for the boater I think the primary interest is minimizing damage to the boat, contents, and not curling the crew's hair. This is done by dealing with the before and during aspects of protecting/guarding your boat from the energy in lightning.

Exactly where and when a strike will occurs is not determinable - the same as the actual path of a hurricane or tropical storm is not totally predicable as there are too many variables in nature for even the powerful human built computer to input and resolve. So you can only do what your think is cost-effective to "lower the odds" that you will the target.

- - On the subject of why to use welding cable versus flat copper foil - The "flat" copper strips/foil is used for RF grounding. HF/SSB radios use the flat copper rather than round wire as they are concerned with bleeding RF energies to ground. However in Lightning situations, only some of the lightning is "hi-freq" lightning, the rest is "low freq" lightning. The Hi-Freq lightning travels on the "outside" of things. This the type of lightning that can strike a human and he can live through it as the lightning travels down the outside of his skin to earth ground. Of, course he ends up "hairless" and with some surface burns but this form of lightning does not usually kill. Low Freq lightning on the other hand, does kill as the energy travels straight through the body to earth ground, frying, cooking and short-circuiting all the human electrical "circuits" resulting in death. It is also the lightning that splits trees and punches holes in things. Luckily most lightning is statistically of the Hi-freq variety.

But on a boat you need to protect against both which is why you use "welding cable" and not "boat cable." Boat cable is stranded, but only with a low multiple of household stranded wire. Flat copper ribbon which does well for RF does not handle high amperage unless it is in thick "bar" format. Welding cable on the other hand has an order of magnitude more strands and it can also handle large amperage loads. So it is the best compromise and is also flexible which is an absolute necessity in boat wiring. The size of the welding cable must be substantial as any electrical "choke" points can lead to melting and interruption of the pathway to earth ground. Considering the thickness and surface area of your mast(s), you should choose a size of welding cable that effectively matches the electrical surface area. You can find - with much difficulty - the bi-metalic cable clamps that have an aluminum mounting pad for bolting to the mast and a copper/bronze cable clamp to holding the end of the welding cable. The welding cable to in-water copper plates must not have any radical bends or right angle bends between the mast and grounding plates. If you try to make the lightning discharge turn a sharp corner it will simply leave the wire and "flash" over to earth/ocean ground possibly punching a hole in your hull.

The basic principle is engineer a nice, as straight as possible, easy electrical path for the lightning that enters at the top of your mast(s) down through a virtual electrical "tube/pipe" to get to the ocean below with no blockages or constrictions along the way.
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Old 08-03-2009, 02:14 AM   #16
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For years I worried about lightning strikes on the boat, yet there weren't a lot of places where we experienced electrical storms, though when we did, they were terrible. *I've just found a report that is most interesting to me: NASA's plotting the areas of the globe with the highest lightning activity. *There are lots of sites on the Internet reproducing this information, one*HERE

Here's the information in one graphic: *

Florida is one of the most active parts of the U.S. for lightning - hmmph! *No wonder US boats seem to be so paranoid about lightning. *And as all the comments regarding NASA's data point out, it's on or near land that electrical storms happen, it's clear to me that this is one more reason to head offshore and enjoy the blue water passages. *And for Brenda, aka Redbopeep, you'll notice that in general, lightning is not a problem in high latitude sailing. *Go for it!

Here's another tidbit of information I recently learned about lightning and lightning rods: *pointy is not as good as blunt for ATTRACTING lightning. *So now I'm reconsidering the Forespar Lightning Master mentioned by Osirissailing. *Maybe that would work after all. *

Because the link won't work, I'm pasting the article here:

Lightning Rods

Article in New Scientist Magazine, 27 May, 2000, by Jeff Hecht

"KING George III was right and Benjamin Franklin was wrong, at least when it came to the tips of lightning rods. The American scientist and diplomat believed lightning rods, which he invented in 1749, should have pointed tips, and his design has been used for over two centuries. But tests on a New Mexico mountain top show that blunt lightning rods, which George III decreed be used on royal buildings, are actually more effective at attracting lightning.

Electric charge builds up during thunderstorms, and Franklin's original aim was to prevent lightning by dissipating this charge, says Charles Moore, a retired atmospheric physicist formerly at the New Mexico Institute of Mining and Technology in Socorro. Franklin knew from his indoor experiments that earthed, pointed rods could discharge a nearby charged object without a spark. But when he placed a rod outdoors, he found that instead of preventing lightning strikes, it attracted them. Undaunted, he realised that attaching a conductor to the rod could divert the strike harmlessly to earth. This remains the basis of lightning rods today, although a perfect design has never been agreed.

In the 1930s, researchers showed that when a sharply pointed conductor is in an electric field, it is "protected" by a surrounding cloud of ions that reduces the local field strength. Moore wondered if rounded tips would better attract lightning because they lack these ions.

"We ran a competition between sharp and blunt rods," with tips from 0.1 to 50 millimetres in diameter, he told New Scientist. During seven summer thunderstorm seasons, he found that the ones struck most frequently had tips around 19 millimetres in diameter. The rounded rods invariably attracted lightning away from the pointed rods, none of which were hit. Moore calculates that the electric field strength above a 19-millimetre blunt rod is higher than that over an otherwise similar sharper rod, making it better at attracting lightning.

George III had no great insight when he insisted on blunt rods, Moore notes. "He did it out of political pique," because he was angry at Franklin for his support of American independence. "Franklin was right in putting up a conductor," he adds. "We just fine-tuned him."

Source: Geophysical Research Letters (vol 27, p 1487)"
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Old 08-03-2009, 02:55 AM   #17
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If you are considering the Forespar Lightning Master there is one major problem with the device. If you have a VHF antenna or anything else on the top of your mast - you must mount the Lighting Master so the top is at least 6 inches above the highest thing on top of your mast. This is easily accomplished by taking the Lightning mast to a ss welding shop and having them cut it in half and weld in a ss bar of sufficient length to get the "spray" at least 6 inches above the highest thing on top of your mast.

And I must repeat any of these devices are a waste of money if you do not have a sufficient large copper/bronze ground under the boat in the water. Dynaplates do not work as after only a few months, the "equivalent" whatever square feet of the sintered bronze is filled with sea creatures and barnacles reducing the real square feet of conductor to the physical dimensions of the dynaplate.

What all this ends up with is that it is a royal pain in the *** to properly protect your boat. And the occurrences, statistically, of boats getting hit by lightning is extremely low which suggests that the effort is not really cost-effective. There are other hazards more immediate to a cruising boat that spending money on would be more cost-effective. In my case I have been in the marine supply and repair business for almost 20 years and got everything free or at fractions of the cost so I could put all the "extras" on my boat for minimal cost and write them off as advertising/business expenses.
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Old 08-03-2009, 12:29 PM   #18
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What all this ends up with is that it is a royal pain in the *** to properly protect your boat. And the occurrences, statistically, of boats getting hit by lightning is extremely low which suggests that the effort is not really cost-effective. There are other hazards more immediate to a cruising boat that spending money on would be more cost-effective.
I agree with that sentiment. *As I mentioned, considering all the high lightning risk places we've been, only once being hit by lightning implies a low probability of a strike, UNLESS you spend most of your boat life in Florida or along the coasts of some of the other high risk locations. *
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Old 08-07-2009, 12:47 PM   #19
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I would be interested to know how you could construct and attach a bronze copper plate to the bottom of a fibreglass yacht and connect the welding cable. As my mast sits about 4 inches above a lead keel, I cant see how I could install the cable without putting a reasonable bend in it.

The plate seems it would take up an large area underneath, how would you attach it ? would there be enough copper content to prevent it from fouling?

. I thought of installing one of these despersers, but there is a lot more to it than just bolting it at the top of the mast.

My other theory is if you dont provide a path fot the current it wont worry you.

While on a passage in the coral sea I had a bolt of lightening hit the water about a meter from the boat and it melted the inside of a spare bronze sea cock, normally just above the water line, but it probably was under the water at the time of the strike. It made a very loud bang, but took 6 months to discover where the bang came from.

Finally to add something I heard from somewhere is while the boat is at sea and moving around the mast is less likely to be able to make contact, so we are at more risk while 'safely' moored.
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Old 08-19-2009, 11:56 AM   #20
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I would be interested to know how you could construct and attach a bronze copper plate to the bottom of a fibreglass yacht and connect the welding cable. As my mast sits about 4 inches above a lead keel, I cant see how I could install the cable without putting a reasonable bend in it.

The plate seems it would take up an large area underneath, how would you attach it ? would there be enough copper content to prevent it from fouling?
Our mast is not a conductor (it is wood) but of course can still be hit by lightening. Some other owners with wood masts and wood hulls have used a shroud to chainplate to cable to ground at lead keel. We know one fellow who doesn't worry about it while underway but when anchored he attached a 6' x 1" copper grounding rod (like you pound into the ground adjacent your house!) to the boat via a cable that is clamped to a shroud.

Hubby, an engineering PhD and tinkerer to boot, was just the other day saying he'd like to run a cable from chain plate to lead keel but would use a neon filled tube as a "gap" to prevent conduction (and damage to adjacent wood) unless there's a lightening strike. I wonder what he's thinking about but doesn't tell me sometimes...
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