Sparrow50

Lightning Strike Mitigation

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8 hours ago, Sparrow50 said:

Jeff Thayer has the best discussion I've heard about lightning: https://www.59-north.com/onthewindpodcast/290-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.

This is pretty great info!  Very cool.

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So would your takeaways be: 1)  you are more likly to be struck by lightning if you mast is rocking than if it is still; 2) you are more likely to be stuck sailing to weather (higher apparent); and 3) wrap you electronic in aluminum foil so protection if in a nasty storm?

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13 hours ago, Tharsheblows said:

So would your takeaways be: 1)  you are more likly to be struck by lightning if you mast is rocking than if it is still; 2) you are more likely to be stuck sailing to weather (higher apparent); and 3) wrap you electronic in aluminum foil so protection if in a nasty storm?

1) Yes

2) Yes

3) Yes

But also, if I sail into a lightning storm, head downwind, power everything down, wrap electronics in foil, disconnect anything coming into the hull (VHF & GPS antennas, solar panels, and mast wiring, etc.) & wrap the ends in foil. Oh, and ignore the oven solution.

Some open questions I have:

Will closing fiberglass or lexan or wooden hatches make a difference?

What is the effect of deck stepped vs. keel stepped aluminum masts?

What is the effect of carbon masts?

What is the effect of stainless steel vs. non-metallic standing rigging?

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Want to listen to this when I get off work, should be interesting. Sparrow, I think applying certainty to it is a slippery slope. We took a direct hit at the dock in Costa Rica last summer, it was pretty spendy.  I was asked for feedback for a article someone was writing for one of the magazines.  My feedback wasn't used, other than being probably long winded, I was pretty adamant against the black white solution-security net that alot of times come out of the articles around this.  From a engineering prospective it was very interesting, my bank account was not very happy, but I think I learned enough to not even try putting a solution in a box.  It's a whole lot of maybes and mitigation.

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3 hours ago, SASSAFRASS said:

Want to listen to this when I get off work, should be interesting. Sparrow, I think applying certainty to it is a slippery slope. We took a direct hit at the dock in Costa Rica last summer, it was pretty spendy.  I was asked for feedback for a article someone was writing for one of the magazines.  My feedback wasn't used, other than being probably long winded, I was pretty adamant against the black white solution-security net that alot of times come out of the articles around this.  From a engineering prospective it was very interesting, my bank account was not very happy, but I think I learned enough to not even try putting a solution in a box.  It's a whole lot of maybes and mitigation.

Looking forward to your experienced commentary on the podcast. Would love your reaction to it.

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Don't put your portable electronics in an oven with a glass door. Makes a very poor Faraday cage!

Want to see if your Faraday cage works? Put a mobile phone in it, close the door then dial the phone.

I used a big aluminum tool box with a special EMP mesh tape gasket. Somewhere on our blog are details.

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Ended up working late again, will listen tonight.  One note on the Faraday part, you can probably save components but what I saw was virtually every shielded cable was toast.  Two entire n2k networks radar SSB com etc.  Antenna coax, one of which took the hit seemed fine?? Cat5 actually was blow out in places.  Certainly is a argument for a wireless backbone on integrating electronics.

Cat was fine though, he does some random yowling at night though.

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Didn't get through all of it but listened to most of it.  Definitely agree on the emp pulse more or less toasting everything.  Ironically, our experience would be a case study showing the exact opposite of what was described in the ion discharge protection bubble.  We were one of two sailboats in a fairly large marina. We have wood sticks but the rigging is all common from the boomkin stay Tang in the water all the way up and over both masts to the bobstay Tang also in the water.  The cap shrouds are also 1x 19 with the chain plates near the water.  The boat is not bonded.  When we got hit it was overcast but not raining, lots of clouds ready to start their afternoon lightning show but nothing going on at that point.  Based on the process described I would think whatever protection effect that could have happened would have been ideal conditions as the boat wasn't moving.  For me I think I will stick to the lighting protection plan of not being somewhere with lightning as the only cure. Otherwise it's run away or cower.

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I always heard one should sail near to a boat with a taller mast.  Electronics?  We didn’t have no stinking electronics.  Lead line, compass, paper charts.  Way back in the last century.

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My boat (not the one I have today) was struck by lightning forty years ago at the south entrance to the Cape Cod Canal. What are the chances I’ll be struck again? Or at least that’s what I tell myself in lightning storms 500 hundred miles off the coast when I’m the only object poking it’s head above the sea within Radar range.....

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38 minutes ago, Orion Jim said:

What are the chances I’ll be struck again? 

 

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We were hit many years ago about 200 miles from Bermuda. The remarkable thing is how long it took for us to get hit, probably 20 minutes with lightning hitting the water around us constantly. Quite remarkable being in the middle of the whole thing although I would happily given up on a second opportunity.

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that whole 'taller mast' thing is bunk. Ive watched strikes in a mooring field and the boats hit were by no means the tallest. 

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I was in a pretty intense lightning storm off of Nicaragua (Chubasco storm). Lasted over an hour. Looked like a press conference with the lightning all around non stop for the entire time. Brighter than day. Wind about 60 knots. Thank God no one got struck; the only electronics that were inconvenienced was my iPad running navionics (I know, subject verb agreement...).

None of the other electronics on the boat that were on (all) seemed to be inconvenienced. But, both of us were on deck dealing with a bunch of shit.

When it was all over, the iPad was fine.

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On 5/5/2020 at 2:40 AM, Sparrow50 said:

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

 

 

I have direct experience here: We were hit in steel boat at anchor, It was an intense electrical storm  with several strikes hitting the water close by. Only afterwards we were told by others that one discharge struck us directly.

There was some visible discoloration of one of the stay terminations atop the mast. The only electrical fitting up there was the tricolor and it was OK. We had no damage to any electronics. The backstay was the HF antennae but both the ATU and the SSB radio were fine.

I think metal boats and ships are generally pretty much immune.

 

 

 

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13 minutes ago, MikeJohns said:

I think metal boats and ships are generally pretty much immune.

Sure sounds like it.

That would be lottery ticket time.

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My theory is that all that ‘mitigation,’ which is grounding, makes the boat more attractive to lightning although I do grant that the mitigation does direct the current. It’s a Catch-22, really.

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On 5/7/2020 at 10:55 PM, Zonker said:

Don't put your portable electronics in an oven with a glass door. Makes a very poor Faraday cage!

Want to see if your Faraday cage works? Put a mobile phone in it, close the door then dial the phone.

I used a big aluminum tool box with a special EMP mesh tape gasket. Somewhere on our blog are details.

Even if it's a good indicator, I am not convinced that dialling the phone is 100% sure. At high frequencies, weird stuff happens and you could imagine higher frequency electric/magnetic waves making their way into a leaky Faraday cage even if it blocks mobile phone frequencies.

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I agree. I'd use it more as a "negative test" - if it rings you are pretty sure your oven sucks!

 

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There are certainly some things that sound like good ideas or practices.  The certainty and anecdote reference with strikes drives me nuts, like steel boats being immune, or "X" happened and we were fine.

If you draw the short straw my guess is your fucked. In the right or "wrong" conditions it will win or do-wreak whatever havoc it wants.

 

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The commercial fleets of smaller coastal craft are a good indication. There was a lot of effort to make wooden boats safer when a strike would often jump or track from deck gear or mast base to the engine block vaporizing wiring on the way.  The results were not pretty.

 

The recommendation for proper protection is a straight low resistance conductor. For example the US Navy on non metal boats requires a copper AWG 0000 cable, installed in a straight line from a high point or metal mast base to a substantial immersed grounding plate . But metal boats don’t need anything other than a spike atop the mast providing the mast is metal and in contact with a metal deck. There are also protective MOV's across the power cables ( metal oxide varistors ) these are very cheap, effective and seldom installed for protection in leisure craft . 

 

The majority of metal vessels, boh ships and smaller craft are often unaware that they havee even been struck by lightening, and it very rarely if ever causes any issues providing antennae are kept within a cone of protection ( provided by a higher grounded conductor).

 

Protecting sailing craft is no different, a straight low resistance path to ground is the recommended practice, relying on rigging shackle contact is not sufficient. There should be a good high current low resistance contact to a stay and it should lead on to a grounding plate.

 

Rigging shackles have a low contact area and can have high resistance to lightening and aren’t considered an ideal conduction path. A sizable high current connection should be provided across rigging terminations if you rely on an immersed chain-plate. The area of the chain-plate may also be inadequate.

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On 5/8/2020 at 4:55 AM, Zonker said:

Don't put your portable electronics in an oven with a glass door. Makes a very poor Faraday cage!

Want to see if your Faraday cage works? Put a mobile phone in it, close the door then dial the phone.

I used a big aluminum tool box with a special EMP mesh tape gasket. Somewhere on our blog are details.

Whilst reading this makes both seemingly obvious sense and easily tested logic, how does that apply to your average Car, which are well known to be the second best protection from Lightening (the first being - not being there......) yet are full of glass windows and windshields?

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Good thought but people are not electronics nor are they subject to the effects of EMP.

I think in a lightning strike on a boat people are not typically harmed due to a direct contact with a bolt because the lightning hits the mast/dissipates in a small way through the shrouds and mast and finds its way to the water. In the process you get huge EMP pulses that fry the electronics.

In a lightning strike on a car, with people inside, the lightning finds its way to ground through the metal structure of the car. As long as you're not touching it, you won't get electrocuted. But nothing is protecting the electronics because the car is NOT anything like a Faraday cage - it is full of glass holes. 


Here's a story from the Detroit News:

. In September 2014, a year-old Toyota Venza five-door wagon was parked at a suburban Detroit bowling alley during a thunderstorm, and it wouldn’t start when the owner returned. The car looked just about perfect, no damage, no leaks. When the owner tried to turn the key, nothing happened. The car was towed to Page Toyota in Southfield, where technicians figured it would be an easy fix such as a blown fuse.

But the car was a total loss. After three days of work, the technicians found that all of the car’s 28 computers had likely been fried by lightning. The insurance adjuster wouldn’t risk spending the money required to find out if more damage had been done, such as to wiring.

Dave Davis, a 12-year veteran technician at Page, said, “We probably spent $3,000 to $5,000” replacing the engine computer, the vehicle power-management computer and the “smart key” computer. Each cost about $600, not including labor, and still the car’s engine would only run at idle speed, and nothing else electrical worked.

“The car took a direct hit; it must have had an enormity of electricity. On this one, everything was fried,” said Davis.

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23 hours ago, Boink said:

Whilst reading this makes both seemingly obvious sense and easily tested logic, how does that apply to your average Car, which are well known to be the second best protection from Lightening (the first being - not being there......) yet are full of glass windows and windshields?

In high lightening areas, vehicle electronics failure from lightening strike is not considered a problem; it’s extraordinary nowadays if it causes any damage.

Same for aircraft. Metal aircraft are innately protected. Composite aircraft embed an external conductive mesh for lightening protection.

On aircraft, even a strike that fuses alloy aircraft skins doesn’t damage the electronics providing a few simple design rules are followed. There are various design standards  from several sources, automotive electronics adhere to a similar standards.

 

As for windscreen openings in metal bodies : Polarization of the low frequency EM wave is critical for it to enter, it doesn't get into holes very well, and if it strikes the roof of the aircraft or car, the EM field won’t enter even through the larger front windows, at least not at significant levels. The significant EM emission radiates outwards. Secondary EM from conduction of the charge are not significant providing cables are run together and microprocessors are screened . The same Spurious EM Emissions standards have actually made most electronics almost completely immune from nearby direct and indirect lightening related EMP.

 

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I have a pretty good understanding of EMP screening on aircraft (black boxes on airliners are in metal cages with optical interfaces where possible).

But I am surprised that cars protect their electronics in anything like a similar fashion. Which standards apply to car electronics spurious emissions; I only know of the FCC B ones for consumer electronics etc.?

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I think most of the world applies ISO these days for EM emissions.  Military contracts come with some detailed specific standards all country specific but all similar, some better than others. The UK is quite detailed even down to wiring layout. The US provides separate installers guides for compliance. EMP is a big issue for them. A few years ago the US military introduced specific lightening protection (mainly electrostatics if the rest is allready EMP resistant). But lightening diverters from antennae and other sensors has become mandatory too.

All vehicle manufacturers are now aware of the bonding earthing shielding and filtering requirements for EMC standards. When a design or layout prevents EM getting out of an enclosure or wiring loom for example it also stops it getting in. 

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Thank you for posting the link, its a good listen. I have been offshore and facing a wall of lightning and wondered how we could pass unscathed.  Many years ago I worked on lightning and surge mitigation for industrial systems and have some comments I hope help

Pipe Cleaner atop mast: I do not think they help.  The truck has many corners, fittings, items such as windex and antenna, these basically provide the same protection, bleeding off the charge.

Steel vs Plastic boat:  Yes steel is good but in the conditions you are likely to face lightning, plastic is fine. Both have risks inside the boat, for that though steel is better, but not perfect.   Lightning is a high frequency signal and travels on the exterior of a conductor.  A copper pipe with surface area is better than solid wire. This is the skin effect.  For a steel boat, the energy travels on the exterior or around the boat to the water.  A plastic boat is likely coated with water, even better, salty water.  The energy will flow on the surface of this water conductor providing similar protection as a steel boat.  

Bonding vs grounding.  In this discussion the term grounded was used for the boat.  Unless your bottom is touching land, it is not grounded. The lightning wants to get to the earth and will travel through the water to get there.  Salt water is more conductive than fresh and because of this the potential difference can be higher for fresh water, causing more damage from lightning events. This is important as your boat is not dissipating the energy, its just part of the circuit.  A low impedance (resistance) path lets the energy go right through causing little or no damage.  

With the skin effect the energy goes around the boat, however dangerous voltages can occur inside the boat without bonding of the metallic items.

On land, most people are not directly struck by lightning. The lightning hits near them, raising the voltage at that point to say a million volts.  Somewhere off in the distance is zero volts.  Like topographical map the lines of voltage differences branch out.  Since humans are ugly bags of water, we conduct better than the ground and it travels up one leg down the other.   

The metallic parts on the exterior of the boat will become energized.  The major parts that pass through the hull are bonded together, mast shrouds, keel, etc. to keep the voltage DIFFERENCE low.  Without this there would be flash over between metal pieces.  Common sense, keep crew away from the mast and shrouds, both above and down below. The bonding keeps the voltage differences low and provides a low impedance path for the energy to flow out of the boat.

Protecting electronics.  The best everyday example of a faraday cage is your microwave oven.  It keeps the microwaves inside, yet the holes in the shield let light in so we can see what is inside.  Unless the boat is a perfect cage a large electrical impulse will come inside the boat.  Likely more for a plastic boat.  Every wire is an antenna and if enough voltage is induced upon it, the difference between conductors fry the devices. Due to the orientation of the wires, ruggedness of the electronics, size of pulse, its almost impossible to have a protection plan for the average sailor.  In my opinion the only solution is a back up plan, tin foil wrapped GPS, a compass, paper charts....

 

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On 5/22/2020 at 8:36 PM, Special Ed said:

Thank you for posting the link, its a good listen. I have been offshore and facing a wall of lightning and wondered how we could pass unscathed.  Many years ago I worked on lightning and surge mitigation for industrial systems and have some comments I hope help

Pipe Cleaner atop mast: I do not think they help.  The truck has many corners, fittings, items such as windex and antenna, these basically provide the same protection, bleeding off the charge.

Steel vs Plastic boat:  Yes steel is good but in the conditions you are likely to face lightning, plastic is fine. Both have risks inside the boat, for that though steel is better, but not perfect.   Lightning is a high frequency signal and travels on the exterior of a conductor.  A copper pipe with surface area is better than solid wire. This is the skin effect.  For a steel boat, the energy travels on the exterior or around the boat to the water.  A plastic boat is likely coated with water, even better, salty water.  The energy will flow on the surface of this water conductor providing similar protection as a steel boat.  

Bonding vs grounding.  In this discussion the term grounded was used for the boat.  Unless your bottom is touching land, it is not grounded. The lightning wants to get to the earth and will travel through the water to get there.  Salt water is more conductive than fresh and because of this the potential difference can be higher for fresh water, causing more damage from lightning events. This is important as your boat is not dissipating the energy, its just part of the circuit.  A low impedance (resistance) path lets the energy go right through causing little or no damage.  

With the skin effect the energy goes around the boat, however dangerous voltages can occur inside the boat without bonding of the metallic items.

On land, most people are not directly struck by lightning. The lightning hits near them, raising the voltage at that point to say a million volts.  Somewhere off in the distance is zero volts.  Like topographical map the lines of voltage differences branch out.  Since humans are ugly bags of water, we conduct better than the ground and it travels up one leg down the other.   

The metallic parts on the exterior of the boat will become energized.  The major parts that pass through the hull are bonded together, mast shrouds, keel, etc. to keep the voltage DIFFERENCE low.  Without this there would be flash over between metal pieces.  Common sense, keep crew away from the mast and shrouds, both above and down below. The bonding keeps the voltage differences low and provides a low impedance path for the energy to flow out of the boat.

Protecting electronics.  The best everyday example of a faraday cage is your microwave oven.  It keeps the microwaves inside, yet the holes in the shield let light in so we can see what is inside.  Unless the boat is a perfect cage a large electrical impulse will come inside the boat.  Likely more for a plastic boat.  Every wire is an antenna and if enough voltage is induced upon it, the difference between conductors fry the devices. Due to the orientation of the wires, ruggedness of the electronics, size of pulse, its almost impossible to have a protection plan for the average sailor.  In my opinion the only solution is a back up plan, tin foil wrapped GPS, a compass, paper charts....

 

Good post, thank you. What is your take on blow out seacocks, or how to avoid it?

Last year, my cousins and I were out racing on my boat when we encountered a thunder storm with lots of rain and lightening. Sitting in the cockpit under the mast and boom and being absolutely soaked, would you say that we were in increased danger if the boat/mast were hit by lightening?

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On 5/16/2020 at 6:46 PM, MikeJohns said:

For example the US Navy on non metal boats requires a copper AWG 0000 cable

Interesting - ABYC only requires #4 and for years it was #8 (commercial pressures from builders who don't want to fit an expensive cable!)
 

On our catamaran, with a mast stepped on the bridgedeck, there was no easy way to ground it. So I installed a glass tube right in front of the mast and could drop a #1 cable attached to a copper pipe straight into the water. About a straight a path as you could hope for.

I ignored the carbon inboard chainplates. If they blew the mast wasn't coming down.

2 hours ago, Misbehavin' said:

Last year, my cousins and I were out racing on my boat when we encountered a thunder storm with lots of rain and lightening. Sitting in the cockpit under the mast and boom and being absolutely soaked, would you say that we were in increased danger if the boat/mast were hit by lightening?

Well yes.  On a small boat the bolt is trying to get to ground. If you are in the way, then you get zapped. Staying away from the mast as much as possible is wise. Boom is not as big a problem because the strike will travel down the mast and yes, some with jump to the boom but likely not as much.

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@Special EdWould it make sense on a GRP / wooden boat to have a copper plate that goes on the deck surface from the mast to the deck/hull joint than along the hull to the water ? Would it keep the strong currents outside the boat (like for a steel hull in a way) ?

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On 5/25/2020 at 6:34 AM, Panoramix said:

@Special EdWould it make sense on a GRP / wooden boat to have a copper plate that goes on the deck surface from the mast to the deck/hull joint than along the hull to the water ? Would it keep the strong currents outside the boat (like for a steel hull in a way) ?

I think the general guideline is to provide as straight a path as you can to earth so that the lightning doesn't choose to go its own way, so probably not. It won't provide a faraday cage unless you wrap most of the boat. The most thorough description I have seen around boats and lightning and how to mitigate damage is at: http://marinelightning.com/science.htm . It sounds reasonable to me, but still don't know if it is right. He is/was selling a solution.

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3 hours ago, Mark Morwood said:

I think the general guideline is to provide as straight a path as you can to earth so that the lightning doesn't choose to go its own way, so probably not. It won't provide a faraday cage unless you wrap most of the boat. The most thorough description I have seen around boats and lightning and how to mitigate damage is at: http://marinelightning.com/science.htm . It sounds reasonable to me, but still don't know if it is right. He is/was selling a solution.

Thanks, that's an interesting read. He doesn't seem to think that you need a path as straight as possible, he is advocating discharging the current at the sea surface. I wouldn't have thought about this, may be that's why the chain trick works.

image014.jpg

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On 5/23/2020 at 4:36 AM, Special Ed said:

....................... A plastic boat is likely coated with water, even better, salty water.  The energy will flow on the surface of this water conductor providing similar protection as a steel boat.   ..................

Sea water is a relatively poor conductor and rain water is an effective insulator.

Conductivity ( S/m) of seawater is around five,  Conductivity of boat building steel is around 6.3 million,  there's no way a thin film of seawater could provide any similar protection !

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Sorry for any confusion as I was trying to reduce complexity and ultimately it looks wrong.  Its really not about conductivity but more about the high voltage, current, and frequency of a lightning event.  For example, air is a very good insulator, until it isn't.  Old horror movies had a device called a Jacobs Ladder, two wires shaped like a V.  A small spark jumps the air gap at the bottom of the V, ionizing the air.  The spark grows in length up the V, with the same energy applied.  

In the conditions of a wet boat, there is large surface area almost an infinite number of parallel circuits, providing a low impedance path for the lighting to flow around.  The impedance (resistance) approaches the same level as the steel boat.  The current is not flowing through the steel or water, but on it, the skin effect.  Water is much better than plastic and because of the area covered provides a path for the energy to flow.

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Panomamix:

I do not know enough about wooden boats to make a comment.  I know wooden utility poles have a ground wire down the side and into a ground rod.  Seems to work pretty well, but that is on land. 

My experience was on protecting industrial device, pumps and motors, control panels.  Most of the time we provided an alternative path for the energy to flow, but sometime we added resistance.  An example is on most computer power supplies have a choke on it, the toroid magnet on the power cord.  We utilized those and even added length wire with bends in it to increase the resistance to electrical surges.      

Sometimes you can make things worse by making the path too good.  If a sites grounding was too good, its like all your neighbors shit flowing into your basement because you have a great drain.  

I am stuck with an aluminum mast, but the pod cast covered how it provides protection rather being a lighting rod.  In this case would a diffuser, pipe cleaner be good for a wooden mast??   

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4 hours ago, Special Ed said:

...........In the conditions of a wet boat, there is large surface area almost an infinite number of parallel circuits, providing a low impedance path for the lighting to flow around.  The impedance (resistance) approaches the same level as the steel boat.  The current is not flowing through the steel or water, but on it, the skin effect.  Water is much better than plastic and because of the area covered provides a path for the energy to flow.

A quick calculation shows that even the ideal of a film of pure seawater 1mm deep over a surface has a resistance of a magnitude of hundreds of ohms per meter of path. That's not low impedance.  In consequence it will vaporize instantly. 

I think you are confusing skin effect with charge distribution. Skin effect is not "on the surface" as you say but within the conductor growing in conduction depth in an order of magnitude of one mm per microsecond. A lightening current pulses main discharge conduction transient  (say 100 thousand amps) lasts around 30 to 40 microseconds. That's all in one direction and is entirely a Direct Current transient (It's a capacitive discharge). Then the magnetic field collapses around the plasma channel  and a lower reverse current flows for a similar time, this then in turn reverses oscillating like a classic LC circuit but rapidly damped. Then the charge redistributes in the cloud and the entire event happens again sometimes 2 or 3 times.  So there's lots of HF but the main discharges are transient DC.

 

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Any clever electrical types care to comment on likelihood of 90% of the charge going down a relatively high cross sectional/high surface area/low resistance aluminum mast versus a bunch of thin s.s. shrouds?

When you're dealing with 1000's of Amps, does it matter because 10% of a brazillion is still a lot?

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7 minutes ago, Zonker said:

Any clever electrical types care to comment on likelihood of 90% of the charge going down a relatively high cross sectional/high surface area/low resistance aluminum mast versus a bunch of thin s.s. shrouds?

When you're dealing with 1000's of Amps, does it matter because 10% of a brazillion is still a lot?

I figure after traveling down thru 10,000 or 50,000 feet of poorly conducting air the lightning strike is relatively indifferent about the last 50 feet of sailboat hardware.

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1 hour ago, El Boracho said:

I figure after traveling down thru 10,000 or 50,000 feet of poorly conducting air the lightning strike is relatively indifferent about the last 50 feet of sailboat hardware.

It's not air anymore, it's a plasma and is a very good conductor indeed. 

 

1 hour ago, Zonker said:

Any clever electrical types care to comment on likelihood of 90% of the charge going down a relatively high cross sectional/high surface area/low resistance aluminum mast versus a bunch of thin s.s. shrouds?

When you're dealing with 1000's of Amps, does it matter because 10% of a brazillion is still a lot?

If you did as you said it will all go via the mast. The rest will rise in potential for a few microseconds each pulse given the mast resistance but it won't develop enough voltage to break down any other conduction path.

Oddly enough WRT conductor sizes, sometimes a small cable can simply act as a leader and once it vaporizes the plasma channel takes over.  No good for subsequent strikes but.

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2 minutes ago, MikeJohns said:

It's not air anymore, it's a plasma and is a very good conductor indeed.

Yes, correct, but it was 30,000 feet of air a moment before. Just like boat parts were in good working non-melted condition a moment before. Look down from an airplane at cruise as if you are an incipient bolt of lightning. Would a tiny sailboat look like a shortcut?

The plasma channel forms from fingers of charged air reaching towards each other. Which ones connect might as well be chance. That is why in one particularly fierce cocktail hour storm a strike chose (and ignited) the nearby wooden dock piling rather that the adjacent aluminum sailboat masts 50 feet higher and presumably grounded as cruisers do.

That knowledge (belief?) inspires me to do the recommended basic grounding but otherwise take it as it comes. I try not to look. Seems to help. So far so good.

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2 hours ago, El Boracho said:

................. relatively indifferent about the last 50 feet of sailboat hardware.

 

1 hour ago, El Boracho said:

...........The plasma channel forms from fingers of charged air reaching towards each other. Which ones connect might as well be chance. .........

The crux is that it's made attractive !

The ground leader forms from a good discharge point and the downward path meets one of the upward. That's why a grounded spike or sometimes metal sphere is used at the top,  it initiates a leader from the ground upward and  that a strike will go direct to the spike, not to any other part of the boat.

So yes the downward path is pretty random, but within a 45 degree cone that leader will go to a lightening rod.

The attached pic shows a ground leader going up from a boat mast, the non contact downward leaders and the final contact that creates the plasma channel.

lightning yacht.jpg

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Living out on the empty prairies of eastern Wyoming, without a tree for ten miles and with a 45' high wind turbine and pole-mounted solar PV.... We gave quite a bit of thought to lightning protection. As far as our research got us, the basic defense-in-depth approach seemed to be:

  1. Multiple robust, easy paths to ground.
  2. Lots of contact area with the earth.
  3. Catch and direct the lightning before it passes thru anything important/expensive (high point concentrator).
  4. Lightning pots (silicon dioxide varistors).
  5. Individual circuit surge clamps ahead of every MOSFET.
  6. ???
  7. Hope.
  8. Have DigiKey on speed dial.

For all that, we've still had chunks of FRP nacelle blown off our wind turbine, plus melted stators, rectifiers, slip rings, and down wires. We've had grounding cables melted off the solar trackers and the shop's metal roof. We've lost the original solar PV controller, the Battery monitor, several turbine charge-controller capacitors, and one MOSFET to lightning.  Only the house has escaped relatively unscathed: it is all steel, bolted to slab on grade. Steel roof, purlins, skeleton, studs, siding, and doors (but plastic plumbing!). It has literally hundreds of paths to ground, a corner-to-corner resistance of 0.1 ohms, and a dry framing-to-ground resistance of about half an ohm. 

But still. Lightning makes its own rules, ultimately; 300 million volts go where they want to go. We view lightning protection much like we view 'bear proof' food storage containers in grizzly country. Bear resistant, bear resistant.

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17 hours ago, Diarmuid said:

Living out on the empty prairies of eastern Wyoming, ...............We view lightning protection much like we view 'bear proof' food storage containers in grizzly country. Bear resistant, bear resistant.

The level of protection depends on the cost benefit trade-off. It’s expensive to fully protect any terrestrial installation (especially in your situation), and generally requires some expert level design, but 100% protection it is achieved routinely.

On boats and ships it's no where near as complex. Sailboats offer a near perfect position for an air terminal and  the entire craft lies within the zone of protection.

 

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Hang on, are we supposed to hang bears in the water hanging from the shrouds? I think I missed a step.

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Ben Franklin over the side with jumper cables on his nutsack. Mix your martinis dry and never piss off the transom in a thunderstorm. If you live in Florida, get teh fuck out of Florida. You know what -- forget lightning, that's just good advice on every level. Lake Titicaca is also bad for thunderstorms, plus it has a silly name like some scat video that popped up when you were trying to do serious internet research.

 

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Having our boat struck by lightening I hope this can help somebody else.

The short version... IMHO the best and only defense is good insurance.  Mitigation is an art not a science and your results may vary!

The longer version...  we have a 36 foot trimaran trimaran that was struck while in its slip about a year ago.  As best anyone can tell the main strike hit about 200 yards away and literally vaporize an entire (decent sized) tree and set a guest house on fire.  Our boat has been hit at the same time with the strike happening at the masthead (fried the CHF antenna and lightening dissipator).  The boat is not bonded/protected nor was it the highest mast.  Four other boats were hit at the same time all in the general proximity of us and all took varying forms of damage.  All of those boats were bonded/protected save for one.  Two were monohull sailboats (one not bonded) and two were powerboats.  On our boat systems that survived and systems that didn't was entirely haphazard.  A handheld battery powered GPS not turned on or plugged into anything, and wrapped in foil in a drawer no longer functioned.  On the other hand the solar panels, and batteries survived... while the in-line controllers did not.  The one sailboat that was hit (monohull) and was not bonded said he wasn't bonded because in a prior strike (different sailboat) when his prior boat was bonded the strike blew the ground plate our of the hull and the boat sank at the slip.  Our damage was pretty extensive (six figure claim) but not at all life threatening in that even with the hull damage (about 20 or so small pin prick size holes scattered all over the three hulls) we barely took on any water and it was easy to seal the areas as we found them. I dove the boat and sealed the holes from both inside and out.  We actually didn't get hauled out for 4 days (it was July 4th weekend and the marina staff off) and I didn't need the bilge pumps there was so little inflow.  

One of our good friends works in the marine insurance biz and says the only thing the data seems to say for sure is that multihulls get hit with greater frequency than monohulls.  I thought that might be grounding or bonding since fewer multihulls would be and was looking at ways of bonding our boat.  He claimed the data didn't support that conclusion.  He also pointed out - and multiple others confirmed same - that if in fresh or brackish water the size of the grounding plate needed / recommended was such that it was not practical. 

Anyway I don't know what to make of it all but the insurance guy's comment was (close as I can recall) as follows... We do this for a living.  If the data suggested there was some way to protect boats we would be pushing builders and policy holders to have such a system.  But the data suggests there is no effective way to mitigate or avoid lightening strikes on your typical recreational sailboat.

I guess I believe him.  As a scientist I would have said it would not be possible for that handheld GPS to be fried.  But yet it was.  Kinda funny actually.  My wife always made fun of me for that thing sitting in the drawer wrapped in foil and would ask if I had a tin foil hat as well.  After the strike I thought I would show her... "now you will see why I did this Dear... watch as the GPS will work fine when all are other nav systems are wrecked..."  And I waited for it to power up.  And I waited some more as I got new batteries convinced it had to be that.  Nope. It was toast when it had worked fine a few weeks earlier.  And you know she loves to bring that up LOL. 

 

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56 minutes ago, Wess said:

I guess I believe him.  As a scientist I would have said it would not be possible for that handheld GPS to be fried.  But yet it was.  Kinda funny actually.  My wife always made fun of me for that thing sitting in the drawer wrapped in foil and would ask if I had a tin foil hat as well.  After the strike I thought I would show her... "now you will see why I did this Dear... watch as the GPS will work fine when all are other nav systems are wrecked..."  And I waited for it to power up.  And I waited some more as I got new batteries convinced it had to be that.  Nope. It was toast when it had worked fine a few weeks earlier.  And you know she loves to bring that up LOL. 

 

Mrs P would love that as well! :rolleyes:

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2 minutes ago, Panoramix said:

Mrs P would love that as well! :rolleyes:

LOL, yea but I don't complain. I lucked out in the wife department.  Mine gets mad when I SELL boats.  We had eleven at one stage. 

On the positive side of the lightening strike nothing in the boat's bar got wrecked.  And we tested that ALOT!  Much drinking ensued after the strike.

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12 hours ago, Wess said:

...............  we have a 36 foot trimaran trimaran ..........

Multi ( and multi multi ;-)  hulls are notorious for attracting lightning. Cats are an order of magnitude higher apparently.

A friend was quite happy when he had ALL his outdated electronics replaced under insurance when his boat was struck. A quick upgrade that added a lot of value to his boat when he sold it later.

Your friend is right. Small non conductive hulled boats below around 35 feet are extremely hard or next to impossible to fully protect. So are non conductive hulled boats in fresh water.  Although the larger the boat gets the better the protection gets. But although smaller boats might lose their electronics, you can still stop the boat sinking by using relatively simple installations of down conductor and ground plate.

More recent concerns both by regulatory bodies and insurance companies is new battery technologies and lightning both initial and secondary effects  which haven't even been considered by the battery manufacturers.

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On 5/29/2020 at 10:30 AM, MikeJohns said:

Multi ( and multi multi ;-)  hulls are notorious for attracting lightning. Cats are an order of magnitude higher apparently.

The only data I've seen was from a BoatUS study in Florida and it showed that catamarans were twice (not 10x) as likely as mono-hulls to get struck. Maybe not very surprising if you consider most are in marinas, and they each take up twice as much room as a mono-hull, hence half as many in any given area, and therefore twice the chance any particular one will be hit if you subscribe to the theory that the lightning is going to hit whatever happens to be in its path somewhat regardless of what it is.

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Claims make poor statistics except for insurers. From shielded water area theory you’d certainly expect a ratio around 2:1. Globally there are areas where there are virtually no multihulls and other areas where they predominate. Same with Lightning, in some areas it’s almost unknown in others it's almost a daily event.

 Referring to the claims for SE Asia for one insurance company from the Singapore office, over half the claims for lightning strike were for sailing catamarans but they represented one fifth of the insured fleet of sailing craft. It’s possible, thinking about it, that that’s explained by geographic anchorages.

 Overall numbers are still relatively low, from memory over a 3 year period around 12 sailboats with significant claims. Probability for a claim was still low, around a fifth of a percent.

Also the insured craft that may have been struck but had no damage aren't counted. Anyway the claims are minuscule in comparison to claims for collision and grounding so it’s never going to be  considered a risk requiring mitigation by insurance

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On 6/2/2020 at 8:10 PM, MikeJohns said:

Claims make poor statistics except for insurers. From shielded water area theory you’d certainly expect a ratio around 2:1. Globally there are areas where there are virtually no multihulls and other areas where they predominate. Same with Lightning, in some areas it’s almost unknown in others it's almost a daily event.

 Referring to the claims for SE Asia for one insurance company from the Singapore office, over half the claims for lightning strike were for sailing catamarans but they represented one fifth of the insured fleet of sailing craft. It’s possible, thinking about it, that that’s explained by geographic anchorages.

 Overall numbers are still relatively low, from memory over a 3 year period around 12 sailboats with significant claims. Probability for a claim was still low, around a fifth of a percent.

Also the insured craft that may have been struck but had no damage aren't counted. Anyway the claims are minuscule in comparison to claims for collision and grounding so it’s never going to be  considered a risk requiring mitigation by insurance

Mike - all I can say is my insurance company sure told a different story both in terms of prevalence and costs.  They tended to be high $ claims relative to other types.  I have no way to know what is true and not but the 12 sailboats over 3 years doesn't seem (??) to pass the sniff test.  In my instance alone, while my boat took the worst of the hit, three or four other boats (not recalling off the top) also had damage in the same strike.  They may have actually been higher damages than my 6 figure claim given the value of their boats and the systems on them.  I sure hope your numbers are right though because I don't want to go through that again!

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10 hours ago, Wess said:

Mike - all I can say is my insurance company sure told a different story both in terms of prevalence and costs.  They tended to be high $ claims relative to other types.  I have no way to know what is true and not but the 12 sailboats over 3 years doesn't seem (??) to pass the sniff test.  In my instance alone, while my boat took the worst of the hit, three or four other boats (not recalling off the top) also had damage in the same strike.  They may have actually been higher damages than my 6 figure claim given the value of their boats and the systems on them.  I sure hope your numbers are right though because I don't want to go through that again!

No, not the total by any means. Keep worrying !   It’s only an indication of the ratio of what they term 'significant cost' claims,  and only on claims to one companies office in Singapore.

Did you have any protection fitted ?  Zonker's method above would certainly help.

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1 hour ago, MikeJohns said:

No, not the total by any means. Keep worrying !   It’s only an indication of the ratio of what they term 'significant cost' claims,  and only on claims to one companies office in Singapore.

Did you have any protection fitted ?  Zonker's method above would certainly help.

Mike - see post 47 for answers to your Qs.

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