Lightning, and what to do about it

[Frankly]

Originally Posted by waterman46

Safer under power lines? Sounds questionable.

If a lightning strike popped one of those wires off its insulator, I would not want to be there!

"Lightning impulse voltages generally have the highest values and the highest rates of voltage rise.
The time range for these voltages to crest is about 0.5 to 6 microseconds. Although it is impractical
to provide a sufficiently high impulse insulation Ievel to withstand the voltage developed when a
conductor is struck by an average strength lightning stroke, lightning flashovers may be controlled.
This is done by locating overhead ground wires to intercept direct strokes and divert the lightning
current to earth through the steel towers or through the ground wires provided on wood pole
structures for this purpose. This diversion of the current is accomplished by coordinating the insulator
string and air gap insulation values, and by obtaining a sufficiently low footing resistance.
In a region of average storm intensity of 30 storm days per year, a transmission line will be struck
on the average of 100 direct strokes per 161 km (100 mi) of line per year. Overhead ground wires
must be used on transmission lines to take these direct lightning strokes and shield the conductors.
The lightning current is expected to follow a path along the shield wire, down the tower, and through
the tower footing resistance to the ground. The entire top of the tower and the connected overhead
ground wire will attain a high voltage, mainly because of the current resistance in the tower footing.
An evaluation of tower clearances and conductor and overhead ground wire configurations for an
acceptable lightning protection design is based primarily on theory and experience."


Taken from the Design Manual for Transmission Lines.


Frankly

[belizesailor]

Originally Posted by Cpt Pat

Woe is me. All is lost. It's up to fate. Don't look both ways before crossing the street because: "when it's my time to go, it's my time."

Fatalistic rubbish. You'd think no one here has heard of Benjamin Franklin.

I worked as a broadcast engineer, and we'd take direct hits on our towers hundreds of times a year with no damage. The coax from that tower lead into a building full of electronics more delicate than anything on your boat.

What's the difference between a broadcast tower and a sailboat mast? There's water under a boat.

Bonding. Grounding (a relative term - seawater is more conductive than the dirt under the broadcast tower). Surge protection.

Do those three things right, and you shouldn't have a problem. Or, you can just blame the capricious lightning gods for smiting your boat with fire from the sky. Everyone in the 17th century would agree with you.

Ok Pat, then specifically how do you implement an effective lightening grounding/bonding/surge protection system on a boat?

There are already a number of systems on the market, and DIY approaches. Per insurance stats, none of them make any difference.

[belizesailor]

Originally Posted by Pegu Club

Exactly, bonded or not bonded, brushy thingy on the mast top or not, etc etc, means nothing to any lightning scenario one may find themselves in. Not all that long ago we found ourselves in one hell of a lightning storm off the Maryland coast, at night of course..., lightning was sky to water all around us, there was no conceivable reason we were not hit, Forty minutes of pure psychological trauma, accompanied by the obligatory forty plus mph winds, call it what you like, but it’s all luck of the draw. The gods were smiling upon us that night, [emoji3]



Fair winds,

Been there done that several times and each time was amazed we were not struck. Ive seem boats struck, had 2 of my own boats struck, but have never been aboard a vessel ehen it was struck.

One of the riskiest situations for actual personal injury is being in a small open boat. YOU are now the highest object around. Ive been caught out in lightening storms in small open boats too, that is very unnerving.

[belizesailor]

Originally Posted by atoll

you could fast charge your new Lipo battery bank,,,,,,,,,,,

I have some AGM batterys ashore which the specs say have an "unlimited" charge absorption rate. When its time to retire them, Im going to hook a lightening rod to them and test that spec!

[Cpt Pat]

Originally Posted by belizesailor

Ok Pat, then specifically how do you implement an effective lightening grounding/bonding/surge protection system on a boat?

There are already a number of systems on the market, and DIY approaches. Per insurance stats, none of them make any difference.

See post #41 above: https://www.cruisersforum.com/forums...ml#post3177415

> Per insurance stats, none of them make any difference.

The insurance companies only ever see the failures. How often do you call your auto insurance company, for example, to tell them you have not had an accident?

And I'd like to see those stats. Please provide a reference. I'm a incredulous that anyone but a fool would say: "Give up. It's hopeless. Surrender to Fate." That strikes me as just an excuse to be lazy.

[robert sailor]

Originally Posted by slug

I’ve been sailing metal boats for decades

Many lightning strikes

Never catastrophic damage

Yes of course but lightning easily exists a steel hull. Your not getting holes blown in it, no pin holes around the waterline. You may get hit but I doubt you’ve ever had any structural damage done,

[CdS2 Roland]

Hello,
I'am owning an aluminium SV. Have heard that it won't be hit by lightning... Not true. Happened early morning in San-Blas/Panama. Everything electric burned, 25K USD damages, no injuries. Best thing we did before? An insurance that cover lightning.

[Hermia II]

The first thing to think about is that all electronics is very vulnerable to lightning. I have had instruments go Coco by a far away lightning strike. So paper charts are mandatory, and having a second electronic option is also good, one thet can be put in the oven (iPad for example) or any other Faradays Box.

[belizesailor]

Originally Posted by Cpt Pat

See post #41 above: https://www.cruisersforum.com/forums...ml#post3177415

> Per insurance stats, none of them make any difference.

The insurance companies only ever see the failures. How often do you call your auto insurance company, for example, to tell them you have not had an accident?

And I'd like to see those stats. Please provide a reference. I'm a incredulous that anyone but a fool would say: "Give up. It's hopeless. Surrender to Fate." That strikes me as just an excuse to be lazy.

Has your configuration been tested by an actual strike?

The stats are from BoatUS. I will look them up.

One interesting thing from their stats is that Catamarans are more likely to get struck than Monos.

[belizesailor]

Originally Posted by belizesailor

Has your configuration been tested by an actual strike?

The stats are from BoatUS. I will look them up.

One interesting thing from their stats is that Catamarans are more likely to get struck than Monos.

Looked up a related BoatUS article. Link below. As I recall more detailed data was also availble, but havent found it again yet.

https://www.boatus.com/seaworthy/mag...ning-facts.asp

At the end of the article there is an updated article on lightning protection. They note that conventional systems sold to boaters as "lightning protection" are not proven to be effective and go on to describe a system more like Cpt Pat suggested.

[malbert73]

Originally Posted by fxarcher

I wanted to call everyone's attention to a blogcast on "On the Wind Sailing", a blog produced by 59 North I listened to on Stitcher.
The episode on April 28, 2020, featuring Jeff Thayer.
Jeff is a scientist who did research on lightning for the space program.

I found it to be the most informative info I ever heard on a subject that is much discussed and little understood.

For what it’s worth I listened to the podcast as well and The naysayers on this thread ought to listen as well before dismissing. The part about an oven not working as a faraday cage, and relative wind speed at masthead affecting your chances of being hit- supporting possibly running off downwind during offshore squall to reduce your chances- very interesting and worth thinking about.

And yes there is no way to prevent your number being called completely

[Cpt Pat]

Originally Posted by belizesailor

Has your configuration been tested by an actual strike?

The stats are from BoatUS. I will look them up.

One interesting thing from their stats is that Catamarans are more likely to get struck than Monos.

Tested in an actual strike? Are you joking? No, I don't have mystical powers to call down lightning bolts from the heavens and direct them at my own boat. And I haven't installed scientific instruments on my boat to record strikes. All I do know is my neighbors have suffered all sorts of failures with their onboard electronics immediately after thunderstorms that I have never experienced. And I've got a LOT of electronics on board. I'm a Ham radio operator - my boat is packed with radios.

Catamarans typically don't have a straight path from the mast step to the water. Energy from lightning typically has to make two 90 degree turns from the mast step to reach the water. (That situation is easily correctable.) And as any radio engineer will tell you, any current besides DC will see sharp turns as a form of impedance that dissipates power at the point of the turn.* Lightning isn't DC. So, cats may not be hit more often, but the consequences are worse. From the perspective of an insurance company - catamarans will seem more prone to lightning strikes only because they will comprise a larger percentage of claims.

In aviation, it would appear - looking through flawed logic - that 100% of of accidental spin encounters are fatal -- only because anyone who recovers from a spin won't have a reason to report it to the NTSB or their insurance company. It's the same flawed logic that would make catamarans appear to be "attracting" lightning.


* RF doesn't like sharp bends. They are like a partial turn in an air-core transformer that produce inductance -- a complex topic having to do with the generation of an electromotive force that is way past the scope of this discussion. I'll refer you to the discoveries of Joseph Henry for details.

[belizesailor]

Originally Posted by Cpt Pat

Tested in an actual strike? Are you joking? No, I don't have mystical powers to call down lightning bolts from the heavens and direct them at my own boat. And I haven't installed scientific instruments on my boat to record strikes. All I do know is my neighbors have suffered all sorts of failures with their onboard electronics immediately after thunderstorms that I have never experienced.

Catamarans typically don't have a straight path from the mast step to the water. Energy from lightning typically has to make two 90 degree turns to reach the water. And as any radio engineer will tell you, any current besides DC will see sharp turns as a form of impedance. So, cats may not be hot more often, but the consequences are worse.

Nope, not joking. The theory may be the same, but does it actually work the same on the water vs on land. All info seems to infer that the products current sold for this purpose to the boating market dont do jack.

The configuration you propose seems practical to me, but have you or anyone else ever actually taken a strike with this configuration in place?

[Cpt Pat]

Originally Posted by belizesailor

Nope, not joking. The theory may be the same, but does it actually work the same on the water vs on land. All info seems to infer that the products current sold for this purpose to the boating market dont do jack.

The configuration you propose seems practical to me, but have you or anyone else ever actually taken a strike with this configuration in place?

If lightning doesn't do any damage to my boat, how would I ever know when it was struck? You are welcome to set up surveillance cameras to see when my boat is hit.

As I explained above: my evidence is the absence of damage to my boat when boats all around and nearby were damaged.

And I agree, the commercial products sold specifically for protecting boats is at best junk - and at worst dangerous junk: like dynaplates. Snake oil mostly. Protecting a boat doesn't require a lot of money and gadgets - it requires a knowledge of lightning behavior, good engineering and only a few materials. I can't see how a company could make a "product" out of good basic engineering. You can't put that in a box and ship it. Those who think it's hopeless have no motivation to acquire the knowledge. Lightning damage then becomes a self-fulfilling prophesy.

I'm retired from NASA. NASA did a lot of research on lightning because they frequently launch from one of the most lightning-prone areas: Florida, and the smoke from a rocket trail is ionized and partially conductive. From the perspective of lightning, every launch is a big lightning rod ascending in the sky. The Apollo 12 launch vehicle got struck by lightning twice (disproving the adage that "lightning never strikes the same place twice"). After that, they did a great deal of research into lightning. That knowledge has just never trickled down to boaters. And it never will if boaters believe there is nothing they can do to protect their boats. The "barrier of ignorance."

Benjamin Franklin, the inventor of the lightning rod, encountered the same resistance hundreds of years ago. It's an interesting story of religious beliefs versus science. (Science got its revenge: churches, often being the tallest building in a village, were the most frequently struck structures - and it's rare today to see a churches in lightning prone areas that don't have lightning rods.)

Most people's mental model of lightning is upside-down. The next time you see a launch on TV, look for towers surrounding the launch pad.* Those are ground charge dissipators that dissipate static charge buildup. They work, because lightning actually starts from the ground up. A good suppression system will prevent the strike from occurring in the first place. So, no, I am happy to report to you that I have no evidence my boat has ever been struck by lightning. Because my system works!

* https://www.nasa.gov/centers/kennedy...ain_LPS-08.pdf

[Wallaby]

Originally Posted by Cpt Pat

1) I use TVS (transient voltage suppression) diodes across every power input to every load, as near the load as possible. Zener diodes work too, but the junctions saturate at lower currents. Here's an example diode for 12 volt buses: https://www.digikey.com/product-deta...ACT-ND/2770240. Those'll cost you 59 cents each.
.....................stuff omitted.............................
Your VHF antenna at your masthead could still become a "sacrificial air terminal" for lightning. But with a good suppressor, the damage should stop there.

Thank you very much. This is extremely helpful. There are several issues I was not aware off, and I will be including on my boat.



One thing is clear--an actual strike is a matter of bad luck--wrong place, wrong time. However, you can minimize the damage, and keep the boat afloat. Maybe even save some electronics. On my one strike about 10 years ago, there were even cuts in the aluminum mast as if the lightning wrapped around it. The high-copper anti-fouling was gone for about six inches around every bonded thru-hull. The surveyor could not FIND the exit wound, much to amusement of myself and the yard owner.
Regarding surge protection on antennae, my 4ft VHF antenna was zapped to nothing--pieces found on the deck. Now, I protect both the VHF and SSB as you recommend.



Anything with a circuit board went in the trash. This included a lot of electronics, including some you don't think about like regulator and refrigeration,



The only good news, 5 brand new Lifeline AGM batteries, which the local auto-electrician declared DOA, were recharged and fully restored--thanks to a Lifeline technician.