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aiprt
02-01-2014, 11:30 AM
Hi all,

Re-reading a 1997 issue of WB this morning, I came across Jonathan Klopman's article on lightning ground systems.
A quick search yielded
http://forum.woodenboat.com/showthread.php?128358-lightning-protection-design-for-wooden-sailboats-with-wooden-masts
http://forum.woodenboat.com/showthread.php?126751-built-in-lightning-protector-in-a-new-wooden-mast-construction
And also Klopman's article :
https://www.woodenboat.com/lightning-ground-systems

Lots of discussion on the forum as to whom to trust and whom not to trust, or does anyone know anything about lightnings etc.

But :


Has anyone around done it on his wooden mast boat ?
If so, can you describe what exactly you installed ?



With a gaff rig (no metal sail track), how about a copper conductor down from a pointed lightning pole to the bronze mast band, then using the shrouds down to the chainplates, then inside the boat a solid copper restangular conductor along the skin down to some keel bolt(s) ?

Naturally I would avoid leaning back on the conductors during a thunderstorm...



Now, shoudn't the keel ballast make contact with the water ?

There is paint, fiber glass, epoxy down there...

slug
02-01-2014, 01:11 PM
Lightning travels down the rigging.

be sure that the blast can exit the rigging and into the sea.

A big boat would use copper conductors from chainplate to lead keel.

i dont know how a small craft , with no lead keel, would discharge the blast.

ahp
02-01-2014, 01:39 PM
I have heard of sailors clipping a short length of chain onto the shrouds with the other end dangling in the water.

Rich Jones
02-01-2014, 01:55 PM
On my gaff rigger, I ran wire from the chainplates to the lead keel.

aiprt
02-01-2014, 03:17 PM
On my gaff rigger, I ran wire from the chainplates to the lead keel.

What is unclear to me is, what treatment for the lead keel ?
In my project it will be painted, so how does one achieve good electrical contact with the ocean ?

slug
02-01-2014, 03:25 PM
I suspect the the lightning simply arcs thru the paint film on the lead keel.

If your boat it complex then all metal objects in the boat should be earthed together with copper cabe and dead ended at the keel bolt.
Metal objects would be water tanks, engine, shafting......

this is done so that the bolt doesnt jump from chainplate to water tank or engine as it tries to escape.

Breakaway
02-01-2014, 03:52 PM
Copper paint for one thing....

But more likely...

....the charge is high and active. I have seen lightning strike damage ( after the fact) that blew a hole through the hull. Paint isn't likely to stop it--probably just burns through it.

Would you touch a live wire with painted hands?

Kevin

the_gr8t_waldo
02-01-2014, 04:17 PM
I believe that to compare "a energized wire" to an electrical strike is misleading. One can be assumed to be,120-480vac and the other is tens of thousand volts dc. In either case , I wouldn't think paint would offer much in the way of resistance on the lead ballast to water interface . I picture a lighting strike ,explosively blowing off an area big enough to allow discharge to the waters. Fwiw, in the case of energized wires, accumulated job site dirt on the hands,does lessen the effects aceidental contact with energized conductors to that area. Dryed paint on the hands would probably serve as well. any one not trained for it, has no business thinking about touching live wires. The real trouble with marine based lighting protection is the number of connections required to create a circuit from lighting rod to ballast. Each connection has to be in "top notch" condition. All connections are subject to loosing up and corrosion, reducing ability to conduct. All electricity will take the path of less resistance . Who knows where the energy will leave the intended path and what the new path will be? Could, we'll be, more excitement than if you didn't try to channel it thru the boat to water in the first place

aiprt
02-01-2014, 04:45 PM
I suspect the the lightning simply arcs thru the paint film on the lead keel.

If your boat it complex then all metal objects in the boat should be earthed together with copper cabe and dead ended at the keel bolt.
Metal objects would be water tanks, engine, shafting....


Agreed. Engine, shaft I believe will automatically be connected to the engine.
Also provision must be made to disconnect the VHF from the coax running down direct from the masthead.


https://www.woodenboat.com/sites/default/files/bonus-content/lightning_7.jpg

aiprt
02-01-2014, 04:47 PM
http://i.telegraph.co.uk/multimedia/archive/01443/lightning_1443666f.jpg

Bob Cleek
02-01-2014, 05:02 PM
Sigh...

A lot more boats have been "cooked" by electrolytic action as a result of "bonding" all the metal parts than have ever been damaged by lightning. (Lightning rods on wooden buildings are bonded with a large metal strap to ground, not wires.) Bonding for that purpose is besides the point anyway. The power of a lightning strike is so much greater than the conductive ability of a wire that, at best, a wire is only going to direct the force and heat where you least want it... inside your boat! The shape of most rigging arrangements is such that it provides a "cone of conductivity" that directs a strike downwards and outwards, to the water. Your mileage may vary, but consider this: If lightning strikes to boats were a risk worthy of doing anything about, don't you think every boat would be equipped with some sort of protective device?

jimL55804
02-01-2014, 05:16 PM
Half way through the build of our BayCruiser 20, It occurred to me that we were building something of a lightning bomb to be sailed in a lightning prone area. The combination of carbon fiber mast, water ballast tanks and a completely non-conductive wood/epoxy/glass hull became an issue, at least in my head. Carbon fiber is conductive but epoxy is not. My understanding is that carbon fiber/epoxy structures tend to explode with nasty carbon fiber shrapnel in a situation like a lightning strike. Once the lightning bolt exited my exploding mast, my mind's eye saw it arcing wildly through the cabin and cockpit into forward and aft the ballast tanks looking for the best path out as it blew holes in the bottom as a parting shot.
If you try and study up on the right thing to do, there isn't just one answer. I really don't know if what I did is any more effective than some random pre-voyage magic incantation, but I felt the need to do something. We started on top with an air terminal that consists of several inches of aluminum rod above and passing through a custom (homemade) masthead LED anchor light. Inside the mast it is crimped and soldered to a beefy aluminum cable of the sort that would be used for a terrestrial lightning rod. This comes out of the doug fir mast base and connects to a terminal in a run of aluminum bar stock that is connected with a beefy aluminum bolt through the stem at deck level to an aluminum band running the full length of the keel, giving ample grounding. I don't know if this will work and I hope I never find out, but I feel better (perhaps foolishly) for having done something.

Jim

aiprt
02-01-2014, 05:34 PM
Bob,

Not sure I get your point.
Metal straps or bars, yes. Some regulation call for conductors as large as AWG 4 or 6, hence the reference to wires. Or cables for that matter.
No problem with straps in a building, since most angles are 90°.
Different story in a boat, but no problem : when they will re-wire my home, I'll set my hands on those cute copper bus bars running up and down the whole building...

One question though : how do you direct the energy from the chainplates to the water ?
Since they cannot run outside the hull, the conductors (straps, bars, whatever) have to run inside the boat.


consider this: If lightning strikes to boats were a risk worthy of doing anything about, don't you think every boat would be equipped with some sort of protective device?

Not sure of that one. Do you mean that a lightning strike on a boat is an unlikely event that doesn't deserve any attention ?
But why lightning protection norms and standards then ?
I have been amid thunderstorms - on land - and at times I wouldn't have dared stand upright in the open. What about being caught at sea ?

the_gr8t_waldo
02-01-2014, 05:42 PM
Wires or metal buss bars...it Dosen't.t really matter as long as you see to it that the cross sections of the ribbon conductor is the same as the wire size...this as a minimum!

donald branscom
02-01-2014, 05:58 PM
Sigh...

A lot more boats have been "cooked" by electrolytic action as a result of "bonding" all the metal parts than have ever been damaged by lightning. (Lightning rods on wooden buildings are bonded with a large metal strap to ground, not wires.) Bonding for that purpose is besides the point anyway. The power of a lightning strike is so much greater than the conductive ability of a wire that, at best, a wire is only going to direct the force and heat where you least want it... inside your boat! The shape of most rigging arrangements is such that it provides a "cone of conductivity" that directs a strike downwards and outwards, to the water. Your mileage may vary, but consider this: If lightning strikes to boats were a risk worthy of doing anything about, don't you think every boat would be equipped with some sort of protective device?

I agree.
Do not bond all electronics together,unless you want to lose them all at once.
It has happened.

aiprt
02-01-2014, 06:20 PM
I agree.
Do not bond all electronics together,unless you want to lose them all at once.
It has happened.

It was only question of bonding large metal masses, ie engine to the lead keel ground.
Also disconnecting the radio from the coax descending from the antenna. The boatronics won't be connected to anything dangerous.

kc8pql
02-01-2014, 06:38 PM
consider this: If lightning strikes to boats were a risk worthy of doing anything about, don't you think every boat would be equipped with some sort of protective device?

You apparently don't live in a thunderstorm prone area. In places like S. Florida, where storms happen every afternoon for nine months of the year, the risk is quite real.

I also agree that it's probably not a good idea to get electronics involved in the lightening ground. My brother in law's aluminum masted sailboat sank at the dock when a strike blew the depth finder transponder out of the bottom of the boat.

Ron Williamson
02-01-2014, 06:46 PM
It's hard to imagine that lightning wouldn't blast your coax disconnect and your vhf if it had already just arced across a few thousand yards of sky to your boat.
IIRC,it takes a million odd volts to arc an inch.
R

aiprt
02-01-2014, 07:22 PM
It's hard to imagine that lightning wouldn't blast your coax disconnect and your vhf if it had already just arced across a few thousand yards of sky to your boat.
IIRC,it takes a million odd volts to arc an inch.
R

Ron,

When I was a kid I went to sea with my father who was a radio operator on large trawlers. On the ceiling of the radio shack were large knife disconnectors for the antennas, so maybe at the time was there some justification in disconnecting the cables and wave-guides from the electronics.
Now if there was a direct path to ground, why would an arc jump to the non-grounded part of the circuit ?
Of course there could be cross flashes everywhere between various parts of the boat, but at least the main flow of energy has a devoted path.

As a comparison all passenger aircraft get hit on a regular basis inflight, and yet usually no special damage occur.
In some cases you'll find extensive damage to radomes, for instance, but it is very unfrequent to have the avionics go toast.

So, while lightning strikes seem to happen at random, someone must know something about mitigating the risks. The standards are a picture of what can be done according to the best knowledge at the moment.
Also those disconnectors, exploders, etc. have been tested full size with high voltage lightning generators, so why not give them a try ?

Breakaway
02-01-2014, 08:18 PM
Re electronics : I've twice been offshore when a lightning strike near to the boat knocked out the electronics. No direct it.

On balance I have been in a boat In a thunderstorms dozens of times and nothing happened.

Kevin

Sent from my iPhone using Forum Runner

Breakaway
02-01-2014, 08:21 PM
Ron,

When I was a kid I went to sea with my father who was a radio operator on large trawlers. On the ceiling of the radio shack were large knife disconnectors for the antennas, so maybe at the time was there some justification in disconnecting the cables and wave-guides from the electronics.
Now if there was a direct path to ground, why would an arc jump to the non-grounded part of the circuit ?
Of course there could be cross flashes everywhere between various parts of the boat, but at least the main flow of energy has a devoted path.

As a comparison all passenger aircraft get hit on a regular basis inflight, and yet usually no special damage occur.
In some cases you'll find extensive damage to radomes, for instance, but it is very unfrequent to have the avionics go toast.

So, while lightning strikes seem to happen at random, someone must know something about mitigating the risks. The standards are a picture of what can be done according to the best knowledge at the moment.
Also those disconnectors, exploders, etc. have been tested full size with high voltage lightning generators, so why not give them a try ?

But they are not grounded in flight?

Kevin

Sent from my iPhone using Forum Runner

brucemoffatt
02-01-2014, 08:41 PM
For what it's worth (free advice is probably worth what you pay for it) I've sailed a small boat through an intense lightning storm once. It had an aluminium mast, so remembering all I'd read about the 'cone of protection under the stays/shrouds' and 'pathways of least resistance' I wrapped chain around the base of the mast then out and down into the sea, dragging a sizeable length along with us. This did not reassure me one little bit as the lightning flashed all round us. At one stage we were relatively close to a lightning strike on the water, that appeared to be no more than a mile away. In fact it looked a lot closer, but it's hard to tell. The sea fluoresced at the strike, giving the impression that a large volume of water had just been vaporised, but that was an illusion of the light. The thunder was very close after the lightning, and was deafening. What impressed me was the scale of it. Had we been struck I doubt that the jury-rigged grounding device would have offered any much protection to the boat or crew at all. It was humbling, in the most profound way, to see how much energy was being instantly released. I respectfully suggest that the notion of running a conductive strip down the mast then to the sea would be a comfort to the crew but probably not a life-saving device, should the mast be struck by a substantial lightning discharge. Happy to be proven wrong though :)

aiprt
02-01-2014, 09:07 PM
But they are not grounded in flight?



Neither are we usually in a boat^^!
When an object is "hit" by a bolt of lightning, it serves as a conductor between a large positive charge and a large not so positive charge (or the other way round if you prefer^^).
A boat acts as a conductor between say a cloud and the sea, and an airplane does the same between say two "clouds", or a cloud and the ground, or a cloud and the sea, etc...
What matters finally is being able to offer a path for the energy with as small inconvenients as possible for those onboard or their systems.

Breakaway
02-01-2014, 09:29 PM
Interesting map

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Global_lightning_strikes.png/800px-Global_lightning_strikes.png (http://upload.wikimedia.org/wikipedia/commons/c/c5/Global_lightning_strikes.png)

Sayla
02-01-2014, 10:10 PM
Hi all,

Lots of discussion on the forum as to whom to trust and whom not to trust, or does anyone know anything about lightnings etc.



Have a listen to this podcast

http://furledsails.com/article.php3?article=676

BBSebens
02-02-2014, 02:18 AM
Most commercial aircraft possess aluminum skins which give the lightning a nice easy path to follow.

not sure what is done on the all carbon fiber 787 Dreamliner.

Old Frog
02-02-2014, 09:00 AM
You would be well served to consult the standards NFPA, & NMEA, etc., ABYC's technical information report (they down graded their standard to a tech report), and the recommendations of your electronics manufacturer. Also interesting is the work of Dr. Ewen Thomson (MarineLightening.com). Likewise, Don Street's comments in his Ocean Sailing Yacht books are worth the reading time. It you carry insurance on your boat, inquire of your agent/carrier about relevant policy language that might apply.

You will find that there is currently no accepted marine lightening standard or guide. Rather there are various theories (ie. "cone of protection" "rolling sphere of protection", Dr. Thomson's work, etc.) some of which carry the status of a standard, some do not. You may find that it is pretty impractical to install many/most of the recommendations in the typical boat or yacht. Some have concluded that Mr. Street's suggestion may have merit.

"You pays your money and you takes your choices (or chances)" might be the best way to sum it up.

Dave Hadfield
02-02-2014, 09:22 AM
Airliners have static-charge "wicks", several on each wingtip, to dissipate the static charge that may build up. This helps make the structure less visible to lightning. I have had several "strikes" in my flying career, but they are really just static discharges that happen when conditions change too rapidly.

My strategy when sailing is to be near a modern sloop with a tall aluminum mast. Better him than me.

Dave

Old Frog
02-02-2014, 09:29 AM
My strategy when sailing is to be near a modern sloop with a tall aluminum mast. Better him than me. Dave

Some wisdom with that approach. Also, do not umbilical tether to shore power.

seo
02-02-2014, 12:57 PM
Probably the best rig for a gaff rigged would be a solid copper rod at the masthead, attached to copper lightning ground cables seized to the shrouds running down past the deadeyes and lanyards, and then at the rail or down at the channels (you didn't say how old-timey this boat is…) connecting to a flat copper strap that runs down the hull and below the WL. No need to extend the strap down to the keel. One square foot of copper is adequate, and there are companies that make discharge fittings that live just above the WL.
The problem with bringing lightning strikes down the mast and to the keel is that in most yachts that means bringing the strike down into the space occupied by people. Also, Inside the hull you can get unpredictable side-flashes to metal masses like tanks, etc, and can also get a side flash right out through the hull.
The system I described above creates a sort of "Farraday cage" that will provide a low resistance path to ground on the OUTSIDE of the protected area, creating an envelope of protection.
A lightning ground system is not an electrical bonding system, which connects throughhulls, engines, tanks, etc, together with a lighter gauge conductor. Bonding is primarily intended to keep people from being electrocuted by faulty shore power systems. Many people feel that these systems cause deterioration in a wooden hull, particularly if the boat is kept connected to shore power.
All of this said, lightning isn't entirely predictable. Boats with very extensive systems can be struck, and boats without any protection might serenely sail through a gulf stream thunderstorm with no trouble. The other thing that's pretty sure is that if you're struck by lightning and your electronics nav/com gizmos are connected to their aerials, they will probably be toast.

jimL55804
02-02-2014, 01:46 PM
...............The system I described above creates a sort of "Farraday cage" that will provide a low resistance path to ground on the OUTSIDE of the protected area, creating an envelope of protection............
The system that seo describes is pretty much just what we did but with aluminum components. Aluminum was used for weight and cost savings but I think that I would do copper if I wasn't mostly in the Great Lakes. Everything in our system is at least as big as the aluminum cable in the mast, which is sized for just this purpose in terrestrial systems, so I think that we are good. It is my understanding that you want a pretty smooth path for the current to follow, that kinks and quick turns increase the chance of the current finding another route. I don't know how well we did on that account. I may think more about this than some since I grew up hearing my dad's story (over and over) of his brush with death getting hit by lightning as a kid.

Jim

CliveP
02-02-2014, 02:19 PM
To paraphrase Breakaway...There are 2 kinds of boaters. Those who have run a ground, and those who lie about it.
Clive P

Don Kurylko
02-02-2014, 03:22 PM
How about a gaff cutter with wooden spars, Dynex Dux polyethylene standing rigging and no wiring of any kind. Basically, a completely isolated structure with no conductive material to provide a path for lightening, except perhaps wet spars and rigging. Would such a vessel attract strikes? Would a strike remain localized and simply dissipate or, at worst, blow the top of the mast off - hopefully, the separate top mast?

John Meachen
02-02-2014, 05:40 PM
I am in the don't know camp on this one.I have been less than quarter of a mile from a grp cruising boat that had its masthead electronics vapourised by a lightning strike,but which appeared otherwise unharmed.I also know of an elderly wooden hull that was sunk after lightning travelled down the shrouds and chain plates and loosened the fastenings.The movement of the fastenings on the t&g bulkhead shattered a mirror that then sent shards into the rest of the cabin.Lucky nobody was in there.Fortunately the boat was moored in around four feet of water and could be salvaged and repaired.

aiprt
02-02-2014, 07:24 PM
Probably the best rig for a gaff rigged would be a solid copper rod at the masthead, attached to copper lightning ground cables seized to the shrouds running down past the deadeyes and lanyards, and then at the rail or down at the channels (you didn't say how old-timey this boat is…) connecting to a flat copper strap that runs down the hull and below the WL. No need to extend the strap down to the keel. One square foot of copper is adequate, and there are companies that make discharge fittings that live just above the WL.

Seo, thank you for your contribution.
The project is a Golant Gaffer.
http://www.classicmarine.co.uk/images/golant_2-_b27.jpg
http://seashellboats.co.uk/golant-gaffer/

Not particularly old design. The shrouds would be tensioned with turnbuckles.
Not sure I'd care for additional conductors tied to the shrouds. Windage and apparence...
Also I was trying to discover a way do run copper straps along the hull without creating too much drag (the straps would lay across the flow of water in the area of max girth) or too ugly a setup. Maybe using some metal stem/keel band or stern post band...?

Old Frog
02-02-2014, 07:29 PM
One thing to keep in mind as you move forward with a system/or no system and remember if you are caught onboard during nearby lightening activity, is how the boat is configured and what system, if any, exists. Consider the boat configuration of a backstay near a pedestal or similar helm that is connected to the rudder by conductive components (ie. cable pedestal system or worm gear). It is not wise to be between the backstay and the helm (very common on modern sloop rigs). I know first had of such a lightening related injury (amazingly, the person was only dazed and lived to tell the tale). Also, in in the cabin during an event, consider the rig, chainplates, metalic masses, etc., it is not wise to be between the components. The addage of bend over & kiss ones arse goodby may apply.

seo
02-04-2014, 08:45 PM
Post #33 raises a very good point. Taken to its logical conclusion, "is there a lightning ground system for an epoxy/kevlar whitewater kayak?" My reply would be that the risk of a casualty caused by lightning strike is vanishing small.
In response to #35, if carefully done a lightning conductor could be seized aft of the main shroud, and wouldn't be conspicuous and might cause you rig to have LESS wind resistance. Also, there's no reason why a 1.5" wide copper strip, 1/32" thick, well faired in, should be visible to either the hull resistance gods OR the arbiters of this week's Old Timey Original Fashion awards.
In #36, "Old Frog" makes an excellent point, one that has struck me with stunning immediacy as I sat with a bronze wheel in my hand, right under the backstay, the wheel was connected by the steering cables to the bronze rudder shaft, direct to the sea. I appreciated the fact that there was a grounding strip from the backstay chainplate to the water, but couldn't help but calculate the "path to ground Length vs resistance" equation, and cringe away from the wheel.

Richard of Woods Designs
02-04-2014, 09:05 PM
I scan read the posts. I think I am the only one so far to have actually been hit by lightning (on my 32ft Eclipse catamaran while motoring in Pamlico Sound). You can read about it here

http://www.sailingcatamarans.com/index.php/articles/11-technical-articles/47-lightning-strikes-on-eclipse-2003

Another useful/scary read is here

http://dominocatamaran.blogspot.com/2013/07/lightning-survey-results.html?q=lightning

The world expert is Ewen Thomson see here

http://www.marinelightning.com/

Unballasted boats (like multihulls), are more prone to lightning strikes, you are more at risk in fresh water (it's not such a good conductor)

The low incidence of lightning in the PNW was a major factor in our decision to buy a house in Port Townsend

Richard Woods of Woods Designs

www.sailingcatamarans.com (http://www.sailingcatamarans.com)

Larks
02-05-2014, 02:16 AM
While cruising up through Indonesia, Singapore, Malaysia during the storm season I was advised by triple circumnavigation sailor Jon Sanders to trail jumper leads from my shrouds when there was lightning about. (40' FG Laurent Giles Salar 40).

As far as I am concerned it worked....I was never struck by lightning!!!
(A bit like the question: why does an elephant paint it's feet white? Answer: So that it can hide in the clouds!......Question: Have you ever seen an elephant hiding in the clouds? Answer: No ........ See, it works!)

I also disconnected everything electrical or electronic and made sure there was a good air gap between leads and sockets

But I did watch, within about a five minute period during one storm, as three yachts around me anchored off of the Changi Yacht club Singapore, were hit by lightning. Luck of the draw?

aiprt
02-05-2014, 07:34 AM
I scan read the posts. I think I am the only one so far to have actually been hit by lightning (on my 32ft Eclipse catamaran while motoring in Pamlico Sound). You can read about it here

http://www.sailingcatamarans.com/index.php/articles/11-technical-articles/47-lightning-strikes-on-eclipse-2003


Richard,

Thank you for this first hand account. Scary indeed. Lots of things to ponder re lightning protection.

seo
02-05-2014, 09:50 AM
On Good Friday, 1990 I was sailing as bosun on a T5 tanker underway light ship from Boston to Baton Rouge. We were right on the outside of the Gulf Stream, riding a countercurrent. At the time we were "blowing tanks," which on an old (1956) ship like this involves opening up the tank cover plates, and setting up steam powered blowers in the open holes, blowing fresh air in, so that the fuel gasoline vapors in the tanks would be blown out through the open tank top.
The crew had worked very hard getting the covers off, the steam hoses out, and the blowers rigged up and howling, and I'd knocked them off for coffee while the blowers did their work.
I remember this very clearly.We were right in the scary part, when the vapors pouring out the tank tops and over the deck were right in the flammable range. One spark and WHOOOMP!
This was part of the reason I'd knocked the crew off-the fewer people on deck, the less likely that someone might drop a steel tool on a steel deck, striking a spark. The fumes were pretty thick, and the Mate and I were standing up on the Forecastle head, enjoying the sweet fresh air the was blowing over us.
I remember that it was Good Friday, because I said to the Mate that maybe we could let the deck gang celebrate the day with no work except for moving blowers from tank to tank, which isn't very hard work. And there'd be no day off on Easter, because everyone would be 60' down in the decks, "Mucking out" the tanks so that we could load jet fuel in Baton Rouge. The mate said "Good Friday? What the f**k are we taking that off for?" Those words were still hanging in the air when a bolt of lightning hit the ship with an explosive blast, stunning both of us. I remember standing there, the two of us staring at each other, waiting for a cloud of flame to ingulf the deck. He looked very young, all of a sudden, with all the toughness wiped off his face. I'm sure I looked the same. The seconds went past very slowly, and very slowly we realized that we weren't going to die. I looked up at the wheelhouse windows, where the Captain and the 3rd mate were staring down at us.
Finally the Mate spoke.
"Good Friday, huh" he said.
"Yes," I answered.
"Okay. Good Friday." he said.
On the way back to after house where the galley was located, I came across the medium frequency radio antenna, a copper cable that ran from the wheelhouse 300 feet back to the stack deck. It was neatly melted in two. Instead of landing on the tank deck, the hot end of the cable had landed on the cat walk, eight feet above the deck.
What were the odds of that?

Old Frog
02-05-2014, 11:44 AM
In reference to SEO's above, one event that remains clear in my memory, even 3+ decades later: Early one morning I was in a group of 14 on a hard run. We were coming down a grade on an isolated road in a remote area. While the weather was clear, it was dead still, not even the normal animal sounds, and it was evident it would storm later that day. Someone mentioned God. Kodiak, who professed to be an atheist, replied very unkindly what God could do. There was an immediate flash, deafening crack, static and a tree that was hit by lightening just off the road ahead less than 100 yards ahead. Some of us actually had hit the deck attempting to seek cover. I never heard Kodiak make a disparaging comment about God after that. Those things do happen.

jpatrick
02-05-2014, 05:14 PM
If a god exacted retribution every time one took his/her name in vain, I'd be dead a thousand times over. Matter of fact, I'd have not been born because my dad invented the phrase.

Tom Robb
02-05-2014, 07:09 PM
Lots of great stories. Interesting anecdotal stuff. Not much expertise.
Has anyone asked the insurance companies?
They have lots of actual data. It costs them lots of money if they don't.

Richard of Woods Designs
02-05-2014, 08:56 PM
Yes I did, (in fact I had a long talk with an insurer) so did Domino, see the links above. Mind you I didn't claim for my strike as I wasn't insured for lightning damage. I suspect that many cruisers are like me.

After being hit I fitted a "Strikeshield" although I don't think it is made any more. I was never hit again. We were anchored for a month in the "swimming pool" in the San Blas islands of Panama (if you go there you'll know how it earned its nickname) with 11 other boats all around us. In one storm 6 boats were hit by lightning, including the boat nearest us. But we weren't.

This is the anchorage where Domino was hit a few years later.

Richard Woods

ScudderPt
02-06-2014, 12:19 AM
Hanging chain from the chainplates to dangle them in the water has been mentioned but no one has said if this is effective. I have an aluminum mast, stepped on the keel with galv steel shrouds and chainplate. Would chain hanging from the shrouds provide enough of a path or would it be likely that the charge would go down the mast and then through the bottom of my wooden boat. Looks like I should have heavy copper wire through a copper bolt to a copper plate on the outside of the hull by the maststep and also dangle chain when in lightening storm.

Richard of Woods Designs
02-06-2014, 01:50 AM
It's of psychological help, nothing more. You really do need to have a good conductor, which means copper. The Strikeshield we had had a copper conducting wire nearly 1in in diameter. Very definitely thicker than our anchor chain. Electricity will go the path of least resistance and that means down the mast rather than a shroud. Check out Ewen Thomson's site. He was very helpful to me after I got hit

Fortunately for us, as I said earlier, the PNW is a low lightning risk area

Richard Woods

Larks
02-06-2014, 02:08 AM
Hanging chain from the chainplates to dangle them in the water has been mentioned but no one has said if this is effective. I have an aluminum mast, stepped on the keel with galv steel shrouds and chainplate. Would chain hanging from the shrouds provide enough of a path or would it be likely that the charge would go down the mast and then through the bottom of my wooden boat. Looks like I should have heavy copper wire through a copper bolt to a copper plate on the outside of the hull by the maststep and also dangle chain when in lightening storm.


I guess as usual I'm talking to myself, but as I said in post #39............... the jumper leads from shrouds worked as far as I'm concerned.........though I should add that, although it was a 40' yacht, this was a deck stepped mast ...........

Thorne
02-06-2014, 12:50 PM
I heard a talk on this topic at the NASA sailing club at Moffett Field, and the gist seemed to be that the lightning bolt tends to blast holes in the hull even if lead to the keel via straps or wires. It certainly can't hurt to run grounding lines into the water, and might give protection against nearby strikes / partial strikes, but there didn't seem to be any sort of 95% protection in the way that lightning rods can provide for most structures.

slug
02-06-2014, 01:00 PM
The energy must escape. It may well blow a hole in the hull. Ive never been holed and I been struck by lightning many times. Your best defense is to follow the standard regulations.

Lightning is unpredictable. A few years ago a small wooden sailboat that was sandwiched between much bigger sailboats was struck and sunk at the dock.

seo
02-07-2014, 10:47 AM
Copper may be the best common conductor (not as good as silver or gold), but you may notice that most houses these days are wired with Aluminum Romex wire. Aluminum is a very efficient conductor, which causes problems when you try to use steel shrouds as your lightning conductor, because steel isn't a very good conductor. If you have an alu mast, it might be best to bolt a copper jumper cable to the butt, and lead it to a bronze keel bolt, or to a dynaplate. There used to be an idea that Dynaplates weren't good for this purpose, but now they're accepted by NFPA. If you put a square foot of copper plate under the Dynaplate, you're covering all the bases.
I think that problems remain with this system: 1) You're bringing the strike through the accomodation area 2) You might get a side flash to a tanks or other metal body.
Whatever you do, DON'T connect the jumper to a through hull. Electricity discharges from metal to water at right angles to the metal, so if it's discharging from a pipe, the current will converge at the center of the pipe, and if the pipe is full of water you can have a steam explosion.
With a wood or carbon fiber mast the current "best practice" seems to be to put a lightning spike on the top of the mast, connect to copper conductors, mount discharge plates near the waterline.
NFPA 302 includes pretty succinct design guidance, but I think that if you're living in a place like Florida it might be worth it to investigate more cutting edge methods. I have interviewed people who research lightning as an academic field, and as an industry, and it seems that the money for research comes from the electrical transmission companies. They're the ones who own hundreds of thousands of miles of copper wire, high up in the air... I believe they were the first to use the "bottle brush" static dissipators that you see around.
Wooden boat with wooden masts (and sailboats in general) are a tiny segment of the industry, and I'm not sure it's really worth anyone's time to do a lot of experimenting in the field. As an example of another field, I once interviewed a provessor at the University of Minnesota who was GIVEN twin engine bombers (B-25's) right after WWII in order to research lightning effects on aircraft. One plane flew, the other was zapped while on the ground. The money came from the military, and NACA. Nobody's funding that kind of effort on wooden sailboats...

Old Frog
02-07-2014, 01:10 PM
To those looking for a succinct easy lightening ground/strike dissipation guideline, it does not exist. As SEO and earlier posts point out, NFPA might be the easiest & perhaps Dr. Thomson is the most current authoritative source. Just understand that there is not uniformity in thinking or within the "experts". The disagreement and data is such that ABYC down graded their standard to a tech info report. I hear occasional mumblings that it might be withdrawn.

I one reads & studies the recommended/suggested practices & installation of a Permanently wired "whole boat" system, one realizes that it quickly becomes very complex, difficult to accomplish, is expensive and must be maintained. The wire ga. size, direct routing, bend radius/minimization, interconnection of objects is a nice objective, but hard to obtain. Then, once accomplished, in a wooden boat, the matter of unintended consequences quickly arrises. Ie. effects of stray current, current/alkaline delignification, etc.

In the suggestion above of connecting a copper jumper to an aluminum mast and keel bolt, possible unintended consequences include but are not limited to:
1. Alu/Cu connection & corrosion issues.
2. Corrosion build up at the connection possibly defeating the jumper purpose.
3. Insufficient bend radi possibly promoting a jump if a strike dissipated via that path.
4. The creation of a partial bonding system attached to underwater metal in the boat.
5. The keel bolt condition, material, etc. Is it an effective conductor? See SEOs post above.
6. What is the ballast keel coating? Barrier coated? Conductive?, Can it effectively dissipate the strike.
7. Issues of stray current if a fault occurs in the mast wiring. Is that fault current now going to ground via your keel bolt? Is that what you want?

I agree with SEO, Dr. Thomson near W/L thru-hull discharge dissipation points make sense. But, that is a lot of thru-hulls. (Thanks but I prefer the KISS approach). If recent research is accurate of strike dissipation near to or just above the W/L, does it really make sense to ground to a keel bolt? Or engine/shaft (& risk damage to the shaft packing/dripless seal)?

In an earlier post on this thread (#36) I opined: One thing to keep in mind as you move forward with a system/or no system and remember if you are caught onboard during nearby lightening activity, is how the boat is configured and what system, if any, exists (& mentioned the backstay/helm/steering gear proximity issue & conundrum). Another example for consideration (based upon 1st hand observation): Headstay configuration vis-a-vis stem head fitting, anchor rollers, & anchor chain &/or wet rode. How close is the headstay to stemhead fitting, bow roller, stored or deployed anchor chain &/or rode.
If the mast/rigging is struck vis lightening, will the dissipation path occur:
1. Down the headstay, jump to the stemhead/roller & chain and then:
A. Down to a set anchor with no deleterious effects? or
B. Down to pile of moist/wet chain in a chain locker? If B, does it go thru the hull, or jump to wiring within the chain locker.
2. Does not travel the headstay as the masthead electronics are higher and connected to superior conductors and run directly down the mast to deck or into the cabin. Or.
3. Does it travel via both paths above & others?

In the situation I am familiar with, the boat was at anchor in salt water, had been cruising FL & the Bahamas, & had all chain anchor. It was raining at the time of the direct strike. The significant discharge appeared to have been down the headstay across to the deployed anchor chain & into the water. There was evidence of a direct mast head hit very near the headstay attachment. Under the remaining chain in the chain locker, there was an area of gelcoat discoloration but not laminate damage found. All electronics & mast lighting were "toast". The boat has not type of lightening protection. Would it have made a difference??? Who knows. The two persons onboard at the time said they knew that they were a lightening storm and did realize they were hit until later.

I was told a story some years ago (I think it occurred in the mid to late 60's if I remember the story correctly) about a quality NE boat yard that up-sold lightening protection and installation of lightening strike rods at mast head. Later the next season, one came loose, feel point first impaled into he deck. Fortunately, no one was hurt and no lasting damage was done. The story ended with the newly installed rods being removed. How true that story is, I do not know. But, given the laws of unintended consequences, it probably is. I have heard knowledgeable persons refer to the masthead brush items as lightening magnets.

As the attorneys love to say: "It all depends". In these situation, the strike magnitude, conditions, direct, indirect, nearby, boat type configuration, etc.
The issue truly is a conundrum.

If you are able to accurately predict this issues on a lightening strike, please PM me as I would like to invest in lottery tickets with you.

If nothing else, please remember the backstay/helm/steering gear issue if ever caught on deck in a lightening storm. Then would a wise time to anchor, heave to, use auto-pilot, SS gear, etc. depending upon the variables & conditions.

Ian McColgin
02-07-2014, 01:47 PM
On Goblin I would wrap some cable around the lee shrouds and trail that in the water.

Granuaile had mid-70's best thinking with carefully grounded masts and upper shrouds to discourage side flashing. All through-hulls, chainplates and the engin were bonded, so the prop could serve as an additional dissapation point.

Neither Goblin nor Granuaile was ever struck so I've no idea whether the measures would actually work in any reliable way.

I have personally known one boat that was hit by lightening - up on the hard in the boat yard - and one other hit twice while sitting at her dock surrounded by trees and higher builidings. I read of one guy who was hit twice during the same storm while anchored in a creek.

And once Mother and I were sailing about Long Island Sound and a well concentrated storm moving with the flood tide chased us from somewhere east of Mt. Siani back to Port Jeff. We were blasting in under jib alone when, just as we passed, lightening struck the light on the jetty. When my eyes cleared, Mother, who had been sitting on the bridge deck by the companionway, had disappeared. She'd actually back sommersaulted down the companion, breaking a collar bone on the way.

I lean now towards a designated braided lightening cable straight from a connection with a masthead rod down each side to a chainplate outside the hull and going down to a dissapation plate below the waterline. No mast base to keel connection except if a metal mast. Braided conductors handle the load better than solid copper for some reason. But boats with large stays can ground the rod through the stays so long as they provide a path past the turnbuckles and a gound a bit below water. If you have a fixed backstay, it should be insulated so the lightening takes a different route. Easy disconnects for all mast wiring is important. Even so, even without a current path through your chart plotter and all that stuff, the electromagnetic field of a lightening strike can do interesting mischief to modern electronics.

G'luck

seo
02-08-2014, 11:10 PM
I agree with almost everything in #53, and also with #52. I have one of those backstays with insulators in it, but I always thought they were to do with using the backstay as a radio aerial. I wonder if the problem of lightning going down the backstay would be partially solved by making the backstay out of spectra. I think it makes a lot of sense to go cruising with a spare vhf that lives in a box, ready to be installed, and a spare cable and aerial. Extend that to any electronic gizmos that you really can't get along with. A person who has pretty good understanding of high voltage electrical pulses told me that the best place for electronics during a thunderstorm is in your over. Farraday cage, I guess.

Richard of Woods Designs
02-09-2014, 01:47 AM
the best place for electronics during a thunderstorm is in your oven. Faraday cage, I guess.

Yes, that is the only thing everyone agrees on. After I was hit I made sure all my electronics was in the oven; with care it all fitted, gps, vhf, ssb, echosounder, handheld VHF and computer. These days I always install the VHF so that I can easily disconnect the antenna , even if I do nothing else. In a lightning storm I also disconnect the batteries, and stop the engine if it's running

Richard Woods

aiprt
02-09-2014, 05:47 PM
After I was hit I made sure all my electronics was in the oven; with care it all fitted, gps, vhf, ssb, echosounder, handheld VHF and computer.

Interesting.
As an oven-less boat to-be builder, I'm contemplating lining the boatronics cabinet with metallic shielding to provide some degree of protection.


These days I always install the VHF so that I can easily disconnect the antenna , even if I do nothing else. In a lightning storm I also disconnect the batteries, and stop the engine if it's running

That's already in the to-do list, something as per post #9

seo
02-09-2014, 08:22 PM
In #52 above "Old Frog" mentions that ABYC has downgraded its standards on lightning protection to an advisory. My guess is that this was done on the advice of the lawyers and insurance consultants, not the advice of the EE's and the meteorologists.
The only basis that I have for that is projection from the case of Catalina, one of the few remaining builders of production sailboats. In their boats' owner's manual (which are excellent, by the way), the company includes the full text of the NFPA standards, but points out that none of these have been incorporated into your new 2008 Catalina, but in case you want lightning protection, here's what's recommended. I've been told that if you install a system, even if it's fully compliant with NFPA 302, and IF the boat is struck by lightning, that a swarm of lawyers will file suit claiming that the plaintiff relied on you to protect him and his adorable family from lightning, and the fact that the boat was hit is proof that you were negligent.
This illustrates the great gulf that yawns between common sense and the law. Anyone who's ever watched the weather understands that weather is funny stuff-any prediction is at best a very well educated guess. Of all the things that fit under the general heading of "weather" there is nothing less predictable than lightning. The scientists construct their best models, and the engineer design their best systems, which the mechanics to their best to install correctly, and STILL the damn lightning strikes.

Old Frog
02-09-2014, 09:27 PM
At the risk of politics... There ought to be a law against lightening strikes.

Seriously, though, one needs to do their due diligence &, to my knowledge, there is no agreement yet. Years ago, I had a couple of buddies whose boats were moored next to each other. One was a Hunter 37. The other a custom 38' that the owner (a very knowledgeable tech - among the 1st group of ABYC master techs - built. & If I ever go around Cape Horn, that is the boat I want to be on) were hit by the same lightening strike. The Hunter had nothing for protection. The VHF & antenna were lost. The custom built boat with the ABYC compliant system, lost all electronics, some lightening & other ancillary components. Obviously that boat sustained the greater of the strike!. Why???

But, when authoritative sources state that a strike can contain 1,000 Giga watts (think Back to the Future), a thunderstorm cloud can contain 100 million V potential, and the average strike is 30K Amps, (source: http://www.aharfield.co.uk/lightning-protection-services/about-lightning), I really doubt that much can be done. The goal is to maximize safety for those onboard.

Thanks for the comments on the oven, that was new to me. A new storage place for my electronics.

Pete E
02-09-2014, 09:50 PM
Lightning and what to do about except build a Faraday cage is a mystery. This I do know.

A fellow who is a neutron walks in a bar, goes up to the bar tender who is a proton and orders a beer. Neutron asks how much ? Proton replies for you no charge. Neutron says are you sure ? Proton says I am positive.

Thats our lesson for the day.....

Richard of Woods Designs
02-09-2014, 11:00 PM
I met Mike O'Brien at the Wooden Boat offices in 2003. We had a long talk about many things, including lightning protection. He told me he had sat inside a Faraday cage while it was being zapped by man-made lightning. So it does work

The problem always seems to be earthing a boat. Lightning rods work well on buildings, consider that some of the most sensitive electronics are put in space craft. They are launched from one of the worlds lightning hotspots. One the face of it, a crazy place to have a rocket base

Richard Woods

seo
02-10-2014, 09:01 AM
I wonder if an effective farraday cage couldn't be built out of copper insect screen. It would be light and cheap, and could be bigger than an oven. Bigger than a breadbox!! I do think that in this conversation there's been a little to much concern over having the ground plate below the waterline.
Consider, for a moment, the old truism that being in a car is a good place to be in a thunderstorm. The reason for that is not that the tires are good insulators: It's a Farraday Cage, and that's why it works, and also why it's important that the windows be closed. Glass is a very good insulator. This also applies to houses. As silly as it seems, closing the windows keeps the lightning out.
With a car, if it gets struck, the lightning can easily arc to ground from the bottom of the Farraday Cage. It's only a few inches, and lightning has come for miles to get there, so a few inches is no big thing. Same thing with a boat. The ground plate doesn't need to be the deepest part of the boat. It needs to be the shortest path to ground

Michael D. Storey
02-10-2014, 10:27 AM
I wonder if an effective farraday cage couldn't be built out of copper insect screen. It would be light and cheap, and could be bigger than an oven. Bigger than a breadbox!! I do think that in this conversation there's been a little to much concern over having the ground plate below the waterline.
Consider, for a moment, the old truism that being in a car is a good place to be in a thunderstorm. The reason for that is not that the tires are good insulators: It's a Farraday Cage, and that's why it works, and also why it's important that the windows be closed. Glass is a very good insulator. This also applies to houses. As silly as it seems, closing the windows keeps the lightning out.
With a car, if it gets struck, the lightning can easily arc to ground from the bottom of the Farraday Cage. It's only a few inches, and lightning has come for miles to get there, so a few inches is no big thing. Same thing with a boat. The ground plate doesn't need to be the deepest part of the boat. It needs to be the shortest path to ground

This car and the lightning thing: If lightning can travel through air for hundreds, thousands of feet, what does a rolled up window do except keep the fireball that you sometimes see from entering the car? You are right, 5" of carbon and air (tires) will be meaningless and useless.
I have relied on bare copper cable, wound around shrouds and dangled overboard. The base of the mast idea seems to put too much energy near flammable materials, whether is is wood, carbon, fiberglass or oil in the bilge.

Breakaway
02-10-2014, 10:42 AM
It might also be worth considering, since we are examining all aspects, that lightning also occurs from earth and to the cloud:.https://www.nssl.noaa.gov/education/svrwx101/lightning/faq/

Does lightning strike from the sky down, or the ground up?The answer is both. Cloud-to-ground lightning comes from the sky down, but the part you see comes from the ground up. A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge. Since opposites attract, an upward streamer is sent out from the object about to be struck. When these two paths meet, a return stroke zips back up to the sky. It is the return stroke that produces the visible flash, but it all happens so fast - in about one-millionth of a second - so the human eye doesn't see the actual formation of the stroke.

Relevant to where this discussion is now, the arcing may need to occur first, rather than last, the most accurate answer, as in so many boating topics, being "it depends."

Kevin

aiprt
02-10-2014, 11:12 AM
Kevin,

Yes, ionized paths may originate from the ground as well as from the sky. Also once the ionized channel is created, there can be several bolts of lightning along the same path in a few milliseconds.
But not reallly relevant to our discussion : a Faraday cage (or ground path) works equally for both directions.
It is all about creating a conductive enclosure around the people or objects to be protected.
I'm with Michael on the closing windows issue, but I must confess I'd *feel* more secure in my car with the windows closed when in a storm...

Back to the oven subject. As I'm not intending to install an oven in my Golant Gaffer project, nor moving about expensive electronic appliances, so the Faraday Cage cabinet with metal shielding seems worth a little reflection...
Seo's idea of copper screen seems appealing, especially to create a removable screen for the front face of the shielded avionics cabinet... Just musing.

Breakaway
02-10-2014, 12:02 PM
Yes, ionized paths may originate from the ground as well as from the sky. Also once the ionized channel is created, there can be several bolts of lightning along the same path in a few milliseconds.
But not reallly relevant to our discussion : a Faraday cage (or ground path) works equally for both directions.
It is all about creating a conductive enclosure around the people or objects to be protected.

I understand it works in both directions. Let me restate as a question and with more clarity ( Hopefully!)

Its said the the "leaders" from the clouds join with the "streamers" from the earth. When leader and streamer meet, the circuit is closed and lightning strikes.

The streamers typically originate at the corner of a building, a steeple, an air terminal ( lightning rod)...that is, they originate at a high, somewhat focused point physically connected to earth.

Finally, my question: Can earth-originating streamers occur with equal ease if they have to jump/ arc from earth at the point of origination? ( as opposed to originating at a point physically connected to earth)


Kevin

seo
02-10-2014, 12:39 PM
The "closed window" factoid came from an interview I did back in the 1970's, talking to a guy who did lightning research at the U. of Minn. His research was about aircraft, and his conclusions were 1) an airplane is a really effective farraday cage, and 2) Lightning is like a fluid, which flows over the surface of the enclosure. An aperture (open window) allows the lightning to "look" in through the window, maybe seeing a tempting path to ground like copper plumbing, for example. Or copper wiring. Good reason to not take baths during lightning storms.

aiprt
02-10-2014, 12:53 PM
Finally, my question: Can earth-originating streamers occur with equal ease if they have to jump/ arc from earth at the point of origination? ( as opposed to originating at a point physically connected to earth)


I'm not a specialist, but trying to remember my physics courses, I'd say that for a given potential difference (PD), "streamers" - or "precursors" as they call them at university - originate more easily from a pointed object than from a flat or rounded object.
Now it all depends on what potential difference has been built up between the said object and the cloud, sky, etc.
So if there is a low PD between an earthed lightning rod and "sky", and a high PD for a nearby flat, insulated etc. object, the probability of a strike is higher for the latter.
Bottom line, hard to predict, and as you said, it all depends...

Richard of Woods Designs
02-10-2014, 01:03 PM
Yes, a lightning rod should have a rounded top. I heard that lightning does go through open car windows. But I tend to keep them closed as it keeps the rain out. Rubber tyres aren't that good an insulator when its a wet road with spray flying (and anyway they contain a lot of steel)

Richard Woods

Breakaway
02-10-2014, 02:05 PM
Thanks, Aiprt.

Kevin

seo
02-11-2014, 03:45 PM
RE: disconnecting electronics to avoid lightning damage. I think the first place to start with that is when you leave the boat unattended. Most boats spend most of their lives either hauled out on land or tied up to a dock or mooring. I inspect a lot of boats in dry storage, outside, with the rigs up, and in very few cases are the electronics disconnected, or taken off the boat.
It's somewhat like having a bilge flooding alarm that makes a little blinker and beeper on the instrument panel operate. That's fine when there's someone on the boat, but... Since 1987 I've inspected vessels that have flooded and/or sank at least 25 times. I can't think of a single case happening when the vessel was underway with the crew on board.
Point being, I want a bilge flooding alarm that flashes a bright light that can be seen a couple hundred yards away, and a horn that will attract attention from the same distance. I wire them through a automotive blinker light "flasher" relay, so that it's even more conspicuous.

slug
02-11-2014, 03:57 PM
RE: disconnecting electronics to avoid lightning damage. I think the first place to start with that is when you leave the boat unattended. Most boats spend most of their lives either hauled out on land or tied up to a dock or mooring. I inspect a lot of boats in dry storage, outside, with the rigs up, and in very few cases are the electronics disconnected, or taken off the boat.
It's somewhat like having a bilge flooding alarm that makes a little blinker and beeper on the instrument panel operate. That's fine when there's someone on the boat, but... Since 1987 I've inspected vessels that have flooded and/or sank at least 25 times. I can't think of a single case happening when the vessel was underway with the crew on board.
Point being, I want a bilge flooding alarm that flashes a bright light that can be seen a couple hundred yards away, and a horn that will attract attention from the same distance. I wire them through a automotive blinker light "flasher" relay, so that it's even more conspicuous.

not easy to disconnect electronics. Are you suggesting disconnecting the antenna and the equipments earth ?

ive been struck by lightning several times. Damage ....Vhf ant and cable...masthead vane, masthead strobe, and the insulated backstay at the insulator. No instrumentation was harmed.


Additional damage was the electronic main engine controls and the main alarm system for high water, fire, and boat functions.

Old Frog
02-11-2014, 05:54 PM
RE: disconnecting electronics to avoid lightning damage. I think the first place to start with that is when you leave the boat unattended. Most boats spend most of their lives either hauled out on land or tied up to a dock or mooring. I inspect a lot of boats in dry storage, outside, with the rigs up, and in very few cases are the electronics disconnected, or taken off the boat.
It's somewhat like having a bilge flooding alarm that makes a little blinker and beeper on the instrument panel operate. That's fine when there's someone on the boat, but... Since 1987 I've inspected vessels that have flooded and/or sank at least 25 times. I can't think of a single case happening when the vessel was underway with the crew on board.
Point being, I want a bilge flooding alarm that flashes a bright light that can be seen a couple hundred yards away, and a horn that will attract attention from the same distance. I wire them through a automotive blinker light "flasher" relay, so that it's even more conspicuous.

In keeping with what SEO writes, it is my experience and observation that, for boats kept in the water, many/most owners do not close sea cocks, turn off un-needed electrical circuits, or even take what I consider to be the basic prudent and appropriate precautions. That does not even take into consideration, the typical absence of mooring gear chafe protection, etc. It is frightening the number of boats that leave air conditioning systems, unattended space heaters, etc. running.

I have not put a pencil to it, but I suspect, of the lightening boats I have been involved with, a high number were not direct strikes. Rather, they were nearby strikes (I think lightening is considered a type of EMP event) or sustained damaged as a result of surge via the boat's umbilical shore power connection to the shore based grid. It is always interesting to see several boats on the same dock within a marina with "lightening damage", no indicators of a direct strike to any of them. Often times, there is a boat somewhere in the mix that did not sustain any damage. In asking background questions, the answer often is: That boat was not connected to shore power.

Several times, I have been involved after the fact with boats that sustained "lightening damage" with similar circumstances. A nearby tree above or near the slip sustained a direct hit. Bark and tree limbs were scattered about the area. Ground disturbance paths were visible leading from the tree to buried conduit (in one instance an extension cord on the ground). The boats plugged in had electronic & electrical system damage. But, boats on the same dock no plugged in were fine. The nearby house or building typically had similar damage (consumer electronics and some electrical circuits). Similarly, I have seen a pole or transformer hit with simialr results to the boats connected to the grid.

Again, thanks for the oven idea. One more thing to do as I put the boat to bed. Close the sea cocks, turn odd circuits except bilge pump & high water alarm, (don't connect to shore power), & put the expensive electronics in the oven (or metal container). With my luck, my wife will one day want to surprise me, pre-heat the oven with out looking.....

Note to self: Research metal or foil liner lockers. I wonder if aluminized mylar lining a storage locker would suffice?

aiprt
02-11-2014, 06:30 PM
Note to self: Research metal or foil liner lockers.

Made the same note^^!


I wonder if aluminized mylar lining a storage locker would suffice?

Just wondering...how about a kitchen experiment with a cell phone and a survival blanket, aluminium foil, microwave oven (all metal), etc.?
Have to note that down in the 'Golant Gaffer notebook'...

So many preliminary questions before making building decisions...
During another type of build in another life, I ended up with building a wind tunnel, doing electrical experiments on batteries and voltage regulators in a college lab, building a hotwire robot, wew !

seo
02-11-2014, 07:16 PM
Well, here's a very brief essay on the virtue of lightning:
When my son was young he was kind of a misfit. I particularly remember a session with his 5th grade teacher, principal, and the school's "Gifted and Talented" program person. I was trying to persuade them that they had the same obligation to provide Kiddo with the same special "appropriate curriculum" programs that they gave kids on the other side of the spectrum. As an introduction, I gave them copies of a math test that I'd given kiddo that morning. They looked it over, and finally the G&T person said "Why'd you mark #8 wrong?"
"Because a positive multiplied by a negative results in a negative," I answered.
"Oh," she said. "Yeah. Right."
Well, anyway, fast forward from there to the class field trip to the Boston Science Museum, where we went to see the lightning show:
http://www.mos.org/live-presentations/lightning
the World's largest Van de Graff generator. Amazing, even to my jaded eye, addled by the passing years. To him, it was magic. From there, almost in a direct line, off he went to McGill University, to graduate in 3.5 years with a degree in Comp Sci and physics.
A couple of years ago I quit asking him what he was studying...
In a lot of ways, he's still studying lightning.