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Old 15-07-2019, 04:57   #106
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Re: Lightning Protection, pros and cons

I guess this is why most of us are worried


Notice the residue still on the dock

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Old 15-07-2019, 05:47   #107
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Re: Lightning Protection, pros and cons

We seem to do lightning about once every six months.

"Attract" is a risky term. Masts are good charge concentrators, but nothing sucks in lightning.

At 150K amps and a billion or so volts, where it goes when it becomes a current is a crap shoot. One boat boils some water under the hull, and another loses all his electronics. It's the one time I'm really happy to be in a steel boat. Let's hear it for faraday cages.
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Old 15-07-2019, 06:03   #108
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Re: Lightning Protection, pros and cons

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Originally Posted by Sojourner View Post
........ what would it be like to have a properly rounded copper lightning rod assembly of some sort (2 ft rod with weight at bottom) with 20m of #2 or #4 gauge copper wire terminating in a copper pipe piece. Attach to spinnaker halyard at anchor, hoist it to masthead where the rod is above everything and drop the pipe-end in the water over the side?

This would create effectively a straight (if angled slightly) path right to the water.
Storage wouldn't be horrible coiled. Makes more sense if anchoring always in Florida or the like, but on paper, would this be a good solution?

Of course now I'm thinking of hard-wiring the top piece and cable down along a shroud, and having a clip on at the bottom for the last 2 meters, so it could be used sailing as well.... wouldn't add much weight or windage, and we're not a performance boat...thoughts?
On paper and lightning mitigation wise it sounds reasonable and certainly better than doing nothing IMO. Clearly #2 would be better than #4.

I can't comment on weight aspects in the "permanent" mode.

The angle isn't an issue, only bends at a problem and if you must have a bend, it should have a large (really large) radius.
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Old 15-07-2019, 07:00   #109
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Re: Lightning Protection, pros and cons

I found this device .. Going to get one .. At least I can turn off breakers of some equipment if a storm/lightning is approaching. Doesn't stop me from getting hit .. but allows me to save some equipment if I do get struck. I know of some people that put one phone, handheld vhf and smart tablet inside the microwave for protection when lightning is approaching in case they are struck (Great Shield). At least they have some communication if lightning damages everything else.

https://www.pmt-fl.com/lightning-det...talos-sfd-1000
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Old 15-07-2019, 07:06   #110
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Re: Lightning Protection, pros and cons

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Originally Posted by Sojourner View Post
After possibly being struck or at least very nearby by lightning a couple weeks ago, I read up a fair bit on the subject of lightning protection/mitigation. Some use it, some thinks it attracts more. Some throw jumper cables off the shrouds into the water to prevent leaders from forming...... Is there any consensus at all regarding strategies to prevent strikes?
I had electronics damaged when a boat 3 berths away was struck.
The reason I was hit as a third party was via my speed wheel, I was only doing an overnight to shelter from the storm so did not remove it but the static change entered my onboard systems and blow some of my instruments so my advise is always remove you speed wheel in a storm in a marina
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Old 15-07-2019, 07:26   #111
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Re: Lightning Protection, pros and cons - my take

Very high voltage generally travels on the outside of the conductor.

My "solution" is to use 3" ofc copper 0.32 or more thick. Run it from a copper "lighting" rod at the top of the mast as straight as possible to the water. I also clip on HEAVY duty jumper cables to the CAP shroud. Praying seems to help a lot. Any attachments to ground should be at ONE location only.

35 years ago we were in middle bay Chesapeake in a 43' sloop. The lightning strikes were about one a second within a mile of us for about 10 minutes.

We survived with NO damage but boats all around us had moderate to major damage. (SS winch turning Blue - All electronics crap etc). Yes I also clipped a Truck jumper cable to my cap shroud.
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Old 15-07-2019, 09:45   #112
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Re: Lightning Protection, pros and cons - my take

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Very high voltage generally travels on the outside of the conductor.

My "solution" is to use 3" ofc copper 0.32 or more thick. Run it from a copper "lighting" rod at the top of the mast as straight as possible to the water. I also clip on HEAVY duty jumper cables to the CAP shroud. Praying seems to help a lot. Any attachments to ground should be at ONE location only.

35 years ago we were in middle bay Chesapeake in a 43' sloop. The lightning strikes were about one a second within a mile of us for about 10 minutes.

We survived with NO damage but boats all around us had moderate to major damage. (SS winch turning Blue - All electronics crap etc). Yes I also clipped a Truck jumper cable to my cap shroud.
When routing often very large amounts of RF energy in broadcasting, we use flat conductors. A flat conductor has less inductance than a round conductor and has more outer surface area for the same amount of material. I've used stainless steel braid from American Grounding Systems: http://www.ags.bz/. I was able to buy stainless flat braid in bulk in 50 foot lengths.

Copper wire corrodes quickly and eventually dissolves in the presence of sea water. Stainless can be run right through your bilge and immersed in seawater without rapid corrosion. Use stainless clamps and fasteners for interconnections.

Stainless has lower conductivity than copper so you'll have to use a heavier gauge than the same copper conductor. ABS above can give you conductivity equivalence of stainless to copper.

I also trail a 30-foot 1-inch wide length of stainless braid astern, attached to my backstay chainplate which is part of my RF ground, when using my HF radio, and the rare times we have thunderstorms here. It trails along right where I want it: an inch or two beneath the surface. As long as I'm underway, it doesn't get anywhere near the prop. It improves my antenna efficiency by 3 to 6 dB on 20 and 40 meters. I spool it up when not in use.
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Old 15-07-2019, 10:18   #113
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Re: Lightning Protection, pros and cons

I have a bowsprit on my boat and the bobstay chainplate is almost always underwater in front on the bow, it has a galvanized chain running up to the bowsprit cranse iron which is the collar where the forestay and side stay whiskers lead off.

I have been struck by lightning several times, being the highest object for sometimes hundreds of miles around, and I have never come to any harm, as the lighting bolt travels from the mast top (stainless steel plate carrying all the stays) travels down to the forestay and into the water via the bobstay chain aforementioned.. I will mention that my mast plat on top glowed green for a long time after I was struck (at night) I was told this was a form of St Elmo's fire...

As a rule I alway disconnected my radios antennas when in the vicinity of electric storms... I crossed the ITCZ many times and there are always plenty of isolated storms around there. It may be a suggestion that a boat's rigging should be grounded permanently.... maybe through the keel or somewhere... not sure if it's a good idea using the prop shaft ...
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Old 15-07-2019, 10:41   #114
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Re: Lightning Protection, pros and cons

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The aluminium mast is a sufficient conductor from the top to the base but the lightning wants to get to the surface of the seawater; this is the essence of a cloud to ground (sea water) discharge.

So you have to complete the circuit from the bottom of the mast to the sea water with a big fat straight conductor to a substantial area of metal in the water.

If you don't provide such a conductor, the lightning will find whatever way it wants to and does't care about how it does it!

If you have a steel or aluminium hull you are sweet!
I guess the video of the yacht hit by lightening that is going the rounds makes this topic active again

In discussing what happens to the energy going down the mast, does it not make a difference if the mast is deck stepped or keel stepped. My aluminium mast goes through the saloon and is screwed onto the lead keel. So do I not have a route for the energy to go through and into the sea?
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Old 15-07-2019, 10:44   #115
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Re: Lightning Protection, pros and cons

War Story here. When I was about 10yrs old on family vacation on Chatuqua Lake NY, I was watching a thunderstorm come across the lake. I saw a ball of white light streak out of a cloud to the top of a mast (brand new Star class, I think), run down the mast, jump to a brand new aluminum dock, run up the dock into the ground and a huge booming that broke some windows. All happened in a blink. Scared the crap out of me.



Afterward, the dock was crystallized to the point you could push your finger through it and the mast crumbled.



Years later I learned that it was probably globe lightening.



I'm glad I live in San Diego, we don't have weather here.
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Old 15-07-2019, 11:08   #116
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Re: Lightning Protection, pros and cons

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Originally Posted by noelex 77 View Post
...lightening likes to travel in straight lines...
The video of the Columbia Yacht Club in Boston strike shows that the lightning is fine with making right angle turns.

We have a lot of "common knowledge" about lightning which is unverified, basically hearsay.

That being said, I do ascribe to the idea that providing a direct and large gauge path from the rig (shrouds included) to a metal face in the water might avoid a lightning strike from finding its own path (through the hull or through-hull fittings).

I'd be interested in any actual scientific study or justification, not just opinion, that masthead lightning protection has any benefit at all for protection against the lightning induced EMF pulses which wipe out so many electronic items not even connected.
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Old 15-07-2019, 11:31   #117
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Re: Lightning Protection, pros and cons

[QUOTE=sailorladd;2931331I will mention that my mast plat on top glowed green for a long time after I was struck (at night) I was told this was a form of St Elmo's fire...

... not sure if it's a good idea using the prop shaft ...[/QUOTE]

St. Elmo's Fire is known in engineering as a "corona discharge." It's not a myth, and you weren't imagining it. https://en.wikipedia.org/wiki/Corona_discharge.

I'm not sure either about the prop-as-ground. The lightning current will flow through the engine's main bearings.
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Old 15-07-2019, 13:42   #118
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Re: Lightning Protection, pros and cons

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Ok, so since I started this thread, I reserve the right to reiterate my stupid question: Should I feel reasonably protected that in a strike on my aluminum mast, in my 100% correctly bonded and grounded boat with an SSB plate on the rudder (and a grounded keel cooler plate as well...would that have the same effect?) the charge (as much as can ever be predicted) would likely exit those instead of blowing a hole in the hull? And followup, quick easy jumper leads or maybe even heavier gauge just for the purpose attached to shrouds (or possibly twin attatchments, shrouds and mast bottom? or just mast foot?) led to copper pipe dragged beside the boat to use as necessary would be good?

Sojourner, yes, it's interesting how these discussions go astray at times. To try & answer your question directly, I would say yes based on direct experience (for which there seems to be little of in this thread). and by that I mean, the direct experience of actually having your vessel struck by lighting while onboard the vessel and subsequently relaying the experience & actual damage. My wife & I were on passage between NZ & Tonga when we suffered a lightening strike. All underwater fittings were well bonded & grounded. The mast was keel stepped in the sense that it passed through the deck and was stepped atop a glassed over plywood structure that was on top of an encapsulated keel & was bonded into the entire system. I was dragging quite thick welding cables through the water that were attached to both cap shrouds at the time. The storm was so horiffic that I could not say which clap of thunder was from the the actual hit as there were so many flashes of intense light followed by such thunderous noise that vibrated through the hull that it was impossible to tell which bolt or perhaps multiple strikes actually hit us. We were hove to at the time & the lightening lasted for perhaps 45 minutes to an hour. The next morning I noticed my B&G wind speed & direction instruments were not functioning. The windex at the masthead was gone as well. When we finally made anchorage in Tonga, going aloft revealed the printed circut boards for the B&G sending unit at the masthead was green goo, the tricolor was blown to bits and the windex was completely gone. The masthead VHF antenna (which was the tallest item) was fine. No other electronic damage was suffered, ie all radios & navigation insturments worked fine. I could hardly believe the VHF was undamaged (or anything else for that matter). I think the worst damage was to our nerves. After eventually replacing the masthead sending unit, the wind insturments worked fine at both helm & nav station. While I can't prove it, I attribute our minimal damage to the deployment of cables from the shrouds with a decent bonded & grounded vessel, along with a multitude of prayers that were sent during that event. Hope this helps answer your question to some degree.
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Old 15-07-2019, 15:06   #119
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Re: Lightning Protection, pros and cons

The lightning rod attached to your mast does NOT have to be copper. Instead of half inch copper, make it 3/4 inch Aluminium and avoid the dissimilar metals corrosion you might otherwise get.

Copper is a better conductor, but a thicker Aluminium rod has the same or close enough resistance.
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Old 15-07-2019, 17:11   #120
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Re: Lightning Protection, pros and cons

Guess I’m a lucky guy. Lived aboard in S Florida for 17 yrs, and cruised the Caribbean, South America, Central America and Mexico both Atlantic and Pacific sides for another 10 yrs. Have been through countless T-storms. Hundred? Maybe a thousand? Didn’t count. Sometimes several a day. And never struck. Some of my boats were grounded, some weren’t. Some were Jerry rigged grounded. Many times had strikes with no discernible time between sound and flash; like a shotgun bang. All monohulls from 26 to 48 feet. Lucky or blessed depending on your thinking. I’ll say “thank you God”. But yeah, scary every time. Never fun to go right through an electrical storm. It’s a chance game.
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