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Old 10-11-2020, 11:07   #1
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Lightning Protection for Electronics

I am currently looking at protecting my new FP Saba 50 Catamaran from lightning as much as I practically can. I have Ewen Thompson PhD (Marine Lightning Protection Inc.), an expert on Marine Lightning, designing a protective rib cage around the sensitive interior of the boat. We want to augment this with some Surge Protective Devices (SPDs) to further protect the sensitive electronics on board from the effects of a lightning strike.

My reasons for undertaking this project is:
ē Lightning can kill you and sink the boat, two things that would ruin my day.
ē I can count up 10 friends that have been hit by lightning and have incurred significant delays (some lost a whole year of cruising), whilst they put their boat back together.
ē Iíve had several close calls in the Med, Atlantic Portugal and the Caribbean. It a truly frightening experience to be surrounded by lightning. I particularly donít like scaring the Admiral.
ē Insurance companies are increasingly looking to up their lightning excesses, as the world experiences increased lightning (the journal Science reported that we could expect to see a 12% increase in lightning activity for every 1 degree of warming). Pantaenius have already indicated that their lightning excess is 30%, unless an endorsed lightning protection system is installed. I can see other insurance companies following suit.

To complete our design, we need to find some well-designed marine 12V Surge Protection Devices that are rated for lightning. Iím interested to see what other owners have actually installed on their yachts and their experience with fitting these SPDs.
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Old 10-11-2020, 11:34   #2
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Lightning Protection for Electronics

Still a crap shoot in my experience. Iíve know of boats with all the bells and whistles in lightning protection have their systems fried (the boat ultimately sank) and Iíve known boats that did nothing who have no damage except a fried vhf antenna.
Other than ensuring your properly grounded and a path of least resistance is created before your sensitive electronics I think the only thing you can really do is ensure you donít rely entirely on your electronics to get to a safe harbor.

It sounds like one more stipulation insurance companies are trying to use to get from paying out claims.
I think if Thor decides heís going to damage your boat thereís not much to be done about it.
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Old 10-11-2020, 12:01   #3
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Re: Lightning Protection for Electronics

If I had money to throw at a lightning EE I would first contract someone who works lightning for Airbus/Boeing/big-time aerospace and would have a marine EE look at the plan afterwards.

The airplane guys actually deal with routine hits (with more on the line) while the marine guys have a lot of snake oil in their midst and/or their systems are in total less tested with who knows what outcomes.
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Old 10-11-2020, 12:36   #4
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Re: Lightning Protection for Electronics

Ewen Thompson is no snake oil guy. He was a Professor of EE at University of Florida and is pretty well credentialed. I'm interested in hearing from boaters who have actually installed SPDs - not really interested in hearing from armchair critics.
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Old 10-11-2020, 14:21   #5
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Re: Lightning Protection for Electronics

I think you mean Ewen Thomson.

Some members of the forum have had strikes, and can tell you about them, but Professor Thomson collected those experiences when he first began work on the question. If you don't want that, you may not get much else.

Professor Thomson cites DC surge protection devices in his Tier 3 design for catamarans. What he (you) may not have is even casual data on boats that have his grounding system and DC surge protectors and have been hit by lightning. Outcomes, in other words. That's going to be a pretty small data pool.
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Old 10-11-2020, 14:40   #6
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Lightning Protection for Electronics

Iím personally not saying he is selling snake oil just that itís not a guarantee. Maybe one day the engineering will get there. Lightning is very powerful as well as unpredictable so itís challenging. Now those fuzzy little lightning diffusers I would call snake oil...

Iím in S Florida so I deal with more lightning strikes than most and have looked extensively at various products. It was a little expensive to purchase SPDs for each and every electronic device you have (both positive and negative sides mind you).
The costs where very high for a lot of uncertainty. Iíve read research from Ewen and others and I can tell you from what Iíve read and seen in the world that it appears to be up to the gods.
Thereís no guarantee the current will follow the path you want itís really all just try and hope.

Here is an article from the University of Florida (my old stomping grounds!) by Ewen himself in which he says there is no real guarantee and advocates simply disconnecting anything valuable.

https://ufdc.ufl.edu/UF00073916/00001

So the boat I knew that sunk reportedly had lightning protection that included voltage surge clamps and was grounded to a special plate (he was a radio operator also) Well the current found its way to a through hull, not the grounding plate (or maybe both) and blew it out. Faulty lightning protection design? Who knows but I do know of boats whoíve been hit and nothing really happened so there seems to be some unforeseen variable(s) here.

With such drastic differences in outcomes between a lightning strike on one boat and another similar one itís very hard to actually provide conclusive evidence that your lightning protection system actually did the protecting. Which is why itís hard to provide recommendations and which is why I think some insurance companies follow X advice and others follow Y. If there was conclusive evidence there would be unanimous adoption.



Planes act like giant faraday cages if I remember correctly.
Iíve always thought this was a good argument for steel hull boats.
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Old 10-11-2020, 14:42   #7
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Re: Lightning Protection for Electronics

We have a lightning diffuser on top of the mast, lightning struck it a few years ago.
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Old 10-11-2020, 15:12   #8
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Re: Lightning Protection for Electronics

This unlucky YouTuber should have had his protection on


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Old 10-11-2020, 15:37   #9
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Re: Lightning Protection for Electronics

Having had 2 direct hits I would say whatever you do hope your insurance covers it!
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Old 10-11-2020, 15:50   #10
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Re: Lightning Protection for Electronics

Oops - yes Ewen Thomson.

Agree that nothing is certain when it comes to lightning but if i can get rid of the insurance excess then Ewen's solution pays for itself over time.
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Old 10-11-2020, 15:54   #11
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Re: Lightning Protection for Electronics

I agree that nothing is certain when it comes to lightning. My cruising friends that have been hit by lightning have had a variety of outcomes. In my mind its all about risk mitigation. Like a lot of risks in this world, you can't reduce them down to zero. Insurance is always going to be my back stop. Thats why I'm keen to pursue something that will remove any lightning excess. Pantaenius looks the best deal for me but they have a 30% insurance excess.
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Old 10-11-2020, 16:56   #12
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Re: Lightning Protection for Electronics

I think with a properly designed and MAINTED lightning dissipation system you can prevent catastrophic damage to the vessel (fiberglass, aluminum, SS) under most strike conditions. Surge protection devices spread around the electrical/ electronic systems can provide a measure of protection from nearby strikes, but a high amperage direct strike to the mast/VHF antenna is likely to take a serious toll on everything electrical/ electronic.

Because of the history and misunderstanding around lightning there is a lot of "snake oil" around. IMO Dr Thomson does not fall in the latter catagory.


The snakes used to show up in my office most every week after desktop computers showed up.


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Old 10-11-2020, 19:53   #13
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Re: Lightning Protection for Electronics

This is something I've wondered about as I'm starting to explore the idea of sailing/cruising..all the expensive electronics in these boats with huge metal masts....

As a teen back in the 1980's I was on my dad's boat just offshore when it was struck. It was a small flying bridge power boat. Lightning hit the CB radio antenna. The interesting thing to me was that every single electrical item that was switched on turned into a pile of goo.... every light bulb, every windshield wiper motor, the electronic ignition in the engine, the CB radio of course....
but everything that was switched off ended up not being touched, the other windshield wiper motor, every light, etc... all fine. I've never understood how those little switches would stop it....

Years later I attended an aviation safety seminar..a talk by Bruce Fisher. With NASA he was part of a study of lightning strikes in aircraft. Tons of very interesting photos and data. My big takeaway was how lightning gets into wires or structure and just tries to flow through to get out. One photo showed a leading edge of a wing of a small plane...cessna I think. It had entered one wing tip, traveled down the small gauge navigation light wiring to the opposite wingtip where it exited. The magnetic force from the current in the wire imploded the curved out leading edge into a cupped cross section. The plane had landed like that....
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Old 10-11-2020, 20:01   #14
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Re: Lightning Protection for Electronics

There is no "automatic protection" for dumb sailors possible which would work by itself and would "avoid lightning" or "protect" the boat. At least, not for modern boats with loads of electronics.
Nothing in the World is able to stop MILLIONS of volts which lightning strike consists.

There are few factors which must be taken in consideration.
1. Each cabin on the boat must be designed and built by boat builder as real Faraday cage. Therefore boat must be aluminum/steel, it's impossible to create real Faraday cages on fiberglass boat. I'm also positively sure that idea of "whole boat as one big Faraday cage" will not work.
2. Each cabin (Faraday cage) must have quick disconnect for ALL wires coming into this cabin. By "quick" I mean matter of seconds, not minutes. All connection points must have ability to be closed with special fitted metal plates so there will be CONTINUOUS Faraday cage.
3. Nav station also must have metal housing, removable metal cover and also must have ability to be disconnected COMPLETELY in a matter of seconds to become fully sealed Faraday cage.
4. Same for engine rooms.
5. Same quick disconnect must be for ALL wires going to the mast, except one very thick cable which should be routed to the water, to properly engineered dissipating system, to help dissipate energy of lightning strike.

So preparation for storm will consist disconnection of ALL connectors, totally depower the boat and turn all cabins into SEPARATE Faraday cages. All equipment on the mast will be destroyed in case of lightning strike, but most of other equipment (that's 100's of thousands $ on modern boats) should survive.

Will this disconnection work be a hassle? Yes, at some degree. Would you do it? What if it will save you $100K one day?

It's very well known fact that cell phones and laptops (very sensitive devices) easily survive lightning strikes if they been inside microwave. Microwave is Faraday cage.
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Old 10-11-2020, 23:58   #15
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Re: Lightning Protection for Electronics

Stull,

Nice to hear of another user of Dr. Thomson's system on the forum! I had fairly extensive communications with him before we purchased the system, and have incorporated our ideas into the build. I have not installed the Seidarcs yet, and will not do that until the boat is launched and I'm confident of exactly where the waterline will be.

Here are my thoughts so far:

1. The down conductor from the mast is crucially important. It should go straight down to the water surface. I'm using 95mm2 cable connected from the mast base exterior, runs beside our Stainless compression post (but inside an electrically insulating cover) to a 20mm diameter copper rod electrode that can be dropped down through a conduit to the water surface under the bridgedeck when at anchor. It's pulled up out of the way when sailing so it's not damaged from floating debris, or wave pressure.

2. All electrical wires and aerial cables have quick disconnect fitting at the top of our mast compression post in the saloon. All wires to electronic instruments & displays have quick disconnect fittings at the navigation station. Same with all wires to instruments at helm. The disconnect fittings are multipin, so several items can be disconnected just by pulling the fitting apart, like a trailer to car connector. I have three to pull apart as fast as I can when lightning threatens. I just wasn't confident enough in surge protectors.

I think that this system will be good for most strikes, but there are lightning super-bolts that are so huge that they would over power any cleverness we may think we can come up with. But buildings are well protected by the principles of this type of system whereby there are large conductors that run down the corners of the building connecting earth to lightning rods at the corners, and they work.

Stull, it would be good to exchange ideas for this system with another user, so PM me if you'd like.
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