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Old 21-09-2014, 18:21   #31
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Re: Lightning Strikes and Cats

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Originally Posted by Arthur Garfield View Post
Again,I reitterate--- Lightning Attenuation Onboard

This the most thoughtful encompassing practical analysis of lightning attenuation.
I agree. Kasten's site is a very good summary of current best practices, as I understand it, and it is based on Ewen Thomson's work & the technical commitee's that have studied lightning risk and mitigation.

The one thing that I am questioning is the surge protectors and whether they would work with such high voltage and current. Intuitively, it seems to me that physical disconnection of the electronic devices within a (proper) Faraday cage would be as good as it gets. It presumes you can judge when to make the disconnection of course, but most times I think you'd have enough heads up to make the disconnections. The disconnecting plugs would have to be easily accessible and quick to do. At night in locations of high probability of nightime lightning storms when anchored, it would be a good practice to disconnect all electronics before retiring to the cabin for the night so you don't wake up at 4 am in a blinding flash and find all your electronics fried.
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Old 22-09-2014, 01:48   #32
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Re: Lightning Strikes and Cats

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The one thing that I am questioning is the surge protectors and whether they would work with such high voltage and current.
Well, pro telecom industry use them for years, and you dont see network dissapearing from your cellular after every thunderstorm due to cell tower electronics being burnt out. There are very good quality, professional grade lightning arrestors and surge protectors for everything from 220V equipment to low-power stuff. I am really puzzled why people don't use them on boats - probably t is easier to file a claim than to do a proper installation.

In the city where I live, my ISP uses own cables for a city-wide hi-speed internet infrastructure. There are hundreds of miles of wires hanging between houses, and I remember before, like 5 years ago, after every major thunderstorm, I was waiting for them to change burnt out equipment - no internet, bummer. Then, they contracted pro telecomm people to install proper supressors and stuff. Not a single outage after that, no burnt out routers and stuff. For me, that shows the efficiency of the properly implemented lightning protectors.
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Old 22-09-2014, 02:07   #33
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Re: Lightning Strikes and Cats

Thanks Sea Frog, very good points. I must do some investigating what specs will work on a boat.

The main challenge is getting the bulk of the current directly to ground from the mast on a cat, without diverting with cables at right angles. Still haven't worked that one out completely to my satisfaction yet, as the mast position is stepped on top of the coachroof, a bit further back than most cats. The compression post goes through the salon.
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Old 22-09-2014, 06:30   #34
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Re: Lightning Strikes and Cats

The problem with lightning is the range of voltage, hence damage, can be from 10v to 10,000,000v (or higher).

Yes, lightning arrestors help on the lower voltages strikes (or side flashes), but a direct strike with millions of volts of potential will burn anything in it's path. There is no failsafe protection from lightning, it's simply too variable. Statistically, using arrestors and mechanisms to help get the bulk of the current off the boat in a direct path has helped, but it's very hard to measure the level of 'help' with the variability between the power of each lightning strike.

A common belief is to provide a direct and short path from the mast to the water. The goal is to get as much of the current off the boat quickly. It's generally accepted that you'll lose the electronics, but the goal is to save the fiberglass. Lightning will follow the fiberglass if that's the only way to ground, when it does this, it can burn open cracks of 2" or more. Not good when that happens below the waterline.
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Old 22-09-2014, 07:55   #35
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Re: Lightning Strikes and Cats

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I am really puzzled why people don't use them on boats - probably t is easier to file a claim than to do a proper installation.
Two reasons - effective ones cost a lot (and are needed on each AC and D circuit, as well as full panel units) and providing a proper installation for them is difficult on many boats, particularly catamarans.

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Old 22-09-2014, 08:13   #36
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Re: Lightning Strikes and Cats

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Thanks Sea Frog, very good points. I must do some investigating what specs will work on a boat.

The main challenge is getting the bulk of the current directly to ground from the mast on a cat, without diverting with cables at right angles. Still haven't worked that one out completely to my satisfaction yet, as the mast position is stepped on top of the coachroof, a bit further back than most cats. The compression post goes through the salon.
For a long time I considered bolting a length of 4-0 battery cable to the mast base and running it though the bridgedeck. It was to have a length of line tied to the end and led to the cockpit so it could be tied up, out of the water, then lowered from the safety of the cockpit when lightning was about. In the end, though, I was not convinced it would do much good to protect the boat and would do nothing for my electronics so I found other things to worry about.
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Old 22-09-2014, 08:23   #37
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Re: Lightning Strikes and Cats

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probably t is easier to file a claim than to do a proper installation.
Almost certainly true. The work and expense required to properly retrofit a boat with lightning protection, of questionable benefit, is not insignificant.

Again, it 'strikes me' (sorry) that if there were a reliable way to prevent damage to boats from lightning, insurance companies would require it before offering coverage for lightning strikes. This would be particularly true of places like Florida where, I assume, a large percentage of their payouts are due to lightning.
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Old 22-09-2014, 08:32   #38
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Re: Lightning Strikes and Cats

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Again, it 'strikes me' (sorry) that if there were a reliable way to prevent damage to boats from lightning, insurance companies would require it before offering coverage for lightning strikes. This would be particularly true of places like Florida where, I assume, a large percentage of their payouts are due to lightning.
Maybe, they prefer to rise insurance costs? Like, there are no (currently) widely accepted standards on lightnng protection for boats, so it will be very difficult for insurers to enforce them. We may see some moves in that direction in the future, but maybe they would just prefer to go the easier path - pay out. Just like people prefer to file a claim.
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Old 22-09-2014, 08:33   #39
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Re: Lightning Strikes and Cats

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For a long time I considered bolting a length of 4-0 battery cable to the mast base and running it though the bridgedeck. It was to have a length of line tied to the end and led to the cockpit so it could be tied up, out of the water, then lowered from the safety of the cockpit when lightning was about. In the end, though, I was not convinced it would do much good to protect the boat and would do nothing for my electronics so I found other things to worry about.
I'm not a Cat and have considered exactly this, but also have wondered if any kind of home made lightning device might just invalidate your insurance?
On sport fishermen I have seen large gauge cable attached to a big plate on the outside of the hull. I've always wondered if lightning might not just blow out that plate and the hull it's attached to?
I don't care about the electronics, I assume they are gone, my concern is keeping the water out.
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Old 22-09-2014, 08:42   #40
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Re: Lightning Strikes and Cats

I've always entertained the question as whether it is wise to have a grounded object sticking up in the air. I would almost seem it is inviting a lightening strike?

Just the corona around a grounding cable I would think could be dangerous?
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Old 22-09-2014, 09:03   #41
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Re: Lightning Strikes and Cats

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For a long time I considered bolting a length of 4-0 battery cable to the mast base and running it though the bridgedeck.
...
I was not convinced it would do much good to protect the boat and would do nothing for my electronics so I found other things to worry about.
We have a length of 4/0 cable attached to our mast with a substantial mounting plate and terminated with an electrode containing >15' of linear edge surface (the electrode is ~12" long with many edge surfaces machined into it. The cable drops between the hulls through the tramp area and, while it has a gentle bend in it to reach that area (20" radius?), it does not have any sharp bends.

We took a direct strike and there was physical evidence that this cable/electrode took the brunt of the current and led it to ground. There was no hull damage anywhere, but almost all of our electronics and some of the electrics were shot.

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Almost certainly true. The work and expense required to properly retrofit a boat with lightning protection, of questionable benefit, is not insignificant.
Suppressors are not of questionable benefit - all communication centers, computer centers, etc use them to great effectiveness. On a boat, the work and expense is indeed very high and they would help protect electronics, but the cost of the installation may exceed the price of the electronics protected.

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Maybe, they prefer to rise insurance costs?
This conspiracy has been brought up in previous lightning threads. I don't buy it at all, and see no practical way this strategy would work in an insurance company's favor.

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I'm not a Cat and have considered exactly this, but also have wondered if any kind of home made lightning device might just invalidate your insurance?
No insurance company that we have ever gotten policy terms from has ever excluded or even mentioned anything like this. It would be a slippery slope considering how many "home made" stuff is on a boat. For example, would a non-OEM anchor roller failure be cause for a claim denial?

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Old 22-09-2014, 09:07   #42
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Re: Lightning Strikes and Cats

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I've always entertained the question as whether it is wise to have a grounded object sticking up in the air. I would almost seem it is inviting a lightening strike?
That is a common misbelief that has caused many to keep their boats ungrounded. However, there is no statistical evidence to support it, and all standards bodies recommend grounding for lightning safety.

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Old 22-09-2014, 09:25   #43
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Re: Lightning Strikes and Cats

Mark,
I think your non OEM anchor roller example is spot on, I'm of the opinion that if something that you manufactured for your boat fails or is the cause of another failure, and this failure causes a loss, that your insurance company may not pay up.
Myself I have one of those zinc guppies bonded to my mast that is hanging in the water, is that enough? I have no idea.
My only personal experience with lightning was with an aircraft that was chained to the ground by six chains, all to grounded tie down points. Logically the lightning would go straight to ground, but enough of it "leaked" out to burn holes in both pitot tube covers, indicating of course that at least some of it exited there.
Amazingly there was almost no damage to the aircraft, except that any ferrous metal was magnetized, but all the avionics worked.
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Old 22-09-2014, 09:44   #44
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Re: Lightning Strikes and Cats

Our insurance company did not deny our lightning claim. We have noted on all insurance forms that we have this system in place, and none seem to care. Our current insurance company waived our deductible in case of lightning strike damage.

What if a thruhull you install fails? While I am sure that there exists insurance companies that will deny claims based on anything, the majority of them are not requiring that you stick with solely OEM equipment and never work on your boat yourself as conditions for being insured.

A zinc guppy is for electrical bonding and will not do much in a lightning strike. It would be of better use for you connected to the engine or bonding system than the mast.

Chain is a very poor lightning conductor because the contact points constructing the continuity path are very poor - the contact area of the links is small, full of corrosion or zinc plating and in motion.
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Old 22-09-2014, 10:12   #45
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Re: Lightning Strikes and Cats

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That is a common misbelief that has caused many to keep their boats ungrounded. However, there is no statistical evidence to support it, and all standards bodies recommend grounding for lightning safety.

Mark
I know that seems to be conventional thinking. I'm still not sure I buy it.

Why did Ben use the kite?

My concern with grounding is the placement of the grounding wire and as mentioned the assoc. corona. I wouldn't want it running through my cabin since that is probably were I would be hunkered down.

Probably all a moot point?
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