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Old 18-07-2015, 16:51   #31
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Re: Offshore Sailing in Thunderstorm far from land

A few years ago, a bolt of lightning hit a tree a bit over 100 feet from the house. Plenty of trees around us but that one collected the bolt. Not a cloud in the sky. The storm front was 20 or so miles to the west of us.... I should have been under the tree splitting firewood but figured the storm was too close to get much work done. Not sure if I would have lived if I had been out there...

The tree had green leaves on in for a few months after the strike, and then one day, the leaves were all brown. Very odd.

Did I mention the storm was 20ish miles away. Not a cloud in the sky near us....

Later,
Dan
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Old 18-07-2015, 16:59   #32
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Re: Offshore Sailing in Thunderstorm far from land

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A few years ago, a bolt of lightning hit a tree a bit over 100 feet from the house. Plenty of trees around us but that one collected the bolt. Not a cloud in the sky. The storm front was 20 or so miles to the west of us.... I should have been under the tree splitting firewood but figured the storm was too close to get much work done. Not sure if I would have lived if I had been out there...

The tree had green leaves on in for a few months after the strike, and then one day, the leaves were all brown. Very odd.

Did I mention the storm was 20ish miles away. Not a cloud in the sky near us....

Later,
Dan
Apparently it's not unusual for lightning to strike 10+ miles from the storm front. This is why it think it is probably not wise to try to disconnect cables from electronics once a TS is near, not to mention that the electro-magnetic pulse from a strike will probably fry them regardless.
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Old 18-07-2015, 19:16   #33
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Re: Offshore Sailing in Thunderstorm far from land

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How do you have your pressure cooker grounded? For that matter how do you have your stove grounded?
Does not need to be grounded - best if it is not. Faraday cage is as close as possible to a metal surround. Electrons repel one-another so they stay in the 'cage'. Here is the most awesome example of a cage.

In your boat, the combination of shrouds and ground strips running throughout the inside of the hull are supposed to approximate a Faraday cage so that the interior is relatively not on the path. A hard direct hit will find its faults.

We have added air dry break double pole switches to break the + & - power to non-removable instruments including the antennas. Alternately, we pull the power leads & antennas off from the back of the nav station access. Portable GPS is in my pocket or the microwave.
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Old 18-07-2015, 19:27   #34
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Re: Offshore Sailing in Thunderstorm far from land

Don't worry, you've got a better chance of being struck by lightning than......um sorry, belay that.

I just sail next to someone with a taller mast. Crisis averted.


goat (helpful once again)
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Old 18-07-2015, 19:41   #35
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Re: Offshore Sailing in Thunderstorm far from land

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Once lightning is in sight I really don't want to be involved in unplugging antennas....

I guess thats why they invented crew.....

However...

Maybe something like a Delta 2 ( or one of their other products) http://www.alphadeltacom.com/pdf/prices_switches-3.pdf
would work.
remind me never to crew your boat!
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Old 18-07-2015, 19:52   #36
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Re: Offshore Sailing in Thunderstorm far from land

Frankly I don't get it. Google, wikipedia etc say a grounded metal cage. Who are you guys who say it is not?
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Old 18-07-2015, 20:47   #37
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Re: Offshore Sailing in Thunderstorm far from land

I'm with Uncivilized, pour a stiff one and don't touch any metal. Enjoy the show and think, not many can say they've been through this.
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Old 18-07-2015, 21:09   #38
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Re: Offshore Sailing in Thunderstorm far from land

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Frankly I don't get it. Google, wikipedia etc say a grounded metal cage. Who are you guys who say it is not?
Read again, it says grounding for "screened room" for testing, and later "if the cage is grounded" in contex with internal charges. Both of them has nothing to do with caging electronic equipment against lightning strikes and EMP's.
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Old 18-07-2015, 22:46   #39
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Re: Offshore Sailing in Thunderstorm far from land

Lightning has been documented to strike 30 miles, laterally, from the storm clouds. So what the latest advisories are, is that if you can see it, or hear the thunder, get inside and protected as best you can, immediately. 30 miles is an extreme case, but that's how far it can reach out sideways.


Somewhere there's another thread by one of the full time researchers in Florida on this, I think he's still off on vacation right now. The new research they've come up with is that the ground charge is not IN the water at all, but rather, the payer of damp salty air in the two feet ABOVE THE WATER is where the charge is building up, and where the lightning wants to dissipate. Not into the water, but on the surface of it, is the air that is full of conductive charged particles. Similar to the ice particles in the clouds that are causing the ruckus upstairs.


So they are recommending a new approach using multiple discharge points, on each side of the hull, clear ABOVE the waterline.


That would mean dangling chain or bare cable, which passes through the "surface mist", would be greatly more effective than insulated battery cables which passed through and only were "grounded" below the water's surface.


They could just be on to something there.
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Old 18-07-2015, 23:39   #40
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Re: Offshore Sailing in Thunderstorm far from land

One of the best answers I've ever see on the subject of lightening goes something like this...

If there was a way to avoid or successfully dissipate a lightening strike the insurance companies would make every masted boat conform in order to obtain insurance.

One person here (Robin3) said they had a lightening strike right next to their boat. Why didn't it strike the mast? By placing a conductive path to the water or just above the water would that have assured a strike? Electricity seeks the path of least resistance so perhaps by providing a better conductive path you are inviting a lightening strike onto your boat. I don't think anyone really knows for sure.

A Faraday cage is the best possible solution in the event of a direct strike. You could also put your small electronics into a plastic bag and wrap with aluminum foil. If you place anything in an oven or microwave it should be insulated, like in a plastic bag, and not touching any metal surfaces. Layers of protection is better so wrap up small, portable items and then put them in a microwave or oven.

I think the best solution is detection and avoidance first and foremost. Second would be mitigation and protection of electronic equipment. Third would be just to hope for the best and take your chances.

If lightening is going to hit you I don't think you get a vote in the matter.
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Old 19-07-2015, 01:14   #41
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Re: Offshore Sailing in Thunderstorm far from land

My boat is all aluminium- does anyone Know if the boat is more attractive to lightning ? In the event of a strike, would the charge pass easily and minimise damage ?
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Old 19-07-2015, 01:27   #42
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Re: Offshore Sailing in Thunderstorm far from land

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Don't worry, you've got a better chance of being struck by lightning than......um sorry, belay that.

I just sail next to someone with a taller mast. Crisis averted.


goat (helpful once again)
Goat, I don't think that will work. A few years ago, here in Manly Qld we had a strike in the marina. It hit the mainmast of a Spray replica which was berthed between two sloops with considerably taller masts... less than twenty feet away on one side and about 25 on the other. The spray's damages amounted to over twenty thousand bucks, his neighbors very little (don't remember their details).

Lightning is capricious... better try sacrificing a virgin or two if you want to propitiate Thor!

Jim
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Old 19-07-2015, 05:23   #43
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Re: Offshore Sailing in Thunderstorm far from land

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Goat, I don't think that will work. A few years ago, here in Manly Qld we had a strike in the marina. It hit the mainmast of a Spray replica which was berthed between two sloops with considerably taller masts... less than twenty feet away on one side and about 25 on the other. The spray's damages amounted to over twenty thousand bucks, his neighbors very little (don't remember their details).

Lightning is capricious... better try sacrificing a virgin or two if you want to propitiate Thor!

Jim
Crisis returned. My boat is berthed in LA right now, better chance of being hit by lightning than finding two virgins.

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Old 19-07-2015, 06:34   #44
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Re: Offshore Sailing in Thunderstorm far from land

I read an extensive article about lightning strikes and the ones that involved death or shock to humans were because they were changing there electrical potential!! as in anchor touching bottom BOOM, holding backstay lowering out board into the water BOOM,stepping ashore BOOM,etc so if you are going to make changes make them early!!!
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Old 19-07-2015, 07:18   #45
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Re: Offshore Sailing in Thunderstorm far from land

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That's Darwin award level stuff right there, boy.

Offshore, generally you see them coming unless cloudy night without a radar signature. We try to steer around them or slow down for them to pass, but sometimes they seem to be tracking you down. We won't go crazy to avoid them and cut through the trailing edge or just take our lumps if need be.
Yep.. Guilty. Thats why I shared. Might prevent someone else doing the same thing.

She could sail the boat but not stop it. .
I had "assumed". That was the mistake. The assumption that another person had the skills required without first checking or testing them.
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