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Old 01-28-2011, 09:02 AM   #21
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RE: Radar/Lightning

Quote:
FF wrote:

is it possible to shield your electronics from damage if

YES BUT , to do a proper job they would all need to be disconnected from power and antennas and probably kept in a Faraday Cage .
Should*I look it up, or can you tell me what is a Faraday cage?

*
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Old 01-28-2011, 09:16 AM   #22
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RE: Radar/Lightning

KJ, it's just an electromagnetic shield, which may be how military equipment is protected - I don't know.* On board, the only ready to use Faraday cage is your microwave.* However, stuffing your electronics into the microwave is a bit inconvenient every time you hear thunder, and most boats aren't built with perhaps the next best option, which is a very straight path for a strike to follow to ground.* Even then, there is no guarantee you'll avoid damage.
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Old 01-28-2011, 09:17 AM   #23
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Radar/Lightning

Faraday cage
* It is generally accepted that this cone of protection extends 45 degrees, all around, from the tip of the metal protrusion.
This means that if the aluminum mast of the average sailing vessel is properly bonded to the vessel's other major metal masses and is given a direct, low-resistance conductive path to ground, the entire boat should fall within the protected zone.
*If the vessel has a wooden or composite mast, a marine electrician can achieve the same effect by installing a 6 to 12 inch metal spike at the top and running a heavy conductor down the mast and as directly as possible to ground, usually through the engine and propeller shaft.
.

Basically just a lightning rod*attached *of the tallest place on the boat grounded to the water.

The 45 deg thing is important as the top needs to be able to cover the entire boat so it is like a cone.**To short and the bow and stern may not fall within the protected barrier created by the. Lightening rod

SD

-- Edited by skipperdude on Friday 28th of January 2011 10:24:26 AM
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Old 01-28-2011, 11:02 AM   #24
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Radar/Lightning

Quote:
KJ wrote:
Should*I look it up, or can you tell me what is a Faraday cage?

*
The reason you are safe in your car if it gets hit by lightning has nothing to do with the rubber tires.* Lightning is so powerful it will get to the ground despite the tires.* The reason you are not cooked is the car itself is a Faraday cage.* The British TV series "Top Gear" did a fairly dramatic demonstration of this in which one of the hosts (Richard Hammond) sat in a car under the most powerful lightning generator in the world, which happens to be in Germany.* Even this thing generates a lightning strike only a small percentage of a real strike.* They fired off the rig and car lit up like a neon sign.* But Richard inside--- who had been instructed to NOT TOUCH any part of the car's body--- was perfectly safe.

A Faraday cage dissipates lightning's energy by spreading it out.* An airplane (a metal one) is a perfect example of a Faraday cage.* Planes are hit by lightning all the time, but the damage, if any, is minimal.* I've seen close-up the result of a lightning strike on the upper fuselage of a 747 (the plane had been stripped of it's paint so you could see the metal) and all there was was a slight discoloration of the aluminum.* Composite airplanes present a bit of a problem in this regard, so to ensure the same Faraday cage characteristics a fine wire mesh is embedded in the composite fuselage panels.* The 787 fuselage is wound, not made of panels, but while I don't know how they do it its fuselage stll has a "Faraday cage" of mesh embedded in it.

*


-- Edited by Marin on Friday 28th of January 2011 06:00:40 PM
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Old 01-28-2011, 02:19 PM   #25
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RE: Radar/Lightning

Wow. Great info. I didn't know any of that stuff other than the metal spike or strip in the mast.* So, I guess I would have to weigh the odds of getting hit*against the considerable effort of preventative*measures.*Thanks again for the info.** KJ
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Old 01-28-2011, 02:38 PM   #26
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RE: Radar/Lightning

Sounds like you would want a sailboat in the next slip with a mast tall enough to include your boat in the cone of protection.* JohnP
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Old 01-28-2011, 09:04 PM   #27
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RE: Radar/Lightning

Will*the aluminum in a fixed canvass enclosure act as a Faraday Cage?*

Last Summer I got scared ****less as we went through storm after storm.* Electricity is not predictable, and so I was scared I was going to die.
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Old 01-28-2011, 11:08 PM   #28
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RE: Radar/Lightning

Quote:
Egregious wrote:

Last Summer I got scared ****less as we went through storm after storm.* Electricity is not predictable, and so I was scared I was going to die.
Just make sure you have completed "final business" with your attorney before boarding*a boat.

By the way, just how many boaters have been killed by lightning during the last decade?* I'd bet it is much fewer than deaths of mountain climbers or motorcyclists.

Still, I can't understand why Floridians*even go outdoors to dare the lightning gods.

*
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Old 01-29-2011, 12:01 AM   #29
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RE: Radar/Lightning

Fishing skiff hit by lightning on a lake in Louisiana.
Two guys were in the boat.* One guy was putting the anchor away when the boat was hit. He was killed on the spot. The other guy was sitting in a plastic seat, got his butt seared a little, but walked away. You can see the exit hole in the third picture.*KJ
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Old 01-29-2011, 01:36 AM   #30
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Radar/Lightning

Almost a*hit. *That'll teach'm to own a sailboat! Thanks Keith.

[img]download.spark?ID=866280&aBID=115492[/img]

*

-- Edited by KJ on Sunday 30th of January 2011 01:50:07 AM
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Old 01-29-2011, 09:58 AM   #31
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RE: Radar/Lightning

KJ: your photo shows a foreground sailboat in front of a background lightning strike.
I well recall spending an hour watching a lightning storm deposit strikes on the land all around our anchorage, in a sailboat, where there were 20 to 30 other sailboats anchored. No boats were hit. We were frightened enough to don our floater coats, and to stay in the cockpit.
There is no predicting where a strike will actually hit, unless you have a proper lighning rod, one with experience. Most sailboats don't get hit, some do.
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Old 01-30-2011, 01:10 AM   #32
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RE: Radar/Lightning

My family had chartered 42' sloop in BVI a couple of years ago. The first night we stayed in the marina at Tortola. There was a thunder/lightning storm so intense that had to register*ten on the Richter Scale. The thunder rolled and boomed like a volley from a battleship. And the lightning, OMG! It lit the sky up so bright you read a newspaper by it. A couple of times the whole boat shook.* The very tall mast on this boat was keel stepped which means it ran through the deck and was secured to the keel. It also ran through the center cabin, right next to the bunk. My sister and her husband were suppose to*sleep in there but the mast was giving off strange zinging and popping noises every time there was a strike near us, so they slept in the salon.* The storm raged for hours.* Scared the piss out us (can I say that?).* We were sure that we were going to take a direct hit, but luckily didn't.* The next morning we took a quick run to the market for some last minute supplies and saw that the whole town had flooded. One guy said he lived there all his life and that was just about the worst storm he had seen.* The rest of the trip was however, great.* KJ
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Old 01-30-2011, 07:24 AM   #33
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RE: Radar/Lightning

Here are some links where you can learn more about lightning and how to protect your boat. I have a lightning rod on the top of my mast, and a large cable that runs into the water with a big copper plate on the end. I have a lot of cuts on the plate to increase the edge area, which is where a charge will dissipate. Can't use it while underway, but it's in the water while I'm docked or anchored.

http://www.kastenmarine.com/Lightning.htm
http://marinelightning.com/
http://www.lightningsafety.com/nlsi_...od_recent.html
http://www.lightningsafety.com/


I had more links, but a surprising half of them no longer work. Oh well, these should provide a lot of good information.
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Old 01-30-2011, 04:25 PM   #34
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RE: Radar/Lightning

We use to live and cruise on*a sailboat.* We kept a pair of jumper cables that we clipped to the standing rigging when lightning storms were in the area (at anchor).* The idea was to give the lightning an easier path to the water.* Did it work, I have no idea for we were never hit.**We also put the laptops,*GPS and other removable electronics in the oven.*The only problem was I left a laptop in the oven and turned*the broiler on and cooked the lid of the laprop till it bubled.* The computer still worked.* I would use the oven again but put a tag on the gas switch next time.

Would the jumper cables or oven really do any good?
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Old 01-31-2011, 12:32 AM   #35
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RE: Radar/Lightning

Has anyone here ever seen St. Elmo's Fire?
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Old 01-31-2011, 06:53 PM   #36
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RE: Radar/Lightning

I guess that would be a no.
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Old 01-31-2011, 07:00 PM   #37
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RE: Radar/Lightning

Quote:
Larry M wrote:


Would the jumper cables or oven really do any good?
Larry, that's funny.* We carried the same thing off shore, and I think the answer is no, they wouldn't help.* But I'm down with you on the concept!

*
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Old 02-01-2011, 04:31 AM   #38
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RE: Radar/Lightning

Has anyone here ever seen St. Elmo's Fire?


Not on a boat , yes on an an aircraft in a snow flurry.
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Old 09-23-2014, 04:29 PM   #39
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I see St. Elmos fire lots of times over the last 33 years in the air. Almost always in heavy precip, in IFR conditions. Its just a build up of static electrcity. Been hit by lightning several times, from mild to severe damage, but not to the occupants as we were in William Faraday's "cage".
My question for you all is, the mast on my trawler is stepped through the coach roof and down to the salon deck. I will of course ground it to a bronze plate on the bottom outside hull, but if it gets hit, is there a danger to people inside the salon?
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Old 09-23-2014, 06:39 PM   #40
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Quote:
Originally Posted by stevensibs View Post
I see St. Elmos fire lots of times over the last 33 years in the air. Almost always in heavy precip, in IFR conditions. Its just a build up of static electrcity. Been hit by lightning several times, from mild to severe damage, but not to the occupants as we were in William Faraday's "cage".
My question for you all is, the mast on my trawler is stepped through the coach roof and down to the salon deck. I will of course ground it to a bronze plate on the bottom outside hull, but if it gets hit, is there a danger to people inside the salon?
You never can predict with any accuracy what lightning will do after it strikes an object. To answer your question it could injure people almost anywhere near or on the vessel. I wouldn't limit the area, the degree of damage or the range of damage a direct lightning strike can cause to a vessel or anyone on or near the vessel. I think it's a good idea to ground the stepped mast to the Bronze plate there are 2 schools of thought with lightning protection do nothing and since lightning generally seeks a ground an ungrounded vessel may not have lightning discharge in or at it at all, the next step is to bond and ground everything in and out of sight. However the one path you missed will probably be the area that gets the most damage from a lightning strike.
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