Lightning.... I've been HIT !!!!!!!!!!
- Thread starter Maine Sail
- Start date
Wow, can't tell you how sorry I feel. I know after spending countless hours an a project I say to myself " don't want to do that again". The level that you work far exceeds mine. Again, reel sorry to hear this. Is this the first time you've been hit? The boat moored just behind me got hit a few years back and lost his electronics. Nothing happened to ours. I was anchored out Saturday night when a thunder storm passed. I lied awake with the sky lighting up with lots of rain and wind. I was a little worried I might have to let out a little more scope that would make me have to go topside. Fortunately I didn't. What's the chances of being hurt if you were aboard for a hit?
Correct me if I'm wrong here, just a thought...the battery switch disconnects the positive side of the battery to the electrical panel. But the ground side doesn't have a switch so all the wired electronics are connected to the grounding system all the time. So voltage from a lightning hit will charge up the wires to all the electronics and while current can't flow since the positive side is shut off, the huge voltage will likely fry most of the components and will cause arcing across large air gaps that small voltages would never jump. Given that Maine Sail had his hand helds and things like Ipods destroyed is another case for an EMI burst.
Maine just wondering if you should haul out and see if any other damage? Somewhere over the years I'd heard about ending up with porosity in the hull near the water line where the current apparently flowed through the glass to the water. Seems hard to believe but probably worth checking out, or maybe at least grab a mask (and wetsuit) and taking a look around under water. Maybe you can get a brand new yacht from the settlement?
Maine just wondering if you should haul out and see if any other damage? Somewhere over the years I'd heard about ending up with porosity in the hull near the water line where the current apparently flowed through the glass to the water. Seems hard to believe but probably worth checking out, or maybe at least grab a mask (and wetsuit) and taking a look around under water. Maybe you can get a brand new yacht from the settlement?
Hey Dave, you make a very good point about the ground being the conduit for the energy to travel back up into your electronics. This would be a relative easy mod. to add a ground disconnect to the engine/prop shaft or any other point such as a keel bolt/ground plate and may make a difference in a marginal strike next to the vessel in the water. Again, I'm not saying isolate the ground post of the bat, like the way a shut off does for the +12, but isolate any connection from the water to the DC ground bus bar. Obviously this could not be done while operating, but when not, why not? The type of switch would be important, maybe use a large knife switch, being mindful of corrosion susceptibility. Unfortunately most measures to try to reduce the chance of damages are futile in a direct or strong indirect hit. We're talking about masive potential differences and sparky will find a way.
Maine Sail...
Jibes makes a great point that I forgot about. Over the years two different boats in my marina have taken direct lightning hits. Both were found to have pin-hole penetrations along the waterline and near the keel afterward.
Might be worth a dip with a mask to take a look. Unexplained water in the bilge could be a sure sign.
Jibes makes a great point that I forgot about. Over the years two different boats in my marina have taken direct lightning hits. Both were found to have pin-hole penetrations along the waterline and near the keel afterward.
Might be worth a dip with a mask to take a look. Unexplained water in the bilge could be a sure sign.
I too say sorry to hear such bad news.
But as I'm redoing some of the 12v stuff and adding electronics it has made me start thinking.
In practice one of the things that helped reduce the damage in my radio studios was that every interconnected piece of equipment had a common chassis ground of decent size (say #14 at least). Not relying on power leads, or the "ground" lead in any interconnect cables. If that's done once the big magnetic field rams through the place, everything rises and falls together. And that reduces the high current flowing between the individual devices on the interconnect cabling.
So I can see that I'll be adding a flock of MOVs across the power leads, maybe zeners on the data leads, and a nice common buss.
But as I'm redoing some of the 12v stuff and adding electronics it has made me start thinking.
In practice one of the things that helped reduce the damage in my radio studios was that every interconnected piece of equipment had a common chassis ground of decent size (say #14 at least). Not relying on power leads, or the "ground" lead in any interconnect cables. If that's done once the big magnetic field rams through the place, everything rises and falls together. And that reduces the high current flowing between the individual devices on the interconnect cabling.
So I can see that I'll be adding a flock of MOVs across the power leads, maybe zeners on the data leads, and a nice common buss.
Interestingly enough I was on the boat today with the adjuster and he was interested in the GPS devices that were not connected and fried. I had an extra Magellan unit that was in my ditch box and I thought would be working after the strike because I had it wrapped in tin foil.
I was comparing one that got fried, my 176, and the Magellan which had been wrapped in tin foil and in a ziplock bag with desiccant.. I pulled it out confident to show him how well the tin foil worked at protecting it and while we were watching it the unit began to blink and then died.. It too is TOAST! Tin foil DOES NOT work as a Faraday cage..... Multiple GPS devices dead and one was wrapped in foil to "protect it". So much for the foil Faraday cage idea an "expert" swore by..
So just what can you do to REALLY protect your wired equipment from lightning. IMHO nothing.. For non-wired a true metal Faraday cage might work but the tin foil Faraday idea failed.....
I was comparing one that got fried, my 176, and the Magellan which had been wrapped in tin foil and in a ziplock bag with desiccant.. I pulled it out confident to show him how well the tin foil worked at protecting it and while we were watching it the unit began to blink and then died.. It too is TOAST! Tin foil DOES NOT work as a Faraday cage..... Multiple GPS devices dead and one was wrapped in foil to "protect it". So much for the foil Faraday cage idea an "expert" swore by..
So just what can you do to REALLY protect your wired equipment from lightning. IMHO nothing.. For non-wired a true metal Faraday cage might work but the tin foil Faraday idea failed.....
My understanding is that Faraday cages DO need to be grounded. If it’s NOT grounded, then the Faraday cage merely becomes a reflector or an amplifier.
I infer the tin foil wrap wasn't?
I infer the tin foil wrap wasn't?
I scanned the Faraday cage entry on wikipedia. It discusses the grounding issue a little bit and it does not seem to indicate that you have to ground the cage for it to be effective.
http://en.wikipedia.org/wiki/Faraday_cage
BUT, it does say that conductivity and thickness of the cage walls is important. More conductive material and thicker walls provide better protection. Tinfoil wrapping sounds like a pretty weak cage, a thicker walled box of copper or aluminum would be a better bet.
http://en.wikipedia.org/wiki/Faraday_cage
BUT, it does say that conductivity and thickness of the cage walls is important. More conductive material and thicker walls provide better protection. Tinfoil wrapping sounds like a pretty weak cage, a thicker walled box of copper or aluminum would be a better bet.
I also don't think a Faraday cage needs to be grounded to work - its purpose is to keep electric fields inside the cage small, has nothing to do with grounding.
A lightning strike will generate both an electric and magnetic field. For the electric field, a good conductor is needed so aluminum or copper are typically used. But for the magnetic field, I don't think aluminum does much at all - you need something like "mu-metal". FYI, for an explanation, I liked post #14 in this thread http://cr4.globalspec.com/thread/49714/Mu-metal-Faraday-Cage
The parameter which mostly matters for the magnetic field is permeability http://en.wikipedia.org/wiki/Permeability_(electromagnetism)
Note in the table on the link that the "relative permeability" of aluminum is just a hair over 1 - ie, its pretty much no different than air in regards to absorbing the magnetic filed - ie, not effective at all. Steel (ie, microwave oven) is about 100 times better than aluminum. Mu-metal is very good for attenuating the magnetic field being 20 thousand times better than aluminum.
But.. both steel and Mu-metal are a lot less conductive than aluminum so wont be as effective for the electric field.
Anyhow, looks like from the data point here (wrapped in AL GPS damaged) that the magnetic field is also important to worry about..
FYI, sorry about this happening - I would be seriously bummed... I think it would be interesting to also look at your keel to see if there was any evidence of a direct strike..
A lightning strike will generate both an electric and magnetic field. For the electric field, a good conductor is needed so aluminum or copper are typically used. But for the magnetic field, I don't think aluminum does much at all - you need something like "mu-metal". FYI, for an explanation, I liked post #14 in this thread http://cr4.globalspec.com/thread/49714/Mu-metal-Faraday-Cage
The parameter which mostly matters for the magnetic field is permeability http://en.wikipedia.org/wiki/Permeability_(electromagnetism)
Note in the table on the link that the "relative permeability" of aluminum is just a hair over 1 - ie, its pretty much no different than air in regards to absorbing the magnetic filed - ie, not effective at all. Steel (ie, microwave oven) is about 100 times better than aluminum. Mu-metal is very good for attenuating the magnetic field being 20 thousand times better than aluminum.
But.. both steel and Mu-metal are a lot less conductive than aluminum so wont be as effective for the electric field.
Anyhow, looks like from the data point here (wrapped in AL GPS damaged) that the magnetic field is also important to worry about..
FYI, sorry about this happening - I would be seriously bummed... I think it would be interesting to also look at your keel to see if there was any evidence of a direct strike..
An electro-magnetic pulse is a moving magnetic field that induces current in a conductor. Your electronic devise without protection is full of conductors that are subject to this induced current. An aluminum pot with a lid will be a single shorted turn of conductor that will shield the content from the pulse. It will be worthless against a strong stationary magnetic field but that won't induce any current. The Faraday cages they used in the Air Force were rooms that were completely covered with bronze screening. This shielded the content from radio frequency signals and noise and allowed for testing without outside interferience complicating the results.
I think I'm hearing put your electronics in a steel box that is grounded and then put the steel box inside an aluminum box (might as well ground that too) in order to be really safe but there is a high probability that won't work either? So how do airplanes get hit once a year on average without major issues? I'm going to grill the EE's in my plant and see what they say. Stay tuned.
Meanwhile many people recommend dropping sails and kicking on the engine in a storm, just wondering if the lightning will kill the engine also as the electric fuel pump might get zapped, or the batteries, and the alternator and regulator will likely suffer?? Maybe storm sails are a better option if a bad one is brewing?
Meanwhile many people recommend dropping sails and kicking on the engine in a storm, just wondering if the lightning will kill the engine also as the electric fuel pump might get zapped, or the batteries, and the alternator and regulator will likely suffer?? Maybe storm sails are a better option if a bad one is brewing?
lightning zapping a diesel
except for the electric fuel pump, the only thing that lightning might do to a diesel engine is mar one of the journels as large currents pass between the moving parts. I doubt that this would stop the engine though.
except for the electric fuel pump, the only thing that lightning might do to a diesel engine is mar one of the journels as large currents pass between the moving parts. I doubt that this would stop the engine though.
The large pulse associated with a lighning bolt has frequency components that span a very large segment of the frequency spectrum. Those frequency components that have wavelengths on the order of the size of the wires, printed circuits, etc., etc. that are in the inventory of most yachts will couple with the equipment and set up large AC currents. Further more, a single isolated wire can conduct current if it is acting like an antenna.
You don't need a circuit ground to conduct a current and you don't need large amperages to blow sensitive electronics. All you need is a potential difference within a circuit and enough current to exceed specs. For modern chips and boards, that may be a small bar to pass. I wonder if some sort of shielded cases might be the way to go for the person determined to fend off Mother Nature and Father Physics? btw, thanks for the link.
Many home appliances are controlled with microprocessors. The service manual requires the technician to wear a static ground strap while working on the control circuits.
When I was in the Phillipines we had a storm in the area of our radio shack. We had a long wire antenna connected to an outlet on the bench. During the storm the static would build on that antenna an discharge across theoutlet on the bench. It produced a nice fat spark about a half inch long with a good snap to go with it. I am sure that it would have damaged modern electronic circuits.
Holy Crap. That really sucks. There has been horrible storms around here this season.
That is a high deductable for your boat! I think that mine is around $500.
That is a high deductable for your boat! I think that mine is around $500.
for all you considering lightning protection--remember the neighbor of nice n easy's who is a NASA engineer whose boat was the only boat in the neighborhood to be struck 2 times in 4 yrs and the last time the wiring to the house was involved as well---he was very very well protected. how is the protecting system going to protect when it seems to be the attractor for the lightning???? this engineer's first strike on his 50 ft bendytoy took 6 months to repair, this time will be over a yr for repairs......
none of the unprotected boats was in any way approached by lightning..something to think about, as lightning is truly random. we sailed thru lots of it--scared the willies out of us but we were not hit in all the time we tempted the gods with our lightning rod in motion in the gulf seas...
i jokingly say it was the crocs and kat that kept it away--there is no recorded history of any cat being hit by lightning. therefore i have a potential anti-zap kathat living with me...i had crocs on my feets, gloves on my hands, and a rubber rainsuit...not even a neck hair on end..not even a tingle...we were fortunate....
none of the unprotected boats was in any way approached by lightning..something to think about, as lightning is truly random. we sailed thru lots of it--scared the willies out of us but we were not hit in all the time we tempted the gods with our lightning rod in motion in the gulf seas...
i jokingly say it was the crocs and kat that kept it away--there is no recorded history of any cat being hit by lightning. therefore i have a potential anti-zap kathat living with me...i had crocs on my feets, gloves on my hands, and a rubber rainsuit...not even a neck hair on end..not even a tingle...we were fortunate....