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View Poll Results: Which best applies to your experience with lightning aboard boats?
Never heard of anyone's boat getting hit 7 15.91%
Heard of someone's boat getting hit through a friend 5 11.36%
Personally know someone's boat that was hit 23 52.27%
My boat was personally hit 9 20.45%
Voters: 44. You may not vote on this poll

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Old 01-12-2006, 15:56   #1
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Lightning?

The other day, I was reading a thread on here that spoke about Pblais's thought about being a shorter mast next to taller ones. It also touched on the fact that a good number of you have seen and/or have been struck.

For the sake of stats, can we fill in a quick poll on who you know that's been hit, if you've been hit, or if you aren't sure of anyone you know being hit?

I'm getting more apprehensive about this topic as I am frequently the only guy out there in a harbor all by myself at anchor when the storms roll through. I'm also in a plastic boat, which spells disaster if the lightning decides to take a path through the plastic.

Does the anchor and all chain rode hurt the situation any, creating a virutal lightning rod underwater while at anchor?
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Old 01-12-2006, 17:04   #2
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Sean,

I'm around lightning a lot Several of my friends have been hit and I have had strikes come very close to me within 200 yards I'm almost convinced that there isn't much you can do about it. Two of my fiends were in wood boats and two were in plastic boats and one was in a aluminum boat. All power boats.
I saw a small center console get struck about 150 yards from me my wheel house is 15 feet off the water and he was hit at maybe 8ft. off the water. I also had lightning hit about 80 yards. from me close enough that it charged up my hand rails and shocked a couple of people thankfully not bad. scared them worse than anything (my niece now wears shoes on the boat.) I also had lightning hit the end of the jetty when I was no more than 200 yards from it and I'm taller than it also. so I have a hard time buying that being the highest thing around guarantees your going to get hit.
My boat did get surged from a strike in the slip one night it fried all my electronics on my main engines and cooked both of my chargers but left everything else alone. the marina building and the restaurant next door lost some computers.
I don't know what the answer is but I have a theory that the composition of the bottom might have some thing to do with it. That little boat was very close to a sunken liberty ship when he got hit maybe all that steel laying on the bottom had some effect. on the other hand one of my friends was doing 16 knots and was in an area were the bottom is mostly sand and mud so who knows if you figure it out let me know when the stock is about to go public
The only thing I know for sure is when its around I get really nervous! I wouldn't want to be wearing a hat like this
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Old 01-12-2006, 17:12   #3
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Dr. Ewen Thompson, the Florida researcher that wrote one of the best write-ups on lightning I've seen, has recently put up on a website and is marketing some interesting looking devices for boats. The website has lots of good information, as well as a description of his most recent finding and what he thinks is the best ways to protect boats, currently.

http://www.marinelightning.com/

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Old 01-12-2006, 17:38   #4
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I know of two boats that have been hit by lightning, both plastic, neither damaged beyond some lost electronics. One of the most sublime experiences of my life was being on the summit of Notch Mountain (4100m) during a lighting storm. Anyway, BOATUS states that having a lightning strike punch a hole in the boat or breaking a thruhull is rare. They suggest a ground plate linked to the shrouds (Seaworthy P225).
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Old 01-12-2006, 18:41   #5
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When we got hit our electric start Yamaha 9-9 o/b was in the piss as we were trying to keep the nose to weather. We had all electrics toasted through the boat, radios , auto-pilot, depth, wiring blown out of conduits that were glassed in, log'sbut all the cheap fluoro's and nav lights were OK.

The motor lost it's main fuse, but the prop has a rubber bush in it and that melted, so we could not motor.

We were a bit sus about sailing as there was fiberglass blown off and scorch marks around the chainplates, so well reefed and took it easy.

All was replaced including dropping the rig and all wire re-done on insurance whih was good.

We also had taller mast's within a couple of hundred feet of us at the time, but they did'nt get hit.

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Old 01-12-2006, 18:44   #6
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static vs. dynamic strikes

For years many boaters have avoided bonding and grounding their masts and rigging pointing to those boats which were properly grounded that were hit anyway. First of all there is a logical problem with this reasoning in that bonding and grounding does not guarantee that one will not be hit. proper grounding WILL, however, tend to minimize damage yet will not prevent the inducement of voltages and currents in any conductors on a vessel caused merely by the magnetic flux rate of change caused by a discharge.

In addition, there are at least two types of lightning discharge: static and dynamic. Both types create magnetic flux intensity and rate of change that can induce damaging voltages and currents in isolated and insulated devices.

The so-called "cone of protection" geometrically does tend to protect a volume of space within the cone created by the top of a grounded rod (translation: mast) due to VOLTAGE GRADIENTS that build statically in a relatively uniform medium of air and humidity. Voltage gradient measuring devices have been in use for decades to warn of potentially imminent strikes. For example, if 5 Volts per millimeter voltage gradient is measured then a bilge-stepped mast 50 ft off of the ocean surface can "see" over 76,000 Volts. Depending upon the standoff voltage rating of the hull separating the mast foot from the ocean a punch through may or may not occur because that voltage is delivered right down to the bottom of the mast. Obviously a 50 V per millimeter voltage gradient will cause sufficient potential to shoot through anything on the way to the sea. This is why grounding the mast is a good thing. As the voltage gradient builds in the vicinity of the vessel the mast top bleeds off the potential directly to "ground" and possibly no strike will occur.

I have worked on several boats which were not grounded and showed various carbon paths on the hull from the mast and/or rigging to the sea after such strikes. If sufficient energy is available a hole may be created and that is the big concern if it is below the waterline, naturally.

Dynamic discharges can occur from various phenomenon related to the movement of air carrying charge and inducing charge by the relative movement and mass. These can be huge, violent, and capricious in that one cannot predict the development or path of the discharge. I believe that it is these types of discharges that feed the negative arguements against grounding a vessel's structural components.

I spent some time at sea in the convergence zone near the equator. Every evening the same scenario occured: beautiful day with puffy clouds and variable winds (if any) give way to dusk and gathering black clouds everywhere. Reef down, because soon 35 knot winds blast you with heavy rain and lightning all around. After several days of this we had to adopt an attitude resigned to the fact that one may or may not get hit and there just isn't much you can do about that. The BIG deal was, though, many times lightning struck right near the boat without ever striking the mast or rigging towering over the space in the vicinity of the strike. This was dynamic lightning discharges at play with all that action. So, merely the fact that a conductor is above the surface of "ground" does not mean that lightning is "attracted" to it. That is a myth with such dynamics at play. With statics, thought, one's rig had better be grounded.

When I finally was "hit" it was at anchor in an outlying island off of Panama. I counted 5 boats within 3 months that got hit in the same general area. All of us sustained at least some damage to electrical devices totally insulated and isolated. For example, the speed control for the sewing machine, stowed with the machine in one of those plastic carrying cases, was destroyed. The lightning obliterated the VHF antenna, traveled down the coax shield (glad I had the large diameter RG-8 at the time which has a lot of copper in the shield) ruining it as well and "jumped" over to the depth sounder shield blasting the outer layers of the depthsounder into the sea. No leaks resulted but I then wished that I had a lead-line.

One interesting thing to note was that the masthead windspeed transducer used a Hall-effect transistor to measure a rotating magnet. One lead to the device was "fused" off. I was able to solder it back on to the base of the transistor package and the windspeed worked again! Wow!
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Old 02-12-2006, 09:37   #7
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Wow. Thanks, Rick. This helps a lot in understanding, rather than fearing lightning. I also just sort of say to myself, "well... I might get hit today and personally be struck..." Seems about all you can do, other than have a fully bonded system to bleed off the static charges.
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Old 02-12-2006, 10:16   #8
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And make sure that insurance is payed up!



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Old 02-12-2006, 10:27   #9
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Shiva sustained some damage when she was quite new in the late 80s during a passing T storm on Spring on the mooring. I arrived to find some gear not working... B&G board was fried and replaced... perhaps the loran too... my first... Sitex. It wasn't a direct strick as there was no evidence of it... so it must have been near by, but near enough to cause some damage to the B&G board and the loran. How peculiar the way that works.

Since that time no damage to report from electrical storms... but seeing those thunder bolts is not especially comforting eh? I marked the poll as having a strike... but my experience was not technically a strike... but defintely electrical storm damage. I suspect this might be more common than actual strikes. No?

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Old 02-12-2006, 10:36   #10
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Lightning is one of the scariest things to me when I am on the water. I do not fear my body being hit as much as my electronics getting wiped out.

(this is a genralized paragraph)
Here is a cenerario for you, a modern sailor is out on the water, lightning strikes the boat and wipes out the electronics. The modern sailor is now literally dead in the water. That would have been me a few short months ago. When you have a boat that is outfitted with the latest electronics and have no idea how to navigate without them you are in serious trouble!
I am enjoying my time down right now while I shop for a replacement to the M 50. I am reading a book a day and taking some courses through the coast gaurd, but more helpful than anything else is an old salt I have run into in all places the califonia desert. With charts at hand I am actually learning that a compass is more than a decorative item and a sextant does something more than look cool on my wall.
It is true that anyone with some cash can buy a boat, buy a race car, buy a gun etc etc. without realizing that all of these items and many more are serious accidents waiting to happen.

Ok with that said I still do not want to be in the middle of the ocean and loose my electronics to lightning.
My lightinig plan on any boat I own typically starts with a lightning diffuser on the mast. I would like to take as many precautions as possible.
Could someone answer the question: Does the anchor and all chain rode hurt the situation any, creating a virutal lightning rod underwater while at anchor?

What do you do to protect your electronics? Do you keep an extra vhf radio and gps in a heavily insulated box? If so what type of box would protect against a strike?
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Old 02-12-2006, 11:08   #11
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anchor down and electronics protection

Electromagnetic waves consist of two components: an electrical field and, nearly at right angles to that, a magnetic field. In order to protect electronics one must prevent both fields from passing through the space occupied by the protected device. This can only be done with a ferrous and conductive material, like steel. Preferably a steel box with an overlapping lid. ANY gaps can allow high frequency components to pass through potentially producing damaging voltages and/or currents.

Various conducting non-ferrous foils do nothing to stop a magnetic field. Even if one were able to completely block the electrical component any relative change in either intensity or space by the magnetic field can, and do, induce damaging voltages and currents.

Again, the only way to ensure that a piece of electronics is protected is by placing it completely in a conducting ferrous enclosure that is capable of not saturating at whatever magnetic intensity is delivered by a lightning strike.

There is no reason to believe that an all-chain rode and anchor is detrimental to your safety when in a lightning storm, in fact, the obverse is probably true.
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Old 02-12-2006, 16:24   #12
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It seems that proper grounding is probably the best way to go. Not being grounded doesn't seem to lessen the odds of being struck, but does seem to increase the damage potential of a strike.

My plan is to glass in a conduit pipe from the mast base through to the bridgedeck floor. I will have a length of copper rod which I can pass through this conduit, down to the water, and bolt to the mast.

I think this should help reduce the damage of a strike when at anchor anyway, but I need to think of something else for when underway.

I always keep a handheld GPS in a metal box. Hopefully it would survive a strike.
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Old 02-12-2006, 16:26   #13
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Oh, I get it, Rick! So are you saying the all chain anchor and rode might help, acting as a conduit for a strike to get it the heck off the boat and down safely to the seabed without so many sideflashes?

That makes a lot of sense. Depending on many dynamics, I could sort of envision it attracting to the foresay and jumping to the chain. Of course, this is purely imaginative, not mathematical at all.

I might start keeping my handheld GPS in a Faraday cage just in case.

Thanks for all the great posts so far... and thanks Chris for bringing up the idea.
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Old 02-12-2006, 16:30   #14
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Hey Sully

I was just reading in Nigel Calders book about lightening protection and a case he quotes of a boat anchored with all chain rode that was struck and the chain acted as a conductor to route the charge to ground. Apparently the last few links near the anchor disintegrated and the boat set adrift and up onto the rocks. I just found it funny that this discussion was going on and I just happened to read it in this book! Go figure.

PS. Look what I added to my electrical system drawing today! Do do de de do do just like an episode of the Twilight Zone!

Rick
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Old 02-12-2006, 18:33   #15
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Faraday cage

Sean,

Keep in mind that a Faraday cage works based upon uniformity of a sphere and charge distribution. It will be better than not having one yet if one is going to put a GPS in a metal box why not make it steel and be able to contend with the magnetic field as well?

Also, many people forget that a classic physics experiment is to place a person inside of one and pass a high voltage dischage to the cage to show that inside there is no voltage gradient. This will work for animals because magnetic fields do not affect them yet a piece of electronics can still be damaged inside of a Faraday cage not made of ferrous material (or mu-metal or the like).
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