lightning protection

[gmeyerga]

An experienced cruiser told me that he turns on his masthead
anchor light in thunderstorms because it helps guard against
a lightning strike.
Is that just one man's opinion?

 

[Scott B]

It's amazing the things you hear on the docks .....

 

[kloudie1]

We used to honk our horns sometimes on high speed motorcycle runs.. We did that to scare the elephants out of the road.. That always worked.. Never saw one.. ??

 

[Maine Sail]

An experienced cruiser told me that he turns on his masthead
anchor light in thunderstorms because it helps guard against
a lightning strike.
Is that just one man's opinion?

I suspect for every theory on lightning & boats there is and will always be a strike that will disprove it...

You want lightning protection? Here's a theory, keep your boat in a barn and it should be okay unless of course the barn is hit.........

 

[gfrazzle]

This only works in the Northern hemisphere. If South of the equator, one must turn on the running lights or reverse the polarity of the batteries.

 

[T37 Phil]

I suspect for every theory on lightning & boats there is and will always be a strike that will disprove it...

You want lightning protection? Here's a theory, keep your boat in a barn and it should be okay unless of course the barn is hit.........

Well said! Another option is a concrete boat with no metal fixtures or instruments.

 

[alexco38]

Static

In theory a Van de Graaff generator tie to the mast works the best. Neutralize the static electricity. But if the theory is wrong, it might actually attracts them.

 

[woodster]

An experienced cruiser told me that he turns on his masthead
anchor light in thunderstorms because it helps guard against
a lightning strike.
Is that just one man's opinion?

when my mother was carrying me at about 6 months...she was carrying a stack of 78 RPM records across the room and droped them and cracked them....but it didnt effect me...effect me...effect me

woody

 

[Warren Milberg]

Lightning will do whatever it pleases, regardless of what we sailors do. The only thing that surprises me about lightning is that there aren't more strikes on sailboats.... My only close call with lightning was bizarre. I was crewing on an IP 38 and a line squall came up. Lightning hit the water about 25 ft off the bow -- but not the boat with a huge metal mast sticking up. Our hair stood on end. All the electronics zeroed themselves or went back to default settings. No damage. Go figure.

 

[Bill Roosa]

An experiment

Since most of us have a mast and keel it would seem to me to be pretty ease to connect a very high resistance volt meter between the two and see the potential build up. Mr. Tesla apparently did such an experiment when in Colorado and said he could see the energy passing overhead. Certainly will not prevent a strike but could give an indication of one approaching (or not).

If that worked an enterprising young man could build a circuit that sounded an alarm when the potential "became dangerous", sell it to the uninformed and buy a bigger boat.

Thoughts?

 

[T37 Phil]

Lightning will do whatever it pleases, regardless of what we sailors do. The only thing that surprises me about lightning is that there aren't more strikes on sailboats.... My only close call with lightning was bizarre. I was crewing on an IP 38 and a line squall came up. Lightning hit the water about 25 ft off the bow -- but not the boat with a huge metal mast sticking up. Our hair stood on end. All the electronics zeroed themselves or went back to default settings. No damage. Go figure.

How deep was the water? I wonder what [below] ground features are in play that seem mysterious to us because we cannot see them.

Bill - I have a box just like that if you're in the market. It's also guaranteed to ease your back pain and toothaches!

 

[walt]

Bill, do you need a bigger boat than 40.5 foot?

We've been talking about electric fields between the sky and the water surface and that the surface charging basically "terminates" the field so that the water surface basically looks like ground. And.. that likely the presence of this field should "concern the hell out of you" as it likely indicates that the conditions for a strike may be building up.

I know a lot of people have experienced getting shocked on a sailboat or a popping sound from an arc happening somewhere on the boat. Ive personally had this happen to me five different times. Many years ago windsurfing, I got a single big shock from a nearby strike which ended up in a wipeout and wet suit soiling - but nothing more.

Here is what I think is happening with getting shocked on a sailboat and it all has to do with the electric field which is present just before (or during) a strike.

The main concept you have to buy here is that a conductor placed in an electric field will take on a single voltage potential at its mid point in the field. An insulator can have an electric field across it since current doesn't flow to equalize things. But if a conductor has a field across it - current will flow - since no current flow - the entire conductor takes on one voltage potential.

I drew up this little figure below to show what happens on a sailboat. In the example, the conductive mast mid point is higher in the electric field than the conductive person standing on deck. Since they have different "average" heights in the the electric field, both take on different voltage potentials. If the person were to touch the mast, there is 20K volts difference and the person will get shocked. Some charge will be transferred but its small since it is only discharging the capacitance (maybe 100 pf) between the person and the mast.

You could use a mechanism like this to tell when an electric field is present - but most boats already have something like this built in - ie, if you get shocked on the boat or hear a pop- pop- pop... you should be worrying.

 

[Jim Seamans]

Hey Warren

Are you sure it didn't zero out your brain...heheheh

 

[T37 Phil]

walt - Are you assuming air is a perfect insulator? Potential makes sense as a relative measure, that is, between two points in a field. If a conductor is placed in a field, the question becomes what is the field within the conductor (thereby determining the current). Isopotential within an [open circuit] conductor occurs due to charge redistribution, which is itself a current. In any case, static and static shocks always seemed peculiar to me, like getting something for nothing. The assumption that a long, straight conductor aligned parallel to a uniform field will take on a potential equal to the midpoint of the field seems less than certain to me. It calls into question the relative nature of potential and the 'history' of isolated/insulated objects and their potential (or total charge?). I'll have to ponder.

 

[walt]

I think non-ionized air is considered a very good insulator. You can have energy flow in air but it must be through electromagnetic waves (such as radio waves or light).

Something sort of interesting is that to initiate a breakdown in air, it takes about 3 million volts per meter of electrical potential. But in a formed lightning strike, this can be "two orders of magnitude less" which would only 30 thousand volts per meter. The reference below says the potential to maintain breakdown in a well developed lightning bolt can be as low as hundreds of volts per meter. Ill take this to mean that air can also be a dang good conductor when its sufficiently ionized and heated.

http://en.wikipedia.org/wiki/Lightning

The ambient electric fields required for lightning leader propagation can be one or two orders of magnitude (10−2) less than the electrical breakdown strength. The potential ("voltage") gradient inside a well-developed return-stroke channel is on the order of hundreds of volts per meter (V/m) due to intense channel ionization,

Regarding this

the question becomes what is the field within the conductor (thereby determining the current).

If there is no current flowing in a good conductor - the field across it is zero (ohms law). If your mast is insulated by air from any source of current, it will have zero volts across it - and in an electric field, will take on the single potential of its mid point in the field.

 

[zeehag]

i still say that crocs, kat and rubber hat is the only way to go --nothing attracts to crocs, there is no written history of a kat being struck by lightning, and a rubber hat might save the remnants of my brane from weather......


oh , yes, and a whole TEAM of guardian angels to watch over .....



but we didnt get hit!! we sailed thru it for days and we didnt get any thing thank the sea gods!!! was an adventure!!!! goood sailing, too!!!

 

[walt]

You have only 1/4 the worry that men do http://science.nasa.gov/science-news/science-at-nasa/1999/essd18jun99_1/

The stat Im having a hard time finding data on is that men which were struck were discovered with their fly down.

Maybe Im getting this mixed up..

 

[Ross]

My first wife's father swore that mules attract lightning and that dreaming of a black dog presaged a death in the family.

 

[Bill Roosa]

So Walt Why can't I...

attach a capacitor to a short stick with one lead grounded and one attached to the mast through a transistor switch. I could let the cap charge up then dump it to a battery (with a fancy circuit that does it rapidly and often) and have an all electric boat.

 

[FourPoints]

Since most of us have a mast and keel it would seem to me to be pretty ease to connect a very high resistance volt meter between the two and see the potential build up. Mr. Tesla apparently did such an experiment when in Colorado and said he could see the energy passing overhead. Certainly will not prevent a strike but could give an indication of one approaching (or not).

If that worked an enterprising young man could build a circuit that sounded an alarm when the potential "became dangerous", sell it to the uninformed and buy a bigger boat.

Thoughts?

This is actually a good idea, and something that I have been considering for the past year.

Last summer a storm unexpectedly changed course and instead of passing east 15-20 miles to my north, turned due south and came straight at me while at anchor off of Lloyd Point of Lloyd Neck, Long Island. When it was about 8 miles away I went up to the fore deck to check the anchor and noticed a humming sound similar to when you are standing under high voltage power lines. When I got near the standing rigging (about 18 inches or so) my hair started to stand on end, and when I was about 6-8 inches away, a strong tingling feeling all over my arms was felt.

Having flashbacks to peoples recounted tales of having their boats struck by lightning I recalled that people near the standing rigging often reported felling a tingling sensation from the standing rigging in the moments before the strike occurred (assuming they were near it). I reached out and touched the fore stay to make sure I wasn't imagining things, and received possibly the worst static shock I have ever experienced in my life.

I immediately told my GF to get below deck and to stay away from the chain plates or the compression post and I pulled the anchor up as fast as humanly possible, started the engine, and shoved the throttle to the limit.

My theory was that a charge was building around the boat, possibly coming through the lead keel, maybe the anchor, maybe both, and going up through the standing rigging (my mast is grounded to the keel) and building a highly charged mass of air around the boat, using the mast and rigging as a transmitter of sorts (earth science 101 teaches us that the lightning bolt usually starts at the ground and moves up to the cloud to equalize a charge imbalance between the ground and the clouds).

My theory was that I could reduce my risk of what was otherwise likely about to be an imminent lightning strike by A) quickly move away from the highly charged air mass that had been building around my boat while at anchor. and B) get as much air to flow over the mast and standing rigging as possible to dissipate the charge that had built up, and to do so across as wide of an area as possible to prevent another "hot zone" from forming around me that could give birth to a lightning strike.

I don't know about the humming sound as it was immediately drowned out by the sound of the engine, but the tingling feeling coming being near from the standing rigging started to fade within 30 seconds or so after getting the boat moving, and within 2-3 minutes it was completely gone, so I believe I analyzed the situation and reacted correctly, and most importantly, my boat did not get struck by lightning.

I'm certain that in that situation some sort of electrical potential monitor attached to the mast would have clearly given me a warning that the vessel was rapidly building a large charge, which was putting me at an extremely high risk of being struck in the very near future, and it would have done so long before I was able to notice the humming sound, or the tingling feeling from the standing rigging.