LIGHTNING (this time not hockey!)

[Steel Shootin']

I think I have few phobias. As a kid growing up in Florida, my passion was catching snakes; I especially had a passion for those in the Pit Viper family (Rattlesnakes, Copperheads, and Mocasins). Florida's only other venemous snake, the Coral, never interested me much. I figured with a Pit Viper I might at least survive.

At one point, at age 12, I had over twenty snakes, mostly of the benign species, such as Florida Kingsnakes, Yellow Rats, Red Rats, Bandid Water (horrible pets...they bite, and have sharp teeth), Hognose, Glass, Indigo (yes, I know protected), the occasional black racer I could catch-up with, and a couple of imports (Boa/Python).

So, between spearfishing and a history of snake hunting, I do not think I am prone to fear, except I have a single phobia: Lightning. The stuff just scares me to death. I'd rather be in almost any situation than in the middle of a lightning storm. This may come from being caught in the woods so many times as a youngster growing up in the Lightning capital of the world, and having it crash around me on many occassions. Oh yeah, and as a Paramedic I responded to a bad strike once, and saw first hand what it can do when it actually connects to a person.

Such a phobia comes into play when you love being on the water. There is something about being on the water that seems to make you such a target. It's like, there is nothing else out there for the lightning to hit, so you feel like a sitting duck. I spun a prop once 30 miles off the coast of North Captiva Pass while trying to out-run the Summer Storm from hell, and had to endure 45 minutes of incredible lightning and wind-gusts to 50 mph, but that is another story.

Articles on lightning always catch my attention, which is why the March/April 04 Issue of DAN's Magazine, Alert Diver, made it's way next to my crapper. Some interesting content, including:

A retired dive boat captain explained his rationale for sending divers into the water during a lightning storm: "Lightning striking the open water would be quickly diffused, but, if it hit the boat....the result would be fish sticks. Trying to outrun the storm would not have been any better, it might actually have been worse, given the electronic equipment on the boat and static charges building up on metallic surfaces."

A researcher studying lightning around the water said that a diver suspended in water does not constitute a target. That would be different if the diver stuck his head out of the water. If lightning posed a great threat to the water and marine life, many fish would be killed each time lightning struck bodies of water.

Another researcher reported diving near the surface of a lake during a thunderstorm. Lightning flashes were visible and heavy downpour produced raindrops at the surface. The divers in the group did not surface, using instead their compasses to navigate themselves to the nearest shore, traveling until they reached the exit point. The researcher contended that if divers have enough air to remain to remain underwater, that option would be better than swimming at the surface. He also concluded that swimming along the shore seemed safer than swimming at the surface in the middle of the lake.

Given that water bodies are usually cooler than land during summer, less lightning occurs over water than over land....

Interesting observations, but anyone who has watched weather reports with radar images for the Tampa Bay area of Florida has seen that lightning strikes plenty out over water. Also, even if it is derived that your safer in the water, don't forget the helmsman, who is at greater danger in spite of the fact that you can hang at 30 ft for the next hour.

Anyone have any expertise, or anecdotal information?! Good topic as we head into the Summer storm season.

[Doc]

I was diving in a pool one day with my brother when I noticed rain at the surface; before we got out we got the shock of our lives... felt like our whole bodies convulsing. We later learned the bolt struck a satellite dish a few yards from the pool.

We quickly departed; and the only after effect was a pretty bad headache and, believe it or not, some loose teeth that tightened up over a day or so.

When lightnig strikes; all the surplus electrons that collect from the storm gather up and discharge either from the ground to sky or sky to ground, eminating from or to a single point; usually the highest object around.

If you are in the vicinity of a stike; your entire body will then either recieve or provide its excess electons; giving quite a shock.

The way people are hurt during strikes is that you become part of the circuit; and the entire bolt uses your body as part of the electic pathway; usually travelling through the tissue with least resistance; the nerves, spine, and brain. It also leaves nasty entrance and exit burns, for example on the bottom of the foot and top of the head. The heart is often part of this path; which can cause arrythmias.

If you are in the water with your head sticking out; that could be real bad... If I came up during a storm, I would try to wait it out underwater with out a doubt; but I would be pretty hesitant to actually jump on in.

[PatMyGreen]

I can completely relate to that fear Scott, I have had two indirect strikes hit me (over the phone and by standing in a flooded street when a telephone pole 50 yrds away got hit) and my Dad has always been pretty scared of the stuff as well. He is a Pro Golfer and has an incredable amount of stories of lightning doing crazy stuff that defied what most people are told it will always do. But the point I am going to make is that while statisticaly lightning strikes the tallest objects around, it goes where ever the charge is stongest which isn't always the tallest object present. A girl from my High School was struck and killed in the middle of a court-yard inclosed by tall buildings and with trees near by. The stroke arced from the girl to the tree and was witnessd by several other students. I'm told it was pretty gruesome but she likely never knew what happened.
There were plenty of tall things very near by but she still took it full force, not that this is more likely than it striking a tall object just a little bit from my experience that makes me feel like lightning is pretty much random when it comes to humans. My two incidents though were both from the energy dispersing after it hit tall objects.
Does anyone have any stories to relate about getting a zap while in the shower? My Mom has a huge fear of this do to a story she heard growing up, seems like there could be some truth to it.

More to the point of this thread, I am curious about how to protect my boat from a strike. I have heard that having a grounded flag pole nearby I a good defensive measure, are there any others or do you just get really good insurance ang hope you don't need it?

[FredT]

It's not a simple matter, but there are some simple rules you can follow if grounding a boat, or anything else. Following them may not be the least expensive way to get the job done, but it can keep you and your electrical equipment alive. The more you know the less expensive the installation can become.

1. Metallic masts on a conductive hull should be grounded to a bare metal plate with an exposed area of at least 4 sq Ft with conductors of 2/0 wire size or larger. Braided conductors are best, followed by stranded.

2. Lightning is a surface follower so bare wire is best, and the reduced surface of a solid wire means a solid conductor size needs to be 250 MCM or better. The mast firmly welded to the hull with a straight path to the keel also firmly welded also makes an excellent air terminal.

3. The effective protection volume of each air terminal can be visualised by rolling a 150' diameter sphere to the terminal so the sphere touches the top of the terminal, and then rotating the sphere around the terminal. The area between a line going directly to ground from the air terminal to the closesest surface of the sphere is protected. Things outside that volume are still liable to take a hit or side strike.

4. ALWAYS provide at least two paths to ground, both able to carry the entire strike. At no place in the path should thesurface of the conductor bend at greater than an 8" radius.

5. On a fiberglass hull the passengers are pretty well insulated by the hull. The outboards aren't. Stay WELL CLEAR of the outboards and low in the hull if lightning is in the area. The EMP produced by a nearby hit is enough to induce internal currents and voltages sufficient to let the magic smoke out of most electronics on an insulated hull. Those same instruments in a grounded faraday cage (conductive enclosure) will usually survive survive.

6. Divers in SEA water are the undesireable path as your conducivity is considerably less than the surrounding water. By the same token a diver in FRESH water IS THE CONDUCTOR. Lightning strikes on lakes ground at the bottom, not the surface. It just finds a reasonable path through the water along the way. I would be especially nervous during a thunderstorm if diving on a metal hulled wreck in fresh water.

7. There are credible accounts of divers hit in seawater where the strike hit and burned holes in the aluminum tank with no damage to the diver beyond needing a new set of shorts. The tank channeled the current past the diver.

8. A LOT more information is available from LPI. This is the Lightning Protection Institute and is the accepted "expert" in the field, much as the NFPA is the accepted expert in fire protection. In fact the sections in the NFPA and NEC that deal with lightning are lifted directly from parts of the LPI documentation. The data isn't cheap, but it's worth twice the cost.

[OceanEd]

Pat:

I agree with you that it is not always the tallest object that gets hit. My boat took a direct hit at the top of the mast and we were in a small hurricane hole with 8 other sailboats, all with taller masts, and cliffs surrounding us that were taller than any mast. It caused over $16,000 worth of damage. I

It is not just the direct path that the lightning takes that creates damage. There can be "side flashes" that can cause damage for some distance away. When we were hit it blew out a computer on a boat next to us on one side and the diodes on a windgenerator on a boat farther away from us.

It is amazing going through the boat and finding what survived and what did not. Sometimes it makes no sense. Insurance agents that are your friend will tell you that in a lightning strike you should declare ALL electronic equipment as defective because stuff that is still working can be severely weakened and will not last long.

We had lasted 15 years on the boat and went through many lightning storms and thought it couldn't happen to us until 1995 when we were hit. Even spent one hurricane season up the Rio Dulce River in Guatemala and one cruising boat almost every two weeks was being hit by lightning up there. So we thought we were pretty safe. Wrong.

Ever since, my dog goes ballistic whenever there is a lightning storm and I have to hold him to keep him from shaking too much.

Everything I have studied since seems to be divided into two camps. Those who strongly recommend that you ground the boat and bond all the thru hulls (I am talking fiberglass boats) and those that recommend that you do not. Very interesting to hear FredT.

FredT: I was told by some "experts" to even put fuses in the negative wires leading to all my electronics because sometimes the force will come back up the black wires from the battery. Any idea? From what I understand, even with good grounding the side flashes will pretty much take out anything on a boat that it wants to take out.

Scott & Pat: I am with you. I think the most helpless feeling in the world is being on a boat in the middle of a lightning storm. You start to realize why our ancestors lived in caves.

The diving organizations I belong to such as PADI and NAUI require that you must get student divers out of the water if there is any lightning. There is no differentation between salt or fresh, pools or open water. That is because the insurance companies require it in their policies. For years I have tried to ask everyone I know whether or not it would be safer to stay in the water and no one has been able to give me an answer until now.

Extremely interesting about the difference between fresh and salt water.

I hope more people will join in here.

[lionfish]

Some friends and i got caught in a thunderstorm in the middle of the sound. we watched a bayliner run by us at full speed with all the antennas up and people waving as they went by. about five minutes later we come up on the boat, dead in the water, antennas melted all the way to the mounts and one passenger doing the technicolor yawn over the gunnel(apparently she had her hand on the baitwell).

There was a funky smell(not the yawn) of ozone and every electronic device, including the cell phone in one passengers pocket, was fried. the motors electronics, radios even the electronic bilge pumps were dead.

it's my understanding that a fuse will not protect electronics from lightning emp, the duration is so short and the pulse so powerfull that once a circuit is made the power will arc across even an open fuse.


fwiw

Leo

[fishspearit]

I've always been interested by the debate over bonded vs. unbonded boats for lightning protection. A well bonded boat provides a nice path for the current to go overboard, theoreticly lowering the damage to the boat. But since lightning follows the easiest path to ground, isn't that making your boat more attractive for a strike? The sailboat that I lived on for years was built in 1962, before it was considered imperative to bond everything. The two masts were deck stepped, and none of the bronze through hulls were bonded. I watched a lot of boats around me, with bonded hulls, get struck. I also know of a high percentage of boats that have been struck multiple times, like there's something more than just bad luck causing it.
One thing that I read a while back, and I'm not sure how true it is, (the post above would tend to dispute it) is that an ionic charge builds up before the strike, the result being that boats moving through the water are less likely to be hit than boats at rest. The idea being that a moving boat is "shedding ions" as the water flows past it. Most of the hits that I know of have been on boats at rest in the water, but it may just be that that is where most boats spend most of their time.

[FredT]

Originally posted by OceanEd


FredT: I was told by some "experts" to even put fuses in the negative wires leading to all my electronics because sometimes the force will come back up the black wires from the battery. Any idea? From what I understand, even with good grounding the side flashes will pretty much take out anything on a boat that it wants to take out.



Side flashes are one item, the EMP is another.

The EMP is strong enough that it induces a current even in equipment that is disconnected. That is why the secondary enclosure protects the electronics. It grounds out the EMP before it can get to your important stuff. The EMP is there even on a perfectly bonded system. Basicly the lightning path is one conductor of a transformer, ALL the other wiring on the boat is the other side, including the traces on an unshielded PC board! CMOS chips die at about 50V, the newer stuff dies even faster so it doesn't take much of an induced voltage to let the magic smoke out. Considering the strike is often a few thousand amps at tens of thousands of volts almost any completed current loop will let the magic smoke of of most logic chips even with a very short 1:1 ratio transformer

A properly grounded and regularly inspected system WILL NOT HAVE SIDE FLASHES! Bend a conductor too tight or have a significant burr on the outside of a conductor and you get them back again. Side flashes indicate you have not enough ground conductor or have a high resistance (say ~.0001 ohm) in the ground path. Sharp bends and burrs induce an inductance load that can cause the surface following plasma to jump off the surface. This inductance load is why it's VERY rare for a stike to jump to a higher surface

Fuses won't normally help anything but your sense of well being. Zeiner Diodes might if the downside is well bonded.

FT

[OceanEd]

FT:

Wish I had talked to you before my stuff got fried.

[Letrappes]

About what Pat was saying. I was at the same high school the day that girl got hit. A friend's little brother was walking with her and barely missed getting killed with her. We had to take him home after he was looked at and he was blinded for most of the rest of the day.

About lightning: Lightning has just travelled over a mile through nearly the worst conductor possible. I doubt it will even notice anything you do to your boat to try and reroute the multi-million joule current that accompanies it. The only thing I think you can do is to make the guys boat next to yours look like a better conductor.

[SpearDiverTampa]

It sounds like even when lightning hits a boat, the passengers usually survive. I would be more worried(especially when drift diving) about being under and the boat being struck by lightning and becoming disabled and not able to pick me up.

[BluewaterRocket]

When I find myself on open water in the midst of a hellacious thunderstorm....... I usually pray.

[gumshoe]

I was in a boat that got hit. It sucked.

Shortened story, bass fishing, the guy I was with was running the trolling motor and got struck. The point of entry was - none other than the little fishing hook that you clip on the bill of your ball cap. The insurance folks said that it looked like it exited out of the transducer at the back of the boat. Other than being scared SHIATLESS, we were pretty much unharmed. All electronics on the boat were fried.

The storm was at least 5 - 6 miles away, skies were darkening, but did not seem too bad, freshwater open lake.

[greyface]

A couple of my brother's friends were cast netting shrimp at Cumberlin Island, Ga., in a 16' boat. One guy was shaking out his net, the other had just cast his, when the strike occured. Blew them both out of the boat, and out of their shoes. Killed the guy with the net in the water, the other was stunned, but ok. Tragic story.

[PatMyGreen]

Back to lightning stories, it was a few (10 or so maybe more) years ago but remember the news reports of 11 people being killed here in PC in their boats (power) by a strike. It was 2 boats that were at rest by Shell Island. One was at anchor and I believe the other was tied to the first. I don't remember which they figured out was struck first but the bolt jumped to the other boat too and everyone on board both boats died. My Mom completely freaked anytime we talked about being around water in a storm after that.

[jeffe]

Talk about following the path of least resistance !
When dismantling a sprinkling system in my west pasture I leaned a sprinkler against this large white Oak tree in the back yard. It is not hard to follow the path of the lightning strike. There is a permanent mark on the tree. When it jumped to the brass sprinkler head it left no mark as it traveled down the metal pipe.
Happened the last week of july this year, 2004. I am glad I was not in the tool shed in the photo, the door is 4 feet away from the strike point.

[jeffe]

The pipe makes a bend and had a brass fitting on the end. But the lightning didnt go to ground when it left the fitting, it went to a tree root.

[Spearo_Fla]

Before I shed my tanks back in 1997 I use to take some underwater photos. One day I was down and a friend above me in about 25 ft of water snapping pics of Coral banded Shrimp when I noticed my flash went off when I wasn't even near the button. Since I was almost out of air I returned to the surface and my partner was back on the boat. After swimming to the boat my partner was washing himself with the freshwater hose and I asked him what was up? He said didn't I see it? I said see what? He said a lightning bolt hit the water about 50 ft to the south of my position. I then realized that flash I saw was not my camera flash!