Lightning Strike

[Wynand N]

Hi

A few days ago a golfer and his son were killed by a lightning strike after taking shelter under a verandah on the golf course during a thunder storm.

This brings the following to my mind. How safe are our boats on the open blue during a thunder storm?
Are there any special procedures a designer or builder can incorporate into the boat during construction, over and above the ABYC recommendations, to make it safer during a strike?

Lastly, in the event of Zeus being in a bad mood, and decides to zap your boat with a bolt, is it safer to be inside or outside the boat

[DGreenwood]

Inside, making yourself as small as possible. Crouched over your feet with them on top of an insulator like a berth cushion or the like.

In the case of sail boats, the rig, and its attendant rigging wire, afford some protection.
There is a lot of hokey garbage out there that is supposed to help reduce risk but most of it is snakeoil.
Much has been learned recently about lightning and some of it applies to yachtsmen.
One of my most recent revalations about it came from a surveyer in Florida (the lightning capital of the yachting world) She claims that those sintered copper Dyna-plates go off like hand grenades and blow large holes in boats. Interesting if true.
I believe grounding the rig to water helps discharge the static that builds up and puts out the leader that attracts the massive voltage dump that is a lighting bolt. I'm sure some others have a different opinion.
If you think you are going to put a wire large enough to carry the current of a full strike to the water,you are dreaming. That would be like trying to connect a garden hose to a six inch fire hose under full pressure.

[SeaDrive]

Originally Posted by DGreenwood

I believe grounding the rig to water helps discharge the static that builds up and puts out the leader that attracts the massive voltage dump that is a lighting bolt. I'm sure some others have a different opinion.

I believe the opposite: gounding the rig makes it easier for charge in the sea to be climb to the top of the mast and increases the charge there.

[Robert Gainer]

Try this site for some information. http://www.cdc.gov/nasd/docs/d000001...7/d000007.html

In the past I have put a chain in the water that was atatched to the backstay. But I have never been hit, at least not yet.

[Skippy]

Don't even think about trying to avoid a strike based on static charge.
What the ground wire does is make sure the current goes through the metal instead of you.
The mast is your lightning rod, which must be grounded.

[DGreenwood]

I knew when I answered the question that there would be a flurry of opinions. This is a contentious issue to say the least. I also must say there are not many topics that that are riddled with more wives tales and snake oil cures.
If you follow the science, it tells a much different story than popular opinion. Now I am not saying I understand it by any stretch, but anyone who has cut and dry answers is BSing because it is a very baffling science and there is still much to learn.
The boats that I have been on that had been hit made it clear that there is no controlling the surge of power. It manifest itself in many peculiar ways. Blasting out through the FRP in places you would never expect. Sparing electronics that had antennae and frying hand held calculators in a drawer.
You see in my twenties I did some rescue work in Yosemite Park. I helped with a body carry out of two poor souls who had made the mistake of hiding from a high altitude electrical storm in a cave. Bad move...I can't blame them...I have wittnesed many of the same type of storm in my mountaineering days and they are hairraising..literaly.
I swore, after seeing that absolutely horrific scene that I would not let that happen to me. Easier said than achieved.
Later in my life I was on a boat up the tropical river that takes you to the town of Golfito, Costa Rica. We were beseiged by an electrical storm for around 20 minutes the likes of which I have never seen or heard of since. Hits only seconds apart and many within 100s of yards.Two of the guys on the crew were sobbing. Now I have spent time in Florida in the summer and seen the terror that is put upon those poor seafarers, but this baby was insane. "That's it" I said I have to figure out how to protect myself. Well, again, easier said than achieved.
Since that day I have tried to get a handle on this stuff but to no real satisfaction. Yeah I've read the stuff that NOAA, NASA, U of M, U of O, UCB, Cal Tech etc. etc. has written on it but it is till unclear to me how to protect ones self. And this is embarrassing because it is one of things that is part of my job. When installing systems on boats I am asked continually what we should do to protect the boat and its occupants. I am tempted to shrug my shoulders but I have to give them some confidence and tell them that we will do the best based on what IS known about it. And that is all that I can do. So if any of you have some solid info based on real science from a real lab I'd love to hear about it. Cause I am confused.

[gonzo]

I've done many surveys of boats hit by lightning for insurance companies. Grounding helps prevent major damage to the boat and crew. For example boats with no dedicated ground will have the current go through fuel tanks causing an explosion. Sometimes it exits through the fiberglass bottom filling it with holes and sinking the boat. Electronics can be damaged with a small voltage spike, but good grounding can prevent disasters.

[FAST FRED]

When just anchored I use a 2ft sq copper plate , lowered over the side and attached to the outboard upper shroud.Under way we trail a chain.

Hopefully this would give the jolt an easy path to the sea , with out having the BOAT in line with the current path.

So far so good ,CLOSE! side strike had no damage to any electricals.

The boat does use a sintered bronze plate , but only as radio ground, and is not internaly bonded .

No problem with pink seacocks or prop in 30 years afloat.



FAST FRED

[Skippy]

Originally Posted by DGreenwood

.. anyone who has cut and dry answers is BSing because it is a very baffling science ...

DG, there's nothing baffling about the basic principles. Electric current will always follow the path of least resistance, and there's nothing you can do to prevent a lightning strike in a rainstorm. Sailing in bad weather with an ungrounded mast is suicidal, regardless of what you do to control "static charge".

If you're talking about guarantees of safety, for instance by commercial products, then that would be BS. But no anecdotal stories about unlikely individual events change the basic facts. A big tall mast is an excellent conductor, and will always be the highest object for miles around. A heavy-duty grounding wire immersed in the water will have overwhelming odds of taking the majority of the current, drastically increasing your chances of survival. Without it, your body is one of the best conducting materials on any nonmetalic boat.

Originally Posted by DGreenwood

I believe grounding the rig to water helps discharge the static that builds up and puts out the leader that attracts the massive voltage dump that is a lighting bolt. ... If you think you are going to put a wire large enough to carry the current of a full strike to the water,you are dreaming. That would be like trying to connect a garden hose to a six inch fire hose under full pressure.

The grounding wire definately does not reduce the chances of a strike, it increases the chances by offering a low-resistance path from the air to ground. What it does do is shunt current away from the rest of the boat (or other structure) if and when the strike occurs.
5/8" metal rod is is a standard size for land-based applications.


A few fun/interesting/useful facts:
The lightning rod was invented by Benjamin Franklin.
Lightning rods are called "air terminals" nowadays.

http://www.lightningsafety.com/nlsi_lhm/lpts.html
Lightning is a capricious, random and unpredictable event.
Its' physical characteristics include current levels sometimes in excess of 400 kA,
temperatures to 50,000 degrees F., and speeds approaching one third the speed of light.
Globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second.
Air terminal design and performance is a controversial and unresolved issue.
Commercial claims of the "elimination" of lightning deserve a skeptical reception.
The marketplace abounds with exaggerated claims of product perfection.

http://lightningsafety.com/nlsi_lhm/InstallRods.html
If it sounds too good to be true - guess what - it is !

http://lightningsafety.com/nlsi_lhm/conventionalLPT.pdf
The government’s experience with lightning protection dates from even earlier, as also indicated by Viemeister:
"Do modern lightning rods protect a building? When properly installed, lightning rods can provide virtual immunity from direct lightning strokes. The Washington Monument was struck and damaged before rods were installed in 1885. Since that time, it has been struck innumerable times without injury.”

Literature based on further, more recent government statistics also bear out the effectiveness of lightning protection systems:
“A survey by [Office of the Chief of] Ordinance [U.S. Army] for the period from 1944 through 1948 shows the following: a. Protected structures were struck 330 times; damage negligible. b. Unprotected structures were struck 52 times; damage exceeded $130,000.”

9.0 Summary of Literature and Theoretical Results
Review of the key literature, as presented here, leads to the overwhelming conclusion that lightning protection systems have been intensively studied and have been proven effective many times over in the past 250 years.

11.2 Conclusions
The conclusions of the Federal Interagency Lightning Protection User Group are:
That Franklin, or conventional, lightning protection systems as specified by NFPA 780 are highly effective in preventing lightning damage.


http://www.marinelightning.com/science.htm
Since there is no scientifically proven method to repel it, the fundamental problem in yacht lightning protection is how to deal with lightning when it strikes. Where the lightning channel attaches to a boat is determined by the geometry of topside conductors on the boat and the location of the downward-going stepped leader relative to the boat.

Any liveaboard yacht requires a high standard of protection to ensure crew safety and hull integrity. Further, any yacht that ventures into blue water needs to be self sustaining after a strike. Larger sailboats have the advantages that stainless rod rigging can be used as down conductors and a large interior volume means that the lightning protection system can be routed away from living quarters. However, complex control systems, dispersed electronics sensors, and carbon fiber or metal reinforcing means many conductors, each being a potential source for a sideflash. While immersed conductors such as propellors, bronze seacocks, and metal ballast have the potential to be incorporated into the grounding system, doing so raises the risk of corrosion and their grounding effectiveness is compromised if the surfaces are painted or covered with fiberglass. Also, dezincification of bronze through-hulls leaves them porous and weak and unsuitable for lightning grounding. Judicious placement of grounding electrodes is vital to ensure that the only lightning exit points are those that are planned.

http://www.forespar.com/resources/ti...Protection.htm
In an effort to continue to ground, a strike to your masthead may arc from a shroud chain plate to the water, leaving a burn mark down the side of your boat. Or, worse yet, if the path to ground is through your keel stepped ungrounded mast, lightning may burn through the bottom of your boat. At least any resulting fire is extinguished when the boat sinks.
One of the scariest places to be during an electrical storm is in a boat. However, if you take the precautions of bonding and grounding the boat, installing surge suppressors on your electrical wiring, and installing static dissipaters on the charge accumulation points of your boat, you should be able to substantially reduce lightning problems.

http://www.lpbinc.com/TechSupport/Om...apers/LP1.html
The most important principle of lightning protection, as most of already know, is to provide the best, lowest impedance local ground connection possible as close to the tower base as possible.


http://www.rainmaster.com/lightning.htm
Necessity of a ground system
In order to neutralize the harmful transient energy, it must be returned to earth ground before the harmful energy can enter the equipment. The protection components incorporated in any manufacturers' controllers rely completely on the external ground path provided during the installation of the controller. Therefore, it is absolutely imperative that a good grounding system be installed. The ground system will consist of one or more properly installed ground rods connected through appropriate means to the controller.

Characterization of the ground system: A single 5/8th inch diameter by 8-foot copper clad ground rod, properly installed, is usually sufficient.


http://www.ametsoc.org/policy/lightn...tems_2002.html
It is well established that properly installed and maintained conventional structural lightning protection systems (LPS) based on Franklin's methods significantly decrease lightning damage. However, the installation of such a system in conformance with NFPA 780 is not a simple matter. Proper procedures must be followed for the protection to be effective. Non-experts need guidance as provided by an appropriate standard which, in the United States, is contained in NFPA 780.


http://www.foremostboaters.com/safety/lightning.htm
When lightning does strike, it will most often strike the highest object in the immediate area. On a body of water, that highest object is a boat. Once it strikes the boat, the electrical charge is going to take the most direct route to the water where the electrical charge will dissipate in all directions.
There is no such thing as lightning-proof boats, only lightning-protected boats. All-metal ships are rarely damaged and injuries or deaths are uncommon. These ships are frequently struck, but the high conductivity of the large quantities of metal, with hundreds of square yards of hull in direct contact with the water, causes rapid dissipation of the electrical charge.
Today's small fiberglass boats, especially sailboats, are particularly vulnerable to lightning strikes since any projection above the flat surface of the water acts as a potential lightning rod.
Lightning protection systems do not prevent lightning strikes. They may, in fact, increase the possibility of the boat being struck. The purpose of lightning protection is to reduce the damage to the boat and the possibility of injuries or death to the passengers from a lightning strike.


NOAA Lightning Safety Web Page (with lots of lightning photos)


Hoping everyone has a safe and happy new year.

[DGreenwood]

Skippy
Glad to see you've got a handle on it. Now that you have it all worked out you are destined to be very weathy indeed. There are some insurance companies in Florida who would be happy to pay plenty for your consultation time. You would save them millions every year.

Sorry, for being smartass, but it is not quite so simple as a grounding wire to the water. Dissipating a charge of 400kA is a little tougher than that.
And there are some well credentialed sorts who think that it is possible to dissipate the static that attracts the charge in the first place. Although that may be witchcraft as well?
As long as you are reading info put out by people that are selling something, you will believe that is a simple matter to protect yourself.

Quoted from one of the sites you have pointed out above:
"In particular, Thomson noted that hull damage to sailboats struck in fresh water was so extensive, even when the boat was well grounded, that multiple grounding surfaces were needed over an extensive underwater area, much more than the one square foot ground plate quoted in the code. This requirement is very difficult to fulfill in practice."
And the quotes saying that steel boats are rarely damaged is ...well ...bunk. Ship, aircraft and metal buildings all take a beating as a result of lightning.
This is from the NOAA site quoting some Air Force and NASA guys:
"One of our best tools is radar.We've developed several rules-of-thumb for using radar reflectivity intensity, depth, and duration versus key temperature levels to predict the start of In-Cloud and Cloud-Ground lightning. The 45 WS then uses these forecasts to issue two tiers of lightning advisories. A Phase-I advisory is issued when lightning is expected within 5 nautical miles of 13 points of operational interest with a desired lead-time of 30 min. A Phase-2 is issued when lightning is imminent or occurring within 5 nautical miles. This two tiered system works so well, the US Air Force adopted it for use Air Force-wide in 1997."

It turns out ( and I can verify this from many Nautical miles of sea time) that the best tool you have is your eyes, your understanding of the movement of lightning storms and Radar. If you can avoid being in them, you stand a chance. Otherwise you are pretty much at their mercy. Run all the big fat wires you want...it may help ...but it is no guarantee, not even a "sort of a guarantee" that you will come out OK.
I finally learned a few things about judging their path and avoiding them...by no means a foolproof method, but the best I have to work with.

[Skippy]

Originally Posted by DGreenwood

... there are some well credentialed sorts who think that it is possible to dissipate the static that attracts the charge in the first place. Although that may be witchcraft as well?

Sounds like it. I would have to see VERY convincing evidence to believe otherwise.

Originally Posted by DGreenwood

Sorry, for being smartass, but it is not quite so simple as a grounding wire to the water.
Run all the big fat wires you want...it may help ...but it is no guarantee, not even a "sort of a guarantee" that you will come out OK.

DG, you and I are talking about two different things. Nothing is a guarantee. Not grounding wires, not even radar and avoidance methods.
I never said anything was simple or a "sort of guarantee". My only point has been that having no protection at all is foolish. The mast and stays must be grounded to reduce the risks as much as possible.

Originally Posted by Skippy

What the ground wire does is make sure the current goes through the metal instead of you.

Looking back at my original post, I would agree the phrase "make sure" is overstated. "maximize the chances" and "most of the current" would be more accurate.

[PAR]

I've been aboard two boats struck, one small (24' sail) and the other medium (48' sail) The 48' ketch had the typical lighting protection seen on most serious cruisers and the bolt was sent to ground through the large cable, though there was some minor burning, little damage. The 24'er took a hit at the mast top, traveled down to the step where it jumped to the pivot bolt in the centerboard (completely incased in 'glass) and blew several holes in the bottom and board case. We just made it back to shore after awaking to a sinking boat and not unlike a real bad hangover kind of fog our heads were in.

Frankly, here in Florida, it's a real concern and NASA has the biggest and best information on the subject available anywhere. A lighting strike on the launch facilities or a spacecraft on it's way is a fear they've strongly addressed. There isn't any place on earth that has as much nor as inventive lighting protection then the "Cape". I use to have the address, but it's been years. A search on NASA's site should yield some usable information, for those interested in the facts, the equipment and techniques need for protection.

There's a lot of hype and shear foolishness in regard to this issue. Get the real story from the folks that have the well funded mandate towards several solutions, most of which can adapt to the marine environment.

[DGreenwood]

Skippy
Sorry...I'm being too literal.
I install equipment on cruising boats and the disclaimer is always right there in everything I say to a customer. These days you can't be careful enough what you say.
As PARs story has pointed out, sometimes the stuff works.

A friend of mine had his trimaran in Florida. Big fat ground chain into the water. Blew a zillion little holes in the bottom. He fixed it. Better ground, different spot, exact same thing again.
I picked a up a boat in Jacksonville Fl. A few weeks before I arrive to deliver it, 45k worth of electronics gets fried. I fix it... new wires to keel, not toy wire either. We are talking four seperate legs of 0000 gauge wire to seperate chain plates. Different place, BAM...all fried again. Burn marks all over interior. I can keep going on with these kinds of stories.
Fortunately the crew is somewhat safe if they are not touching the rig or any potential current carriers.
The NASA site is a good one, but they even point out the safest is to stay away from them. Kind of tough to do in Florida though.

[Skippy]

Originally Posted by DGreenwood

1. These days you can't be careful enough what you say.
2. Big fat ground chain into the water. Blew a zillion little holes in the bottom.
3. The NASA site is a good one, ...

1. That's true.

2. Sounds frustrating. Of course, chains are designed for mechanical strength, not conductivity. As the current gets into each link, it can cross the point of contact with the next link, which is not nearly as good as going through the solid material of the link itself. And the current can also cross where the link touches the hull, which is apparently an attractive alternative.

I would expect a cable to conduct better, although it would also rust faster. What about a whole set of solid conductors embedded vertically in the sides of the hull terminating in plates below the waterline, one for each stay or shroud, and a bigger one somewhere for the mast? That way you have four or five garden hoses taking the flow from the fire hose. And a couple/few more emergency conductors to hang overboard when necessary. Now you're up to almost 10 garden hoses.

The trimaran would be flying one of the floats, so maybe they would have to have tails or something. Also, one page somewhere mentioned that rod rigging conducts well.

3. In case anyone is interested, NASA's main lightning section is here:
http://thunder.msfc.nasa.gov
I didn't see much there about protection systems.
But there is some in KSC [Kennedy Space Center] Fact Sheet "Lightning and the Space Program":
http://www-pao.ksc.nasa.gov/kscpao/n...t/lightnin.htm

One section, for example, is Protection at the Pad:
http://www-pao.ksc.nasa.gov/kscpao/n...ghtningpad.htm
An 80-foot fiberglass mast on top of the Fixed Service Structure at each pad is the most visible means of protecting the structure itself, the Shuttle while it is on the pad, and the enclosed launch equipment. The mast supports a 1-inch stainless steel cable that runs over its top. This cable stretches 1,000 feet in two directions to where each end is anchored and grounded. Its appearance is similar to that of a suspension bridge tower and its supporting cables. A 4-foot-high lightning rod on top of the mast is connected to the cable.
___

NASA and others have links to the National Lightning Safety Institute (NLSI).
This is a discussion that debunks hyped-up claims:
http://www.lightningsafety.com/nlsi_lhm/magic.pdf

NASA decided to protect the Space Shuttle with a wire above the Shuttle to act as a preferential strike point for lightning.
There are many documented incidences of lightning striking the overhead wire, protecting the Shuttle as designed.

[How's this for a fun job???]
At Langmuir Laboratory ... We have a specially-built instrumentation shelter (called Kiva II) ... we bring lightning to our instrumentation by triggering it - we shoot a small rocket trailing a grounded wire into an active thunderstorm to do this. On many occasions I, as well as other researchers and observers, have been inside Kiva II when it has been struck by lightning, with the lightning terminating on a current-measuring shunt on the top of Kiva II, about two feet above our heads. To prevent the currents from a direct lightning strike from entering Kiva II, it was constructed of 1/4” steel, ...

The principles of traditional lightning protection are basic -
1) provide preferential strikes point for lightning (an array of conductors higher than the objects being protected), a good grounding system, and conductors between the two to conduct the damaging current from a lightning discharge away from the structure to be protected; and
2) provide appropriate transient protection on power and signal wires entering the structure to protect equipment and personnel from the effects of induced lightning currents.
___

NLSI has a few references here:
http://www.lightningsafety.com/nlsi_pls/boating.html

This is the main one:
An excellent website on the subject that we recommend is: <http://www.cdc.gov/niosh/nasd/docs/as04800.html>
[That link doesn't work, but this is on the same site:]
web page: http://www.cdc.gov/nasd/docs/d000001...7/d000007.html
or pdf file: http://www.cdc.gov/nasd/docs/d000001...07/d000007.pdf

[Note these are EXCERPTS ONLY. And there's also info on electronics.]

LIGHTNING-PROTECTED BOATS
There is no such thing as lightning-proof boats, only lightning-protected boats. All-metal ships are rarely damaged, and injuries or deaths are uncommon. These ships are frequently struck, but the high conductivity of the large quantities of metal, with hundreds of square yards of hull in direct contact with the water, causes rapid dissipation of the electrical charge.

LIGHTNING PROTECTION SYSTEM
The major components of a lightning protection system for a boat are an air terminal, main conductor, and a ground plate. Secondary components are secondary conductors, lightning arrestors, lightning protective gaps, and connectors (see Figure 5).
The mast, if constructed of conductive material, a conductor securely fastened to the mast and extending six inches above the mast and terminating in a receiving point, or a radio antenna can serve as the air terminal.
The main conductor carries the electrical current to the ground. Flexible, insulated compact-stranded, concentric-lay-stranded or solid copper ribbon (20- gauge minimum) should be used as the main conductor.
The ground plate, and that portion of the conductor in contact with the water, should be copper, monel or navel bronze. Other metals are too corrosive. The secondary conductors ground major metal components of the boat to the main conductor. However, the engine should be grounded directly to the ground plate.
Sailboats with portable masts, or those with the mast mounted on the cabin roof, are particularly vulnerable as they are usually the least protected as far as grounding or bonding is concerned.

LIGHTNING PROTECTION CODE
The National Fire Protection Association, Lightning Protection Code, suggests a number of ways in which the boater can protect his boat and minimize damage if the boat is struck or is in the vicinity of a lightning strike. These suggestions are summarized below:
A lightning protective mast will generally divert a direct lightning strike within a cone-shaped radius two times the height of the mast. Therefore, the mast must be of sufficient height to place all parts of the boat within this cone-shaped zone of protection
To provide adequate protection, the entire circuit from the top of the mast to the "water" ground should have a minimum conductivity equivalent to a No. 8 AWG copper conductor. If a copper cable is used, the individual strands should be no less than No. 17 AWG. Copper metal or strips should be a minimum of No. 20 AWG.
On sailboats, all masts, shrouds, stays, preventors, sail tracks and continuous metallic tracks on the mast or boom should be interconnected (bonded) and grounded.

[Wynand N]

Hi

Thanks for the input this far, especially to DGreenwood and Skippy for their informative debat on the subject.

Sounds to me the best prevention is not to go sailing....

Originally Posted by Skippy

LIGHTNING-PROTECTED BOATS
There is no such thing as lightning-proof boats, only lightning-protected boats. All-metal ships are rarely damaged, and injuries or deaths are uncommon. These ships are frequently struck, but the high conductivity of the large quantities of metal, with hundreds of square yards of hull in direct contact with the water, causes rapid dissipation of the electrical charge.

....or at least do it in a steel hull, or so it appears.

Then again as a sideline, on land they say the best place to be in a thunderstorm is your car.
Well, a few months ago is was widely reported in the press of a woman who had her car striked by a lightning bolt. The damage to the car was substantial. All four tires (steelbelt radials) blown apart, alu rims damaged, side mirrors blown off, arial melted, so are some of the glass, instruments shattered and needless to say the electrical harnass a mess. The was even severe burn marks on the paint work.
The lady, alive but shaken.

So, are cars really a safe haven from lightning or are Opels not so safe


This makes me rethink the quote regarding steel boats....