Lightning Protection

[senormechanico]

The above story is absolutely true. Cross my heart.

Steve B.

[EwenT]

Originally Posted by ronbo1

Lightning protection of boats and marine facilities

In addition to Gordo's excellent sources check out the above site. Though dated it provides good background in trying to understand lightning. One statistic it mentions is the chance of a boat being struck is highest in Tampa Bay, 4-20% of moored boats per year. Presumably if you own it for 30 years it's certain to be struck at least once.

I agree that some of the content of this site is showing its age. The IEEE paper, Sea Grant pamphlet and video were published about 15 years ago and since then some of the major concepts have changed considerably. This Fall the National Fire Protection Association is scheduled to publish its latest lightning protection standard, NFPA780-2008, which contains a major rewrite of Chapter 8, the watercraft section. See pp. 26-28 on http://www.nfpa.org/Assets/Files/PDF/ROP/780-08-ROP.pdf for a preview. Note that this is not the final version. Other editorial changes have been made but nothing substantial.

[GordMay]

Lightning kills man beneath cloudless sky - 06/22/2007 - MiamiHerald.com

”... With no rain or even clouds to warn him of the danger, death came literally out of the blue Thursday to a self-employed landscaper. The killer was a powerful bolt of lightning that cracked through perfectly clear skies ...
... Experts said Canales was killed by a weather phenomenon fittingly called a ''bolt from the blue'' or ''dry lightning'' because it falls from clear, blue skies ...
... The fair-weather bolts pack a bigger, deadlier punch and form differently.
Most lightning bolts carry a negative charge, but ''bolts from the blue'' have a positive charge, carry as much as 10 times the current, are hotter and last longer.
The bolts normally travel horizontally away from the storm and reach farther than typical lightning, then curve to the ground ...”

Goto: MiamiHerald.com - Miami & Ft. Lauderdale News, Weather, Dolphins & More

[EngNate]

I can see why a Dynaplate could explode if a massive amount of current went through it. It is made of sintered material, like a cinderblock, and is very porous. Under the boat, it is full of pockets of water. The water contact area is what makes it work efficiently for its size. If lightning current goes through it, the trapped water boils & expands and blows it apart.

With respect to a direct strike once it is initiated, I don't believe that lightning protection works - that is, you just can't carry a conductor big enough to divert the current from it's intended path which is established from the ground by a stream of electrons that has ionized the air and created a path which the arc follows. The bolt comes from the sky, but it's following a path which started at the ground. (See the Mythbusters episode and what they did to get "planned" strikes.) The resistance of an electric arc is virtually zero, regardless of its length. We have no conductor material like that.

For the present, I'm excluding effects of nearby or indirect strikes and flashes, power line surges that result, St. Elmo's Fire, etc. Lightning does a lot of wierd things, but it's still electricity and I hold the conviction that it must conform to Ohm's Law. The following is my theory, and I present it as such.

From the school of thought I went to, the practical element of lightning protection (prevention) lies in bleeding off electrons in a steady stream to prevent the sudden burst that ionizes the air along the way. Also important is preventing sudden changes in this electron stream. I'm fairly convinced that a mast with an intermittent bonding connection is a magnet for lightning.

The earth, and especially the water, holds a huge reserve of free electrons. Under a charged cloud, electrons in the earth bunch up and follow the cloud like the tidal wave follows the moon. Lightning producing clouds don't just appear, they develop and move along, concentrating electrons below. Electrons are constantly leaving the ground and rising to the cloud like champagne bubbles, and features on the surface - like your boat - influence this flow. Conditions ripe for a strike occur when flow is suddenly facilitated following a large buildup. Prevention is in facilitating a constant steady bleedoff of the electron reserve, preventing it from reaching a potential that will ionize a path for a strike to follow.

[44'cruisingcat]

Originally Posted by EngNate

With respect to a direct strike once it is initiated, I don't believe that lightning protection works - that is, you just can't carry a conductor big enough to divert the current from it's intended path which is established from the ground by a stream of electrons that has ionized the air and created a path which the arc follows. The bolt comes from the sky, but it's following a path which started at the ground. (See the Mythbusters episode and what they did to get "planned" strikes.) The resistance of an electric arc is virtually zero, regardless of its length. We have no conductor material like that.

.

I'm not sure I agree with this. I've seen lightning conductors on very old buildings (in Scotland, well over 300 years old) and they were about 1 inch by 3/8 inch solid copper. These buildings (churches, castles) would have been struck many times, but they hadn't burned down. A few times I asked about lightning damage I was told the buildings were sometimes struck, but not damaged.

[EngNate]

Back in the hills of western Virginia - settled by Scotch Irish - many barns had similar lightning rods, most made from 1/2" square copper rod, straight down the side and into the ground. In accordance with my theory, the rods avert more serious damage by having dissipated much of the electron reserve in the ground before the strike occurs.

[GordMay]

Originally Posted by EngNate

...In accordance with my theory, the rods avert more serious damage by having dissipated much of the electron reserve in the ground before the strike occurs.

I acknowledge your great knowledge & experience, and highly respect & value the vast majority of your very valuable advice & information, and intend no disrespect in suggesting that your theory (about dissipation, charge transfer, or early streamer emission arrays), is very likely wrong; and is certainly not supported by the theory, experimental data nor practical experience in the literature.

I’ve previously posted links to many scholarly sources, by respected & authoritative authors, on the subject.

[EngNate]

OKay, I did mean to specify it as un-qualified theory, and I'll definitely read... It's not the kind of thing many get or want a lot of firsthand experience with.

[EngNate]

Originally Posted by GordMay

Understanding Lightning Protection ~ by Bill Laudeman
BoatUS.com Seaworthy magazine

Gordie, the article above contains this:

"Therefore, I suggest that the primary goal of an LPS must be to allow the accumulating "ground charge" (the build-up of energy in the earth or sea below a thunderstorm) to drain away at a low voltage level and prevent the initiation of a strike. This is what the "ion discharge" or "dissipator" air terminals are designed to do. For these to be effective, however, they must be part of a well-designed system.. "

[GordMay]

W. J. (Bill) Laudeman, mat be a talented freelance writer, but is certainly not an authority on lightning.
Bill Laudeman's short resume

Apparently, Laudeman was asked by Seaworthy to write an article offering some practical steps that boat operators might take to prevent damage from lightning strikes, and became enamored with dissipation theory following a single interview with a single engineer.

As excerpted from:
Understanding Lightning Protection by Bill Laudeman (BoatUS Seaworthy Archives)
BoatUS.com Seaworthy magazine

“... Several years ago in preparing an article on "Lightening Protection Systems" (Practical Sailor, December 1993) I interviewed one of the engineers responsible for preventing lightning damage to the U.S.'s largest power utility, the Tennessee Valley Authority, plus others at firms making lightning damage prevention systems for high-risk operations such as petroleum refineries and tank farms. The conclusions reached were fairly simple, and within a short time after the article was published, advertisements began to appear for devices called ion dissipators, like those previously offered only in high-tech industrial systems. These are stainless steel wire brushes, typically about two inches in diameter and about eight inches long. You can buy a similar brush for a few dollars from a supplier of diary cleaning equipment; the ions probably can't tell the difference, but you will have to build your own mount ...
... Therefore, I suggest that the primary goal of an LPS must be to allow the accumulating "ground charge" (the build-up of energy in the earth or sea below a thunderstorm) to drain away at a low voltage level and prevent the initiation of a strike. This is what the "ion discharge" or "dissipator" air terminals are designed to do. ...”

Reading is good; but some care should be excercised in choosing one's sources.

Some contrary references:

A CRITICAL REVIEW OF NONCONVENTIONAL APPROACHES TO LIGHTNING
PROTECTION ~ BY M. A. UMAN AND V. A. RAKOV
MARTIN A. UMAN, Distinguished Professor: ECE-UF Dr. Martin Uman
http://www.lightningsafety.com/nlsi_lhm/Uman_Rakov.pdf

WAR OF THE LIGHTNING RODS ~ By Abdul M. Mousa, (Ph.D., P.Eng., Fellow IEEE)
http://www.lightningsafetyalliance.c...htning_war.pdf

There Is No Magic To Lightning Protection:
Charge Transfer Systems Do Not Prevent Lightning Strikes ~ William Rison
(Professor of Electrical Engineering, New Mexico Institute of Mining and Technology)
”... 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 ...
http://www.lightningsafety.com/nlsi_lhm/magic.pdf

Charge Transfer System is Wishful Thinking, Not Science ~ Charles B. Moore*
(Professor Emeritus, Atmospheric Physics, New Mexico Institute of Mining and Technology)
Charge Transfer System is Wishful Thinking, Not Science - National Lightning Safety Institute

*Charles B. Moore is internationally known for his research on the electrical aspects of thunderstorms and volcanoes. He is an expert in many different areas of atmospheric research, including the scientific and political aspects of weather modification, the scientific and practical issues of lightning protection, and the efficacy of different kinds of lightning rods:
Lightning and Thunderstorm Research - Langmuir Laboratory
http://infohost.nmt.edu/mainpage/news/2005/7feb02.html


Fundamentals of Lightning Protection ~ By Richard Kithil, President & CEO, NLSI*
*National Lightning Institute
Fundamentals of Lightning Protection - National Lightning Safety Institute

Evaluation of Early Streamer Emission Air Terminals ~ By Scott D. McIvor, Roy B. Carpenter, Jr., Mark M. Drabkin, Ph.D.
...”CONCLUSIONS: There is limited test data on ESE performance, and no available data substantiates the suppliers’ claims; conversely, the data collected by independent researchers prove otherwise. That is, the ESE performs no better than the conventional Franklin rod.
2. The physics related to the situation, as provided by the atmospherics physics community, demonstrate that the claims made for all of these ESE are wildly exaggerated ...”
http://www.ees-group.co.uk/downloads/ESE%20paper.PDF

[EngNate]

Originally Posted by Alan Wheeler

The only total effective way of protection is stay away from thunderstorms.

That is an indisputable fact. (There's the Dry Lightning, but also perfectly fit and healthy people drop dead from heart attacks, too)

Just how large are the grounding rods on ATC towers? 50 feet of the 1" x 3/8" copper stock, like on the barns in Scotland, weighs about 76 lbs, a bit of a challenge to install on or in your mast. They go directly into the ground, likely several feet. How do you make the equivalent connection in a boat? Not with a dynaplate, apparently, and not thru-hulls or keels. Will we make the whole bonding system from the same stock? Then, what about the exit points? What's do-able on a terrestrial structure may not be practical on a boat. From reading Ulman & Rakov, one thing I conclude is that the practicalities of applying lightning protection to vessels was not brought into their scope in any way whatsoever. Illustrations 1: (a), (b), and (c) irk me a bit because they are a composite of real-world (the lightning bolt was photographed) and artist's conception (the rest is a drawing). Beside those illustrations is a sentence that I think at least establishes charge-dissipation theory as a valid pursuit:

"...when the downward-propagating leader passes
through that surface at a specific location, the leader
is “captured” by a specific point on the ground or on

a grounded object."

I'm going to concede that I don't know on which side the results of that pursuit will ultimately fall. If it goes one way, the poll will be more or less right - prayer is your best bet!

The idea behind charge dissipation is to make the boat a less likely capture point by keeping the voltage potential below the threshold long enough for a peak potential overhead to pass without striking. Anyone's claim of eliminating lightning strikes is ludicrous, and it's logical that under some conditions these devices could be more likely to be struck. Note, I haven't advocated the use of any device. The fact is, you have got a stick in the air. I'm all about robust and secure bonding. It does appear that I've got the polarities mixed up. Most cloud to ground lightning comes from the negatively charged bottom of the cloud, which attracts a shadow of positive charge in the ground below. The opposite condition does occur more rarely.

Laudeman is certainly no scientist, engineer, or technician - he's a journalist, what would you expect? But, his information came from folks who have multi-millions, maybe dozens or hundreds of millions at stake from lightning damage. (The Tennessee Valley Authority is one of the largest (the largest?) electric utilities in the US.) The same credibility could be said for the FAA, and lots of lives, too. (FAA cited in referenced articles) However, as of Sept. 10, 2001, the FAA didn't forsee any necessity of locking cockpit doors.

[Unicorn Dreams]

How good would this work for protection, 2 aluminum mast, 36' and 52' tall, numerous ss shrouds going to ss chain plates bolted to steel hull. Bottom of keel 14" x 10' unpainted. What little amount of grass that grows there, i can brush off with 2 breaths. 19 years old, don't know if its ever been hit or not, never have found any damage. 1st 14 years of life was in the Fla Keys.

[David M]

It's easy to forget that electricity will take the path of least resistance. Create a low resistance path for it to take versus a higher resistance path in the same area and it will "choose" the path of lower resistance. If your boats aluminum, carbon, or wood mast is 50 feet in the air, its going to be the path of least resistance between the water and the sky, versus the surrounding atmospheric path of greater resistance. There is no stopping lightning...the best strategy we have is to create a path of least resistance through the boat in order to minimize the damage. My best guess would be to run a copper wire from the top of the mast down to the lead keel. Then you have created a path of least resistance where the electrons are least likely to stray from the copper wire creating damage elsewhere. The only thing I can think of that would work is to drag a good sized diameter copper wire from the masthead to the water behind the boat..but that of course would be impractical. There is no ideal solution.

Lightning ionizes everything in its path...the ions create free electrons which help in directing the lighting by basically lowering the resistance in the lightnings path.

I think the only thing that can be done is to create a relatively linear path for it away from the critical things on your boat and hope for the best.