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Old 15-06-2012, 07:25   #16
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Re: Lightning strikes

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Originally Posted by Vasco View Post
After getting a direct masthead strike while sailing I have come to the conclusion that ... nothing can be done to minimize the damage caused by a strike.
I disagree with this. In your case, the keel stepped mast most likely minimized the damage. The lightning seeks ground and without ANY connection from the mast to ground, will simply blow through other spots to get to it. Without your mast to ground connection, there is a good chance your boat would have been holed catastrophically. Where the through hulls showing electrical activity also bonded to your grounding system?

However, I don't think hanging battery cables from shrouds will do any good. A boat needs a high-contact, low resistance, direct conduit from the mast to the water that can handle the current. Battery cables on a shroud rely on several weak, high resistant connections and an indirect conduit to ground.

And I feel for you - we took a direct strike less than a year ago and have yet not returned to a state where we don't assume a fetal position during any lightning activity!

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Old 15-06-2012, 07:25   #17
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Re: Lightning strikes

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Originally Posted by colemj View Post
I can underscore this statement with an example:

Yesterday in our current anchorage here in Panama, a powerboat took a direct strike. The powerboat was anchored with large sailboats all around it and was the lowest point by a good 40'. None of the sailboats were hit. And the powerboat had an extensive lightning protection system that consisted of multiple down-conductors connected to multiple thruhull electrodes around the waterline.

So, not even a well-protected boat underneath much taller conductive structures is safe from a direct strike.

Mark
Know of a similar experience. With a large number of sailboats stern-to at the marina, the smallest boat took the hit--in the middle of the fleet.
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Old 15-06-2012, 07:30   #18
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Re: Lightning strikes

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Originally Posted by cal40john View Post
The founder of this company was a University of Florida professor and had done some research on lightning.

I don't know if there is a track record yet with his system, but the recommended installation will drive you to buy a new boat and have it installed during construction.
Lots of sciency articles on the website.

Marine Lightning Protection Inc.
Had not heard of the company but if founded by a lightening researcher from UF it must be Martin Uman. He is certainly considered one of the best if not the best expert in the field world wide.

Has a cool setup for his research. He has a facility in the area with bunkers full of test equipment and a launch pad for model rockets that trail a grounded wire when fired. When thunderstorms are in the area they shoot at it with the rockets and capture strikes pretty often. Sort of a modern version of Ben Franklin's kite and key. I think if anyone could come up with a system to minimize the risk and damage from lightening strikes Uman might be the one.
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Old 15-06-2012, 07:31   #19
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Re: Lightning strikes

there was a beneteau 55 in slidell louisiana that was hit not just once but twice--was extremely well protected by a NASA engineer who didnt want to get struck by lightning---first hit put boat into yard for 6 months. second hit, in same place, 4 yrs later, caused damage to the electrical system to half way to the house behind which the beneteau sat. boat sank second time and went to yard. methinks lightning protection is a crock.
good luck. we sailed for a yr in gulf of mexico in lightning storms daily. was scary. we presented a moving target and the gods must have laughed as we werent hit--55 ft lightning rod and all by ourselves.
we have many lightning storms here in west coat mexico, come rainy season---last year, there were close hits, no boats wer ehit inmazatlan...we will see how we fare in la cruz de huanaccaxtle.
our lightning protection consists of crocs, as nothing is attracted to them, a cat--thwre is no record in written history of a cat being hit by lightning--feline variety, not fiberglass...rubber suit to my crocs and covering my head, and sailing gloves.
PRAY HARD.
lightning is random experience--willhit where and when it hits--DOES hit same olace twice. that beneteau proved that one......
sail far and have fun--i keep a set of jumper cables in my boat, but methinks would be a lil late to wait until i was hit to use em, so i dont.....i was advised to place on my shrouds to dissipate a hit.
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Old 15-06-2012, 07:31   #20
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Re: Lightning strikes

Quote:
Originally Posted by cal40john View Post
The founder of this company was a University of Florida professor and had done some research on lightning.

I don't know if there is a track record yet with his system, but the recommended installation will drive you to buy a new boat and have it installed during construction.
Lots of sciency articles on the website.

Marine Lightning Protection Inc.
This is the system installed on the boat in my previous example that was struck yesterday. It was installed during construction. They are dead in the water right now - no electronics, no electrics, no engines...

Mark
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Old 15-06-2012, 07:36   #21
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Re: Lightning strikes

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Originally Posted by noelex 77 View Post
Grounding the boat does significantly reduce the level of damage when a boat is hit. It also possibly slightly reduces the chance of being hit, but the difference is very small.
There is really nothing you can do to the boat that will substantially reduce the chance of a strike, but grounding is worthwhile to minimise the damage.

Lightning strikes vary in intensity enormously so there is an overlap of damage between grounded and ungrounded boats. An ungrounded boat can be damaged less in a mild strike when compared to a grounded boat in a more severe strike, nevertheless grounding the boat is worthwhile.
Read what noelex posted and read it again. While all of it is spot on, let me just repeat this part:
"There is really nothing you can do to the boat that will substantially reduce the chance of a strike, but grounding is worthwhile to minimise the damage."

Anyone thinking that doing nothing doesn't increase the likelihood of damage is kidding themselves. The science supports grounding and bonding.

The only variable is the size of charge received (big strikes or little strikes ) and this is why so many report different outcomes.

Ever consider why ALL aircraft and communications towers incorporate lightning mitigation techniques (principally bonding and grounding). Hint, it isn't because they want to throw money at unproved concepts.

Perhaps I should qualify ALL, really I mean ALL the hundreds I have seen or been involved in, perhaps there are plenty that don't in other parts of the world
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Old 15-06-2012, 07:50   #22
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Re: Lightning strikes

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Originally Posted by sokari View Post
My husband and I have been sailing for almost 30 years, most of them as liveaboard cruisers. While cruising extensively in S.E. Asia from Oz we sat through electrical storms almost every day and they scared the daylights out of us. Nobody could give us any ideas on how to protect the boat. Luckily, we were never hit. Over the years we've known quite a few boats that have had lightning strikes and despite many discussions, no-one seems to have come up with a foolproof, or even nearly foolproof, way of averting this disaster. Most of these boats have been repairable however, the latest one was a total write-off. Does anyone out there have any suggestions?

I studied the subject "extensively" during the 10 years we were building our boat, (+ the 30 years of boatbuilding prior)... and have as complete a lightning protection system for Delphys as is still practical. It would be considered "state of the art".

"LIGHTNING PROTECTION" is just its name! IT DOES NOT "PROTECT YOU FROM LIGHTNING", and never claimed too! IT ONLY MINIMIZES THE LIKLIHOOD OF TOTAL BOAT DESTRUCTION, AND BEING KILLED BY SIDE FLASHES.

I have written NUMEROUS full page explanations on CF in the past. Look it up in "Mark Johnson's past posts" to find them...

Protecting all of your electronics is not likely, but "surviving a strike" can be made 100X more likely, with a bit of work. This is clearly proven over decades of scientifically compiled statistical evidence. Anyone who believes otherwise, is ignorant of the subject or simply doesn't believe in science at all.

This is not a controversial subject... The jury has been in for decades!

Look it up...

M.
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Old 15-06-2012, 07:51   #23
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Re: Lightning strikes

There is a good article written b BoatUS on Lightning at:
BoatUS.com - Seaworthy Magazine

The thing I found most interesting was that during their statistical analysis of insurance claims, Catamarans were struck almost twice as much as monohull sailboats.
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Old 15-06-2012, 08:05   #24
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Re: Lightning strikes

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Originally Posted by jeremiason View Post
, Catamarans were struck almost twice as much as monohull sailboats.
That's logical, after all they do have two hulls!
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Old 15-06-2012, 08:12   #25
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Re: Lightning strikes

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Originally Posted by colemj View Post
This is the system installed on the boat in my previous example that was struck yesterday. It was installed during construction. They are dead in the water right now - no electronics, no electrics, no engines...

Mark
Oh well. One more example of the random nature of lightening strikes and what a waste of time and money most all "protection" systems are.
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Old 15-06-2012, 08:38   #26
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Re: Lightning strikes

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Originally Posted by noelex 77 View Post
........... Lightening does not always follow this grounded path so it by no means foolproof.
It is certainly possible the ground system on your boat took some of the energy and prevented more serious damage, but in some cases the ground system is of little help.
The ground system is not designed to reduce the chance of a strike, although there is some evidence it may be a slight benefit in some circumstances.
I would agree with the general tenor of this post but I would like to expand on the point of just exactly the where the current flows.

Remembering that lightning is electrical flow and the actual electrons that are moving don't know that it is lightning that is causing them to dance around so they just move in accordance with the well known electrical principles. So the current produced from the strike will flow in all available (parallel) paths towards the potential charge they are seeking (normally the "ground" or the surface of the water). And the flow will be inversely proportional to the resistance of each path.

In the instance quoted, I suspect the bulk of the current went along the grounded path but enough went down other paths and that was enough (in this instance) to cause damage. Which is what others have already posted
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Old 15-06-2012, 09:04   #27
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Re: Lightning strikes

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Originally Posted by jeremiason View Post
.......
The thing I found most interesting was that during their statistical analysis of insurance claims, Catamarans were struck almost twice as much as monohull sailboats.
Quote:
Originally Posted by Vasco View Post
That's logical, after all they do have two hulls!
Actually the insurance figures show that catamarans moored, docked or at anchor are struck almost twice as often as mono likewise moored.

Again the science of why this is so is well known but down played by the twin hulled crowd. It is rather complex but let me simply it as much as I can.

When moored, the vortex of the micro currents of the water which are trapped between the two hulls which generates a surface charge that increases the potential electrical difference between the marco air currents in the atmosphere and the water surface thus creating the breeding ground for a lightning discharge from the atmosphere.

Clearly catamarans induce the extra strikes. One interesting experiment shows that if a catamaran has metal through hulls on both sides of each hull and they are bonded together, the number of strikes decrease to that similar to monos.











OK, I made all this up, its not true.
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Old 15-06-2012, 09:06   #28
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Re: Lightning strikes

sokari,
Lightning is a very controversial topic and "lightning protection" is almost always misunderstood, with people thinking that it means being protected from being struck, when what it actually means is "protecting" people from death and electronics from being severely damaged WHEN YOU ARE STRUCK!!!


You CANNOT make a boat lightning proof, nor significantly reduce the chances of a strike.
However, you CAN significantly improve the chance you, your crew, and your equipment will survive a strike

Unfortunately, Mother Nature is unpredictable and she can be a fickle witch at times....

But, there are things you CAN do to protect yourself and your vessel...

As I grew up in S. Florida and sailing the Bahamas, Carib, N. Atl. and summertime Med....and have had a home/business in central Florida (the lightning capital of N. America, with > 110 "thunderstorm days per year"!!!) for almost 30 years now, working in communications, etc. and I have personally seen my own radio towers struck by lightning many times, and the tower where I have a couple of my ham rdaio repeaters on (1300' tall) I've seen struck a LOT (it averages 1000+ strikes per year), and I've only once had any damage (minor at that)...and as I've read all the research and studies done by the Univ. of Florida's lightning research center and well as the definintive paper on this subject "Lightning and Boats", by Dr. Ewen M. Thomson. University of Florida (which the ABYC Lightning and Grounding recommendations are based on, as well as most marine insurance underwriters/adjusters use as their guide)..... perhaps I could clarify a few things....



Quote:
Originally Posted by sokari View Post
Does anyone out there have any suggestions?
Yes....and these suggestions are the same as they have been for decades.....

1) Using a static disappator,on your masthead,in addition to proper grounding of the mast, stays, etc. may allow your vessel's static charge to be blown off and may give you some added protection from being struck....
BUT, this is NOT in anyway a certainty, and anyone who tells you that you can add something to your boat that will keep you from being struck is either a liar, a saleman, or doesn't know what they're talking about!!!(probably all three!!!)

Although the science says they work, and I'm NOT saying they don't, but I'm skeptical....
The reason I'm skeptical about the static disapators actually making much difference, is that my ham radio repeaters are on a 1368' tall tower, with a few dozen large disappators (5' tall, with hundreds of spikes), and it gets struck over 1000 times each year.....
Just saying....


2) Follow the suggestions and recommendations of Dr. Ewen M. Thomson. (formerly with the University of Florida, and Martin Uman predessor), in his definitive paper on the subject, "Lightning and Boats".....and/or read over and follow these same recommendations from the ABYC pamphlet on this subject.....

Marine Lightning Protection Inc.
Articles
Amazon.com: Lightning and Boats: A Manual of Safety and Prevention (9780963956606): Michael V., Jr. Huck: Books

http://www.kp44.org/LightningAndSailboats.php
http://www.kp44.org/LightningProtection.php


If you follow these suggestions and recommemdations (as I have done), you should have yourself (and crew) well protected from lightning AND, if you add some "lightning arreestors" (Polyphaser, etc.) to antenna cables / electroinc wiring (especially to/from the mast), you'll also have an effective protection system for your on-board electronics as well.....
(BTW, because of practicality, I've opted to use my VHF antenna as a sacrifical "air terminal".....this isn't really recommended, but I have one 65' bridge that I pass under to get to the Atlantic and haven't found an approach that works better, yet!!!)

But, unless you get lucky, this will not keep you from getting struck.....as this is more luck than anything else....

I was stuck back in Aug 2006.....direct hit to the vhf antennas (I have two at the masthead) and masthead.....
Blew the vhf antennas to bits....
One was literally melted to a short, fat stub (about the size of your thumb), and the other was laying in about 10 pieces on the deck, and the masthead had a small scortch mark (about 3" - 4" long) right at the top, by the vhf antenna mount....
Although I did have my mast and shrouds well grounded (followed Dr. Thomson's recommendations), at that time I did NOT have any lightning arreestors in-line.....
My damage was only to electronics, and just those connected to the mast, or connected to other electronics which were connected to the mast....(radar/chartplotter, vhf, tv antenna, wind instr. gps, autopilot, cockpit instr. and SSB radio and tuner.....)
I replaced EVERYTHING electronic on-board, including ALL electronics wiring and cables....it was a BIG job, and including waiting for the ins co. adjuster, etc. it took about 2 months....

{Since this direct strike to my boat in 2006, I've sailed her across the Atlantic twice, thru the N. Carib and Bahamas, and around Fla....and have been thru many, many T-Storms, etc.....
And, as I wrote above, I've had many direct hits to my ham radio towers over the years, and have never suffered any major issues....only had one fm rec. front-end blown in 30 years....
So, I now have the added lightning arrestors on-board, and disconnect things when not in use for a few days and/or when T-Storms are predicted and I won't be needing that gear for the time being....and I've not have any lightning issues since.....}



To sum up....
READ Dr. Thomson's paper, follow his recommndations (as I did), and add some lightning arrestors on your antenna coax cables, wind instr. etc....and disconnect things when not in use....
And, you'll be in good shape!!!

Oh, and read noelex77's posts here as well....

sokari, I do hope you find these suggestions helpful....

Fair winds...
John
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Old 15-06-2012, 09:13   #29
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Re: Lightning strikes

Just another thought about grounding a boat...

The average lightning bolt has condcuts between 10 and 120 million volts....

Just for the sake of discusion...

I wonder if a direct lightning strike is really taking place or based on the actual voltage involved, it more common that non-direct strikes (Near misses) are more frequently causing the damages.

My Hypothosis is that boat is not as good a ground as water, even with grounding places. If electricity is trying to find ground, why not go directly to water...

Second, if a boat took even a 10 million volt strike, the chance of nothing more than losing your electrical systems seems remote.

My though is that even a near miss lightning strike will still generate electric field in the hull and surrounding water, capable of destroying electical devices and other damages routinely seen in lightning strikes.

Just a thought....
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Old 15-06-2012, 09:33   #30
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Re: Lightning strikes

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Originally Posted by jeremiason View Post
Just another thought about grounding a boat...

The average lightning bolt has condcuts between 10 and 120 million volts....

Just for the sake of discusion...

I wonder if a direct lightning strike is really taking place or based on the actual voltage involved, it more common that non-direct strikes (Near misses) are more frequently causing the damages.

My Hypothosis is that boat is not as good a ground as water, even with grounding places. If electricity is trying to find ground, why not go directly to water...

Second, if a boat took even a 10 million volt strike, the chance of nothing more than losing your electrical systems seems remote.

My though is that even a near miss lightning strike will still generate electric field in the hull and surrounding water, capable of destroying electical devices and other damages routinely seen in lightning strikes.

Just a thought....
Reasonable thoughts and logical!

As to "going directly to water", a large part of the reasoning is that the air is a good insulator, especially compared to ground metal mast. The only time the air really conducts is after it is ionised and the charge required to ionise the air is directly proportional to the air gap. A metal tower or even a tall building reduces the air gap and this why they are struck more often.

Of course, once the air is ionised, the ions make for a low resistance path and high currents flow - the visible effect is the lightning bolt (big spark ).
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