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Old 22-07-2012, 16:47   #136
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Re: Lightning Strikes

i have placed a cookpot over the binnacle on occasion--in someone elses boat in the gulf of mexico--here i havent bothered to do that--my binnacle is too large for a pot to cover.
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Old 22-07-2012, 17:05   #137
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Re: Lightning Strikes

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i have placed a cookpot over the binnacle on occasion--in someone elses boat in the gulf of mexico--here i havent bothered to do that--my binnacle is too large for a pot to cover.
Wow, you should really consider getting lower-powered compass lights...though heating hot choccy at the wheel is a neat idea.
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Old 22-07-2012, 17:22   #138
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Re: Lightning Strikes

rofl---upside down to cover and protect----and with my autopilot i can still be in cockpit while cooking hot chocolate if i feel is urgently needed...
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Old 22-07-2012, 18:13   #139
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Re: Lightning Strikes

Well--I have listened to stories of bad advice given by so-called experts, who frighten the heck out of me when I consider that for the most part they themselves bear no consequence for such advice--even if they get to know the results tjherefrom.

Personally I know enough about the subject to have some concerns that lives are being put at risk on the basis of some crazy ideas.

Firstly, the path from earth to the charged portions of atmosphere is dependent on resistance--which is dependent on the ionization of the air.

Ionized air is not uniform in intensity or its volume. It may be a long spiralling column, or it may be a broad expanse of charged air travelling at wind speed over the ground. It is not a straight line path either, since the wind which blows it about varies in intensity at different altitudes, and there are many such evanescent paths available in the atmosphere at any one time as charge can migrate from one part of the system to another without reaching earth. In any event, charge density or availability is is not a constant.

This explains why the tallest structures are not always the ones which are struck, and the degree of protection is a factor but not the only factor. As for there being two types of lightning discharge--that may be true--but I know of only one--but it does have different effects depending on the atmospheric situation and the conductive properties of objects on the surface of the ground. All lightning discharges which reach earth involve electron flow from the earth to the charged atmosphere, at least initially.

Providing a conductive system for allowing charged ions to escape to earth as an electric current actually increases the total "resistance" of the air above the conductor by de-ionizing it temporarily. Of course the wind will replace the air with other possibly ionized air very quickly, so the conductive system may need to work frequently. This is in effect what happens--but the voltage discharged is usually fairly low--but it is very common. Gaseous arrestors as used in telecommunication protector terminals give an audible POP as they fire--and when there is any electrical activity in proximity to these open ariel conductors such popping is quite frequent. You will not know if your lightning conductor is working unless you fit some sort of pulse measuring device in parallel with it.

There are a few good systems designed for vessels, but i always like to point out that radio earths need to be separate from the lightning discharge earth plates. Use copper discharge earth plates for steel hulls, use alluminium plates on aluminium hulls. Place lightning discharge earths under the mast. If you have two masts--use two plates. I bolt them on using tufnel bolts through brackets fastened to the hull--and run the heavy connecting cable through a polyethene stand pipe to deck level. Make sure you have zinc anodes though--

Radio earths need to be situated well clear of the lightning discharge plate--I have mine well aft. All it connects to by direct connection is the radio sets and radar. Everything else is double-insulated, but the twelve volt system is is connected across a gaseous arrestor earthed to the radio earth plate. The arrestor will fire at 600 volts earth potential and conduct until about eighty volts--then discharge will cease. Just a bit of extra protection for the pumps etc--because it is in the boat's wiring that the induced currents flow--and I want them discharged before they burn off any insulation and start fires--

My advice to anyone considering lightning is to disregard well-meant advice (including mine) and research the thing yourself. My experiences are mostly to do with buildings and steel towers--but the ocean is a very good earth. Your chances of being struck in a completely unprotected vessel are low--and yet people die every year from lightning strikes nearby. Many more are seriously burned.

Complacency might be contagious--but lightning can kill you or sink your vessel, leaving you to drown or get chomped by something in the water. A good lightning system will cost about six hundred or so--what is the life of yourself and your loved ones aboard worth?
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Old 22-07-2012, 18:14   #140
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Re: Lightning strikes

Quote:
Originally Posted by cat man do View Post
So if lightening wants to take the past of least resistance doesnt it make sense that the boat with the best grounding system is most likely to get hit?
In this case it was the powerboat
We were close to that boat and our 60' mast is connected to the water in a straight run with a 4/0 cable permanently connected to the mast and ending in an electrode with 48" of edge surface on it. So we were also a well-grounded boat. We were not hit.

Someone in this thread understands science and stated that there is a scientific rational behind lightning but one only understands it through probability analysis. This is the only valid way to scientifically understand lightning. Those who attempt to understand it through unique personal experiences or through small surveys of boats they know, etc, are not approaching it scientifically and the data is not valid by themselves. And this type of science is not unique to lightning - it is also how epidemiology, quantum mechanics, blackjack and baseball, to name a few areas, are studied, understood and predicted (sports bookies and professional card players make a fortune taking advantage of people who don't understand probability science).

For example: here is a small informal data set that contradicts the one given by John Hacking - 10 boats (that I directly know of) were damaged by lightning in the San Blas Islands so far this year. Of those ten, eight had no lightning grounding or bonding system and two did.

And Zehag: come to the Caribbean side of Panama if you really want to see lightning! No disrespect for Pacific Mexico or Florida, but you guys are in second and third place when it comes to lightning! We have had only 5 nights of the past 70 days that did not have lightning storms.

Here are some facts:

You cannot protect your boat from a lightning strike, you can only mitigate the damage that one will do. This is most likely the confusion around whether a "lightning rod" is snake oil or not. It is snake oil if it is used alone and with the expectations that it will ward off strikes. It is sound science if it is used as the highest point of a robust down-conductor to a grounding plate sufficient to dissipate the energy - and it has the expectations of minimizing structural damage to the boat and not preventing a strike.

If you take a direct lightning strike from a very large, multi-fed bolt, your boat and you will be destroyed no matter how well (or not) it is grounded. I think a previous poster pointed this out. I don't think the full ramifications of that statement has set in for many people. In other words, this whole argument is moot in the face of a massive strike. Anyone who has watched severe lightning storms has seen the type of bolt I'm talking about - the bolt that is many times larger than all the others and that seems to drill into the earth for 4-5 seconds culminating in a sonic wave that threatens to knock you over.

If you take any smaller, more normal strike on a boat bonded like Mark Johnson describes, your boat will most likely be spared structural damage, but you will still lose a lot of electronics and electricals.

If you do not bond your boat in any way that allows a path for lightning to get to ground, you will most likely suffer significant structural damage.

Providing a robust path to ground for lightning does not attract lightning. A lightning strike begins over a mile in the air and contains up to a million volts and hundreds of thousands of amperages. By the time it has followed an ionization path down 99% of the way to ground, it is not searching around for the best grounded path to go that extra 50 feet - EVERY boat looks like ground to it at that point. This is also one of the reasons lightning seems so "unpredictable".

To advise people specifically against taking measures to protect their boats from structural damage in the event of a lightning strike is bad advice. To take that advice is insanity.

Mark
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Old 22-07-2012, 18:21   #141
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Re: Lightning strikes

Quote:
Originally Posted by colemj View Post
We were close to that boat and our 60' mast is connected to the water in a straight run with a 4/0 cable permanently connected to the mast and ending in an electrode with 48" of edge surface on it. So we were also a well-grounded boat. We were not hit.

Someone in this thread understands science and stated that there is a scientific rational behind lightning but one only understands it through probability analysis. This is the only valid way to scientifically understand lightning. Those who attempt to understand it through unique personal experiences or through small surveys of boats they know, etc, are not approaching it scientifically and the data is not valid by themselves. And this type of science is not unique to lightning - it is also how epidemiology, quantum mechanics, blackjack and baseball, to name a few areas, are studied, understood and predicted (sports bookies and professional card players make a fortune taking advantage of people who don't understand probability science).

For example: here is a small informal data set that contradicts the one given by John Hacking - 10 boats (that I directly know of) were damaged by lightning in the San Blas Islands so far this year. Of those ten, eight had no lightning grounding or bonding system and two did.

And Zehag: come to the Caribbean side of Panama if you really want to see lightning! No disrespect for Pacific Mexico or Florida, but you guys are in second and third place when it comes to lightning! We have had only 5 nights of the past 70 days that did not have lightning storms.

Here are some facts:

You cannot protect your boat from a lightning strike, you can only mitigate the damage that one will do. This is most likely the confusion around whether a "lightning rod" is snake oil or not. It is snake oil if it is used alone and with the expectations that it will ward off strikes. It is sound science if it is used as the highest point of a robust down-conductor to a grounding plate sufficient to dissipate the energy - and it has the expectations of minimizing structural damage to the boat and not preventing a strike.

If you take a direct lightning strike from a very large, multi-fed bolt, your boat and you will be destroyed no matter how well (or not) it is grounded. I think a previous poster pointed this out. I don't think the full ramifications of that statement has set in for many people. In other words, this whole argument is moot in the face of a massive strike. Anyone who has watched severe lightning storms has seen the type of bolt I'm talking about - the bolt that is many times larger than all the others and that seems to drill into the earth for 4-5 seconds culminating in a sonic wave that threatens to knock you over.

If you take any smaller, more normal strike on a boat bonded like Mark Johnson describes, your boat will most likely be spared structural damage, but you will still lose a lot of electronics and electricals.

If you do not bond your boat in any way that allows a path for lightning to get to ground, you will most likely suffer significant structural damage.

Providing a robust path to ground for lightning does not attract lightning. A lightning strike begins over a mile in the air and contains up to a million volts and hundreds of thousands of amperages. By the time it has followed an ionization path down 99% of the way to ground, it is not searching around for the best grounded path to go that extra 50 feet - EVERY boat looks like ground to it at that point. This is also one of the reasons lightning seems so "unpredictable".

To advise people specifically against taking measures to protect their boats from structural damage in the event of a lightning strike is bad advice. To take that advice is insanity.

Mark
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Old 22-07-2012, 18:56   #142
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Re: Lightning Strikes

who is advising??i was saying i wouldnt add something to attract lightning to my boat.
i didnt recommend anything--is totally up to them. i have found that lightning is nasty and will kill ye.
friends recently--within the past 2 weeks, actually-- have had lightning strikes to unprotected boats without major damage and i know of a single boat hit 2 times in 4 yrs and badly damaged both times--was the only protected boat in that canal and no unprotected boats were hit. he is a NASA engineer.
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Old 22-07-2012, 21:36   #143
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Re: Lightning Strikes

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Originally Posted by micah719 View Post
Science, eh? Depends if it's real science, or just dressed up like it. When there are conflicting reports from "scientists", I suspect witchdoctors, or as Capn Zee said, snakeoil sellers.

I read an article just yesterday about how lightning seeks to discharge to the surface of the water, yet this new spin suggests treating a boat like a house and using the existing fittings...subsurface. Either one of them is wrong, or both of them...
These two reports are not exclusive. Yes, lightning will seek the surface of water, also it could well be that multiple grounds are best to discharge to the surface of the water, but too complex (expensive) to practically implement. Another factor is fresh water vs. saltwater. Fresh water has 1000 times more resistance on average than saltwater and for that you really may want the multiple grounds.
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Old 22-07-2012, 22:30   #144
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Re: Lightning Strikes

Lightning does not discharge TO the surface of the water--it discharges FROM the surface of the water initially--in the absence of anything else available--but what difference does that make? We aim to remove the ionizing charges from atoms of gas in the local vicinity as well as any other chargeable molecules in the air--as well as to conduct a small to medium discharge to earth.

It does not really matter in which direction the actual electrons flow--what matters is a destroyed vessel and burned victims. The only way to make your vessel. attractive to lightning is to shoot a very thin wire from it as high as possible into the air. That will precipitate a strike of sorts--maybe even a big one.
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Old 22-07-2012, 22:53   #145
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Re: Lightning Strikes

Quote:
Originally Posted by zeehag View Post
i do not need furthr education in the science of lightning beyond that which i already have been taught by experts in everything--i KNOW lightning--was a very very close call aT AGE 3 YRS -.
...Oh yes we know and add to the list accomplished cruiser, rigger, doctor, maintenance specialist, and all round judge of character. What you say MUST be true...
A Podcast, "stuff you should know" had an excellent episode last week on lightning. One of the things they stated was it is a myth that rubber tires protect you while in your car during a strike. It's actually the Faraday effect of the metal that protects you as stated in an earlier post.
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Old 22-07-2012, 22:55   #146
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Re: Lightning strikes

In a lightning strike, there is a strong EM pulse and electrical disruption due to the generated plasma field and ionization of the area surrounding the strike. That's what takes out the unplugged electronics. IOnduced current on all the circuit paths that actually heats and burns out the boards and chips. A strong solar flare can do the same thing on a global level......look up "The Carrington Event" in the late 19th Century.....telegraph wires ignited spontaneously due to induced current from the EM effects.

Quote:
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....
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Old 22-07-2012, 23:48   #147
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Re: Lightning strikes

Quote:
Originally Posted by colemj View Post
We were close to that boat and our 60' mast is connected to the water in a straight run with a 4/0 cable permanently connected to the mast and ending in an electrode with 48" of edge surface on it. So we were also a well-grounded boat. We were not hit.

Someone in this thread understands science and stated that there is a scientific rational behind lightning but one only understands it through probability analysis. This is the only valid way to scientifically understand lightning. Those who attempt to understand it through unique personal experiences or through small surveys of boats they know, etc, are not approaching it scientifically and the data is not valid by themselves. And this type of science is not unique to lightning - it is also how epidemiology, quantum mechanics, blackjack and baseball, to name a few areas, are studied, understood and predicted (sports bookies and professional card players make a fortune taking advantage of people who don't understand probability science).

For example: here is a small informal data set that contradicts the one given by John Hacking - 10 boats (that I directly know of) were damaged by lightning in the San Blas Islands so far this year. Of those ten, eight had no lightning grounding or bonding system and two did.

And Zehag: come to the Caribbean side of Panama if you really want to see lightning! No disrespect for Pacific Mexico or Florida, but you guys are in second and third place when it comes to lightning! We have had only 5 nights of the past 70 days that did not have lightning storms.

Here are some facts:

You cannot protect your boat from a lightning strike, you can only mitigate the damage that one will do. This is most likely the confusion around whether a "lightning rod" is snake oil or not. It is snake oil if it is used alone and with the expectations that it will ward off strikes. It is sound science if it is used as the highest point of a robust down-conductor to a grounding plate sufficient to dissipate the energy - and it has the expectations of minimizing structural damage to the boat and not preventing a strike.

If you take a direct lightning strike from a very large, multi-fed bolt, your boat and you will be destroyed no matter how well (or not) it is grounded. I think a previous poster pointed this out. I don't think the full ramifications of that statement has set in for many people. In other words, this whole argument is moot in the face of a massive strike. Anyone who has watched severe lightning storms has seen the type of bolt I'm talking about - the bolt that is many times larger than all the others and that seems to drill into the earth for 4-5 seconds culminating in a sonic wave that threatens to knock you over.

If you take any smaller, more normal strike on a boat bonded like Mark Johnson describes, your boat will most likely be spared structural damage, but you will still lose a lot of electronics and electricals.

If you do not bond your boat in any way that allows a path for lightning to get to ground, you will most likely suffer significant structural damage.

Providing a robust path to ground for lightning does not attract lightning. A lightning strike begins over a mile in the air and contains up to a million volts and hundreds of thousands of amperages. By the time it has followed an ionization path down 99% of the way to ground, it is not searching around for the best grounded path to go that extra 50 feet - EVERY boat looks like ground to it at that point. This is also one of the reasons lightning seems so "unpredictable".

To advise people specifically against taking measures to protect their boats from structural damage in the event of a lightning strike is bad advice. To take that advice is insanity.

Mark
Please cite your sources for indicating what works and what doesn't in mitigating lightning damage.

I noticed one of the links from the first page of this thread pointed to another thread that indicated the insurance companies had found no difference in strike probability for grounded and ungrounded boats. I looked for the this info because I wanted to know about damage probabilities but couldn't find any published data.
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Old 23-07-2012, 02:21   #148
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Seems to be alot of expertise here so I might as well ask a few questions (not to many lightning strikes down here in Tassie).

When delivering boats with unknown bonding systems I have often shackled chains onto the rigging wires and towed them. I don't know if it works but figured it might just reduce the chances of blowing a hole in the side of the boat or a side flash? I like external chainplates for the same reason, though with the paint would they have too much resistance to disipate any ionised charge?

I had the top meter of both wooden masts (ketch) glowing like a green neon tube once... Very scary. Is this common, and what is it indicating?

How effective is an oven as a faraday cage, or would it be better to put the electronics in a pot with the lid? Or Both ?

Finally what nasty things can I expect to happen to my steel boat if I got hit with a bolt. I kind of figured the boat would not be damaged, just electronics and paint?

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Old 23-07-2012, 03:54   #149
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Re: Lightning Strikes

I have heard that large auto jumper cables clipped onto the shrouds with good sized copper plates clipped or welded onto the other clamp and submerged in the sea is a good substitute for an internal grounding system. What say you experts? gts1544
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Old 23-07-2012, 03:55   #150
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Re: Lightning Strikes

I love this thread! I'm inclined to think Zee has best science for sitting in a massive pool of electrolyte (born out by experience) but Mike's science is best for land (born out by his experience)
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