Lightning????

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walt
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Re: Lightning????

Post by walt » Sun May 20, 2012 11:42 am

If your getting advice on home building - no.

(my apologies for putting that in there and I absolutely do think Mr. Stewart is a very bright person - but since its the public internet, you always have to question where something came from)

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Re: Lightning????

Post by walt » Sun May 20, 2012 1:32 pm

FYI, in my previous post, I wanted to point out that my comments regarding the catamarans not being grounded was to only point out the lack of evidence that having some sort of metal in the water has any influence on your chances of getting struck by lightning. If there is a claim that grounding has any influence, it should be backed up.

In the past, we Macgregor owners have had some interesting discussions on lightning and I don’t think we need to repeat a bunch more stuff that won’t get read link here http://macgregorsailors.com/forum/viewt ... 0&start=45 . Previous to the particular post which I responded to in this thread, the advice was given to not do anything – which I really can’t argue against. Some years we get a lot of lightning where I sail so I chose to carefully do something since Its my opinion this is a net positive..

There is one new idea regarding T storms I wanted to throw out mostly for HaminX since we have discussed this in the past and I know he has been interested in and has a lot of experience with the wire brush dissipaters at the top of the mast. I think this paper somewhat explains what they do and regards some of the other odd things we experience on sailboats during a thunder storm. . This paper is here http://zenpole.com/Corona_current_rev_0.pdf and comes from these references below which sometimes can be found free on the internet and are interesting reading if you like this sort of thing.

1. “Responses of Lightning Rods to Nearby Lightning” C. Moore, G. Aulich, W. Rison, Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology (C. 2001)
2. “Lightning Rod Improvement Studies”, C. Moore, W. Rison, J. Mathis, G. Aulich, Langmuir Laboratory for Atmospheric Research, Geophysical Research Center, New Mexico Institute of Mining and Technology (1997, final form April 1999)

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Re: Lightning????

Post by Hamin' X » Tue May 22, 2012 11:45 pm

Walt,

I wish you all success in the sale of your lightning protection system. There are many systems out there and a lot of people are looking for a "silver bullet". I think that you need some more real world testing though, as I have seen real lightning strikes vaporize tower legs when the installers thought that they had sufficient grounding. I have seen it destroy 5/16ths guy wire in the same manner. All the while, my towers stand nearby with their brushes. The naysayers of my brushes continue to point out their use on grounded systems. If you read what I say and practice, they are used on ungrounded systems. As the negative charged cloud bottoms draw up the positive ions, they are discharged into the air from the sharp points of the brushes, before they can form the streamers that are needed to complete a path for the destructive down-stroke.

In previous threads, you have distorted my views and/or ducked obvious inconsistencies with yours. I suggest that all readers of these forums go back and read the entire previous threads and then do due diligence on their own part and do their own research. Go around and look at commercial installations. Go look at power company sub stations. Look at NASA launch pads. Look at communication towers. If grounding did not attract lightning, these folks would not bother to place grounded lightning rods around their installations to attract lightning away from their equipment. Why do you think that the power company runs their ground wire above the rest of their wires?

Don't look at other sailboats. Don't look to the likes of Don Casey. Don knows a little bit about everything, just enough to be dangerous. I have found many things in his writings to just enough off, that I won't trust him.

Trying to discuss the ins and outs of lightning protection and/or avoidance on this forum is not likely to be productive. You have university alphabet soup behind your name and I have real world experience. I think that if I want my house wired safely and correctly, I'll call a licensed, union electrician, not an electrical engineer.

As I have stated before: If you are not willing to invest several thousand dollars to install a proper lightning grounding system on your boat, you are better off doing nothing. Statistics say that you are not likely to be struck.

Fair winds.

~Rich

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Re: Lightning????

Post by walt » Wed May 23, 2012 8:48 am

Fair enough..

I’m pretty sure that no commercial tower install would let you get away with not grounding the tower – those towers must be your own personal towers on your own property?

One caution – sailboats with ungrounded masts and the wire brush on top do get struck by lightning. If your tower is not grounded and it does get struck, a significant amount of the energy could come though the cable into your house – receiver. I would think this could be personally dangerous.

I would like to continue the discussion on the wire brushes, do you have any other references showing they prevent lightning stikes on sailboats?

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Re: Lightning????

Post by Hamin' X » Wed May 23, 2012 10:02 am

Why would you want to place the brush on top? I place them down on the sides. As long as they are in open air, things are fine. You are correct in stating that a wire brush on top of a grounded structure will be vaporized. I have worked on both commercial and amateur radio tower installations. Most commercial installations use grounded structures and are willing to invest the money to do things right. It is on these installations, when grounds fail, or are inadequate, that catastrophic failures occur. In my experience, improper grounding causes more damage to equipment than not grounding. If you start grounding things, you MUST do so in such a way that when you are struck, all equipment rises to the same potential at the same time. It is difference in potential that does the damage. Most people are not willing to spend the time and money to do this and most do not have the knowledge to do it properly.

Asking for me to prove a negative, is like me asking you when you stopped beating your wife.

~Rich

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Re: Lightning????

Post by Sumner » Wed May 23, 2012 10:28 am

This is one of those subjects that it is hard to post about without someone feeling that you are attacking them. It is also a topic where no one is going to be able to prove they have the 'correct solution' as there are just too many variables involved with lightning. Kind of like saying we can run these two cars into each other time and again and that your seat belt or air bag will always protect you. With that in mind I'll try and post a few things to possibly consider.

First I feel that you can't really equate what is happening with lighting regarding tall towers vs. a sailboat. If you can believe NOAA ( http://www.nssl.noaa.gov/primer/lightni ... asics.html) there are two basic types of of ground flashes: natural (those that occur because of normal electrification in the environment), and artificially initiated or triggered. They go on to say...
Artificially initiated lightning includes strikes to very tall structures, airplanes, rockets and towers on mountains. Triggered lightning goes from ground to cloud, while "natural" lightning is cloud to ground.
While our mast looks 'tall' to us during an electrical storm it really isn't very tall compared to "very tall structures, airplanes, rockets and towers on mountains". Since tall towers can actually trigger a strike they usually always have protection on them with a grounding system. I feel that reading NOAA's description of what can "trigger a strike" is something way taller than our mast so I'll rule out that our mast has the ability to trigger a strike (grounded or ungrounded). If we can't 'trigger a strike' we are likely to only be hit if the strike ends up within about 50 yards of us on its last step to the ground and at that point are the tallest point (shortest path to ground).

The chances of us being at that point are small, but still it does happen. If we are at that point most evidence points to the fact that if we have no attempt at grounding or do have a system in place our odds are about the same of being the final step for the lightning to take. Some of the same evidence also suggests that the boats that are hit with protection are damaged less. Still the data base on all of that evidence is a lot smaller than one would hope for.

Since lightning normally hits the waters surface I'll go with the hope that we have a better chance of keeping the strike from going from the bottom of the mast and out the bottom of the boat (think hole in the bottom) with what Walt is trying to accomplish with his approach to grounding. I'm not sure it is really grounding, but a system that is trying to divert the strike to where it would go if the boat wasn't there, the water's surface.

Can he prove now or maybe ever that it works? Probably not, but we believe in it vs. the alternatives enough to use it. If it even worked 25% of the time we'd use it. There again kind of like the seat belt deal,

Sum

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Re: Lightning????

Post by walt » Wed May 23, 2012 1:45 pm

“Asking me to prove a negative”

Hamin, I thought I was asking if the ungrounded towers you have experience with are commercial – or are they only your own towers on your own property? I also asked if you had any references regarding ungrounded or grounded sailboat mast with our without wire brush dissipaters (located anywhere on the mast) having any influence on your taking a strike.

Reason I ask this is its hard for me to tell but it seems your lightning statistics about an ungrounded tower with a static dissipater are only based on your personal towers on your property. As I mentioned, an ungrounded tower with a coax cable leading into a house is likely very dangerous – you could be inviting a huge voltage spike in on the coax cable so I’m guessing you are the only one doing this. Just trying to establish a baseline for this data point.
FYI, I’m not sure of your whole setup with the ungrounded tower but it goes against National Association of Broadcaster standards (book is on my desk at the moment) – you should consider the safety aspect

Regarding equipment damage and bonding, what you’re saying is correct for a commercial building with a lot of interconnected equipment on a power grid system. But in the sailboat, we have equipment such as VHF receivers, cell phones, car stereos, TV, DVD’s, chart plotters etc. All of this is high volume commercial electronics mostly in plastic chassis and no matter how well you bond the input and output wires into these devices, you can still have damage from magnetic field induced transients inside the device on circuit board traces.

As Sumner said, this is about trying to keep a hole blown in the boat between the bottom of the mast and the nearest water surface. Put the key safety electronics in a metal cage, get insurance for the rest.

FYI, for the poster earlier (with the single post), The Zenpole also doesn’t actually make electrical contact with the water – the surface sparking electrodes (developed by Dr. Thomson) are actually well insulated from the water by a relatively thick oxide coating. So its not actually “grounding” to the water but this term can mean so many things when it comes to water.

I also don’t think the dissipaters have any negative effects - but they also don’t do any more than a sharp point somewhere on the mast does (I have a reference if this needs to get discussed more).

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Re: Lightning????

Post by Hamin' X » Wed May 23, 2012 2:55 pm

When most boats don't get struck, how can anyone prove that something prevented a strike? Kind of like your catamaran statistics, perhaps they get struck more often because they carry higher masts for their size? I don't know, but do know that you can show most anything that you want with creative statistics.

~Rich

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Re: Lightning????

Post by Catigale » Wed May 23, 2012 3:17 pm

The catamaran vs monohull statistics prove very little

For one thing, cats vs monohulls are not randomly distributed, so the two groups being compared are geographically biased for one...sort of like Cars with Florida license plates are more likely to have orange pips stuck in the tires..

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Re: Lightning????

Post by Sumner » Wed May 23, 2012 3:55 pm

Catigale wrote:The catamaran vs monohull statistics prove very little

For one thing, cats vs monohulls are not randomly distributed, so the two groups being compared are geographically biased for one...sort of like Cars with Florida license plates are more likely to have orange pips stuck in the tires..
They (Boat US) are saying cats are hit twice as much per 1,000 boats ( 9.1 vs. 4.5) and some possible reasons why are given here...

http://www.marinelightning.com/catamaran/index.html

What difference does it make to us if they are hit twice a much?

I'd encourage anyone who is trying to make a decisions on this to do all of the reading they can. There are papers and such written by Universities and such that go into the subject with a lot of detail. Take what you can from it and make a decision,

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Re: Lightning????

Post by Catigale » Wed May 23, 2012 4:00 pm

What difference does it make to us if they are hit twice a much?
It doesnt. It means dont boat in Florida rather than ground vs non-ground.

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Re: Lightning????

Post by mastreb » Wed May 23, 2012 5:19 pm

Grounding vs. non-grounding aside, by far the best way to protect a Mac from lightning strikes is to lower its mast and slip or park it amidst boats that are mast up.

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Re: Lightning????

Post by vizwhiz » Thu May 24, 2012 12:12 am

I heard a statement made once regarding lightning, with reference to a person feeling safer being in their car because of the rubber tires "insulating" them from the ground...it went something like... "The lightning bolt just jumped through hundreds of feet (or even farther) of air - which is normally considered an insulator...and you think it's going to stop at a little piece of rubber?" That lightning is going to follow the path to the "ground" be it the water or a building or whatever. I've watched lightning strike the ocean before, and it's amazing...but if your boat's right there in the way, well...good luck.

From "listening" to this, and reading the posts, this is nothing but an argument at the moment...interesting, but a lot of posturing and chest-puffiness... I think it's the basis of a very good discussion, but we'd all have to get together and have a beer or two first... :|

Sumner made a very good point because in Florida, lightning capital of the world (our part of the world anyway) they actually track both up-strikes and down-strikes...there's that much of it when storms roll through. We have a unique opportunity, and also a higher risk, than most, so this is of high interest to us down here!

I think the points that are well-made are well-made - if you aren't going to spend the serious boat-bucks to have a professional installation of a system (read that as "I can blame them if something happens") then it is likely better not to do something on your own that you make up yourself. If someone on your boat gets hurt because of your makeshift lightning rod, then you could be seriously liable just like any other makeshift device that gets someone hurt. Expert installer with experience and a good track record makes for a very credible argument, but doesn't invalidate others' input.

Alternatively, electricity follows a set of physics rules just like gravity and fluids and other things in the world around us, and those laws apply whether it is a small amount of electricity or a large one. The device recommended by an obviously educated EE has a significant amount of merit, albeit untested and essentialy unproven. But to discount the validity of the device because it is untested/unproven is like the reference to negative proof - can't prove it won't work any more than you can prove it will...and just because the laws function consistently doesn't mean that they provide for a reliable and functional implementation, which is just as important as having the calculations right...if you can't make it work, doesn't matter what the laws say.

So I'm back to Sumner's advice...read, check with your insurance company about what they approve/require, and read some more. Ultimately, it's not about who wins an argument, it's about boating with confidence and peace-of-mind knowing you've done what you can to be prepared, even if that means running from the storms.


Just my buck-and-a-quarter.

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Re: Lightning????

Post by Catigale » Thu May 24, 2012 5:19 pm

Alternatively, electricity follows a set of physics rules just like gravity and fluids and other things in the world around us, and those laws apply whether it is a small amount of electricity or a large one
It does, and the rules for large flows and small flows are completely different.i think this is what generates some of the chaff and commotion In discussion - when people who might have read Resnick and Halluday volume 2 start lightning protecting there boat, the results are amusing at least

Almost without exception, anyone hawking a solution commercially spouts studies that are hogwash.

Don't wash your hogs in a thunderstorm, btw.

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Re: Lightning????

Post by Sumner » Thu May 24, 2012 6:06 pm

Catigale wrote:..Almost without exception, anyone hawking a solution commercially spouts studies that are hogwash.
Do you have basis for that observation or is it a gut feeling? Are you saying that there are no lightning protection systems out there that offer any degree of protection?

I think I've spent enough time spouting my beliefs on the subject and will stick with them until I see reason to change them. And I will be pursuing with interest the subject in the future,

Sum

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