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  #11  
Old 08-04-2011
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Quote:
Originally Posted by kd3pc View Post
proven time and time again to be of absolutely no use in a direct lightning strike to the boat and cost way more than a "few hundred dollars" while they will still provide bypass and shortest path to ground, there is no way to guarantee that the strike will follow it...

as the OP finds, and will find, lightning can cause moisture anywhere to become volatile regardless of where it is, or how "dry" we may think the material is.

Many of these systems are almost as useful as ultra sonic bottom critter repellent.

Just the PL259 strike/arc boxes for ham radio and vhf coax are almost a hundred dollars each, and that is where you can take them to an earth ground. Appropriate ground rod and bussing are thousands for the material and installation....I just spent over $700 on a 50 amp, 100', three conductor copper with ground.....just the cable....as copper is $$$. Not to mention the tower grounding.. again this is on the land, where you can do what you want, cadweld connections and the like.

Look up polyphaser or Roger Block for more, accurate information. His designs are used by the DOD and many commercial tower erectors, with great success.

You can certainly find someone to do this kind of work, but I would still have great insurance.

Yes, I am a licensed electrician, and a ham radio operator, FWIW.

I made my statement based on several articles including a noted one by a research professor at the University of Florida. I think that probably carries a bit more weight than being a licensed electrician or Ham Operator. If you had a PhD or an electrical engineering degree I'd be more impressed.
The recommended wire per another source is to use tinned #4 marine cables with crimped connectors all leading to a suitable ground strip or external ballast keel. For my 39 footer I am replacing the plain copper cable with tinned marine cable. The wire from an online source is a bit under $200 for a 100 ft roll, which is enough to ground all the chain plates and mast. I probably need about $25 worth of connectors. On my vessel the ballast is internal so I installed an 8 foot x 1 inch x 1/8 inch Cu strip fastened on with #10 bronze bolts with a 1/2 machine screws as the thru hull connectors. Lightning ground systems for fiberglass sailboats operating in salt water have similarities but noted differences than land based towers. You are however correct in that there are no guarantees when it comes to lightning on how it will behave but fro piece of mind I'll stick with a grounded mast and rigging.
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Old 08-07-2011
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I hate to say it, but if this were my boat I think I'd get a hole saw and take a core sample in the affected area. You then have a hole to patch, and if the core sample is good you get the peace of mind to know your boat is still strong. If the core sample is bad, no insurance company will be hiding behind any expert 'opinion' of what needs to be done, while it is your life at risk.

Gary H. Lucas
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  #13  
Old 08-07-2011
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Being reasonably frightened of a lightning strike (living on a sailboat) I did a considerable amount of research awhile back which resulted in a page on "Lightning and Your Boat" on our website, the Frugal Mariner. Mirari quoted a research professor from the University of Florida above. I'm pretty sure I've read that report and several others by University Professors (with grant money in hand) which either copied that report or were copied by that report - hard to tell which came first.

Many experts conflict with each other - some with themselves. Bond - don't bond; ground - don't ground. It's a crap shoot. The famous "cone of protection" I've learned is totally bogus. Those little "static dissipaters" (by Forespar et al) are absolutely useless.

What works? Insurance. Plain and simple.
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  #14  
Old 08-07-2011
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Quote:
Originally Posted by Mirari View Post
If you had a PhD or an electrical engineering degree I'd be more impressed.
To the OP, if you need an authority, over experience as Mirari does:

here is your authority who dispels the "old school" single conductor between the mast stub and the keel thoughts you have attempted to revive for this subject for the more modern faraday cage model, that I mentioned previously. Fairly pricey, I might add. And installation even more so.

Dr Ewen Thompson, and Science & Technology


You might find this enlightening, if you read it all.

Of course your mileage may vary...
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  #15  
Old 08-07-2011
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Quote:
Originally Posted by Mirari View Post
I made my statement based on several articles including a noted one by a research professor at the University of Florida. I think that probably carries a bit more weight than being a licensed electrician or Ham Operator. If you had a PhD or an electrical engineering degree I'd be more impressed.
The recommended wire per another source is to use tinned #4 marine cables with crimped connectors all leading to a suitable ground strip or external ballast keel. For my 39 footer I am replacing the plain copper cable with tinned marine cable. The wire from an online source is a bit under $200 for a 100 ft roll, which is enough to ground all the chain plates and mast. I probably need about $25 worth of connectors. On my vessel the ballast is internal so I installed an 8 foot x 1 inch x 1/8 inch Cu strip fastened on with #10 bronze bolts with a 1/2 machine screws as the thru hull connectors. Lightning ground systems for fiberglass sailboats operating in salt water have similarities but noted differences than land based towers. You are however correct in that there are no guarantees when it comes to lightning on how it will behave but fro piece of mind I'll stick with a grounded mast and rigging.
That noted and eminent 'lightning professor' from FSU is now retired and actively engaged in the commercial protection of boats/yachts ... principally 'mega-yachts', etc. Here's his website that will seemingly show his 'current' [;-o] thinking on bonding, 'escape pathways', etc. etc. etc. : Marine Lightning Protection Inc.

Ive had 3 lightning strikes ... one blew a LARGE chunk of FRG from an encapsulated keel, one fried ALL my electronics (except that safely inside the 'oven' at the time), one 'spidered' a large section of a hull (had to be rebuilt after I assayed/found FG damage, etc.)

I once witnessed a boat that had received a direct amperage hit. The strike passed down the mast to the keel step then 'spread out' into perhaps a zillion exit points throughout the underwater sections of the hull. The only symptom: all the hull under the water was 'sweating'; the boat was 'totaled' by the insurance carrier.
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Old 08-07-2011
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Quote:
Originally Posted by Mirari View Post
I made my statement based on several articles including a noted one by a research professor at the University of Florida. I think that probably carries a bit more weight than being a licensed electrician or Ham Operator. If you had a PhD or an electrical engineering degree I'd be more impressed.
The recommended wire per another source is to use tinned #4 marine cables with crimped connectors all leading to a suitable ground strip or external ballast keel. For my 39 footer I am replacing the plain copper cable with tinned marine cable. The wire from an online source is a bit under $200 for a 100 ft roll, which is enough to ground all the chain plates and mast. I probably need about $25 worth of connectors. On my vessel the ballast is internal so I installed an 8 foot x 1 inch x 1/8 inch Cu strip fastened on with #10 bronze bolts with a 1/2 machine screws as the thru hull connectors. Lightning ground systems for fiberglass sailboats operating in salt water have similarities but noted differences than land based towers. You are however correct in that there are no guarantees when it comes to lightning on how it will behave but fro piece of mind I'll stick with a grounded mast and rigging.

I think you're wasting your money. My boat was hit while sailing. My keel stepped mast is grounded to a wing keel with a heavy battery cable. The charge went throughout the boat. From stem to stern. All through hulls showed "treeing" (burnt paint that looks like tree roots) although they are not bonded. Even the rudder had it where the gudgeon and pintle are. I have come to the conclusion that nothing helps. But if it makes you feel better, like hanging jumper cables over the side, by all means do it.
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  #17  
Old 08-07-2011
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Designing a Faraday cage into a boat certainly has a logic to it. Interestingly MLP's web site often phrases how their system might be working, or why they think things are happening, and their own words say they are not sure of what is really going on. Which has been the norm in lightning 'science' anyway.

Applying the concept to the usual monohull, standing rigging should be treated with antiseize at all connections or jumpered across them for a better ground path, at which point all of it becomes the Faraday cage, if you add a continuing path from the rigging into the water. That mightn't be terribly expensive in the grand scheme of things.
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Old 08-08-2011
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Regarding the 'Marine Lightning Protection' company, I remain skeptical. There are an awful lot of 'shoulds' and 'likelys.'

I want to see statistics. Not anecdotal evidence. And large database statistics take time to accrue. Give the MLP company 10 years, and then lets look at the evidence.
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  #19  
Old 08-08-2011
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Quote:
Originally Posted by RichH View Post
That noted and eminent 'lightning professor' from FSU is now retired ...
Absolutely unrelated to the thread, but PLEASE don't confuse the fine, prestigious University of Florida located in Gainesville with that nest of criminals, ne'er-do-wells and general hooligans located in Tallahassee attending the so-called Florida State University. On behalf of the entire Gator Nation, I thank you...

Now back to the main discussion, carry on.
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Old 08-09-2011
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I have an idea I'd really like to test, but no one seems willing to donate their boat to science. You know if you were designing a conductor to handle lightning you'd really have to work to find something better than a large diameter aluminum mast! It an almost perfect lightning conductor because high voltage electrons only flow on the skin of a conductor, not down the center. Stop at a substation and look at all the large diameter round bare conductors tying all the switches and transformers together. They are all thin wall hollow tubes.

The bad crap happens when the lightning gets to the end of the perfect conductor and finds a whole bunch of high impedance connections that can't carry all that power. So it arcs, jumps all over the place and does all kinds of damage.

But what if it had a path just as good right into the water? What if instead of a cable you got a length of thin cooper or aluminum flashing and attached it to the mast by bending it around the mast and fastening it with stainless hose clamp. Then toss the loose end over board, maybe with a weight on the end, and keep all the bends very gentle. Now the lightning has a large surface conductor capable of carrying all the energy of the strike.

I came up with idea years ago when I was an electrical contractor. One of my best customers was having huge problems with their computers due to interference from high voltage high frequency induction furnaces used to grow germanium crystals in the same building. They had us install a 4' x 8' galvanized steel sheet in the ground outside the building. Then every induction furnace was connected to the plate by a horridly expensive 2" wide braided flat copper cable bolted the frame of each furnace. I was skeptical, but like magic all the interference problems went away!

If you live aboard and only move occasionally then this setup could be cheap insurance. Anybody got a boat to test it on?

Gary H. Lucas
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