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  #11  
Old 01-19-2013
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Re: lightning advice

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Originally Posted by Frogwatch View Post
Having routinely worked with multi-million volt potentials, I disagree with some advice given here. One can minimize the probability of the strike going thru certain paths by offering a much better path and eliminating paths that you do not desire.
Most effective would be a very good lightning ground.

Shameless commercial plug:

My new company is now selling a lightning ground
Can you give me some actual data. Tests? not just hypothesis or ligic, actual real world tests?
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Last edited by Faster; 01-20-2013 at 02:39 AM. Reason: commercial plug removed from quote
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  #12  
Old 01-19-2013
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Re: lightning advice

Quote:
Originally Posted by Frogwatch View Post
Having routinely worked with multi-million volt potentials, I disagree with some advice given here. One can minimize the probability of the strike going thru certain paths by offering a much better path and eliminating paths that you do not desire.
Most effective would be a very good lightning ground.
as they say in the electrical world, it is not the voltage that kills you, it is the current.

Similarly, lightning damage is a result of the current flowing, quickly. Anything that impedes current flow at inrush currents of millions of amp, is going to cause problems. Whether a mechanical splice, or welding clamp or simply some corrosion of a mast to clamp connection, that is a "high resistance" bump that the current will eliminate as a path to ground. It may blow it to pieces, or in many cases simply arc/jump to a better ground.

The ability to provide a "better path" is the challenge if it is possible at all on a boat, especially since the cable sizes and connectivity options preclude using adequate gear and there is no easy path to "ground" so water becomes the next best path to sink the current.

There is no such thing as a good lightning ground on land, let alone on the water.

All that being said, it is your boat and you are free to spend as much as you like on widgets and gadgets and cable and chains. Before spending or doing - You may want to ask to speak with an insurance loss analysis person at your insurance company and see what they will allow to be installed on your boat, and still provide coverage.

Check the web for radio tower hits to see what "good lightning grounds" look like after the strike. Some are 40' deep ground rods, with 250/500 CM copper connections to screens and such, and still are vaporized. Others are just fine and sustain multiple hits yearly, ala the Empire State Building transmitter tower. That is my background.


fyi:
http://www.engineeringradio.us/blog/...d-ground-wire/

YMMV

Last edited by kd3pc; 01-19-2013 at 06:38 PM.
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  #13  
Old 01-19-2013
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Re: lightning advice

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Originally Posted by Frogwatch View Post
For long term use, I'd use silver epoxy to seal the connection to the mast against corrosion.
not to quibble, but if you are sealing the mast against corrosion, how then are you going to:

" It carries a #4 tinned Ancor cable with a welding clamp to attach to the boat. It should attach to mast at the boom level by twisting to get a good connection thru the oxidized aluminum."

I am missing something with these two?
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Old 01-19-2013
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Re: lightning advice

Appreciate the input. Spent time studying to be an e.e. at columbia u. before pursuing my ultimate career path - have some basic understanding of the engineering concepts. Appreciate comment about galvanic corrosion/elctrolysis. Appreciate kd3pc's posts as well. Surprising there is so little hard science and data about this issue. CE/ABYC rules seem aimed at preventing side flashes. Still wonder with encapsulated keel why it doesn't make sense to provide a low impedance, non ( or less) destructive pathway. Care about not having holes burnt thru the boat. care less about the e/m pulse destroying electronics. seems virtually all sites/articles I could find to date suggest with ground slightly higher chance of getting hit but much lower chance of sinking. Thought that came from pooled insurance data. Still will ask insurance vendor before installation. thanks for the idea kd3pc
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Re: lightning advice

Exactly how would one go about such testing? With lightning "diverters", it was sorta like saying they were also Elephant repellers until the escaped circus elephant jumped onto the boat with one. In a normal marina situation, the average boats strike probability is low..........unless you happen to be the isolated high mast.
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Old 01-20-2013
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Re: lightning advice

Quote:
Originally Posted by Frogwatch View Post
Exactly how would one go about such testing? With lightning "diverters", it was sorta like saying they were also Elephant repellers until the escaped circus elephant jumped onto the boat with one. In a normal marina situation, the average boats strike probability is low..........unless you happen to be the isolated high mast.
No silly, do be so condescending

I meant things like, is there an insurance discount on boats with certain protections installed. Their data would indicate a preference as they would pay less insurance claims to boats with lightning prevention . Do you knw any company which does this?

Surely you mut have some concrete evidence of benefits other than you words that adding some system to a boat for hundreds, maybe thousands of dollars will have any difference at all.

I can put alligator clips on by shrouds and run a 1 wire into the water for pennies. Do you any scientific data or proof you system or "invention" is any better.

Short of any data or proof there are many snake oil salesmen that will sell you lots of their own theories to make money..

BTW aren't their rules on posting Sailnet against selling services or products. Even if you identify yourself, I don't think posts are an appropriate place to do this.
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  #17  
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Re: lightning advice

from what I can gather.
risk ~ 4 per thousand per year. higher FLA carribean lower NE
double risk for multi hulls
no good statistics for sinking with solid glass v cored v wood v carbon fibre but consensus extremely low for metal hulls.
If grounded and in salt water ~12' of "edge" required ( theoretical not backed by fact). Higher if in fresh.

Boat is in construction phase where installation at this point would be easier/cheaper. Still very confused. Will hold off untl I have more concrete knowledge. Thanks for all the opinions given but think to date they are just that- opinions. Have calls into certified marine elctricians and await replies. Perhaps will post when I have some facts to offer the group. Tx. for your input.
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Re: lightning advice

I am enjoying reading you experts discuss this.
As one that is not educated in the field, Do you mind if I ask a question?

By providing as easier path, are you not inviting a strike?
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Re: lightning advice

Quote:
Originally Posted by sailortjk1 View Post
I am enjoying reading you experts discuss this.
As one that is not educated in the field, Do you mind if I ask a question?

By providing as easier path, are you not inviting a strike?
The consensus is that grounding slightly reduces the chance of strike.

Grounding reduces the charges that can accumulate at the masthead and attract the lightning.
The effect, however, is very small. The only real practical effect is to reduce the damage.
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Old 01-20-2013
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Re: lightning advice

Quote:
Originally Posted by outbound View Post
from what I can gather.
risk ~ 4 per thousand per year. higher FLA carribean lower NE
double risk for multi hulls
no good statistics for sinking with solid glass v cored v wood v carbon fibre but consensus extremely low for metal hulls.
If grounded and in salt water ~12' of "edge" required ( theoretical not backed by fact). Higher if in fresh.

Boat is in construction phase where installation at this point would be easier/cheaper. Still very confused. Will hold off untl I have more concrete knowledge. Thanks for all the opinions given but think to date they are just that- opinions. Have calls into certified marine elctricians and await replies. Perhaps will post when I have some facts to offer the group. Tx. for your input.
Let us know what you discover
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