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08-07-2019, 05:49
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#16
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,242
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by sanibel sailor
Lightning does respect conductors all that much. Remember that it just hopped across a thousand feet or more of air which is generally considered pretty nonconductive. Concepts that make sense for 12 or 240 volts break down when the voltage is in the billion range. My boat has a grounding system as well as a lightning rod at the masthead, but I don't count on it to do much. The overpriced brush style dissipators are worthless. NASA says a rod with a 3/16" rounded tip is most effective and they have a bunch of really smart people protecting a lot of really expensive really tall toys in a really high risk area.
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The dielectric strength of air is quite high however when it's breakdown voltage is exceeded by the static charge built up in the thunderstorm, this air becomes ionised and it's resistance is greatly reduced which allows the current (strike) to flow. The resulting huge EM field is the thing that causes most of the electronics nearby to fail.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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08-07-2019, 06:01
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#17
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Registered User
Join Date: Aug 2011
Location: Melbourne Australia
Boat: Paper Tiger 14 foot, Gemini 105MC 34 foot Catamaran Hull no 825
Posts: 2,912
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by Wotname
Ahh, no... Aircraft are very affected by lightning. Bits and pieces of the fuselage go missing after been struck and a full inspection has to be carried out - it was part of my previous occupation to do such inspections. It is true their electronics are rarely affected but this is due to the design and installation methods that are employed.
Normally a definite entry and exit point can be identified!
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Im always learning something new, Not having any thing to do with flying aircraft, I didnt know that bits and pieces fell off them,
At least they dont usually fall out of the sky,
I also wonder how many boats have sunk when the Thru hulls have been blown out,
Thats also a newie to me, I havent heard that comment before,
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08-07-2019, 06:10
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#18
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Registered User
Join Date: Apr 2014
Posts: 23
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by Mr B
Considering an aluminium mast is just standing there on a Fibreglass boat and is not connected to ground or earthed out in any way,
Why would it attract a lightning strike, ???????????
On anchor with a chain out, Yes then your earthed out,
Very small gap between your anchor chain and the front Guy wire for your mast,
Would it not be the same as an aircraft getting hit by lightning,
Its a large aluminium structure flying through the air and not earthed or grounded out,
They seem to be uneffected by lightning strikes,
Their electronics and wiring dont short out or melt when hit by lightning,
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Your mast is a shorter path (lower resistance) through the air on the way to the ground, just like airplanes fuselages are.
And lightning likes big low impedance conductors (lightning is effectively RF energy) like masts, not small high impedance conductors like shrouds.
Fuselages are fairly safe because because it's a faraday cage, RF travels on the outsides of conductors not through them. Since all of the electronics are inside the cage, you're good.
But a mast/conductor that ends before it hits ground suddenly presents a high impedance, and the energy then bleads to every lower impedance path to ground (your electronics which have wires closer to earth potential..) until the potential becomes so great it arcs through whatever air gap/GRP is in between it and earth.
Sean
WK7R
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08-07-2019, 06:20
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#19
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Registered User
Join Date: May 2019
Location: Longboat Key, FL
Boat: 42' Chung Wua Trawler
Posts: 80
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by Mr B
Considering an aluminium mast is just standing there on a Fibreglass boat and is not connected to ground or earthed out in any way,
Why would it attract a lightning strike, ???????????
On anchor with a chain out, Yes then your earthed out,
Very small gap between your anchor chain and the front Guy wire for your mast,
Would it not be the same as an aircraft getting hit by lightning,
Its a large aluminium structure flying through the air and not earthed or grounded out,
They seem to be uneffected by lightning strikes,
Their electronics and wiring dont short out or melt when hit by lightning,
Its a totally different story if your mast is connected to the water in some way, Welding wires over the side into the water attached to the mast,
Then the mast is and will be grounded out,
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Mr. B.,
Masts definitely attract lightning. They do this through charge accumulation. When it gets really bad you can actually see it as a glow at night.
From Wikipedia (St. Elmo's Fire).
"Sharp points lower the necessary voltage because electric fields are more concentrated in areas of high*curvature, so discharges preferably occur and are more intense at the ends of pointed objects."
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08-07-2019, 07:05
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#20
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Registered User
Join Date: Sep 2015
Posts: 81
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Re: Lightning Protection, pros and cons
Ok, so from this I’ve followed the path of lightning from the storm, through the sky, through the mast and then...
BUT, when the mast ends and it’s grounded to a ground plate in the keel, where does it go from there? How does this dissipate the electricity? Is the ultimate goal to give it a path to water?
And selfishly, what happens with aluminum boats? I’ll google that, but wonder if there is first hand knowledge here.
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08-07-2019, 07:07
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#21
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Registered User
Join Date: Feb 2013
Location: Oregon
Boat: Seafarer36c
Posts: 5,563
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Re: Lightning Protection, pros and cons
[QUOTE=Mr B;2926062]
Would it not be the same as an aircraft getting hit by lightning,
Its a large aluminium structure flying through the air and not earthed or grounded out,
They seem to be uneffected by lightning strikes,
Their electronics and wiring dont short out or melt when hit by lightning,
Picture a helicopter getting hit. The bolt hits the main blade, down thru the rotor head, arcing damaging each bearing and gear surface on the way thru the transmission. Down the tail rotor shaft, thru the 45deg gearbox, the 90 deg gearbox and out a tail rotor blade. That is a lot of damage.
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08-07-2019, 07:13
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#23
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Lightning Protection, pros and cons
Quote:
Originally Posted by Mr B
Im always learning something new, Not having any thing to do with flying aircraft, I didnt know that bits and pieces fell off them,
At least they dont usually fall out of the sky,
I also wonder how many boats have sunk when the Thru hulls have been blown out,
Thats also a newie to me, I havent heard that comment before,
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Often it’s a dime sized hole in an airplane, and lightning is a very, very large problem for composite aircraft, used to be the fix was a screen wire layer inside of the composite, this wire layer is also needed for EMI/EMC. I assume it still is.
Most of our boats are composite, I assume a metal boat would be far superior to resisting damage to a strike, like a metal airplane is.
Lightening grounds are very common in the Sportfishing world, they consist of a #2 or larger wire connected to the aluminum structure on top of the boat and carries down to a large plate on the outside of the hull, usually larger than a dynaplate.
Plus it’s not unheard of for boats to be totaled from lightning making small but numerous holes in a fiberglass hull, with no metal involved, or a hole being blown thru the hull and the boat sunk.
It’s not unheard of for that plate to be blown off, or the #2 ga wire vaporized. On our Sprtfishing boats during a storm we would stay away from that metal cage, from fear of being zapped.
Often also lightning will magnetize any ferrous metal in the object that was struck, and of course ruin a compass.
I maintain that nothing works, and if it did don’t you think Insurence companies would either recommend or give a discount for a system?
Or all the “good” boats would come with protection systems, I’m actually surprised that’s not an option, good profit potential.
There are two schools of thought, prevent being hit and give it a place to go, and then there is the argument that giving it a place to go increases the likelihood of being hit.
Does it, I think it might, who knows? Supposedly bonding all the thru hulls together helps protect from lightning, but I don’t know how.
Everything on my boat is bonded and it’s supposedly to help protect from damage during a strike, does it work? Who knows.
I used to leave a section of SS chain hanging from my shroud in the water.
Lightning protection is a lot like bonding thru hulls, both ways seem to work, bonding or leaving unbonded, which is the right way?
Lighting does as it wants to and does not seem to always follow any logic that I can see, it seems often to just be random, like striking a dock surrounded by sailboats or something.
Although it does seem to usually go for taller objects, usually.
Lightning I believe is formed from the ground up, and whatever leader connects first completes the circuit and bam there is a strike, that I think may explain the randomness, occasionally a leader from the ground may connect before one from a taller object.
There are odd things about lightning, like why are Cats more likely to be struck than Monos statistically and I believe corrected for population density.
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08-07-2019, 07:17
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#24
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Registered User
Join Date: Aug 2013
Location: Oakland, CA
Boat: Freedom 38
Posts: 2,503
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by noelex 77
Carbon masts do not fare well. The combination of higher resistance and lower heat tolerance means they are easily destroyed, often in a spectacular fashion.
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I'd be interested in the literature on this statement, too. Especially the "spectacular fashion" part. Seems this is said a lot but can't find much evidence it is actually true.
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08-07-2019, 07:23
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#25
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Lightning Protection, pros and cons
I had a helicopter struck on the ground, the ingress point was the #1FM antenna on the top of the tail. This antenna was fiberglass, after being struck it looked like some kind of hair, there was nothing left of the resin, but the fibers some of them were still there, and four ft or so of antenna was like a bunch of hair.
Composite parts on an airplane have been known to literally explode / vaporize if they don’t have the screen mesh wire in the layup.
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08-07-2019, 07:23
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#26
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Registered User
Join Date: May 2019
Location: Longboat Key, FL
Boat: 42' Chung Wua Trawler
Posts: 80
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by a64pilot
Often it’s a dime sized hole in an airplane, and lightning is a very, very large problem for composite aircraft, used to be the fix was a screen wire layer inside of the composite, this wire layer is also needed for EMI/EMC. I assume it still is.
Most of our boats are composite, I assume a metal boat would be far superior to resisting damage to a strike, like a metal airplane is.
Lightening grounds are very common in the Sportfishing world, they consist of a #2 or larger wire connected to the aluminum structure on top of the boat and carries down to a large plate on the outside of the hull, usually larger than a dynaplate.
Plus it’s not unheard of for boats to be totaled from lightning making small but numerous holes in a fiberglass hull, with no metal involved, or a hole being blown thru the hull and the boat sunk.
It’s not unheard of for that plate to be blown off, or the #2 ga wire vaporized. On our Sprtfishing boats during a storm we would stay away from that metal cage, from fear of being zapped.
Often also lightning will magnetize any ferrous metal in the object that was struck, and of course ruin a compass.
I maintain that nothing works, and if it did don’t you think Insurence companies would either recommend or give a discount for a system?
Or all the “good” boats would come with protection systems, I’m actually surprised that’s not an option, good profit potential.
There are two schools of thought, prevent being hit and give it a place to go, and then there is the argument that giving it a place to go increases the likelihood of being hit.
Does it, I think it might, who knows? Supposedly bonding all the thru hulls together helps protect from lightning, but I don’t know how.
Everything on my boat is bonded and it’s supposedly to help protect from damage during a strike, does it work? Who knows.
I used to leave a section of SS chain hanging from my shroud in the water.
Lightning protection is a lot like bonding thru hulls, both ways seem to work, bonding or leaving unbonded, which is the right way?
Lighting does as it wants to and does not seem to always follow any logic that I can see, it seems often to just be random, like striking a dock surrounded by sailboats or something.
Although it does seem to usually go for taller objects, usually.
Lightning I believe is formed from the ground up, and whatever leader connects first completes the circuit and bam there is a strike, that I think may explain the randomness, occasionally a leader from the ground may connect before one from a taller object.
There are odd things about lightning, like why are Cats more likely to be struck than Monos statistically and I believe corrected for population density.
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I recently read that cats get hit more often because of thier distance from other boats. They are often on end ties and thier beam also places them further away. Who knows. Maybe
I suspect that the beam, surface area, and the fact that the mast is deck stepped may also play a part, but I am just theorizing.
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08-07-2019, 07:28
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#27
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Registered User
Join Date: Apr 2014
Posts: 23
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Re: Lightning Protection, pros and cons
Quote:
Originally Posted by fschaefer4
Ok, so from this I’ve followed the path of lightning from the storm, through the sky, through the mast and then...
BUT, when the mast ends and it’s grounded to a ground plate in the keel, where does it go from there? How does this dissipate the electricity? Is the ultimate goal to give it a path to water?
And selfishly, what happens with aluminum boats? I’ll google that, but wonder if there is first hand knowledge here.
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The ultimate goal is to give it a low impedance path to the surface of the water in seawater. Since RF wants to travel on the surface of conductors (including seawater), the lower in the water it exits the boat, the higher the impedance path to the surface becomes. Lighting will always find the lowest impedance path to earth potential -- your job is to make the desired path lower in impedance than the undesired paths. 1 foot to the waterline is far more desirable than 4 feet.
And aluminum boats would fair far better than GRP boats in lightning so long as the mast is bonded to the deck and the deck is aluminum and welded/bonded to the hull, surface effect should protect everything inside the boat as the whole boat rose and fell together in potential. Though I wouldn't want to be standing on the deck of one with my feet apart when it happened, I'd feel better about that than being on/in a GRP boat when it happened.
Sean
WK7R
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08-07-2019, 07:33
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#28
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Registered User
Join Date: Dec 2014
Location: On a sphere in a planetary system
Boat: 1977 Bristol 29.9 Hull #17
Posts: 730
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Re: Lightning Protection, pros and cons
The From everything I have read there is no Definitive way reduce or keep lightening from striking ones boat. If there was it would be very expensive, and we would all already own it, and some entity would have gotten very rich had it been produced. It appears to be a luck of the draw sort of thing when it comes to lighting strikes.
Sure wish such a system existed though.
Fair winds,
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08-07-2019, 07:37
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#29
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Lightning Protection, pros and cons
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08-07-2019, 07:40
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#30
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Registered User
Join Date: May 2019
Location: Longboat Key, FL
Boat: 42' Chung Wua Trawler
Posts: 80
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Re: Lightning Protection, pros and cons
There is this. They claim no strikes in 15 years but I am not sure how many boats are in thier sample.
https://www.empdefense.us/?gclid=Cjw...BoCec4QAvD_BwE
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