What is this heavy copper cable?

[DougR]

Originally Posted by philcun50

I would like to from anybody who has had lightning protection such as this that has been struck by lightning. Did it do any good when after all there is so energy in lightning that it makes me wonder if those tiny little cables would be enough to defuse that energy?

Years ago I had a Tartan 30 with a keel stepped mast. There was a lightning ground wire from the aluminum mast step to the front keel bolt. This solid wire was somewhere between a #6 and a #4 (never measured it) and about 15” long. When the boat took a direct lightning strike to the top of the mast this ground wire fed the strike to the lead keel and into the water. There was no physical damage to the mast, ground wire, or keel, but the fiberglass VHF antenna on the top of the mast exploded and all the solid state electronics were toast.

[philcun50]

Originally Posted by boatpoker

No, it does not attract lightning. I've done a number of lightning strike investigations and yes they are pretty much useless as 3,000,000volts at 30,000amps and moving at 270,000mph will vaporize that conductor in an instant.

I was meaning the balls they put over buildings may attract lightning.
However you have confirmed what the guys told me as said before “lightning let’s us know how puny we are”. Why only 270,000mph?
I only know of one boat that was struck by lightning. I wonder how common it is?
Like wise how many boats have contact with whales.

[boatpoker]

Originally Posted by philcun50

I wonder how common it is?
Like wise how many boats have contact with whales.

it is geographic. Tampa Bay is a hotspot. Ontario is maybe 2 or 3 (boats) per year.
Venezuela is a real hot spot.

https://geology.com/articles/lightning-map.shtml

[MikeHoncho]

Take a listen to this Poscast
https://www.59-north.com/onthewindpo...90-jeff-thayer
It will enlighten you on the physics of lightening and decipher between myths and facts.

[hzcruiser]

Originally Posted by boatpoker

No, it does not attract lightning. I've done a number of lightning strike investigations and yes they are pretty much useless as 3,000,000volts at 30,000amps and moving at 270,000mph will vaporize that conductor in an instant.

While such devices are not likely to avoid damage from a direct massive hit, there are many more occurrences of nearby strikes or smaller hits where they provide, if nothing else, an additional path to the water. In either case, my assumption is they're neither useless nor fool/strike proof.

[s/v Jedi]

These bonding cables have been 100% effective for us. At least 3 hits that vaporized antennas and wind instruments at the masthead and no damage at the bonding wires nor grounding plates.

Also, I have checked and rechecked many such shore side installations on radar towers. A solid 3/8” copper conductor was used there and never any damage after lightning hit the rods at the top.

The amperages and voltages mentioned are correct but apparently so short lived that the conductors survive.

[FAST FRED]

"They don’t defuse energy. They channel it to ground instead of the strike choosing it’s own path, which often pokes holes in fiberglass hulls."


I wonder at the wisdom of bringing the strike inside the living spaces?

[johnn33]

Hi to boatpoker
Please could you post some photos of your lightning protection?
John

[GordMay]

The recommended lightning downconductor cable size, was increased from #6, to #4 AWG, some time ago.
A #6 AWG cable has a diameter of 0.1620 inches (4.115mm), or about 1/6Th of an inch.
A #4 AWG cable has a diameter of 0.2043 inches (5.189mm), or about 1/5Th of an inch.
My thumb, for instance, has a width of ±1".
A 750 MCM/kcmil cable has a diameter of 1.128 inches (28.77mm).

[Frankly]

Originally Posted by boatpoker

No, it does not attract lightning. I've done a number of lightning strike investigations and yes they are pretty much useless as 3,000,000volts at 30,000amps and moving at 270,000mph will vaporize that conductor in an instant.

The three million Volts is the cloud to water potential, on a well grounded mast the potential from mast head to water is more likely in the thousands Volt range. 270,000 MPH (this number is way low), in this case speed is your friend. Electrical conductors safely conduct strikes world over every day with little/ no harm.


Frankly

And thanks again to Gord for introducing the phrase "lightning mitigation". I went and changed my posts here and at IP Homeport to incorporate this much more accurate term.

[s/v Jedi]

Originally Posted by FAST FRED

I wonder at the wisdom of bringing the strike inside the living spaces?

Obviously the shroud and chainplate bring it inside. The bonding wire is to safely escort it out again.

Gord just wrote that the recommended size was increased from 6 AWG to 4 AWG which of-course is correct (he actually checks everything while I often have to add “iirc”). We have 4 AWG from the mast steps to the bonding plates and 6 AWG from chain plates to bonding plates. We also have 8 AWG from every winch, stanchion, pad eye etc. to the bonding plates. It appears that our builder (TPI, Newport, Rhode Island) used a variety of sizes for different bonding points, aiming for the bulk of the strike to come down the mast itself. Our build was certified by the American Bureau of Shipping in 1994.

[GordMay]

Originally Posted by s/v Jedi

... We have 4 AWG from the mast steps to the bonding plates and 6 AWG from chain plates to bonding plates. We also have 8 AWG from every winch, stanchion, pad eye etc. to the bonding plates. It appears that our builder (TPI, Newport, Rhode Island) used a variety of sizes for different bonding points, aiming for the bulk of the strike to come down the mast itself. Our build was certified by the American Bureau of Shipping in 1994.

Your mast is (or has mounted on it) the air terminal, so the #4 AWG, from mast base to grounding plates is part of the downconductor, requiring #4 cable.
The #6 from chain plates, and #8 from "other" (only immersed metals required, others recommended) metals, are part of your lightning bonding system, requiring #6 AWG wire (used to be #8).
Accordingly, your installation almost meets the CURRENT standards, IIRC.


Ewen Thomson addressed some of the issues, raised in this thread, in his 2007 IEEE paper:
“A New Concept for Lightning Protection of Boats - Protect a Boat like a Building”
➥ http://marinelightning.com/EXCHANGEOct2007Final.pdf

[GordMay]

Originally Posted by GordMay

Your mast is (or has mounted on it) the air terminal, so the #4 AWG, from mast base to grounding plates is part of the downconductor, requiring #4 cable.
The #6 from chain plates, and #8 from "other" (only immersed metals required, others recommended) metals, are part of your lightning bonding system, requiring #6 AWG wire (used to be #8).
Accordingly, your installation almost meets the CURRENT standards, IIRC.

Ewen Thomson addressed some of the issues, raised in this thread, in his 2007 IEEE paper:
“A New Concept for Lightning Protection of Boats - Protect a Boat like a Building”
➥ http://marinelightning.com/EXCHANGEOct2007Final.pdf

ABYC TE-4 “Lightning Protection” was Revised in July of 2019. I haven't seen it.

[and4ew]

Well fortunately for me I sail in Atlantic Canada where lightening is pretty rare compared to some areas south and on the Great Lakes.

Thanks for the contact info for Mike Gozzard, I will contact him.

[EwenT]

Originally Posted by boatpoker

No, it does not attract lightning. I've done a number of lightning strike investigations and yes they are pretty much useless as 3,000,000volts at 30,000amps and moving at 270,000mph will vaporize that conductor in an instant.

This is the conclusion I have come to as well. I no longer see the point in drilling multiple holes below the waterline to attach something that has questionable scientific support. If you could document where the lightning does exit and other evidence of discharge paths then this would be a valuable source of data. For example, your mention of conductors vaporizing indicates that significant charge passed through these conductors, and so is indicative of the discharge mechanism. Further, since beefy copper conductors (4 AWG and larger) are more than sufficient to dissipate the heating energy from a typical lightning current, the connection may be the problem in this case.