Lighting strike on an all electric boat????

[nwdiver]

Originally Posted by AedanC

I’m very interested in that aspect, do you have any photos of the faraday cage?

It's a soldered 1/8 inch copper box with an inset lid, on the inside is aluminum diamond mesh then a 3/4 inch closed cell foam....if a microwave works it will work better....

[Dave_S]

I was given advice to drop the anchor into the water if lightning was around. I was thinking with the anchor locker at the base of the mast it would be a simple job to connect the mast to the chain guide and create a connection. Could also create a connection to the front stay.

Any thoughts ?

[BigBeakie]

Chain is not a good conductor because there is not enough contact surface between the links.

Lightning is "trying" to get to the surface of the water, not down into the water. So having several conductors at or very near the waterline are required, with correctly sized conductor wire between them and the mastbase.

See excellent information at www.marinelightning.com



Sent from my iPad using Cruisers Sailing Forum

[boatpoker]

I'm no expert but I have taken a couple of courses and handled a number of lightning damage claims on boats without and with various types of lightning protections systems.

My conclusion is that up to 200,000amps moving on the return flash at about 1/3 the speed of light does not care about any of your protection systems or devices. All such systems are built on "theory" with no substantial proof behind them. Research on strikes on water is very thin, research on fresh water strikes is almost non-existent.

[coopec43]

Originally Posted by boatpoker

My conclusion is that up to 200,000amps moving on the return flash at about 1/3 the speed of light does not care about any of your protection systems or devices. All such systems are built on "theory" with no substantial proof behind them. Research on strikes on water is very thin, research on fresh water strikes is almost non-existent.

I understand where you are coming from. Even the "experts" don't fully understand lightning - why lightning is attracted to sharp/pointy edges and (for example) why most hull damage occurs at or near the water line.

But statistics can be a guide : the risk of a lightning strike at a particular place in the world, 90% of strikes are on high objects.........

"A system designed in compliance with a standard does not guarantee 100% immunity from damage. Lightning protection is an issue of statistical probabilities and risk management. Lightning protection systems designed in compliance with standard should statistically reduce the risk below a pre-determined threshold."(Marten Havelka)

I have lightning protection as anything that improves my chances is a plus. (My TV aerial has been hit and my neighbor's lobster boat has been hit)

Clive

[Montanan]

Originally Posted by nwdiver

I was also thinking of synthetic rigging.....this would make my mast the only way to the water

Subject of a previous thread.

http://www.cruisersforum.com/forums/...ons-21574.html

[Paul L]

Originally Posted by BigBeakie

Chain is not a good conductor because there is not enough contact surface between the links.

Lightning is "trying" to get to the surface of the water, not down into the water. So having several conductors at or very near the waterline are required, with correctly sized conductor wire between them and the mastbase.

See excellent information at Marine Lightning Protection Inc.



Sent from my iPad using Cruisers Sailing Forum

Chain may not be a great conductor, when it comes to lightning it will conduct a lot of energy. A friend's boat was hit while at anchor near us in Costa Rica. He had a shiny, polished stainless steel bruce anchor. When he hauled the anchor one side was nice and shiny. The other side was heated metal rainbow colored along the whole side.

They were off the boat when the hit occurred. They went onboard and at first couldn't figure out why the floor boards were scattered in the cabin and on the settee. Thought is the bilge water boiled and blew the floor boards out.

[Paul L]

Originally Posted by Paul Howard

I know from personal experience that lightning strikes when far at sea kills everything. Batteries burst, inverter and circuit breaker panel nothing but melted wiring. LED lighting burns out, even bilge pumps had to be replaced. The engine the system was grounded through (on a catamaran with twin engines) was toast, thought the second engine with its own isolated system did work after the strike. The only thing that still worked was a handheld VHF.
Autopilot, compass light, refrigeration, even the solenoid for the propane cooking stove was all gone. Took three days to get to nearest port plotting a DR on a paper chart and using small LED flashlight while hand steering to light the compass. Not fun at all.

Sounds brutal. Where were you and how far to safe harbor?

[coopec43]

A friend of a friend was in a 40ft fishing boat 30 mile off the West Coast of Australia. They were hit by lightning. The plastic instrument blew up and sprayed molten plastic over one of the guy's face, all the wiring had melted so they couldn't start the motor or use the radio.

Luckily the only boat in the area (on the horizon) saw them get hit and came to their aid. I suppose they could have used the flares if another boat came into sight otherwise the boat would have washed up in Africa about three months later with two skeletons on board.

Clive

PS Why is it that multi-hulls get hit more often than mono hulls? Do they know?

[44'cruisingcat]

Originally Posted by coopec43

PS Why is it that multi-hulls get hit more often than mono hulls? Do they know?

Some theories are that a greater proportion of multis inhabit the tropics and that they may tend to anchor in shallower water.

[GordMay]

Originally Posted by coopec43

I understand where you are coming from. Even the "experts" don't fully understand lightning - why lightning is attracted to sharp/pointy edges ...

Actually, it's not. Rounded tips are more attractive.


“... An examination of the relevant physics shows that very strong electric fields are required above the tips of rods in order that they function as strike receptors but that the gradients of the field strength over sharp-tipped rods are so great that, at distances of a few millimeters, the local fields are often too weak for the development of upward-going streamers. In field tests, rods with rounded tips have been found to be better strike receptors than were nearby sharp-tipped rods ...”
~ Charles B. Moore, Langmuir Laboratory for Atmospheric Research, New Mexico Institute of Mining and Technology, Socorro, NM

https://journals.ametsoc.org/doi/ful...L%3E2.0.CO%3B2

[coopec43]

[QUOTE=GordMay;2801948]Actually, it's not. Rounded tips are more attractive.
In field tests, rods with rounded tips have been found to be better strike receptors than were nearby sharp-tipped rods ...”
~ Charles B. Moore, Langmuir Laboratory for Atmospheric Research, New Mexico Institute of Mining and Technology, Socorro, NM

QUOTE]


Now I am confused........

I quote from a science paper written in 2014.

A fundamental principle of static electricity is that all objects emit charges through the process of ionization, and sharp objects emitcharges faster than flat or rounded planes. This partly explains why lightning strokes hit corners and sharp points of a building more often than the flat sides.


That is why I have ground strips as opposed to plates as there are more sharp edges on a strip than a plate.

When I get a chance I will do more research........

Clive

[Dirk01]

What about Aluminum boats? Are they better protected? Are they more or less closer to a Farraday's cage? As far as I know current at high voltage flows over the surface (most of it). And hopefully discharge directly into the water...

[coopec43]

Originally Posted by GordMay

Actually, it's not. Rounded tips are more attractive.

In field tests, rods with rounded tips have been found to be better strike receptors than were nearby sharp-tipped rods ...”
~ Charles B. Moore, Langmuir Laboratory for Atmospheric Research, New Mexico Institute of Mining and Technology, Socorro, NM

This makes for fascinating reading.

A Malaysian woman changed the world’s view on lightning, but what did she discover anyway? Badd — 25/03/2018

https://cilisos.my/a-malaysian-woman...scover-anyway/


Robiah's method, later known as the Collection Surface Method (CSM), is based on the observed lightning damage to buildings instead of power lines. It allows engineers to predict lightning strike locations on a building and design an effective lightning protection system by placing lightning rods at the predicted locations – a technique which was never before developed by any scientist



Clive

[GordMay]

Originally Posted by coopec43

... Now I am confused........
... That is why I have ground strips as opposed to plates as there are more sharp edges on a strip than a plate.

Blunt or rounded (but not flat) Air Terminals have been shown to be slightly more effective than sharp Lightning Rods, because they have lower breakdown voltages, and longer time to breakdown compared, to other air terminals*
The results of studies suggest that moderately blunt metal rods (with tip height–to–tip radius of curvature ratios of about 680:1) are better lightning strike receptors than are sharper rods or very blunt ones.
Dr. Charles B. Moore et al, reported* that the electric fields above the blunter rods were as much as two times stronger over greater distances than those above the sharp rods. This, he said, ''can be significant in the possible interception of an approaching lightning streamer.''
Moreover, Dr. Moore said, “the sharp rods create around their tips a dense sheath of electrified, or ionized, particles, which reduce the probability of lightning's striking the rod. In so protecting itself from lightning, instead of drawing it, the rod is not as likely to fulfill its intended function of diverting lightning from other exposed objects in the vicinity. “

Goto: Lightning Rod Improvement Studies
By C. B. Moore, William Rison, James Mathis, and Graydon Aulich
Langmuir Laboratory for Atmospheric Research (New Mexico Tech)
➥ https://journals.ametsoc.org/doi/abs...-0450-39.5.593

The most recommended lightning ground electrode is a long strip, perhaps 4" wide x 1/4" minimum thick, and 36" minimum long, installed on the outside of the hull, from the base of the mast, leading aft. The ends should be secured with two fasteners, to prevent “twisting” under dynamic loading. Strips are recommended due to their increased “edge length”, which form better attachments than flat surfaces. Do not fair the edges, but allow them to remain in “sharp” contact with the water.

➥ http://www.cruisersforum.com/forums/...late-2428.html

Ewen M. Thomson has patented a new electrode geometry, claimed to be more effective.
Goto ➥ Marine Lightning Protection Inc.
and see the patent at:
➥ http://www.marinelightning.com/USPTO...708638_001.pdf