Lightening...again

[DocBrauer]

Hi Dale.
My monohull was previously owned by an electrical engineer. He put a large copper plate on both sides of the hull. He attached a large cable from one to the mast and to the other he attached the forestay. I don't have his knowledge so will keep as is.

Keith

[cyan]

Originally Posted by DocBrauer

Hi Dale.
My monohull was previously owned by an electrical engineer. He put a large copper plate on both sides of the hull. He attached a large cable from one to the mast and to the other he attached the forestay. I don't have his knowledge so will keep as is.

Keith

There is some recent research indicating that a grounding plate near the waterline has a much more significant effect than the same plate at the hull bottom.

[GordMay]

Originally Posted by cyan

There is some recent research indicating that a grounding plate near the waterline has a much more significant effect than the same plate at the hull bottom.

According to Ewen Thomson (Marine Lightning Protection Inc.), “... the key to reducing sideflash likelihood is to distribute the lightning current into the water from multiple sources. Since using multiple immersed ground plates is impractical, and the optimum location for exit terminals is close to the waterline, MLP has developed the new patented SiedarcTM electrodes that can be faired into the hull to reduce drag and require only a single hull penetration. Further, they are preferably installed above the waterline, thereby eliminating galvanic corrosion.”
➥ Siedarc electrodes

“... Although these spark-promoting electrodes offer new possibilities for grounding, the pragmatic approach is to use them in combination with, rather than instead of, more standard ground plates...”
➥ http://www.marinelightning.com/ProBoat.pdf

[AndyEss]

Originally Posted by Sojourner

Because lightning can start at the ground as well and travels upward. Feelers come both up and down from the cloud. The big visible bolt doesn't come until two feelers meet. The bottom part feeler comes up from your mast, your head, a tree, etc. So I believe yes, a small air gap can prevent the bottom feeler, and then the big blast is less likely to come.

Interesting.

I have, so far, been lucky and have yet to have been struck by lightning - body, homes, boats, cars ( or flying in commercial airplanes).

I hope never to have a more intimate experience with several hundred thousand Volts of lightning, greased or ungreased.

It is my understanding that the metal body of an automobile forms a Faraday cage and protects whatever is inside from damage.

The rubber tires have nothing to do with this protection.

I hope my luck continues.

[Group9]

Originally Posted by AndyEss

Yet lightning travels 1000s of meters through the air to release its potential energy.
Our tall, conductive masts make excellent short cuts for lightning to travel those last 10s of meters.
As a side note, I am always amused when friends say the reason why automobiles are safe in lightning storms because they sit on non-conductive rubber tires. Not sure why anyone would think that a 15cm of tire air gap poses any block to electrical energy that has already leaped probably through kilometers of sky

I worked for a power line company one summer. One lesson I learned was that everything conducts electricity if the voltage is high enough.

We had only one lightning strike on our sailboat that we knew about. It vaporized our masthead VHF antennae (and the VHF radio never worked again) and anchor light. No other damage (although we did replace the VHF wire going up the mast as well). Our mast and rigging was bonded to our lead keel, but I'm not sure how much of that really matters when it happens.

The other funny thing, was that there was a sailboat near us in our marina, with a mast a good fifteen shorter than ours, that got hit four times in the two years we were at that marina, and we only got hit that once.

[Checkswrecks]

Originally Posted by daletournier

I do wonder how any cable we could possibly add could provide a adequate path for the tremendous amount of current and voltage a lightening strike would contain, to me it would be like trying to push a swimming pool amount of water through a garden hose in microseconds. 10,000-200, 000 amperes .

The cable just provides a low resistance path for the power to follow. With the voltage and amperage in a lightning discharge, the air around the cable will become an ionized channel. And the path doesn't need to cost much or be as heavy as a set of jumper cables, you could simply put an alligator clip on something like an 8 AWG wire or heavier.

btw - I wouldn't bother doing more than protecting the electronics if the boat is mast stepped to a lead keel, because the path is already built in.

One either thought about IF a boat gets struck or as others have mentioned, a strike has even been close. Every circuit, instrument, and light will need to be checked for function. Don't be surprised if the diodes are blown in alternators or LED lights. It'd suck to start out on a passage a month later and find the coffee maker is inop.

[Jim Cate]

btw - I wouldn't bother doing more than protecting the electronics if the boat is mast stepped to a lead keel, because the path is already built in.

In the real world, few masts are actually stepped in contact with an external ballast keel, despite their being called "keel stepped". there is almost inevitably a hull in between mast and keel, and usually some other structure constituting the step.

For instance, on our boat the heel of the mast sits upon an aluminium weldment which in turn is bolted to a massive timber "H" beam, wrapped in glass and epoxy, and that sits upon the internal thin glass layer over the actual timber hull with it's external glass layer. The steel shell of the fin keel is bolted through hull and H beam, and when I feel the need for a lightning ground I run a heavy cable from the heel of the mast to a keel bolt. Without that, our mast is effectively as electrically isolated from the keel as if it were deck stepped.

I believe this is just as true for most fibreglass hull boats.



Jim

[DocBrauer]

As mentioned my copper plates are on sides of boat not bottom. They are about 2.5 ft below waterline though. They are 4ft x 1ft x 3/8 in

[hernandobeach]

"Montanan" is correct about the contact of the chain. I can only tell you what has worked in the past and is recommended by experts in lightning damage mitigation. I will also touch on some areas suggest by others.

#1 Lightning is nature's version of a difference in potential. It is a charge (most are positive but some are negative) that seeks to equalize the difference in potential. #2 Lightning takes any and all paths when it strikes an object. Most of the energy is DC, however there are some higher frequency elements within it. #3 Ohm's Law I = E/R tells you that the majority of the energy of lightning will seek the less resistance path. I could go into detail, but the energy or current is developed over the lowest resistance path. #4 It is wise to give lightning a path as when it is not given a low resistance/impedance path it will often seek paths you would prefer it not take. Such as the bond through the hull of the boat to the anode!

Over the past 50+ years I have witnessed numerous strikes on boats and investigated a number for insurance companies and manufacturer's of boats. Power boats and sail boats face the same issue, how to provide a highly conductive path around what they care about and avoid as much damage as possible. Lightning does not always strike the tallest object. What is will do is choose to expend the majority of it's energy following the most conductive path.

The addition of conductive elements to shunt the energy into the water is proper. In the case of a larger sail boats with a mast (metal or wood) it will have guys or rigging that a "stainless wire rope" and that will be connected hull with "chain plates" as well as to the bow and stern. These wires and the mast will support the flow of energy. The proper protection is to continue the path of the stainless wire rope into the water. That will shunt the majority of the energy away from the core of the boat.

Power boats with towers as part of their rigging have the same issue. The connection to the metal of the tower at the base of the tower, where it is connected to the boat is the correct point for the "conductor" placed in the water. The key elements are a substantial, large surface area contact between the tower in this case and the conductor. This can be difficult to accomplish if the boat is moving and most often is only done when the boat is docked or at anchor.

In the case of sail boats with stainless rigging, the "grounding" wire I will call it will be connected "in parallel" for several feet (by mechanical fasteners) to the rigging cable. The grounding wire should be highly stranded, flexible and run as straight as possible into the water. If at anchor more wire can be put in the water. If the boat is moving less due to the contact issues with elements of the boat.

A facility (building) lightning protection system if properly designed and installed will shunt the energy of lightning strikes around the building structure's elements to earth. Some use building steel as the down conductor, and I vehemently oppose such installations..... the goal of adding the stainless cable into the water it to give lightning a path to a lower potential "0", the ocean or lake.

Remember, lightning does not like 90-degree turns. The only way to avoid all lightning damage is to be where there is none! Also, disconnect what you can (radio antennas, etc.) during a lightning storm.

I hope this helps.........

[limte]

Although we've had lightning strikes very close to us while sailing or motoring, we've never been hit; however, the house that we lived in for many years was hit a number of times. The house was on the top of a hill in an area in which lightning was frequent in the summertime. The roof of the house, along its peak, was equipped with several 8" long pointed copper rods of about 3/4" diameter. The rods were attached with crimp type clamps to 1" braided copper cables, which were run down the side of the house and attached to copper grounding rods driven several feet into the ground. An additional cable was attached to the copper tubing which carried the water from the pump to the house (the tubing was buried about 4' underground.


I experienced several direct lightning hits while I was in the house, and while alarming, the only damage amounted to a burned out circuit that controlled the interior light in the freezer. The hits were incredibly loud, and in one case there was a huge flash when the current traveled down to the buried water pipe, where I happened to be standing.


It the case of our house, it does seem that the grounding arrangement allowed the lightning to travel safely to ground. I have thought of connecting a spare piece of this braided copper wire to the mast and leaving it coiled up near the mast to be tossed overboard when lightning is near, but have not gotten around to it yet. I do have a setup with heavy duty jumper cables attached to a piece of chain, but I have doubted that the chain would effectively transfer a lightning hit to the water, so I have never deployed it. During lightning storms we generally engage the autopilot and go below.


Regards,
Bob S

[mark0978]

Lightning is about rebalancing charge. Ions that rise into the clouds can be positive or negative, and the ground can have a similar positive or negative charge. The purpose of a lightning rod is not to take the lightning strike, but to bleed the charge off before it can build up. The idea of jumper cables placed into salt water is very sound provided it is connected to the mast or other metal object that goes up into the sky. So while chains are nice and flexible, good conductors they probably aren't . Go with copper wire.

The sharper the point on the lightning rod, the better it is at bleeding the charge before it can build up. And all lightning does NOT come from above, sometimes it goes from the ground up to the clouds, all about rebalancing the charges.

Now for the joke:
Why do cats get struck more than monohulls? Hitting a moving target is much harder than a stationary one. Monohulls are rocking back and forth, sometimes quite vigorously, and cats are nice and stationary, like a tree. All that rolling back and forth probably shakes the electrons off the monohull with a great deal of seasickness. Obviously, they will look around and find a more stable platform to migrate to....

[Talos]

If you are looking for a product that can alert you when to deploy your Lightning Plan, you may find this of interest:

https://www.pmt-fl.com/talos/lightni...talos-sfd-1000

[GordMay]

Originally Posted by mark0978

... The purpose of a lightning rod is not to take the lightning strike, but to bleed the charge off before it can build up...
... The sharper the point on the lightning rod, the better it is at bleeding the charge before it can build up...

The purpose of a lightning rod IS to take the lightning strike.
It's impossible to dissipate (bleed) the charge.

It is commonly believed, erroneously, that a rod ending in a sharp point at the peak is the best means to conduct the current of a lightning strike to the ground. According to field research, a rod with a rounded or spherical end is actually better. The old sharp-pointed rod is not as effective as a rounded-tipped 1/2 inch to 3/4 inch diameter rod. The idea is that, as the negatively charged step leader from the cumulonimbus cloud above reaches down, its final path is determined when it reaches a point about 75 feet above the ground. At that point, streamers from the tallest objects in that 150-foot diameter sphere will reach out to make contact with the step leader. The energy streaming from the sharper-tipped lightning rod reaches out only a fraction of the distance as the energy streaming from a round-shaped rod.


N. Tesla knew this a hundred years ago.
Tesla Has New Pointless Lightning Rod (1918)
... Says, Dr. Tesla, “The efficacy of the ordinary lightning rod is to a certain degree unquestionably establisht thru statistical records, but there is generally a prevalent, nevertheless, a singular theoretical fallacy as to its operation, and its construction is radically defective in one feature, namely its typical pointed terminal.” In his new form of lightning protecting rod and terminal here illustrated, Tesla avoids all such points on the metal parts facing skyward, and uses an entirely different form and arrangement of terminals....
➥ https://teslauniverse.com/nikola-tes...-lightning-rod

[cblurton]

Originally Posted by Montanan

Okay, perhaps there is a bit of an English language barrier with the international nature of this forum but the correct word for this thread subject is Lightning, not Lightening.

First of all, this is not a criticism of you. I love language and its "proper" use, too, and I wish everyone would be more careful with its use. But for an international forum I think we should be generous in what we accept as "proper." After all, no language is static and all change over time, fairly rapidly too. Think of all of the words we no longer use (CD, cassette or a floppy disk) or have just recently started using (crowdfunding, bromance, butt-dial,and vaping).

If I can understand a word within the context of the discussion in an international forum that makes it "proper" to me and I won't correct the poster unless, of course, I happen to know they teach English!

Some more fun:


https://www.mentalfloss.com/article/...ally-over-time

[BBill]

[QUOTE=mark0978;3044189]Lightning is about rebalancing charge. Ions that rise into the clouds can be positive or negative, and the ground can have a similar positive or negative charge. The purpose of a lightning rod is not to take the lightning strike, but to bleed the charge off before it can build up. The idea of jumper cables placed into salt water is very sound provided it is connected to the mast or other metal object that goes up into the sky. So while chains are nice and flexible, good conductors they probably aren't . Go with copper wire./QUOTE]

That is exactly my understanding...bleeding static reduces strike attraction. As told to me by a high voltage electrical company owner with a sailboat next to me. I saw him holding a small handheld voltage meter against his alum mast one day. It was gusting 25ish and the meter (miliamps) would jump with static charge every gust. That charge was an attraction, voltage increased and lasted longer without a discharging wire in the water as measured. He had stories of windmill water pumps for cattle that got struck every couple yrs and destroyed until he ran braided cu wire from the top and down into a cu grounding rod driven into earth. They had gone 10 yrs without a strike after grounding. Ever since then (1976) I've put a wire in the water. This is same method done on buildings...bleed static to ground to avoid strike attraction.

I think it might be possible to bleed off a very small feeder strike without damage but that's what surviving boats you see are getting hit with. I looked at Cal 25 that was thought to be struck by a main bolt under sail. It melted the mast/boom/sails, blew the chain plates off, melted holes where bolts and through hulls were, blew the bolt on keel off, blew a door size hole in the hull and killed 2 people. No "grounding" system would have survived or even began to reduce the damage.