Lightning prevention system.

[Frankly]

On my roof system, the ground system consists of a ground rod (right below the roof drip line) and then over to the chain link fence running along the property boundary (some real surface area). Bonding conductor back to the electrical service ground (minimize common mode potential).

Certainly the marine situation we find our self in is between the cloud and surface of the ocean, just that the surface is not convenient (unless you want a bunch of copper wiring draped around the salon). Look at Dr Thompson's "side arc" system. So we make a compromise and get to the sea in the shortest most direct path possible. Reasonable compromise for most IMO.

With a well ocean connected aluminum mast I am not convinced the potentials are so awfully high on the yacht. Once the attachment is complete and the current starts to flow Ohms Law takes over. 10,000 amps over an impedance of 1 Ohm is just 10,000 volts. Note: the one ohm is a via rectumus number, I tried once to calculate the impedance of a 6" aluminum round tube at 1 Mhz (way above my pay grade).

Life is full of compromises.

[bdgWesternMass]

Originally Posted by smj

So on a catamaran would it be good practice to run the cable from the LM through the bridgedeck and directly into the water?

This product page describes there approach.

Catamarans

[smj]

https://loosecannon.substack.com/p/n...PBmacAWe9g&s=r

[HighTemp]

Recently, we took a direct strike. Typical lightning damage. All nav electronics/ radios toasted, 4 inverters, both alternators, 2 LifePO4 batteries, MDI's and one tachometer, 2 air conditioners, freezer, all 6 bilge pumps, TV's, stereo, and every LED light on the boat including the ones backlighting the rocker switches on the 12V panel. Even the standing rigging had to be replaced. Thus, the reason I decided to read through this thread.

My take away is that while I agree, there is no guaranteed way to prevent a strike, I nonetheless have decided to give it a try. Given the time, associated frustration and very considerable expense required to recover from the event, the price of one of these ion dissipation systems is worth something, if only just a small amount of peace of mind. Short answer is that it can't hurt.

Funny thing is that I'll never know if it actually works, only if it fails to do so. I can accept that. If we never get hit again, I'll chalk it up to the device, and if we do, then I'll add its purchase to the long list of questionable spending decisions I have made in the past.

[team karst]

Ouch. Sorry to hear. Any idea of strike path? Sailcat?

[HighTemp]

Yes. It struck the VHF antenna and made its way down via the cables in the mast and through the N2K data buss and Ethernet network to the rest of the instruments. Nothing survived. It also travelled down the standing rigging and apparently out through either the sail drives or grounding plates. No hull damage that we can find thus far. Given that my inverter / chargers got popped, it would appears that it also traveled through the shore power path to ground. Just found out that the meter on the power pedestal had been destroyed too. Not getting an electric bill from the marina for two months was the only bright spot...lol. So basically, it took every possible path to ground...including the 12V side.

[fxykty]

With all synthetic rigging other than an aluminium mast that terminates on a thick slab of fibreglass on our main beam, what possible path to ground is there for a strike to our masthead?

Would it be the two big LMR400 cables from the two masthead antennas that will conduct the strike energy through to the electrical system’s ground plate and engine shafts?

So, during a lightning storm would it make sense to disconnect those two cables? But even if we do that, they’re inside our salon with no path to water. Then there’s nothing grounding the mast at all.

Hmmm, should we bolt a big ass cable to our mast and dangle it in the water?

[Bowdrie]

Originally Posted by fxykty

Hmmm, should we bolt a big ass cable to our mast and dangle it in the water?

Not surprisingly, a variation of that was common in the days of wooden masts.
The difference being that lengths of chain were attached to the chainplates to hang in the water and ground the standing rigging.
Aluminum masts should have an EASY AND SHORT path to water/ground, the straighter and shorter the better.
It usually doesn't stop all damage, but it can do much to minimize it.

[team karst]

Title of the thread should be: Lightning Transportation System.
ie: providing a low R path for the current to water.

[RaymondR]

Originally Posted by s/v Jedi

No, please. Right under the base of the mast, straight connection between mast and bonding plate.

Boats with holes blown through fiberglass do not have these bonding plates to deal with lightning strikes. They are 100% effective in preventing that kind of damage when installed correctly.

Possibly need a modification of nomenclature?

I think what you are saying is that a good conduction to earth (ie the sea) from the mast is required and separate from the bonding system which is present in a lot of boats and which keeps all the metal fittings exposed to the sea water at ground potential.

In effect, a very high current capacity flow path dedicated solely to grounding the mast without connection to the vessels other electrical, RF earthing or bonding systems.

[team karst]

Originally Posted by RaymondR

...

In effect, a very high current capacity flow path dedicated solely to grounding the mast without connection to the vessels other electrical, RF earthing or bonding systems.

Yes, that technique is quite difficult to implement. Isolation from the high current/high voltage is the intent. But the large magnetic field developed from a strike doesn't require direct/physical contact to cause high currents in circuits not designed for it.

I think of the problem statement in 4 parts:
1) protect the occupants on board;
2) protect the boat from sinking
3) protect the prime movers, and mains power circuits
4) protect the electronics.

One chronic issue most of us have, including myself, is installing the primary COMM antenna at, and even above the highest point of the mast. No surprise that the strike current will tend to run down the coax into the networked nav station area, now involving many pieces of electronics some distance away.

Its like designing a car for safety, but the driver is seated at the front bumper!

But, items 1, and 2 above are entirely doable, and 3 is possible. 4 will be a huge trick to pull off. We need to talk about battery operated, isolated devices, with wireless connectivity, and some other tricks.

[Frankly]

As in all things lightning, no guarantees.

I installed a two radio switch (VHF) that in the center off position connects the center coax conductor direct to the ships lightning ground system (got to remember to turn it on/off). In the radio positions (ICOM/ Std Horizon) there is a gas discharge tube shunting lesser discharges to ground.

Both my neighbor and my wife say my yacht took a direct hit last Summer (I was in another room). Only the wireless remote for the windlass bought the farm.

Frankly

[team karst]

Frankly; very nice. Is the switch at the base of the mast?

[Frankly]

Within a foot or so. The other aluminum box is a homemade surge protector for the mast lights. The hull mounted copper ground plate is sitting right below that location.

Some pictures in my associated albums for the details.

[Tetepare]

Some critical infrastructure industry applications (e.g., telecommunications towers) use Transtector lightning/EMP quick reaction MOV fuses which should work well on boats if properly grounded.