Lightning -- to ground or not to ground, that is the qn

[GordMay]

Originally Posted by Pelagic

All very interesting but back to basics for a simple sailor:
All Steel Boat-Wooden Masts with heavy Stainless Mast Top Caps and stainless rigging to hull.
What is my weak point in Lightning strikes?

Wooden masts are the weak point.
Install an air terminal [or not], and a #4AWG Cu. [or larger] down-conductor, from mast top, directly down to a grounding point, on the hull.
With multiple masts, it couldn't hurt to interconnect the top of the masts [triatic stay?, in blue, below.
PS: NOT a radio antennae.

.

[s/v Jedi]

Originally Posted by GordMay

Wooden masts are the weak point.
Install an air terminal [or not], and a #4AWG Cu. [or larger] down-conductor, from mast top, directly down to a grounding point, on the hull.
With multiple masts, it couldn't hurt to interconnect the top of the masts [triatic stay?, in blue, below.
.

Exactly. The document I linked up thread describes details perfectly

[absoffthewake]

I've been researching lightning protection systems for a while now. The amount of conflicting information out there is simply mind-boggling. I've dedicated a significant amount of time to this because I want to get it right. Below is my current opinion on the subject. Below that, are a few example videos that helped form my opinion.

Lightning Rods (of any type) both prevent and attract lightning. They prevent lightning by absorbing negative ions from nearby clouds. However, when the negative ions being generated in the surrounding area exceed the amount the rod is able to absorb, a strike occurs and the lightning rod can become the most likely area to be hit because it is the tallest thing in the area with the least amount of resistance to ground.

If you research modern lightning protection systems in skyscrapers, more advanced systems push more positive ions in the air when they detect an influx of negative ions overwhelming the area. Although they are able to prevent a significant amount of strikes, sometimes even those systems are overwhelmed and a strike occurs anyway. That is where lightning mitigation comes in. When that strike occurs, you need to direct the strike (or at least attempt) directly to the ground to minimize the damage to nearby equipment (and people). A big thick copper rod (or cable) can and does effectively direct strikes so long as it is thick enough AND the rod/wire is properly grounded to the earth. In order words, big = better. If you think this is impossible, then please explain why tenants of skyscrapers do not constantly replace all their technical equipment every time a strike occurs.

I have no doubt that a system like this can prevent many strikes and even dissipate a significant amount of energy when a strike occurs. But I doubt the small seidarc electrodes provide sufficient grounding to water (on their own) when a large strike occurs because:
1: the small surface area touching water.
2: lightning wants to travel straight down. Any turns in the wiring significantly increase the chance of charge jumping off the wire (and yes burning thru the insulation) onto nearby conductors.

I read a post by someone claiming to use that system saying they received a shock while lying down in bed when they got struck, but the damage to the boat was minimal. I believe the shock came from the fact that the boat effectively distributed the bolt throughout the boat before the bolt made its way out rather than strait down to ground/water.

I would improve the system by ensuring there is a solid connection from the shrouds and the mast strait down to a traditional ground plate that is directly underneath them. In addition to that, I would use the sidearc electrodes to dissipate any remaining charge that is unable to exit via the plates or is collected by side flashes that are closer to them in other parts of the boat. Instead of a traditional lightning rod, I would replace that with a CMCE device as they have provided laboratory evidence that they are more effective in absorbing charges, which can delay/prevent the formation of a streamer, preventing a strike. It also appears to be designed well enough to take a strike and direct it to wiring that is thick enough to have a shot. A properly installed fuzzy static dissipator is able to accomplish the same, but I believe it issignificantly less effective at it. In addition, it is very unlikely that it would survive a direct strike. Certainly not multiple.

To help protect your electronic devices, I would install a surge suppression device like this as close to each device as possible AND on your buss bars to cut off the path and allow the charge to exit via the ground plates/sidearcs. Although some of these devices are sacrificial, after the event you can disconnect/replace them rather than having to replace all your expensive/hard to get equipment.

In order for any of these dissipation/mitigation devices to work right, they must be connected as strait to the ground as possible AND they must be the highest thing on your boat, with any other metal objects insulated (or underneath them) to decrease the chance of the strike missing the device and hitting other objects, which can change the path of the strike. One thing you can do right now is attach a 4AWG copper wire to the bottom of your mast, connect to the other end to a copper lightning rod, then place dunk the rod underwater well below the lowest point of your hull. Easy if you have a catamaran with a mast near the trampoline. Not so much when your mast is directly above the saloon.

Hopefully this helps.

Lightning protector CMCE versus Franklin rod

https://www.youtube.com/watch?v=wbDiJ2Crpis

Lightning Rods Part 1 -

https://www.youtube.com/watch?v=zhu5pIrPw7U

Lightning Rods Part 2

https://www.youtube.com/watch?v=G1_XFbtWoFg

Empire State Building: Lightning Strikes Thrice!

https://www.youtube.com/watch?v=XKMdYbOfFzI

[Kettlewell]

I am somewhat skeptical any lightning ground system that could be installed aboard will work to prevent a lot of damage in the case of a direct strike based on some personal observations. I spent a few summers down in Panama and Central America where the bolts coming down sometimes looked more like columns than the usual spidery stuff we see in the USA. These columns would come straight down into the water which was obviously being vaporized in a huge cloud of steam. Though the strikes could be some miles away they sometimes triggered strange behavior on our boat, like turning on electronics that were turned off. I tried to disconnect everything important during these storms, and I always have a handheld GPS onboard that gets stored someplace safe. In Panama it seemed like 50% of the people we met had a lightning strike story, whether grounded or not. The other incident was when lightning struck the steel building my office was in and destroyed all sorts of electronics in the building. Nobody was hurt that I know of, but this was a building that couldn't have been more grounded: steel roof and walls, steel beam construction, plus the usual lightning grounds on the utilities, etc. The strike even fried various large surge protectors, etc. But, not everything was fried--there is a ton of luck involved in any lightning strike. For what it is worth, I have talked to numerous people with metal boats and it always seems they have a lightning strike story to tell.

[absoffthewake]

I agree that there is no way to completely eliminate the risk of lightning damage. A megaflash is going to remind you that you are a small and seemingly insignificant human, and your efforts are laughable. But throwing in the towel and saying que sera sera will absolutely result in preventable damage as it will increase your susceptibility to damage for even the smallest trickle of lightning and electrical field disturbances.

Before I properly grounded and surge suppressed my gate box, it got fried at least twice a year. It never got a direct hit. Now that it is properly protected, its been running trouble free for 3 years. I think metal buildings increase the risk of damage because it distributes the surge throughout the building, increasing the risk of arc jumping to other wiring rather than directing it strait to ground outside the building. A faraday cage isn't a bulletproof faraday cage if there are large openings. But to your point, it seems likely that a large metal object in the water could certainly attract more lighting attention. This stuff makes my head hurt...

[Kettlewell]

But throwing in the towel and saying que sera sera will absolutely result in preventable damage as it will increase your susceptibility to damage for even the smallest trickle of lightning and electrical field disturbances.

But do we know that? If having all the grounding done just right actually increases your chance of getting a direct hit maybe having none is worth it, even if you have to occasionally deal with "the smallest trickle of lightning and electrical field disturbances." Those can be dealt with by disconnecting electronics during storms, having backups, and possibly storing some handhelds in the oven. Personally I want to avoid the big direct strike that is so destructive. My main point is that in the case of a direct hit the grounding on a boat seems to not prevent damage, so what's the point?

[s/v Jedi]

Originally Posted by Kettlewell

But do we know that? If having all the grounding done just right actually increases your chance of getting a direct hit maybe having none is worth it, even if you have to occasionally deal with "the smallest trickle of lightning and electrical field disturbances." Those can be dealt with by disconnecting electronics during storms, having backups, and possibly storing some handhelds in the oven. Personally I want to avoid the big direct strike that is so destructive. My main point is that in the case of a direct hit the grounding on a boat seems to not prevent damage, so what's the point?

A proper bonding system designed to handle lightning strikes will 100% prevent sinking due to hull / thru-hull damage. I know because we spent 10 years in Panama and unfortunately experienced more than one direct strike.

If you are talking about damage to electrical wiring then I estimate that 99% can be prevented by using surge suppression, isolation transformers or unplugging shore power.

If you’re talking about damage to electronics then you got the most vulnerable items and the protection goes down significantly but I still estimate 70% of all damage due to lightning can be prevented by multi-level surge suppression.

About preventing/attracting strikes. You can’t prevent strikes. There are two things you can do to influence where the strike hits: camouflage and attract. The camouflage part are the bottle brush devices if installed correctly and success will depend on surroundings. Attract is the lightning rod, the conductors over the ridges of roofs etc. This is done to prevent the strike to hit the parts you want to protect, like what is underneath. This is the cage/cone of protection.

That effect of attracting lightning doesn’t mean you attract strikes that would otherwise not hit you. The area of protection is very limited, you don’t attract it away from a neighbor. For that only the camouflage can work.

The thing is that prior to the strike leaders form. The tip of a leaf of a nearby tree may offer a much better path than the top of your mast even if it is higher. Or maybe both win and the strike forks.

[absoffthewake]

Having a 70' mast increases your chances of a direct hit not being grounded. That is a myth propagated by a lack of understanding of what is actually happening. Refer to the videos in my first post for a more detailed explanation but simply put:

The coronal discharge effect of a grounding/lightning rod system absolutely decreases the likelihood of a direct impact and also has the benefit of significantly reducing the strength of the bolt when it does occur.

If you get stuck with a grounding system, you were going to get struck regardless because a 70 mast will always be the path of least resistance, grounded or not.

In the Lightning Rods Part 1 video minute 5:40, observe the striking as the wand is moved about the globe. The strike occurs wherever the resistance to ground is least, which is usually straight down in a perfect environment. As the wand is moved closer to the pin, the coronal discharge stops the striking from occurring. So one could interpret from that observation that a lightning rod eliminates lightning, but that is not true because it is possible for the absorption of negative ions to be overcome by a faster charge buildup. So in order to resume striking, he would have to turn up the speed of the Van de Graaff generator or in nature, have a bigger storm cloud. Once striking is resumed the bolt will be smaller than the bolt in other parts of the globe because most of the energy is being absorbed by the coronal discharge.

I am of the informed opinion that a grounded boat with a 70" mast and lightning rod has less risk of being directly struck than the same boat not grounded. It also comes with the added benefit of having less of a risk of having a hole burned through your hull if you get struck. That coupled with surge protection could give you a better chance as is disconnecting things but if you are not onboard to disconnect things (or can't because they are hardwired) it does you no good.

As for whether a metal sailboat has less risk than fiberglass boat... that's an entirely different argument. I think it would be fair to say that the high concentration of highly conductive material could provide a pathway of less resistance for side flashes from surrounding boats that are struck. That could introduce risk that may not be offset by the benefit of greater coronal discharges but I haven't researched that enough to form an opinion there.

[absoffthewake]

Here is another great video about what happens when you have a lightning rod that is grounded. This is from an open house at Jeffferson Lab, a dept of energy facility. I think the whole video is interesting but the key point is at 7:48.

https://youtu.be/ubZuSZYVBng?si=F75I1yHE0mf80gSh&t=468