Paint on Lightning Protector

[Sailor_Grant]

On my 1978 Cape Dory 27, there is a lightning ground metal plate built into the side of the full keel. This grounding plate is attached to the backing plates for the chainplates.

The grounding plate is currently painted over with antifouling paint. Is this okay?

This was a 1978 design, so a lot of new information on lightning has been found since then. Does this system even work?

[tkeithlu]

Makes no difference whatever. Lightning before it strikes is a static electric charge, concentrated at the highest sharpest point around, caring nothing about conduction, an once it hits, it "don't care about no stinking paint job."

[tkeithlu]

Sorry, that was flippant. Yeah, best you keep the plate clean, because you probably are using it as a ground for everything in your boat. Lightning is a phenomenon we can't really relate to - first because the charge is static, so shape concentrates, not conduction. Second, the voltage, current, and temperature are outside human experience. All it would take is a few bubbles of water in your fiberglass, ergo massive steam, ergo flying fiberglass just like flying tree bark. It will take the easiest path(s) to ground, with either all going through your grounding system, or part throught the VHF, the GPS, the AIS, the radar, the laptop with Open CPN, and you because you are holding the wheel when it hits. The sound starts in the middle of your head and goes outward.

[S/V Illusion]

To be precise, it’s not a “protector” but rather serves as a ground point intended to help dissipate a strike. Nothing protects a boat. It’s impossible to quantify what if any added value it may serve beyond the keel itself but it probably can’t hurt as long as it isn’t attached to the glass.

[RaymondR]

Lightning conductor or ground bleed for the bonding system it's best not to have it's conducting function impaired by covering it with an insulator.

[Sailor_Grant]

Also, this boat only has a DC electrical system, so there is no ground bleed. This is purely a lightning ground to my best knowledge.

[a64pilot]

Many, many Sportfishing boats used to have larger bronze plates on the bottom that they would connect the Tuna tower etc to, they are almost always made from aluminum tubing and are sort of like a radio mast.
I don’t think there was ever any evidence that the large ground plate connected to the tuna tower with heavy gauge wire actually protected or reduced the likelihood of a strike.
I know we all avoided the tubing during bad weather, was real sure not to touch it,
But many, many people paid large sums of money having them installed.

Now I feel fairly certain that there is no evidence that they don’t work or cause any kind of harm either.

[a64pilot]

Originally Posted by S/V Illusion

To be precise, it’s not a “protector” but rather serves as a ground point intended to help dissipate a strike. Nothing protects a boat. It’s impossible to quantify what if any added value it may serve beyond the keel itself but it probably can’t hurt as long as it isn’t attached to the glass.

I’m certain it’s attached to the glass and not just hangin over the side.

We always heard rumors etc that lightning would blow that plate off and a large hole in the boat, bit never, ever saw any real evidence

[Thumbs Up]

The best lightning protection is to dock near boats with taller masts.

[robert sailor]

Originally Posted by Thumbs Up

The best lightning protection is to dock near boats with taller masts.

You can get pretty good lightning protection docking next to a shorter mast....as long as it's on a Catamaran.

[Thumbs Up]

Make sure that it's a fiberglass catamaran. Mine's never been hit. Knock on wood.

[Jim Cate]

Originally Posted by Thumbs Up

The best lightning protection is to dock near boats with taller masts.

Sounds logical, but a few years back we were in the MBTBC marina in Manly Qld during a thunderstorm. A friend and fellow ham radio guy had a Spray replica, steel hull and a short ketch rig. He was situated between two modern sloops with much taller masts in adjacent berths. A lightning strike somehow found its way between the sloops, scoring a direct hit on his main mast, doing over thirty thousand dollars of structural and electrical damage. I dunno why this happened, but happen it did and I place little value in having taller rigs nearby!

Jim

PS Lots of boats rely upon their keels for lightning grounds, and those keels are always covered with antifouling, often many layers thick. Doesn't seem to detract from the grounding function.

[Frankly]

I used to design and specify lightning protection systems for buildings. In evaluating a building for needing a lightning protection system, the number 1 factor was location/ lightning activity. The number 2 factor was relative altitude (relative to surrounding structures).

Lightning protection systems are to protect the underlying structure, they have no effect on probability of getting hit. The idea is to conduct the current to ground not involving the protected building ect. Unlike gravity, there are no absolutes when it comes to lightning.

On my yacht I have a copper plate 1/2 " X 6" X 24" right below my keel stepped mast connected with parallel # 1/0 cables connecting to 4 ea 1/2 " silicone bronze bolts soldered to the copper plate (that was fun). When I get around to replacing my chain plates, they will also get connected to the ground plate.

To keep the fouling at bay, I paint my copper ground plate, but scrape the edges before launch.

Also have 6 or 8 (lost count) homemade surge protectors and common mode chokes scattered around the electrical system.

I live in Florida, operate uninsured, so tend to be a little anal about such things.


Frankly

[Rucksta]

Originally Posted by robert sailor

You can get pretty good lightning protection docking next to a shorter mast....as long as it's on a Catamaran.

I've never heard this said out loud before.
I'm parked between two cats.
Great neighbours.

[RaymondR]

Originally Posted by a64pilot

Many, many Sportfishing boats used to have larger bronze plates on the bottom that they would connect the Tuna tower etc to, they are almost always made from aluminum tubing and are sort of like a radio mast.
I don’t think there was ever any evidence that the large ground plate connected to the tuna tower with heavy gauge wire actually protected or reduced the likelihood of a strike.
I know we all avoided the tubing during bad weather, was real sure not to touch it,
But many, many people paid large sums of money having them installed.

Now I feel fairly certain that there is no evidence that they don’t work or cause any kind of harm either.

Might come down to preferred path to ground.

Decades ago they were doing research on lightning strikes and they induced them to where they wanted by shooting a rocket up into the thunder storm. Although the wire was extremely fine it would initiate the strike down to their instruments on the ground. The tiny wire would vaporize immediately but the current would flow down the plasma conductor thereby formed.

Inducing the current path to ground through a connector to a hull plate might prove less damaging than letting. it find it's way through a big osmosis blister and thereby blowing a large hole in the hull.