Grounding the mast for Lightning Protection

[MArk]

You would think a metal airplane wouldn't be affected by lightning, but the aluminum skin is so thin that lightning current flow can generate enough heat during a strike to burn holes right through. The same thing can happen in a fiberglass boat.See story about Jeb Bush's plane on related link.Happy sails *_/),MArk

[John]

I'd like some input on how to ground the mast to achieve protection from lightning strikes. This is a real concern living in Florida as the rainy season ( with almost daily thunderstorms )is only months away.On most boats, the manufacturer goes to great lengths to run a big ground cable from the mast to the keel or a grounding plate and ties the battery ground, the engine and almost anything else that's metal to this ground. This forms what is referred to as "the cone of protection".I just acquired my Mac 26S and found that the mast isn't grounded. - Has anyone else made mods to get their boat grounded for lightning protection ?- If so, how did you do it ? Thanks, John

[Paul M]

try looking through the archives in the forum section, I found alot of information there, along with some good links.

[John]

Thanks Paul, You are right. There are a lot of posts about lightning protection & boats that have been hit, etc in the archives. There are many votes for doing nothing & taking your chances as well as many who profess to using diffusers, grounding plates, heavy wire, chains, jumper cables, etc I was hoping someone had come up with a way to quick connect/disconnect a 26S mast to some novel grounding system. I guess the closest approach I saw to achieving this is clipping a battery jumper cable (with a copper buss bar attached) to the shrouds and towing it in the water when thunderstorms threaten.It's not very pretty, but I guess it might afford some protection by providing a path for lightning to travel if the mast does get hit. John

[MArk]

Hi John,Here's one of my favorite lightning information sites:http://www.marinelightning.com/science.htmThe other is on the related link.The concensus seems to be, if you're on fresh water, you need to find shelter on land. No amount of grounding in fresh water will prevent dangerous side flashes. In salt water, the mast, which is the best conductor on the boat, must be grounded to a 1 square foot or better grounding plate following recommended practices. All metal objects and electronics must also be grounded to the grounding plate.The reason everything needs grounding is that a lightning strike (even if not a direct hit) causes an electromagnetic pulse that induces high voltage spikes in nearby metal objects and electronics. If this elevated voltage is not drained off, electronics will be fried and crew will be injured or worse./_/), Happy sails,MArk

[Timm Miller]

during a storm......put some chains on you chain plates and let them dangle in the water. You can rig some jumper cables to the the same... make sure one end is in the water. This is not as good as a grounding system, but works when you get caught unexpected.

[John Dawson]

While I haven't followed the discussions on grounds for boats assiduously, I expected to see some advice that agreed with my best friend, a seascout-electricalengineer-exnavysub-nowNRCinspector who said (in my own paraphrasing) no little wire is going to channel a major hit. One of the primary reasons for trailing a wire of any dimensions is to prevent a difference in charge or potential between the masthead and surrounding area so it doesn't constitute a focal point. Conducting stray electricity is what most comments seem to address here. Is this how you understand it?

[Timm Miller]

It just lessons your chances........a direct hit, nothing can stop that. Now I heard while playing golf you can hold up a one iron because not even god can hit a one iron.......just something I heard.

[John]

So, the consensus says that grounding the mast just lessens your chances. Even so, that seems like a step in the right direction. Getting down to the practical side of doing this - Is anybody using a method more elegant than towing chains and jumper cables ? I'm thinking of something like a single conductor plug connected to a grounding bolt on the mast, plugged into it's mating socket next to the mast on the cabin top. Then a hidden large wire conductor that runs from the socket down to a through hull connection to a grounding plate (dyna-plate ?) that is attached to the hull somewhere away from the water ballast tank. The only concern doing it this way, is the corrosion that would build up on the ground plug and socket. Over time, this would make the ground less than perfect. Any other ideas or experience on how to do it short of using chains or a jumper cable ? John

[73mensailed]

I've read quite a few good articles with good links in the archives at sailnet.com. Just more ideas for you all.

[Jim Humphrey]

Check out the attached link. Some pretty deep stuff on lightning and boats.

[MArk]

Hey Jim,Did you mean this site?/_/),MArk

[Jim]

Yes Mark, some had sent me that link last year when this topic was being discussed on the other Mac site.