Tuesday, July 14, 2009

The Fear of a Lightening Strike At Sea

How scared are you of lightening at sea?

On the Greek sail trip we had a spot of bother with a storm as we approached Orei. To the south west were dark clouds lit occaisionally by brief flashes of wriggling white lines.

It didn't go down well with some of the crew: "Let go of the bimini - its support has got metal in it!" I was told.

I've been unhappy at the sight of lightening mid channel, where it is clear that our mast is the only thing that is both a) metal and b) above sea level. But in the middle of the Greek isles there are loads of mountains and buildings, some with lightening conductors that must be really tempting for those electrons high in the clouds.

And then take as an example what happened to Liza Copeland and co on "Still Cruising" when they were struck by lightening off South Africa. No one suffered in the blast though ok almost everything electrical was fried.

So relax, it will be ok.....but... OMG!!! I had this terrible thought...

What about my iPhone??? It will become an expensive slice of toast!!

After a moment of worry it was suggested that the solution was a Faraday Cage, an enclosure made of conducting material which ensures that the electric field within it is constant - see the Wikipedia article here.

But how many yachts go to sea with a Faraday Cage? Ah-ha, another thought - what about the oven?

So it was that in the midst of the thunder storm my precious iPhone was stored for safety in the yacht's tiny oven.

In the end we didn't get struck by lightening, and to this day I have been wondering..... would it have worked?


O Docker said...

I believe the only proven lightning deterrent, JP, is a nice bottle of wine.

Your iPhone might have fried (baked?) in the oven, but you probably wouldn't have cared as much.

Has anyone actually captured a live Faraday in one of those cages?

Carol Anne said...

A thought arises ... if a lightning strike were to enter the boat in such a way as to get to the oven ...

Attached to the oven is presumably a hose that carries propane gas. Even if the gas is turned off at the tank when the oven is not in use, there will still be propane in the hose.

OTOH, there aren't any easy routes for electricity to get conducted to the oven, or much of anywhere else in the boat. When electronics get fried, it's usually through the boat's wiring system, via a radio antenna or the like.

BTW, I believe that even in Britain, "lightning" (the weather phenomenon) is spelled without an e. "Lightening" is the present participle of the verb "lighten", which means "to make or become lighter".

JP said...

Nooooo! My previous iPhone! No bottles of wine would have been enough.

I was worrying a bit about the spelling of lightening / lightning so don't be surprised if use one or other.

Lisa Copeland said that some of the electrics that were unplugged got zapped too, so that wouldn't help.

I could have been doubly safe and:
- put the iPhone in a plastic container
- wrapped the container in tin foil
- put the tin foil wrapped container in the oven

It would make a good episode of Top Yacht - zapping a yacht with lightening and seeing what happened and whether this would work (are you listening BBC?)

Carol Anne said...

If the electronics in question were unplugged but still close to materials through which hundreds of thousands of amps were coursing, the electric field would have been enough to fry the electronics. In that sort of situation, a Faraday cage would definitely have been protective. The oven, assuming its outer shell was reasonably solid and made out of conductive material such as steel, probably was a good way to protect the iPod.

Here in New Mexico, with the highest per-capita death rate from lightning of any state in the U.S. (Florida has a higher number, but a lower per-capita ratio), authorities are always advising us to stay away from water when thunderstorms are near. Being in a car, however, is generally a good way to stay safe; the steel shell of the car makes a great Faraday cage.

Now, however, Pat and I have a car whose body, like the hull of a boat, is made of fiberglass. We'll just have to make a point of driving something else when there are thunderstorms in the area.

JP said...

I'm not sure if you saw it but there was a classic episode of "Top Gear" where Hammond was in a car while it was struck by artificially generated lightening and was fine due to the Faraday cage effect.

That was a traditional steel frame car - not sure if modern carbon fibre would have been as good