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Old 07-06-2023, 03:14   #1
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Lightning strike/damage avoidance question

I store my 39' sailboat every year from June to November in Georgia and am wondering whether she's more or less likely to be hit by lightning and/or damaged by a lightning strike if she's stored on the hard (vs stored in a marina)? I'm guessing that, because my insurance rates are the same regardless how my boat's stored, that the risk is equal, but figured I'd see if anyone is aware of any data on this subject (or has a good technical understanding of why lightning is more or less likely to strike a sailboat).
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Old 07-06-2023, 03:30   #2
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Re: Lightning strike/damage avoidance question

Simplified, use height of mast head as the risk factor. Lightning not always strikes the highest point but in general, the lower the safer.
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Old 07-06-2023, 04:39   #3
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Re: Lightning strike/damage avoidance question

Interesting question.

When on the hard, there are usually other buildings, towers, etc, in the vicinity, which would be taller than the mast on your sailboat, and more likely to get hit by lightning instead of your boat.

I've never seen lightning hit any boat at my marina, though I have been hit by lightning (once) while I was offshore.

Even on the hard, there are likely to be other boats as well around you, with taller masts.

I'd be more worried about potential hurricane winds than a lightning strike.
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Old 07-06-2023, 06:37   #4
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Re: Lightning strike/damage avoidance question

Supposedly Catamarans are the likeliest targets to be hit. Tie your boat up next to a cat and statistically, the cat will be hit, not your monohull
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Old 07-06-2023, 07:17   #5
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Re: Lightning strike/damage avoidance question

Can we assume you store with the mast down?

It makes a difference…..
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Old 07-06-2023, 07:48   #6
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Re: Lightning strike/damage avoidance question

The first rule about lightning is that anybody who claims to know what is going to happen is wrong. They might be get lucky right about the lightning, but the are for sure wrong about KNOWING.

I would GUESS that a boat on the hard is more likely to be hit, and it hit more likely to be mechanically damaged. Assuming of course that everything else is the same, which of course it NEVER is!
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Old 07-06-2023, 08:24   #7
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Re: Lightning strike/damage avoidance question

True, nobody can tell when, where or how a lightning strike will occur, this is a given.

But, starting with this, the odds are slim to be struck by lightning in the first place.

Having sailed thru' countless lightning storms over a period of 35 years afloat, I have been struck only once and considering I was the only thing out there with a tall metal stick pointing to the sky, I would say, pretty decent odds..

I don't see where a boat is any more liable or more safe than anything or anyplace else.

But..."generally speaking" if there are other more attractive or more conducive objects in the immediate area for a lightning strike, the " likelihood is vastly more improved" of the strike happening there rather than your mast.

My 2c off course...
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Old 07-06-2023, 08:44   #8
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Re: Lightning strike/damage avoidance question

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Originally Posted by SailingHarmonie View Post
The first rule about lightning is that anybody who claims to know what is going to happen is wrong. They might be get lucky right about the lightning, but the are for sure wrong about KNOWING.
Definitely agree with this.

Also, has anyone figured out why it is that multihulls are hit more often?

It’s a statistical fact from the insurance data.

But it could have any number of causes:

-Multis are used in the warmer areas (where there are daily thunderstorms) more than cooler climates
-Multis are more likely to have comprehensive insurance since they are usually newer and more expensive
-Multis often have taller masts per LOA

So many reasons other than hull arrangement come to mind
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Old 07-06-2023, 08:59   #9
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Re: Lightning strike/damage avoidance question

Actually multihulls have a wider footprint in the water and a longer waterline. I would guess that could be an important factor.

One thing I have been wondering if a very light tent, of metal strings with metal mylar bands attached raised to the top of the mast and hanging over the side all around would not be working as a kind of Faraday cage on a yacht at anchor.

Similar to a low windage camouflage net.

A bit like this:

https://www.alamy.com/stock-photo-re...102216909.html
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Old 07-06-2023, 09:01   #10
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Re: Lightning strike/damage avoidance question

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Definitely agree with this.

Also, has anyone figured out why it is that multihulls are hit more often?

Itís a statistical fact from the insurance data.
...
I wonder if the longer waterline length/area in multi hulls is a factor in the increased number lightning hits vs mono hulls.

The last two issues of Professional Boat Building has had articles on lightning strikes, different codes, how to minimize damage, protection systems, etc.

Later,
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Old 07-06-2023, 09:07   #11
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Re: Lightning strike/damage avoidance question

Right, but multihulls have less wetted surface area.

More wetted surface area should be what causes the initial static build up to allow those leaders and charges to build and promote full strikes
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Old 07-06-2023, 09:11   #12
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Re: Lightning strike/damage avoidance question

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has anyone figured out why it is that multihulls are hit more often?
This is probably way out in left field, but the "Double diamond" rigging on many multihulls looks surprisingly like a Rhombic antenna in the vertical position.
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Old 07-06-2023, 09:13   #13
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Re: Lightning strike/damage avoidance question

Multihulls typically have two engines, shafts, props, etc in the water, making for a better "ground" than a monohull with just a single engine, could be a reason ??
Catamarans also, typically have a big alum cross-bar and wire supports up on the bow, something else, mono's don't have....could also be a factor ??

At one time, one could purchase this bottle brush doodad, which was mounted on the top of one one's mast, ostensibly to minimize a lightning strike probabilities, but whether this worked or not, hard to say. I don't see those things anymore.

Growing up, in suburbia, there was a house down the street from us, that got hit repeatedly by lightning, usually always blowing the chimney right off. No explanation, but that house got hit a lot.
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Old 07-06-2023, 09:18   #14
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Re: Lightning strike/damage avoidance question

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Right, but multihulls have less wetted surface area. That should be what causes the initial static build up to allow those leaders to build and promote full strikes
I read something, somewhere, that a component of the strike could be, or is, because of the interface with the hull and water surface. If that is true, a multi hull has more length/area at play than a similar sized mono hull.

Later,
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Old 07-06-2023, 12:28   #15
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Re: Lightning strike/damage avoidance question

My understanding is that height only really comes into play when something gets to about 400 feet or so. Lower than that a tall object is the same as the ground next to it, as far as likelihood of a strike. There are plenty of photos of lightning hitting the ground next to a radio tower, or a tall building, next to trees, or even hitting a radio tower near the ground instead of the top.

I am lucky to have had 2 lightning strikes right next to my boat, close enough to give the helmsperson a significant jolt through the wheel. If there was any truth to the myth of tall objects, at least one of those would have hit me directly.

And yeah, multihulls statistically get hit more than monohulls. But AFAIK no research has looked into why. My guess leans towards the greater number of multihulls relative to monohulls in areas like Florida, and greater numbers of monohulls in areas like California.
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