Visit our Popular Forums

hellosailor · 26-11-2014, 15:00

St. Pauls' might as well be a unicorn in a cattle ranch. It certainly is not contemporary 20th century skyscraper construction, with heavy steel frames and masonry only serving as the cladding.

DumnMad · 26-11-2014, 17:00

Seawater is a much better conductor than fresh or groundwater so I think practice on land might be irrelevant.
Its probably the groundwater that causes lightning to strike the house in the gully rather than the ones on higher and dryer ground.

With a storm coming your way you could hang some copper wire from shrouds to water but you would want to be quick!!!
I still can't see whether grounding will save you from a strike or attract more to you.

Meanwhile I shall do nothing except hide in the saloon away from the masts.

GILow · 26-11-2014, 18:09

It must be a Swanson thing... Our boat got hit and the VHF antenna ended up in the dinghy too. The owner had chains trailing in the water from the shrouds at the time, as was his standard practice in stormy weather. No damage to the hull has been found after 20 years. Might have been good luck or might have been thanks to the chains. Fried a few electronic devices at the time.

Glad Sweetchariot is still around to share the experience.

Matt

Sent from my iPhone using Cruisers Sailing Forum

maxingout · 26-11-2014, 18:30

I recently had a patient who was struck by lightning, and the only damage that happened to his body was that he developed cataracts in both eyes. Eyes don't like large electric currents.

colemj · 27-11-2014, 05:07

Quote:

Originally Posted by DumnMad

I still can't see whether grounding will save you from a strike or attract more to you.

Neither. Grounding has not been shown in any studies or actuarial analyses to increase or decrease the chances of being struck.

The purpose of grounding is to increase the probability that the strike will safely find its way to ground through the grounding system rather than randomly through the boat (punching holes in the hull, blowing out thruhulls, etc).

Mark

model 10 · 27-11-2014, 08:47

Quote:

Originally Posted by colemj

The purpose of grounding is to increase the probability that the strike will safely find its way to ground through the grounding system rather than randomly through the boat (punching holes in the hull, blowing out thruhulls, etc).

Mark

There are other opinions on that. One is; first the lightning is checking for grounds or a potential and sends out small preliminary bolts before the big one goes off. By grounding your boat, it blends in with the surroundings better.

colemj · 27-11-2014, 09:26

I think you are confusing how stepped leaders and streamers occur. This isn't lightning sending out small reconnoitering bolts to determine where to strike. That just plain does not happen. They are random, and not really checking for grounds.

If you can point me toward a studied opinion on grounding, and not just uninformed people writing about how they think it works, I would be appreciative. I am very interested in this topic and have not found studies or hypotheses supporting that grounding either increases or decreases the chances of getting hit. There are some that suggest it may slightly decrease the chances, but that is a small decrease indeed.

I don't know of anyone who thinks differently than what I wrote, and you quoted. The purpose of grounding is to attempt to guide the energy more safely through the boat. While one could argue whether grounding really does any good, the purpose of grounding seems kind of incontrovertible to me.

Mark

Cadence · 27-11-2014, 09:57

Quote:

Originally Posted by Cheechako

If you are a lightning worrier, yes,

chainplates all the way to the waterline!

I'm not a worrier. I've had grounded and ungrounded masts. If it's going to get you it will. I have mixed emotions as to whether grounding attracts it or protects you? On one hand stick a grounded rod near a HV field and guess what attracts the voltage. On the other hand your mast gets it and being grounded the shouds act as a Faraday cage protecting those within and it might not blow a hole in your hull. I guess the latter is the conventional thinking.

Cheechako · 27-11-2014, 10:33

Quote:

Originally Posted by Cadence

I'm not a worrier. I've had grounded and ungrounded masts. If it's going to get you it will. I have mixed emotions as to whether grounding attracts it or protects you? On one hand stick a grounded rod near a HV field and guess what attracts the voltage. On the other hand your mast gets it and being grounded the shouds act as a Faraday cage protecting those within and it might not blow a hole in your hull. I guess the latter is the conventional thinking.

Sorry, didn't mean to imply you were... It was just coincidental that my post was right after yours!

colemj · 27-11-2014, 10:39

Quote:

Originally Posted by Cadence

I have mixed emotions as to whether grounding attracts it or protects you?

While grounding can, in a catastrophic sense, "protect" you and the boat (see previous discussion), it neither attracts lightning nor decreases your chances of getting struck.

A lightning bolt has already travelled 5,000' or more at 220,000 miles/hr by the time it gets near the ground - it isn't picky about the last 50' during those 200 milliseconds of its entire life.

Mark

Cadence · 27-11-2014, 10:52

Quote:

Originally Posted by Cheechako

Sorry, didn't mean to imply you were... It was just coincidental that my post was right after yours!

I didn't really take that you did.

Even if you did, I might have caused it? Life's to short to worry about the little things.

Cheechako · 27-11-2014, 11:27

Quote:

Originally Posted by colemj

While grounding can, in a catastrophic sense, "protect" you and the boat (see previous discussion), it neither attracts lightning nor decreases your chances of getting struck.

A lightning bolt has already travelled 5,000' or more at 220,000 miles/hr by the time it gets near the ground - it isn't picky about the last 50' during those 200 milliseconds of its entire life.

Mark

That's kind of been my feeling, but... why are there so many pics of lightning striking the ground rod on a skyscraper.. why not the corner of the building? etc etc Is it possible the bolt is influenced much further up than the last 50 ft?

westwinds · 27-11-2014, 12:50

Lightning can make holes in fiberglass. I think what happens is fiberglass can have ten percent water in it, which with minerals from its manufacture, make it a conductor for the voltages lightening contains. So, the water in the fiberglass turns into steam and makes a hole. The thing to do is give the lightening a path to the sea water.