Being Hit By Lightning - To Ground or Not - Page 4

txmatt · #31 (**permalink**) 01-23-2008

GBurton,
Grounding effectively is certainly possible, particularly in salt water. "Ground" is simply something big that will absorb the excess charge and potential.

An interesting article that I found when researching about this: http://www.thomson.ece.ufl.edu/lightning/IEEE.pdf

I was caught out in my first thunderstorm last weekend and have been thinking about this some as a result. I have a deck stepped mast and a full keel with internal ballast (i.e. all ballast is well encapsulated.) No compression post, either; the mast is over a bulkhead. I could run 4 gauge up the mast and then down through the deck and hull and to a copper plate, but I don't much care for that idea as it would be, in my view, inviting a strike and would require new holes in both the deck and hull, not to mention the wieght of the wire in the mast. I guess I could just bond some 4 gauge to the base of the mast instead of running it up to the top. Of course, the marginal effectiveness of the grounding plate in low conducting fresh water that I usually sail in doesn't help motivate me any.

I don't care much about electronics damage as I don't have much, certainly nothing expensive, but more concerned with hull, rigging and people damage.

I would be interested to hear any ideas to deal with this.

GBurton · #32 (**permalink**) 01-23-2008

The point that I was trying to make, is that the jumper cables provide a path to "ground" as well. You may have a well bonded system with an external plate etc. but this will not guarantee that you will not sustain damage from a hit. The energy transferred to the boat may be enough to overwhelm a "grounded" system and cause a lot of damage.

I suspect what a lot of people are talking about here is not a grounded system at all, it is just a bonded system.

Wrapping the anchor chain around the mast would not be a good thing to do imho

txmatt · #33 (**permalink**) 01-23-2008

Quote:

Originally Posted by GBurton

The point that I was trying to make, is that the jumper cables provide a path to "ground" as well. You may have a well bonded system with an external plate etc. but this will not guarantee that you will not sustain damage from a hit. The energy transferred to the boat may be enough to overwhelm a "grounded" system and cause a lot of damage.

I suspect what a lot of people are talking about here is not a grounded system at all, it is just a bonded system.

And the point that SD was making was that the method of attaching the cables (clipping them on) would not provide and adequate path the ground, which I think is probably true. The 2 ga. wire wouldn't do much good if the connection is poor (loose and small area), and the low conductivity of the stainless shrouds relative to the mast has already been disscussed, making this a less than ideal solution.

GBurton · #34 (**permalink**) 01-23-2008

If the hit was on the capshroud then it is being conducted right? And then you would want a way to take it to your "ground"

Wouldnt the shroud be a better conducter than the fiberglass deck? And nobody said it would be an ideal situation, it would be better than nothing.

txmatt · #35 (**permalink**) 01-23-2008

Quote:

Originally Posted by GBurton

If the hit was on the capshroud then it is being conducted right? And then you would want a way to take it to your "ground"

Wouldnt the shroud be a better conducter than the fiberglass deck?

You might want to check out that article I linked to. It explains the heat generated in a 8 ga. Cu wire and why such a wire is inadequate. The same would likely be true for the clips on the cables and the shrouds themselves, for that matter.

GBurton · #36 (**permalink**) 01-23-2008

What does #8 wire have to do with what we are discussing?

Stillraining · #37 (**permalink**) 01-23-2008

Advice by some people with a hole lot more experience them I.

I'm taking it all in !!

Now for my individual case please refer to post # 10 for pictures.

1) I have sofar gathered not to try and redirect the strike horizonally to my existing bonding plate. Ok I got that

2) My fuel tanks straddle the mast step ( Built in fiberglass at construction ) and my keel bolts are SS a very poor conductor Im finding out here.

3) There is no room for any new hull penitrations due to fuel tanks and keel. ( unless drilled all the way thru keel ..yikes!!

4) Lightning current will flow to the bottom of the mast possibally causing severe side flashes befor returnning up mast to posibally disipate thru another mast conected channel. ie..shroud or mast deck to water connection.

Im stuck on what to do on this one guys ?

killarney_sailor · #38 (**permalink**) 01-23-2008

We were hit by lightning a number of years ago on a passage between New York and Bermuda. The remarkable thing was not that we were hit, but how long it took before we were hit. Strikes were hitting the water near us every 30 seconds or so for 20 minutes plus before we were hit. At the beginning it was terrifying but after a few minutes just awe-inspiring.

The boat was a Nonsuch 30 which had a heavy battery cable from the mast base to the forward keel bolt that was perhaps 8 feet aft. The boat has external ballast. Damage was a burnt out voltage regulator on the engine, all the nav lights and a windex that was blown off the mast head and hit the water in a semi-molten state (you could see its shape bending as it fell). I happened to be looking at the mast head when we were hit and it was spectacular to see. There was probably an inch of rain in the cockpit from the intense rain but no one felt anything.

You can get hit, but it was my sense that it is pretty hard to get hit. We were the tallest thing for miles but it took a long time before we got nailed.

txmatt · #39 (**permalink**) 01-23-2008

Quote:

Originally Posted by Stillraining

Advice by some people with a hole lot more experience them I.

I'm taking it all in !!

Now for my individual case please refer to post # 10 for pictures.

1) I have sofar gathered not to try and redirect the strike horizonally to my existing bonding plate. Ok I got that

2) My fuel tanks straddle the mast step ( Built in fiberglass at construction ) and my keel bolts are SS a very poor conductor Im finding out here.

3) There is no room for any new hull penitrations due to fuel tanks and keel. ( unless drilled all the way thru keel ..yikes!!

4) Lightning current will flow to the bottom of the mast possibally causing severe side flashes befor returnning up mast to posibally disipate thru another mast conected channel. ie..shroud or mast deck to water connection.

Im stuck on what to do on this one guys ?

Maybe dill a hole at an angle through the keel and insert a copper rod connected to a dissapating plate on the outside of the keel? Maybe if you did it towards one side and at a 45degree angle or so it wouldn't be so long.

Your situation doesn't sound a lot more fun than mine.

soulesailor · #40 (**permalink**) 01-23-2008

Could you get a grounding plate installed forward of the mast step and fuel tanks? Your entire bilge area is flanked by gas tanks? No room anywhere? I don't think lightning will come down your mast and then go back up again looking for another route. It would probably come down the mast and keep going or take another route from the start. That is why I also have my shrouds, stantions, cleats, bow pulpit and push-pit also connected to my 6' long through bolted grounding plate, along with a bottle brush dissipator on the masthead. I would try hard to find a place to get a nice plate attached somehow, it's not something you want to learn the hard way.