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Catalina 25 Specific Forum

Hit by lightening - physical impact

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Mike Rauh
Deckhand

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11 Posts

Initially Posted - 07/27/2008 : 13:36:36

My boat was hit by lightening, I was not aboard. All my electronics are kaput; see previous topic on lightening and electronics for additional details and discussion. I've opened this topic to get some information about dealing with the physical impact of lightening to a boat.

At the top of the mast my antenna and windex vane are gone. I'll take the mast down to examine what physical damage was done. Beyond the obvious physical evidence, does anyone know if a lightening hit weakens the aluminum? Are there any types of tests that should be conducted to determine if the spars and shrouds are OK?

Someone told me that lightening must exit the boat somewhere. They suggested I have the boat hauled (it's a fixed-keel 1980 C-25). I was advised to examine the entire bottom especially around the keel to see if there are any cracks (exit wounds).

Do any of you have any comments or recommendations about other steps I should take to determine the physical health of my boat?

Thanks for any help you can provide.

1980 C-25 TR/FK
Capt. Mike
City Island, NY

Edited by - on

Ed Cassidy
Captain

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USA
365 Posts

Response Posted - 07/27/2008 : 13:52:45

I have seen the results of a boat hit by lightning, it sank in it's slip. The electricity had to exit the boat and when it did it created thousands of pin holes, right at the waterline. It was a powerboat but the hull was fiberglass. Look it over carefully.
Ed

Edited by - on

Breezy Cat
1st Mate

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38 Posts

Response Posted - 07/27/2008 : 14:24:13

I have heard and seen boats sink due to blowouts below the water line.
The fact that you found your boat afloat and didn't notice damage till inspecting the electrical is a good sign but...
Check all the through holes including the transducer and speedo.
Referring to your other post, call the insurance company and have them pay for a thorough inspection of the entire boat.
Most likely all the electrics/electronics and wiring need replacing, it sounds like the motor can be replaced as well as all the running lights.
This was one of the first questions I asked my insurer because it can and does happen.
BTW - There are severe thunderstorms in our area as I type this.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/27/2008 : 15:13:56

Terrible luck! Perhaps the melted bilge pump was the last step in a path to the keel bolts and into that big hunk of essentially exposed (except for paint) cast iron. BoatUS should cover your losses--they did for friends of mine whose electronics were fried by a nearby strike that didn't hit their boat--apparently they were done in by the magnetic impulse. You should have the boat hauled--if you see a lot of paint is missing from the keel, that and a lack of water in the bilge will be a good sign (all things being relative). You might need to put some paint on...

I won't speculate on the condition of the mast, but aluminum is a much better conductor than stainless, so your standing rigging is likely fine--although I'd have a rigger inspect it while the boat is out. See what BoatUS recommends (and will pay for). They seem to be pretty good about those things.

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skrenz
Captain

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USA
351 Posts

Response Posted - 07/27/2008 : 19:03:15

Lightening can follow any path. There is no way of knowing if it actually traveled down the total length of the mast or jumped down one or all of the standing rigging or both. Right now you do know that there isn't a hole in the bottom of the boat.
You say that it was moored at the time. It is very possible that the strike exited through the mooring line. There may be some indication of this.
Sorry about your electronics. No, a fuse somewhere won't help at all, the lightening not only flows through the wire but also around the outside of it. Since your motor starts and runs, its probably the starter/generator that's fried.
The only rather old suggestion made on this topic for prevention is to attach a length of chain from a shroud to hang in the water. This gives a least resistance path without going through the hull. This however won't necessarily save your electronics.

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DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 07/28/2008 : 07:58:10

skrenz said;

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> The only rather old suggestion made on this topic for prevention is to attach a length of chain from a shroud to hang in the water. This gives a least resistance path without going through the hull. <hr height="1" noshade id="quote"></blockquote id="quote">

Let me ask you a question regarding this tactic. If you have 2 metal posts, one grounded and the other not and you put an electrically charged wire equal distance from both posts but close enough to jump to one or the other, which one will attract the electrical charge?
I'm betting the grounded post will 10 out of 10 times. So I am concerned that grounding will attract the lightning to my boat and have chosen not to

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/28/2008 : 08:51:58

This debate is older than any of us, and has been rehashed here many times. I won't get started... except to suggest that if you want to dangle something in the water from a shroud, especially in a marina, be sure you put a sacrificial zinc annode on the end. Otherwise, you're exposing your entire rig to electrolytic corrosion from stray current leaking from other boats, dock wiring, etc. Similarly, if you connect your mast to the keel, be sure the keel has a big zinc on it.

I'll also state (OK, you got me started) that I don't like the "dangle from the shroud" approach--it is possible that a grounded shroud would be just conductive enough to create the "leader" that's the first step in a strike, but not enough to be the preferred route for the strike going to the water. I don't know that--I'm just suspicious. Stainless is not a very good conductor--aluminum is an excellent one. There's no absolute protection--only relative... and I'm always a little suspicious of "old wives" solutions that seem too simple.

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stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 07/28/2008 : 13:35:57

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Stainless is not a very good conductor--aluminum is an excellent one.<hr height="1" noshade id="quote"></blockquote id="quote">

Aluminum is an even better conductor than Copper. Isn't it a fun fact that our masts are made of a better conductor than the stuff that is used in electrical wires!!!

(about the only metals that are better conductors are silver and gold)

So, I guess if you wanted to make your boat a less likely target, and given that you may need a new mast - perhaps you could consider a wooden mast.

Sorry, I know this isn't much help...because as Doctor Bristle notes, this is a debate that goes back...
Ohh, and another thing - as I alluded to in your other post, lightening is moving with great force, and once it hits on something, the laws of electricty as we 'generally' know them, are no longer valid. The force, or Amperage, is so great that the charge will keep moving regardless of conductivity of connective material ie:wood, fiberglass.

Edited by - stampeder on 07/28/2008 13:40:29

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 07/28/2008 : 14:12:56

I've related this story before but, since you asked............

I was struck at my mooring several years ago. Same result. No windex, electronics shot, radio fried, electrical panel fried, one battery shot.Mast and rigging remained sound.

I had two exit holes in the boot strip, one about the size of a quarter, the other right next to it about the size of a dime. These were about two feet from the bow, which means the lightning traveled from the top of the mast, down the rigging, through the chain plates and forward to the bow. The holes were actually pulverized, burned fiberglass. I also had about 25 pin-sized holes in the bottom which I didn't find until I hauled out that fall.

I was lucky. A fellow club member's Santa Cruz 26 was struck several years earlier and sank. He said he had hundreds of pin-sized holes in his bottom. These were the only holes that allowed water to enter the boat.

So, check your boot strip carefully and have the boat hauled. Look for pinhead-size dots (holes) with spider cracks eminating from them.

I made my own repairs since there wasn't any real structural damage. I bored out the holes with a dremel tool and filled them with thickened epoxy. I had the bottom and boot stripe professionally painted.

Edited by - on

skrenz
Captain

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USA
351 Posts

Response Posted - 07/28/2008 : 17:28:50

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by DaveR
 skrenz said;

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> The only rather old suggestion made on this topic for prevention is to attach a length of chain from a shroud to hang in the water. This gives a least resistance path without going through the hull. <hr height="1" noshade id="quote"></blockquote id="quote">

So I am concerned that grounding will attract the lightning to my boat and have chosen not to
<hr height="1" noshade id="quote"></blockquote id="quote">

I guess that's why the negative wire going from electric pole to electric pole is grounded to the earth at each and every pole. They perhaps want their poles hit.

I'm going to offer this even though I know I'm going to get blasted in the next 100 responses.

Years ago I was a builder in Santa Fe. We get a lot of lightning storms around here so the question of lightning rods was always a subject for discussion. We had so much destruction going on that there was an electrical contracting company that specialized in nothing but lightning rod installations.

So we were talking one day. The general consensus on how lightning rods worked was that they "channeled" the strike down through the wire connecting the rod, on the top of the house, to the ground. I was corrected. "No not at all" he said. "Lightning has so much power that there isn't a wire in the world that could pass that much power. Rather, the point is to keep the lightning from hitting the rod and its 'cone of protection' from getting hit in the first place."

It seems that lightning rods work on the principle of bleeding off positive electrons into the atmosphere. This works because the rod is connected to the ground, the source of the electrons, and a pointed tip at the end of the rod. (some physics principal I don't know cause the electrons to bleed off). This causes an ionized area around the rod which actually repels the leader strike from starting. The "cone of protection" (no not the ones you made out of tin foil as a kid) extends from the tip of the rod out at a 60% angle to the ground. Anything under that cone is protected. This is why in the plains you would always see several rods along the long axis of a barn so that the whole structure would be covered.
When you search the web you will find ample documentation supporting opposing views of the subject. I'll offer this link supporting mine:
http://www.lightningrod.com/manual5_how.html

Edited by - on

Mike Rauh
Deckhand

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11 Posts

Response Posted - 07/28/2008 : 19:46:01

I appreciate your comments and I'm always impressed at the collective wealth of experience I read on this association forum.

I've called Boat US insurance and opened a claim. They've been supportive and authorized an immediate haul of my boat. Tomorrow it will be hauled out, and the bottom will be washed. A thorough inspection will be preformed - looking for both large and tiny holes as well as blistering.

I have my fingers crossed and will open a topic on my insurance claim experience as I gather information.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 07/28/2008 : 22:33:59

Electrons are negative - always. Aluminum ranks below silver and copper in electrical conductivity.

Lightning rods provide an easier path to ground. The negative charge of the leader moves electrons to ground resulting in a residual positive charge at the end of the rod. Lightning that could otherwise strike within the protected cone is hopefully diverted by following the leader to the positive charge. That sounds good, but much is still not known about lightening. Two things are clear from statistics: lightning rods provide some degree of protection within the cone and lightning rods increase the likelihood of of being struck. Is the degree of protection greater than the risk of an increased likelihood of being hit? That is still up in the air. I take my chances now, but I will eventually go with an air-gap to ground system.

Edited by - Dave5041 on 07/28/2008 22:35:13

Voyager
Master Marine Consultant

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USA
5430 Posts

Response Posted - 07/28/2008 : 23:09:48

I'm not saying a word, except, boy - we've had a lot of lightning this year out east, haven't we?

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ilnadi
Captain

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452 Posts

Response Posted - 07/29/2008 : 09:37:48

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by skrenz
 Lightening can follow any path. There is no way of knowing if it actually traveled down the total length of the mast or jumped down one or all of the standing rigging or both.<hr height="1" noshade id="quote"></blockquote id="quote">. Agreed. Without a lot of math, think of it this way: after the lightning "jumps" 5000ft of humidity the material the last 30 ft is made of makes little difference. The grounding, wires, etc probably make more of a difference in the pre-lightning stage than during.

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