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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

lightning protection - grounding

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greatescape
1st Mate

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USA
33 Posts

Initially Posted - 08/16/2005 : 16:38:19

I have a 1982 Catalina 25 fin keel and am not sure I have proper lightning protection. There is a heavy copper wire going from my instruments to one of the keelboats but what aboout the mast?

Any way to tell? Any way to do what's necessary?

Thanks
Scott - Great Escape

Scott

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 08/16/2005 : 17:00:41

Check with the manufacturer and see if that is a suggested grounding. If it is not required I would take it off. I would never turn my stick into a lightning rod either. If the gods want to take me I am going to make it harder than that!

Edited by - on

Happy D
Admiral

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921 Posts

Response Posted - 08/16/2005 : 17:33:52

While working on my 77, I found a heavy copper wire, like 4ga. or so, running down the inside of the compression post and into the forward port locker. One end was burried under the mast step and didn't connect to anything. Someone redid the area under the mast step and may have disconnected it. The other end was cut off in the forward port locker. Maybe it was intended to ground the mast. I have a swing keel so I don't know what was going on there. I just pulled it all out and discarded it.
Dan

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 08/16/2005 : 21:43:30

There are two schools of thought on this - You ground it and are safer if you get hit, but then you also attract the lightening. The second is to not ground it and not attract lightening, but risk the chance of damage if it gets hit. I know of two different boats that have been toasted within the past 3 years. One was grounded one wasn't.

I have a friend who survey's boats for a living and was previously in the boat repair business. His exact comment to me was I would never tell a client to ground his boat. So I asked him - "so you advise against it" and he replied " I would never tell a client not to ground a boat." He said he defers the question becuase its too much of a liability.

Edited by - on

Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 08/16/2005 : 22:02:19

There is no such thing. Prevention perhaps but protection . If it's going to hit it will . If you find yourself traped or caught out in an electrical storm get to shelter ASAP. If you cant then tale a Car Battery jumper cable attach one end to a mast head shroud and the other end to 1' square piece of diamond plate and throw it over the side. Get below and or stay in what they call the shroud of safty. Stay low and inside the shrouds and back stay . crouch . Been there done that and have the video . NOT FUN . If you want to ask questions about the strike my wife and I had E mail me at dgyoung_2000@yahoo.com

Edited by - on

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 08/17/2005 : 14:47:36

I was struck a few years ago and was/am not grounded. If you ground your boat you need to use copper lead/foil from each chain plate and mast base to a keel bolt.

Lightning (positive ions) is attracted by negative ions generated on the ground. They meet in the atmosphere, thus the bang and flash. On your boat, friction caused by a rope coil rubbing on a pulpit could concievably generate enough negative ions to attract the positive ions in a thunder cloud.

There is no recognized protection from a lighting strike. You can however, minimize the possibility of a strike by keeping loose gear stowed. You can minimize the effect of a strike by grounding usiing copper foil. Another method is to drape chain or cable off your upper shrouds and into the water. This is supposed to be effective.

Edited by - on

DaveC25
Navigator

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USA
152 Posts

Response Posted - 08/17/2005 : 15:35:39

Maybe there are lots of theories on it, but to me it seems that a bolt of lighting is a static charge with enough energy to jump several thousand feet through the atmosphere. That being the case, an extra 30 feet or so from the mast top to the water doesn't make a much of a difference. I think when boats get hit, they're just in the wrong place at the wrong time, and the mast sticking up in the air isn't as large of an "attractor" as it might appear.

Also, I don't believe "grounding" the boat to the water does much good because the boat, sitting on the water, would be at the same static charge potential as the water already....so it looks just like the sea to the thundercloud's static charge especially if it's wet with salt water. As a matter of fact, if you could keep the boat isolated from the water this would probably decrease the chance of getting hit since the lightning is trying to get to the water.

Also, damage to instruments and such is caused not from the lightning running through the instrument (well, it would be if that happened, but I imagine this usually isn't the case), but from the EMI pulse caused from the lightning bolt. The only way to shield from this is to have your instrument in a grounded metal box. Since this is not possible while being able to read the instrument, pretty much it's gonna fry if the bolt comes within close proximity to it.

One last bit.... if you did run cables down your mast to the ocean, and somehow the lightning got on these, the cables or shrouds would probably blow like fuses, and afterward the boat would still take the brunt of the strike anyways.

-DaveC25

Edited by - DaveC25 on 08/17/2005 15:48:07

mwalkup
1st Mate

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USA
79 Posts

Response Posted - 08/17/2005 : 22:15:16

Damn dave you an electrician or sumthun!
Just joshing nice insight.
Mike
83 t/r f/k

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 08/18/2005 : 09:01:33

Dave, doesn't the fiberglass act as an insulator, and grounding the boat to the ocean with a cable act as a direct conduit?

Edited by - on

DaveC25
Navigator

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USA
152 Posts

Response Posted - 08/18/2005 : 10:06:32

Fiberglass is a good insulator to around 600 volts or so...but we're talking millions of volts. After this lightning has travelled 5000 feet through the air, I don't think a few feet of fiberglass really makes much of a difference. It's very easy to build a static charge on fiberglass, which is basically what a lightning bolt results from in the first place.

As well, although the cable would act as a direct conduit when that million volts hits the mast, I think that even though most of the charge might follow the cable (before it melted) some of it would still go straight down through the boat and some of it wouldn't even be on the boat. And when you're speaking of millions of amps, "some of it" could mean thousands of amps. All of the air around the boat in that instance would be ionized so whether the boat was there at all I believe might not make much of a difference. So I think it'd just be fate whether or not the bolt hit the boat or not.

If you're ever seen lightning strike a tree you could begin to understand my thinking. The bolt hits the tree, then some it goes down through, some of it spiders of in different directions and strikes the ground around the tree. And some charges come off the main bolt and don't even hit the tree. It is because all of the air in the vicinity is ionized, so it's all charged.

But again, I'm not an expert in super high voltages such as lightning so don't go by what I say. These are just thoughts of mine.

-Dave

PS: Notice the lightning rod on top of the steel launch tower....

Edited by - DaveC25 on 08/18/2005 10:50:08

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 08/18/2005 : 10:27:33

For what it's worth, I've had my sailboats struck by lightning at least twice.

The first time I know of, the wooden mast had no dedicated grounding system. The lightning strike did a rather thorough job of converting the mast to splinters.

The screws attaching the chainplates were blown out of the boat, leaving what looked like bullet holes. The standing rigging had arc burn marks were the lightining had jumped air gaps, but otherwise didn't seem 'toasted'.

I made sure my next two sloops had grounding systems in place.

More recently, I noticed the windvane on my Catalina 25 seemed to be missing. I blamed the birds. (We have great herons, brown pelicans, wood storks, rosette spoonbills, osprays, comorants, anhingas, and various other large birds here.) When I got around to doing rig maintenance, I discovered that the remaining masthead accessories were spattered with the residue of vaporized windvane. No other damage has been found. The electronics work fine.

I plan to continue using a grounding system.

-- Leon Sisson

Edited by - on

Don B
Captain

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USA
317 Posts

Response Posted - 08/18/2005 : 11:32:56

Dave, let me see if I have this right...what you're saying is that by assuming the position (head between knees...)it's not going to do me much good.

Edited by - on

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 08/18/2005 : 11:51:39

I've seen two boats that were hit by lightening, I was sailing in the same race when the one was hit, and got to see the damage in the second. The first boat had softball size holes both fore and aft below the waterline. They were lucky enough to have someone with a handheld radio in a bag away from anything else because all of the boats electronics were toast. They didn't even really know they were hit until there was about 8 inches of water and rising in the cabin. They were towed in and hauled ASAP.

Here is the story from the second one. His boat was only months old - it was a beneteau 40 something and change.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/18/2005 : 23:04:29

Duane's surveyor-friend is explaining why virtually no manufacturers put grounding systems into their boats. Doing so could make them liable when the system is proved inadequate, or is even cited for "attracting" a strike.

Statistically, boats in fresh water are more vulnerable--probably because salt water, the better conductor, does a better job of reducing static charges on boats and is more attractive to lightning to strike directly. Several friends lost electronics from strikes very close to their unprotected sailboats (in salt water).

Cables dangling things from standing rigging is a dubious approach--stainless is a relatively poor conductor compared to aluminum, so the mast, if anything, is the key to a grounding system. Experts say that the system should have a large (1' square or more) copper plate on the outside of the hull below the waterline, with a very heavy wire running in a very straight line from the mast step to the a connector to the plate. Turns in the wire invite jumps through the hull. A less robust system invites a powerful surge it can't handle.

My observation is that the C-25 mast, being cabintop-stepped, with a dry wood compression post, several layers of fiberglass and almost 6' of dry air below it, shouldn't be very attractive to lightning. A strike is probably about as likely to go straight to the water a few feet from the boat as down the rig. But there are no certainties here... My "protection" is to figure out how not to be on the boat in a lightning storm--probably easier done around here, where they don't pop up as much as they do in many places. YMMV!

BTW, one of the most damaging strikes I've heard about around here happened to a boat with an "de-ionization brush" on top of the mast. So much for that theory...

Edited by - on

Dave Laux
Captain

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318 Posts

Response Posted - 08/19/2005 : 21:32:19

On our boat I have a 4 gauge wire running from the mast step to the ballast bolts in as direct a line as posible. I don't think that this will cover all eventuallities but I do believe that it will reduce the probability of major hull damage. As noted the induced curents will probably take out electronic stuff in the vicinity (a couple of boats over if a boat in a marina is struck).
BTW we had two thunderstorms on Lake Huron a couple of weeks ago with 84 knot winds. People we were with said they could see the ballast keel of our boat. This with all sail down. I was trying to get back to a boat with a less experienced crew. Had the 9.9 Yamaha High thrust cranked up and could not go upwind. Dave

Edited by - on

frogger
Navigator

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USA
184 Posts

Response Posted - 08/20/2005 : 07:48:09

I share a double slip with a Capri 26 which has an inboard and full electronics on board. Recently, the Capri was hit by lightning and all of his electronics, including the battery charger were fried. Amazingly, his engine would start. No one was aboard at the time of the hit, but debris and charred wind vane parts were scattered aboard both boats. He had no visible damage to other parts of his boat. He had no lightning protection installed. Hits happen.

Edited by - on

Dave Laux
Captain

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318 Posts

Response Posted - 08/20/2005 : 08:53:29

The engine on most boats is well grounded and the electrics associated with it are robust and grounded to the engine. Radios and instruments are full of voltage a current sensitive stuff and have choke coils and capacitors that act as transformers to induce curents in the circuit. Dave

Edited by - on

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 08/20/2005 : 09:18:47

Joseph (Frogger),

Get with the guy who owns the Capri and advise him to haul his boat. Experience with my boat and a friends boat that was struck by lightning tells me that when an unprotected boat is struck, the lightning only has one way to go, through the hull. In my case it exited on the boot stripe making dime-size and a quarter-size holes right next to each other. When I hauled the boat I also found about 30 pin-size holes in the bottom near the keel. The pin-sized holes are easy to spot because the paint "spiders" outward from them. The larger holes consist of pulverized fiberglass which narrow to tiny channels made by the charge as it passed throught the fiberglass from the lower shroud chain plates. It's an easy repair with a Dremmel tool and epoxy.

In my friends case, his Santa Cruz 27 actually sank from several large holes blown completely through the hull and reportedly several hundred pin-sized holes.

I say again, advise him to haul the boat and thoroughly inspect the hull.

Edited by - aeckhart on 08/20/2005 09:24:16

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