Being Hit By Lightning - To Ground or Not

[artbyjody]

Originally Posted by BIRDBATH

This Has Not Been Tested, But If At Anchor In An Electric Storm, I Bend The Storm Anchor Chain Around The Base Of The Mast And Dangle The Anchor Over The Side. It Seems To Me This Would Divert The Strike To The Water And From The Existing Bonding System. The Existing Bonding Wires Are Not Too Heavy (they Are Imbedded In The Fiberglass) And The Grounding Element Consists Of The Shaft And Prop. The Anchor Makes Good Contact With The Water.

In Retrospect, I Should Also Do This At My Slip.

Let Us KNow WheN YouR Boat BlOWs UP or you Stand THEiR WEHILE IT HIts...

[coatiac]

My 2 cents as an electrician are that most damage caused by lightning strikes are due to a poor or improperly sized ground path. The best example I can give is when the stike happens to an "ungrounded" mast. Of course there are conductors up there, the mast being the best one, but if it isn't properly grounded, the the strike will usually start with a light or antenna wire, because there is a connection to ground with these circuits. But as soon as the strike is iniated, the small conductor will fail at some point, leaving the strike to find a new path, which then becomes the mast until arriving at the base, where it then jumps to the next closest conductive material. It is the failing of one path, and subsequent jumping to the next path that causes the damage.

Ground your sticks properly, keep the paths as atraight as possible, and keep your connections maintained.

[chucklesR]

Copper foil is (I think) the best grounding plate, doesn't need to be thick - hecks it's meant to be blown away. A thin, 3 inch wide or so, 'tape' of foil from bow to stern provides maximum linear footage for charge disapation. Connected to the mast with the heaviest gauge wire you can get to it - the foil only costs a few bucks and can be replaced every bottom job.

[nwr]

I installed the Forespar lightning dissipater brush on the mast of my Islander 37 Motor Sailor prior to a transit from New Orleans to Charleston SC via Florida in June 2003. We got caught in Sarasota Bay in the middle of a thunderstorm super cell that had lightning in all quadrants. we anchored and since i hadn't yet put in a grounding system put 2 automobile jumper cables 2AWG wire size with large copper clamps, into the water from the port and stbd main cap shrouds. lightning struck the water less than 100 yards from the boat several times in the next 1/2 hour or so and i could see a bluish ball of ionization glowing from the top of the mast in the gloom. i know we were the tallest thing within 5 miles but even with the grounded shrouds we didn't get hit. after the storm passed we continued on in the ICW and across lake Okeechobee. every night when we anchored i put the jumper clamps on for security and while there were several more storms none were as close aboard as in the Sarasota Bay. On several strikes i could see the steam come up from the water from the strike. it made me a believer. i'll be putting the suppressor/dissipater's on my recently acquired 45 ft ketch at the next haul out. Neal Richardson s/y Black Swan II (Islander 37 Motor Sailor) and S/Y White Magic (ALOA 45)

[sailingdog]

NWR-

The 2AWG jumper cables probably did less than zip to ground your boat, given the high resistance of the stainless steel used in shrouds and stays, and the low surface area of the clamping method... it was of almost purely psychological benefit if anything.

Chuckles-

The grounding strip/plate for a lightning bond system does generally have to be a bit heavier than most foils are. The best ones I've seen have threaded copper studs that go through the hull to the bonding system.

[chucklesR]

SD,
Gem's don't come grounded anymore than your Telstar did, I'm still in design mode.
I'm not wanting to add 100 pounds to my boat as I get 450lbs per hull = 1 inch of immersion, every pound counts. Granted thicker is better long term - I'm figuring I'll replace each bottom paint or if it gets blown away by a strike.

I'll report back when it happens.

[sailingdog]

A 1/8" plate of copper that is 2" x 24" isn't all that heavy.. You could install two of them and probably never have to replace them again. Have them installed with five 1/4" x 20 copper studs attached...and you'd be good to go. However, how you get from the mast, to the underwater part of the boat on a catamaran without encouraging sideflashes is a neat trick.

A trimaran is a bit simpler... and I'm planning on getting a strip made up for my boat.

[ppsavage]

Check the web at rule69blog (of course adding the www prefix and the dot com suffix). There are two pictures today of a 30 meter alumninum sloop at the Cat Club Marina in Antigua that was hit by lightning and burned to the waterline. Our boat was tied to the pier immediately in fron of them. I'm sure their mast was higher than ours!

[Loewe]

Can anyone say "snake oil" ? If any of the methods mentioned/marketed had any empirical data to support their effectiveness in a true scientific method, they would have cornered the market on said devices and insurance companies would give us a break for installing them. The safety recommendations given by knowledgable sailors are still valid if caught in those situations, but some of these antics are as effective as trailing a dead cat over the side. The will of Providence seems to be the ultimate determining factor in a strike. Most of us that actually get out on the water can testify to manifold experiences and the interesting thing is the absolute unpredictability of a strike and the amazing variety of results from one. Be prudent as you can and take your chances like everyone else. There are no guarantees.
Regards,
Red

[GBurton]

SD, how do you know that the jumper cables would do "less than zip" ?
If lightning struck the cap shrouds it is likely that the jumper cables would help a lot to transfer the strike to the water where it would be dissapated.

Grounding the boat is not possible anyway since its floating in the water not attached to the "ground"

Edit - in NWR 's case he was anchored...thus attached to the ground.....but his anchor chain may not have been bonded to his mast.

Originally Posted by sailingdog

NWR-

The 2AWG jumper cables probably did less than zip to ground your boat, given the high resistance of the stainless steel used in shrouds and stays, and the low surface area of the clamping method... it was of almost purely psychological benefit if anything.

Chuckles-

The grounding strip/plate for a lightning bond system does generally have to be a bit heavier than most foils are. The best ones I've seen have threaded copper studs that go through the hull to the bonding system.