Radar/Lightning

KJ: your photo shows a foreground sailboat in front of a background lightning strike.
I well recall spending an hour watching a lightning storm deposit strikes on the land all around our anchorage, in a sailboat, where there were 20 to 30 other sailboats anchored. No boats were hit. We were frightened enough to don our floater coats, and to stay in the cockpit.
There is no predicting where a strike will actually hit, unless you have a proper lighning rod, one with experience. Most sailboats don't get hit, some do.

My family had chartered 42' sloop in BVI a couple of years ago. The first night we stayed in the marina at Tortola. There was a thunder/lightning storm so intense that had to register*ten on the Richter Scale. The thunder rolled and boomed like a volley from a battleship. And the lightning, OMG! It lit the sky up so bright you read a newspaper by it. A couple of times the whole boat shook.* The very tall mast on this boat was keel stepped which means it ran through the deck and was secured to the keel. It also ran through the center cabin, right next to the bunk. My sister and her husband were suppose to*sleep in there but the mast was giving off strange zinging and popping noises every time there was a strike near us, so they slept in the salon.* The storm raged for hours.* Scared the piss out us (can I say that?).* We were sure that we were going to take a direct hit, but luckily didn't.* The next morning we took a quick run to the market for some last minute supplies and saw that the whole town had flooded. One guy said he lived there all his life and that was just about the worst storm he had seen.* The rest of the trip was however, great.* KJ

Here are some links where you can learn more about lightning and how to protect your boat. I have a lightning rod on the top of my mast, and a large cable that runs into the water with a big copper plate on the end. I have a lot of cuts on the plate to increase the edge area, which is where a charge will dissipate. Can't use it while underway, but it's in the water while I'm docked or anchored.

http://www.kastenmarine.com/Lightning.htm
http://marinelightning.com/
http://www.lightningsafety.com/nlsi_lhm/lightning_rod_recent.html
http://www.lightningsafety.com/


I had more links, but a surprising half of them no longer work. Oh well, these should provide a lot of good information.

We use to live and cruise on*a sailboat.* We kept a pair of jumper cables that we clipped to the standing rigging when lightning storms were in the area (at anchor).* The idea was to give the lightning an easier path to the water.* Did it work, I have no idea for we were never hit.**We also put the laptops,*GPS and other removable electronics in the oven.*The only problem was I left a laptop in the oven and turned*the broiler on and cooked the lid of the laprop till it bubled.* The computer still worked.* I would use the oven again but put a tag on the gas switch next time.

Would the jumper cables or oven really do any good?

Has anyone here ever seen St. Elmo's Fire?

I guess that would be a no.

Larry M wrote:


Would the jumper cables or oven really do any good?

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Larry, that's funny.* We carried the same thing off shore, and I think the answer is no, they wouldn't help.* But I'm down with you on the concept!

*

Has anyone here ever seen St. Elmo's Fire?


Not on a boat , yes on an an aircraft in a snow flurry.

I see St. Elmos fire lots of times over the last 33 years in the air. Almost always in heavy precip, in IFR conditions. Its just a build up of static electrcity. Been hit by lightning several times, from mild to severe damage, but not to the occupants as we were in William Faraday's "cage".
My question for you all is, the mast on my trawler is stepped through the coach roof and down to the salon deck. I will of course ground it to a bronze plate on the bottom outside hull, but if it gets hit, is there a danger to people inside the salon?

stevensibs said:

I see St. Elmos fire lots of times over the last 33 years in the air. Almost always in heavy precip, in IFR conditions. Its just a build up of static electrcity. Been hit by lightning several times, from mild to severe damage, but not to the occupants as we were in William Faraday's "cage".
My question for you all is, the mast on my trawler is stepped through the coach roof and down to the salon deck. I will of course ground it to a bronze plate on the bottom outside hull, but if it gets hit, is there a danger to people inside the salon?

Click to expand...

You never can predict with any accuracy what lightning will do after it strikes an object. To answer your question it could injure people almost anywhere near or on the vessel. I wouldn't limit the area, the degree of damage or the range of damage a direct lightning strike can cause to a vessel or anyone on or near the vessel. I think it's a good idea to ground the stepped mast to the Bronze plate there are 2 schools of thought with lightning protection do nothing and since lightning generally seeks a ground an ungrounded vessel may not have lightning discharge in or at it at all, the next step is to bond and ground everything in and out of sight. However the one path you missed will probably be the area that gets the most damage from a lightning strike.
Bill

If I were going to put lightening protection on a mast that was stepped through the cabin...I would bond the points where the stays attached to the hull outside and run those straps down to a bronze sintered plate....actually if I was in the midst of a bad lightening storm with bolts hitting close by...I'd clamp a couple jumper cables to the stays and let them dangle in the water.

Anything to keep a spike from entering the cabin then heading for sea water. 2 bad things could happen with lightning in the cabin...where it hit people and where it tried to exit the boat.

I'd clamp a couple jumper cables to the stays and let them dangle in the water.

Better to bolt a heavy cable with a 2x2 or bigger copper sheet for overboard.

Not much area in cable clamps , and poor ampacity with steel clamps with a thin copper plating.

Yes.... but all you are doing is looking to "cause" a path for lightning ...a path of least resistance.....not actually carry it because that is almost impossible.

Some people have reported success with just shackling on lengths of galvanized chin.