How NOT to light up a Weekender

[Tim Diebert]

.....what I am wondering is.....does anybody know...really know....if a small wood sailboat is susceptible to lightning strike?

I recon anything is.

BUT, how often does it happen...?

Is there something that can be done on a small boat without a hollow mast to run wires down to a grounding plate?

Plenty of lightning around here again this year. In fact, it is lighting up our province...again. This is the worst fire season on record. 350 fires burning right now. Most caused by 'dry lightning' strikes.

Just went through a long weekend with a major high firmly fixed in place. Not a lot of wind. Just a couple of hours sailing (95 F temps) each afternoon. Today a bit of a low has moved in and they are calling for some pretty wicked wind...cooler temps. And here my wife is taking off for three days on a solo camping trip...and taking the tow vehicle with her.

I am going to have to find a someone with a car and hitch I can borrow

[Dave R1]

Tim, I've read various things about sailboats and lightning strikes. Some say there's not much you can do while others advocate hanging a piece of chain in the water from a chainplate.

I think if you are going to do something--anything--I would put up a lighning rod on the top of the mast. Attach it electrically to a shroud or better both of them on a side and then connect the shroud electrically at the chain plate so you can run that piece of chain down into the water.

The thing is, lighning voltages are high enough that the shrouds might not be capable of carrying it all. Shrotening a 2000 foot or more spark gap by 15' really won't have much impact. If your boat is wet, you might end up in the path to ground.

Problem with this sort of thing is you won't know if it works until you need it. Obviously the best thing would be to avoid those conditions. What ever you do, be safe. We don't want to read about you in the paper.

[Tim Diebert]

Great info Dave. Thanks.

If you read about me in the paper, bear in mind I died having a great time.

Pretty hard to predict such an event around here. When and if I see (hear) this stuff coming it is a great idea (I guess) to get off the water...but, I know myself well enough that if the wind came up at the same time.....I would keep sailing. BUT....if the sailboat just down lake from me just vapourized, I would be dropping that mast as fast as I could.

[Dave R1]

Why don't you try to just sail where there are taller masts around. Hopefully they'd draw the firs so to speak.

You could do a Ben Franklin and fly a kite off the transom and drag a key in the water.

[Kudzu]

Take this for what it cost you (nothing). I discussed this a good bit with the fellows over at the local sailing club a few back. They said they had sat in the club house and watched lightning go over all the boats in the marina and hit the trees on the bank. 150-200 masts and 99% of the aluminum too.

Of course next week it may destray one sitting there too.

[Craig]

Tim this area is one of the worst for lightening in the country and I have never heard of a boat getting hit. I did have a Prindal rigging light up once though when the bolt hit the trees near by. Best thing is to take shelter in the cabin til the storm blows by.

[Russ Sylvester]

A very good friend of mine was aboard when it got hit and he said it was like somebody let a 12 gauge go off right next to his ear. A few seconds after the strike the VHF antenna and the globe of the anchor light fell into the cockpit. Fried all of the wiring going up the mast but the anchor bulb itself was just fine along with the VHF radio. Go figure.

I've read several articles that have all said that lightning is looking for a low impedance path to ground no matter what form that path takes. Hanging a chain from a chainplate into the water says that the energy will go down a shroud rather than the mast itself. The most popular idea is to wrap the chain around the mast and then over the side. This keeps the path the shortest and the lowest impedance. The biggest problem with a strike is the hull area directly under the mast. This area can get cooked or completely blown out which we all know the result from that happening.

Craig is right, Florida is the worst for lightning so this subject interests me greatly. I've come close a few times to being at ground zero and I can attest that it will scare the bejeezus out of you. Most times when it hits that close you don't even realize what's happening until it's over cause it only lasts a split second.

I'll see if I can find those articles and post a link.

Russ

[Craig]

An old jumper cable will work well also, is easy to store, and doesn't beat the hell out of the side of the boat. Just clip it to a stay and throw the other end over the side. You just never know with lightning so it best to run for safety if you can. Trouble down here is our bays are so big it may take over an hour to reach shore depending on where you are. If that is the case maybe the best idea is to heave to with a sea anchor off the bow, turn on therunning lights, close yourself in the cabin and wait it out. Here the worst of the lightning will only last a few minutes. Half hour later it is clear and a million again.

[kevgrn114]

You can get a diffuser for the top of the mast. Kind of pricey but if lightning is a common occurance for you it might be worth it.

http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&langId=-1&catalogId=10001&productId=13902

[Tim Diebert]

Thanks for all the info folks. Excellent stuff.

[Russ Sylvester]

That diffuser isn't gonna do anything to help unless you run something like a 0000 stranded ground wire from the bottom of the diffuser to the water. Look at buildings that have lightning rods on the roof. They will also have a VERY thick wire running down the wall to a grounding rod. The idea is to keep the energy outside the building.

Lightning has been measured to be anywhere from 1 to 50 kiloamps with a rise time measured in nanoseconds. That means that almost ANY inductance or impedance is going to produce a difference in potential that will burn through almost anything.

Russ

[RussMartin]

I think I'll weigh in on this one. While I've not had to deal with lightning vis-a-vis sailboats, I have had to deal with it in terrestrial broadcast (television and radio) settings.

You might wish to look at this article:

http://www.uscgaux.org/~auxcen/beacon/spring03BEACON.pdf

Even there, you'll see, there is disagreement--also some interesting statistical predictions.

A ground path and a dissipator (sometimes called a "diffuser") perform inherently opposite functions. The ground path safely sends the lightning where you'd prefer it to go (hopefully); the dissipator bleeds off charge by spreading it among a large number of points and/or surfaces so that lightning will not strike in the first place (hopefully). If a client whose life and/or equipment depended on it asked me, I would say: If the dissipator is not attached to a structure already grounded (such as a tower), then don't try to ground it.

[Tim Diebert]

Soooooo.....ya pays yer money and ya takes yer chances....

I won't be loosing any sleep over lightning at this point. Great info.

Thanks Lads.

[Konrad in Lincoln]

I know this is the obvious but...

Would it not be best to simply NOT be on the water when there's lightening?? :shock:

When we're sailing cats, the rule is: If you can hear thunder (no matter how distant) it's too close. Tie down the boats and stay way from them till it passes.

[Craig]

Konrad, you old hoser, where have you been? We've missed you. How's that baby?

[Dave Ruedel]

Got caught last year in a thunderstorm that came up out of nowhere - sunny one minute with light wind, dark, lightning, strong winds, and buckets of rain the next. Wife and crew warm and dry in the cabin while the nut at the helm is fighting 30 knot gusts and trying to keep away from the cliffs on the side of the lake, not that I could have seen them in 100 ft visability, the way it was raining, and all the time having visions of the mast looking like a burned-out match in the cartoons, and me blackened. Happily, it was over as fast as it appeared, leaving about 3 inches of water in the cockpit, a very wet skipper, and a dry crew. Prefer not to be in the boat when it is lightening, but sometimes you don't have a choice. And no, the weather guy with all his satelites, radar, computers, etc hadn't predicted it, unless you consider the CYA just in case "10% chance of rain" a prediction.

[RussMartin]

Well, lightning is fickle to the point of unpredictability.

You've probably heard that "lightning doesn't strike twice in the same place" (is that ever? or in the same month? week? day? storm?). This has been demonstrated and recorded to be false, repeatedly, but a lot of people still believe it.

You've probably also heard that lightning strikes the highest point in the vicinity. Again, not true frequently enough to be a rule. It seeks the shortest electrical path, i.e., the "path of least (electrical) resistance".

My personal rule, whether golfing or camping or backpacking or climbing or canoeing or sailing, has always been "be elsewhere; if you can't be elsewhere, be really small". The rule of thumb for TV and radio news trucks (the ones with the telescoping masts that have microwave links and/or satellite dishes on top) is much the same as Konrad states: If you can hear thunder, it's too close. Don't raise the antenna mast; if it's already up, get it down. If you don't feel comfortable waiting to bring the mast down, get far away from the vehicle.