Lightning Protection

[GordMay]

Understanding Lightning Protection ~ by Bill Laudeman
BoatUS.com Seaworthy magazine

What are the Chances of Lightning Striking Your Boat?
The following statistics are based on all of the BoatUS Marine Insurance claims for lightning damage over a five-year period. The percentages suggest the chances of the various types of boats being struck in any given year.

Auxiliary Sail : 0.6% (Six out of 1000)
Multi-hull sail: 0.5% (Five out of 1000)
Trawlers: 0.3% (Three out of 1000)
Sail Only: 0.2% (Two out of 1000)
Cruisers: 0.1% (One out of 1000)
Runabouts: 0.02% (Two out of 10,000)
Source: BoatUS Marine Insurance Claim Files

Good Old Boat Newsletter: December 2005
Good Old Boat Newsletter: December 2005

Seaworthy magazine reviews lightning claims data
There may not be much boaters can do to prevent lightning from striking their vessels, but there is an important step to take immediately after a jolt hits, according to the July 2005 issue of Seaworthy magazine, the quarterly BoatU.S. Marine Insurance and damage avoidance report. In “Lightning! Flash, BANG! Your Boat’s Been Hit – Now What?” Associate Editor Chuck Fort reviews five years of lightning-strike claims data from the BoatU.S. Marine Insurance claims files. What he found might surprise you or confirm your suspicions about lightning strikes.

The feature reports that in any one year the odds of your boat being struck by lightning are about 1.2 in 1,000, with 33 percent of all lightning claims coming from the sunshine state, Florida. The second most struck area in the country is the Chesapeake Bay region (29 percent), while Idaho, Nebraska, and 11 other states had no lightning-related claims.

The rate of lightning strikes for sailboats was about four boats per 1,000, while motorboats averaged 0.5 per 1,000. A surprise finding was that multi-hulled sailboats were struck more than twice as often as monohulls.

Interestingly, the files also showed that many boats equipped with lightning dissipaters were also hit, calling their effectiveness into question. Most electronics aboard a boat, it was noted, were not damaged by a direct hit but rather from surging electrical current created in the wiring by the strike.

While the story explains that some vessels can have little or no damage after a strike, an immediate hull inspection is a must because when lightning exits your boat, it can go through the hull itself or via a through-hull fitting. This may cause a gradual leak that could go unnoticed.

Often, boaters don’t know their unattended vessel has been struck or suffered collateral damage as the result of a nearby strike. The article reviews a claim in which lightning damage was found only after an amber LED light lit up on a battery charger — a light the owner had never seen before — and his depth sounder quit. Sometimes a damaged or missing VHF antenna is the only clue that an unattended boat has been struck. Chuck Fort also mentions that most vessels are not electrically bonded according to the American Boat & Yacht Council lightning protection standards. Boats built to these construction standards offer a more direct pathway for lightning to exit a vessel.

Photo (below) From: http://www.smh.com.au/ffximage/2006/...yacht470,0.jpg

[Cruisingdad]

Ok, Pblais, Gordon, and others, here is a question:

Why did the T-Hulls, though rare, blow out when hit by a lightning strike?

What caused it?

- CD

[GordMay]

The water, within a semi-enclosed through-hull is instantaneously heated (by the lightning strike) up to (or beyond) it’s superheat limit, causing an explosive flash boiling. The expanding steam (water vapour) takes up about 1,000 times the space of the water it replaces, causing a tremendous pressure wave, not unlike a boiling liquid expanding vapour explosion (BLEVE).

[Vasco]

I've probably posted this in an earlier thread years ago but here's my experience at being struck by lightning.

We were ten miles offshore on Lake Ontario about 60 miles from Toronto, heading home, when I saw the most god awful electrical storm approaching. After seeing two strikes off the bow I went below, got my position off the gps, tucked the slip in my foulies and went back up into the cockpit. No sooner had I done this than we were hit right at the masthead. I remember the smell and a sizzling sound - that was all my masthead stuff, red hot, going into the water.

I called the coastguard on my handheld, reported the strike and my position, told them I was going to check for damage and would report back in ten minutes. They said they'd send SAR out if I didn't report back.

On checking, we were not making water (a good sign). All the electronics except a small Garmin gps were out. The alternator was shot, nav lights out, vhf out, autopilot out. Luckily I was motoring already and the diesel was still chugging. I reported back to the coastguard and said I was proceeding to Toronto ( I didn't want the boat to be in a strange port with all the damage to be fixed). I told them I was on a handheld and we arranged a reporting schedule of every half hour as I had to conserve the batteries. They informed me that they had notified SAR and the unit (aircraft at Trenton) was on standby and would be out if we did not report. They also informed me that sometimes the damage was not immediately evident, such as nearly burned through keel bolts that could result in the keel falling off later. I thanked them for this thought and continued towards Toronto. I checked the bilge every half hour. When I got back to the club early in the morning I finally signed off with them. It was very reassuring to know they knew of our plight for the rest of the journey as we had to endure that storm for another hour and a half and then another eight hours before we got home. Since the autopilot was out I put the wheel brake on and corrected the course now and then as we were scared to touch the wheel.

Two things really helped. Having a handheld vhf and the fact that the Garmin still worked so I could give an accurate position every half hour. I don't know why the Garmin (hard wired) didn't go out except that it does not have a ground wire.

When we hauled the boat for inspection, paint was burned at all the through hulls (bronze) and gudgeon and pintle. This I found out is called "treeing", the familiar pattern which looks like tree roots. My mast is keel stepped and bonded to the keel bolts with a thick wire. The through hulls are not bonded. The lightning went through the boat from stem to stern as can be seen by the treeing. I was lucky, no holes.

All the mast wiring was shot, all instruments (including a Loran) except the gps shot. Nav lights shot. VHF shot. Alternator shot. Windex, vhf antenna and wind instrument fly gone. Magnetic compass way out. Headsail was burned on the luff (Harken foil). Sometimes the foil sections get welded together but did not happen in my case. I think I got off lucky.

I got real interested in lightning strikes after this and saw boats where water soaked rudders had exploded and had tons of pin holes at the water line when the lightning went through to the metal dock it was lying alongside. I also came to realize that there is only one thing to do when caught in a bad electrical storm...... PRAY. This is now my preferred lightning protection plan. So far so good.

[Cruisingdad]

Gordon,

That is my thought too. Now, why is that any different than a D-Plate? Yes, the water in a T-Hull is "more" than what is absorbed in a plate, but the principle is the same.

Viking,

I think the Dynoplate is a great product - for an ssb. Not for lightning. That part about them being a lightning protection, or whatever... well, let me just say this: I got a F150. Ford says it is a great family truck and gets 18 mpg. I beg to differ. THat is just marketing. I dont believe anything in marketing since they will push the "truth" envelope just enough to the edge to keep from getting sued.

- CD

[ssullivan]

Originally Posted by Vasco

I also came to realize that there is only one thing to do when caught in a bad electrical storm...... PRAY. This is now my preferred lightning protection plan. So far so good.

I would agree with this completely. When the thunder comes in, I just hang around and hope not to die that day.

It's a very strange thing to get used to. You have to accept your own mortality and say well... I might get hit by lightning and killed again today... let's see if I make it.

I read some article recently on lightning that suggested that people in open boats (runabouts) were more likely to be killed if struck. Good thing they come in at the bottom of the list Gord posted.

[Cruisingdad]

Viking and all,

Here is the information you wanted, per Valiant.

First, Valiant does not use a Dynoplate. They run copper strapping through their boats for Counter Poise, tying in their tanks, rails, etc for ssb/ham. Thus, they do not have that issue with a Valiant, at least V-42's/V50's.

Second, they have never had a boat struck by lightning with a plate on it, that they can recall.

Third, they have repaired many boats struck by lightning. They have seen it blow out a t-hull and sink the boat, blow out the depth and sink the boat, and blow out pieces of the hull and sink the boat.

I am going to make an assumption (READ AGAIN, ASSUMPTION) on how the boats sank: in each instance, it was the pressure build-up of water rapidly expanding/boiling which could not be released quickly enough.

This would be the same potential for a dynaplate. However, I guess the question could be how the plate would take the strike. If you put a firecracker in your hand and let it pop, you will hardly feel anything at all. If you do the same but squeeze down - you might lose a finger. Thus, where the pressure built and how quickly it was released (and where) would be critical in how much damage was done to the hull.

I hope that helps Viking, though it solves nothing.

- CD

[Alan Wheeler]

I dont believe anything in marketing since they will push the "truth" envelope just enough to the edge to keep from getting sued.

I think it because they all use large point marker pens. It's hard to stay within the "lines" when using a big marker pen ;-) :-)

In past discussion on the subject, I made a comment that I had heard of a Dynaplate distorying its'elf from a strike. That very affect of water boiling in an explosive way can damage the plate. But it was only something I heard in a very distant way and can not substantiate the report and can only confirm it as distant and foggy memory hearsay. (by the way, is that how you spell hearsay?) The same reason a tre can split apart in a lightening strike, is that the moisture within the tree is instantly vaporised and the trmendouse pressure will split the trunk.

[Cruisingdad]

Hey Alan,

Wasn't there (and maybe still is) a bottle brush company that has a guarantee: If you get hit by lightning, we will pay your deductible. That is how strongly we believe in our bottle brush, at $375..!!

So, knowing the chances of getting hit are very small, they sit there and rake in the money. And when the poor chap gets popped, well - what is a deductible (up to 2k, I think was their limit)??????

Thus, I have developed the shotgun cleaner brush. Much more powerful than the old bottle brush, and much more effective and easy to install. You don't have to stick this one on top of your mast, it goes on your head (while sailing - a great promotional tool by the way). And, if while sailing, you take a strike through your head, I will pay your health insurance deducitble - should you survive. However, in the even you were holding a dynaplate at the time, the warranty is void. (smile, sorry, that was for you Viking... just trying to have some fun, don't get mad!!!!)

- CD

[Alan Wheeler]

Don't sell one to that guy in the States that has been hit 11 times or something like that. The most funniest thing I have ever heard was that a local pub wouldn't let him inside in a thunderstorm for fear of a strike. The poor guy says he know's when he is about to be hit. He can smell the ozone around him. poor guy :-0

[ronbo1]

Lightning protection of boats and marine facilities

In addition to Gordo's excellent sources check out the above site. Though dated it provides good background in trying to understand lightning. One statistic it mentions is the chance of a boat being struck is highest in Tampa Bay, 4-20% of moored boats per year. Presumably if you own it for 30 years it's certain to be struck at least once.

Last year, my boat (w/ DynaPlate) in the Chesapeake got a side flash blowing out just the Hsb link between Raymarine units. The boat two slips down got the direct hit on the masthead losing 75G in anything electrical.
Three adjacent boats lost inverter/chargers presumably because all were plugged into shore power - a good reason to unplug at the marina.

[GordMay]

Professor Thomson's paper (cited by ronbo1) is the classic text for Lightning & Boats.

[senormechanico]

About 20 years ago, we set out for a visit to my father in law's place. We left our house on the Sammammish Slough to cross Lake Washington with 6 people in my son's 13' Boston Whaler. He had a speed prop on the 50 hp engine, so we couldn't plane.
We had to be satisfied with 5 knots going across the lake as it was a sunny summer day with light winds, puffy clouds, and we only had about 3 miles to go. About halfway across the lake I noticed that all the clouds seemed to be going from right to left all the way around us, and the sky was greenish overhead. Uh-oh.

The next thing I noticed was people's hair was starting to stand up on end.

Double UH OH!!!

I got the brilliant idea that if I stuck my hand in the water, it would discharge any static I had built up. As I did so, I asked one of our passengers if my hair laid down. Nope! I quickly pulled my hand out of the water. Everyone started praying and keeping their heads as low as possible while I kept the throttle on full. We were leaving a good sized wake and using a lot of gas, but we had to get out of the lake ASAP!

Just as we arrived at his dock, it started raining very hard with enormous raindrops. The rain splashes were at least 3 inches across on his dock.

We tied up the boat as fast as possible and ran into the house as lightning was all around us. We were all soaked to the skin in only about 2 minutes.

A few hours later after visiting in robes while our clothes dried, the sky cleared and the sun came out. We left to go home again, glad to be alive.

To make a long story shot, when we got to almost the exact center of our crossing, it happened again!! Hair standing up, clouds rotating around us, green sky. WHAT ARE THE ODDS??

We were the commodores of our local cruising club, and had previously obtained the local TV station's meteorologist Jeff Renner to do a talk at our next meeting. When I met him before the meeting and told him of our experiences, his eyes got really big. He said "You're lucky to be alive. Both times, you were at ground zero, and very close to a direct hit."


Needless to say, I'm convinced in the power of prayer!
Steve B.

[Cruisingdad]

Steve,

If you had only had the Shotgun Cleaner Brush (guaranteed to work or 1/2 your money back minus shipping and handling and restock fees), you would have been safe and could have continued boating in style.

- CD

[Alan Wheeler]

Hair standing up, clouds rotating around us, green sky.

Nah..it was a bad nightmare after watching "War of the Worlds" ;-) :-)