Lightning is frightening

LIGHTNING IS ONE of the most frightening things I’ve faced at sea. For me, it’s the equivalent of instantaneous death. From the first sight of those ominous cumulus clouds piling up on the windward horizon, it’s all angst and high drama. I know there will be no escaping from screaming wind, high waves, stinging rain, the crash of thunder, and lightning bolts crackling like the furnace of hell. The air will be filled with the smell of ozone. If it’s night--and thunderstorms are frequent at night on the deepsea tradewind routes--the stark outlines of strobe-like flashes will turn everything into blinding whiteness or stygian black in turns, and my night sight will be destroyed. I hate thunderstorms.

There is a lot that we still don’t understand about lightning, but it’s generally agreed that it’s the discharge of static electricity from one part of the thundercloud to another, between different clouds, or between a cloud and the Earth or a terrestrial object.

How does static electricity build up in clouds? They say  it’s just particles rubbing against each other, just as you can build up a static charge by scuffing your socks across an acrylic carpet. Enormous energy is created in cumulus clouds. They rise to great heights, creating areas of positive and negative ions separated by vast distances.

Air normally doesn’t conduct electricity, but when the potential voltage rises high enough, lighting will force its way through. A lightning flash may have an electrical potential of 30 million volts and a current flow of 100,000 amps. It’s hard even to begin imagining the sort of destructive power those figures represent.

Sometimes 100 or more individual discharges may be needed to find a path between areas of opposite polarity, and when this “leader stroke” reaches its destination, the heavy “main stroke” flashes off in the opposite direction--that’s the visible lightning.

When you’re on land, they warn you not to take shelter under a tree during a thunderstorm. That’s a dangerous place to be in, because the tree’s height makes it more likely to be struck. So what are your chances when you’re on the water, with a metal mast sticking up higher than anything else around?

Well, according to claims made to the insurance department of the BoatU.S. organization, an auxiliary sailboat has a 6-in-1,000 chance of being hit by lightning in a thunderstorm in any given year. Here are the odds for other types of boats: multihull sailboats, 5 in 1,000; trawlers, 3 in 1,000; pure sailboats, 2 in 1,000; cruisers, 1 in 1,000; runabouts, 1 in 5,000.

About 100 people are killed by lightning annually in the United States, and many are injured. Lightning starts some 75,000 forest fires a year in this country, and maybe more in this year of extra-dry weather.

Lightning is a weather phenomenon I could well do without.

Today’s Thought

I saw the lightning’s gleaming rod
Reach forth and write upon the sky
The awful autograph of God.
--Joaquin Miller, The Ship in the Desert.

Tailpiece

The luckiest man is the one who has a wife and an outboard motor that both work.

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

Dealing with lightning

A READER IN FLORIDA wants to know how to protect his boat against a lightning strike. “Worried,” of Fort Lauderdale, says a boat in his marina was struck the other afternoon and all its electronics were fried.

“I have a Catalina 27 and I’m concerned that I will be caught out during a day sail. What can I do to prevent damage to my boat or, lord forbid, me?”

Well, the oft-repeated advice is to get close to some boat whose mast is taller than yours, but that won’t work at sea, of course. I personally dangle a length of anchor chain from the backstay a foot or two into the water, more as a sop to the gods than anything based on scientific precepts. It just makes me feel better.

I can tell you that the general principle of lightning protection appears to involve creating a simple pathway for lighting to traverse if it does strike you, thus guiding it harmlessly to “ground” — which, in this case, is the water you’re floating in.

A grounded vertical metal conductor 10 feet high for every 17 feet of boat length will attract and divert lightning flashes, thus providing a cone of protection angled downward at 120 degrees from the top.

A sailboat’s metal mast makes a good conductor, but a wooden mast will need at least #4 AWG stranded copper wire, or a copper strip at least 1/32 inch thick, projecting at least 6 inches above the mast.

This conductor, or the metal mast must be connected as directly as possible to a lightning ground connection — a submerged ground plate at least 1 square foot in area. The whole of the conducting pathway should be as straight as possible: no sharp bends, or else the surging current will be tempted to take shortcuts, and perhaps blast through the hull.

Standing rigging, winches, guardrails, and pulpits, in fact all large metallic objects that are not tied into a bonding system, should be joined to the ground plate with stranded wire of at least #8 AWG.

As for yourself, keep your hands away from anything made of metal during a thunderstorm. If you have a metal wheel, wear rubber gloves. If it’s safe to do so, douse all sail and send all hands down below until it blows over.

Put handheld radios, phones, GPS units and any other sensitive electronics in an enclosed metal box (a primitive Faraday cage) to avoid damage.

Finally, it has to be said that lightning is very tricky stuff to deal with. It doesn’t read the human rule books, and doesn’t always behave as we think it should. But on the principle that some preparation is better than nothing, and that it will at least earn you points in the black box, the advice given above should prove helpful.

Today’s Thought
I saw the lightning’s gleaming rod
Reach forth and write upon the sky
The awful autograph of God.
— Joaquin Miller, The Ship in the Desert.

Boaters’ Rules of Thumb, #195
Spreaders should be higher at their outer tips than they are where they touch the mast. This not only looks more pleasing, it is also structurally stronger. The spreader should bisect the angle formed by the wire shroud as it passes over the spreader tip.

Tailpiece
“I can’t quite diagnose your complaint Mr. Brown, but I think it’s drink.”
“That’s okay, doc, I’ll just come back when you’re sober.”

(Drop by every Monday, Wednesday, Friday, for a new Mainly about Boats column.)

One strike is enough

ONE OF THE MOST frightening experiences I’ve ever had on a small sailboat was a violent night thunderstorm in the South Atlantic. We were many hundreds of miles from the nearest land at the time and our shiny aluminum mast was the highest thing sticking up in the air from horizon to horizon.

I doused all sail and we lay drifting broadside on, heeled over in gale-force gusts while bolts of lightning crashed,flashed, and sizzled all around us like lethal blue strobe lights.

I followed the advice of the British sailor and author, Eric Hiscock. I wrapped a fathom of chain around the backstay, which ran to the top of the mast, and let it trail in the sea astern. I don’t know whether that helped, or whether it was just one of your everyday simple miracles that we avoided getting struck, but I still remember how scared I was for the hour or so until it blew over.

What do you do in these circumstances to calm the intense apprehension, the awful conviction that you’re going to be blown to smithereens at any moment? There’s always the bottle of rum in the medicine cabinet, of course, but I read a better (well, alternative) method on the Cape Dory bulletin board the other day.

Duncan Cameron is a Cape Dory 27 sailor from Montreal, Quebec. He lectures in Strategy at the John Molson School of Business, Concordia University, in Montreal. He once got caught in a series of squalls between Point Judith and Fisher's Island while he was sailing between Rhode Island Sound and Long Island Sound.

“I'm going to guess the swells were up to 10 feet,” he said, “and I had to squint sideways to see in the rain and spray. There was lightning all around, more than I've ever seen, huge purplish forks at times. I fell off a couple of waves, and was clawing off a lee shore most of the way.

“The boat seemed to take the weather pretty well, and I was towing the dinghy too, but that worked out OK. I did wish I had full lifelines and a stern pushpit, because I was worried about trying to stay in the cockpit some of the time.

“As far as the lightning went, I just decided I was an ant in a big field, with a farmer walking around it. That way, I reckoned my chances of getting stepped on weren't that high. But there were times when the farmer walked all around me in me in a big circle, and he was stomping his feet pretty hard at times.”

Duncan was adopting the fatalist’s approach, of course, and frankly I can’t think of a better way to keep calm in the face of calamity — especially if you have saved up a few points in your black box. Remember Duncan’s method next time you get caught out in a lightning storm.

Remember, you’re the ant. The lightning is the farmer. Don’t get stomped on. Good luck.

Today’s Thought
Fate, show thy force: ourselves we do not owe;
What is decreed must be, and be this so. —Shakespeare, Twelfth Night.

Tailpiece
’Twas in the tropic latitudes
While we were talking platitudes,
As any sailor might.
We forgot to take our longitude,
Which was a grievous wrongitude,
So we did not reach Hong Kongitude
’Til very late that night.