Lightning

Can Small Craft Sailors Protect Against a Strike?

Article By Gordon Gilbert

Not long after launching their MacGregor 26, Kera Jane, on Lake Kootenay in southern British Columbia in July 2009, Sumner and Ruth Patterson observed dark clouds rolling toward them on rising winds. In unfamiliar waters on a month-long trailersailing tour of Idaho and BC, the couple decided to seek shelter in what appeared to be a protected cove about a half mile away. On arrival they anchored the boat about 35 feet from shore.

Lightning and thunder increased and rain began to fall as Sumner rowed Kera Jane’s stern line ashore in his dinghy and tied it off to a tree. “The weather was moving in fast, and as the lightning intensified I became more concerned for Ruth’s safety in the boat,” relates Sumner. With lightning striking uncomfortably close by, he decided they both might be safer off the water.

He rowed back to the boat in driving rain, picked up Ruth and returned to shore with her. A few feet from the water were some car-sized boulders and trees, and the ground rose sharply uphill toward the highway that bordered the lake. “We felt we were better protected there from the lightning than out on the water with the mast sticking 30-something feet up in the air,” Sumner says. “It might have been a false security, but at least we felt better.”

The couple weathered the storm amongst the rocks through the evening. At one point the rain and lightning let up, says Sumner, but by the time they walked to their dinghy the storm intensified again and they retreated back to the rocks. Eventually, the thunder and lightning subsided and the couple returned to Kera Jane wet and cold. “It was late by then, so we dried off with towels, grabbed a quick snack and hit the bed after a long day,” he says.

Were the Pattersons right to leave their anchored MacGregor and wait out the storm ashore? Probably yes, says National Weather Service lightning specialist John Jensenius. “If the shore has some place such as a wooded area where you’re not the tallest object around, then you’re probably better off heading there ahead of the storm,” he advises. However, he adds, “Sailors should understand that anyplace outdoors is unsafe during a thunderstorm.”

Strikes on sailboats: How likely?

How big a threat does lightning actually pose to small-boat sailors? NWS statistics indicate that lightning killed from one to three people in boats (not necessarily sailboats) per year in the United States from 2000 through 2009, a small percentage of the approximately 35-55 people the agency says are killed per year by lightning in all types of outdoor activities nationwide. Jensenius says most of the boater fatalities were in fishing boats or other open craft. About 150-350 Americans per year were injured by lightning strikes in all types of activities during the 10-year period, according to the NWS.

Although reports of strikes on sailboats—and especially those causing injuries or deaths—are relatively rare, sailors should consider lightning a serious threat, Jensenius states. “It is something they should worry about. Certainly if you are in a small sailboat in a thunderstorm, you are at risk of being struck and killed or injured.”

Ewen Thomson, president of Marine Lightning Protection Inc., a Florida-based boat-grounding systems designer and installer, and a former associate professor of electrical engineering at the University of Florida, says he believes lightning probably kills about 10 or so people a year on or near the water, and he agrees with Jensenius that fatal strikes on sailboats are rare. “I generally hear of at least two fatalities a year, but invariably they were in an open boat,” relates Thomson, who has written a comprehensive bulletin, Lightning & Sailboats, for the University of Florida Extension Service.

Many more unreported sailboat strikes no doubt occur in which no one is hurt but the vessel involved may have been damaged. Robert Adriance Jr., editor of Seaworthy Magazine, published by the BoatUS Marine Insurance Damage Avoidance Program, agrees that lightning strikes on sailboats are uncommon. He says statistics based on all BoatUS Marine Insurance claims for lightning damage over a five-year period suggest that in any given year sailboats without auxiliary engines have a 0.2% (two out of 1,000) chance of being struck. That compares with a 0.6% chance for auxiliary sailboats, a 0.5% chance for multi-hulled sailboats, and a 0.2% chance for runabouts.

“I can only think of two fatal lightning strikes on sailboats,” Adriance relates. “One guy on a Beneteau was killed when he had his hands on the metal steering wheel and his head resting against the backstay, and another guy was stepping off his boat at the dock while holding onto a shroud.”

Lightning strike stories

My informal survey of small boat sailors via online and e-mail subscriber forums found only a few lightning incidents and a couple of close encounters. While damage to small craft was noted in a couple of cases, there were no reported instances of serious injuries or deaths.

Brian, the owner of a Precision 23, reports that his sailboat was struck while he and his family were anchored off Shackleford Bank in the Outer Banks of North Carolina. “It fried the VHF antenna and the radio and blew a bunch of fuses and light bulbs, but otherwise there was no serious damage.”

Another forum participant, Leif, notes that his 15-foot plywood catboat was struck atop its mast while tied along a seawall at his marina. He says the bolt continued down a stay to the stainless steel rub rail, then along the rail to the lowest point of the sheer, and then hopped from screw to screw down the side of the boat. “It blew the top plywood layer off along two lines of screws, but because the bottom had been glassed it did not sink the boat. I was so happy to have not been aboard.”

In British Columbia, a Montgomery 17 crew may have come close to being zapped, reports the craft’s owner, Tim. He, his son and a friend were caught in a thunderstorm on big Okanagan Lake. “We were heading toward a marina to wait it out, and at one point my son got up to get a better look at something and got a substantial shock from the rigging,” he says. “His reaction was enough that if he was walking forward on the side deck and used the stay as support, he might have reacted right over the side. The current was so strong that he was able to grab the boom and touch me and still pass the shock to me.”

Finally, one forum poster’s response to my online poll bordered on the surreal: Jack, a Hunter 23.5 skipper, says a San Juan 21 that was in a race in which he participated was hit by lightning during the event on the Indian River in Florida. “The strike came down the wiring for the masthead light into the fuse box,” he explains. “The box then sent a charge to the knot meter, blowing a hole in the bottom of the boat.

“The crew member was standing in the cabin in the open hatchway while the arcing flash caught her hair on fire, as well as the fuse panel,” Jack continues. “The captain threw his wife overboard, put out the fuse panel fire, plugged the hole in the boat with a towel, rescued his wife, then went on to rescue the crew of another boat that was knocked down in the storm.” One can’t help wondering if the heroic San Juan skipper was struck by something worse than lightning when he got home.

Can small craft be protected?

Jensenius and Thomson say the only certain way sailors can avoid being struck by lightning is to not be out during a thunderstorm. For skippers who venture offshore or cruise in remote coastal or lake areas where they can’t avoid potential exposure—and for owners who want to protect their boats sitting on moorings or at marinas—proper grounding of the craft and bonding of its major conducting components may provide protection, they say.

Thomson, an acknowledged expert in sailboat-lightning interactions, states that a well-designed and installed system will not prevent strikes but can reduce the chances that a hit will injure crew or damage the boat. “The idea of the grounding system is to divert the lightning current through a predetermined path so that it does not make its own explosive path through fiberglass, teak, crew members, etc.,” he notes in his bulletin, Lightning & Sailboats.

He continues that a grounding system may include an air terminal, or lightning rod, atop the mast (but this is not crucial for an aluminum mast, he says), down conductors (the mast serves this function down to the mast base), a network of conductors around the boat that includes a loop that encircles the boat, and grounding conductors that are both immersed underwater (these can be a metal keel, plates or strips) and installed just above the waterline (the latter being electrodes rather than plates or strips). “There must be several grounding terminals to distribute the current evenly around the waterline,” Thomson explains.

Tying components such as chain plates, bow and stern pulpits, metal toe rails, steering wheels, motor controls, antenna bases and ground wires for electronics into the system, called “bonding,” helps to prevent side flashes inside the boat (which may cause the most damage, fires and injuries during strikes) and protect the boat’s occupants and components, he adds.

With small, trailerable sailboats, the type of ballast also is an important factor in designing a protection system, Thomson says. “A metallic swing keel effectively brings the water potential inside and becomes a hazard if it is not bonded to the mast,” he explains. “That is, a side flash could spark from the mast base through a crew member to the keel if these potentials (mast and keel) are not equalized by bonding.”  Water-ballasted boats present another set of problems, Thomson continues. “Since the water in the ballast is a conductor, it presents a similar side flash hazard to a metallic keel, but bonding is impossible. Also, if the side flash does connect to the ballast water, exiting side flashes from the ballast to the water outside are likely to blow holes through the hull. In this case external lightning conductors become crucial.”

Two small, ungrounded sailboats were holed after lightning struck them and exited through their fiberglass hulls. Photos courtesy of BoatUS Marine Insurance. Thomson’s company, Marine Lightning Protection, installs grounding connectors like this SiedarcTM through-hull electrode above a boat’s waterline and metal strips below the waterline. Photo courtesy of Marine Lightning Protection Inc.

Thomson acknowledges that most small-craft sailors won’t spend the hundreds or even thousands of dollars a professionally installed grounding/bonding system may cost. At a minimum, he says, “If I had a small sailboat, the first thing I’d do is to add two electrodes above the waterline and wire the aluminum mast to them via aluminum straps down the sides of the cabin top.” (Note: Detailed boat grounding/bonding instructions are beyond the scope of this article. Please refer to the resource materials suggested in the sidebar.)

One of the best sources of information on how to properly ground a sailboat, says Thomson, is the National Fire Protection Association Volume 780-2008, Standard for The Installation of Lightning Protection Systems. “Read Chapter 8 (Protection for Watercraft),” he suggests. “It tells you what needs to be done.”

Some sailors say grounding works

Is there evidence that grounding systems work? Thomson says yes, that data he has collected from sailors whose boats were struck indicate that vessels with no protection system suffer more damage than those with a proper system. In addition, he adds, “There is no support for the argument presented by some sailors that they should not ground their sailboat because it will increase their chances of it being struck.”

At least two respondents to my online poll are convinced that grounding works. Ron of Texas reported the result of being struck while sailing his Balboa 20 on the Chesapeake Bay. “The previous owner had put a ground strap on the back of the compression post from the mast base to the keel pivot bolt as a lightning ground,” he explains. “When we were struck on the masthead, the shrouds and backstay glowed, and afterward we could smell burnt wood in the cabin. The back of the compression post was charred in a diamond pattern from the ground strap, and the strap was still very hot. With the boat back on the trailer, we found a hole burned in the masthead and the gel coat around the chainplates was slightly discolored, but there was no other visible damage.

“I am thankful to the previous owner for having installed the lightning ground,” Ron continues, “since no one was injured and the most serious damage to the boat were some huge pucker marks in the cockpit cushions. We were lucky that no one was in contact with the mast or rigging. Since then I have installed lightning grounds on every other boat I have owned. I am looking at my newly acquired Seaward Fox to determine how to install a ground and will probably put a copper plate on the bottom somewhere.”

Ron adds that a friend of his who sails dinghies has successfully used a simple lightning ground system. “He keeps three lengths of light chain with a snap shackle on the end of each, and when he’s in threatening weather he clips the chains to the shrouds and lets them dangle in the water. He has been struck twice and says the system works.”

Jack, who reported about the San Juan skipper who extinguished his mate’s flaming hair by throwing her overboard, says, “The next race we were in, we all had jumper cables with aluminum plates all ready to be tossed overboard in the event of a lightning attack. I’ve used the plate and cables many times since,” he continues, “but have not had or witnessed any strikes since then.”

Systems vary in type and effectiveness

Adriance of BoatUS Marine Insurance’s Seaworthy Magazine says one reason grounding effectiveness is so difficult to study, especially on small sailboats, is the wide variety in installations, from the rudimentary to the complex. “What is the system composed of and is everything on the boat tied in? We almost never see a boat with a plate underneath,” he notes. “Not only that, plenty of people will tell you that the current standards for yacht protection are not sufficient to do the job. With all the twists and turns the cables and wires have to take, it’s such a headache to try to ground a boat properly.”

Ewen Thomson adds that jumper cables attaching shrouds to plates in the water, for example, are not a good way to ground a boat. “It may be better than nothing, but you’re also asking for the mast to come down.”

Another form of protection for small sailboats, Adriance notes, may be to simply “make sure that your insurance premiums are paid. That sounds facetious but it’s the truth. You can’t really prevent being hit,” he points out, “and on a sailboat you’ve already got some protection from the mast. There’s very little chance that you’ll be killed.”

Low odds offer little solace in a storm

Knowing that sailboat lightning fatalities are rare does little to relieve your anxiety when the sky is black, an electrical storm is flashing directly overhead, and you’re a few feet from a 30-foot metal mast, says Sumner Patterson, who with his wife Ruth spent an evening crouched among the rocks on the shore of Lake Kootenay. “I don’t know what the answer is, as lightning is never the same,” he says. “But if you are out in situations like we were in, maybe you’ll want to do something to improve your chances of surviving a lightning strike.

“We were out on our sailboat for 45 days last year and had to deal with lightning on four or five of those days. After studying our options, we decided to install a Zen Pole marine lightning protection system, which is designed to discharge the strike at the surface of the water, similar to how lightning actually strikes the water.” •SCA•

Gordon Gilbert is a Milwaukee-based financial writer who loves sailing, kayaking and almost any other activity on or near the water. He and his wife own a 1983 Montgomery 17, Sapphire.

As appeared in issue #68

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