Island Bound Traveller Writer, Storyteller
Gary Grieco is a freelance writer, avid reader, sailor, and motorcycle enthusiast based on Texada Island, British Columbia, Canada.
LIGHTNING STRIKE ON LAKE SUPERIOR
by Gary Grieco - email@example.com
Published Gam on Yachting 2006
Thunder Bay lays nestled on the west shore of Lake Superior. Its very name evokes images of Thor, that stormy Norse god, slashing about in the heavens with his magic hammer, delivering aimed thunderbolts at hapless sailors on the waters below. Thunder in itself may frighten, but does not damage. Lightning does.! Just ask any boater who has had the unfortunate and terrifying experience of being on the receiving end of one of Thor's shots. Sailors, Jerry and Susan Ventrudo from Thunder Bay, Ontario, received a direct hit to the mast of their Aloha 34 while moored to a buoy in Cloud Bay, on Lake Superior's north west shore. A premonition came to Jerry as the storm clouds gathered; perhaps as a result of a previous encounter. One small cloud resulted in an amazing display of St. Elmo's fire, discharging electrical energy from their boat's rigging into the air, and lighting up the top of their mast. The charge draining from the boat caused Susan's classic symptoms of having her hair stand on end. Both she and Jerry developed fierce headaches that lasted until they sailed out of range without further harm. They knew they were lucky. The storm intensified in Cloud Bay and they decided not to push their luck, but to leave their boat and spend the night in Jerry's brother's cottage on shore. Jerry Ventrudo describes what happened next. "It was raining as we were rowing to shore in our dinghy. We heard of blast of sound coupled with a bright flash that hit our boat's mast, and jumped to an upright steel post attached to the neighbour's dock. I knew our boat had taken a direct hit." This time the Ventrudos were not so lucky. The extent of the devastation to their boat became evident as they rowed closer the next morning. The weather vane, night-light, and aerial atop the mast were gone - "vaporized" in Jerry's words. When they arrived at their boat, the Ventrudos were astonished to find a charcoal zee; a shazam symbol from old Marvel comics, slashing the starboard hull from rub rail down to the wateline. They didn't discover the true extent of the damage to the hull until the boat was hauled and examined closely. Below the waterline, hundreds upon hundreds of pin holes in the gel coat were blown outward in a display of force. The millions of volts fused the circuit boards of the radar, sonar, and VHF radio. The master switch resembled a melted cone. "The inside of he boat wasn't bad, but the food locker was a mess," said Jerry. "The Tupperware was all in a jumble. The sugar and other condiments were fused, brittle, and mixed in crop-swirl fashion. The boat wouldn't start because of a burned out starter, but even if it had, we found out later that the driveshaft had been welded by the charge to the bronze shaft log." Flashes and bolts of lightning are basically caused by a difference in potential between the earth and clouds, measured in millions of volts created during thunderstoms. Sailboats are at most risk when the difference of potential is so great that it creates a condition called ionization, which allows the normally insulating air to conduct electricity. A voltage of 100 million volts or more is common in lightning strikes. Compare this to the few volts involved in electrolysis.
Proper bonding and grounding could save your boat from electrolysis, as well as saving your life. Susan and Jerry Ventrudo's new boat was not grounded. The builder was of the school of thought that grounding a boat could in some cases attract a charge. Their aluminum mast stepped to the lead keel may have acted as a giant lightning rod and helped dissipate the charge, but the experts recommend that you ground your boat to a large copper plate attached to the keel to dissipate the energy as quickly as possible. Grounding a boat will help prevent galvnic corrosion, which slowly eats away at your boat. But, a lightning strike occurs in a couple of tenths of a second and can cause havoc with your boat's hull and electrical systems. At worst, it could kill or maim you and your crew. A rusty prop or shaft is one thing; even a melted turnbuckle isn't so bad. The prospect of being killed by lightning on the water is chilling to contemplate. Oftentimes, boaters don't know that their unattended vessel has been struck, or suffered damage as the result of a nearby strike. This was the case with Bob and Donna McKay. Their 35' C7C sloop, Windwalker once received a massive jolt of 'runoff' voltage. In July 2005, on the northwest shore of Lake Superior in Sturgeon Bay near Thunder Bay, their boat was moored to a buoy in just over a fathom of water in front of their friend's island 'lighthouse' cottage, where the McKay's were visiting in the house with Brian and Bev Perigord during a thunderstorm. Coincidentally, Susan and Jerry Ventrudo own the other half of this island, and were present for the McKay's lightning strike. This is the same area of high frequency and intense lightning storms where the Ventrudo's Aloha 34 was struck.
The irony is that the McKays had just returned from an 1100 mile sailing trip to Collingwood on Georgian Bay without incident, when their boat's meeting with 'Thor' took place. Donna McKay tells their story. "We felt fortunate we were staying the night as guests in the 'lighthouse', and not on our boat. A small front passed through causing heavy rain for a couple of hours. There were two bright flashes of lightning followed closely by loud thunder which prompted us to glance at our boat, but nothing seemed amiss. The next day we motored to our own anchorage just a mile away, unaware that our boat had been struck by lightning, until we rowed for our shore, and Bob looking back at our sailboat swinging on its buoy noticed a black mark on the hull about eight inches above he waterline. He thought it might be a leaf or some dirt we had picked up, and headed back for a closer look. We found a hole the size of a 'twoonie', with the gel-coat blown outwards." Bob McKay thinks it was run-off voltage, "but the path is very hard to determine as there are no other marks or burns." It appeared that everything attached to the mast received current. The radar shorted out, and the VHF radio was blown, but the stern-mounted GPS and Auto Helm remained functional.
I asked Bob about Windwalker's grounding system, and if it provided any protection. "Our boat's 53' aluminum mast, step to keel, is grounded to the upper and lower shrouds, as well as the forward and aft stays. Did it help ? I think that it could have been much worse if things had not been grounded properly." Bob has a theory, "bad luck."
Lightning sometimes comes with an early warning system. The time between the flash and the thunder tells you the distance from the lightning. For each five seconds from the flash until you hear the thunder, the lightning is about one mile away. Experts say three miles away is too close. Find shelter. Is there anything a sailor can do to avoid being a prime target of 'Thor' ? Ground your boat, and don't go sailing when there is threat of a thunderstorm !! Of course, we can't always exercise that kind of control over our environment. There is no such thing as being lightning-proof, but common sense is perhaps the most under-used weapon against lightning threats.