Lightning

© 2003 Jeffrey E. Isaac, PA-C

From the Experts

When there are only a very few real experts on a subject, it is a rare and wonderful privilege to learn directly from one of them. Such an opportunity was presented when Dr. Mary Anne Cooper was invited to speak at the annual meeting of Wilderness Medical Associates instructors in October. Dr. Cooper is an experienced emergency physician and researcher at the University of Illinois at Chicago, and one of the world’s two or three leading experts on lightning and lightning injuries.

One of the benefits, and risks, of speaking directly to the source is that they sometimes share information that is not yet ready to print. One of the risks of dealing with something like lightning is that, just when you print it, something completely different happens. So, as I share what I’ve learned, please keep these caveats in mind.

Over an 80-year life span, your chances of being involved in a lightning strike are about 1:3000 (averaged worldwide stat). There is no statistical significance to someone being struck more than once. It’s just the luck of the draw and geographic circumstance. Specific people do not “attract” lightning more than others.

Metal does not attract lightning either. The only two factors that influence the probability of a strike are the height and isolation of an object. In fact, the probability of a strike increases by the square of the object’s height. Add a one-meter antenna to your 20-meter mast, and you increase your probability of being struck by 10.75%.

Devices claiming to reduce your chances of being struck, by bleeding ions or electrostatic charge off of your masthead, do not work. If the device increases your mast height, it will actually increase your probability of being struck. This opinion was rendered in response to my direct question on the subject, and was unequivocal.

Lightning progresses toward the ground or water in a series of stepped leaders, penetrating 30 – 50 meters through the atmosphere a split-second at a time until contact is made. The resulting column of ionized air becomes the conduit through which the electric potential between ground and cloud is equalized. This gives lightning a “visual field” of only 50 meters max. In other words, the stepped leader would have to come within 30 – 50 meters of your masthead to “see” it.

This observation explains why the Cone of Protection concept we’d been teaching is inaccurate. The idea was to locate yourself within the 45-degree cone below the top of a tall object, assuming that the object would be struck instead of you. Dr. Cooper dispelled this myth with a photograph of the space shuttle being struck on the launch pad in Florida. The lightning bolt curved around the huge lightning rod on top and into the base near the tail of the spacecraft. NASA has since re-arranged their lightning protection into a web of cables strung from the top of the gantry slanting outward to the ground. It sounds kind of like standing rigging, doesn’t it?

While metal does not attract a lightning strike, it does do a fine job of conducting it once struck. The best grounding system is a straight shot of metal conductor to a large (1 square meter, minimum) ground below the waterline. An aluminum mast stepped directly on a lead keel would be nice.

There is no truth to the idea that a grounding system increases your boat’s chance of being hit. If you do get struck, a robust ground system can prevent damage and injury. Just be sure to watch the storm from the cockpit, not while leaning on the backstay.

As you construct or evaluate your grounding system, remember that lightning does not like to follow sharp bends or corners. It will jump across or through a less conductive medium instead. The increased resistance will release heat, vaporizing any moisture in the material. This is how fiberglass or wooden hulls explode when struck.

As a side note, I will be interested in the results of lightning strikes on boats with fiber rope for standing rigging. Aramid fiber melts at a relatively low temperature. It is also brittle – I wonder what a blast of superheated steam would do to it.

Your best protection from lightning is storm avoidance. If you do get caught, spend as little time exposed to the thunderstorm as possible. Lying hove-to while it passes over you may be a better choice than running with it.

Of the people involved in a lightning strike, 90% survive. Of those, 70% may experience some type of permanent disability. The only direct cause of death from lightning is cardiac arrest. Burns are rarely serious. People do not turn into “crispy critters”. Secondary injury and death can occur as a result of falls or drowning following a strike.

Lightning injuries include everything you might expect from a nearby explosion. Superficial burns are caused by vaporized sweat. They tend to be more serious where the steam is held against the body, such as inside foul weather gear.

There is no special emergency treatment for a lightning strike, just treat what you see. If the victim was involved enough to sustain visible injury, or was knocked down by the jolt, seek follow up medical evaluation when possible.

Lightning victims do not remain charged. It is safe to handle them immediately. Even if the victim appears dead, attempt cardio-pulmonary resuscitation. Lightning acts like a defibrillator, stopping the electrical activity of the heart. It also will stop respiratory effort. Since the heart is somewhat automatic, it may restart on its own while you continue to supply air to the victim. Don’t give up until you’ve tried CPR for 30 minutes without restoring a pulse.