Don Casey Tip #12

Lightning

The technology of lightning protection hasn't changed significantly since Ben Franklin invented the lightning rod in 1752. The best way to protect boat and crew from this random force is still to provide the strike a straight, low-resistance path to ground. If the highest metal structure on the boat is properly grounded, the risk of structural damage or personal injury is extremely small.

Onboard electronics are, unfortunately, not protected. Lightning induces current to flow in any conductor it passes near, and a powerful strike even 100 yards away may induce currents that exceed the capacity of the low-current components inside most marine electronics. You can gain limited protection by twisting all electronics power leads so induced currents will tend to cancel. Electrical wiring should run perpendicular to bonding wires to minimize the inductive effect of current flowing to ground. Ground the chassis-the metal housing--to protect internal circuits and components from directly induced currents. A surge protector in the supply line may stop a limited range of lightning-induced power spikes. But despite every protective effort, if lightning strikes your boat, your electronics have only one chance in two of not becoming toast-so keep your insurance paid up.