A “Faraday Cage” is a metallic enclosure that surrounds people and sensitive electronic “gadgets,” “gizmos” and “gilhickies” to protect them from damaging stray electrical discharges (electrostatic discharge) that might accompany nearby lightening strikes occurring in a thunderstorm. For example, a car can act as a Faraday Cage. The car protects the people in it from electrical discharge. If stuck on a bridge in a thunderstorm, stay in the car! The metal skin of the car struck by lightening will lead damaging stray electrical energy away from the car’s occupants.
On a boat, a number of possible Faraday Cages are available to protect sensitive electronic devices and electronic memory cards from possible damage. The bake oven in the galley of a boat can be utilized as a Faraday Cage. Disconnect your computer from power and from all peripherals, and place it – alone and unconnected – in the oven. The metal enclosure of the oven will protect the computer from any stray electrostatic energy that might otherwise damage memories or circuit boards.
Your microwave oven can also act as a Faraday Cage. Place your fully disconnected iPad, Android tablet, eReader, camera and/or cell phone(s) in the microwave during a thunderstorm. The metallic enclosure will protect these sensitive devices from any stray electrostatic energy that might damage them.
A metal 1-gallon paint can can act as a Faraday Cage. Place your hand-held VHF Radio, your hand-held GPS, your USB thumb drives, your back-up hard drive and any camera memory cards in a metal paint can. The can will protect them from stray electrostatic energy that might otherwise damage them. Of course, you can also use a metal ammunition container, commonly available at sporting goods suppliers.
The entire boat can also be set up to conduct electrostatic energy to a ground plate. That will route electrostatic energy safely into the water. This involves interconnecting all of the boat’s stanchions, railings, stays, shrouds, mast (if metal), boom (if metal), deck hardware (Samson Post, anchor rollers, anchor chain, boom crutch), decorative rail guards, etc, etc, etc, with #6 AWG or larger electrical conductors. This network is in-turn connected to the boat’s ground plate(s). These items – when methodically interconnected – create an enveloping shell (a Faraday Cage) around the exterior of the vessel, and ultimately act to protect occupants in the same way a metal shell of a car does. The Faraday Cage routes stray electrostatic discharges around, rather than through, the living areas of the boat where people and pets huddle up during thunderstorms. As you might imagine, this is vastly more easily accomplished at OEM fabrication-time for the boat, because the large conductors can be imbedded in the fiberglass and otherwise routed in conduits and/or protected and hidden. It is greatly more expensive and difficult to retrofit such a system.