During a thunderstorm it is not advisable to be on the open water. Especially for sailing ships, where the mast is usually the highest object, protection against lightning is enormously important, because lightning usually chooses the highest object. The probability that a sailing ship will be struck by lightning is low and no reason to panic, but both the damage potential and the chances are great enough to think more carefully about lightning protection on yachts.
Often no adequate lightning protection available Lightning protection systems are widespread in buildings, but less so in ships. Large yachts built according to class guidelines are more likely to have such a system than series-production yachts, which in most cases lack lightning protection. In most cases, the owner must take care of suitable protection himself. However, yacht lightning protection requires a lot of expertise, is time-consuming and cost-intensive. Even today's on-board electronics offer no advantage in this respect, because today the devices are all interconnected. In the event of a lightning strike, the current rushes through the entire network and can damage all the devices.
Danger for equipment and boat In addition to the technical equipment, the boat itself is also in danger. Lightning seeks the path with the least resistance to ground potential. If it hits a resistor, rudder blades can be split, masts can burst, and hull or keel formwork can be blown away. To minimize these risks, every yacht needs a lightning protection system.
The lightning protection system does not prevent lightning from striking, but the point of impact and path of the lightning current of the striking lightning can be better controlled. The tremendous current of lightning, which can reach between 20,000 and 100,000 amperes, must be conducted into the water by the fastest and easiest route. While this is less of a problem with aluminum and steel yachts, it is more complicated with wooden and GRP vessels.
The simplest solution for lightning protection A makeshift, quick solution is a copper conductor-clamp system that is attached to the mast, shrouds and stays. The ends of the cables hang 1.5m deep in the water. Lightning can be diverted over this, but the system is not comprehensive because the behavior of lightning is extremely complex. Lightning splits, strikes, and can also return to the ship from the water. Lightning can also strike from the outside, as via the shore connection in the harbor. An expert should always be consulted for appropriate retrofits.
The usual safety measures Of course, the usual safety measures always apply during thunderstorms: Approach harbor or sheltered bay (if possible), bathers must leave the water, haul in fishing lines, go below deck or make yourself as small as possible on deck (crouch down), wear shoes with rubber soles, do not touch any metal parts, do not handle the anchor chain, disconnect shore power connection in harbor, turn off main switch, disconnect all power and antenna plugs, disconnect cable connections to receivers at masthead. With good lightning protection on board and some safety measures in case of thunderstorms, hardly anything can happen on board.