Lightning strikes the mast
The worst moment in my sailboating life, recalls Richard Woods, was a lightning strike on the sailboat ...
In early July 2002, I was powering my 32-foot catamaran at Pamlico Sound, a freshwater lake on the US East Coast. All the last days it was hot and stuffy - high humidity was felt in the air, and thunderstorms rumbled around every afternoon.
On that special day, it was fresh in the morning, but by 2 pm the familiar huge clouds with anvils at the top reappeared. Not far off, straight ahead, I saw a dark streak of downpour, and in the west, it looked like a downpour was also gathering. I decided to wait until they both passed, but the clouds were everywhere.
Before I got to the edge of the fairway to anchor, a loud and harsh “crack” sounded directly above me, and I smelled a strong smell of ozone in the air (by the way, lightning does not make a thunder rumble above you, it sounds like a deafening “crack” "). A rain of fragments and fragments of fittings from the top of the mast fell on me, and I realized that lightning had struck the sailboat.
It became clear that I had a big problem. I anchored to get some relief from the shock and assess the damage. Immediately after the impact, I noticed that my four-stroke suspension began to work unevenly, and after I stopped it, it did not want to start at all. As expected, I found that I now had no working radio and electronic equipment - neither the radio nor Navtex showed signs of life. The autopilot ST2000 had a hole in the hull and didn't work either. I also noticed that my main compass started to give a 30 degree error. Sliding downgo downstairs, I found most of the fuses in the electrical panel melted. The smell of burning wiring was in the cabin. Fortunately, there was no fire.
Not a single lamp in the cabin worked - all the incandescent lamps simply burned out, the halogen ones exploded, scattering glass throughout the cabin, and the diode lamps evaporated without a trace. The brightness adjustment rheostat burned out.
All electronic clocks on board were showing the wrong time, including my personal organizer clock and electronic barograph. Investigating the situation further, I found a non-functioning CD player and refrigerator. And, finally, the strips burnt into the skin under the guard rails showed me the path of lightning through the ship. Having passed from the top of the mast along the shrouds and to the rails, she proceeded to the stern and went into the water through the rudders.
Then I was lucky - I was not injured. Good thing it wasn't raining and I wasn't holding on to anything metallic! Some local fishermen saw what happened and came up to me in their boats to ask if everything was all right. They said the lightning looked very impressive and set off spectacular fireworks from the top of my mast. They lifted me to the mast, where, to my joy, I did not find any damage either in the mast itself or in the shrouds and earrings of their fastening to the mast. However, the wind indicators, the top three-color light and the VHF antenna were completely destroyed or missing.cheered.
But, nevertheless, I was alive, and still had my sailing catamaran!
It was not difficult to walk a couple of miles to the nearest marina, but what happened required understanding of what happened and its consequences - I could go far from the coast with an autopilot and radar, plot and control courses using a chart plotter, and suddenly - "crack", and I have nothing. Not even a watch and a compass - even Columbus was better equipped than me in his time! Now I always carry a sextant, paper charts, and a mechanical watch on board.
The next day I managed to get a mechanic to fix the suspension, and after replacing the electronic ignition board, I had a working motor. True, a week later, his other electronic unit failed, which led to further expensive repairs. While outboard engines are more at risk from lightning strikes, modern stationary diesel engines also have electronic control systems and generators that suffer just as much.
Over time, it became clear to me that apparently intact instruments stopped functioning later. For example, my battery (which was only a year old) could no longer hold a charge and had to be replaced.
I slowly began the expensive procedure of replacing all the damaged appliances. A handheld GPS and VHF radio was first in line, along with a fishfinder, whose echo sounder I badly needed in the shallow waters of the east coast. The new log and the weather station could wait a bit. Another highlight was the refrigerator, which cost more to repair than its original price! It took a long time before I restored all my equipment, and it was a big expense.
Like most British sailboatsmen, I didn't give much thought to lightning protection on my sailboat until I left England, mainly because in northern Europe you encounter hardly a few thunderstorms a year. But even if you are not going to cruise to the coasts of Central Africa, where there are more than 200 thunderstorm days a year, you need to remember that in any areas of the world popular with sailboatsmen, you are always at risk of being struck by lightning.
Не станьте мишенью
More than 10% of deaths on cruising sailing sailboats are due to lightning strikes.
The sailboat, with her mast, looks like the most attractive lightning on the sea. Small craft suffer the most damage from lightning strikes because they are most often made of plastic and wood and are not properly “grounded” i.e. poorly conduct electrical energy of lightning into water. To reduce the risk, and practically negate damage to the boat, the correct lightning protection system will help - grounding the vessel.
By installing protection, we cannot make the boat inaccessible to lightning, we simply allow its energy to go into the water without harming the ship and people on it. In the event of a direct lightning strike, an electric current of 100,000 amperes and a voltage of 30 million volts passes through the mast and hull of the sailboat for less than half a second. This current tends to go into the water, and if the sailboat is not grounded, it makes its way, burning channels in dielectric materials and destroying electrical circuits and devices. Lightning always finds its way to water. She can get away through the rowingengine shaft, through the keel, outboard valves or breaking through the skin in the underwater part of the hull.
The organization of protection of the sailboat from lightning is based on the fact that the mast receives a lightning strike and transmits it through a conductor to a metal plate under water, through which the lightning energy goes into the water.
The mast creates a protective zone in the form of a cone around the sailboat, preventing lightning from striking below it - on the deck or in the cockpit. Since lightning tends to strike the highest object, it is necessary to install something like an antenna on the top of the mast - a bar of copper wire with a diameter of at least 6 mm, the top of which is not sharp, but blunt, and even better - in the form of a panicle, and is located above any device on mast top.
If your mast is metal, then it itself serves as an excellent conductor. It is only necessary to organize the connection of its spur to the "ground" by means of a copper conductor with a cross-sectional area of at least 50, and preferably 75 mm2.
In the case of a wooden mast, you either need to run a separate conductor of 6mm copper wire, or use (if available) a metal strap for the mainsail sliders for this purpose. All connections must be bolted, provide reliable electrical contact and be protected from corrosion. The earth conductor line should be as straight as possible.
In the case of a carbon mast, a separate conductor from the mast top to ground is also necessary, despite the fact that carbon conducts current. In fact, a lightning strike on a carbon mast without a conductor destroys it, because the carbon fibers, when passing a large current, are heated and delaminated in the surrounding and non-conductive epoxy resin.
Top shrouds can also work well as conductors as long as they are no thinner than 3 millimeters in diameter. An important condition must be met in this case - the lower ends of the cables must be electrically connected and carried to the "ground". In general, all massive metal parts at a distance of up to 1.5 meters from the conductor of the lightning electric charge must be connected to it in order to avoid “breakdown” of an electric arc on them.
The best "ground" is a bare metal case, but modern epoxy paints and primers are good insulation, so even they need to install ground plates.
I was struck by lightning in fresh water, which conducts electricity much worse than sea water, and is more dangerous. Therefore, when installing the ground plate, count on lightning in fresh water.
The ground plate is a 1-3 square foot copper sheet attached to the hull or keel and wired to the mast. It can be square or rectangular in shape. Unfortunately, you cannot install and grind the plate flush with the skin, because the best dissipation of electrical charge into the water occurs from the sharp edges of the plate, and not from its surface.
Sometimes on sailboats where there is no grounding system, during a thunderstorm, a piece of wire connected to a guy or mast is lowered overboard. This is a bad idea, as the wire does not have enough area in contact with the water to effectively transfer the lightning energy to it. As a last resort, on a small boat, such a scheme can be applied, provided that a copper plate of at least 1 square foot in area, submerged under water, is attached to the end of the wire.
It is unwise to use an engine screw as a "ground", even if it has a suitable area. In this case, a large current will go through the motor, which must not be allowed. An even worse idea is to organize "land" on outboard kingstones. There were cases when lightning pulled them out of the hull, and the sailboats sank.
Even with a good lightning protection system, electronic devices remain vulnerable. The huge potential of static electricity in a thunderstorm, the strongest lightning discharge current and the most powerful radio emission leave practically no chance for “delicate” low-voltage electronic equipment to survive a lightning strike.
To protect it, you can try to put a surge protector on each circuit, but only a real lightning strike can test its effectiveness. It seems to me that the safest and most reliable thing would be to simply turn off the devices from the network, but not just with switches, but completely disconnect them from the power supply and sensors. As my sad experience has shown, simply removing the fuses in the circuits may not be enough - a high-voltage discharge can easily pass between the contacts. For this reason, I no longer have "tightly" built-in electronicappliances and my refrigerator and watermaker have separate electrical connectors. I also manually disconnect all the wires coming from the masthead, including the navigation lights.
The only reliable method for protecting your electronic equipment from lightning strikes is actually very simple. Hide the instruments in a metal box, the so-called "Faraday cage". A useful feature of the device is its ability not to pass an electric charge inside. I use galley utensils for this purpose - an oven and a large saucepan. (You can make a special grounded metal box, which, by the way, can serve as a safe for you).
Now, as soon as I notice a thunderstorm coming, my chartplotter, radar, GPS, laptop and radio go into the oven. Then I disconnect the engine from the battery, remove the autopilot and steer the sailboat manually. Entering the harbor under sail and navigation "by eye" seems to me a low price for the saved electronics and engine.
Причина появления молнии
Most occurrences of lightning occur in the afternoon, when the moisture-saturated air heats up and, rising up, forms huge, up to 10 miles in height, cumulus-thunderstorm clouds with an anvil-shaped top.
- When heated air is raised to this height, the moisture it contains condenses and freezes, forming ice crystals. Rubbing them against each other creates a static electric charge. In this case, the upper part of the cloud receives a positive charge (+), and the lower one - negative (-). Opposite charges interact and attract. Therefore, when a cloud passes over water, its negatively charged lower part collects a positive charge on the surface of the water, which is transferred to everything that is on the water.
- This positive charge tends to be negative in the cloud and will be concentrated at the highest possible points above the sea - in our case, at the top of the mast.
- Lightning, which is an electrical discharge - a huge spark - occurs when the potential difference between positive and negative charges becomes large enough to overcome the resistance of air as an insulator between them.
- A lightning discharge with a potential difference of 100 million volts generates tremendous energy and can raise the temperature in the lightning channel to 30,000 degrees.
- Like any electrical spark, lightning also generates powerful radio waves and thunder.
Thunder - sound waves from a lightning discharge can do you a good job. Knowing the speed of sound propagation in the air (240m/sec) and counting the time interval between a flash of lightning and a roll of thunder, you can calculate the distance to a thunderstorm. For example, 30 seconds elapsed between visible lightning and thunder from it. Multiply 30 sec. at 340 m/s = 10200 meters or 10.2 km. This is your distance from lightning. If the next thunderbolt from lightning reaches you in less time, for example 25 seconds, and this trend continues, then this means that the thunderstorm is moving inour direction, and it is advisable for you to change course and prepare for a possible meeting with thunder and lightning.
If you are buying a new or used boat, be sure to check if it is equipped with a properly designed and installed lightning protection system. These (boat manufacturer's) systems are usually more efficient and cost less than later self-installed boats.
During a lightning storm, adhere to the following personal safety rules:
- before the thunderstorm approaches, stop all activities related to water sports or sports - swimming, scuba diving, surfing, fishing, etc. - lightning can strike a mile before the thundercloud approaches you.
- while on board, do not put your arms or legs overboard.
- Do not use radio or electrical appliances. Disconnect them from the network.
- avoid, as far as possible, contact with parts of the boat connected to lightning protection. Never touch two grounded objects at the same time, such as winch and backstay. In the event of a lightning strike, the current will pass through your body exactly in the region of the heart, which can be deadly. In thunderstorms, even wet synthetic halyards can be dangerous because they come from the top of the mast.
- know and be able to apply first aid rules for electric shock and cardiac arrest.