lightning rod for sailboat

Yachting Monthly

• Digital edition

Sailing in lightning: how to keep your yacht safe

• In partnership with Katy Stickland
• July 22, 2022

How much of a concern is a lightning strike to a yacht and what can we do about it? Nigel Calder looks at what makes a full ‘belt and braces’ lightning protection system

Storm clouds gather at Cowes, but what lightning protection system, if any, does your boat have for anchoring or sailing in lightning? Credit: Patrick Eden/Alamy Stock Photo

Most sailors worry about sailing in lightning to some extent, writes Nigel Calder .

After all, going around with a tall metal pole on a flat sea when storm clouds threaten doesn’t seem like the best idea to most of us.

In reality, thunder storms need plenty of energy, driven by the sun, and are much less frequent in northern Europe than in the tropics.

However, high currents passing through resistive conductors generate heat.

Small diameter conductors melt; wooden masts explode; and air gaps that are bridged by an arc start fires.

Sailing in lightning: Lightning is 10 times more likely over land than sea, as the land heats up more than water, providing the stronger convection currents needed to create a charge. Credit: BAE Inc/Alamy Stock Photo

On boats, radio antennas may be vaporised, and metal thru-hulls blown out of the hull, or the surrounding fiberglass melted, with areas of gelcoat blown off.

Wherever you sail, lightning needs to be taken seriously.

Understanding how lightning works, will help you evaluate the risks and make an informed decision about the level of protection you want on your boat and what precautions to take.

Most lightning is what’s called negative lightning, between the lower levels of clouds and the earth. Intermittent pre-discharges occur, ionising the air.

Whereas air is normally a poor electrical conductor, ionised air is an excellent conductor.

These pre-discharges (stepped leaders) are countered by a so-called attachment spark (streamer), which emanates from pointed objects (towers, masts, or lightning rods) that stand out from their surroundings due to their height.

Summer is the season for lightning storms in the UK. Here, one finds early at Instow, Devon. Credit: Terry Matthews/Alamy Stock Photo

This process continues until an attachment spark connects with a stepped leader, creating a lightning channel of ionised air molecules from the cloud to ground.

The main discharge, typically a series of discharges, now takes place through the lightning channel.

Negative lightning bolts are 1 to 2km (0.6 to 1.2 miles) long and have an average current of 20,000A.

Positive lightning bolts are much rarer and they can have currents of up to 300,000A.

Preventing damage when sailing in lightning

A lightning protection system (LPS) is designed to divert lightning energy to ground (in this case the sea), in such a way that no damage occurs to the boat or to people.

Ideally, this also includes protecting a boat’s electrical and electronic systems, but marine electronics are sensitive and this level of protection is hard to achieve.

Lightning protection systems have two key components: First, a mechanism to provide a path with as little resistance as possible that conducts a lightning strike to the water.

This is established with a substantial conductor from an air-terminal to the water.

Components of an external and internal lightning protection system. Credit: Maxine Heath

This part of the LPS is sometimes called external lightning protection.

Second, a mechanism to prevent the development of high voltages on, and voltage differences between, conductive objects on the boat.

This is achieved by connecting all major metal objects on and below deck to the water by an equipotential bonding system.

Without this bonding system high enough voltage differences can arise on a boat to develop dangerous side flashes.

The bonding system can be thought of as internal lightning protection.

Rolling ball concept

Lightning standards, which apply ashore and afloat, define five lightning protection ‘classes’, ranging from Class V (no protection) to Class I.

There are two core parameters: the maximum current the system must be able to withstand, which determines the sizing of various components in the system, and the arrangement and number of the air terminals, aka lightning rods.

Let’s look at the arrangement of the air terminals first. It is best explained by the rolling ball concept.

A lightning strike is initiated by the stepped leaders and attachment sparks connecting to form the lightning channel.

The distance between the stepped leader and the attachment sparks is known as the breakdown distance or striking distance.

If we imagine a ball with a radius equal to the striking distance, and we roll this ball around an object to be protected, the upper points of contact define the possible lightning impact points that need to be protected by air terminals.

Lightning protection theories and classifications rely on a ‘rolling ball’ concept to define requirements, areas of risk and protected areas. Credit: Maxine Heath

The air terminal will theoretically provide a zone of protection from the point at which the terminal connects with the circumference of the rolling ball down to the point at which that circumference touches the water.

The shorter the striking distance, the less the radius of the rolling ball and the smaller the area within the protection zone defined by the circumference of the rolling ball.

The smaller the protection zone, the more air terminals we need. So, we use the shortest striking distance to determine the minimum number and location of air terminals.

Class I protection assumes a rolling ball radius of 20m; Class II assumes a rolling ball radius of 30m.

Continues below…

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Boat building standards are based on a striking distance/rolling ball radius of 30m (Class II).

For masts up to 30m above the waterline, the circumference of the ball from the point at which it contacts the top of the mast down to the water will define the zone of protection.

For masts higher than 30m above the waterline, the ball will contact the mast at 30m and this will define the limit of the zone of protection.

If Class I protection is wanted, the radius of the ball is reduced to 20m, which significantly reduces the zone of protection and, on many larger recreational boats, may theoretically necessitate more than one air terminal.

Protection classes

With most single-masted monohull yachts, an air terminal at the top of the mast is sufficient to protect the entire boat to Class I standards.

The circumference of the rolling ball from the tip of the mast down to the surface of the water does not intercept any part of the hull or rig.

However, someone standing on the fore or aft deck might have the upper part of their body contact the rolling ball, which tells us this is no place to be in a lightning storm.

Some boats have relatively high equipment or platforms over and behind the cockpit.

Protection classes to protect your boat while anchored or sailing in lightning

These fittings and structures may or may not be outside the circumference of the rolling ball.

Once again, this tells us to avoid contact with these structures during a lightning storm.

Ketch, yawl, and schooner rigged boats generally require air terminals on all masts, except when the mizzen is significantly shorter than the main mast.

The external LPS

The external LPS consists of the air terminal, a down conductor, and an earthing system – a lightning grounding terminal.

The down conductor is also known as a primary lightning protection conductor.

All components must be sized to carry the highest lightning peak current corresponding to the protection class chosen.

In particular, the material and cross-sectional area of the air terminal and down conductor must be such that the lightning current does not cause excessive heating.

The air terminal needs to extend a minimum of 150mm above the mast to which it is attached.

A graph depicting NASA’s record of yearly global lightning events. The Congo once recorded more than 450 strikes per km2

It can be a minimum 10mm diameter copper rod, or 13mm diameter aluminum solid rod.

It should have a rounded, rather than a pointed, top end.

VHF antennas are commonly destroyed in a lightning strike.

If an antenna is hit and is not protected by a lightning arrestor at its base, the lightning may enter the boat via the antenna’s coax cable.

A lightning arrestor is inserted in the line between the coax cable and the base of the antenna.

It has a substantial connection to the boat’s grounding system, which, on an aluminum mast, is created by its connection to the mast.

In normal circumstances, the lightning arrestor is nonconductive to ground.

When hit by very high voltages it shorts to ground, in theory causing a lightning strike to bypass the coax – although the effectiveness of such devices is a matter of some dispute.

Down conductors

A down conductor is the electrically conductive connection between an air terminal and the grounding terminal.

For many years, this conductor was required to have a resistance no more than that of a 16mm² copper conductor, but following further research, the down conductor is now required to have a resistance not greater than that of a 20mm² copper conductor.

For Class I protection, 25mm² is needed. This is to minimise heating effects.

Let’s say instead we use a copper conductor with a cross-sectional area of 16mm² and it is hit by a lightning strike with a peak current corresponding to Protection Class IV.

Sailing in lightning: This catamaran relies upon cabling to ground from the shrouds but stainless steel wire is not a good enough conductor. Credit: Wietze van der Laan

The conductor will experience a temperature increase of 56°C. A 16mm² conductor made of stainless steel (for example, rigging ) will reach well over 1,000°C and melt or evaporate.

Shrouds and stays on sailboats should be connected into a LPS only to prevent side flashes.

The cross-sectional area of the metal in aluminum masts on even small sailboats is such that it provides a low enough resistance path to be the down conductor.

Whether deck- or keel-mounted, the mast will require a low resistance path, equivalent to a 25mm² copper conductor, from the base of the mast to the grounding terminal.

Grounding terminal

Metal hulled boats can use the hull as the grounding terminal. All other boats need an adequate mass of underwater metal.

In salt water this needs a minimum area of 0.1m². In fresh water, European standards call for the grounding terminal to be up to 0.25m².

A grounding terminal must be submerged under all operating conditions.

An external lead or iron keel on monohull sailing boats can serve as a grounding terminal.

This owner of this Florida-based yacht decided to keep the keel out of the equation when is came to a grounding plate. High electrical currents don’t like sharp corners, so a grounding plate directly beneath the mast makes for an easier route to ground. Credit: Malcolm Morgan

In the absence of a keel , the cumulative surface area of various underwater components – propellers, metal thru-hulls, rudders – is often more than sufficient to meet the area requirements for a grounding terminal.

However, these can only be considered adequate if they are situated below the air terminal and down conductor and individually have the requisite surface area.

Metal through-hulls do not meet this requirement.

If underwater hardware, such as a keel, is adequate to be used as the grounding terminal, the interconnecting conductor is part of the primary down conductor system and needs to be sized accordingly at 25mm².

Propellers and radio ground plates

Regardless of its size, a propeller is not suitable as a grounding terminal for two reasons.

First, it is very difficult to make the necessary low-resistance electrical connection to the propeller shaft, and second, the primary conductor now runs horizontally through the boat.

The risk of side flashes within the boat, and through the hull to the water is increased.

Sailing in lightning: GRP hull, fairing filler and iron keel will have carried different voltages during the strike – hence this damage

An engine should never be included in the main (primary) conducting path to a grounding terminal.

On modern engines, sensitive electronic controls will be destroyed in a lightning strike, and on all engines, oil in bearings and between gears will create resistance and therefore considerable heat which is likely to result in internal damage.

However, as it is a large conductive object, the engine should be connected to the internal lightning protection system.

Internal lightning protection

On its way to ground, lightning causes considerable voltage differences in adjacent objects – up to hundreds of thousands of volts.

This applies to boats with a functioning external lightning protection system but without internal protection.

Although the lightning has been given a path to ground along which it will cause as little damage as possible, dangerous voltages can be generated elsewhere, resulting in arcing and side flashes, threatening the boat and crew, and destroying electronic equipment.

We prevent these damaging voltage differences from arising by connecting all substantial metal objects on the boat to a common grounding point.

One of the holy grails of marine photography – a direct lightning strike on a yacht’s mast. Credit: Apex

The grounding terminal is also wired to the common grounding point.

By tying all these circuits and objects together we hold them at a common voltage, preventing the build-up of voltage differences between them.

All conductive surfaces that might be touched at the same time, such as a backstay and a steering wheel, need to be held to the same voltage.

If the voltages are the same, there will be no arcing and no side flashes.

The bonding conductors in this internal LPS need to be stranded copper with a minimum size of 16mm².

Note that there can be bonding of the same object for corrosion prevention, lightning protection, and sometimes DC grounding.

We do not need three separate conductors.

Electronic Device Protection

With lightning protection systems, we need to distinguish electric circuit and people protection from device protection.

Even with an internal LPS, high induced voltages may occur on ungrounded conductors (such as DC positive) which will destroy any attached electronics.

A mechanism is needed to short high transient voltages to ground.

This is done with surge protection devices (SPD), also known as transient voltage surge suppressors (TVSS) or lightning arrestors.

Marine-specific SPDs are few in number and domestic models are not suitable for boats

In normal circumstances these devices are non-conductive, but if a specified voltage – the clamping voltage – is exceeded they divert the spike to ground.

There are levels of protection defined in various standards depending on the voltages and currents that can be handled, the speed with which this occurs, and other factors.

This is a highly technical subject for which it is advisable to seek professional support.

Most SPDs are designed for AC circuits.

When it comes to DC circuits there are far fewer choices available to boat owners although there are an increasing number for solar installations that may be appropriate.

There is no such thing as a lightning-proof boat, only a lightning-protected boat, and for this there needs to be a properly installed LPS.

Nigel Calder is a lifelong sailor and author of Boatowner’s Mechanical and Electrical Manual. He is involved in setting standards for leisure boats in the USA

Even so, in a major strike the forces involved are so colossal that no practical measures can be guaranteed to protect sensitive electronic equipment.

For this, protection can be provided with specialised surge protection devices (SPDs).

The chances of a direct lightning strike on a yacht are very small, and the further we are north or south of the equator, the smaller this chance becomes.

It’s likely your chances of receiving a direct lightning strike are very much higher on a golf course than at sea.

‘Bottle brush’-type lightning dissipators are claimed by sellers to make a boat invisible to lightning by bleeding off static electrical charge as it builds up.

The theory rests upon the concept that charged electrons from the surface of the earth can be made to congregate on a metal point, where the physical constraints caused by the geometry of the point will result in electrons being pushed off into the surrounding atmosphere via a ‘lightning dissipator’ that has not just one point, but many points.

It is worth noting that the concept has met with a storm of derision from many leading academics who have argued that the magnitude of the charge that can be dissipated by such a device is insignificant compared to that of both a cloud and individual lightning strikes.

It seems that the viable choices for lightning protection remain the LPS detailed above, your boatbuilder’s chosen system (if any), or taking one’s chances with nothing and the (reasonable) confidence that it’s possible to sail many times round the world with no protection and suffer no direct strikes.

Whichever way you go, it pays to stay off the golf course!

Enjoyed reading Sailing in lightning: how to keep your yacht safe?

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Lightning Protection: The Truth About Dissipators

About this time of year, when lightning strikes become frequent occurrences, we receive a good deal of mail asking about static dissipators such as the Lightning Master. These are the downside-up, wire-brush-like devices you see sprouting from antennas and rooftops in cities and towns, and more frequently, on sailboat masts. When these devices first appeared on the market, we did a fair amount of research to find out whether they realistically could be expected to spare a sailboat’s mast from a lightning strike. The following Special Report first appeared in the July 15, 1995 issue of Practical Sailor . Sailors also will be interested in reading about our discussion of conventional lightning protection systems in Getting a Charge Out of Lightning .

All sailors-except those who sail exclusively in the most northern but still liquid reaches of the Arctic Ocean, or most southern parts of the Antarctic Ocean-are well aware of lightning and its inherent risks. Lightning awareness generally takes one of two forms: (1) aware, concerned, resigned, do nothing or (2) aware, concerned, do something, and hope what was done will be more beneficial than harmful. In many ways, our ability to deal intelligently with lightning is little advanced from Benjamin Franklins approach. Most boats are built in compliance with the safety grounding and lightning protection recommendations of the American Boat and Yacht Council (ABYC). The highest mast will be well grounded to the sea through a copper wire of suitable size, which connects to a metal plate mounted on the hulls exterior surface. There may be a lightning protection air terminal mounted at the masthead. The terminal may take the form of a vertical spike with a sharp point or some more exotic shape and construction.

For years, a number of companies have started to aggressively market on-purpose lightning protection devices for use on boats. Although the devices appear to be little different from the forms that have been used on both aircraft and stationary constructions, some of the marketing claims have been rather innovative. Are these claims reasonable in light of what is known about lightning? Is the cost of protecting a vessel with one of these devices a good investment? Can you really placate Thor, the god of lightning?

How Lightning Occurs

First, let’s examine what we know about lightning. Lightning is a final result of the natural creation of an electrical charge imbalance in the Earths atmosphere. Simply put, the imbalance can occur due to the movement of the air, which like the movement of a person across a carpet, can cause electrical charges to be moved from one place to another. Imbalance in electrical charge causes a potential gradient to develop. This gradient can be measured and is usually expressed in volts per meter. The normal electric (E) field averages about 150 volts per meter. The field can exceed 1,000 volts per meter on a dry day. At this intensity, the potential difference from the head to the toe of a person 6 foot, 3 inches tall can reach 1,800 volts!

Since this is a static charge, it won’t electrocute anyone, but unfortunately, it also can’t be used to power the electrical consumers on a boat. The ability of the atmosphere to withstand or prevent a flow of electrical current when a voltage gradient exists can also be measured.

If, or when, the voltage gradient created by the charge imbalance exceeds the ability of the atmosphere to prevent a current flow, something will happen. In some cases, the charge will be dissipated harmlessly as a flow of ions. This flow may cause a visible affect under some conditions. Seen at night. St. Elmos Fire, an ethereal blue flamelike discharge, may be seen around any sharp points on the boat’s rig. In an aircraft, the blue glow may trail from wing tips and static discharge wicks (those round, pencil-like tubes seen protruding from the trailing edges of wings and control surfaces). An adventuresome pilot may be able to draw electrical arcs from the windscreen to his outstretched fingers. This type of electrical discharge won’t hurt you because the small electrical current moves through the surface of the skin, not through the internal organs of the body.

On some occasions, the build-up of charge gradient occurs very rapidly, so rapidly that little if any effective dissipation of the charge can occur before the stress applied to the air by the charge overcomes the ability of the air to resist. When this happens, the charge imbalance is relieved very quickly, by what we call lightning. Lightning is always occurring somewhere on the earth. The planet is always losing electrons. Although the current is very small, less than 3 millionths of an ampere per square kilometer, it amounts to an average global current flow of about 2,000 amperes. Nature balances this current flow by creating about 150 lightning strikes per second.

Lightning occurs both within the atmosphere, cloud-to-cloud lightning, and from the atmosphere to the earth, sky to ground lightning or the reverse, ground to sky discharge. Regardless of the direction of the lightning stroke, a great deal of energy is released as the electrical charge balance of the atmosphere-earth is restored. An average lightning strike consists of three strokes, with a peak current flow of 18,000 amperes for the first impulse and about half that amount of current flowing in the second and third strokes. Typically, each stroke is complete in about 20 millionths of a second. Once the lightning strike occurs, the air becomes a conductive plasma, with a temperature reaching 60,000 degrees. The heating makes the plasma luminous; in fact, it is brighter than the surface of the sun.

Measurements made of the current flow in the lightning strike show that 50 percent will have a first strike flow of at least 18,000 amperes (18 kiloamps, or kA), 10 percent will exceed 65 kA, and 1 percent will have a current flow over 140 kA. The largest current recorded was almost 400 kA.

Current flows of this magnitude are serious stuff and cannot be dealt with lightly.

The Risk to Structures

People who have boats and those who have towers or tall buildings share a common concern about lightning. Due to the altitude distribution of the air movement in the atmosphere that gives rise to the charge imbalance, things that are tall and stick up into the atmosphere are likely to be attractive targets as nature tries to rid itself of the charge imbalance. Since there are more tall towers than seriously tall boat masts, and since lightning-strike records are kept for these towers, we can use this data to ascertain the affect of tower height on attractiveness for lighting strikes.

The Westinghouse Co. obtained data for isolated, grounded towers or masts on level terrain, in a region that experiences 30 thunderstorm days per year. The number of strikes per tower or mast did not reach two until the height of the tower exceeded 500 feet. With a tower 1,000 feet high, the strike frequency was about nine. Towers more than 1,200 feet high were struck more than 20 times. Although the data may not be accurate for very small towers or masts, it appears that the chance of a typical 60-foot sailboat mast being hit will be quite close to, but clearly not zero. We know that there is always a chance of being hit by lightning; after all, people walking on beaches have been hit.

The ground wire, usually the topmost wire in an electrical power transmission line, is frequently hit. Trees are hit very often, sometimes exploding due to the instantaneous vaporization of moisture within the wood. Concern about lightning strikes on golf courses is sufficient to cause the Professional Golf Association to take special measures to ascertain the level of a threat of lightning and to stop play when the local electrical field strength and other indicators show a probability of lightning.

Charge Dissipation

Some people believe that by constantly discharging the charge build-up on an object, the magnitude of the charge imbalance can be controlled and kept to a level where a lightning strike will not occur. Continuous dissipation of static charge potentials is used in every electronics laboratory that works with sensitive integrated circuits and transistors. The workers wear wristbands of conductive material that are connected to the rooms electrical ground. Charges bleed off before they reach levels that might destroy the electronics.

Unfortunately, what works in a laboratory, with very modest static charge quantities, does not work in nature. Let’s look at the facts that govern the charge dissipation approach to undoing what Thor wants to do-blast us with a lightning bolt.

We can begin with some interesting evidence in nature. Trees have many thousands of reasonably sharp points. These points should operate somewhat like man-made charge dissipation devices. The evidence shows that trees, even small trees, are constantly being hit by lightning. Although trees are not terribly good conductors of electricity, they do in fact conduct to some extent, as witnessed by the lightning strikes they suffer. Suppose we substitute a carefully designed set of sharp points for the branches and twigs of the tree. We will make the sharp points of a material that conducts electricity very well, perhaps metal, or graphite (used in aircraft static wick systems). The idea is to take the electrostatically induced potential in the ground system and convey it to the sharp points where it can create ions in the air.

Sharp points create the greatest possible voltage gradient, enhancing the creation of ion flow. As the ions are created, they are supposed to be carried away by the wind, eliminating or greatly reducing the total potential difference, thereby reducing or eliminating the chance of our object being hit by lightning.

The problem with this approach is that the earth can supply a charge far faster than any set of discharge points can create ions. A bit of math will show that a carefully designed static discharge wick or brush can create a current, in an electrical field of 10,000 volts per meter, of 0.5 ampere. This is equivalent to a 20,000 ohm impedance (R=E/I: R=10,000/0.5 = 20,000). The impedance of a site on hard ground is typically 5 ohms. The ratio of the ability of the earth to supply a static charge is inversely proportional to the impedance of the conductor. In this example, the ratio of impedances is 20,000 : 0.05 = 4,000:1.

The earth can supply energy 4,000 times faster than the rate at which a static discharge brush can dissipate the energy! The impedance of saltwater is a great deal less, on the order of 0.1 ohms, making the theory of protection from use of static wicks even more suspect.

Another concept quoted by advocates of lightning prevention through the use of static discharge devices is that the wind will carry off the ions being released by the wicks or brushes. Not only will the wind-blown ions not prevent a strike, they may present a converse affect when there is no wind. In this case, they may migrate upward, making the air more conductive and possibly creating an attractive point of attachment for a step leader which is lurking above looking for a place to strike. Data indicates that step leaders, the precursor of the main lighting strike, don’t pick out a point of attachment until within about 150 feet of an object.

Scientific evidence of the behavior of the step leader indicates that it moves in steps about 150 feet long. This indicates that objects more than 150 feet above the surrounding terrain are more likely to be hit than those which are shorter (most sailboat masts). Until 1980, it was assumed that a grounded mast would provide protection against a direct lightning strike for all objects within a 45-degree cone whose apex was at the masthead. From that date the National Fire Protection Association has advocated that a different assumption be used (NFPA Code#78). This code recommendation assumes that a 96-percent protected volume exists adjacent to a grounded mast, with the boundary of the protected volume described by a curve having a radius of 150 feet (the length of one step in a step leader).

Makers of static discharge devices often quote evidence of many installations that once equipped, have never been hit by lightning. Unfortunately, these reports must be considered as anecdotal, not scientific proof of the value of the system. The fact is that the chances of a given mast or tower of the dimensions of a typical sailboat mast being hit by lightning are exceedingly small. The willingness of some makers of these systems (notably Island Technology, maker of No-Strike devices) to offer to pay the deductible amount on an insurance policy, or a fixed amount if there is no insurance coverage, is good financial accounting on their part rather than proof of the scientific value of their device.

For example, if you assume that the chances of an equipped vessel being hit by lightning are 1 in 1,000 (much higher than actual probability) and you charge purchasers as little as $10 more than normal for the product, you will have accumulated a $10,000 reserve from which to pay the $1,000 deductible amount on an insurance policy.

This income to cost ratio of 10:1 is somewhere between very good and wonderful. Given the price being charged for some of the devices, which offer to pay up to $1,000 toward the deductible in the event of a lightning strike, the ratio of income to probable cost for payout in the event of a lightning strike is more on the order of 100:1, or greater.

Recommended Practices

What should you do to protect your boat from lightning? The best advice available today is to follow the practices recommended by the ABYC for both lightning protection and grounding. Installation of a good lightning protection system wont hurt. If you like the idea and appearance of a particular kind of static discharge device, sharp points, brush or whatever, install it.

When in an active thunderstorm area, you may wish to have all personnel stay as far from shrouds and the mast as practical, and refrain from using electrical equipment. Some skippers may wish to disconnect electronic devices from all connections to the boat, power and antennas, although in the event of a direct strike, even this may not protect the increasingly sensitive solid-state devices used in this equipment.

And If You Play Golf…

The real risk from lightning appears to be greater for those who play golf than for sailors. The practice at most golf tournaments held in areas where lightning is common is to employ various weather monitoring systems to provide some advance warning of a coming storm or likelihood of lightning. A company appropriately called Thor Guard offers a lightning prediction system that monitors the electrostatic field in the nearby atmosphere. The system compares the monitored data with a stored data base and predicts the probability of a lightning hazard in an area up to 15 miles in radius from the monitor. This system is really not practical for use on a boat, although it could be used to provide warning for an area in which a small boat race was being sailed. It would appear reasonable that, with the very large amounts of money involved in delaying a major golf tournament due to the chance of lightning, static dissipation devices would be sprouting from the fields and woods if they could be shown to work.

The chances of being hit by lightning are very low. There is really nothing you can do to dissuade Thor if he takes a liking to your masthead. You might install an electrostatic field strength meter, or calibrate the hair on the back of your head. When the needle indicates a high enough field strength, or when your hair stands up straight enough, give everyone except the helmsman their favorite drink and invite them to watch the show.

For more on on board electrical systems, grounding, and lightning protection see our ebook Marine Electrical Systems – The Complete Series available in our online bookstore .

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On watch: this 60-year-old hinckley pilot 35 is also a working girl, 35 comments.

I remember reading about this stuff from the Florida Lightning Research Laboratory back in about 2005. We were living on a Catalac 10M at the time and debating with a “licensed” Marine surveyor who thought the little whisk brush like devices were the Cat’s Meow. But even grounding the mast on the catamaran is questionable due to the bridge deck and high energy not liking to turn corners. In 10years cruising never heard a good answer. 🙁

When I was leading the design of an aircraft antenna for Inmarsat communications which was to mount under the fibreglass fairing at the top of the vertical stabilizer we were concerned about lightning strikes. We could not use the heavy aluminum straps used on nose radar domes as this would have degraded the performance of the antenna. We found that a strip of copper shim washers which were not touching each other and supplied as a self adhesive strip could provide lightning protection without interference with the antenna. I understood that this was something invented by a Boeing engineer. The theory was that at very high voltage the strip would be conductive enough to discharge the air near it so that lightning would not conduct near it.

watched a boat hit by lightening in a race. The strike took out the UHF antenna; twirling it like a baton. The boat was chasing us. When we returned to the clubhouse at the Bristol, RI yacht club, the captain was unaware his yacht had been struck. Taking down the mast revealed the entirety of the top of the mast work was melted. No injuries.

Does it make sense to store electronic devices like computers, tablets, or smart phones in the oven during a thunderstorm?

Theoretically, yes – Faraday cage.

yes, a magnetic pulse protection case

A particularly poor article with advice written with poor knowledge of the subject matter. Ion dissipators have been used in the broadcast antenna and aircraft manufacturing industries for decades. Are they bulletproof? Nothing is, however, your main argument seems to be that if it’s not bulletproof then they shouldn’t be used at all. A properly designed sailboat with grounding straps and ion dissipators will encounter far far less lightning strikes. It’s almost as if this article was written by a salesman who wished to increase his commissions. This article should be withdrawn!

Do you have ANY real-world data to support your terribly convoluted implication that ion dissipators reduce lightning strike frequency or even severity? Your reaction is just like that people give when they have a paradigm in their field that is being challenged and they can’t refute the challenge. FACT: The article addresses claims that are unsupported with conclusive evidence. Those claims are refuted to a varying degree with real-world examples suggesting dissipators do not add value as well as mathematically-based models that suggest they do not. FACT: You have offered *nothing* to support the notion that ion dissipators reduce strike frequency or even severity. Your haughty attitude is worth nothing in the quest for a common basis for agreement (a basis of commonly acceptable evidence and logical or probabilistic analysis).

I add that your insulting complaint about the author’s motivation actually makes no sense – it is inherently self-contradictory! It’s almost as if *your* comment “…was written by a salesman who wished to increase his commissions.” Your comment should be withdrawn! How would the author make money by *reducing* sales of an item that provides a so-called solution when there are not even other competing types of products to provide that solution.

Let’s add one final note. You seem to think longevity of use proves effectiveness. That’s a foolish belief. Casting spells was *and is still* used by people to protect themselves. Prayer is believed by *many if not most people* to be a protective method with statistically significant results no less! Toxic elixirs were believed to help heal people for millennia until proven otherwise. Items providing more specific protections have also been around for centuries and yet eventually proven to be useless or harmless. Particularly when money is to be made *or esteemed “expertise” to be had*, humans will promote beliefs that run counter to reality. Don’t presume such behavior is justified just because it persists. You are not a child – you know that. So take that to heart and stop acting like such motivators are not an influence on (and perhaps the ONLY reason for) the sales of ion dissipators.

Thanks for the great academic review. I guess many of us are really interested in the ‘practical’ (sounds familiar? :)) bottom line recommendations for sailboats, not so much for golf courses… And somehow the clear message got lost within the text; what works and to what level, the costs, other means of protection and damage prevention while cruising and at the dock/mooring.

The article seem to leave a void. I was reading it for the same info. Thanks for posting.

It seems clear to me that the take-away from this article is that ion dissipators lack justification beyond making some people money and being “security blankets” for customers (or worse, show-off items for fools). The author has *not* chosen to tell you what to do, but should any article really do that if the author trusts the audience to make the right choice for themselves (if maximally informed). Choice of action is your own responsibility.

This might sound a bit naive but does attaching heavy duty battery cables to the upper shrouds at the deck and letting them dangle in the water help dissipate a lightening strike to the top of the mast? Or, prevent one for that matter? I tried this while crossing the Tehuantepec in Southern Mexico, Pacific side, when I went through a lighten storm where lightening was hitting the water all around me at a rate of about once every second, believe it or not. It lasted for a good two hours. I was the only sailboat out there. Does anybody know if the cables might have made a difference, maybe by dispersing ions or something like that? Or, if hit by lightening, would the cables be able to direct the charge to the water? Thank you

I have heard the same thing and I do attach heavy duty cables to my shrouds and drag them in the water (shrug) no idea if it achieves anything as I’ve never been struck by lightning I figured it can’t hurt ! Or can it ?

20,000 : 0.05 = 4,000 : 1 ?? Um, maybe….. 400,000 : 1 ?

Otherwise, very informative article. Thx!

I think that 0.05 was supposed to be 5, so the 4,000 would be correct. Where would the 0.05 come from if it is not a mistake?

I agree the article left me hanging with no course to follow. How deadly are lightning strikes on sailboats? Should we just rely on insurance to replace damaged equipment? What steps can we take during a storm to protect life/property?

Steve not sure what protected your boat in that storm,,,,frightening . I am an engineer but no lightening expert.

Here is my lightening story. We have an Islander 30 MKII in an end slip at McKinley marina in Milwaukee. Our neighbor was a visiting catamaran from Africa about 45 feet long on the face dock across from our boat. The masts were about 30 feet apart. Prior to the storm I recall talking to the cat owner as he had a serious cable from the mast into the water. Said it was for lightening protection with a large copper plate in the water. That night his mast was hit by a lightening strike. The next morning we went to check things out. The strike destroyed everything electrical or electronic including appliances etc. on the catamaran. Melted portions of his masthead that rained down on his deck left burn marks. After hauling the cat there were hundred black soot holes at the waterline. All needed to be repaired. The only thing that happened to me was the circuit breaker on my boat was tripped. Breakers on the dock were tripped also. No electrical or electronic damage for me. Essentially the neighboring boat took a hit for me. The strike must have created quite an electromagnetic field to trip breakers. Got lucky on this one.

Your vessel might have even been contacted by a weaker branch of the same strike. Close-up views of lightning strikes show they can have multiple points of contact, with some channels much brighter (presumably carrying much more current than the dimmer/narrower ones).

Can a well-grounded mast actually attract a strike? Our 41′ Morgan O/I was anchored at Cape Lookout NC with more than a dozen others, our mast just average height but grounded to a bronze plate. We were the only boat hit, and the water under the hull boiled orange!

An experienced surveyor, who had seen a number of lightning-damaged boats in the course of his career and made note of the protection measures in place on each, said to me, “Bottom line, lightning’s gonna do what it wants.”

A couple of thoughts on boats and lightning and the lack of specific recommendations. Me; live in low lightning area, trailer sailor and amateur radio operator. I installed an outdoor antenna a year or so ago on the house. A child of the Midwest, I took lightning protection seriously. Found a bunch of info on line, some good and some,….well, less so.

Key things that stood out; + kinda like Descarte’s argument for believing in God. the liklihoods may be small, but the consequences can be grave. +there are maps of lightning liklihood out there on line + Electricity follows the path of least resistance. Lightning is so electrically huge that it will explore all possible paths. Provide the easiest, most direct path possible for a lightning strike to reach ground that guides the current away from people and sensitive gear. Here that meant two stranded 2/0 leads (about 3/8″ diameter) from the antenna bracket directly to individual ground grounds which were then “bonded” to three ground rods serving the house wiring with about 90+ feet of #4 solid copper (smaller diamater #6 meets code but, some of the literature recommended #4 to be on the safe side). The antenna coax where it enters the house in a metal junction box was separated from the jumper that attaches to the radio by a “lightning arrestor.” The arrestor and surrounding metal box are directly grounded (#4 solid copper) to one of the antenna rods located directly under the box. + the concept of path step distance; if I am standing outdoors close enough to a ground rod or down wire, and the antenna takes a hit, the current in the soil or the wire may be strong enough to kill simply by going up one of my feet and down the other or grounding through my body. See pictures of dead cattle standing next to a barb wire fence that was hit by lightning. If I am standing out on the wet hull of a sail boat and the mast takes a hit…..maybe the same would apply. Moral here; stay as isolated as possible from the paths lighting might follow. + more ground rods are better than fewer for disapating the current into the surrounding soil. How this translated into ground plates on boats, dunno, but more might be better than fewer there as well. +British and European lightning structural protection standards have been regarded as more robust than our NFPA standards. Dunno about boats, but might be worth investigating. +soils vary in their ability to absorb electrical current; probably the same holds with fresh vs salt water. Ground rods do corrode in the soil over time. Pouring salt around a ground rod increase electrical transfer to the soil and also decreases ground rod life. Not recommended. Better to add more ground rods. +if an electrical storm is on the way, and I happen to be on the premises, I disconnect the radio from its coax antenna lead _and_ its power source (two paths for lightning). Also, unplug the power source from the wall outlet. A surge protector might not block juice coming in on the ground wire. +I have not placed the radio in a microwave. That solution I have seen offered for EMP protection, provided that the power cord is cut off to avoid acting as an antenna for high voltage RF input.

That’s about all I can think of of terms of main points. My fellow hams do not use the same level of lightning protection, but seem to regard mine as along the lines of the way to do it. Good luck on coming with with systems for sailboats

Hope useful, Full sails, Ole

A couple of thoughts on boats and lightning and the lack of specific recommendations. Me; live in low lightning area, trailer sailor and amateur radio operator. I installed an UHF/VHF outdoor antenna a year or so ago on the house. A child of the Midwest, I took lightning protection seriously. Found a bunch of info on line, mostly good and some,….well, less so.

Key things that stood out; + kinda like Descarte’s argument for believing in God. the liklihoods may be small, but the consequences can be grave. +there are maps of lightning probabilities out there on line for land masses, perhaps also for the oceans + Electricity follows the path of least resistance. Lightning is so electrically huge that it will explore all possible paths. Provide the easiest, most direct path possible for a lightning strike to reach ground that guides the current away from people and sensitive gear. And even then, keep your fingers crossed. Here, that meant two stranded 2/0 leads (about 3/8″ diameter) from the antenna bracket directly to individual ground grounds which were then “bonded” to three ground rods serving the house wiring with about 90+ feet of #4 solid copper (smaller diameter #6 meets code but, some of the literature recommended #4 solid Cu to be on the safe side). The antenna coax where it enters the house in a metal junction box was separated from the jumper that attaches to the radio by a “lightning arrestor.” The arrestor and surrounding metal box are directly grounded (#4) to one of the antenna’s grounding rods located directly under the box. + the concept of path step distance; if I am standing outdoors close enough to a ground rod or down wire, and the antenna takes a hit, the current in the soil or the wire may be strong enough to kill simply by going up one of my feet and down the other or grounding through my body. See pictures of dead cattle standing next to a barb wire fence that was hit by lightning. If I am standing out on the wet hull of a sail boat and the mast takes a hit…..maybe the same would apply. Moral here; stay as isolated as possible from the paths lighting might follow. + more ground rods are better than fewer for disapating the current into the surrounding soil. How this translated into ground plates on boats, dunno, but there as well, more area might be better than less. +British and European lightning structural protection standards have been regarded as more robust than our NFPA standards. Dunno about boats, but might be worth investigating. +soils vary in their ability to absorb electrical current; probably the same holds with fresh vs salt water. Ground rods do corrode in the soil over time. Pouring salt around a ground rod increase electrical transfer to the soil and also decreases ground rod life. Not recommended. Better to add more ground rods. How lightning grounding plates on a salt water boat might interact with Zn anti-corrosion plates…..dunno. +if an electrical storm is on the way, and I happen to be on the premises, I disconnect the radio from its coax antenna lead _and_ its power source (two paths for lightning). Also, unplug the power source from the wall outlet. The surge protector might not block all those Amps coming in on the ground wire at high Voltage. +I have not placed the radio in a microwave. That solution I have seen offered for EMP protection, provided that the power cord (now an antenna) is cut off to isolate the metal case from high voltage RF input. Probably work for lightning as well.

That’s about all I can think of of terms of main points. My fellow local hams do not use the same level of lightning protection, but seem to regard mine as along the lines of the way to do it. Good luck on coming with with systems for sailboats

Last point; ground (earth) rods are recommended to be spaced horizontally at least 2x the length of the rod, to better maximize current transfer to soil (minimizing overlap of the electrical fields emanating from each rod). For standard 8 foot rods, that equates to 16 foot spacing. How that translates into size, shape and spacing of grounding structures on a boat electrically connecting to the surrounding water might be a useful question to explore. Again good luck on coming up with systems for sailboats.

Thank you. Best explanation I’ve read about lightning. Shame there’s no definitive answer, but I think there’s not much we can do about lightning. Been through Tehuantepec at the wrong time of year (July), bolts everywhere, but never hit. My best story was in Costa Rica, early ’70s, aboard our Lodestar Trimaran ketch, wooden masts with S.S. masthead fittings, lightning all around, and close, and I hear a buzzing sound, look up and we have a glowing ball on both mastheads. Saint Elmo’s Fire. Basketball size on the main and grapefruit on the mizzen. Every close strike made them flare up and buzz louder, then they would return to “simmer”. This went on for over an hour. Finally, everything died down and they went out. It was extraordinary and colorful to watch, but I was pretty nervous steering with our S.S. tiller.

High altitude mountain climbers are supposed to try and get off the peaks before the lightening begins; usually by noon. If you get caught in a storm with lightening and can’t get down below treeline or into some type of depression, you are taught to keep away from your ice ax and for sure don’t leave it attached to your pack with the spike pointing up. Then crouch down as low as possible with legs and boots touching each other so you don’t have as convenient a way for the strike to go across your heart from one leg to the other. Maintain a low crouch and only touch the ground with the two boots together. No hands. Then between strikes, run down-hill like the devil is after you.

I don’t think that would work on my Catalina 27 though.

As a life long sailor, golfer, and electrical engineer who has a more than average understanding of lightning and potential protection from it, here is the 10% you need to know as a sailor:

– Mast top static dissipaters are worthless and, as the article points out, could have a negative effect. – Proper bonding of your mast and shrouds to a hull mounted grounding plate is a worthwhile project. With that said, a large strike will overwhelm even a well designed and installed grounding system.

This has usually been an academic subject as most of my sailing has been done is areas not prone to lightning storms. However, on 8/15/2020 we got caught in the most hellacious lightning storm I have ever been in off the coast of Big Sur after leaving Carmel, CA. It is the same storm that created the massive wildfires still ravaging northern CA. Had the most extreme lighting bolt I saw that night make a direct hit our boat, a 36′ cutter, it would have likely destroyed our boat and killed the crew. The good news is the odds of getting hit in a bad lightning storm are likely better than the 1 in 1,000 actuarial odds per the insurance companies but are probably not 1 in a million either.

Finally, this is as well written and article on this subject that I have seen.

To the catamaran on fresh water, sorry, fresh water isn’t conductive enough for grounding. Salt water is an electrolyte however. https://nemasail.org/news/7279551

reading all of this it made me question why proper grounding should be a positive thing to do ?! …since electricity always follows the path of least resistance, why should I create a perfect path to ground and even attract a lighting? within a storm cloud negativ electrons are seperated from positive charged ions. The lightning is a visible path of current. On the boat, it is suggested to insulate yourself … so why not insulate the boat? instead of creating a path to ground? Or why not even give the mast and rigging a low positive charge on purpose? As far as I could understand, St. Elmo’s fire is a visible corona discharge. A positive charged object leaking charge. That means if you see St. Elmo’s fire on your masthead you are protected ?, since your equipment is not negative charged and the lighting would not be drawn into it? I might have completely wrong, but I could not find proper answers, yet. Most of these articles repeat the same stuff. I found the comments here more interesting.

Interesting.

But are you ignoring voltage gradient in this analysis? The voltage difference between the source (the cloud) and the sea creates a volts/metre gradient. Your ion dissipation doesn’t have to reduce the charge to the voltage of the cloud. It just has to reduce the voltage by more than the voltage gradient over the height of the mast, to make the top of the mast appear less polarised than the sea around it, (or less polarised than the boat anchored 100m away). It just has to do a better job than the dissipation of the surroundings. Happy to be corrected if I’m missing something.

I suspect that dissipators work better on catamarans as the masts swing less, and don’t move out of their own ion cloud. Am I visualising this right?

Hi, it’s sad this marketing pseudoscience and I am glad of this well documented article. It’s sad that we normalize this situation and keep using tension masts or sloops and rely in insurance, because this is a real problem for blue water sailing and so this must be one of the main factors in sailboat design.

1st. boats must be multisail as ketches are, using light freestanding masts to me removed in case of electric storm, also can be used some sort of small thick rounded mast with large boom as sort of wide short sail in that scenario. 2nd. all electric equipment must be located in a magnetic pulse protection case (with spare parts of sensors to be replaced), because this is the real problem with in situ strikes and nearby strikes, and even fireworks.

this risk is real and im glad is less frequent than thought

also, the boat could use a bow freestanding mast with a ground plate in the bow to avoid boat and personal damage

Not to be contrary, but charge dissipation DOES work as a mitigation. Looking at it slightly differently – if the earth were a perfectly conducting sphere, the probability of a lightning strike would be equal everywhere. Add hills, mountains, towers, buildings, trees, hay stacks and other objects on the surface and each accumulates charge build-ups over the perfectly conducting earth. The idea is to put an “air terminal” on the object you want to protect to lower the probability of a strike – not to eliminate it which would be nearly impossible. In other words, drop the charge difference from your tower or mast relative to another location or object. This is a lot like using camouflage to hide objects from the air. An extension of this is used in power plant and substations where there are aerial lines strung from towers above the working of the plant to “pull away” the potential strike from the critical components. Also a taller object well grounded yields a so called “zone of protection” which is roughly a 45 degree angle from the top of the object to the ground. Things inside are less likely (there’s that probability word again) to suffer a strike or damage. In grounding a number of communications installations on mountain tops for commercial and government installations, the so called “bottle brush” type of dissipation has proven (through experience) the best. A lightning rod must be continually sharpened to dissipate. If not, it becomes dull and accumulates charge rather than dissipates it. The bottle brush has around a hundred stainless steel points which are thin and dissipate well – and last over time. The real key, however, is not the bottle brush, lightning rod or other dissipation device, it is the construction and connections to the Earth Electrode Subsystem of which there are many types and rules – Another topic.

A joke i like to tell: with sailors you can talk about religion and politics but not about anchoring or lightning preotection… We have been struck four times on our 38′ catamaran. Two times within 2 minutes, these strikes nearly totaled the boat (in insurance terms) as it wiped everything electric, from electronics to engine wiring harnesses and caused fiberglass damage. The third time it “just” took out the electronics, the fourth the inverter. What we learned: we have over 50,000 miles and twenty years onboard and have sailed or been at anchor thru many a breath taking lightning storm. All of the lightning strikes have occured at docks while hooked to shore power! The fourth strike hit our neighbors mast who had a dissapator talked about in the article. He had, ironically, told me the day before how it had kept him safe for two years… Strikes 1&2 hit us rather than the boat next to us whick had a 10′ taller mast. Strike 1,2&3 had us the farthest boat out on the pier. Insurance companies tell us the order of most likely to least likely to be struck: sailing trimarans, sailing catamarans, monohaul sailboats, power boats. It all seems to come down to how much water (and i am talking salt water) you cover. While properly connected metals are important for corrosion resistance, grounding a mast properly will not save your boat in a direct strike for several reasons: First off, as mentioned in other replies, it is extremly difficult to do. Second, the amount of power can easily overcome any grounding system, third, the emp is going to wipe sensitive things out anyway. Long and short of it is you wither need insurance or a boat with no electronics, which, btw, is what we had when we first started sailing…

The choice ground or no ground. Controlled invited strike or uninvited catastrophic strike due to arc jumping. I would like for people that have experienced strikes to specify if they had lightning protection or not to compare results. Let me confuse the reader even more: in the pouring rain the lightning can travel around lightning protection from the mast down wetted surfaces to the vessels water line. That may explain water line damage. During a storm I hoist a thawed Turkey and an old two way radio to the mast head, some say it satisfies Thor.

I witnessed my own boat being struck with lightning while moored in front of my home. 34′ sailboat in fresh water, without grounding, keel stepped mast, external lead fin keel epoxy coated. I was standing at the window watching the storm pass when BOOM and I saw a cascade of white hot sparks from the masthead as the windex and VHF areal were vaporized. Waited for the storm to pass and rowed out to inspect the damage and found nothing! Electronics worked, even the radio fired up but obviously would not transmit or receive. Hauled the boat later in the week and found about one hundred little “craters” on the bottom that were the exit points of the strike. The craters only were as deep as the gelcoat and part way in to the mat skin coat. Ground them all out and filled, faired, and painted them. All good after replacing the windex and VHF… Lucky I guess…

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Modern Lightning Protection On Recreational Watercraft

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While you can't prevent a strike, there's a lot you can do to mitigate — or even prevent — damage.

A thunderstorm passing over a marina has the potential to cause expensive damage.

The recent advances in electrical and electronic systems have revolutionized recreational boating. Vessel operations have been simplified and the boating experience enhanced due to the integration of electronics into almost every onboard system, from navigation and communications to propulsion and maneuvering. Complex engine electronics known by various names including Engine Control Unit (ECU) and Engine Control Module (ECM) have increased performance and reduced emissions on modern engines. However, these advances have come at a cost. Many 21st-century boaters depend on electronic systems to navigate and maneuver their boats, and many modern engines will not function if their electronics are compromised. That makes modern mariners and their boats vulnerable to a lightning strike that damages these now mission-critical systems, potentially leaving the boat dead in the water without navigation or communications equipment.

Unfortunately, sensitive electronics on boats have become increasingly vulnerable to lightning strikes, yet lightning-protection systems have not kept pace. It's not that there haven't been significant advances in lightning science since Benjamin Franklin developed his theories on how to protect barns and livestock. The National Fire Protection Association, Underwriters Laboratories, and industries which are significantly at risk from lightning, such as telecommunications, wind generation, aviation, and fuel, have achieved consensus on the science of lightning protection and have embraced new protocols and practices. But the recreational boating industry has been slow to adapt those changes to the marine environment. There are at least three reasons for that.

There is no evidence from independent laboratories that these fuzzy lightning dissipators prevent strikes.

First, corrosion and motion on board boats, as well as limitations with respect to weight, space, and geometry, make lightning protection more challenging than in shoreside installations. Second, the mandate of the standards body for the industry, the American Boat & Yacht Council (ABYC), focuses on protecting life; protecting equipment has been a lower priority. Third, there has been strong disagreement between professionals about the best way to mitigate damage in a lightning strike and precious little data to support one point of view over another. The sometimes-raucous debate surrounding certain unproven lightning- protection devices and such theories as "fuzzy" lightning dissipation terminals and early-streamer emission terminals, as well as unorthodox placement of grounding terminals (a.k.a. grounding plates), have sharply divided the recreational boating technical community, all of which makes consensus on lightning protection difficult, if not impossible.

This lack of guidance is frustrating for those with boats at risk. While a runabout in Portland, Oregon, or a daysailer in Portland, Maine, may have little risk of lightning damage (see " Striking Lightning Facts "), larger vessels (particularly sailboats) in such lightning-prone areas as the Chesapeake Bay or Florida absolutely should be protected using the best technology available. Any marine-insurance adjuster can attest that the potential for loss on these vessels can be great. The National Fire Protection Association made some fundamental changes to the watercraft chapter of NFPA 780: Standard for the Installation of Lightning Protection Systems in 2008 that incorporate the thinking that has become accepted in other industries. While the recommendations in NFPA 780 have yet to be embraced by the recreational boating industry as a whole, understanding what it says — and why — may assist you in developing a lightning-protection plan for your boat.

Lightning 101

The simplest way to think of a lightning strike would be as a short circuit between the cloud and the earth. The earth and an active thundercloud have either a positive or a negative polarity with respect to each other, just like battery connections that can arc if they are not separated by a long enough air gap. Whether the positive charge is in the cloud or on the water may have great importance to a physicist, but matters little to the cow in the barn or the VHF radio antenna on the mast.

The important point is that the earth (or in our case, the water) contains an unlimited supply of positive and negative charges; it is the thundercloud that induces the charge concentration in the water. For example, if a large concentration of negative charge coalesces in a storm cloud over the ocean, a large concentration of positive charge is drawn to the very top surface of the water directly beneath it. (Opposites attract.) Since air is a good insulator, no electricity will flow between the cloud and the water unless the airborne charge loses altitude, moves close enough to the surface of the water, and the lightning jumps the gap. If an electrically conductive material, such as an aluminum tuna tower or mast, stainless steel rigging, or a long vertical copper wire, comes between the cloud and the water, then the gap that must be jumped becomes shorter. The boat short circuits the voltage, much like a wrench across battery terminals.

Because boats are built from electrically conductive components installed between the water and the areas aloft (masts, rigging, antennas, towers, support structures, electrical wiring), a lightning strike is inevitable if an active thundercloud containing electrical charges passes overhead at a low enough altitude. How much damage the lightning strike does to the boat depends upon how easily the electrical energy from the strike can find its way through the boat to ground. There will be a lot less damage if the discharge is contained in a well-designed lightning-protection system than if it takes a detour through the ship's wiring and sensitive electronics on its way out of the boat.

This is a basic concept that surprises many boaters: A lightning-protection system is not designed to prevent a lightning strike, but rather to provide a safe discharge path for the lightning. This is the only viable solution for lightning protection (short of going back to wooden ships, kerosene lamps, and sextants). The technology to prevent lightning strikes does not yet exist.

Still, there are devices out there claiming to do just that. Lightning dissipaters (LDs) look like metal bottle brushes or frayed paint brushes and are installed on the top of the mast. The hypothesis is that the numerous conductive points on the LDs safely dissipate accumulated charges so the lightning strike will not occur. As far as I am aware, not a single independent testing laboratory has confirmed the effectiveness of lightning dissipaters as lightning preventers.

Early-streamer emission (ESE) terminals have also gained traction in some circles. Fancy lightning rods often shaped like a torpedo that usually come with electronic circuitry, these are supposed to attract lightning better than a standard lightning rod (also called an air terminal), to ensure that the lightning strikes the grounding path rather than what is being protected. Once again, I am not aware of any independent studies validating the effectiveness of these devices.

Lightning-protection systems actually function by acting as the "best" short circuit between the cloud and the water, one designed to lead the lightning harmlessly to ground. The system accomplishes this in two ways: by attracting lightning away from more destructive pathways between cloud and ground, and by sending the charge around, instead of through, what it is protecting.

The first concept has traditionally been known as the "cone of protection" or the area protected by an air terminal from a strike. Traditionally, the cone of protection has been thought to include a circle centered on the base of the air terminal whose radius equals the height of the terminal and to extend from the top of the air terminal to the ground at a 45 degree angle. In fact, the length of the final jump that lightning takes before striking the air terminal is about 30 meters. Recent research suggests that the actual area protected can be defined by an imaginary sphere with this radius that is "rolled" up to the air terminal. All objects inside the imaginary sphere will not be protected by the air terminal, which means the area protected often differs in size and shape from the cone of protection model. Modern lightning protection for airports and power plants use the rolling sphere method and place air terminals so that the areas of protection overlap and include any sensitive equipment that would be damaged by a strike.

The second concept will be familiar to many as the Faraday cage. As early as 1836, Michael Faraday discovered that objects surrounded by metal were protected from lightning (explaining why we are safe from lightning while in our cars). Many old-school sailors have used Faraday's discovery to good purpose when they placed sensitive electronics in the oven during a lightning storm (with the oven off, of course.) This practice can be significantly updated by placing sensitive electronics in the microwave oven!

21st Century Lightning Protection

Benjamin Franklin pioneered lightning protection in 1749 with the invention of the lightning rod, and, when it comes to recreational boats, until recently, little has changed. Under his model, the lightning is attracted to the lightning rod (air terminal), which then passes the lightning current harmlessly to a submerged metaevent secondary flashes from these metal structures.

Air Terminals are shown in green; grounding plates with down, side flash, and equalization conductors in yellow; loop conductors in red; and catenary conductors in blue.

NFPA 780 draws much from the old-school system while incorporating improvements based on the modern understanding of lighting protection. While solutions will vary depending on the boat, let's talk about the basics.

Air terminals (lightning rod or Franklin rod) should be installed at the highest points of masts, towers, etc. On a sailboat a single air terminal could be bolted to the mast; on a sportfish it could be bolted to the tower and made to look like an antenna. This should be higher than anything you are trying to protect from a lightning strike, such as a VHF antenna.

A heavy electrical conductor should be connected from each air terminal directly down to a grounding point on the hull. In the case of a sailboat's mast, aluminum is a good conductor, so no separate wiring run needs to be installed. (Note that the wiring inside of the mast will be protected due to the Faraday effect.) An aluminum tower will work the same way on a sportfish so long as the legs are connected to an adequate grounding plate. Where no aluminum structure exists to act as a down conductor, a 4 AWG wire or larger should be run from the air terminal to the grounding plate in as straight a run as possible and well separated from other wiring.

The grounding point should be a corrosion-resistant metal plate installed on the exterior of the hull below the waterline. The plate should be at least one square foot in size and at least 3/16 of an inch thick. Research shows that most of the electrical discharge occurs along the edges, so a long, narrow plate, especially one with grooves cut in it, will be most effective at dispersing the charge. A new major point of contention is where to install the grounding plate, or plates. Some research indicates that a location at or near the waterline is by far the most effective solution. On a sailboat, the lead keel can be used as the grounding plate if the keel is not fiberglass-encapsulated or covered in fairing. If the mast is solidly keel stepped, there would be no need for a separate conductor from the mast to the keel. Metal rudders or propeller struts are also acceptable as grounding plates.

Protecting Electronics

Surge-protective devices (SPD) or transient voltage surge suppressors (TVSS) should be installed on all equipment that's mission critical, expensive, difficult to replace, and/or prone to lightning damage. Examples include the ECU/ECM, alarm systems, chartplotters, and instruments.

A bank of TVSSs protecting sensitive electronics.

TVSSs are the most exciting development in the field of lightning protection. These semiconductor devices provide protection by suppressing lightning-related voltage spikes. They are widely used in the telecommunications, wind generation, and avionics industries.

TVSSs are connected across the input terminals supplying voltage to a piece of equipment; they can be thought of as fuses that react to voltage instead of current. The TVSS is an open circuit as long as the supply voltage feeding the equipment is in the normal range. However, if a lightning strike causes a momentary voltage spike and puts, say 1,000 volts on a 120-volt device, the TVSS will "clamp" or short circuit 880 volts and convert it to heat. The excessive heat could, and probably would, damage the TVSS; but destroying a $250 surge arrestor to protect a $5,000 engine controller is good engineering.

Grounding plates should be long and narrow with groves cut into them to disperse the charge more efficiently.

Voltage surge protection would be prudent for engine controls, navigation systems, steering systems, and shorepower systems. TVSSs come in many voltage ratings, energy ratings, response times, and so on. Some are designed to protect whole distribution systems, while others are suitable for individual equipment protection only. A well-designed system includes cascaded protection, with extra protection on mission-critical and lightning-prone equipment, such as main engines and shorepower systems. The key to a reliable and cost-effective system is to ensure that appropriately rated devices are specified and properly installed. The best TVSS in the world will be ineffective if it is not connected properly.

Despite the best technology, there can still be challenges with an NFPA 780-based system, particularly when the system is improperly or only partially installed. For example, if the air terminal is installed lower than an adjacent antenna, it will not protect the antenna; in that case, the antenna cable carries the lightning current. Also, if the down conductor is connected to the bonding system rather than directly to a dedicated grounding terminal (ground plate), the lightning strike can energize the entire bonding system before discharging into the water. Another common mistake is to secure the lightning down conductor to other wiring. The high current from a strike through the down conductor can result in voltage surges in these adjacent wires, leading to additional damage in equipment that would otherwise be completely unaffected by the lightning strike.

In Conclusion

The recent revolution in marine electronics demands an evolution of our thinking on marine lightning-protection; equipment protection should be an important aspect of any modern lightning protection system. The knowledge and resources to safely transform this change in thinking into reality are readily available, both from the NFPA and industries also at risk from lightning. However, there are unique challenges on pleasure craft that are not addressed by others. These must be solved by sharing the experiences of lightning-protection systems and their effectiveness across the industry.

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James Coté

Contributor, BoatUS Magazine

James Coté is an electrical engineer, ABYC Master Technician, Fire Investigator and Marine Investigator. He operates a marine electric and corrosion control consulting firm located in Florida. For more information, go to: cotemarine.net

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Yacht lightning strikes: Why they cause so much damage and how to protect against them

• August 27, 2020

A lightning strike may sound vanishingly unlikely, but their incidence is increasing, and a hit can cause severe damage costing thousands of pounds, as well as putting an end to a sailing season, writes Suzy Carmody

Lightning strikes of boats are still fairly rare – but are on the increase. Photo: Image Reality / Alamy

Pantaenius handles more than 200 cases of lightning damage every year. “Over the past 15 years, the total number of such loss events has tripled in our statistics. The relative share of lightning damage in the total amount of losses recorded by us each year is already 10% or more in some cruising areas such as the Med, parts of the Pacific or the Caribbean,” added Pantaenius’s Jonas Ball.

Both UK and US-based insurers also report that multihulls are two to three times more likely to be struck by lightning than monohulls, due to the increased surface area and the lack of a keel causing difficulties with adequate grounding. Besides increased likelihood of being hit, the cost of a strike has also risen enormously as yachts carry more networked electronic devices and systems.

The CAPE index measures atmospheric instability and can be overlaid on windy.com forecasts

Avoiding lightning strikes

The only really preventative measure to avoid lightning is to stay away from lightning prone areas. Global maps of lightning flash rates based on data provided by NASA are useful to indicate areas of more intense lightning activity. They show that lightning is much more common in the tropics and highlight hotspots such as Florida, Cuba and Colombia in the Caribbean, tropical West Africa, and Malaysia and Singapore in south-east Asia.

Unfortunately, many of the most popular cruising grounds are located in tropical waters. Carefully monitoring the weather and being flexible to changing plans is an essential part of daily passage planning during the lightning season in high-risk areas. CAPE (Convective Available Potential Energy) is a useful tool for indicating atmospheric instability: you can check the CAPE index on windy.com (see above) as part of your lightning protection plan.

Protection against lightning strikes

Yachts that had no protection when lightning struck often experience extensive damage. The skipper of S/V Sassafras , a 1964 carvel schooner, reports: “Most of the electronics were toast. Any shielded wiring or items capable of capacitance took the most damage: isolation transformer; SSB tuner; autopilot and N2K network Cat 5 cables.”

Article continues below…

What is a Spanish Plume? Thunderstorms, lightning and downdrafts explained

Earlier this summer we saw considerable thunderstorm activity over the UK and Europe, resulting in flooding and some serious injuries.…

Expert sailing advice: How to handle a lightning strike on board

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The owner of Matador of Hamble , a Rival 41, recalls the effects of their strike: “The extent of the damage was not immediately obvious. For days afterwards anything with a semi-conductor went bang when we turned it on.”

The crew of Madeleine , a Catana 42S catamaran, had a similar experience. “We were struck in Tobago but only discovered the electrical damage to the port engine when we reached St Lucia and it was in the Azores that we found out the rudder post was broken and we had lost half our rudder.”

It therefore seems prudent that in lightning prone areas a protection system should be implemented where possible to protect the boat, equipment and crew. As a first step analysing the boat and the relative position of all the main metallic fittings can often reveal a few safe places to hide and places to avoid. Areas such as the base of the mast, below the steering pedestal and near the engine have the highest risk of injury.

Stays on a steel boat are attached directly to the steel hull. Photo: Wietze van der Laan / Janneke Kuysters

In terms of minimising the effect of a strike, one temporary method to limit the damage is to direct the current outside the boat using heavy electrical cables attached to the stainless steel rigging. With the other end of the cable immersed in the ocean, this provides a conductive path from the masthead to the ground.

The main flaw in this plan is that an aluminium mast has much greater electrical conductivity than stainless steel and is a more likely pathway to the ground. This system also requires adequate copper to be in contact with the seawater to discharge the current.

Other temporary measures include disconnecting radar and radio aerial cables, putting portable electronic items in the oven or microwave as a Faraday cage, turning off all the batteries or nonessential electronic equipment if at sea, or in a marina unplugging the shore power cord. All these procedures rely on someone being on board with several minutes warning before a strike to drop the cables over the side and turn off/disconnect and unplug.

Cable used as a down conductor from the shrouds on a catamaran. Photo: Wietze van der Laan / Janneke Kuysters

Posting an ‘Emergency Lightning Procedures’ card in a central location of the boat showing where to stand and what quick preparations to take is a simple first step.

Permanent lightning strike protection

In a thunderstorm, molecular movement causes a massive build up of potential energy. Once the voltage difference overcomes the resistance of the airspace in between, invisible ‘channels’ form between the base of the clouds and tall objects like masts, providing a path for a lightning strike to discharge some of the accumulated electrical energy. There will be less damage to a vessel if the discharge is contained in a well-designed lightning-protection system.

Lightning rods or air terminals installed at the top of the mast connected to an external grounding plate on the hull, via an aluminium mast, provide a permanent low impedance path for the current to enter the water. On boats with timber or carbon masts a heavy electrical cable can be used as a down conductor.

If not installed during production, a grounding plate can be retrofitted during a haul out. On monohulls a single plate near the base of the mast is adequate. A ketch, yawl or schooner requires a vertical path for each mast and a long strip under the hull between the masts, whereas catamarans usually require two grounding plates to complete the path to the water.

The current from a lightning strike is dissipated primarily from the edges of the plate, so the longer the outline the better. Warwick Tompkins installed a lightning protection system designed by Malcolm Morgan Marine in California on his Wylie 38 Flashgirl :  “Two heavy copper cables run from the foot of the mast to the aluminium mast step, which was connected to a copper grounding plate on the outside of the hull via ½in diameter bronze bolts.”

The grounding plate was an eight pointed star shape. “Some liken it to a spider.” Warwick says, “And the very minimal electrical damage we experienced when struck was directly attributable to this spider setup.”

A copper ‘X’ grounding plate, used on boats that have a fin keel some distance aft of the mast. Photo: Malcolm Morgan Marine

Morgan adds: “Any cables associated with lightning protection should be routed away from other ship’s wiring wherever possible. For example, if the navstation electronics and main switchboards are on one side of the vessel, the lightning protection cables should be routed on the opposite side.”

An internal bonding circuit connects the major metal objects on a boat to the grounding plate via bonding cables. This can help prevent internal side strikes where the current jumps between objects in order to reach ground.

Morgan explains: “As modern boats are becoming increasingly complex careful consideration is required to ensure the bonding system is designed correctly. There are five possible grounding systems on a vessel (lightning protection, SSB radio ground plate, bonding for corrosion, AC safety ground, and DC negative) and all need to be joined at one common point and connected to the external grounding plate.”

This strike exited through the keel, blowing off the fairing and bottom paint. Photo: GEICO / BoatUS Marine Insurance

Surge protection

Yachts anchored close to shore or on shore power in a marina are susceptible to voltage surges during a thunderstorm. If lightning strikes a utility pole the current travels down the electricity cable looking for ground. It can enter a vessel through the shore power line or can pass through the water and flashover to a yacht at anchor.

Surge-protective devices (SPD) are self-sacrificial devices that ‘shunt’ the voltage to ground. They reduce the voltage spikes eg a 20,000V surge can be diminished to 6,000V but the additional current can still be enough to damage sensitive electronics. Therefore fitting ‘cascaded’ surge protection with several SPDs in line on critical equipment is a good idea.

High-tech solutions

Theoretically, if a lightning dissipator bleeds off an electrical charge on the rigging at the same rate as it builds up it can reduce or prevent a lightning strike. Lightning dissipators such as ‘bottle brushes’ are occasionally seen on cruising boats, though these are relatively old technology. Modern dissipators feature a 3⁄8in radius ball tip at the end of a tapered section of a copper or aluminium rod. The jury is out on their effectiveness.

A more high-tech solution is Sertec’s CMCE system, which claims to reduce the probability of a lightning strike by 99% within the protected area. The system has been widely installed on airports, stadiums, hospitals and similar, but has now been adapted for small marine use (and may reduce your insurance excess).

Arne Gründel of Sertec explains: “The CMCE system prevents a lightning strike by attracting and grounding excess negative charges from the atmosphere within the cover radius of the device. This prevents the formation of ‘streamers’, and without streamers there is no lightning strike.”

A Sertec CMCE marine unit, designed to dissipate lightning

• 1. Avoiding lightning strikes
• 2. ‘A lightning strike caused £95,000 of damage to my yacht’

An approach to a modern sailboat lightning protection system

We were lucky when we were struck by lightning on our small 35’ GRP cruising sailing boat in Turkey in 2013, but without an LPS. All the plastic and some of the metal gear at the top of the mast exploded (see photo below) and simultaneously the headlining in the saloon exploded downwards with a loud bang. So much smoke that we initially thought we were on fire; but my wife and I survived unscathed to tell the tale.

The most likely discharge exit was through the propeller shaft, but practically all electronics were violently destroyed and, as an electrical and electronic engineer, my assessment for our insurance claim afterwards showed that most devices had experienced severe arcing with small electronic components having exploded internally (see photo below).

An lightning protection system is a bonding, grounding and shielding arrangement made of four distinct parts: Air terminals, down conductors, a low-impedance ground system and sideflash protection.

The best lightning protection system cannot guarantee personal protection, or protection from damage to sensitive electronic equipment. Also it is not a lightning prevention system. I knew the private owner of one large blue water catamaran which has been struck three times in its life and it is not an old boat. Fortunately no one was hurt on any occasion, but many electronic systems on that complex boat were effected and had to be replaced on each occasion. Unfortunately catamarans are many times more likely to be struck than mono-hulls and records in the USA, where certain locations are particularly prone to electrical storms (e.g. Florida where boat ownership is high), show that mono-hull sailing boats are about 25 times more likely to be struck than motoryachts.

Lightning is very hard to study and to accurately predict its behaviour is almost impossible, but it is driven by the simple fact that a massive potential difference (voltage) exists between the highly charged clouds of a brewing thunderstorm and the surface of the Mother Earth. Eventually, a path is found through the atmosphere down to ground for some of the accumulated charge to discharge and the creation of a discharge path first requires the creation of so called ‘streamers’ [1],[2]. Bear in mind that air breaks down at 3 million Volts per metre, and you get some inkling of the enormous voltage differences involved.

In the middle of a large body of water, with your sailing yacht in it, the top of the mast, being the highest point around, looks like a handy point to discharge through. So the LPS is designed to control the first point of discharge and then make the onward path to ‘ground’ – in this case the sea – as direct as possible and capable of conducting very high currents for a very short time during the discharge.

In 2006, the American Boat and Yacht Council (ABYC) technical information report TE-4 [3], [4] recommended the following:-

• lightning protection system conductors must be straight and direct and capable of handling high currents. The main ‘down’ conductor is recommended to be 4AWG, or 25mm2 in European sizing; see diagram.

• A large enough area ground must be provided between the vessel and the water to offer an adequately low resistance path (ABYC recommends 1sq.ft. {0.1m2} in salt water; much larger in fresh water. NB this is not adequate for acting as the SSB counterpoise). Metal-hulled vessels naturally offer a large ground contact area with the sea, but the connection between the hull and all other electrical systems needs careful consideration.

• Heavy metal objects such as fuel tanks and engines must be bonded to the ground bonding arrangement to reduce the risk of ‘side flashing’ where the lightning literally can jump from one conductor to another, seemingly better path. Similarly, it can jump out of corners in cabling, so if bends must be made, then they should not be more than 90° and with as large a bend radius as possible.

The basic arrangement is as depicted in the diagram, where the ‘air terminal’ is a rounded end (circled in photo) metal wand mounted at the top of the mast to ‘attract’ lightning to it and, most importantly, to stand at least 6” (15cm) higher than anything else e.g. above the VHF or other antenna. Providing the air terminal is securely electrically bonded, presenting a high surface contact area, low resistance path to an aluminium mast, the mast itself can be used as the down conductor at least to the deck or keel, depending on where the mast is stepped. In the case of wooden, or carbon composite masts they present too high electrical resistance and a 4AWG cable must be run straight down the mast as the main down conductor. From the bottom of the aluminium mast or down conductor, the 4AWG onward path needs to be as direct and short as possible to the ground plate, or the metal hull.

It is actually better to leave through-hull metal fittings electrically isolated if they are already insulated from the rest of the boat by dint of their attached rubber or plastic hoses and their insulating mounting plates – decent quality bronze alloy seacocks and engine intake strainers will not unduly corrode if left submerged for extended periods of time without needing connecting to the vessel’s earth bonding. However, in the US it is more normal to bond everything metal below the waterline, use a tinned copper bus bar running the necessary length of the vessel, above any bilge water level, to connect each through-hull fitting to, which is then connected at one point only to the main grounding route out of the boat. This bonding arrangement is gaining in popularity outside the US with consideration of a lightning protection system.

Note in the diagram that all tie-ins, including fore- and back-stay (unless insulated) must use at least 6AWG (16mm2 European) cable. All large metal objects within 6ft (2m) of the lightning down path also need tying in with 6AWG (16mm2) cable. Examples are metal fuel tanks, main engines (despite them usually already being connected to the water via their prop shaft) and generators; this is to minimize the risk of ‘side flashing’ where lighting can literally jump from conductor to metal object, looking for a better path to ground, even if one does not exist.

In considering of the creation of a ground plate of sufficient size, a metal hulled vessel is ideal, but nevertheless only one electrical connection point to the hull should be made from the main 4AWG down conductor. This same point should have all the other earth bonding made to it alone. The DC main negative bus in turn should be connected to the earth bonding in only one place, though European boats generally have their DC system isolated from any bonding system to discourage DC earth faults, the US differs in this respect, preferring direct bonding. One solution to this dilemma is to use a suitably rated surge capacitor between the DC negative busbars and the bonding system for the LPS. In the case of a non-metal hulled sailing vessel, the attraction of using the keel as a discharge point should be resisted as it is in contact with the water some distance below the surface where already a lot is going on with respect to charge balancing, so an alternative point is likely to be sought out by the discharge, nearer the surface. It seemed clear to our very experienced (and ancient) marine insurance surveyor that, during our own strike in Turkey, the discharge was out through the propeller shaft.

So far, so good, but recent thinking and good practice [5],[6] has modified the above ideas to take into consideration the danger of side flashing much more. A side flash is an uncontrolled spark that carries current to the water and can do extensive damage to hulls and equipment. The good practice and standards for a lightning protection system relating to marine situations, such as they exist (see NFPA 780, latest version, especially chapter 8, ‘Protection for Watercraft’, [7]) are tending to treat a boat more and more like a building to exploit those well tried and tested techniques used in a land based situation. Rather than a ‘cone’ below the air terminal, the ‘zone of protection’ is now more reliably envisaged to be formed from a ‘rolling sphere’ of 30m radius, as shown below for a larger yacht [7],[8]:-

Diagram of Boat with Masts in Excess of 15 m (50 ft) Above the Water; Protection Based on Lightning Strike Distance of 30 m (100 ft).

With a large building, the down conductors from the various air terminals run down the outside of the building to a number of grounding stakes; not so with a yacht where, as we have described, we’ve now concentrated the discharge right in the middle of the boat, where the danger of side flashing into other metal parts is very real; if these parts are not bonded and protected by a properly designed, low impedance path there’s are very real further danger of the side flash finding its way onwards and out through the side of the boat to the surrounding water surface. This has indeed been experienced by an American friend of mine on a high-tech, all carbon racing sailing boat on its way back to Newport, which after being unavoidably struck several times in a violent storm, put in to New York and immediately hauled to find literally a thousand or more tiny holes around the waterline when the discharge had exited! Apparently lightning does not always take the straightest path to the water, but rather has an affinity for the waterline.

The latest version of this NFPA 780 standard recognises this danger and, in a departure from the older versions, provides for multiple grounding terminals to provide the shortest path to the surrounding water surface. These ‘supplemental grounding electrodes’ conduct lightning current into the water in addition to that conducted by a main ground plate. The new standard provides for a continuous conducting loop outboard of crewed areas, wiring and electronics. Placing the loop conductor well above the waterline, outboard, and with grounding terminals below it retains the advantages of an equalization bus, whilst correcting for its weakness with side flashes having nowhere else otherwise to go.

Protection of electronic equipment by a hermetic system on larger yachts

So much electronic equipment on board a yacht struck by lightning is very susceptible to permanent damage. The only safe way to fully protect electronic equipment is to have it completely disconnected from all other circuits when thunder and lightning are nearby, and I still to this day do that as much as possible, but how practical is complete protection really?

A recent idea I had whilst discussing the problem with a 30m ketch owner may have some merit, and I call it a ‘hermetic system’, so suggesting that it is sealed from the outside world: If the most critical and/or sensitive electronic equipment can be enclosed within its own quite separate power and cabling set, separate from the rest of the boat’s electrical and electronic wiring, then it is possible that it could be saved in the event of a lightning strike. One way to do this would be to run all those systems required to be protected effectively off an Uninterruptable Power Supply (UPS), powered from the AC bus (via the generator), then down converted to the necessary 24/12VDC electronics supply. In the event of a lightning storm, all AC connections to the UPS and any signals, power or ground returns outside the hermetic system must be open circuited by large clearance contactors. The electronics contained within the hermetic system can still continue to operate, for a limited time (depending on the capacity of the UPS batteries) and further choices can be made about what to shut down within the hermetic system to extend the battery life, leaving for example just the absolute minimum electronics to continue to safely navigate e.g. Depth, GPS, Chartplotter. Very careful consideration must be given to cable runs.

The VHF antenna on the main mast may be protected by a surge arrestor from one of several suppliers e.g. www.nexteklightning.com. No guarantee is likely to the effectiveness of this as a protection device in all cases of lightning strike and the manufacturers should be consulted for further information.

I certainly now resort to the marvel of a GPS chart plotter on my mobile phone when there’s a nasty electrical storm about and I’m out at sea! References: –

1. Top 10 best lightning strikes (USA) by Pecos Hank, with rare photo of an upward streamer. 2. http://marinelightning.com/index_files/SFMechanism.gif for a graphic showing the formation of negative streamers 3. ABYC (US) technical report TP-4 “Lightning Protection”. 4. Nigel Calder – “Boatowner’s Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat’s Essential Systems” 5. “Complexities of Marine Lightning Protection”, By Ron Brewer, EMC/ESD Consultant, April 2011 6. “A New Concept for Lightning Protection of Boats – Protect a Boat like a Building” Ewen M. Thomson, Ph.D.; published in the October 2007 edition of Exchange 7. National Fire Protection Association (US) document NFPA 780-2014 “Standard for the Installation of Lightning Protection Systems” – see especially chapter 8 ‘Protection for Water craft’. 8. “Evaluation of Rolling Sphere Method Using Leader Potential Concept – A Case Study” P.Y. Okyere, Ph.D & *George Eduful – Proceedings of The 2006 IJME – INTERTECH Conference

Feature article written by Andy Ridyard. Andy Ridyard has been a professional electrical and electronics engineer for more than 35 years and started SeaSystems in 2008. His business is dedicated to providing troubleshooting, repair and installation services to superyachts internationally, specialising in controls and instrumentation. He lives with his wife in Falmouth, UK, but works mostly in the Mediterranean. SeaSystems has fixed countless intractable problems with marine control systems, marine electronics, Programmable Logic Controllers (PLCs) and marine electrical systems. For more information visit SeaSystems.biz .

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How to Protect Your Boat From Lightning

Of all the dangers you can face at sea, lightning is one that almost no boater considers. Lightning is not a threat in the eyes of most people. It’s considered rare and unusual. You need to get that thought out of your head as a boat owner. Lightning strikes are far more common than you might think.

They key to staying safe from lightning at sea is preparation. You need to use a little help gleaned from 19th century scientist Michael Faraday. He can keep you safe from the total destruction of your electrical systems and a potential fire.

How Common Are Lightning Strikes on Boats?

According to the insurance provider BoatUS , the statistics are very unexpected. Around one in 1000 boats get hit by lightning every year. If there are about 12 million registered boats in America. Knowing that allows the numbers to become a little more clear. That’s 12,000 boats every year getting hit by lightning. One in 1,000 odds are not very high at all.

It should come as no surprise that taller boats are more at risk. This is for the same reason you see lightning rods on tall buildings. Lightning wants to get to the ground as fast as it can. It is attracted to conductive materials. The closer those materials are to the source of lightning, the more at risk they are. So anything tall and metal is at the greatest risk. The top of the mast on a sailboat is, in effect, a lightning rod at sea. If a sailboat and a jon boat are side by side on the water, the lightning will hit the sailboat every single time.

Likewise, the bigger the target, the more likely lightning is to hit it. Swap out the sailboat in our example with a yacht. The jon boat is still much safer. Bigger boats have more conductive materials on them. They have their own electrical equipment, which creates an electrical field. More metal parts will attract lightning. And simply having more area exposed makes it more attractive to a stray bolt from the sky.

It’s also worth noting that a multi-hulled boat is at greater risk as well. BoatUS stats show a multi-hulled boat is twice as likely to suffer lightning damage. On the upside, this doesn’t hold true for pontoon boats. In fact, they have statistically fewer instances of damage than other boats. So if you’re really worried about lightning, maybe give a pontoon boat a second glance.

• By the numbers, you want to have a bass boat, a pontoon boat , or a runabout. In 2012 and 13, insurance policy claims for lightning strikes on those boats were the lowest. They had a 0.1 chance in 1,000 of a direct lightning strike. That’s about as impressive as it can get.
• Averaged across all boats, the rate of lightning strikes was 0.9 in 1000. We’ve rounded that up to 1 in 1,000. Not trying to make things look worse than they are, but it’s just easier to say it that way. The point is mostly the same.
• A trawler or a motoryacht have a 1.5 in 1000 chance of being hit by lightning.
• A monohull sailboat will bump your odds of being struck significantly. At this point they are 3.8 out of 1000. More than double a trawler, nearly 4 times the average, and nearly 40 times what a bass boat is facing.
• A multihull sailboat has a 6.9 chance in 1,000 of being hit by lightning strikes. That’s about a 1 in 144 chance. You need a lighting protection system of some kind to avoid this. It won’t prevent lightning strikes, but it can prevent damage.

Why Are Multi-Hull Boats More at Risk?

Why is a multi-hull sailboat a danger when a pontoon boat is not? That’s a good question and there is not a good answer. As frustrating as that may be, not enough research has been done. So it’s not easy to explain why a multihull sailboat is so much more at risk than other boats. Since pontoon boats are actually below average, the reason is not immediately apparent. That doesn’t change the fact that statistics bear this out, however. If you have a multihull sailboat, it is at the greatest risk of lightning strikes. That means you’ll want to be a little more cautious than you otherwise would be.

How Does Boat Size Affect Lightning Strikes?

It’s not just the kind of boat you have that can attract lightning. As we said before, size is a factor. Smaller boats offer a smaller conductive path. They offer less chance for lightning to reach ground. Because of that, they are less likely to suffer a lightning strike.

If your boat is fifteen feet or less then you can rest a little easier. Statistically speaking, it’s not likely to be hit by lightning at all. It’s not impossible, but the numbers are not even charted, really. You have a 0 in 1,000 chance. That could mean you still have a 1 in 10,000 chance, so don’t think you’re fully immune.

At 16 feet to 25 feet your numbers increase. There’s a 0.2 in 1,000 chance of any boat at those sizes being struck.

There’s a significant increase above 26 feet. From there up to 39 feet your odds are 2.1 in 1,000. A boat of that size will have a lot more conductive material present. It’s also going to have more electronics on board and you need to worry about that. Lightning strikes and electronics do not mix at all.

Finally, a boat over 40 feet have a 6 in 1000 odds of being struck by lightning.

The mast of a sailboat is hands down the most attractive part of a boat for lightning. If your mast top goes from 35 feet to 45 feet, you just increased the odds of a strike threefold.

Where Is a Boat Most at Risk from Lightning?

Weather can be a very fickle thing. Depending on where you are in the country you may endure lightning storms all the time. Other spots almost never see electrical storms. So it stands to reason not every part of the country is as potentially dangerous as others.

The frequency of lightning flashes across the country follows a fairly reliable path. Nowhere is “safe” from lightning, but there are high concentrations and low concentrations. In fact, you can nearly bisect the country in a diagonal. The northwest United States suffers the least amount of lightning strikes. So up the Pacific Coast into Washington. This is where you will find the lowest frequency of lightning strikes.

You can draw an arrow from that point all the way down to the southeast tip of Florida. Southern Florida has the highest frequency of lightning strikes. Florida is the number one state for lightning damage to boats. Let’s take a look at the list for the top 7 claims locations.

• Mississippi
• South Carolina
• North Carolina

Only one state there isn’t down towards the south-east part of the state. Maryland comes in tied with Mississippi thanks to its high density of sailboats. Something to keep in mind. Even when something seems safe, it doesn’t necessarily mean that it is.

Claims for lightning damage along the Pacific Coast happen rarely. The frequency is around 1 in 10,000. Given how low that is, it should give you pause when you think of the Atlantic Coast. All of the numbers we’re presenting are averages. That means there are a lot of west coast boats that are never being struck. Therefore, there are more east coast boats getting struck by lightning to balance things out. Keep this in mind if you boat anywhere along the Atlantic.

The Pacific Ocean is colder. That means lightning occurs less frequently on that coast. The Atlantic Ocean is much more fertile ground for storms.

What Can a Lightning Strike Do to a Boat?

Now that you know the odds of a lightning strike, what next? How bad could a lightning strike be? Well, it can get pretty ugly. A mild lightning strike will render any fixed electronics useless. Radio , lighting, GPS , bilge pump , engines, you name it. Generators will likely be fried in most cases. It’s not unheard of for a DC solenoid to literally melt.

It’s possible your engine will still run after a lightning strike. But this is like a deer still running after it gets hit by a car. It can happen, but it’s not pretty. It also may not run for long. Expect frequent misfires if it’s still operational. Also, a lot of smoke. Your RPMs are going to drop significantly. Fire risk will greatly increase. The chances of it failing anytime thereafter are very high.

Other systems may continue to function but not in the intended way. We’ve heard of bow thrusters that will continue to run. The problem is you can’t turn them off and they may only run hard to port or starboard. Changing direction is no longer an option.

Suffice it to say lightning can utterly ruin your electronics. More than that, it can wreak havoc with your boat’s body. Most of the metal and writing in a boat is designed with a certain charge in mind. The average lightning bolt is 300,000 million volts and 30,000 amps. It has a negative charge and is DC current. Think of what kind of battery your boat runs on. Is it 12 volt? Maybe 24? No matter what it runs on, it’s not meant to handle lightning level power.

When lightning hits your boat, it’s going to follow the path of least resistance. Unfortunately, lightning can also make use of something called electromagnetic induction. That means if you have two wires near each other, the electrical charge can jump from one to another. Even if the second wire is not touching the first through which the current is flowing. Just being close enough to it allows the power to arc and continue on its path. Your boat is going to be small enough that the lightning is able to continue on a path. It will travel through wires and across metal fittings and fixtures.

Much of the wiring in your boat is likely to be melted completely by lightning. The power flow can actually blow a hole right through your hull. It’s also possible that it will burn the fiberglass around metal fittings. That can create holes and cracks and cause a boat to sink.

Boats on the water typically suffer less damage than those on trailers or stored out of water. On dry land, the electricity will follow a path down to whatever is holding the boat up. On some boats you can even see the scorched path and burn marks along the hull. In the water, the power dissipates more evenly. It will cause less destruction as it reaches ground. In this case, of course, ground is actually water. Lightning protection systems are therefore important in preventing this.

The Cost of Lightning Strikes

So what does all that damage do to a boat? More than 75% of all lightning strike claims are for less than 30% of the insured value. Of those damage claims, the vast majority of them are claiming electronics damage. That’s why, if you see a storm coming, it’s good to unplug those electronics that you can.

All of this being said, you need to keep things in perspective. You already know the odds on even getting hit by lightning in the first place. Suffering severe damage is still a rarity even when lightning strikes do occur. But the fact is it can happen, so you should be prepared. That’s where Michael Faraday and his Faraday Cage.

What is a Faraday Cage?

Michael Faraday created what is the basis for a modern lightning protection system. Lightning strikes can’t be prevented. They can be redirected, though. Faraday was convinced he could make a cage of conductive materials. The outside of the cage would redirect the electrical charge. This, in turn, would protect whatever was in the cage. You may have seen these before in YouTube videos.

The idea is to have this cage of conductive materials around a person or thing. All the metal is bonded together and carries the same electrical potential. Lightning follows the cage to the ground because it’s the path of least resistance. It’s like a bundle of lightning rods fused together. The electrical current can easily travel from the sky to the ground along it.

Obviously you’re not putting a literal cage around your boat to protect it from lightning. However, the same principles are used to protect your boat.

What’s the Best Lightning Protection System for a Boat?

In order to protect your boat from lightning strikes you need a way to redirect those strikes. Your cage is not a literal one but it does require certain conductive materials. You’ll need a marine electrician’s help here. They can put together the best protection system for your particular vessel.

In general, it works like this. Heavy conductors are used to create a cage by bonding all of your boat’s metal components. This starts at the top of the mast and must include all of the major components we have mentioned. Outriggers, railings, arches make a good framework. The AC compressor, engines, stove and other electronics need to be included as well.

A low resistance wire can connect all of these components and offer a path for the lightning to travel. The current will travel to ground, or in this case water, along the path. It can exit the boat through the propeller shaft or keel bolts. Ideally, though, you want a separate system in place. At least one square foot in diameter external ground plate is ideal. The electrical current can be routed to the ground plate and avoid damage to the rest of the boat.

Your engines should be bonded. This helps you avoid something called side flashes.

What is Thompson’s Lightning Protection System?

The National Fire Protection Association helped devise a system. Along with the American Boat and Yacht Council, they created this method. It was devised by Electrical engineer Ewan Thompson. He developed it as the best way to protect a boat from lightning.

• Start with lightning rods. A single rod protects in a cone of about 45-degrees. You want more than that, of course. Several lightning rods set up around a boat provide maximum lightning protection. Thompson found that the best lightning rod is a ½ inch in diameter with a rounded top. Located at the bow, the stern, and above the highest points can help create the basis of your cage.
• The rods need to be connected with heavy two-gauge wire. The wire needs to travel the easiest path to the water’s surface. If there are bends, they need to be long, sweeping ones. Remember, the current could potentially leap from one wire to another. This will happen if they are too close together. Run them outboard and keep them two feet away from any other wires. This is especially important if they are on parallel paths. Any closer and you risk electromagnetic induction. Then all your hard work will be for nothing.

If there is a point where your lighting wires cross normal wires, make it a right angle. Induction has the least chance of happening at right angles. It keeps the contact to the bare minimum.

• Rails and aluminum supports for a hardtop can become part of the cage. Bridge any gaps with wire, however. If the wire doesn’t connect gaps in rails, it can’t work.
• Create your Faraday Cage. You have the top of your cone of protection set up now. But to make it a cage you need one continuous band around the entire boat. This can be either one wire or a metal strap. It should be located below the level of the deck but above the waterline. Some manufacturers of boats include these bands right in the hull. Just above the waterline you’ll find a copper band around the entire boat. All the wires can be connected to it to dissipate any lightning strikes.
• Thompson’s method also includes the use of sparking electrodes. These small devices can be affixed around the boat above the waterline. They’re made from stainless steel or graphite and other fire-resistant materials. They allow the current to discharge into the water. When lightning does strike, it will typically blow them out so they will need to be replaced. It’s recommended they be placed most frequently near the bow. That’s where the majority of lightning strikes seem to occur.
• To avoid that side flash on your engine, you need to run more two gauge wire. Connect it to where the bonding system connects the engine. From there it can go to the electrodes. Also it can be connected to submerged grounding strips above and outboard of the prop. This is a better solution than letting the propeller take the electrical charge. You can also connect bow thrusters in this manner. When this is done properly, your thrusters and engines are all part of the cage as well.

Finally, use surge protectors. These are especially useful for your GPS and VHF radio . They can suppress voltage above 300 volts. As we’ve seen, that would be pretty important in a lightning strike. The result is knowing your expensive electronics can be protected.

How to Handle a Lightning Storm on a Boat

So, let’s say you have your boat all set up now. There’s a Faraday Cage, and you have your cone of protection. There’s a storm brewing and you can see lightning in the distance. Are you safe to wait it out? Maybe. But don’t risk it.

If you ever have the option, leave. Outrun a lightning storm whenever it is feasible to do so. Running for protection is always better than facing lightning in the open water. If that is not an option, then do your best to prepare. Make sure you pull in any fishing lines and bring in any swimmers if possible. Lightning can actually strike up to one mile ahead of a storm.

Turn off any electronics that you don’t need and stay low and centered in your boat.

What to Do If You Think Your Boat Was Hit?

Many lightning strikes are going to happen when you’re not there. Your boat will be in the marine while you’re at home. You’ll get to the boat and realize things aren’t working. The fridge is off, the radio is a no go, nothing that runs on power is turning on.

You have a few steps you should follow. These will allow you to give your vessel a thorough check after a suspected lighting strike.

• Turn off all of your battery switches
• Unplug shore power to prevent the possibility of a short circuit
• Check your bilge . If the bilge isn’t dry you may have an issue below the waterline and you’ll want to have the boat hauled out.
• You’ll need to call your insurance company once your boat is secure. If you know it’s not taking on water a haul out may not be necessary.
• Keep any damaged electronics or parts. The insurance company will want to assess them before they get tossed out.
• A marine surveyor can come and assess your boat. They’ll be able to determine what works and what has been destroyed. If the insurance company deems it necessary, they may pay for a haul out as well. That way everything below the waterline can be inspected.

The Bottom Line

Lightning damage is definitely a rare thing. But on the water it’s a lot more common than most boaters realize. It’s not the sort of thing you need to lose sleep over, but you should be prepared. Lightning protection systems are invaluable. You don’t want to be on the wrong end of a lightning strike one day. The saying “better safe than sorry” definitely applies here. If you have a sailboat, consider protection. Likewise if it’s a large boat, or one on the Atlantic coast anywhere. An ounce of prevention is worth a pound of cure.

My grandfather first took me fishing when I was too young to actually hold up a rod on my own. As an avid camper, hiker, and nature enthusiast I'm always looking for a new adventure.

Categories : Boats , nauticalknowhow

Paul on August 4, 2021

…”lightning hits your boat, it’s going to follow the path of least resistance. Unfortunately, lightning can also make use of something called electromagnetic induction. That means if you have two wires near each other, the electrical charge can jump from one to another. Even if the second wire is not touching the first through which the current is flowing. Just being close enough to it allows the power to arc and continue on its path.”…

The article is very informative but misses out some stuff & is possibly misleading in parts.

Arcing between wires is not electromagnetic induction. Electromagnetic induction is due to the fact that a lightning strike consists of repeated sharp rises & falls in large currents which produces an RF effect which creates rapidly changing magnetic fields which results in induced voltages in cables intersected by the changing magnetic fields.

One of the basic methods of protecting electrical & electronic equipment is to have twisted pair cables, mu metal cable shielding, arranging for most cable runs to be as horizontal as possible with all vertical runs in one place In heavy magnetic shielding conduits and ensuring that lightning current is always as vertical as possible. All mast cables should be connected by easy to reach & disconnect plug & sockets that can quickly be unplugged if needed.

Ben on August 23, 2021

What about galvanic considerations?

Chuck Dickey on September 2, 2021

So should you unplug shore power before a lightning storm?

Jeffrey M Streib on February 13, 2023

What effect might a lightning strike have on:

-The batteries and their capacity -Speakers

I suffered a lightning strike and lost almost all electronic components, engine components, gps, vhf steer by wire etc.

The insurance company has been good overall, but the surveyor doesn’t think the (3) batteries speakers, and bilges were related to the strike. (They all worked fine prior)

Any help would be appreciated.

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How to Prepare for Lightning Strikes

• By Ken Englert
• Updated: January 24, 2012

Lightning will always take the most direct conductive path to earth by striking the highest object in the area. Unfortunately, on the water, the highest and most attractive object to a lightning bolt just might be your boat. Be advised that when lightning strikes your boat or even near your boat, your electronics are vulnerable to damage. Here’s how to be prepared.

Create a Short Circuit There is no absolute protection against lightning aboard a boat. But there are steps you can take to avoid or minimize damage. The most likely targets are antennas, fishing rods, towers, T-tops or any elevated electrically conductive surface. You can’t prevent a lightning strike, but you can create a safe path for lightning to travel.

To conduct a strike safely to “ground” (on a boat this means to the water), create a low-resistance path from the highest point on your boat to a metal grounding plate in contact with the water. Start with a solid half-inch-diameter steel or bronze rod elevated six to 12 inches above every other object on the boat. The tip of that rod should be pointed, not blunt. Run a conductor made of at least a No. 8 gauge wire from the rod in as straight a path as possible to the water-grounding point.

The recommended water ground is a metal ground plate mounted outside of the hull. It can be copper, monel, naval bronze or other noncorrosive metal and should be solid, not the porous type used for radio antenna grounds, and be at least one square foot in area. Check with the manufacturer to see if this already exists. Also know that factory-installed lightning rods and grounding conductors are sometimes unwisely removed or disconnected by boat dealers or unknowing buyers.

Ground, Ground, Ground Ground all electronics and large metal objects on board, including metal cases or grounding studs on electronics and electrical equipment. Not to be overlooked are the engine(s), stove, sink, tanks, refrigerator, air-conditioner, metal railings, tower, arch and Bimini top. When running grounding conductors, don’t attempt to neatly bundle grounding cables together with the rest of the electrical wiring. Keep them separate from all other conductors, including antenna wires. Also, do not run the ground conductors in close proximity to or parallel to existing wire runs to prevent arcing.

More Detailed Lightning Protection Tips and Strategies

Storm Safety Tips – Lower all antennas and downriggers.

– Disconnect all power, antenna and interconnection cables to the electronics and electrical gear.

– Do not touch two metal surfaces at the same time (engine controls, a railing, helm, etc.) or you may become a convenient conducting path yourself.

– Do get out of the area and head for shore, and send the crew belowdecks.

Check out more tips on how to protect yourself and your boat during a lightning storm: 3 Crucial Tips to Avoid Lightning Strikes

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Lightning Protection for Boats, Sailboats and Yachts – No More Lightning Strikes on Boats

No more lightning strikes,

No more damage on boats,, no more equipment loss.

Boats are extremely prone to lightning because the mast of the boat is highly conductive and it is usually the highest structure around. Even if the mast is made of a non-conductive material, salty sea water makes it extremely conductive.

During a storm, all positive charges on water climb up on the boat mast and emit towards the storm cloud. This process develops the lightning channel between the cloud and the mast, and lightning current flows down to the water through the mast, and damage all equipment on the mast and on the boat.

Lightning rod on boat mast

Lightning rods are invented more than 300 years ago to protect non-conductive buildings from lightning strikes. Conductive structures such as boat masts cannot be protected by lightning rods because the lightning rod attracts lightning strikes on itself and naturally to the mast.

Lightning current prefers to flow down through mast surface instead of a tiny conductor cable, and this results with damage on the boat and equipment on the mast.

Once again, lightning rods are invented to protect ordinary buildings, not conductive structures such as boats .

Lightning must be kept away from boats.

EvoDis® Lightning Prevention System

EvoDis® System Marine Series is the only lightning protection solution which dissipates the charges on the mast and makes the boats, sailboats and yachts “ invisible ” to lightning. This process keeps the surrounding electric field lower than the threshold level and avoids the development of the lightning channel between the cloud and mast.

Lightning acts as if the boat does not exist there and all equipment remain safe.

EvoDis® Lightning Prevention System protects more than 1300 sites all over the world with 100% success for the past 11+ years.

Contact Us today to protect boats from lightning strikes forever.

Best way of lightning protection is to stay away from lightning.

EvoDis® keeps lightning away from your boat.

Marine Lightning Protection

• Introduction
• Sideflashes
• The lightning system
• Collaboration
• Air terminals
• Grounding concepts
• Grounding guide
• Design & build
• Connections
• Grounding Strips
• Siedarc TM Electrodes

Marine Lightning Protection Inc. Being at the forefront of both the basic science and product development in this area, we are uniquely qualified to address all of the problems inherent in lightning protection on the water. Whether for a fiberglass jet ski or a superyacht our method is the same - to place lightning conductors on the outside of the vessel with multiple air terminals at the top and multiple grounding terminals at the waterline. This provides a shielding enclosure, external current pathways, and more effective grounding to the water surface. We can also address lightning issues with metal-hulled vessels ranging from jon boats to supertankers, and can give advice on electronics protection by considering wire routing, shielding and surge suppression.

The desirable features of a ship lightning protection system cover a broad range from personal safety of passengers, surge protection of electronics, protection of vulnerable instruments or structures, lowered downtime to repair lightning damage, safety procedures for loading explosive materials, etc. Over the years we have had many enquiries from ship agents who have been interested in addressing lightning protection and are very familiar with both the type of damage to be expected and the techniques needed to address any problem that might be encountered. While the priorities for each lightning protection project vary from ship to ship, one common feature for all projects is that in a task of this size an appropriate amount of analysis is required in order to assess the best course of action. In order to expedite this we recommend our so that we can give the matter the attention it deserves. Given the wide range of potential issues with lightning protection of ships, it is not surprising that a common problem is that the agent does not understand how to define the most pressing concern. Ill defined Class regulations, use of ambiguous terms such as "lightning arrestor", and the widespread availability of devices with checkered histories do not help. To this end we offer a standard 20-hour consulting package that provides basic concepts, identifies prioritized issues, and develops the framework for an effective lightning protective process. Please us with questions or details. features single component silicon bronze electrode Since a lightning protection system is intended to protect the hull and occupants, electronics is still vulnerable. Even in metal-hulled vessels damage to electronics systems is pervasive. We are now addressing this issue and can supply both parts and advice to minimize the risk. As an example, consider the following three tiers of protection that we recommend for catamarans: even in the Tier 1 system we include surge suppression on all wiring exiting the mast. Since CFC is a conductor, but not a good one, it is difficult to deal with when designing a lightning protection system. Since we have not been able to design and test a reliable air terminal support for CFC masts, unfortunately we can no longer offer advice or devices for protection for them. Carbon fiber rigging is also a risk factor that we can do little about. Enveloping the interior with a conducting steel or aluminum hull still leaves all topsides transducers vulnerable. We deal with each metal vessel on a customized basis to identify the major vulnerabilities and then develop appropriate techniques and hardware to lower the risks of direct lightning attachment, formation of upward streamers, and damage from voltage surges on cables. Since current flow during lightning strikes appears to be via sparks, even below the waterline, we have developed the GStud ($200 each) , a silicon bronze immersed grounding electrode suitable for additional grounding near bow thrusters, hull transducers, keel-stepped masts, etc. Since these are embedded in a Marelon through-hull they are ideal for CFC hulls. Another product that now is available in silicon bronze is our Siedarc electrode in either a mushroom (SE-M-SiBr) or flush through-hull (SE-F-SiBr) @ $150. Add $30 for fairing. electrodes A recent report from one of our customers has shed some light on how our electrodes function - by forming sparks just above the water surface that neutralize the ground charge residing on the surface. See the discussion and animation on our page, or click here for a . Boat US has released their latest statistics for lightning claims. These show that not only are there twice the frequency of multihull claims, compared with monohulls, but also the average claim is 67% higher. See all the statistics . Also, we explain the higher strike frequency for catamarans in terms of their wider footprint. This leads us to conclude that you can increase your risk by 5-10 times when you anchor out, even if you are in a monohull! The October 2007 edition of Boat US's Exchange explains this novel concept. See the article . This concept has been incorporated into the National Fire Protection Association Lightning Protection Standard NFPA780-2011, and later versions, that are now . The watercraft section is Chapter 10 in the new (2011) version. Derivations for the new formulae regarding the use of metallic fittings in the system are published Also read in the May 2009 edition of MotorBoating. See our for pictures and descriptions of systems on all types of power and sail boats.

Principles Our approach to lightning protection is based solidly on observation and scientific theory.  The foundation was established in a published in 1991 in the prestigious  IEEE Transactions of Electromagnetic Compatibility.  As a result of this paper, subsequent renditions of standards published by ABYC and NFPA upgraded their recommended sizes for down conductors from #8AWG to #4AWG and noted that a ground strip is a more effective grounding conductor than a square plate of the same area.  Another fundamental problem revealed in this scientific work was that a one square foot ground plate is "hopelessly inadequate" to prevent sideflashes in fresh water.This was not addressed in these earlier standard rewrites since, at the time, there was no obvious solution.  We can now solve this problem with our patented Siedarc electrodes that, when distributed around the hull, provide the multiple exit points needed for effective grounding.  More recently, we have worked with the NFPA 780 technical committee to establish a new standard based on these new ideas, that is now published as Chapter 8 in the 2008 version of This standard is based on the simple concept that a boat should be protected the same as a building, with the lightning conductors on the outside rather than through the middle of the boat. As the ground attachment path for a 5-mile long spark carrying tens of kiloamperes, the protection system has the task of safely diverting this current around crew, sensitive electronics, and hull components.  However, even when the current is flowing in the water, voltage differences can cause sideflashes, both inside the boat and between the boat and the water. These present a shock hazard to the crew, produce overvoltage in electronics systems, and can blast holes through the hull. Management of the sideflash problem is the fundamental issue in the design of an effective marine lightning protection system. page for a technical explanation of the underlying concepts and suggestions as to how these can be applied to a protection system. Sideflash management is the objective An interesting feature of hull damage is the tendency for sideflashes to form around about the waterline.  Apparently either the water surface or the waterline itself causes charges to accumulate, usually on internal conducting fittings, and initiate sparks through the hull.  The effect is more pronounced in fresh water than salt. Photo by Dave Edwards In lightning protection circles, the conventional solution to a problem such as this is to add conductors where the damage is observed.In the above case this means placing lightning conductors through the hull at the waterline. Since it is impractical to install multiple ground plates in a hull, we developed the Siedarc electrode to provide the necessary exit terminals. This is effectively an air terminal near the water.In fact, each  In order to investigate the effectiveness of this concept, we tested an electrode with a 10kV generator for both salt and fresh water at Kennick Inc. in St. Petersburg.  Even though 10kV is much lower than what would be expected during a lightning strike, we obtained results that clearly indicated the promising potential for the method and further elucidated the best mode of operation.  Specifically, in the photo below, with the electrode about 1/4" above the surface of salt water, a spark of about 15" in diameter was produced. Clearly the sparking is contained very close to the water surface, perhaps even above it, showing the importance of the surface for current dissipation. In fresh water, the spark connected all the way to the sides of the container, about 12" away.  In contrast, when the electrode tip was immersed just below the water surface, a small (~ / ") glow was observed but no sparks.  The conclusion is that an electrode can generate a spark that is orders of magnitude longer than the spark gap in air when placed above the water surface.  Hence the optimum placement is just above the water surface.  The animation below illustrates how we expect the Siedarc electrodes to function.  See our page for more details Providing exit terminals around the perimeter of the hull is the key to an effective system design since, in addition to dispersing the current more uniformly around the boat, it also enables the lightning down conductors to be routed externally to all wiring and conducting fittings.  This is illustrated for a sailboat on the right.  The lightning conductor from mast base connects to both the chain plate and the loop before passing down to a daisy-chain Siedarc electrode just above the waterline, and from there via an immersed HStrip to a keel bolt (and base of a keel-stepped mast).  Siedarc electrodes at  bow and stern provide more exit terminals from the loop to the water.  This geometry is mirrored on the port side, as indicated by the dashed lines.  That is, there is a total of two HStrips and six Siedarc electrodes.  Thus a conducting grid covers the interior of the boat and a total of eight exit terminals are distributed over the hull near the waterline.  For a keel-stepped mast, make another connection from the mast base to both the keel bolt and the HStrips. Guiding the current on the outside rather than through the middle of the boat minimizes shock risk and emi.  In addition, a bonding loop around the boat at about deck level equalizes potentials, provides additional paths for current flow, and can be used for bonding conducting fittings.  In a major departure from the status quo, NFPA (the National Fire Protection Association) has recently revised their watercraft standard (NFPA 780 Ch.8) to include the concepts of a loop conductor, external down conductors, and perimeter grounding electrodes.   See our page for details.  With this new system the conductor layout more closely mirrors that found on the typical lightning protection system on a building.  We call this system of external lightning conductors and peripheral exit terminals the ExoTerminal protection system. In the photo below, we have shown where additional (internal) lightning conductors, grounding terminals, and air terminals were installed to fabricate this type of system. Products & services We can provide all of the components needed in a marine lightning protection system - air terminals, connections, grounding strips and Siedarc electrodes. See our page for details. We also offer for: Contact 3215 NW 17th Street Gainesville Florida 32605         Niosh Ag Centers Recent Additions Boating- Lightning Protection Those who enjoy Florida's waters certainly should understand the phenomena of thunderstorms--lightning and the precautions to take in order to keep these activities pleasurable--and how to prevent tragedy. While this phenomenon is occurring in the clouds, a similar phenomenon is occurring on the surface. Negative charges repel negative charges and attract positive charges. So, as a thunder cloud passes overhead, a concentration of positive charges accumulates in and on all objects below the cloud. Since these positive charges are attempting to reach the negative charge of the cloud, they tend to accumulate at the top of the highest object around. On a boat that may be the radio antenna, the mast, a fishing rod, or even you! The better the contact an object has with the water, the more easily these positive charges can enter the object and race upward toward the negative charge in the bottom of the cloud. Lightning occurs when the difference between the positive and negative charges, the electrical potential, becomes great enough to overcome the resistance of the insulating air and to overcome the resistance of the insulating air and to force a conductive path between the positive and negative charges. This potential may be as much as 100 million volts. To help you understand the magnitude of this voltage, the voltage needed in an automobile to cause a spark plug to fire is only 15 to 200 volts! And the spark plug gap is but a fraction of an inch! Lightning strikes represent a flow of current from negative to positive, in most cases, and may move from the bottom to the top of a cloud, from cloud to cloud, or most-feared, from cloud to ground (see Figure 3). And when the lightning does strike, it will most often strike the highest object in the immediate area. On a body of water, that highest object is a boat. Once it strikes the boat, the electrical charge is going to take the most direct route to the water where the electrical charge will dissipate in all directions. A second example is a sailboat. Lightning strikes the mast. The electrical current follows the mast or wire rope to your hands, through your body to the wet surface, and then through the hull to the water. Or, while operating a motor boat, the lightning strikes you, passes through your body to the motor, and then to the water. Or, sitting in your aluminum or fiberglass rowboat, you are holding a graphite (a good electrical conductor) fishing rod. The rod is struck by lightning. The electrical charge passes through the rod, your body, then to the boat to the water. In all four examples you could be seriously injured. You could be dead. Watch for the development of large well-defined rising cumulus clouds. Once they reach 30,000 feet the thunderstorm is generally developing. Now is the time to head for shore. As the clouds become darker and more anvil-shaped, the thunderstorm is already in progress. Watch for distant lighting. Listen for distant thunder. You may hear the thunder before you can see the lightning on a bright day. Seldom will you hear thunder more than five miles from its source. That thunder was caused by lightning 25 seconds earlier. The sound of thunder travels at one mile per five seconds (see Figure 4). But small boats are seldom made of metal. Their wood and fiberglass construction do not provide the automatic grounding protection offered by metal-hulled craft. Therefore, when lightning strikes a small boat, the electrical current is searching any route to ground and the human body is an excellent conductor of electricity! Today's fiberglass-constructed small boats, especially sailboats, are particularly vulnerable to lightning strikes since any projection above the flat surface of the water acts as a potential lightning rod. In many cases, the small boat operator or casual weekend sailor is not aware of this vulnerability to the hazards of lightning. These boats can be protected from lightning strikes by properly designed and connected systems of lightning protection. However, the majority of these boats are not so equipped. If you are considering the purchase of a new or used boat, determine if it is equipped with a properly designed and installed lightning protection system. Such a system is generally more effective and less costly than a system installed on a boat after it has been constructed. The mast, if constructed of conductive material, a conductor securely fastened to the mast and extending six inches above the mast and terminating in a receiving point, or a radio antenna can serve as the air terminal. The main conductor carries the electrical current to the ground. Flexible, insulated compact-stranded, concentric-lay-stranded or solid copper ribbon (20- gauge minimum) should be used as the main conductor. The ground plate, and that portion of the conductor in contact with the water, should be copper, monel or navel bronze. Other metals are too corrosive. The secondary conductors ground major metal components of the boat to the main conductor. However, the engine should be grounded directly to the ground plate. Lightning arrestors and lightning protective gaps are used to protect radios and other electronic equipment which are subject to electrical surges. The connectors must be able to carry as much electrical current as other components of the system. Further, the connections must be secure and noncorrosive. On a large power boat or sailboat, a properly designed and grounded antenna could provide a cone of protection. Presently, however, the vast majority of the radio antenna is totally unsuitable for lightning protection. This is also true of the wires feeding the antenna. If the antenna is not properly grounded, it may result in injury or death and cause considerable property damage. Ideally, an effective ground plate should be installed on the outside of all boats when the hulls are constructed. Unfortunately, this is not often done. Such a ground plate would help manufacturers design safer lightning protection systems for the boats. A lightning protective mast will generally divert a direct lightning strike within a cone-shaped radius two times the height of the mast. Therefore, the mast must be of sufficient height to place all parts of the boat within this cone-shaped zone of protection (see Figure 6). The path from the top of the mast to the "water" ground should be essentially straight. Any bends in the conductor should have a minimum radius of eight inches (see Figure 7). Major metal components aboard the boat, within six feet of the lightning conductor, should be interconnected with the lightning protective system with a conductor at least equal to No. 8 AWG copper. It is preferable to ground the engine directly to the ground plate rather than to an intermediate point in the lightning protection system. If the boat's mast is not of a lightning protective design, the associated lightning or grounding connector should be essentially straight, securely fastened to the mast, extended at least 6 inches above the mast and terminate in a sharp receiving point. The radio antenna may serve as a lightning protective mast, provided it and all the grounding conductors have a conductivity equivalent to No. 8 AWG copper and is equipped with lightning arrestors, lightning protective gaps, or means for grounding during electrical storms. Most antennas do not meet these requirements. The height of the antenna must be sufficient to provide the cone-shaped zone of protection. Antennas with loading coils are considered to end at a point immediately below the loading coil unless this coil is provided with a protective device for by-passing the lightning current. Nonconducting antenna masts with spirally wrapped conductors are not suitable for lightning protection purposes. Never tie down a whip-type antenna during a storm if it is a part of the lightning protection system. However, antennas and other protruding devices, not part of the lightning protection system, should be tied down or removed during a storm. All materials used in a lightning protective system should be corrosion-resistant. Copper, either compact-stranded, concentric-lay-stranded or ribbon, is resistant to corrosion. The "water" ground connection may be any submerged metal surface with an area of at least one square foot. Metallic propellers, rudders or hull will be adequate. On sailboats, all masts, shrouds, stays, preventors, sail tracks and continuous metallic tracks on the mast or boom should be interconnected (bonded) and grounded. Small boats can be protected with a portable lightning protection system. This would consist of a mast of sufficient height to provide the cone of protection connected by a flexible copper cable to a submerged ground plate of at least one square foot. When lightning conditions are observed in the distance, the mast is mounted near the bow and the ground plate dropped overboard. The connecting copper cable should be fully extended and as straight as possible. The boaters should stay low in the middle or aft portion of the boat. Stay in the center of the cabin if the boat is so designed. If no enclosure (cabin) is available, stay low in the boat. Don't be a "stand-up human" lightning mast! Keep arms and legs in the boat. Do not dangle them in the water. Discontinue fishing, water skiing, scuba diving, swimming or other water activities when there is lightning or even when weather conditions look threatening. The first lightning strike can be a mile or more in front of an approaching thunderstorm cloud. Disconnect and do not use or touch the major electronic equipment, including the radio, throughout the duration of the storm. Lower, remove or tie down the radio antenna and other protruding devices if they are not part of the lightning protection system. To the degree possible, avoid making contact with any portion of the boat connected to the lightning protection system. Never be in contact with two components connected to the system at the same time. Example: The gear levers and spotlight handle are both connected to the system. Should you have a hand on both when lightning strikes, the possibility of electrical current passing through your body from hand to hand is great. The path of the electrical current would be directly through your heart--a very deadly path! It would be desirable to have individuals aboard who are competent in cardiopulmonary resuscitation (CPR) and first aid. Many individuals struck by lightning or exposed to excessive electrical current can be saved with prompt and proper artificial respiration and/or CPR. There is no danger in touching persons after they have been struck by lightning. If a boat has been, or is suspected of having been, struck by lightning, check out the electrical system and the compasses to insure that no damage has occurred. Boating in Florida's waters is an enjoyable activity for many people. Keep it that way! Listen to the weather reports! Learn to read the weather conditions. Heed these reports and the conditions. Stay off or get off the water when weather conditions are threatening. Install and/or maintain an adequate lightning protection system. Have it inspected regularly. Follow all safety precautions should you ever be caught in a thunderstorm. By using good judgment, it is less likely that first aid or CPR will be needed while boating. National Fire Codes. Lightning Protection Code--NFPA 78; Fire Protection Standard for Motor Craft--NFPA 302, 14. National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Standards and Recommended Practices for Small Craft. Standard E-4, Lightning Protection. American Boat and Yacht Council, P.O. Box 806, Amityville, NY 11701. Sitarz, Walter A. Boating Safety--Thunderstorms (MAP-5), Florida Sea Grant College Program, University of Florida, Gainesville, FL 32605. William J. Becker, Professor and Extension Safety Specialist, Agricultural Engineering Department, Cooperative Extension Service, Institute of Food Publication #: SGEB-7 October 1992 Disclaimer and Reproduction Information: Information in NASD does not represent NIOSH policy. Information included in NASD appears by permission of the author and/or copyright holder. More Lightning protection on sailboats is an un-researched area of knowledge.  Most of the information is based on the theoretical physics of lightning coupled with experiential and anecdotal evidence.  This doesn't mean we know nothing about the matter. The articles and links below pretty much cover the ground and I suggest you read them over before deciding the level and complexity of any lightning protection system for you boat.  Two things seem clear: You CANNOT make a boat lightning proof, nor even much reduce the chances of a strike. You CAN significantly improve the chance you and your equipment will survive a strike. Don't have the Adobe Acrobat� free Reader?  .  Recommendations for Lightning Protection provided by the American Boat & Yacht Council, Standard E4.  (KP44 website page) Grounding Your Vessel . Technical articles and links on grounding: on the kp44.org website Air Terminals (i.e. lightning rods) by Ewen M Thomson, Univ. Fla. Sea Grant.  Lightning & Sailboats . (i.e. lightning rods) by Ewen M Thomson, Univ. Fla. Sea Grant Publication. 1992. Very good publication. Articles and Letters on Lightning and Boats by Ewen M. Thomson.  Terrific resource for lightning info. World Wide Opposition to ESE Lightning Rods   from National Lighting Safety Institute, May 13, 2003.  (Article dated 1999, by Abdul Mousa). Considerations for Lightning Protection. A very excellent analysis of the problem.  Presented in the blog of Domino – a 65' power catamaran. Forespar "Lightning Master" Static Dissipater .  Supposedly "leaks off lightning causing ground potential".  Mousa, Thomson  (above) and others disagree, saying the ground potential on structures below 300 meters is meaningless in terms of lightning strikes.   Lightning Master Corporation .  Surge protectors and Dissipaters.  DIssipaters are pretty much shown to be ineffective, but surge protection for onboard electronics is important. Marine Lightning Protection, Inc. Founded by Ewen M Thomson. Best information on the web. Provider of air terminals and lightning protection systems . In particular look at his page on Grounding and Sidearc™ electrodes which is currently state-of-the art. 106 IMAGES Sailing in lightning: how to keep your yacht safe Esitellä 36+ imagen sailboat lightning protection Modern Lightning Protection On Recreational Watercraft Weathervanes and Lightning Rods 37918: Beautiful Copper And Brass Make a grounding system to protect your boat from lightning strikes Lightning Protection for Boats, Sailboats and Yachts COMMENTS Sailing in lightning: how to keep your yacht safe In salt water this needs a minimum area of 0.1m². In fresh water, European standards call for the grounding terminal to be up to 0.25m². A grounding terminal must be submerged under all operating conditions. An external lead or iron keel on monohull sailing boats can serve as a grounding terminal. Lighting Protection for Boats EvoDis Lightning Prevention System dissipates the ground charges on mast through thousands of tiny sharp points and blocks the emission of these charges by keeping the surrounding electric field strength below the threshold level. This process makes the protected boat "invisible" to lightning; prevents any damage on electronics and sensors ... Lightning Protection: The Truth About Dissipators A bit of math will show that a carefully designed static discharge wick or brush can create a current, in an electrical field of 10,000 volts per meter, of 0.5 ampere. This is equivalent to a 20,000 ohm impedance (R=E/I: R=10,000/0.5 = 20,000). The impedance of a site on hard ground is typically 5 ohms. Modern Lightning Protection On Recreational Watercraft Air terminals (lightning rod or Franklin rod) should be installed at the highest points of masts, towers, etc. On a sailboat a single air terminal could be bolted to the mast; on a sportfish it could be bolted to the tower and made to look like an antenna. A Quick Comprehensive Guide to Lightning Protection for Boats Key Components of a Boat's Lightning Protection System: Wiring, Air, and Ground Terminals. Bonding systems are typically designed to prevent corrosion, however, when used in conjunction and compliant with a lightning protection system, they can improve safety and reduce damage. Bonding systems connect underwater metals, deck gear, spars ... Yacht lightning strikes: Why they cause so much damage and how to According to US insurance claims (from BoatUS Marine Insurance) the odds of a boat being struck by lightning in any year are about 1 per 1,000, increasing to 3.3 per 1,000 in lightning prone areas ... Lightning Strikes And Boats: How To Stay Protected The likelihood of your boat being struck by lightning depends on a number of factors. Not surprisingly, sailboats are more likely to get hit by lightning than power boats. According to data, sailboats generally have a 155% greater chance of being strike by lightning than powerboats (40 out of 10,000 for sailboats, as opposed to 5 out of 10,000 ... What to Do in a Lightning Storm on a Boat A conventional lightning-protection system consists of an air terminal (lightning rod) above the boat connected to a thick wire run down to an underwater metal ground plate attached to the hull — large metal objects like tanks, engines and rails are also connected. New studies suggest multiple terminals and multiple ground paths work better. Sailboat Lightning Protection: Technical Advice In 2006, the American Boat and Yacht Council (ABYC) technical information report TE-4 [3], [4] recommended the following:-. • lightning protection system conductors must be straight and direct and capable of handling high currents. The main 'down' conductor is recommended to be 4AWG, or 25mm2 in European sizing; see diagram. How to Protect Your Boat From a Lightning Strike The CDC says Florida is the "lightning capital" of the U.S.; BoatUS says about one third of all lightning-related marine insurance claims come from Florida. The majority of lightning strikes happen on sailboats, adds BoatUS, as an aluminum mast makes a great lightning rod (or "air terminal" in today's parlance). FORESPAR Lightning Master™ Static Dissipater Reduce your boat's exposure to a direct lightning strike. Forespar's Lightning Master Static Dissipater lowers the exposure to a direct lightning strike by controlling the conditions which trigger direct strike (i.e. it reduces the build-up of static ground charge and retards the formation of the ion "streamers" which complete the path for a lightning strike). How to Protect Your Boat From Lightning Thompson found that the best lightning rod is a ½ inch in diameter with a rounded top. Located at the bow, the stern, and above the highest points can help create the basis of your cage. The rods need to be connected with heavy two-gauge wire. The wire needs to travel the easiest path to the water's surface. Lightning Protection If your sailboat is a vessel with an aluminum mast you have the starting point of a well-grounded lightning rod. This will provide a zone of protection for a radius around its base equal to the height of the lightning rod. Due to some vessels overall length, it may be necessary to install another lightning rod to encompass any areas that do not ... How to Prepare for Lightning Strikes To conduct a strike safely to "ground" (on a boat this means to the water), create a low-resistance path from the highest point on your boat to a metal grounding plate in contact with the water. Start with a solid half-inch-diameter steel or bronze rod elevated six to 12 inches above every other object on the boat. Build your system The distinctive feature in a sailboat is the pre-existing lightning rod that carries the sails. If the mast is aluminum it can be used as a main down conductor, although it is advisable to add an air terminal at the masthead for protection of transducers. If the mast is carbon fiber then using it as a down conductor may result in its destruction. Lightning and Boating: How to Stay Protected Remove all metal jewelry, avoid electrical outlets and appliances, and disconnect any power cords, leads, or antennas. Stow metal equipment such as fishing rods and lower outriggers. Stay out of the water and wait at least 30 minutes after the last round of thunder before resuming normal boating activities. Thunder Struck: Protecting your Boat from Lightning Strikes While protecting your boat against lightning strikes is advisable to cruisers, especially those that sail in areas that are prone to lightning strikes, the best way to avoid damage from lightning is to avoid lightning altogether. One tool that can help coastal sailors combat a run-in with lightning is Sirius XM Satellite Weather ( siriusxm.com ... Lightning Protection for Boats, Sailboats and Yachts ... Lightning is one of the biggest threats to sailboats, yachts, and catamarans. Traditional lightning rods cannot protect them because they attract lightning o... Lightning Protection for Boats, Sailboats and Yachts Lightning rods are invented more than 300 years ago to protect non-conductive buildings from lightning strikes. Conductive structures such as boat masts cannot be protected by lightning rods because the lightning rod attracts lightning strikes on itself and naturally to the mast. Marine Lightning Protection Inc Marine Lightning Protection Inc. Being at the forefront of both the basic science and product development in this area, we are uniquely qualified to address all of the problems inherent in lightning protection on the water. Whether for a fiberglass jet ski or a superyacht our method is the same - to place lightning conductors on the outside of ... Does My Boat Have Lightning Protection? Lightning is as unpredictable as ever, and no boat builder can guarantee protection. There are some accepted best practices, though. By Ed Sherman. August 10, 2013. Question: In the photo I sent along you can see one of the wires attached to the chainplates on my new sailboat. The boat has one wire on the port side and another on the starboard ... NASD Today's fiberglass-constructed small boats, especially sailboats, are particularly vulnerable to lightning strikes since any projection above the flat surface of the water acts as a potential lightning rod. In many cases, the small boat operator or casual weekend sailor is not aware of this vulnerability to the hazards of lightning. Lightning Protection on Sailboats Lightning & Sailboats. (i.e. lightning rods) by Ewen M Thomson, Univ. Fla. Sea Grant Publication. 1992. Very good publication. Articles and Letters on Lightning and Boats by Ewen M. Thomson. Terrific resource for lightning info. World Wide Opposition to ESE Lightning Rods from National Lighting Safety Institute, May 13, 2003. (Article dated ... catamaran gulet powerboat riverboat sailboat trimaran yacht