lightning strike 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.

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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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• Yachting World
• Digital Edition

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.”

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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’

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What to do in a Lightning Storm on a Boat

• By Mike Telleria
• Updated: February 10, 2020

Powerful, dangerous, highly unpredictable — all are common descriptions of lightning storms. A direct strike that results only in ringing ears and a few roasted electronics would be considered lucky. Unlucky would be through-hulls blown out, a sunk boat or worse — possibly serious injury or death.

Many powerboaters like to think that they’ve got the speed to simply outrun or get out of the way of lightning storms , or they figure they’re safe if they go boating only when it’s clear and sunny. That’s an attitude aided by the low odds of a boat being struck by lightning, which BoatU.S. pegs at about one out of 1,000 boats in any given year.

No worries, right, mate? Wrong.

Engines can malfunction ; big lightning storms can leave no room to escape; sunny mornings can turn into dark, threatening afternoons. If yours is the only boat in the area during a lightning storm, the odds of being struck go way up, leaving you and your crew vulnerable to millions of volts raining down from the skies. Lightning and boats do not mix. While manufacturers can build in a degree of protection, lightning protection begins with boaters being informed and prepared to act in the event of a thunderstorm or actual strike. You should know the following techniques and strategies.

Boating in a Thunderstorm is Bound to Happen at Some Point

A strategy of boating only on sunny, cloudless days may work well in places like Idaho and California, but that would mean almost never using the boat in places such as Florida, Louisiana and much of the Midwest. For example, most of Florida — the Sunshine State — has at least 70 to 80 thunderstorm days per year, with some parts having more than 100 thunderstorm days per year (with increased activity during the summer months).

Absolutely, boaters should track VHF , Internet and television weather reports and make responsible decisions about whether to go boating depending on the likelihood of lightning storms. Short-term forecasts can actually be fairly good at predicting bigger storms, but small, localized storms might not be reported. This is when knowing how to read the weather yourself can come in handy. (The U.S. Power Squadrons offers great weather courses for boaters, and there are many books that cover the basics.)

Lightning strikes typically occur in the afternoon. (Florida estimates 70 percent occur between noon and 6 p.m.) A towering buildup of puffy, cotton-white clouds that rise to the customary flat “anvil” top is a good indication to clear the water and seek shelter — or move out of the storm’s path if possible. That’s if the storm is at least somewhat off in the distance (most storms are about 15 miles in diameter and can build to dangerous levels in fewer than 30 minutes). If lightning and thunder are present, just count the seconds between the lightning and corresponding thunder and then divide by 5 — this will provide a rough estimate of how many miles away the storm is.

A storm that builds directly overhead might be less obvious until those pretty white clouds that were providing some nice shade moments ago turn a threatening hue of gray as rain dumps on you and the wind starts to howl or, worse yet, boom with thunder and lightning that are right on top of each other. Now is the time for a mad dash to the dock and shelter if close by. Like the National Weather Service says: “When thunder roars, go indoors!” You really don’t want to be on a boat struck by lightning. If out on open water or too far from shore and shelter, it’s time to hunker down and ride it out.

Caught in Thunderstorm on a Boat

Boaters who have been struck by lightning often begin their stories with “I was caught in this storm … ” before they share their miraculous or harrowing tales of survival and destruction (BoatU.S. has a number of first-person storm stories archived online: boatus.com/seaworthy/swthunder). Even though getting caught in a storm is not always avoidable, there’s still plenty that boaters can do to minimize the chance of a strike and lessen injury and damage if there is a strike.

How to Stay Safest in a Thunderstorm

We all learn in grade school that it is not safe to be outside during a lightning storm. We also learned that lightning seeks the highest point, and on the water that’s the top of the boat — typically a mast, antenna, Bimini top, fishing rod in a vertical rod holder or even the tallest person in an open boat. If possible, find a protected area out of the wind and drop anchor . If the boat has an enclosed cabin, people should be directed to go inside and stay well away from metal objects, electrical outlets and appliances (it’s a good idea to don life jackets too). Side flashes can jump from metal objects to other objects — even bodies — as they seek a path to water.

A Microwave Oven is a Faraday Cage

Lowering antennas, towers, fishing rods and outriggers is also advised, unless they’re part of a designated lightning-protection system. Some boaters also like to disconnect the connections and power leads to their antennas and other electronics, which are often damaged or destroyed during a strike or near strike.

Under no circumstances should the VHF radio be used during an electrical storm unless it’s an emergency (handhelds are OK). Also, be careful not to grab two metal objects, like a metal steering wheel and metal railing — that can be a deadly spot to be if there’s a strike. Some boaters opt to steer with a wooden spoon and keep their other hand in a pocket if forced to man the helm during a storm, while others like to wear rubber gloves for insulation.

Surviving Lightning Strikes While Boating

An open boat like a runabout is the most dangerous to human life during lightning storms, since you are the highest point and most likely to get hit if the boat is struck. If shore is out of reach, the advice is to drop anchor, remove all metal jewelry, put on life jackets and get low in the center of the boat. Definitely stay out of the water and stow the fishing rods.

If all goes well, the storm will blow past or rain itself out in 20 to 30 minutes. It’s best to wait at least 30 minutes until after the last clap of thunder to resume activities.

There’s a Zap For That

What to do when your boat is struck by lightning.

Knowing what to do in a storm and having the best lightning-protection system installed on the boat is by no means a guarantee that lightning won’t strike. The immediate checklist for a direct hit is very short:

1. Check for unconscious or injured persons first. If they’re moving and breathing, they’ll likely be OK. Immediately begin CPR on unconscious victims if a pulse and/or breathing is absent — there’s no danger of being shocked by someone just struck by lightning.

2. In the meantime, have someone check the bilges for water. It’s rare, but lightning can blow out a transducer or through-hull — or even just blow a hole in the boat. Plug the hole, get the bilge pumps running, work the bail bucket — whatever it takes to stay afloat. An emergency call on the VHF is warranted if the situation is dire. If the radio is toast, break out the flare kit.

If there are no injuries and no holes or major leaks below, just continue to wait it out. Once the danger has passed, check the operation of the engine and all electronics. Even a near strike can fry electronics and an engine’s electronic control unit, cutting off navigation, communication and even propulsion. Some boaters stash charged handheld VHF and GPS units and a spare engine ECU in the microwave or a tin box for this very reason. These makeshift Faraday cages have saved equipment.

One in 1,000 Boats Are Hit by Lightning Per Year

Obvious damage will need to be assessed and set right. Even those lucky enough to come away completely unscathed after lighting storms, with no apparent damage should have a professional survey done just to be sure. Minor damage to through-hulls can result in slow leaks, and all manner of electrical wackiness can emerge — sometimes much later. It’s best to catch these issues right away and get that information to the insurance folks for coverage.

Is Just a Ground Plate Enough?

On many levels, robust insurance coverage plays a huge role in your lightning-protection plan. Knowing how to avoid lighting storms and read the weather are certainly important, being ready for action in the event of a storm or strike is crucial, and an upfront investment in lightning protection can lessen destruction. When it comes to dealing with the aftermath of a damaging strike, however, extensive lightning strike coverage can’t be beat.

Take it from a luxury trawler owner who sustained more than $1 million in damage from a strike: “Boat insurance turns out to be the best investment we have made in the past 10 years!” he said. “We will never again grumble about writing a check for an insurance premium.”

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How Often Do Sailboats Get Struck By Lightning?

Last Updated by

Daniel Wade

April 26, 2023

‍ Key Takeaways

• A lightning protection system can help mitigate a lightning strike.
• Lightning storms can form anytime when offshore sailing so prepare the best you can.
• If you see lightning strikes nearby you should move to the middle of the boat.
• Multihull sailboats attract lightning more than other types of boats.
• Perfect lightning protection does not exist so plan accordingly before sailing.

‍ Sailing during rough weather can be a dangerous situation. But how often do sailboats get struck by lightning?

Sailboats are hit with lightning strikes at a rate of four per 1,000 on average. Various boats in Florida on average have a rate of 3.3 out of 1,000, so location matters. The chance of any boat being struck by lightning in a given year is one in 1,000.

According to insurance claims for places like Florida that get hit with lightning strikes often every year, these numbers only reflect reported damage to sailboats. Marine surveyors warn that these numbers could be slightly higher so the chance of your boat being struck by lightning is still dangerous no matter how little or significant the risk is.

Table of contents

‍ The Chances of Sailboats Being Hit by a Lightning Strike

Some will argue that the size and type of your boat do not matter when it comes to lightning strikes. This is not true since some boats have been reported to be more susceptible to lightning strikes than others.

Lighting strikes are not your fault but there are some things you can do to help lower the chances of your sailboat being struck by lightning. While there is no guarantee in a lightning protection plan, having all materials and actions ready beforehand could save you money and someone’s life.

Multihull Sailboats

Multihull sailboats like catamarans or trimarans have a 6.9% chance of lightning strikes a year out of 1,000. Multihulls lack keels and with more exposed surface area face a greater risk of lightning strikes. Modern multihulls come with complex electronic systems that usually lead to costly damages from a lightning strike.

Monohull Sailboats

Monohull sailboats have a slightly lower occurrence of lightning strikes than multihull sailboats at 3.8% out of 1,000 per year. Just because they are less likely to be hit with lightning than multihulls does not mean you are in the clear.

Other Types of Boats

Other boats such as trawlers, bass boats, and even pontoon boats are at lower risk individually. These boats have less surface area and some are not even designed to be offshore where storms are intense. When combining those and all other boats besides sailboats, the risk of being struck by lightning is 0.9 out of 1,000.

Length of Sailboat

Your mast is an extension of your boat so you should sit and wait for the weather to pass before heading out to sea. According to Martin Uman, who leads the Lightning Research Group at the University of Florida , sailboats with 20 to 30 feet taller masts are almost three times more likely to be struck by lightning. This is due to the nature of electrical charge transfer between clouds and the ground despite lightning bolts being typically five miles long and one inch wide.

Sailing in the Rain

Rain clouds hold water and thunderstorm clouds carry electric charges. Interestingly enough, sailing in the rain is fine, but the accumulation of storm clouds is dangerous. Your focus should be on Nimbostratus and Cumulonimbus.

Nimbostratus clouds are flat, large, and closer to the ground. They can produce precipitation and span vast areas at a time. Safe boating in these conditions requires proper measures such as adequate rain protection, safety gear, GPS, and lighting for navigation and anchoring.

Why Are Sailboats a Target for Lightning Strikes?

Lightning strikes can hit boats during a lightning storm since some have metal masts and antennas. You are more susceptible to a lightning strike due to conductive material and turning your boat into a giant lightning rod.

This is especially true for sailboats with high aluminum masts since lightning can hit the mast before anywhere else on the boat. Fiberglass boats sitting low on the water are less likely to be struck by lightning.

How to Prepare for a Potential Lightning Strike

Boaters must be familiar with essential safety guidelines for thunderstorms. A practical approach to lightning protection is providing a safe discharge path for lightning. No technology currently exists to prevent lightning strikes so preparing for the worst is all you can do.

Update Insurance or Check the Policy

Ensure your sailboat has adequate insurance. If you do not have any or want to change you could always check out what BoatUS Marine insurance can do for you.

Seek Weather Updates

Equip modern weather detection gear and check the forecast before sailing. If thunderstorms are predicted you should stay in the harbor until the weather clears.

You can always tune into the VHF radio weather channel that is typically found on channels one through nine depending on your area. This gives you timely storm updates and critical information if you are out while a storm arrives.

If Stuck in the Middle of a Storm

Storms that will likely produce lightning strikes can pop up at a moment's notice at sea. If you are unable to outrun the storm, here are a few tips to consider:

• Wait it out and keep your shoes on while avoiding metal objects.
• Hold onto non-conductive items like fiberglass but beware that water can conduct electricity.
• Keep a hand in your pocket for safety and ensure no metal is inside.
• Use a vital piece of wood or rubber to control the steering wheel and set the throttles at idle or low throttle.
• Lower the antenna, outriggers, and any fishing rods.
• Stay close to the middle of the boat and remove any metal jewelry.
• If lightning strikes the boat you should immediately ask if everyone is okay and look for a hole that the lightning went through to ensure you are not taking on water.

Keeping Electronics Safe

It would be best to use transient voltage surge suppressors (TVSS) to safeguard crucial and lightning-sensitive equipment such as ECU/ECM, chart plotters, and instruments. These semiconductor devices suppress lightning-induced voltage spikes and are widely used in aviation, wind power, and telecommunications.

TVSSs function like voltage-sensitive fuses and redirect excess voltage as heat. Using TVSSs is a wise investment in preventing lightning damage to equipment even though this heat may damage them.

Ground Your Sailboat

For a grounding system, you should install lightning rods or terminals on top of the mast and connect them to the grounding plate to protect it from lightning. Use cable as a down conductor for wood or carbon masts and retrofit the grounding plate during haul out.

Monohulls require one plate, while ketches, yawls, and schooners need a path for each mast and a strip under the hull. Catamarans need two plates but a more extended plate outline is better for current dissipation.

Internal Bonding Circuit

A bonding system is a circuit inside a boat that links main metal objects to the grounding plate with cables. This reduces the risk of internal side strikes caused by current jumping between objects towards the ground.

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I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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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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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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Explained: Lightning strikes sailboat, sends sparks flying

Sparks flew off the mast of an unlucky sailboat in Boston Harbor after lightning struck on July 6.

Harry Minucci filmed this footage of a bolt of lightning hitting a vessel moored in the Columbia Yacht Club marina. Minucci told Storyful he took out his camera after seeing lightning strikes in the distance, and couldn’t believe he captured this moment on camera.

Luckily, nobody was on board at the time of the incident. Weather Network meteorologist Tyler Hamilton, because lightning yields a lot of power.

"First of all, the air surrounding the strike [seen in the video] heats to around 10,000 degrees Celsius."

In the same area, but invisible to the human eye, are negative and positive charges that combined to create the spectacular explosion seen in the video above. The crash could be heard from 20 km away.

the U.S. sees about 20 million lightning strikes each year.

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Techniques to lessen the impact of a lightning strike, adopting standardized lightning protection for boats, key components of a boat's lightning protection system: wiring, air, and ground terminals.

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How Likely Is Your Boat To Be Struck By Lightning

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Spring and early summer are the most active times for thunder and lightning storms. Here's the good news and the bad.

Photo: David Keen

According to reports from our BoatUS Marine Insurance claim files, the odds of your boat being struck by lightning in any year are about one in 1,000. Some states, such as Idaho, have no lightning claims (no surprise). But for those of you with boats in Florida, nobody has to tell you that the odds there are greater. Much greater.

Thirty-three percent of all lightning claims are from the Sunshine State, and the strike rate there is 3.3 boats per 1,000. Not surprisingly, the majority of strikes are on sailboats (four per 1,000), but powerboats get struck also (five per 10,000). Trawlers have the highest rate for powerboats (two per 1,000), and lightning has struck houseboats, bass boats, and even PWCs. Lightning-strike repairs tend to be expensive and time-consuming, but there are things you can do to lessen the damage after a strike.

You Can Run, But You Can't Hide

Volumes have been written about methods to mitigate damage or even avert a lightning strike. Lightning, however, doesn't seem to read them. As an example, one boat, fitted with a popular "fuzzy" static dissipater at the top of the mast, was struck twice in one year. Ironically, the second time the bolt hit the dissipater, it happened even though the VHF antenna right next to it was higher. Lightning is unpredictable. While you can mitigate the damage from a lightning strike, there is nothing you can do to prevent one. So here we'll focus on what to do if your boat is hit.

The Extent Of Damage Isn't Immediately Apparent

The first thing you should do if your boat is struck is call your insurance company and get your boat short-hauled as quickly as possible for a quick hull assessment. The reason is that when lightning exits your boat, it can leave via a thru-hull fitting or even through the hull itself. Even if the force of the bolt doesn't blow out a thru-hull or cause hull damage, it may cause a gradual leak that could go unnoticed and sink your boat. As part of its "sue and labor" provision, BoatUS Marine Insurance will pay to have your boat short-hauled to check for damage. The short-haul is not subject to a deductible.

Damage Is Determined By How The Strike Exits

In a properly bonded system that follows American Boat & Yacht Council standards, the strike should follow a low-resistance path to a boat's keel or an installed grounding plate, though few boats are equipped this way from the factory. While no two lightning strikes are exactly alike, examining a typical claim can shed some light on the possible damages your boat might have if it's ever struck; some may not even have crossed your mind. Example: Priority , a 33-foot sailboat, was struck in North Carolina during a July thunderstorm. Sailboats are nearly always struck on the mast — and this one was no exception. A damaged or missing VHF antenna is typically the first sign that an unattended boat was struck. Sometimes bits of a melted antenna are found on the deck.

It's no surprise that electrical devices are susceptible to strikes; NOAA estimates a strike contains around 30,000,000 volts, and a quick zap to a 12-volt device will certainly destroy it. But lightning is like horseshoes: "Close" counts. There can sometimes be collateral damage when a nearby boat gets hit, either the result of the lightning's powerful electromagnetic field or the current induced by the field running through the boat's shore-power cord. This can create strange problems; some electronics may work fine, others that are adjacent might not, and still others may only work partially. In some cases, compasses have been off by 100 degrees.

Lightning strikes can cause hull damage. If your boat has been struck, have it hauled to inspect for damage. (Photo: BoatUS Marine Insurance)

In one instance, the owner of a 28-foot sailboat noticed an amber LED on his battery charger that he'd never seen lit before, and his depth sounder had quit working. He couldn't figure out what had happened until his neighbor told him his boat had been struck. On another boat moored next to a struck boat, the compass readings were 50 degrees off and slowly returned to normal after a few weeks. But a direct hit usually causes more obvious and substantial damage.

When a boat gets struck, lightning is trying to find its way to ground, typically the water around and under the boat. When a sailboat like Priority gets struck, one of the paths the lightning takes is down the mast; typically, anything that happens to be close by on the way down can be destroyed: wind instruments, TV antennas, radar, lights, and so on.

Fortunately, aluminum is a very good conductor and allows the strike free passage. However, wood and carbon-fiber masts can get damaged because neither one is a good conductor. Thankfully, damage to the rigging is rare. Though mast-mounted components are the most likely to be destroyed, anything on the boat that is electronic can be damaged. As a general rule, if the equipment works OK after the boat was struck, it probably wasn't damaged; it's unusual for electronics to fail months later.

Often the first sign owners have that their boat was struck is that some of the boat's electronics don't work. Look for fuse failures, and if you have more than a couple of blown fuses, look to lightning as a possible cause. Powerboats are typically struck on the VHF antenna or bimini top, and though electronics are often destroyed, passengers are fortunately rarely injured. Sometimes, however, the engine electrical system is damaged. This underscores the need for nonelectronic signaling devices, such as flares, in case your boat is struck at sea and is taking on water or, worse, if someone is injured.

Lightning Can Be Brutal To Fiberglass

In the case of Priority , the lightning traveled down the mast in addition to the VHF coaxial cable. The cable had been disconnected and was resting against the hull inside the boat. When the strike exited the cable, it had no easy way to get to the water. After traveling a quarter of a mile through air, lightning has no trouble going through a fiberglass hull, and this is exactly what it did, blowing a 3-inch hole on the way. Fortunately, the hole was above the waterline, and the boat was saved from sinking.

Powerboats are also susceptible to hull damage and are less likely to have been fitted with a lightning-protection system. Fortunately, the strike usually exits the boat through the props and rudders, and aside from damage to the bottom paint, the running gear is not often damaged (although electronic engine controls sometimes are). Need another good reason to replace a leaking fuel tank? A 25-foot fishing boat with a small amount of fuel in the bilge exploded at the dock when it was struck, sending the contents of the boat's cockpit nearly 100 feet away. Rarely, the claims files show that lightning enters a boat's electrical system and creates enough havoc to start a fire.

Strike By Type Of Boat

Look for minor damage.

One component that is often destroyed is a ground fault circuit interrupter (GFCI). This can easily be overlooked after a strike. Though it may still power appliances, the protection circuit is often nonfunctional. A GFCI can be easily checked by pushing the test button on the cover. Other small items to check are handheld radios and GPS, bilge pumps, inverters, lights, and fans. It should be noted that lightning is fickle and boat damage varies enormously; one owner saw his boat struck on the mast and yet none of the electronics were damaged. The only evidence the surveyor could find of the strike was a blackened area on the masthead.

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Charles Fort

Contributing Editor, BoatUS Magazine

Charles Fort is BoatUS Magazine's West Coast Editor. He often writes local news items for BoatUS Magazine's Waypoints column and contributes to Reports, in-depth tech features in every issue written to help readers avoid accidental damage to their boats. He is a member of the National Association of Marine Surveyors, he's on ABYC tech committees, and has a 100-ton U.S. Coast Guard license. He lives in California.

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Lightning strikes sailboat

People and firefighters stand on the dock near the sailboat at the Silver Beach Marina that was hit by lightning on Friday. BILL BULEY/Press

People and firefighters stand on the dock near the sailboat at the Silver Beach Marina that was hit by lightning on Friday.

Channing Elvidge stands on his boat at the Silver Beach Marina, while people stand near the sailboat struck by lightning at a parallel dock in the background.

Some of the damage caused by a fire following a lightning strike on a sailboat at the Silver Beach Marina.

Some of the damage caused by a fire following a lightning strike on a sailboat at the Silver Beach Marina on Friday.

Jennifer Weeks checks on her boat next to the sailboat struck by lightning on Friday at the Silver Beach Marina.

COEUR d’ALENE — With a storm rolling in Friday morning, Channing Elvidge began putting up the front window on his boat at the Silver Beach Marina.

Then, he saw lightning strike the top of a sailboat mast about 50 yards across the water on another dock.

“No way that just happened," he thought.

It did. To prove it, thunder shouted from the sky.

“There was just like a boom,” he said.

Elvidge and wife Tammy Schneider hit the deck. She screamed.

“I thought it hit our boat,” Tammy said. “I was so scared.”

The mast was charred and smoking. A few minutes later, Elvidge saw smoke coming from the sailboat’s hatch.

“That’s not good,” he said.

Elvidge didn’t hesitate.

“You don’t think. You just run,” he said.

He charged down the dock and grabbed a fire extinguisher attached to the side decking. As he went, he yelled for someone to call the fire department and shouted for others to grab more extinguishers posted throughout the marina that was packed with boats.

When he reached the sailboat, about a 100-yard dash away, the inside of the boat was on fire and flames were halfway up the mast.

“It took off and burned like you can’t believe,” Elvidge said.

Within minutes, he and about five people began blasting away with fire extinguishers and knocked down the blaze before firefighters arrived.

“A bunch of good guys,” Elvidge said. “Everybody just stepped up.”

No one was on the boat and there were no injuries. The dock was not damaged.

Coeur d’Alene Fire Department Capt. Steve Jones praised their actions.

“I think they were heroic,” he said. “They absolutely prevented further damage from happening to any of the other boats on the marina.”

The 24-foot sailboat suffered extensive damage, but did not sink. It belongs to Rich Relyea, who arrived later and was on the phone with his insurance company.

He said he had owned the boat since 1987 and had many good memories of summers spent sailing with family on Lake Coeur d’Alene.

The boat hadn’t been used often lately, but he had plans to get out on it more this summer.

The storm rumbled from a distance before 9 a.m. It had been slowly moving in, with whitecaps on the lake, as skies turned gray with dark clouds and sheets of rain fell hard.

It hit the marina on Coeur d'Alene Lake Drive with a bang.

“I never heard thunder that loud,” said Dick Miller, who was at the marina on a boat.

Reilly Chapman, Silver Beach Marina employee, was inside the store when she heard “the loudest thunder clap" in her life.

Initially, she thought the store was hit. Then, she hurried outside and saw smoke. She grabbed a fire extinguisher and hurried to help.

"We all just sprinted," she said.

Chapman didn’t know the extent of damage or the situation, but thought lives could be at stake.

“If any other boats got hit we could have major blowups,” she said.

Chapman used the training she and other marina staff received the previous day with fire extinguishers: aim low, left to right.

“The training helped,” she said.

Lindsey Olmstead, marina manager, said staff members go through fire extinguisher training with firefighters each year. A session was in late June and another on Thursday.

She said it’s paid off. There have been two other recent boat fires at the marina, both related to fuel issues.

"Our team was able to put out the boat fire with great speed — but also with great calmness," she said. "I am very proud of our team members — and also very grateful that our local fire department was able to teach our dockhands the skills they need to handle these emergencies as they arise."

Shane Rosenberg was at the marina Friday morning and could sense something in the air.

“I don't know if you’ve been around lightning before, but I felt all the hair sticking up on my body,” he said. “I knew it was coming.”

He saw a huge flash, stood up, and then stopped as thunder roared, seemingly on top of him.

He was still shaken hours later.

"It gets the heart going,” he said.

Ray Wardenaar said the storm was unusual.

“I’ve been here 30 years on this marina. I’ve never seen a lightning storm that close,” he said.

It was powerful.

"You could feel the explosion in the air," Wardenaar said.

Chad Wold was in his car at the marina on a conference call. The clap of thunder was so loud the people on the call thought he had been hit by a car.

“It was pretty nuts,” he said

Jennifer Weeks rushed to the marina after being told a boat at E dock was struck by lightning and was sinking.

Her family's boat was next to Relyea’s on E dock. The strike blew a small hole in the side of her boat, and fried the fuses.

She was relieved it wasn’t worse.

“It could have been under water,” she said.

When it was over, Elvidge was also relieved as he and his wife walked away.

“That’s about as close as you get to lightning without getting hit," he said.

BILL BULEY/Press

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Where does lightning strike the most in the US? This map breaks it down by county

Thunderstorms can develop at any time of year in the U.S., but they typically occur during the warmer months of spring, summer and fall. All types of thunderstorms carry one major threat: Lightning.

Warm air and humidity are the perfect ingredients for thunderstorms. You hear that rumble in the distance or a loud clap that sounds like a whip cracking. You can bet there's a thunderstorm brewing, and it's glowing with lightning.

About 242 million lightning flashes were recorded during 2023 in the U.S., according to a recent report by Vaisala Xweather , which tracks each stroke of lightning. That's the most in at least the past seven years, the company said.

Where lightning strikes: States with the highest lightning density

Last year, there were more lightning strikes in Texas overall last year, but Florida frequently has the highest lightning strike density in the U.S. – that's, more lightning strikes per square kilometer in the state.

Compared to the average for 2016–2022, the red areas on the map below experienced more lightning in 2023. Within the blue areas, lightning had less than average in 2023.

The National Lightning Detection Network finds that during the past six years, the U.S. averaged annually 23.4 million flashes , 55.5 million strokes (the visible bright, flickering light we see) and 36.8 million ground strike points .

Unable to view our graphics? Click here to see them. 

When lightning strikes: Top dates for total lightning strikes

Five of the top 10 lightning days in 2023 happened from June 14 to June 21 – when the Northern Hemisphere experienced its highest temperatures. The most intense lightning storms ranged from the edge of the Rockies, through the Middle Plains and to the Southeast. Large thunderstorms in the Northern Plains and eastern states also contributed.

Daily lightning strikes peaked in June

The peaks on the graphic below reflect storm systems moving across the country.

Summer is the most common time for lightning fatalities

According to the National Weather Service, lightning caused 13 deaths in the U.S. in 2023. That was down from 19 in 2022. From 2006 through 2021, lightning strikes killed 444 people (about 28 per year) in the U.S., according to the  Centers for Disease Control and Prevention .

How does lightning form?

Lightning is basically a huge, static electric shock inside a storm cloud. Storm clouds hold millions of tiny water droplets and ice crystals. The turbulent winds inside a cloud cause the droplets and crystals to bounce into each other and create a positive charge.

As they crash into each other, the droplets collide with other moisture. As the moisture rises, it condenses. This creates a negative charge in the lower portion of the cloud. Lightning flashes when there's a strong enough attraction between positive and negative charges.

Anatomy of a lightning stroke

A single bolt of lightning can heat the air around it to 54,000 degrees. Because of this high temperature, the air expands rapidly. The expansion generates a shock wave, which creates a booming sound wave, or thunder.

Ways to avoid becoming a victim of lightning

The  National Oceanic and Atmospheric Administration's motto  "When Thunder Roars, Go Indoors! " has helped countless people.

On average, 21 people are killed by lightning each year in the U.S., says John Jensenius, a meteorologist with the  National Lightning Safety Council. That's down from 2001 when the country averaged 55 per year. Most victims are struck in open areas, such as on beaches or golf courses, or when they take shelter from the rain under a tree.

Lightning can also be dangerous in your home. Here are some tips to reduce your risks:

CONTRIBUTING Doyle Rice/USA TODAY

SOURCE Vaisala Xweather Annual Lightning Report 2023, National Weather Service, Center for Science Education; AccuWeather, Centers for Disease Control and Prevention, The USA TODAY Weather Book

Thunderstorms expected to move through Maricopa County, but won't last long

Conditions were favorable through 6:30 p.m. Monday for the continued development of strong thunderstorms with gusty winds and small hail, the National Weather Service reported.

Tom Frieders, a meteorologist with the weather service in Phoenix, anticipated the storms would wind down by 7 p.m.

"The storms are winding down already," Frieders said at about 6:15 p.m. Monday. "Everything's weakening and moving out of the area already."

Winds in excess of 40 mph and half-inch hail would be possible with the strongest storms, the weather service said.

Locations to be impacted included Phoenix, Mesa, Chandler, Glendale, Scottsdale, Gilbert, Tempe, Apache Junction, Florence, Fountain Hills, Paradise Valley, Superior, east Mesa, Gold Canyon, Sugarloaf Mountain, New River, Ballantine Trailhead, Queen Creek, Cave Creek and Carefree.

This included highways Interstate 17 between mile markers 210 and 241; State Route 51 between mile markers 5 and 15; U.S. 60 between mile markers 176 and 231.

"Most areas should be clear for the rest of tonight," Frieders said.

For the latest watches and warnings, see our weather alert page .

Tips for driving in the rain

The Arizona Department of Transportation provided the following safety tips for driving in the rain :

• Inspect windshield wipers and replace them if necessary prior to expected rainfall.
• Turn on the headlights.
• Reduce speeds.
• Avoid sudden breaking on wet pavement.
• Create a "space cushion" between your vehicle and the vehicle in front of you.
• Avoid areas where water has pooled in travel lanes.

How to protect yourself from lightning strikes

Here are lightning safety tips from the National Weather Service:

• Pay attention to the weather. If you see big blue clouds, otherwise known as thunderheads, go inside. These types of clouds could mean a thunderstorm is coming.
• Get in a building with plumbing and wiring. If lightning strikes the building, the lightning will be conducted around and into the ground.
• Stay in your car. A vehicle will give you protection as electricity from lightning will pass through the vehicle's structure instead of hitting you.
• Get off open water. A boat out on the water is likely to be the most prominent object and you could be struck.
• Do not shower or bathe. If lightning hits your pipes, it could be conducted into the water in your bath or shower.
• Do not use electric appliances with plugs or cords. Wireless cellphones are OK, as are laptops that are connected to Wi-Fi but not plugged in.
• Follow the 30-30 rule. If you hear thunder within 30 seconds of a lightning bolt, that means the thunderstorm's distance is threatening. Wait at least 30 minutes after you hear the last thunder to go out. That gives the storm enough time to move away or dissipate.
• You don’t have to be near a storm to get struck. Lightning strikes can easily travel 10 miles or more. A record lightning flash in Oklahoma in 2007 traveled nearly 200 miles. Seek shelter if you hear thunder.
• Do not shelter under a tree. If lightning strikes the tree, the ground charge from the strike could travel into you.
• Don't huddle in a group. If you are outdoors with friends or family during a thunderstorm, don't all clump together. Keeping separation could reduce the number of people injured if lightning strikes.

This article was generated by The Arizona Republic and USA TODAY Network using data released by the National Weather Service. It was edited by a staff member.

Orange County beaches closed temporarily amid reports of lightning strikes

NEWPORT BEACH, Calif. (KABC) -- At least three beaches in Orange County were shut down temporarily Monday afternoon after reports of lightning strikes in the area.

Beach access and piers in Newport Beach, Seal Beach and Laguna Beach were closed until weather conditions cleared up. Seal Beach reopened just before 6:30 p.m.

The closures came as pockets of quick but intense storms popped up in spots throughout Southern California. The National Weather Service was issuing warnings about hail and thunderstorms throughout the region.

There were no immediate reports of injuries.

See full updated forecast here.

Related Topics

• ORANGE COUNTY
• NEWPORT BEACH
• LAGUNA BEACH

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Guishard chose to take home the one-time cash option of $571,000 before taxes.

It appeared lightning struck twice for this Smithfield woman – it wasn’t the first time she’d won big in the lottery.

She also won $100,000 in 2021.

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Eight dead after South Korean tanker capsizes off Japan

Coastguard says chemical tanker was carrying 980 tonnes of acrylic acid but no leaks reported

Eight people died after a South Korean-flagged tanker capsized in rough seas off Japan, the coastguard said.

“They were confirmed dead at a hospital,” a spokesperson told AFP on Wednesday. One other person was in a non-life-threatening condition while two others remained missing.

The coastguard had said previously that nine people were rescued from the stricken ship but gave no indication of their condition.

The chemicals tanker had 11 people onboard, including two South Koreans, eight Indonesians and one Chinese, the coastguard said.

The tanker was carrying 980 tonnes of acrylic acid, but there were no leaks reported, Japan’s Kyodo news agency reported, citing the coastguard.

Footage from the Japanese broadcaster NHK earlier showed the overturned red hull of the ship as well as a life raft, as a coastguard ship negotiated heavy waves and a helicopter flew overhead.

The ship had been at anchor due to rough weather near the island of Mutsure, off Japan’s south-western coast not far from Kitakyushu port.

With waves as high as 3.5 metres (11ft), the crew notified the coastguard early on Wednesday that the vessel was tilting and requested help, NHK said.

The Japan Coast Guard received the rescue call shortly after 7am (22:00 GMT on Tuesday) saying that the ship was “tilting, please help us”, the spokesperson said.

NHK named the vessel as the Keoyoung Sun, which the specialist website VesselFinder said was a chemical and oil products tanker built in 1996, measuring 69 metres (226ft) in length.

The ship’s operator declined to comment.

Japan was being buffeted by strong winds on Wednesday with high waves and heavy snow forecast, especially along mountainous areas.

Gusts of up to 126km (78 miles) an hour were expected in several areas, NHK reported, with winds intensifying, mainly in western and eastern Japan owing to a low pressure system.

The Meteorological Agency warned people to be alert for gusty winds, high waves, heavy snow and even lightning strikes and tornadoes.

South Korea’s foreign ministry said it had dispatched an embassy official to the site and was in “close communication with related organisations”.

Earlier this month, a South Korean fishing boat carrying nine crew, including seven Indonesians, capsized off the country’s southern coast, leaving six missing.

The South Korean president, Yoon Suk Yeol, had ordered the relevant authorities to “do their best to save lives by mobilising all available personnel and equipment, including navy and fishing boats”, his office said in a statement.

The Yonhap news agency said patrol boats, navy vessels, and aircraft had been deployed for the continuing search efforts.

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Plant material on obsidian blades on Rapa Nui suggests settlers there visited South America and returned

by Bob Yirka , Phys.org

A team of archaeologists affiliated with several institutions in Chile reports evidence that early settlers on the island of Rapa Nui sailed to South America, interacted with people living there and then returned. In their study , published in PLOS ONE , the group analyzed plant material found on obsidian blades made by the early settlers.

Prior research has shown that there were people living on Rapa Nui during the years 1000 to 1300, though their origin is still not known—those early settlers are most famous for their giant stone carvings of human figures.

In this new study, the research team found evidence that some of the settlers sailed all the way to the coast of South America and back. Such a voyage would have entailed sailing one way for 3,700 kilometers and likely would have taken anywhere from one to two months, depending on the weather.

Prior research has found that the oral history of the Rapu Nui people includes reports of at least one trip made by the early settlers to South America. In this new effort, the research team followed up on such reports by digging up and studying obsidian blades at a site called Anakena, the earliest known settlement on the island. The researchers found very small amounts of plant material on the blades, evidence that they were used to process plant-based food.

An analysis of the plant material showed evidence of cassava , breadfruit, purple yam, taro, achira, ginger and the Tahitian apple. Of those, the Tahitian apple and breadfruit stood out because neither grows naturally on Rapa Nui—and ginger had never been seen before in remote parts of Oceania.

Cassava, sweet potato and achira stood out for a different reason—all three are South American foods. They also noted that the sweet potato remnants were found in the deepest parts of the dig site , suggesting that they arrived on the island during the early years of the settlement.

The researchers conclude that early Rapu Nui settlers ventured to South America and back, perhaps several times. They further suggest that some of the food they brought back with them was planted and used to grow crops over the ensuing years.

Journal information: PLoS ONE

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Climate change and boat strikes are killing right whales. Stricter speed limits could help them

• Emily Jones, Grist

This story was originally published by Grist . Sign up for Grist’s weekly newsletter here .

Amid a difficult year for North Atlantic right whales, a proposed rule to help protect them is one step closer to reality.

Earlier this month, a proposal to expand speed limits for boats — one of the leading causes of death for the endangered whales — took a key step forward: It’s now under review by the White House Office of Information and Regulatory Affairs, the last stage of federal review.

Fewer than 360 of the whales remain; only about 70 of them are females of reproductive age. Every individual whale is considered vital to the species’ survival, but since 2017 right whales have been experiencing what scientists call an “unusual mortality event,” during which 39 whales have died.

Human actions — including climate change — are killing them.

When the cause of a right whale’s death can be determined, it is most often a strike by a boat or entanglement in fishing gear. Three young whales have been found dead this year, two of them with wounds from boat strikes and the third entangled in gear. One of the whales killed by a boat was a calf just a few months old.

Climate change, meanwhile, has disrupted their food supply , driving down right whale birth rates and pushing them into territories without rules in place to protect them.

“Our impacts are so great right now that the risk of extinction is very real,” said Jessica Redfern, associate vice president of ocean conservation at the New England Aquarium. “To be able to save the species, we have to stop our direct human-caused impacts on the population.”

This is not the first time humans have driven North Atlantic right whales to the brink of extinction .

Their name comes from whaling: They were known as the “right” whale to hunt because they spend time relatively close to coastlines, often swimming slowly and near the surface, and they float when dead. They also yielded large amounts of the oil and baleen whalers were after. So humans hunted them to near extinction until it was banned in 1935.

Many of those same characteristics are what make right whales so vulnerable to human-caused dangers today. Because they’re often near the surface in the same waters frequented by fishing boats, harbor pilots, and shipping vessels headed into port, it’s easy for boats to collide with them.

“They’ve been called an urban whale,” said Redfern. “They swim in waters that humans are using; they have high overlap with humans.”

To reduce the risk of vessel strikes, ships over 65 feet long have to slow down during set times of year when the whales are likely to be around. In the southeastern U.S., the speed limits are in force during the winter when the whales are calving; off the New England coast, the restrictions are in place in the spring and summer when they’re feeding. Regulators can also declare voluntary speed restrictions in localized spots if whales are seen, known as dynamic management areas.

The National Oceanic and Atmospheric Administration, or NOAA, in 2022 proposed expanding those restrictions in three ways.

First, the new rule would cover larger geographical areas. The protection zones would extend down the coast from Massachusetts to Florida at various times of year, instead of only applying in certain distinct areas.

Second, the change would apply the speed limits to smaller craft like fishing boats, rather than only ships over 65 feet.

Third, the new rule would make the speed restrictions — the temporary speed limits where whales have been spotted — in dynamic management areas mandatory.

Since NOAA published and gathered feedback on the proposed rule in 2022, whale advocates have been clamoring for the agency to implement it. Those calls have increased in recent months as dead right whales have washed up on beaches.

“There have been three deaths, and that has been really devastating this year, and two of them are related to vessel strikes,” said Redfern. “It’s just highlighted that absolute urgency, the necessity of getting this rule out.”

A leading boating industry group is speaking out against the expanded speed restrictions, arguing they could hurt small businesses in the recreational boating industry.

“We are extremely disappointed and alarmed to see this economically catastrophic and deeply flawed rule proceed to these final stages,” said Frank Hugelmeyer, president and CEO of the National Marine Manufacturers Association, in a statement. “The proposed rule is based on incorrect assumptions and questionable data, and fails to distinguish between large, ocean-crossing vessels and small recreational boats.”

Right whale scientists have documented in recent years that small, recreational boats can injure and kill right whales. At least four of the lethal vessel strikes since the current restrictions began in 2008 have involved boats smaller than 65 feet and thus not subject to that speed limit, according to Redfern.

NOAA estimated that, based on the size and placement of the propeller wounds, the boat that killed the months-old calf this year was between 35 and 57 feet in length — too small to fall under the existing speed restrictions, but subject to the new rule if it were to be implemented.

In his statement, Hugelmeyer also pointed to new marine technologies aimed at detecting right whales in the water to reduce vessel strikes without expanding the speed rules.

Scientists like Redfern remain skeptical, though.

The tech “offers a lot of promise,” she said, but the speed limits are proven.

“It’s really important, I think, that we rigorously evaluate the technology that’s proposed to make sure that it is going to achieve the same type of risk reduction that we see with the slowdowns in expanded areas,” she said.

Many groups, meanwhile, have raised concerns that offshore wind turbines could harm whales. There is no evidence of that, according to NOAA.

This article originally appeared in Grist ,  a nonprofit, independent media organization dedicated to telling stories of climate solutions and a just future. Learn more at Grist.org

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