lightning sailboat review

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• Sailboat Guide

Lightning is a 18 ′ 11 ″ / 5.8 m monohull sailboat designed by Sparkman & Stephens and built by Nickels Boat Works, Inc., Skaneateles Boat & Canoe Co., Helms - Jack A. Helms Co., Siddons & Sindle, Lippincott Boat Works, J.J. Taylor and Sons Ltd., Lockley Newport Boats, Eichenlaub Boat Co., Mobjack Manufacturing Corp., Clark Boat Company, Allen Boat Co., and Loftland Sail-craft Inc. starting in 1938.

• 2 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 3 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 4 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 5 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 6 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 7 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View
• 8 / 8 Charlotte, NC, US 1982 Lightning $4,500 USD View

Rig and Sails

Auxilary power, accomodations, calculations.

The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.

Classic hull speed formula:

Hull Speed = 1.34 x √LWL

Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio .311 Hull Speed = Max Speed/Length ratio x √LWL

Sail Area / Displacement Ratio

A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.

SA/D = SA ÷ (D ÷ 64) 2/3

• SA : Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
• D : Displacement in pounds.

Ballast / Displacement Ratio

A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.

Ballast / Displacement * 100

Displacement / Length Ratio

A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.

D/L = (D ÷ 2240) ÷ (0.01 x LWL)³

• D: Displacement of the boat in pounds.
• LWL: Waterline length in feet

Comfort Ratio

This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.

Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam 1.33 )

• D: Displacement of the boat in pounds
• LOA: Length overall in feet
• Beam: Width of boat at the widest point in feet

Capsize Screening Formula

This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.

CSV = Beam ÷ ³√(D / 64)

One of the most popular one-design classes in the US since the 1940’s. But fleets also exist in other parts of the world. Although originally designed for wood planked construction, nearly all boats since the early 1960’s have been built of fiberglass. Ballast above is max weight of centerboard.

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International Lightning Class Association

Class contact information.

Click below

Class Email

Class Website

One-Design Class Type: Dinghy

Was this boat built to be sailed by youth or adults? Both

Approximately how many class members do you have? 1600

Photo Credit:Douglas Wake

Photo Credit: Art Petrosemolo

About International Lightning Class Association

The Lightning truly excels as an affordable racing boat. The rig is simple but offers sophisticated sail shape controls. The hull features a unique hard chine design that combines the stability that provides sail-carrying power, with flat bottom sections that promote planing. At 700 pounds all up, the trailerable centerboard sloop is tough enough to avoid frequent breakdowns, but light enough to plane wildly on the reaches. Membership is diverse with sailors aged 8 to 80+. Many families sail together at top events and it is common to see females make up at least 40% of competitors.

The Lightning is sailed in more than thirteen countries and in the Pan American Games. A World, Master World and Youth World Championships are held every two years. North American, South American and European Championships are held each year as are innumerable regional and District championships. Major regattas attract some of the finest sailors in the world, but you find Class members friendly and the sailmakers’ complete tuning guides helpful at getting you up to speed in a hurry.

The International Lightning Class Association is one of the oldest and best organized class associations in sailboat racing. Its primary purpose is to serve its membership, preserve the integrity of the Lightning and provide high-quality competitive events. In addition, the Lightning Class publishes monthly e-blasts and a quarterly newsletter Flashes with up-to-date regatta news, boat brokerage and ideas on how to get the most out of your Lightning. The professionally managed association and dedicated volunteers are always on hand to assist both current and potential members.

If you’re looking for a boat you can be proud to sail, one that offers dinghy handling with the performance of a sport boat, a refined design that’s free of fads, complete with the technology of today for both racing and day sailing – look at the Lightning.

Boats Produced: 15630+

Class boat builder(s):

Allen Boat Company, Buffalo, NY: https://www.allenboatco.com/

WindRider International: https://www.windrider.com/

Approximately how many boats are in the USA/North America? 11,000+

Where is your One-Design class typically sailed in the USA? List regions of the country:

East of the Mississippi, Mid-West, Texas, Denver, San Diego, Pacific Northwest Click Here for Fleet Finder Map: https://www.lightningclass.org/content.aspx?page_id=451&club_id=93488

Does this class have a spinnaker or gennaker? Yes

How many people sail as a crew including the helm?  3

Ideal combined weight of range of crew:  490

Boat Designed in  1938

Length (feet/inches): 19’0″

Beam: 6’6″

Weight of rigged boat without sails: 700 lbs

Draft: (board down): 4’11”, (board up): 5″

Mast Height: 26’2″

Back to One-Design Central

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About the DN Iceboat

The Lightning offers a combination of performance and stability that eludes most one-designs. The Lightning’s hard chine and 130 lb centerboard give her the stability and power of a small keel boat going to weather in strong winds and allow her to carry a very large spinnaker for breathtaking off wind rides. The Lightning’s rig is simple, but offers sophisticated sail shape controls. 

Our 19-foot trailerable centerboard sloop has evolved into one of the most popular and competitive one-design racing classes in the world. Awarded ISAF International Class status, the Lightning is sailed in more than 13 countries and in the Pan American Games, and the class provides a professionally-managed association that is among the largest in all of one-design sailing. 

If you’re looking for a boat you can be proud to sail, one that offers dinghy handling with the performance of a sportboat, a refined design that’s free of fads, complete with the technology of today for both racing and daysailing – Get The Best Of Both Worlds. Get into a Lightning.

Class Information:

Class Contact:  Laura Jeffers, Executive Secretary

Class Contact Email:   [email protected]

Class Contact Phone:   727-942-7969

Class Website:   lightningclass.org

Social Media:   Facebook  |  Twitter  |  Instagram  |  Youtube  

Class Specs

LOA:  19 ft. 

Beam:  6 ft. 6 in. 

Draft:  4 ft. 11 in. 

Weight:  700 lbs. 

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Blue Jays, and Lightnings, and Lasers, Oh My

There must be a couple of hundred small sailboats available new or used that would serve just fine on any Maine lake. In this issue, we narrow the choices down to just three: the Blue Jay, the Lightning, and the Laser. 

Lightnings and Blue Jays—like Stars and Comets, Indians and Town Class, Thistles and International 14s—could be considered size variations on a theme. Both are Sparkman & Stephens designs, and Blue Jays are often referred to as “baby Lightnings.” Back in the heyday of one-design sailing, this mama and baby sailboat theme was common.

Blue Jays have an emotional connection for me. My twin brother and I built our first boat, a Blue Jay, at the age of 14 in our family’s garage. Back in the day, before one-designs were all popped out of a mold, each with a white hull and a colored deck, a youngster’s first boat was a unique and treasured thing, more so of course if he and his brother built it themselves.

Blue Jays were inspired by Drake Sparkman and designed by his firm, Sparkman & Stephens. The former chair of his yacht club’s junior sailing program, Sparkman intended the boats to be used to teach sailing. Accordingly, Blue Jays feature a complete sloop rig with a mainsail, jib, and spinnaker. This setup provided the essential lines for two children to learn how to trim and coordinate sails. The boats, which have roomy open cockpits and no seats, can easily hold three kids or two adults. 

The original design (1947) called for the boats to be easily built with readily available quarter-inch-thick plywood (the plans are still available from the International Blue Jay Class Association). A fiberglass version became available in the 1960s.

At 13'6" long with a draft of just 6 inches—or 4 feet with the centerboard down—the Blue Jay makes a great lake boat. Small and light, these boats can be trailered behind any old car, kept on a mooring, pulled up on the beach or just tied up at the dock. The small sail plan is manageable by kids of average size and limited strength, but in a strong wind this flattish-bottomed box still can get up and plane. It can capsize, too—although that takes a fair amount of effort. When you are just 14 or so, if the water is midsummer warm, capsizing just adds to the fun.

Now that I’m fully grown, it is easy for me to rig a Blue Jay on Lake Megunticook and sail it alone. Given my history with these boats, an afternoon sail in a Blue Jay is a special pleasure. The beauty of this design is that anybody can delight in the Blue Jay’s lively maneuverability, the enjoyment of hiking hard and making the boat point and go to windward. When I pull the centerboard halfway up, hike out hard, and hear those staccato little pulsations reverberating up from the cutwater, I’m buff, I’m young, and I’m ineffably happy.

While the Blue Jay’s centerboard is made of common plywood or laminated wood, the centerboard of its mama Lightning is galvanized or stainless-steel plate, only 3/8 of an inch thick. This metal board helps make the boat a little more stable. It also happens to be a good choice for rocky Maine lakes because it can bash into a rock without expensive damage. The thin centerboard has minimal resistance at high speed, allowing a Lightning to plane in good winds almost any time the spinnaker is up. 

Modern fiberglass Lightnings are low maintenance. They are usually fitted with side ballast chambers or buoyancy bags so they can, with lots of grunting and groaning, be re-righted after capsizing by a crew of three. It helps to have some clothing or rags to stuff into the top of the centerboard trunk, and a nearby powerboat can be helpful. The fact is that I have sailed my buddy’s Lightning all around Panther Pond, just him and me, in all kinds of wind, and never had any trouble. 

There are many high-tech expensive dinghies that can sail circles around a Lightning, but for me, when I sail a Lightning on a lake and heel her over displaying the flashy varnished seats and ribs and floorboards to lakeshore dwellers, I feel like John Beresford Tipton cruising downtown in his Duesenberg Touring Car. 

The design was perfect in terms of performance, and also perfect in simplicity: The easy-to-build hull mated to the easy-to-build deck lid by means of a cleverly turned-down edge. The one slipped over the other and all that was needed to mate the parts together was a little bit of goo. (One might say it was a goo-ed idea!) Over 200,000 of these hulls have been manufactured and they can be found all over the world.

The Laser mast is just a round aluminum tube, or actually a pair of tubes that fit together. The single sail slips down over this pole before it is stepped, and since the sleeve rotates around with the sail, it’s all very aerodynamic. This is far easier and way less prone to trouble than you might imagine. In most any other boat you would have a halyard. But the Laser flips over and unflips with ease. If a thunderstorm looms, instead of dropping the sail you can intentionally capsize for a spell. The boat floats high and visible, becoming one huge life preserver. 

Laser hulls are light enough (130 pounds) that one person can easily drag it back and forth from the shore to beach or woods. I owned a Laser at one time and by myself could haul it off the top of my car, where it customarily lived. I was a lot younger then….

If you get really good at sailing a Laser, you can qualify to compete in the Olympics. There is a somewhat smaller mast and sail combo available and whole gaggles of thusly-rigged Lasers form a separate official class, the Laser “Radial.” This is a great equalizer for the light and the small of stature.

But all that is racing stuff, and what I really wanted to emphasize is that there probably isn’t a boat in the whole world that is as much fun to just sail as a Laser. That’s what I’m talking about!

Flitting around at high speed on a windy blue day on a whitecapped Maine lake, your eyes just inches above the water. Some people can even gybe without catching the mainsheet under the corner of the transom! Not me—not always. But who cares?

We are on a lake, it’s midsummer, it’s hot, and a periodic dunking just washes off the sweat. 

Contributing Author Art Paine is a boat designer, fine artist, freelance writer, aesthete, and photographer who lives in Bernard, Maine.

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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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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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Yachting Monthly

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Sailing in lightning: how to keep your yacht safe

• In partnership with Katy Stickland
• July 22, 2022

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

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

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

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

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

However, high currents passing through resistive conductors generate heat.

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

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

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

Wherever you sail, lightning needs to be taken seriously.

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

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

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

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

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

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

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

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

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

Preventing damage when sailing in lightning

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

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

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

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

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

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

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

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

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

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

Rolling ball concept

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

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

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

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

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

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

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

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

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

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

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

Continues below…

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

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

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

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

Protection classes

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

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

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

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

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

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

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

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

The external LPS

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

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

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

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

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

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

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

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

VHF antennas are commonly destroyed in a lightning strike.

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

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

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

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

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

Down conductors

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

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

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

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

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

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

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

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

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

Grounding terminal

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

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

A grounding terminal must be submerged under all operating conditions.

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

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

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

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

Metal through-hulls do not meet this requirement.

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

Propellers and radio ground plates

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

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

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

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

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

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

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

Internal lightning protection

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

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

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

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

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

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

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

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

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

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

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

We do not need three separate conductors.

Electronic Device Protection

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

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

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

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

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

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

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

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

Most SPDs are designed for AC circuits.

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

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

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

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

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

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

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

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

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

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

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

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

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

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A Brief History of the Lightning

Part i — the origins of the idea.

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Buying a boat that was hit by lightning?

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Would you even consider buying a boat hit by lightning? Last week I looked at a 2007 Catalina 309 (almost new, unlike my 30 year old current boat). It is in great shape- a very clean well-maintained boat. But it was hit by lightning a year and a half ago. As a result, all the electronics have been replaced (with top of the line stuff) as well as a new master AC/DC panel, new batteries, battery charger, alternator, all running lights, new frig, radios, bilge pumps, etc. There are no noticeable pinholes, scorch marks, or damage around thru-hulls -- at least to my non-expert eye. I've asked the broker for the insurance survey that would have been done after the strike. I've also asked about whether the boat has been sailed since then. (Yes, with one long trip from MA to Maine). The asking price is not super low, but definitely lower than comparables without a doubt -- especially when you add all the new gear. What do you think? Investigate further (i.e. make an offer and hire a surveyor as normal) or should possible lingering "ghosts" and damage make me run away  

Investigate further with a surveyor. I might even try to get a copy of the last survey.  

I agree that you want to the original insurance survey, so that your surveyor can inspect everything that was in it. The result can go either way. New electronics could be a nice find or the boat could have prettied up delamination.  

Missawaka, As an Electronics tech and lake sailer, I'm no expert on the hull damage, but if the electronics has been replaced, I would crawl around and inspect the ground system on everything electric. Looking for fried connections etc. They are all hooked together somewhere. If the strike wasn't very direct, there may not be anymore damage. good luck Dan  

I agree with everything above. Oour boat was an indirect lightning strike last summer and now has all new elctronics as you described. There was no damage to the hull and the rig. So look at what the insurance said...especially with a surveyor and the fact that the lightening strike was disclosed is a good thing. Dave  

I've been involved with a few lightning struck boats have have seen panels and electronics replaced but no one ever wants to replace all the conductors becuase the cost is extreme. If there was enough juice to fry a panel what did it do the the conductors under the liner ? You may not find out for a few years .... or maybe tomorrow. As to effects on the structure I think I'd want a clean bill of health from a certified thermographer with marine experience to tell me that the laminate under the new gelcoat patches is sound. Buying any boat involves risk, Buying a lightning struck boat is a much bigger risk and at the very least I'd be looking for a very substantial discount.  

Something to consider... A nearby lightning strike will generate a large magnetic field. If you look at this link go down about half way and there is an easy to understand picture of the "right hand grip rule". The "I" in that figure is current and in the case we care about here, I is the lighting bolt current itself. That magnetic field propagates with field lines as shown in that figure and if the transient field encounters conductors (orientation is important), current is generated in the conductor. This could include DC or AC wires in the boat and even circuit board traces in electronics. The currents generated can be much lower than what would damage a wire from heat but high enough to damage sensitive electronic nodes such as on the circuit board itself. So you can't assume there would be any conductor damage even if all the electronics were fried. I would guess (could be wrong) that in most cases of an indirect strike, the conductors are just fine.  

60 million volts and 60 thousand amps travelling at near the speed of light. You pays your money and you takes your chances. I know which way I'd bet.  

Thanks for the replies. In the past few days, I've had a chance to talk to the head of the yard that worked on the boat (it is a very reputable yard). He personally inspected the boat with the insurance rep, and oversaw the work. He sent me (with permission of the owner) a five page, seemingly exhaustive list/bill of all work done, as well as the initial inspection report. According to him, the strike came down a stay and out through the shore cord (the boat was docked obviously). it then went into the power system of the docks and damaged other boats as well. According to his report, there was no hull damage to the boat (not surprising if the bolt travelled as he says), all wiring leading to and from all replaced items was replaced, including conductors that were affected. That's on top of all the equipment replaced, the alternator, the board, all mast electronics, all navigational electronics, batteries, plugs, bilge pumps, rudder sensors etc. According to the boat yard, the present owner then sailed 3 more weeks at the end of that summer after the repairs were done and then for another seven weeks (including one long trip) the next summer. Of course it is possible that the boat yard is working with the selling broker in some way (they are in different towns, but not far away). But I have no real reason to think that. So I'm slightly closer to pulling the trigger and going for an offer/survey. Anything else I should explore?  

So, Philo, did you buy the lightning-struck boat? If so, how have things gone? Do you regret purchasing the boat? We are looking at a late-model lightning-struck boat. Supposedly insurance paid for all repairs needed. Just wondering about others' experiences. Thanks for taking a moment to fill us in on the late-breaking details.  

jslinder, welcome aboard. Unfortunately, this forum changed software recently and is doing something to serve up old threads to new, less familiar, members. The thread above was written 8 years ago. The dates are at the top of each post. If you click on the original poster's name, you'll see their last activity was about a month later and hasn't been back since. I think you need 10 posts to start your own thread on the subject, where you could give the details of what you're looking at. I think all the same above advice will apply. Hope it works out for you, or you find something else soon.  

I appreciate your thoughtful reply. I do not consider myself to be a “new, less familiar” member. As you can see, I have been a member since 2013. I have been a member long enuff to know that people often hang around for many years, and will often respond to queries made on threads that have been inactive for a number of years. It was worth a try to me to give it a shot with Philo. Sorry if that was inconvenient or confusing for you.  

jslindner said: Sorry if that was inconvenient or confusing for you. Click to expand...

That's what a surveyor is for, but in this case, I'd probably hire two, who didn't know each other or about each other and deduct the cost of at least one from the asking price. Boatpoker is a professional surveyor, so I'd be inclined to take his posts very seriously,and I'm with him 100% about that boat being seriously reduced enough to even think of making a deal. Just think about all those cars salvaged from hurricane Katrina, refurbished superficially, but still cars that were underwater for some time. At what price would you knowingly buy one?  

Damn, got me again. Zombie thread.....  

No zombie post. I appreciated your contribution. Found it helpful. Thank you.  

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