Marine Lightning Protection Inc.

Latest news July 10 , 2008

Annapolis boat shows We are considering a visit to Annapolis from Oct 13-20 and may be available to meet with anyone interested in putting our system on their new yacht. Please email Ewen to set up an appointment or to get details about his seminar on Oct 15.

Airboats These craft are particularly hazardous. See the details on our new Airboats page.

Protect a Boat Like a Building The October 2007 edition of Boat US's Exchange explains this novel concept. See the article here. This concept has been incorporated into the new National Fire Protection Association Lightning Protection Standard NFPA780-2008, which is now available. The watercraft section is Chapter 8.

Latest projects
Nordhavn 55 (completed September 2007)	Tag Young 60' sail cat (system parts delivered November 2007)
Mirage Great Harbour N37 (completed March 2008)	Domino 20 60' power cat (system parts delivered January 2008)
Big Mama 60' fisherman (system parts delivered January 2008)	Outbound 46 sailing monohull (completed June 2008)
Maxi77 (completed July 2008)

The catamaran below was not one of our projects. It shows that all it takes is a spark from lightning to turn a beautiful yacht into a smoldering hulk. With our exoterminal^TM system we transform the interior into a shielded equipotential zone and keep the sparks outside the boat. Since catamarans get struck twice as often as monohulls, we now have a new page devoted just to them.

Aftermath of lightning strike to Moorings 46' cat in Abacos, 7am June 20, 2008. Fortunately there were no injuries. Photos by Eric Kraft

Innovative lightning protection

Peer-reviewed science forms the basis

Our approach to lightning protection is based solidly on observation and scientific theory.  The foundation was established in a paper published in 1991 in the prestigious IEEE Transactions of Electromagnetic Compatibility. As a result of this paper, subsequent renditions of standards published by ABYC and NFPA upgraded their recommended sizes for down conductors from #8AWG to #4AWG and noted that a ground strip is a more effective grounding conductor than a square plate of the same area.

Another fundamental problem revealed in this scientific work was that a one square foot ground plate is "hopelessly inadequate" to prevent sideflashes in fresh water. This was not addressed in these earlier standard rewrites since, at the time, there was no obvious solution. We can now solve this problem with our patented Siedarc^TM electrodes that, when distributed around the hull, provide the multiple exit points needed for effective grounding.

More recently, we have worked with the NFPA 780 technical committee to establish a new standard based on these new ideas, that is now published as Chapter 8 in the 2008 edition of NFPA780

. This standard is based on the simple concept that a boat should be protected the same as a building, with the lightning conductors on the outside rather than through the middle of the boat.

As the ground attachment path for a 5-mile long spark carrying tens of kiloamperes, the protection system has the task of safely diverting this current around crew, sensitive electronics, and hull components.  However, even when the current is flowing in the water, voltage differences can cause sideflashes, both inside the boat and between the boat and the water. These present a shock hazard to the crew, produce overvoltage in electronics systems, and can blast holes through the hull.

Management of the sideflash problem is the fundamental issue in the design of an effective marine lightning protection system. See our Grounding Concepts page for a technical explanation of the underlying concepts and suggestions as to how these can be applied to a protection system.

Sideflash prevention is the problem

An interesting feature of hull damage is the tendency for sideflashes to form around about the waterline.  Apparently either the water surface or the waterline itself causes charges to accumulate, usually on internal conducting fittings, and initiate sparks through the hull.  The effect is more pronounced in fresh water than salt.

Photo by Dave Edwards

In lightning protection circles, the conventional solution to a problem such as this is to add conductors where the damage is observed. In the above case this means placing lightning conductors through the hull at the waterline. Since it is impractical to install multiple ground plates in a hull, we developed the Siedarc^TM electrode to provide the necessary exit terminals. This is effectively an air terminal near the water. In fact, each one is designed to the same specification as a lightning air terminal.

In order to investigate the effectiveness of this concept, we tested an electrode with a 10kV generator for both salt and fresh water at Kennick Inc. in St. Petersburg. Even though 10kV is much lower than what would be expected during a lightning strike, we obtained results that clearly indicated the promising potential for the method and further elucidated the best mode of operation. Specifically, in the photo below, with the electrode about 1/4 "above the surface of salt water, a spark of about 15" in diameter was produced. Clearly the sparking is contained very close to the water surface, perhaps even above it, showing the importance of the surface for current dissipation.

In fresh water, the spark connected all the way to the sides of the container, about 12" away. In contrast, when the electrode tip was immersed just below the water surface, a small (~¹/₂") glow was observed but no sparks. The conclusion is that an electrode can generate a spark that is orders of magnitude longer than the spark gap in air when placed above the water surface. Hence the optimum placement is just above the water surface.

The ExoTerminal^TM system is the answer

Providing exit terminals around the perimeter of the hull is the key to an effective system design since, in addition to dispersing the current more uniformly around the boat, it also enables the lightning down conductors to be routed externally to all wiring and conducting fittings. This is illustrated for a sailboat below. The lightning conductor from mast base connects to both the chainplate and the loop before passing down to a daisy-chain Siedarc^TM electrode just above the waterline, and from there via an immersed HStrip^TM to a keelbolt (and base of a keel-stepped mast). Siedarc^TM electrodes at bow and stern provide more exit terminals from the loop to the water. This geometry is mirrored on the port side, as indicated by the dashed lines. That is, there is total of two HStrips and six Siedarc^TM electrodes. Thus a conducting grid covers the interior of the boat and a total of eight exit terminals are distributed over the hull near the waterline. For a keel-stepped mast, make another connection from the mast base to the keelbolt of HStrips.

Guiding the current on the outside rather than through the middle of the boat minimizes shock risk and emi.  In addition, a bonding loop around the boat at about deck level equalizes potentials, provides additional paths for current flow, and can be used for bonding conducting fittings. In a major departure from the status quo, NFPA (the National Fire Protection Association) has recently revised their watercraft standard (NFPA 780 Ch.8) to include the concepts of a loop conductor, external down conductors, and perimeter grounding electrodes. See our Standards page for details. With this new system the conductor layout more closely mirrors that found on the typical lightning protection system on a building. For a graphic demonstration of the shielding effectiveness of a metallic cage, check out this photo sequence from the Boston Museum of Science. We call this system of external lightning conductors and peripheral exit terminals the ExoTerminal^TM protection system.

In the case of a powerboat, the external down conductors can be connected directly to air terminals that are around the perimeter. Placed using the rolling sphere model, these can be much shorter than a single air terminal that covers the whole boat using the "cone of protection" concept.  The annotated photo below shows our first system on a passagemaker that was installed during manufacture. The lightning conductors (the blue lines) are on the inside of the hull and the only features that might stand out as different are the two air terminals at the rear of the bridge deck.

Lightning protection system on Mirage Great Harbor 47 John Henry

We can provide all of the components needed in a marine lightning protection system.

Component	Product	Description
Air terminals	RMAT^TM	Rod with rail-mount ratchet base
	SMAT^TM	Rod with surface-mount ratchet base
	Rod	Aluminum or tinned copper rod with threaded base
Connections	StanCon^TM	Through-connector for stanchion
	MastCon^TM	Connector for aluminum mast base to either aluminum or copper conductors
	GapCon^TM	Tinned copper connector with air gap for galvanic isolation
	Lug	Heavy duty tinned copper closed-end lugs for cable terminations
	HStripCon^TM	Inboard coupling for combining two HStrips into a single one square foot area
Conductors	Strip	Aluminum or tinned copper strip for main conductors
	Cable	Insulated tinned copper cable
Grounding	HStrip^TM	0.5 ft^2 tinned solid copper grounding strip
	Siedarc^TM	Spark-promoting grounding electrodes embedded in non-conducting through-hulls

General information on these items and their integration into a lightning protection system can be found on the History/Problems/Solutions page, and specific details on these pages:

Item	Document	Contents
Siedarc^TM	Introduction	Introduction to the Siedarc^TM electrode line
	Grounding guidelines	General guidelines for using Siedarc^TM electrodes
	Grounding concepts	Physical basis for grounding electrode placement and type
	Prices	Product price list
Grounding strips	Information	Problems, solutions & applications for immersed grounding strips
	Specifications	Brief specifications of HStrip^TM grounding strips and accessories
	Prices	Product price list

We also offer consulting services for:

· analysis and recommendations for specific systems;

· expert witness testimony concerning any aspect of lightning on or near water.

Please call or email if you have any questions.

Marine Lightning Protection Inc. Phone: +1 352 3733485  Email: info@marinelightning.com URL: www.marinelightning.com

Copyright Marine lightning Protection 2007

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