Lightning strikes on power boats?

[tuffr2]

I have been at different boats types including catamarans and sailboats. What I would like to know do boats w/o that tall metal mast get struck by lightning?

If not, do power boat people anchor near sailboats?



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[colemj]

They get struck just like any other short object near taller ones (houses, people, the ground itself). We saw one power boat surrounded by sailboats take a direct strike.

Mark

[GordMay]

Yes, boats w/o that tall metal mast can & do get struck by lightning.

Excerpted from Dr. Ewen Thomson’s excellent website:

“The principles for effective lightning protection on smaller boats are the same as those for larger boats. That is, form an ExoTerminalTM system. Grounding terminals and interconnections around the perimeter shield the region inside, while attachment conductors (air terminals), also around the perimeter, attract the strike point away from the boat's interior. Superstructure such as a metal-framed bimini, metal outriggers, and metal cabin framing act in a similar fashion to the metal rigging of a sailboat. They can be incorporated into a lightning protection system to act as air terminals and form part of the conducting cage. Some, but not a lot, of modifications are in order. Consider the typical fisherman. While there is usually a lot of deck-top metal, not all of it is above head height, which is an obvious problem. For example, a wraparound bow rail is in the optimum place to be used as part of the system but knee-high is nowhere near high enough to attract the strike that precious few feet away from a deck hand. We are presently developing a solution to this – a lightning rod that attaches to the bow rail but that can easily be laid flat for docking, etc. While this does not guarantee the safety of the deckhand, it considerably skews the odds in his or her favor. Other techniques such as overhead catenary wires can skew the odds even more. In the absence of connections to a good grounding system, however, this same metal superstructure becomes instead an electrical hazard since it acts as a launching pad for uncontrolled sparks. Also, to minimize the shock risk to the helmsman, the engine and steering controls should be bonded to the lightning protection system to ensure that everyone floats at the same potential. The grounding system on any boat should comprise multiple grounding terminals that include at least one square foot of immersed area. For the immersed area, outboard and stern drives can be used, or additional grounding strips can be added. SiedarcTM electrodes complete the grounding network. How many electrodes and where they are best placed depends on the individual boat. However, some locations are no-brainers, such as directly below each outrigger on a fisherman. Owing to the proximity of the lightning attachment point to occupants, even the best possible lightning protection system still presents an extreme risk on a small boat so that there can be no guarantees. A lightning protection system hence should be regarded as a good insurance policy that could just save your life. “

“An ocean-going power yacht has more risk factors than any other type of boat. Large open deck spaces with an absence of natural lightning rods raise the risk of a direct attachment to anyone on deck. Any on-deck spa or pool further increases the odds of electrocution since a wet human body is more likely to conduct a lethal current than a dry one. Without adequate air terminals, at least upward-going streamers, and possibly direct lightning attachment, is likely for elevated transducers such as antennas, radar, and weather sensors. The natural path to ground in this case is then via on-board wiring through the main instrumentation cluster, likely destroying most other electronic systems as well. This may include electronic control systems for steering and engines that are much more susceptible to lightning damage than manual ones. Hence mechanical redundancy is crucial. In-built conductors such as water in tanks, carbon fiber reinforcing, metallic fittings, and power plants are all potential sources for sideflashes, perhaps through crew, passengers or the hull. As with cruising sailboats, there are many immersed conductors that may be incorporated into the grounding network but doing so raises the risk of corrosion and their grounding effectiveness is compromised if the surfaces are painted or covered with fiberglass. Our proprietary grounding technology is designed to fix this problem. Passagemakers do also have some advantages. Extensive weather sensing capabilities can be supplemented with thunderstorm and lightning sensors to warn the crew of electrical hazards. Also, extensive metallic superstructure and handrails on the periphery of the vessel are already in the ideal location to form part of the external conducting shield that we call the ExoTerminalTM grounding system. Just add air terminals, six SiedarcTM electrodes, one square foot of immersed ground strips, surge suppressors for antennas, and interconnections, and a superior lightning protection system is the result. Sample installations are available for a Mirage Great Harbour Pilothouse and a Nordhavn 55. “

➥ Marine Lightning Protection Inc.

➥ Science & Technology

[Cottontop]

BoatUS Marine Insurance has a good article:

Striking Lightning Facts - Seaworthy Magazine - BoatUS

Which include the following chart:

Table 1. The probability of a lightning
strike by type of boat, 2003–2013

Type of Boat Chances per 1,000
Multihull Sailboat 6.9
Monohull Sailboat 3.8
Trawler/Motoryacht 1.5
All – Overall Average 0.9
Bass Boat, Runabout, Pontoon Boat. 0.1

[tuffr2]

Cottontop - thanks, this is data I can use as part of my decision making process. I will be moving to Florida's east coast within a year.

Again ...thanks

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