Lightning Strikes And How To Prepare

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We’ve been fascinated by–and worried about–lightning strikes onboard since we saw the aftermath of a strike on an almost-new yacht in New Guinea. It  had a piece of hull blown out below the waterline and lost most of its electronics/electrical gear.

This is not an easy subject to discuss, and there are many different opinions on preparedness. What follows are our thoughts after more than a few years of inquiry and observation. It is certainly not expert advice! We suspect that amongst our SetSail family there exists more specialized know-how, and we invite comments to educate us all on this subject.

Here is what we think we know:

  • Lightning is unpredictable, and any rules may or may not apply depending on how the lightning strike occurs, and how strong it is.
  • Static dissipators may or may not work. Lots of scientific debate on this. They don’t seem to hurt.
  • It pays to have a sextant, almanac, and paper charts just in case. We know of one yacht that had all their hand held devices, GPS and VHF included, taken out by a hit.
  • There may be some benefit to wrapping backup parts in tin foil, carrying same in a metal box, or ideally, inside of a microwave oven.
  • Lightning does not like to turn corners. Bonding plates should be directly below mast(s), not offset with a piece of bonding wire between the bonding plate and mast heel.
  • Metal through-hull fittings must be properly bonded to nearby shrouds, and to the rest of the underwater items (keel, engine, etc).
  • Metal fittings on deck–lifeline stanchions, winches, sail tracks–should be bonded together and to the rest of the system. In other words, any metal on a fiberglass yacht will have the same potential to avoid side flashes.
  • Ideally electronics will be easily disconnected in risky situations. We are told that complete disconnection, not just a switch, is best.
  • Antennae are often the entry path for lightning. There are arrestors which will in theory take a lightening strikes of moderate magnitude to the vessel’s grounding system.
  • When we had our fiberglass 50 footer, we used battery cable hose-clamped to each cap shroud and the back stay and trailed in the water, as a ground path. It was never tested by a strike.
  • Metal boats are supposed to be safer than fiberglass in that they bleed the static charge buildup and so attract less activity. They also are supposed to be a giant “Faraday cage” and protect the inhabitant and equipment.
  • A major lightning strike will take out all sorts of electrical/electronic items (see link below).

What we do these days:

  • Now that we have the emergency immediate pilot control system, the lazy pilot is left disconnected. A third pilot is wrapped in tin foil in the basement.
  • We do carry a sextant, charts, and current almanac, just in case.
  • In lightning storms we disconnect the three computers on board from all wires.


And now a reference which you may or may not want to read. The vessel just off our bow in the photo above, Sheer Madness, took a major hit a year ago. They went through a long and arduous task recovering therefrom, and have written a very detailed account which you can read here.

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Meanwhile, we have a lightning trigger for the camera and are looking forward to some new photos of this fascinating, if scary, phenomenon.

Okay SetSailors, the ball is in your court. Suggestions for reducing or avoiding damage, and firsthand accounts, would be much appreciated by all.

Posted by Steve Dashew  (August 20, 2012)

19 Responses to “Lightning Strikes And How To Prepare”

  1. Bill Says:

    I suggest reading Ewen Thompson of Gainsville FL website


  2. Stan Creighton Says:

    We are in Costa Rica this summer on our boat, so this is an issue we marvel at almost everyday now. Do you think the latest generation EPIRB’s are like any other device on the boat and subject to being taken out in a strike? We currently have one mounted on a rail and one in the ditch bag.


  3. Steve Dashew Says:

    Definitely a possibility if the strike is big enough. Probably the best safeguard is a spare microwave oven, with the mission critical stuff stored therein.

  4. Sid Fisher Says:

    I remember a 40 ft traditional sailing vessel coming into port having been struck by lightning 60 miles out. ALL electronics were blown but the hull was fine probably because of the fact that her wire rigging with bottlescrews was setup directly to long metal chainplates the lower ends on the leeward side being below the waterline. Thus a direct path to ground.

    Not so many years ago I was surveying a 2 year old yacht 60ft designed by a leading Dutch designer. This vessel had a revolving carbonfibre mast (Aero rig) and at first I was pleased to see the heavy lightning conductor UNTIL I had the sole boards removed when I saw numerous right angle bends in the conductor before it reached the grounding plate.
    Steve is absolutel right, lightning does not like to turn corners! A strike on this vessel would likely have blown out the bottom of the boat
    This is a specialist subject about which even top yards are likely to have little practical experience.

  5. Matt Mills Says:

    Hi Steve, I was wondering about lightning and grounding systems on the 97. Are there any special considerations with regard to the huge solar array on that beautiful boat? What happens to a solar panel and all the others and associated systems connected to it in the unlikely event of a lightning strike?

    PS. Your site is on my daily reading list. Thanks for sharing it.

  6. Steve Dashew Says:

    No special precautions for the solar panels. However, since they do have diodes odds are they would get toasted with a major strike.

  7. Sam Block Says:

    We took 2 shots, both in North Carolina, but in different years. The first I witnessed while running back to our slip to make the mentioned disconnects. The shot hit an alloy sloop on the opposite finger pier; went down the stick, on to the lifelines, and departed horizontally off his davits. We took the shot thru our davits frying the chips in the radar, autopilot, and oddly the AC control switches. The other shot, again while dockside, came down the neighbors stick and took us thru the prop shaft. We took a third shot in the Gulf of Panama, but that happens to everybody.

  8. Steve Dashew Says:

    Sounds like you need to make a sacrifice to the appropriate gods! Or, choose your neighbors more carefully. Where are you these days?

  9. Sam Block Says:

    Lucy and I own a big rig and drive for FedEx. We run hard for 8 months then kick back on ‘Knockabout’ our Banjer 37. We’ve been with FedEx since the kids graduated from college (Gerry – Columbia & Kate – Penn). We downsized from the H-R 49 and do the winter months in the Bahamas aboard our Dutch double ender. Big Kudos for all you do! Sam and Lucy

  10. George Frazier Says:

    Sam & Lucy,
    I (have a) guy who is living with me trading his labor for my roof and food has done a lot of sailing (4 times across the Atlantic). I thought of you and wondered how your doing. Read your post and glad to see you are still sailing. I remember that first trip out of Fort Lauderdale. You have come a long way from there.
    I am living in Baltimore and just completing a house for myself near the water. Fells Point if you have been in town.

  11. Mike Parker Says:

    Hi Steve,
    In answer to your question, we put some lightning arrestors on Avatar (FPB#1). They are on the HF and VHF radio coax and are mounted on metal plate screwed to the metal hull at the entry point (the wet locker). It can’t hurt, but there is no warranty. You can see a selection of parts at
    There are other paths from above deck into the boat such as the wiring for lights, controls on the flying bridge, radar, etc. that are not protected. If there is a nearby strike, it is possible that induced currents onto these wires will damage the attached equipment, but retrofitting lightning protection onto every wire is just too difficult. Carol and I came home one day to find that lightning had struck a tree in the yard and induced currents had damaged several pieces of computer equipment attached to our house’s wired Ethernet system and also the microwave oven that was plugged into AC power.

    If there is a direct strike, I just hope the un-protected wires will arc to the metal boat or act like a fuse before the full strength of the lightning gets inside the boat. As we have discussed before, I feel that lightning arrestors will not give good protection against direct strikes. So we keep spare parts (like the engine computer) and hope that most of the damage is in a non-critical area. Living in a metal cage makes me feel safer, and I try to keep away from things that might become the lightning’s favored path. So even though the radio’s coax is bonded to the metal at the entry point and has a lightning arrestor, I try to avoid radio use during a lightning storm, etc.

    I will close with an interesting statistic from our friend “Mike the Strike” who makes a living from lightning. In his safety talk, he points out that lightning is sexist. In every country in the entire world, many more males are killed by lightning than females, especially young males. In the USA the males are killed 4.6 times as often as females. Basically they tend to be doing things outside during lightning storms. Look at for some good advice, and check the picture of the dead cows near a fence. They were not hit by a direct strike.

    Well I hear thunder, so I am going to turn off my computer that is attached to wires and start using my wireless iPad 🙂

  12. Keith Jacob Says:

    If lightning decides to jump 1500feet out of the sky, turning off a switch or disconnecting a cable will have no effect. The electromagnetic pulse alone can cause as many problems with electronics, even from 1000’s of feet away from a strike.

  13. Patrick S Lasswell Says:

    A slightly better preserving system for keeping electronics intact is to put things in a coffee can with a foil piece held down by the plastic lid. A good preserving system would use a small (or if you have the room, full 50 gallon) steel drum with a steel bracket holding the lid closed. Inside the steel drum I’d put the electronics in Pelican cases, because if you’re in a lightning storm, the strike is probably not the end of your excitement. If the lightning gets through the steel drum Faraday cage and Pelican case insulation to destroy your electronics, you might consider the possibility that God hates you. I’m pretty sure you could take cheap consumer electronics, put them in a Pelican case inside a steel drum and they would shrug a direct strike.

  14. Steve Dunbar Says:

    I’d suggest surplus military ammo cans – US government issue type – for storage. We have been using them whitewater rafting and they are the only containers that stay reliably dry through flips in big rapids. They are easy to get into in a hurry and available in several sizes. I have not tried them with lightning but they are all metal and should isolate the contents.

  15. Steve Dashew Says:

    Excellent idea! We’ll get a couple for ourselves even though we have a giant Faraday cage in the metal hull of Wind Horse.

  16. Steve Dunbar Says:

    We use the smaller .50 cal for day boxes left accessible for cameras, cell phones, etc.

    The larger 20 mm or rocket boxes will swallow a laptop and accessories. The best way to get them is from army navy stores since it can be worth looking at the gasket on the lid.

  17. dominomarie Says:

    As always, a lively discussion when it comes to lightning. DOMINO got hit in the San Blas 3 months ago. In the same week, 6 other boats got hit. We sustained a direct hit through the VHF antenna that we had mounted (our big error) higher than our top lightning rod. The lightning system (Ewen Thomson’s) discharged most of the energy through the ground plates and sidearc electrodes. However, some of the energy went through the antenna, to ground, and backed up the negative and blew a great part of our electronics. We are rebuilding, trying to learn and improve. We are shortening the VHF antenna. We are also putting arrestors on all vital circuits to handle the excess surge. Considering installing grounded dispersers (Forespar “wire brush”) to disperse static electricity (as you say, they are not shown to hurt anything, are all over the Maltese Falcon), carry extra gear stowed in foil, and have built a Faraday Cage all around our electronics cabinet as an extra layer of protection for our electronic “brains” – It’s witch science and physics, but as a 65′ power catamaran, we are more at risk than most sailing monohulls out-there. We take lightning seriously. It will happen to us again, it’s only a matter of time.

  18. dan catalyst Says:

    I found a simple solution, lightning never strikes the same place twice so i bought a boat that was struck by lightning once already so ill never have to worry about it happening again,haha.

  19. dan catalyst Says:

    * boats name was ‘great white’at the time and strike happened during the 1978(ish) mini-tonner nationals held in tampa,fl knocked out electronics and mast and all rigging scraped. there were spirals burnt into the topsides where the lines were coiled. salty wet lines conduct electricity better than aluminum it seems. mast, boomand rigging were changed due to possible issues. if any metal parts were heated up very hot by the strike,then the heat treating would be compromised and aluminum that could have been heated that hot can never be trusted.