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.
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.