[Valiente]

I have heard that physically undoing the coax and the power to the VHF/SSB will help, if you have time. This obviously goes for anything: physically break the circuit and don't think a switch will suffice.

I have seen lightning actually hitting a moored boat (a new Hunter 42, FWIW) at our club. After I stopped blinking from the sheer brightness of the event (about 200 metres away), I could see a column of brown smoke hanging in the air. This was the remains left over from vapourized windex and weather station, plus bits of the mast's top plate. When we took our Zodiac over to check out the boat, we saw a series of dime- to quarter-sized, burnt holes punched out of the hull just above the waterline on the starboard bow.

These were taped out with duct tape and the boat was able to start its engine and go to a yard for repair (new mast and glass work). I heard from a boat fix-it guy that there was no other damage to the electrics: the boat started perfectly and the voltage that didn't blow up the mast top simply shot out the bow, far from metallic bits. It was a brand-new boat, as well...owned for two weeks.

This underlined for me that you can do the sensible things listed here, but that lightning will exit wherever it feels like doing so, and there's not a lot you can do about that except to avoid putting your tongue on the stays while standing in bare feet on a salt-water-drenched deck.

On the upside, I know two guys who were club racing their boats and got hit, and both survived with only minor issues.

 

[sailingdog]

The reason lightning does so much damage is that it creates a very high voltage differential as it passes through the boat. That creates a voltage differential across various electronic components internally, regardless of whether the equipment is plugged in, live, or disconnected. That is what does in most of the electronics.

IIRC, the reason disconnecting the COAX from the VHF is that reduces the length of the potential inductor, making the equipment less likely to get fried.

The reason putting electronics into the pressure cooker works is that the solid metal barrier of the pot and lid-which are in solid contact with each other if the pressure cooker has the gasket in and is locked closed-forms a faraday cage that the inductive forces are shunted around-protecting the pressure cooker's contents. This is very similar to the protective effect that most cars offer in a thunderstorm-since most cars form a fairly solid metal cage around their passengers.

Thanks Sailing dog I wont worry in future. I thought the large gap formed when the main battery switches are off may have been enough to encourage the high voltage to seek an alternative path rather than go via my expensive electronics at least with a nearby rather than direct hit. Hopefully Inside an aluminium boat the electronics receive a little protection from the induced voltage if a strike travels via the hull.
At least your advice saves me getting up in the night to turn off the battery switches.

 

[brokesailor]

We had a lightning strike hit just above a makeshift mast we had rigged on a Swan 48 using a spinnaker pole after we had been dismasted in a storm a few days earlier on a crossing from Saint Martin to Newport. Got to see Saint Elmo's Fire. Even though when it happened it scared the living crap out of me, now looking back it was very cool.

 

[Bene505]

Thanks for all the posts. I guess I'll put the handheld in a pot with a lid (don't have a pressure cooker), and put the pot in the microwave. Oh, and maybe wrap the handheld in aluminum foil for good measure.

It sure would be good to have a working VHF and GPS after the strike. Or rather, after the storm had gone by.

 

[Winderlust]

Note to self:

Keep tongue of shrouds during electrical storm. Good tip; thanks Val

 

[pdqaltair]

True, except fingers of the metal lid are pressed against the edge of the pot ...

Doesn't the gasket seal prevent electrical conductivity between the lid and base? This would make it a poor Faraday cage.

... to hold the lid on. There is solid metal-to-metal contact with a very small gap.

The trouble with the microwave is that I would surely forget and turn it on a few hours later!

 

[GaryHLucas]

A better option for protecting small electronics is your pressure cooker. It forms a well-sealed faraday cage, thanks to the pressure gasket seal. A refrigerator, depending on what it is made of, may not be a good faraday cage. A microwave oven is probably less protective than a pressure cooker, since they're not solid metal all the way around.

Of course the chamber of a microwave is DESIGNED to contain microwaves, so why do you think it wouldn't keep out electrical charges?

 

[sailingdog]

Microwaves and lightning are two different beasties...and I'd rather rely on a solid stainless steel pressure cooker than a microwave oven.

Of course, I don't have a microwave oven on my boat, and wouldn't if you paid me...just take the money and use it for something more useful for a sailboat, rather than a floating condo. :laugher

Of course the chamber of a microwave is DESIGNED to contain microwaves, so why do you think it wouldn't keep out electrical charges?

 

[boatpoker]

Valiente: that boat you saw struck by lightning was (after a protracted fight) written off and sold as salvage. A yachtbroker bought it, de-registered it, changed the name then licensed it and sold it. As it was de-registered there is now no way to trace it unless you know the HIN. Lovely huh !

 

[camaraderie]

Just to be clear...a microwave oven forms a VERY GOOD Farraday cage and the item does not require further insulation from the cage as it would if you put it in a pot or cooker. The interior of a marine oven is also a good place but the window makes it imperfect to a further enclusure in a pot/cooker should be used.

 

[TSOJOURNER]

thanks everyone

 

[artbyjody]

The ******* way of avoiding damage is to put loops in your associated cables / wires. The loop itself acts as a semi Faraday and shreds upon over expected current - breaking the flow of conductive paths.

Little do most know - a surge protector is about useless - when you have a lighting strike - the current jumps and you have to give some means to disrupt such. A fuse is not likely to be blown until after the fact.

Simple knots where you coil the wire within itself - is most effective - you lose the wire because it explodes but less likely to see you electronics fry from it. ******* it may be - but a tried and proven way of actual isolation...

 

[Valiente]

Valiente: that boat you saw struck by lightning was (after a protracted fight) written off and sold as salvage. A yachtbroker bought it, de-registered it, changed the name then licensed it and sold it. As it was de-registered there is now no way to trace it unless you know the HIN. Lovely huh !

That's quite an interesting story. Why was it written off? The external damage looked pretty easily repairable, but I never saw the interior, just heard about it, and saw the boat heading to Bristol Marine (I think) a few days later under its own power.

And as to the de-registering trick, I can believe it. Both my boat purchases have been private with surveyors brought in.

 

[Winderlust]

I can't think of a better response to my OP than the Kathy Barron forum post of 4-07-2005 "lightning Strike". I'm just getting used to this SailNet stuff. I should have looked at the "Similar Threads".

 

[Winderlust]

Sh****; also Don Casey's article "Gear and Maintenance" 08/09/2004. very good stuff! Both attached to this thread. Good work Sailnet!!!

 

[Winderlust]

Why is this statement wrong:

"There is a lesson to be learned here. Don't flatter yourself that you can be a cosmic player: lightning doesn't know you exist, and it doesn't care. The way to deal with lightning is just to stay out of the way. On a sailboat, staying out of the way primarily means giving the lightning an unimpeded path to ground."

from Don Casey.

 

[camaraderie]

The statement is wrong only in the fact that given an unimpeded path to ground (which helps), lightning will often choose an impeded path to ground! You just can't trust it to stay on the road you give it.

 

[sailingdog]

Cam's right-lightning often does some very strange stuff... and it has trouble figuring out what we want it to do...after all, it only lives for all of a couple of milliseconds...and isn't all that smart, regardless of how bright it may appear to be.

There was a girl in NH that was recently hit by lightning and the thing that probably saved her life was a nose ring piercing. LINK You can't make this stuff up...

The statement is wrong only in the fact that given an unimpeded path to ground (which helps), lightning will often choose an impeded path to ground! You just can't trust it to stay on the road you give it.

 

[waltsn]

Not related to the original posters question.. but..

At my job, we test consumer electronics intended to be operated in an outdoor environment for lightning tolerance. Any wires or cables into or out of some device will generate current/voltage from the lightning produced electromagnetic pulse. I.e., the wires or cables to some extent act as an antenna. To test this (proving that we meet a spec), we have a big ol lightning simulator which is capable of about 7K volts with fixed low impedance (as low as 25 ohms) and a waveform similar to a lightning strike. We feed this directly into the input of the device (for example, this might be the 12 volt wires into a radio or a cable RF input). Our customer has a spec for the product and the spec has been adjusted over the years based on field returns. I.e., if they were getting too high of return for lightning damage, they would increase the spec. As the spec went up, we made the product more robust. This mostly involves semiconductor voltage clamps called "transorbs" on any input with a cable or wires. As the spec goes up, we just have to put in transorbs which can handle higher power and also make sure the signal path which gets the charge to the transorb can handle things. Note that the transorbs will allow a fairly high very fast voltage to occur (like in our case, 40 volts) even though the electronics wont tolerate this for longer periods of time. We do see a correlation with the lightning protection spec level and field returns.

So most consumer electronics could be made better survive a lightning strike but it adds cost and in general, the manufacture has no good reason to do this (unless they are getting a lot of returns because of lightning damage). Disconnecting wires where they enter electronics will help because this for the most part cuts off the energy source into the electronics. Putting some piece of electronics in a faraday cage with the wires still attached may have no benefit.

 

[Valiente]

Interesting perspective. Thanks.