Electrifying lightning strike report

jeremyshaw

jeremyshaw

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Two interesting things strike me about this lightning strike report I got from friends in the US yesterday. Here's the report:

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best of all, we managed to dodge some really bad thunderstorms - 2” hail, 70 knots of wind, until, the day after we were hauled at Tidewater in Port Covington, Baltimore, when our luck ran out and we took a direct lightning hit to the top of the mast. God must have been really mad that day as a 140 year old church was also hit and burned to the ground. We are fortunate to be able to tell the tale as we were on board when the lightning struck with a blinding flash and very loud bang. It blew the VHF antenna and the masthead tricolor light to smithereens; killed all the electronics which weren’t por table or small enough to fit in the stove (our improvised Faraday cage); scorched the genoa and welded the furler blade; and another nasty surprise awaited when the storm passed and we went off the boat, there was a hole in the starboard bow and a crater in the ground below.
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The interesting things are:

1. It shows the Faraday cage idea of putting stuff in the oven really works, even with a major strike like this. I've always done it, but more in faith than certainty.

2. I'm curious as to whether the hole in the bow would have got blown if she had been in the water. This boat is a cat so would likely have been on wooden blocks with just a couple of front and back support props on each hull. I suspect the lightning was unable to ground easily and therefore went through the hull to take the shortest path.

Any views on whether this boat, if in the water in this situation, would have still got a hole in the hull? I think not but I can't really argue the case well...
 
Must be a Cat thing this week. Two days ago I went to see a yacht just a couple of hours after a big storm had passed over. Whilst there the company techies were busy refitting a new autohelm controller on the Cat as it had received a strike during the storm. Unlucky for the cat, but maybe lucky for me as the boat I was viewing was ok (moored just 30m away), first thing I did was ask for the Navigation gear to be swithched on and checked.

(Yes I am going to have a full survey done anyway, with particular attention to all things electric)
 
I am not so sure about the Faraday Cage theory or more specifically the need to put things in the oven.
I suspect that the real damage from lightning strikes comes form the electronic gear being connected to mast head gear and then other gear being connected to the gear connected to the mast.
If gear is connected to the mast top then it and its wiring can become an alternative current path to ground.

In other words I am wondering if simply disconnecting all cables to electronics would not provide enough protection.

If the boat were in the water we might find an adequate low resistance path from the mast to the water. I can imagine multiple paths via wiring and engine prop shaft to water or simply via damp fibreglass and mast stay wires. This might mean more distributed damage or may lessen the whole damage by distribution of current path. I guess it is all academic but a bit frightening.
Note that if the current goes through the stay wires they will get hot and almost certainly lose their temper (heat treatment) so should be replaced if not already melted. This is because they have quite a significant electrical resistance.

The obvious question is... can it happen to me and how can I minimise the damage. I think from what I have read that a very heavy cable from mast base to the metal keel or an earth plate of at least 2 square feet contact with the water would be valuable in the case of a strike. And of course disconnect your electronics (and put in the oven if you want) One thing for sure some parts of USA get a lot of lightning compared to others. olewill
 
[ QUOTE ]
I am not so sure about the Faraday Cage theory or more specifically the need to put things in the oven.

[/ QUOTE ]

Are you suggesting Mike was wrong and most of my time working in an expensive cage repairing RF gear was a waste of time, or, are you questioning the use of a Faraday cage during a lightening storm; even though the original poster stated the electronics not placed into the oven were ruined?

I can explain the theory behind Faraday cages, but can't help with the evidence presented as I was not there.
 
A common path of destruction for lightening damage is the negative cables, as most switches only switch the positive side and all the negativesd are permenantly connected together. That said lightening is of course more than capable of jumping straight thru switches whther they are on or off.

I saw a yacht that had thought it had got away with a lightening strike, till it was pulled out shortly afterwards to find major cracking / crazing centered around the thru hull fittings.

If you are near a lightening storm then at very least worth unplugging whatever you can, starting with the VHF aerial. No guarentee that it will be saved, but stands more chance if not connected.

Anthony
 
High Dogwatch no I think I understand the theory of the Farady cage.

What I was suggesting is that the real benefit was in disconnecting the items rather than actually putting them in the oven. Or put another way sailors who don't have an oven should disconnect items anyway for possibly the same benefit. Possibly being the operative word.

Or I was hoping to get more comment on the benefit of farraday cage.
thanks olewill
 
I've been in the middle of a very intense lightning storm. Being a little powerboat, no oven or faraday cage type affair. I disconnected everything I could. If I had an oven to put things in, I would have done. The psychological element is probably as important as the physical.
 
I reckon it's having equipment disconnected and physically separate from the boat's wiring system that saves it rather than putting it in a Faraday cage. I suspect removing your lecky stuff and putting it in your butty box would work just as well. Anyone want to test my theory? I'll give you joint authorship on the subsequent paper. /forums/images/graemlins/grin.gif
 
[ QUOTE ]
I've been in the middle of a very intense lightning storm. Being a little powerboat, no oven or faraday cage type affair. I disconnected everything I could. If I had an oven to put things in, I would have done. The psychological element is probably as important as the physical.

[/ QUOTE ]

Return trip across Baltic ... about 10nm before entrance to farosund- Gotland. Had an extremely harrowing experience ... electrical storm that seemed to be all around us .. being about midnight - it was dark and scary ..

At first it seemed to be ahead of us and we moving slowly - all apperaed to be OK and we could just quietly job along following behind .. but then it just changed ... the lightning instead of being on the horizon ahead - cracked astern then odd ones to either side of us ... but major still well ahead ..

I made the other guy go below - my thoughts being that it was not necessary for both of us to be at risk ... as to electrics / electronics - to be honest plain didn't enter my mind - I was too afraid and wound up with what was happening around us ...

It didn't help that rain was also coming down ... so all was electrically conductive - including me !! plus a 8m mast sticking up like a beacon saying Hit me !!

The whole episode lasted about 5 hours ... and I can honestly say that it was not something I wish to repeat ...

On another occasion ... on a ship - we were moored to the mid-river buoys in Port Harcourt Nigeria ... I was off watch and doing some work on the bridge ... the 3 wives we had on board were standing at accommodation side at the rail looking ashore ... BHAM ! We were hit by a single large bolt ... apparently it hit the mast head...... the VHF antena was burnt to a crisp ...

The main VHf box on the bulkhead - it was an older Sailor model with the large wall box .. the board melted and flowed out the vent at base ... staining the wall !
The whole accoms was lit up in total like a massive St. Elmos fire ... the wives were fine - but after their hair was standing up on end !! and they were struck dumb in shock !! For minutes after all they could do was splutter and try to speak ...

Lightning ... after those two incidents ... not funny !!
 
There was a boat moored on the Hamble which got struck by lightning last year. All the electrics got fried, including things like the handheld VHF and GPS which were stored in a locker or in the chart table.

I also remember a race a few years back when a fellow competitor said his electronics got knocked out by a nearby strike, but were OK once he had switched them off and then on again. Our foredeck crew said afterwards that she got a jolt off the spinnaker pole when we gybed, even though we had been nowhere near any lightning.
 
Years ago, I read a detailed report of an investigation into the destruction of electronic equipment, that was disconnected, during a storm. The damage was caused by the huge magnetic field, created by the lightening. This caused large, secondary voltages in the circuits.

So, if you have a Faraday cage, it would be wise to use it.

I once saw a large blue flame rise from a church that had just been struck by lightening. Probably St. Elmos fire.

Philip
 
[ QUOTE ]
I suspect removing your lecky stuff and putting it in your butty box would work just as well.

[/ QUOTE ] Done exactly that twice now as we have no oven on board. It was a Ryvita tin though, not a plastic butty box.

A small tin can take HH VHF, HHGPS and satphone if you have one, so it is probably worth having on board. It can also be used as a biscuit tin once the storm has passed.

Thdere are plenty of reports of unconnected HH electronics being fried in a lightning strike, so I think a Faraday cage is a good idea.

- W
 
During thunderstorms, the ground has an opposite charge to the cloud. A pointed conductor triggers the connection between the earth and cloud earlier than a flat topped conductor.

This was the conclusion of research carried out in the not too distant past, and reported on TV.

Philip
 
Fascinating subject this, with an equally fascinating number of contradictory answers! First of all, a lightning strike can induce quite substantial voltages in any metal object nearby. I have read accounts of crew getting shocks from metal fittings during a lightning storm, with the advice that crew wear rubber gloves, wellies etc, and followed by the advice to put a rubber object such as a welly or a condom over the masthead.....

Certainly any object with a spike will help a 'leader' to form, which is the first stage on ground of the formation of a lightning stroke.

The Faraday Cage is the best way of preserving electronics, and can be any metal container. Even a metal mesh works apparently, as it prevents the magnetic charge from inducing heavy currents in sensitive electronics. Disconnecting things doesn't seem to make a lot of difference, though is a good idea to help reduce damage.

I suppose the ultimate Faraday Cage afloat is a steel hulled yacht? They do appear to survive lightning strike much more effectively.

I have to admit that at the first growl of thunder the old adrenalin starts pumping, for all the reasons SBC mentions, and a few others. One of the few things that really will keep me off the water!
 
I sent a link re this thread to a singlehanded sailing friend in England who was hit by lightning off Brazil a few years ago - he enjoyed reading through all the posts above, but was reluctant to sign up as a newbie just in order to post an account of what happened to the boat (and him) in this case.
He is still suffering physical side effects today as a result of that lightning strike.
Soooo, I asked if he would like to send me a copy of his thoughts, and he did just that - they are copied below :

Electrical equipment stored in the boat is often zapped even though it's completely isolated in its boxes, but wrapping it in cooking foil is very effective.
Electronics grounded to ship's "earth", but switched OFF, are usually destroyed, but things actually switched ON at the time may survive maybe because the positive and the negative lines BOTH go to the same extreme voltages briefly, preserving the correct 12 volts across the equipment.

The really daft thing is that although the steel rigging of the ship acts as a primitive but moderately effective Faraday cage of sorts most of the time, we promptly nullify all its effect by sticking a VHF antenna straight out into the clear at the masthead.
Keeping the aerial INSIDE the rigging, and giving the lightning an easier path to the sea directly from the rigging itself (NOT through skin fittings inside the ship) considerably lessens the damage done inside.

An American friend was struck at sea in the Gulf of Mexico, and had previously thought he was safe because every one of the skin fittings had been bonded together to the mast stays .. in his case ALL the skin fittings abandoned ship at the same instant, and he was extremely lucky to be picked up out of the water by a fishing boat next day. The pepper-potted yacht had gone down pretty quickly, as you can imagine.

Many people seem to forget that these massive voltages don't behave like ordinary DC voltages.
The instant extreme charge flashes over the OUTSIDE of things if it can, and not necessarily through the middle.
So it seems a good idea to offer it an easy route.
You won't stop it, but maybe you can minimise the damage. Best would be
(i) have a steel or aluminium boat with a VHF antenna mounted lower than usual, and
(ii) be somewhere else.

You don't have to be physically struck by the lightning either....... a near miss up to 80 metres away can still cause all sorts of destructive stray voltages.
One yacht lost all three spare GPS's, almost certainly in this manner.
This would be totally prevented by the cooking foil trick, again.

In my own case we have eventually surmised the following :-

(i) I was very lucky indeed, even though I was actually holding the HF microphone at the time (warning my brother in England that I was going to switch off because of the oncoming storm).
(ii) The masthead VHF aerial was the prime entry point into the ship (not the HF antenna, to which I was directly connected by holding the microphone).
(iii) I was very hot and sweaty and wearing nothing at the time (sweltering heat in the Tropics) so I had a good conducting surface over the outside of me,
(iv) The rain was pouring torrentially, giving a fair conductive track from rigging to the sea.
(v) I was physically super fit at the time, which statistically means the heart is less likely to be stopped by the shock, apparently.

I was UNlucky to have my head right by the lightning's main entry point into the cabin (the VHF coax), which is why I got damaged personally.
 
your friends account has a part that certainly agrees with my observation of the ships incident in Nigeria ... the lightning appeared to "envelope" the whole ship in a display of sparkling light shower .. as though it was making path round the vessel to the water.
Also that the ships lighning entry point was same - the VHF antena sticking up from top of mast !
 
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