Lightning: things to do that limit damage

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Jamesuk

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Hi,

I have been involved with a lightning discharge and since I am totally and justifiably OTT about it.

It just started to rain here I jumped up and turned everything off flick all the breakers and disconnect from
Shore power.

Is there anything you do or do you simply look out of your boat and say ahh that mast is taller or ahh there is a catamaran so he will be the bait and so do nothing ?

Thanks

Ideally I would like to disconnect all Raymarine and stuff rubber sockets in them to prevent the jump.
 
Jamesuk said:
Hi,

I have been involved with a lightning discharge and since I am totally and justifiably OTT about it.

It just started to rain here I jumped up and turned everything off flick all the breakers and disconnect from
Shore power.

Is there anything you do or do you simply look out of your boat and say ahh that mast is taller or ahh there is a catamaran so he will be the bait and so do nothing ?

Thanks

Ideally I would like to disconnect all Raymarine and stuff rubber sockets in them to prevent the jump.
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Have a beer & relax
 
Remove all electrical equipment outside and inside the boat - VHF, FM/AM radio, log, depth sounder, GPS, DVD player if you have those and anything else. Then put them in the oven which is Faraday cage. You will still get burnt wiring and sometimes a scorched ensign if it's on the back stay.

The closest we came to a strike was on passage from Grenada to Mustique. The lightning hit the water about 30 yards in front of the boat and we had crackling Elmos fire in the rigging which was impressive but no damage. It was the loudest bang we've ever heard.
 
KellysEye said:
Remove all electrical equipment outside and inside the boat - VHF, FM/AM radio, log, depth sounder, GPS, DVD player if you have those and anything else. Then put them in the oven which is Faraday cage.
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This idea keeps cropping up, and it's wrong on two counts. Firstly, any oven with a glass door is not a Faraday Cage. Secondly, even if it was a Faraday cage, that only means that it stops external electrical fields from penetrating. It does nothong for magnetic fields which are what induce unpleasantly destructive currents in electronics. There may be advantages to putting stuff in the oven, but Faraday cageness ain't one of them.
 
I tend to ponder whether or not the thumping great cable connecting my mast to my keel might serve any useful purpose.... whilst hoping to remain ignorant of the facts.

That said, the amount of lightning we seem to have sailed in this year and not been struck gives me hope that we never will find out.
 
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sailorman said:
It will depend where one sails & the occurrence of violent storms.
were not all world circumnavigate`s OV :ambivalence:
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That's true, but I don't think lightning bolts pick and choose where to strike you. Nearest I've ever been to being hit by lightning was just west of Portland Bill.
 
Simondjuk said:
I tend to ponder whether or not the thumping great cable connecting my mast to my keel might serve any useful purpose.... whilst hoping to remain ignorant of the facts.

That said, the amount of lightning we seem to have sailed in this year and not been struck gives me hope that we never will find out.
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IMHO that thumping great cable mast to keel is your best protection. Just liek copper strips down from a rod ona church steeple. It will hopefully conduct current from the mast a very good conductor (assuming ali) to the seawater.
The lower he resistance of this cable then the less tendency there will be for current to flow through other wiring to alternative ground (seawater). Try to avert current going through stainless steel stay wires, these have a higher resistance and will get hot with any current and so lose temper and strength. (if not fuse)
Certainly radios and equipment especially those connected to the mast should be disconnected at any risk of lightning. If you are in a marina connected to mains power then disconnect this. Mains can often get a high voltage induced in them which takes out anything connected.
The idea of putting electronics in the oven is perhaps warranted. The hopefully iron case will protect gear from some induced magnetism though I think if you have that much current inducing that much magnetism then you will have other concerns. The oven may act a a partial farady cage for electrostatic damage. If you don't ave an oven don't worry just disconnect. Major concern will be underwater gear and rigging. Finally make sure no one touches any metal of any sort. good luck olewill
 
JumbleDuck said:
This idea keeps cropping up, and it's wrong on two counts. Firstly, any oven with a glass door is not a Faraday Cage. Secondly, even if it was a Faraday cage, that only means that it stops external electrical fields from penetrating. It does nothong for magnetic fields which are what induce unpleasantly destructive currents in electronics. There may be advantages to putting stuff in the oven, but Faraday cageness ain't one of them.
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You must have a posh oven. Most boat ovens don't have glass doors.
 
ghostlymoron said:
You must have a posh oven. Most boat ovens don't have glass doors.
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Let's just have a quick shufti at the Force 4 website ...

Ten cookers with glass door, average price £652.95
  • Smev: £419.95
  • Force 4 Neptune: £499.95
  • Plastimo Neptune: £849.95
  • Eno Open Sea 2 burner: £829.95
  • Eno Open Sea 3 burner: £849.95
  • Eno Gascogne 2 burner: £849.95
  • Eno Gascogne 3 burner: £879.95
  • Dometic Starlight: £399.95
  • Spinflo Nelson: £499.95
  • Parker: £449.95


Two cookers with metal door, average price £2270
  • GN Espace Alize: £2395, metal door
  • GN Espace Levante: £2145, metal door

Mine's a Techimpex. It has a glass door.
 
>There may be advantages to putting stuff in the oven, but Faraday cageness ain't one of them.

OK what would you do? We've been on board two boats that had been hit by lightning their Windex, VHF aerial and wind instrument had been vaporised. Then it had run down the mast and rigging destroying all the instruments, VHF, DVD player etc plus all the wiring in the boats. If you put everything in the oven at least you have a reasonable chance of saving things, except the wiring and the mast items mentioned. By the way Faraday cages stop electromagnetic fields
 
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JumbleDuck said:
Let's just have a quick shufti at the Force 4 website ...

Ten cookers with glass door, average price £652.95
  • Smev: £419.95
  • Force 4 Neptune: £499.95
  • Plastimo Neptune: £849.95
  • Eno Open Sea 2 burner: £829.95
  • Eno Open Sea 3 burner: £849.95
  • Eno Gascogne 2 burner: £849.95
  • Eno Gascogne 3 burner: £879.95
  • Dometic Starlight: £399.95
  • Spinflo Nelson: £499.95
  • Parker: £449.95


Two cookers with metal door, average price £2270
  • GN Espace Alize: £2395, metal door
  • GN Espace Levante: £2145, metal door

Mine's a Techimpex. It has a glass door.
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Apologies, things have obviously moved on.
 
KellysEye said:
By the way Faraday cages stop electromagnetic fields
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They don't. A Faraday cage is a closed conducting surface which prevents external electric fields from penetrating to the inside. Magnetic fields are unaffected, unless by chance as a result of ferromagnetic behaviour of the material. Conducting media stop electromagnetic radiation, and this works even with holes in it as long as the wavelengths are larger (~10x or more) than the holes, which is why you can see through the grille which keeps microwaves inside your microwave oven.

Closed conducting surfaces used to keep EM radiation out are sometimes referred to as Faraday cages, though strictly speak they are not.

In any case (a) ovens with ruddy great holes on the front filled with glass doors are not Faraday cages in either sense and (b) even if they were where is this EM radiation supposed to come from?
 
>In any case (a) ovens with ruddy great holes on the front filled with glass doors are not Faraday cages in either sense

The glass doesn't help but the oven is a better bet than leaving all the electronic kit in place which will be destroyed a lightning hit.

(b) even if they were where is this EM radiation supposed to come from?

Lightning is an electrostatic discharge accompanied by the emission of visible light and other forms of electromagnetic radiation. I think the damage done is caused by the lightning which can have 100 million to 1 billion volts rather than EM, it was raised in an earlier post not by me.
 
KellysEye said:
>In any case (a) ovens with ruddy great holes on the front filled with glass doors are not Faraday cages in either sense

The glass doesn't help but the oven is a better bet than leaving all the electronic kit in place which will be destroyed a lightning hit.
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Perhaps in as much as it might provide a route round your gadgets, but I wouldn't be on it, as there will be huge magnetic fields as the lighting current goes through and that will induce all sorts of nasties in your electronics. Better keep the lightning away from there all together.

Lightning is an electrostatic discharge accompanied by the emission of visible light and other forms of electromagnetic radiation. I think the damage done is caused by the lightning which can have 100 million to 1 billion volts rather than EM, it was raised in an earlier post not by me.
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The number of volts is irrelevant, because large distances are involved and it's electric fields which matter. I have seen nothing to suggest that the EM emissions from lightning are particularly dangerous.
 
JumbleDuck said:
Perhaps in as much as it might provide a route round your gadgets, but I wouldn't be on it, as there will be huge magnetic fields as the lighting current goes through and that will induce all sorts of nasties in your electronics. Better keep the lightning away from there all together.



The number of volts is irrelevant, because large distances are involved and it's electric fields which matter. I have seen nothing to suggest that the EM emissions from lightning are particularly dangerous.
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Quite so. Although you can get some weird effects from electrostatic build up lioke St Elmos fire the real danger of lightning is when it discharges to ground. It is the huge current which does damage. Like instantly vaporising the sap in a tree to cause it to explode. The initial start of a lightning discharge can come from the ground up to the cloud via a relatively high resistance current path. (like tree) Once the plasma discharge path is made the real discharge comes down at high current. Any disruptions to the current path are quickly overcome or jumped across. hence once a discharge coming down gets to the top of your mast it is going to go through to the water. Any conductive path like wiring from mast top instruments or antenna will jump across to wiring that might go to the sea. Via prop etc or even log. The huge current will wreck any path it uses of course. Hence the value of the heavy cable mast base to water. Hopefully it will conduct thee current with not too much voltage drop.

The rapid rise of current either in the plasma or in any conductor will cause a rapidly rising magnetic field which can induce current into any conductor nearby. Like a transformer.
Farady cage is simply a cage of conducting material. It will act as a secondary of a transformer and soak up some of the rapidly rising magnetic field by causing currents in the metal. (note here it is only the changing magnetic field that induces current) If the cage is made of iron then it has the added advantage of conducting magnetic field (even a static field) through the metal so tending to dissipate more of the rising magnetic field. Even if the oven does no good at all the simple disconnection of gear and removel from its connections will be a big help. good luck olewill
 
my experience of lightning strikes is that there is very little you can do to prevent damage to anything electrical. I have seen boats directly hit where no damage has occurred, others that have been directly hit where everything has fried including battery powered devices with no batteries in them and rigging joints, and more where the strike was many tens of metres away but everything has fried. I have seen fork lightning hit the sea a few metres from my boat (Ionian Sea 2010) and we suffered no damage; so there is no rhyme or reason to this stuff.

Mrs thinks the best defence is an array of deities lined up on a shelf in the saloon and lots of prayer.
 
Marsupial said:
Mrs thinks the best defence is an array of deities lined up on a shelf in the saloon and lots of prayer.
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The best defence is a steel hulled boat.

Last night we had a direct strike at home took out our alarm system which is mounted in a steel cabinet which is not connected direct to ground so an ungrounded oven will only give little protection.

I have lots of lighting protection units fitted to all my electrical equipment at home, being in a very lighting prone area, and all must have a very good ground connection to work at all.

have a look here

http://www.clearlinestore.co.za/
 
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