Lightning rod on ferro boat

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CharlesM

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Hello all

I am a little afraid of lightning. Any recomendations about installing a lightning rod/conductor on a ferro boat?

I have wooden masts, so cannot use the mast itself...

I imagine one would attach some kind of conductor down the mast, but how and where? Then once it reaches deck what then?

I know the path should be as short and with the fewest number of curves/bends possible... but what happens from the base of the mast till it gets to the water.

Also, since Serendipity is a ketch, should we place conductors on both masts or just the main?

Anyone in the know please share with me.

Thanks
Charles
 
I'd have a search on some expert opinions/research but it was my understanding that you dont actually want to encourage the lightening to earth through anything on the boat. I dont know if they are true but stories of lightning exiting through an earthed skin fitting and leaving a large hole seem feasable.

My experience of meeting several boats that have cruised in the Pacific / Japan where large electric storms seem to be more common, is that they use the earthed spikey brush mounted on the mast to disperse charge and prevent a strike.

This sums it up nicely http://www.boatus.com/seaworthy/swlightning.asp
 
Hi Tigawave

I would agree with the attempt to dissapate the charge, but it looks like there are great similarities between a lightning rod and a protection system, with the only diference being a fuzzy brush (to try dissipate) at the top rather than a spike.

Is my understanding correct?

Cheers
Charles
 
I think the lightning is more likely to run down your rigging than a wooden mast, maybe some sort of earth to ground (sea) connected to your chain plates?
 
Hi Charles, welcome back.
They are similar in that the dissipator and lightning rod both have to be connected to ground by a metal mast or a wooden mast fitted with a suitably sized cable. From the base of the mast the cable should go as directly as possible to a significant mass of metal. An external metal keel or a large grounding plate. The dissipator, properly connected to earth, is supposed to discourage a strike. Sounds like gobbledygook to me, given the awesome power of lightning. I had wooden masts on my ketch and no rod or conducting cable. When we were struck the mast was unharmed although the masthead instruments were vapourized. All electronics were lost and the alternator controller burst into flames and set fire to the engine compartment. Oh joy! The strike went to ground via the rigging I assume. If your chainplates are external and they reach the water, that might be the route a strike would take. Faced with lightning storms we now protect people by putting them below, away from metal, and electronics by disconnecting them and putting them in the oven. In my opinion you can't do anything about a strike so you just have to try not to worry about it. It is a pretty rare event after all.
 
I amassuming that your masts have metal rstanding rigging.

If so this will be effectively at earth potential, and as such will form a reasonably effective cage to protect you.

I cannot see what difference a spike or even a fuzzy spike will make.

Interestingly a lightning strike is initiated from the earth upwards, so what a spike does is make a strike morelikelt to start from the spike than from any other nearby point.

If you are really worried about lightning you may try consulting BS6651:1999 which gives a standard for protection of buildings.

http://www.buildingdesign.co.uk/requests.htm also gives a lot of good info on lightning protection.

But what the hell - we all have to go sometime and if its your turn its your turn, there's worse ways than being hit by lightning.
 
I agree with Bergman to the exten that as I understand it a very fine trace discharge starts from ground and reaches up to the cloud where upon a huge current decends. It seems to me a pointed rod or fuzzy brush is designed to discharge at a lower voltage any static build up but will encourage a leader strike. (could be wrong).
If it were me I would be running a heavy copper wire or copper strip from the highest metal of the mast (not VHF antenna ofcourse)and taking this down to a ground in the sea water. If you have an insulated keel then about 2 square feet of metal has been suggested as adequate to dissipate the strike. Propellers and running gear in the water may not be large enough and may then be damaged by the current if used as the ground connection.
Stay wires are usually stainless steel whiich has the worst characteristics of being conductive to encourage a strike but quite resistive so that any real lighning current would cause the stay to overheat or fuse. An aluminium mast on the other hand has low resistance and hopefully can conduct the currents without overheating. So for a wooden mast you need to protect the the stay wires, I am assuming the wooden mast is dry and not conductive.( living trees provide enough conduction to encourage a strike but have resistance so the moisture boils and the trunk explodes from moisture vapour) The way to protect the stays is to provide a low resistance (wire) connection. This should be as heavy as you can manage but wire the size of your starter feed wire would probably be adequate. Anything smaller may or may not suffice. Who knows how much current you will need to dissipate? You often see on old churches a copper strip 2 inches wide and 1/8 inch thick. They must find that adequate.
As for puting electronics in the oven my gut instinct is that that is overdoing it but certainly you should disconnect all aerials and unplug power and earth connections. Good luck olewill
 
Best to buy Nigel Calder's book on boat electronics and mechanics - latest version from Amazon at less than £20. There's a very good section on lightning protection that suggests using a rod with a rounded end (the brush types don't work apparently i.e. preventing a strike) at least 6 inches higher than other antennae. Then running copper wire down the side of wooden masts and taking this to a metal grounding plate on the hull. There's also a comment on ketches but I can't recall what he says.

Interesting what might happen if the strike reaches the ferro rods in the cement in the hull? Hm, could be very interesting.
 
My ferro has a metal mast. If I run some copper down the mast..well, does this bit of metal stay outside the boat but is then stuck on to something?
Oh, I'm such a fool. I know nuffing but I do learn alot from you guys.
Actually, I have the Calder book but it's over in Mexico. I will consult it.
Thank you Charles for asking all these questions. It's really helping me indirectly.
 
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