Lightning Conductors

[Guest]

My Harding MOBO 26 FRC had a small stainless lightning conductor? fitted on grp foredeck, but not earthed - should I refit it & should it be earthed? Will it be of any use considering that there will be a lot of antennas and aerials fitted higer up on an A-Frame?

Roger Mathison

 

[LORDNELSON]

There is quite a good discussion of lightning protection in "The Marine Electrical and Electronics Bible" by John C. Payne
- second edition published in 2000, publishers are Adlard Coles Nautical, ISBN 0-7136-5724-3.

 

[oldharry]

An unearthed lightning conductor is not even as useful as a gauge for measuring the temperature of the bilge water. At least that would be actually doing something!

Various gadgets for lightning protection have been put forward, and sold - often at considerable cost. The limited research that has been done on them seems to indicate they are about as effective as a putting a welly over the top of the mast - in other words they do not seem to make much odds.

Most people - both theorists (who have not yet suffered a lightning strike) and those unfortunate enough to have experienced it afloat and survived ( or should that be 'fortunate?) - seem to agree that the best course is to provide a solid conductive path down to well below the waterline preferably outside the hull. The idea being to provide an electrical path outside the hull in the hopes it will avoid punching holes through the hull and sinking it - usually through transducers and skin fittings - and to avoid starting a fire below decks. Lightning is highly unpredictable, and dislikes intensly going round corners, so can easily punch its way through the glass fibre mouldings to reach the water outside.

Competetely disconnecting electronics from their supply, and from their aerials and transducers or sensors may also stop them being fried in the event of a strike.

 

[Guest]

Yes the small stainless lightning rod on the foredeck will be useless. and probably no better if it was earthed. There is a good artical on lightning at:-

http://www.thomson.ece.ufl.edu/lightning/SGEB17.html

It mainly centres around sailboats which automatically have a very good lightning attractor....it's motor. However you can see quickly what you are up against. Basically to ensure you are somewhat protected you need a lighting rod higher than any antennas etc and with a very heavy connection to the seawater. This is even more important if it is NOT raining at the time or there isn't a covering of saltwater all over the boat.

Occasionally we have lightning storms here but there is no rain or even wind. At these times I am more scared than during a real storm.

Cheers
Derek