Lightning Protection

coopec

coopec

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I'm going to quite a lot of trouble installing a lightning protection system. I've read a number of articles detailing the damage caused by lightning on unprotected boats but no articles on damage to lightning protected boats.

Is anyone aware of just how effective lightning protection is in the case of a direct hit?

If nothing else it might give me a little peace-of-mind when in the vicinity of a thunderstorm.
 
coopec said:
I'm going to quite a lot of trouble installing a lightning protection system. I've read a number of articles detailing the damage caused by lightning on unprotected boats but no articles on damage to lightning protected boats.

Is anyone aware of just how effective lightning protection is in the case of a direct hit?

If nothing else it might give me a little peace-of-mind when in the vicinity of a thunderstorm.
Click to expand...

Tests in America showed that some lightning protection actually did the opposite, and attracted it!

Nothing will actually stop 30 million volts going where it wants when it wants. About he best you can do is to ensure that you have no spiky bits which could encourage charge leaders to form on your boat.

Maybe the lack of information is because it doesnt work. Its a bit like the anti-elephant hat. The fact nothing has happened doesnt mean it works.
 
IMHO the only to protect you boat from a lightning strike is to make the hull from metal (steel or aluminium) with metal mast and rigging.

It then becomes a Faraday cage protecting all electrics inside metal structure and directs any direct strikes direct to ground around the outside like metal skined aircraft.
 
I am not a surveyor or boat designer but...

I did a bit of research into this a while back and came to the conclusion that retro-fitting lightning protection to a small fibreglass yacht would be difficult. If you have a fin keeler with a keel stepped mast, connecting the two together MIGHT be a good idea... but you'll still get side flashes from the rigging unless you ground all that also.

Otherwise providing a safe ground involves a large metal plate on the outside of the hull and lots of very thick wires (16mm2 min) throughout the interior that need straight runs.

Lots of details of the counstruction of a system here - http://www.marinesurveyorschool.org/seminar_files/Lightening Protection.pdf

Good news is if on deck away from possibly side flashes people are inside the "cone of protection" from the mast so shouldn't be injured. If you get struck the usual best case seems to be all your electrics get fried. The worst case (assuming no injuries and the gas is off) is large holes in the hull as metal fittings get blown out. An incomplete system may make things worse - increasing the chances of your boat being struck by improving the path to ground without protecting the whole vessel.

In the end I decided for my boat no protection was practical and that I would just hope to not be struck, in theory the odds are in my favour...

All of that said, lightning protection is common on American boats in higher risk areas - I suspect it's built in from new before linings and things get installed and that they design in good straight routes for the relevant cabling etc.

Please do take all the above with a pinch of salt though. Your safety decisions are your own and should be made based on expert opinion mixed with your own. Not mine :)
 
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There is a big study on US boats around [ Maybe on BoatUS ? ] The stats showed the masthead mounted inverted mop type did not reduce the chances of being struck.

I was interested in protection because I suffered a direct hit some years back while at anchor in Beaufort North Carolina. I was sitting below having seen the storm coming and had disconnected most electronics and placed them on a wooden table. The boat was a steel 38 ft ketch with a mizzen mounted fluxgate compass for the autopilot. The hit vaporized my masthead tri and masthead mounted VHF aerial. Nothing was left except some small metallic blobs on the deck. The Windex survived.

Of the onboard electronics about a 1/3 was blown including some but not all florescent lamps, the color TV and my freshwater pump. An unexpected problem was that the hull was strongly magnetized rendering all magnetic compasses useless.

So that kinda shoots down the faraday cage theory.

Some people say that you should put small electronic stuff in the oven.
 
Here in Rio Dulce, Guatemala 16N 88W, every summer about 12 to 14 boats get hit, a lot of these vessels are from the US and some have some sort of lightening protection.

Catamarans seem to get more hits than mono hulls. I believe there is quite a bit written about this and it is due, in some part, to the wider stay base on a cat not being able to dissipate the hit as well
 
Thanks everyone: your posts are helpful.

My 43ft is under construction so I can do what I want as far as lightning protection is concerned. I have 5 grounding strips (4 for the rigging and one for the aluminum mast (all are interconnected. I will also include the pushpit and pullpit)

I have done a lot of research on the subject but I will follow up on your references. Thanks.

Apparently lightning strikes on ships are common and my neighbour's lobster boat has been hit. Looking at the global map of lightning strikes the UK doesn't really have a problem.

http://geology.com/articles/lightning-map.shtml
 
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