Lightning protection

[richardh10]

Chatting with the guy on the boat next to mine, and he asked what protection I had against lightning strikes. It occurred to me that I had none, and that maybe I should have some. Bearing in mind also that he has a steel boat and I don’t. So should I attach some earth bonding to the mast, but where should the other end go, as the keel is encapsulated so there are no keel bolts?

Or, is it so unlikely that my present strategy of crossing my fingers is sufficient?

 

[Artic Warrior]

I used to wrap a chain around the mast and dangle it into the water if it looked possible for lightning..... now I have a steel boat

 

[matthewriches]

Have worked on a few boats fitted with Forespar's Lightening Master. A sort of a bottle brush type thing that goes up the top of the mast. You also find similar things on some transmission towers.

 

[matthewriches]

One of these https://www.forespar.com/products/boat-lightning-static-dissipater.shtml

 

[prv]

Lightning protection seems popular in the US, but it's fairly rare for a UK boat to have any specific provision. I don't know if that's because they get more lightning there, or if it's just a cultural thing that US boaters worry about it and European ones don't.

Pete

 

[coopec]

Richard

I have lightning protection on the yacht I am building (in Western Australia) but then my TV aerial has been hit by lightning, my neighbor's lobster boat has been hit and a farmer friend was leaning against his farm shed and he got a "tingle".

As Pete suggests the prevalence of lightning varies as to where you are. It is particularly bad around Florida and they recommend you head for the marina if a thunderstorm develops. They also maintain the average yacht will be hit at least once in it's lifetime

Lightning is particularly bad in the Amazon river. Right now (as of this minute) there are a lot of thunderstorms over France and Lands End.
https://www.lightningmaps.org/?lang=en#m=oss;t=3;s=0;o=0;b=;ts=0;
( You can move the map around with your cursor)

This map is also quite interesting: note how lightning is not common at sea. Also note the prevalence of lightning in Florida and the Caribbean.
https://geology.com/articles/lightning-map.shtml

Lightning is much more common in the summer months as can be seen by the Wiki map.
https://en.wikipedia.org/wiki/Distribution_of_lightning

Clive

 

[macd]

note how lightning is not common at sea.

True, except that there are plenty of strikes close to land. Given that leisure craft spend the vast majority of their time near land, it's not much of a comfort. Even a yacht logging 10,000 miles p.a. would be very close to land for at least three-quarters of the year.

This site also offers live lightning strike information: illuminating ambivalence and useful: http://en.blitzortung.org/live_lightning_maps.php

 

[coopec]

Lessons in lightning
A voyaging boat can expect one lifetime lightning hit, but the chance increases dramatically in hot, humid places, like the Intertropical Convergence Zone or Florida’s lightning alley, where as much as 20 percent of boats suffer some lightning damage every year.
http://www.oceannavigator.com/May-June-2013/Lessons-in-lightning/

Clive

 

[KellysEye]

>sort of a bottle brush type thing that goes up the top of the mast.

The previous owner fitted one of those on our steel boat and as far as I know they don't work. The only thing to do Is remove all the electrical kit and put it in the oven even with a glass door it acts as a Faraday cage. In Trinidad a boat arrived on the opposite side of our pontoon and it had a scorch mark on the flag on the backstay and no instruments at the top of the mast, he lost thousands of pounds of electronic kit because he had left them in place.

 

[coopec]

Why would you need lightning protection on a steel yacht? The lightning charge will be conducted to ground by the alloy mast and steel hull so what else is required?

I've attached X4 ss strips to my f/g hull and attached the mast to the main strip with a copper strip (25mm x 3mm?). All chain-plates have been attached to the earthing strips. (I have yet to attach all my stanchions, pushpit/pullpit, winches, steering wheel to the system).

Clive

 

[coopec]

>sort of a bottle brush type thing that goes up the top of the mast.

The previous owner fitted one of those on our steel boat and as far as I know they don't work.

Lightning Protection: The Truth About Dissipators

https://cdn.practical-sailor.com/media/newspics/643/p1cgh4oukck3dggm1r5kemm12sj6.jpg

Charge dissipators are designed reduce the likelihood of a strike. Unfortunately, what works in a laboratory, with very modest static charge quantities, does not work in nature.

Clive

 

[noelex]

Lightning strikes are very variable, but by providing a safe path to ground you greatly reduce the amount of damage, particularly the risk of catastrophic damage. A severe strike may sink a fiberglass boat, so steps to minimise the damage are worthwhile, especially if you are sailing offshore.

Contrary to popular perception, grounding the mast does not increase the chance of strikes, in fact as the grounding also provides a means of dissipating the boat’s static charge, the risk of a strike is very slightly reduced. The bottle brush static discharge rods take this a step further, but the chance of a strike is still only reduced very slightly.

So lightning protection to reduce the chance of damage is very worthwhile. However, there is little you can do to minimise your chance of being hit (other than avoiding locations where lightning is more prevalent).

Catamarans are hit more frequently than monohulls so if you have a cat lightning protection is particuarly important, although it is unfortunately it is also more difficult to achieve.

 

[coopec]

noelex

I agree with everything you say.

The scientists don't really understand lightning and even in the last few years they have revised some advice. But they agree lightning likes pointy objects (A pointed rod on top of the mast and discharge strips with sharp edges)

Catamarans and Trimarans are much more at risk than single hulls as you say.



http://marinelightning.com/catamaran/index.html#Probability

Clive

 

[coopec]

An interesting story.

His is the worst sailboat-lightning story I’ve ever heard, but I’m sure there are some that are never told.

While I was in Costa Rica I knew eleven boats that got struck, ranging from minor damage to total destruction of all things electrical and electronic.

NOTE: Costa Rica is near Panama

Lightning and Sailboats
https://www.sailfeed.com/2017/11/lightning-and-sailboats/

Clive

 

[William_H]

Yes lightning is unpredictable. Yes it is far more prevalent in America. The little brush type devices help to dissipate an electrical charge at a lower voltage this may reduce the chances of a direct strike. Lightning initially goes up from ground to cloud then the main strike comes back down this ionised air. This initial discharge is low current so can be conducted through high resistance material. Wet GRP wood trees etc.
Now obviously the ali mast is the most likely point of strike. It will conduct a lot of current before it is over heated due to large cross sectional area and low electrical resistance. When the charge gets to the bottom of the mast it needs to go to the sea. If wet GRP is only choice it will run through that, boiling the water so exploding the GRP. It will also run through any wiring that is connected to the sea (engine negative for instance) vaporising that wiring and possibly taking out any devices connected. So best bet is to take a good conductor directly from the ali mast to the sea. Connecting to a metal keel is ideal. However you are trying to deal with many thousands of amps. Even heavy cables may melt but may yet provide some conduction through the molten and vaporised metal.
What is really bad is to allow or encourage any current through the stay wires. SS has a (relatively) high resistance so will melt or at least over heat with even a few hundred amps. (permanently losing strength) if not melting.
The next problem is that even if you can conduct the current safely to earth. (the sea) the enormous current rising quickly will induce a voltage in any wiring on the boat. This high voltage can in itself take out electronics. Hence the idea to remove radios etc and put them in the (steel ) oven. Certainly disconnect all cables from electronics. (especially radio antenna) If you think a strike is likely. Don't touch any metal yourself .
Now back to OP question. Long experience will dictate what you need to do. So if no boats around yours seem concerned then don't worry. If other boats are hit (over the years) then yes be concerned.
Lastly look at any church steeple or tower and you will see heavy copper strip running from a spike on top down to ground. Typically 40mm and 6mm. Yes steeples were destroyed over the centuries but it would appear the lightning conductor helps now days.
For Coopec I have not heard of a lightning strike on yachts in our waters though an old radio mast at our club did take strike some years back. Me I just hope like heck. (and don't sail in an electrical storm. olewill

 

[jiris]

An interesting story.

His is the worst sailboat-lightning story I’ve ever heard, but I’m sure there are some that are never told.

While I was in Costa Rica I knew eleven boats that got struck, ranging from minor damage to total destruction of all things electrical and electronic.

NOTE: Costa Rica is near Panama

Lightning and Sailboats
https://www.sailfeed.com/2017/11/lightning-and-sailboats/

Clive

One realises how bad it can be only after seeing something like this:
https://www.facebook.com/ManShedOff...4C7vUcpnJfos-efpXIST2LAHnC0StbCAZ9MPDQqtkGJdI

 

[coopec]

"So best bet is to take a good conductor directly from the ali mast to the sea. Connecting to a metal keel is ideal. However you are trying to deal with many thousands of amps. Even heavy cables may melt but may yet provide some conduction through the molten and vaporised metal".

I have a copper flat bar 19mm X 5mm from the base of my mast to a 3 meter ss strip bolted to the f/g hull (no bends). (The strip is also linked to the motor). I'm hoping that will be up to the task.

"For Coopec I have not heard of a lightning strike on yachts in our waters"

I wonder how many lightning strikes are reported off our coast? My Sister's friends were hit 30 km off the coast which put their boat out of action - no radio, no engine. Luckily a boat on the horizon saw them get hit and came to their aid otherwise their boat would have ended up in Africa. That was not reported in the press.

https://www.youtube.com/watch?v=iO_E-xRJwxY

Clive

 

[chrishscorp]

One realises how bad it can be only after seeing something like this:
https://www.facebook.com/ManShedOff...4C7vUcpnJfos-efpXIST2LAHnC0StbCAZ9MPDQqtkGJdI

That is not lightening it is an underwater explosion to clear the channel of debris, looks fun though

 

[KellysEye]

We had a steel boat but the problem is that lighting can go down the wires and destroy the electrical kit.

 

[john_q]

Question

Ships and planes regularly get hit by lightening but seem to not have the problems we have with the resulting damage. I am told that the ships and planes use a DC floating ground system i.e. where the structures are completely isolated from the electrical system.

Could this be why they suffer much less damage?