Lightning protection for steel hulled boat

[Lomax]

My boat (steel hull & superstructure) has a ~3.5m tall wooden mast (not for carrying sails), which is festooned with various bits of equipment; navigation lights, antennas, weather instruments, etc. It is mounted on the cabin roof, which sits approximately 1.5m above the water, so the top of the mast is about 5m from the wet. I am worried that it could potentially(!) attract lightning, especially with all the electrical conductors running down it. What steps can I take to ensure that if I get hit by lighting 1) those on board remain safe 2) electronic equipment connected to the mast doesn't get damaged?

Edit: More specifically, I am wondering if it would be worth putting a "lightning rod" on top of the mast, and connecting this to the cabin roof with a hefty cable. Also whether inline "lightning arrestors" or "surge protectors" on the wires going up the mast provide a good level of protection for the equipment at the other end.

 

[NormanS]

Stay close to saily boats with tall masts.

 

[Lomax]

Stay close to saily boats with tall masts.

LOL!

 

[William_H]

If you are concerned about lightning protection then yes A heavy gauge cable from a conductor on the top down to the cabin top should provide protection for the mast. Surge protectors like voltage dependant resistors would be useful on light wiring. However I am not sure that they would permit the radio to work well with them on the antenna cable. An antenna with a coil inside to ground providing a DC short might be preferable but this might evaporate pretty quickly with the induced currents so perhaps you should accept that the VHF radio might be lost in a strike. Disconnect if a storm approaches might be the best idea and carry a HH VHF.
In the end much depends on where you sail (some places are a far greater risk of lightning than others) and your own personal concern.
Funny today is forecast to have thunder storms here and I am going to do a race this afternoon. Lightning is not so common here. I don't know of any boats being struck although many years back our club radio tower got a hit but with no real damage. I will probably just hope for the best. Although if I was concerned I would connect a heavy cable from ali mast base to a conductor plate or chain in the water. olewill

 

[Lomax]

Thanks William. I have been looking at ham-radio set ups and they take lightning protection very seriously. The usual approach is a copper ground-plate (Single Point Ground, SPG) on which they mount the individual lightning arrestors for each antenna:



Bit overkill for my needs perhaps, but made me wonder if I should do something similar. It's not just the VHF I'm worried about; I also have three onboard computers, with GPS and AIS receivers, and a (pricey) 3G/4G router. A lightning strike could prove to be a very expensive experience - not to mention how time consuming it would be to rebuild everything from scratch.

 

[KellysEye]

There is a debate about whether gas ovens and microwave ovens are Faraday cages. What I would have done if lightning was close is disconnect all electrical kit and put everything in our gas oven and cover the glass with multiple layers of tin foil. Anything at the top of the mast will be destroyed as we saw when we had a boat park next to us on a pontoon in Trinidad that had been hit by lightning. He hadn't tried to make a Faraday cage or at least disconnect all the electrical kit so everything was destroyed. The most interesting thing was there was a scorch mark on his small red ensign on the back stay.

We were sailing at night off the Venezuelan coast and the radar showed lightning building all around us, I was on watch and I heard the loudest bang I've ever heard, the brightest flash I've ever seen and the smell of ozone, I hadn't prepared anything because it was cloud to cloud. The closest we came was on passage from Grenada to Mustique an unexpected squall line formed close by, lightning hit the water about 30 yards in front of the boat and we had Elmo's fire crackling in the rigging but no damage.