Lightning on masts

[Fanie]

Is lightning a big risk on masts during storms ?

[lazeyjack]

yes and no, I was struck over and over in our steel yacht in Fiji, all it did was knock out our ssb, via the backstay
It is a real risk even in boats with grounded mast, because if the high voltage, it can neevr be relied upon to take a certain track, I mean you can not expect a million volts to track down a 6mm wire, so often the lightening will blow out meatal seacocks and the like, CertainLY GROUNDING THE MAST TO KEEL BOLTS DOES HELP, but really you can not control the path it may take
All in all, many boats come away with the men in them alive after lightening strike, albeit lacking a lot of expensive equipement
I will say this, it is very scary and bloody noisy

[Fanie]

Certainly the steel boat provided a shied around you. How about if it's a fibre glass boat. If a mast is through-cabin, can or will it be life threatening ?

[ted655]

Here are some things to know that might help in making decisions.
Lightning is always in a hurry, it doesn't like to make sharp turns.
It prefers a surface path, pipe is a much better conductor than wire, other things being equal.
It will jump, it's always seeking a faster path or "paths" to ground.
The height of the initial contact is not always the tallest structure, but rather the better path.

[Ike]

If you go to menu at the top of the page and use the search function, searching on lightning you will find that this has been discussed many time. Here's the most recnt thread http://boatdesign.net/forums/showthr...ight=lightning

[Fanie]

Ok, I've read the posts made that Ike suggested, thanks. I still don't have an answer, is lightning on a boat with a metal mast life threatening, or are there no-one alive to tell about it

Wrt the electronics that gets damaged. Even if plugged out it can get damaged by EMP. Such an electro magnetic pulse can be very large. Equipment with metal shielding inside would have a better chance to survive than if enclosed only in plastic.

If you place electronic equipment inside a lightweight metal enclosure you should get about zero lightning damages, unless maybe in a direct strike. The CSIR once showed how safe automobiles are, lightning travels outside the body, never in, so the occupants are safe. Same for equipment.

The real reason plugged-in electronics get damaged is a simple matter of ohms law - if a radio is connected to the mast antenna, and even grounded really well to the mast, the radio gets damaged purely using ohm's law.

The low ohm value of the mast, conducting many thousands of amps works out to a huge huge voltage drop that is frying the equipment. It is this immense current from the lightning bolt that generates an electro magnetic field (EMP) that buggers the equipment up.

The best metal to use would be 'mu-metal', you find it in hard drives and floppy drives to shield the magnetic fields from the supermagnets to the magnetic media they use in them - otherwise the saved data on a drive will get erased faster than you can write it.

While still magnetic, this metal prevents magnetic fields to pass through the metal. If you place a magnet on one side nothing will be attracted on the other side. The same with other metals is not true to a more or lesser degree.

You don't need a direct lightning hit to lose equipment from EMP. The world's biggest fear should be if a meteor enters the atmosphere and create a large enough EMP to destroy all electronics. Everything would come to a screetching halt. Ok, maybe not all boats...

[PAR]

Lightening can strike a metal mast, can damage equipment and all the rest. I've been struck twice, once in an unprotected production sailboat and the other in a well protected wooden ketch. Both strikes were on the mast (metal rod and wire on the ketch). The unprotected boat was holed by the strike, as its path out was through the centerboard pin, which the surrounding materials didn't like the quick rise in temperature. The ketch blew a few of the wire clamps, holding the cable to the mast, free and the connection between the masthead mounted rod and the cable was burned through. Some charred wood was evidenced under the cable, but this was the extent of the damage.

I've known of several people who have been struck aboard their yachts and repeatedly, the protected boats faired much better then the unprotected. I've read about lose of life from strikes, but it's reasonably rare and most had the misfortune of taking the strike on a body part (usually the head). Personally, I live in the lightening capital of the world. On a summers day, when the afternoon thunderheads build, we may experience 6,000 (typical average) in an hour. In particularly bad, usually very lager storm cells, doubling this number isn't uncommon. Things get hit, trust me. Automobiles are naturally protected by the insulating effect of their tires, though electronics can be affected. People in close proximity to a strike will get hurt, mast or not.

In direct answer to your question, yes you can die, but more often then not you'll just get the crap scared out of you. It's a matter of willingness to accept risk. You're willing to go father from shore then you can safely swim back too. You may have potentially explosive chemicals and fuels aboard this vessel. You have bits and parts of rig that can bonk you on the head well enough to mash your skull, but you can accept these risks, with understanding, equipment and reasonable skills. This same logic applies to lightening. Set up a protective cone for your yacht and you'll fair better then those that elected not to.

[tuks]

Lightning is a risk, but I wouldnt worry too much about it. On the Vaal Dam there are over 1000 boats, in a fairly high risk lightling area(highveld thunderstorms almost every day in summer). Only a few boats get struck a year. There are other things which are more dangerous.

In one particularly bad storm, I have seen multiple strikes around me including the local farmers house which burned. I thought I was going to die. Its weird, when there is lightning around, I wont go fishing with a <3m long fishing rod, but am fairly comfortable in a boat with a 10m mast.

[Fanie]

So it's a 'normal' risk. Btw, lightning occurs from the earth up, and not down as is common believed.

We were at the Gariep dam (centre in SA), if you carried a carbon fishing rod you'd get shocked by the static. We were'nt long at the specific spot.

When fibre glass yacht building, do the builders glass metal into the boats for lightning diversion ?

[tom28571]

Originally Posted by Fanie

Ok, I've read the posts made that Ike suggested, thanks. I still don't have an answer, is lightning on a boat with a metal mast life threatening,

The answer is, YES, a lightning strike on a sailboat mast is life threatening. It is a bit like crossing a street with blinders on. You may be killed and maybe not. Several people have given good answers to your questions. Ted's list is good. The best you can do is to study the problem, which you are doing, and then choose how you will work out your particular "solution."

Lightning is like the weather, it may be predictable but not very well.

[ted655]

I have held many hot wires without injury., (rubber soled shoes on dry surface & spare hand in my pants pocket or holding the same item) Anyone can, as long as you don't become the path to ground. Give the lightning a better path on your boat, OR don't become the cross over TO a better path and "happy sailing" Provide a better conductor to ground than anything around you, (bare wet feet or both hands touching separate items), and it's "fried Popeye".

[Fanie]

Lightning is like the weather, it may be predictable but not very well.

Sounds more like a female if you ask me

[chandler]

Lightning goes from the ground up????, What would cause the earth to spew electricity????

[Fanie]

Read up on lightning

[Fanie]

If lightning does pose a serious thread, why doesn't they glass metal sheets or strands in the cabins and hulls to divert the lightning ?