Lightning Protection

[EdD]

Lousy sailing weather in north-central South Carolina this weekend.  Lots of storms blowing through...much lightening.  I don't mind getting wet but I have a VERY healthy respect for lightening.  Ain't it great that we have a built-in lightening rod right on our boat.

My Hunter 23 had a cast iron keel with a heavy duty cable running from the mast base to one of the keel bolts.  I don't know how effective it was but at least I had something.  Maybe it was just a false sense of security...not that I was about to test it.  I was wondering what some of ya'll do to address the lightening issue, particularly on center board boats. 

I read in Robert Burgess' book "Handbook of Trailer Sailing", that he attaches automobile jumper cables to the forestay and puts the other end in the water.  Has anyone heard of this?  Does anyone (who is still alive) know if it works?

Until I can find an affordable Suncat (oxymoron), I need to do something with my MacGregor 21 Venture.  Any suggestions?

EdD

[AdriftAtSea]

With lightning, the most important part is how straight the path is, and that the conductor is heavy, flat and has good edges... static electricity tends to travel over the edges of the conductor, and .03" copper strips work much better than an equal weight round wire IIRC.

If the conductor takes any sharp  bends, you may get flash over, where the lightning jumps sideways.  Very dangerous. 

Improperly lightning grounding the boat is IMHO more dangerous than not grounding it it all... but that's just my opinion.

[Captain Smollett]

There is one school of thought that says "if the mast is not touching any metal, there is no path to ground."   So long as you don't provide one, this theory goes, you are just as safe as grounding the mast.

I could probably dig up some links if interested.

YMMV.

[starcrest]

in my personal opinion theres no way anyone can escape a strike by lightening completely unscathed.its best just to live life without upsetting the "Great Overseers of All Things".lest they strike yee down.and if yer' out there in the middle of a severe electrical storm-or if ya'see one coming---head the other way quickly-even if yaz' gotta motor it.---that mast sticking up is jus' askin'fer'it.especially if you're the only one around. I would disconnect all electrical components---including the battery---and attatch possibly the anchor chain somewhere to the rigging and allow an anchor to drag overboard---with the pretense of allowing such a charge to  diffuse over the largest area below sea level.remember --these things can and do happen in real life---not just on tv. we have all heard of the people on golf courses getting struck ---with just a golf club in hand- one precursor to this is if your feel you hair standing on edge----get down---its zeroing in on you----plus there is reportedly a distinct aroma of ozone---(then its probably too late)---sleep tight!(or atleast with one eye open)

[xroyal]

This a popular subject in boating forums now! It sort of reminds me of illness warnings in the media. Do this to avoid that. Then you find out that 3000 people out of 300 million people were affected. Sure lightning can be scary/dangerous, but how many sailboats and crews actually suffer hits %wise?

Read one comment about being in a lightening storm one might hook a ground to the battery and throw it overboard. Going to the keelbolts makes more sense to me. Or, maybe staying home when the threat arises appeals too. If I were a long term cruiser or liveaboard I'd sure take this seriously.

[AdriftAtSea]

Just remember a lightning bonding system isn't really to protect the boat from a lightning strike, but to protect the occupants of the boat in the case of a lightning strike.  There really is no way to prevent lightning strikes from doing damage to the boat hit.  You just want to try and make sure that no one who is unlucky enough to be on board is killed or badly hurt.

[maxingout]

When I sailed through the Singapore Straits, there were 5 sailboats struck by lightning within one week.   All of them had extensive damage to their electronics.

I read in a cruising guide that one boat out of a thousand gets struck by lightning each year cruising the Bahamas.  We did an eleven year circumnavigation, and we were never struck by lightning.  We avoided thunderstorms by changing course if necessary.

We also had two static electricity dissipators mounted on the mast - two different designs by two different manufacturers.  I don't know if they made a difference, but it made me feel better just knowing that they were up there on the top of my mast.

Cheers,

[Lynx]

The jumper cables tech has been around for a long time. If you do not have a good ground, that is metal in the water that is connected by thick wires, it works. Just make sure that it is not bad looking.

When I was in bimini for 1 week there was a boat that had the VHF destroied by a storm.  It is thought that in Fl your chances are 1 in 5 that your boat will be struck by lightening. I think that this is a bit high and misleading.

The different lightening protection on the mast does help to some degree but just having a mast is a help and having the shortest mast in the harbor helps. Not having any electronics on the mast helps. Lightening has melted plastic through hulls and sunk boats in Florida.  I have been in the water many days and miles in Fl.

Just part of the thrill.

[Fortis]

The only lightning damaged boat I have ever personally seen was a keel-steped GRP yacht that ended up having about 300 very small holes burnt and chipped through the fibreglass of the hull below waterline. No hole was larger then the tip of a ballpoint pen...but there were lots and lots and lots of them....So they spent a few days bailing and using the manual bilge pump (the electric one having died along with most other things.

Their mast survived for about ten hours after the strike, but then broke in a "weird" way in 8-10knots of wind. The skipper beleived that the lightning strike had effectively played heck with the temper of the aluminium mast, leading to a band approximately a foot wide and just below the bottom spreaders to shatter into shards.

They were able to hand crank the 20hp diesel and make for home, using a hand bearing compass to navigate.

Definately scary stuff.

Amongst some of the stuff that got zapped that I had never considered before was the electrically operated solenoid valve for the gas bottles to run the stove, the aforementioned bilge pumps, and the rudder bearings...

Tunrs out the rudder tube was a copper pipe that had been glassed over on the outside. It was earthed to the keel but somehow managed to heat up to the point where the tiller bushes had de-natured (I am not sure if the material could vulcanise, but it went brittle and crumbly and the rudder was shaking around in its mounts because the holes in the bushes had enlarged).

Interestingly enough, no one on board was seriously hurt, though a man that grabbed hold of a liflen suffered a burn and muscle aches on his shoulder, even though he was gripping on by his hand.

All very very odd.

The insurance company tried to get the matter resolved by offering a new mast and some work on filling the hull. They ended up going to court and the boat was written off and payed out (No one wanted to do a full survey of things like the keel-bolts because they were more or less inaccessible on that design of boat).

That's about everything I can recall about Far Horizon. Other then that I was not allowed to salvage any hardware off her once she had been declared a write off...Such a waste of ST winches.



Alex.

[AdriftAtSea]

From what I've seen, there are three schools of thought on lightning protection. 

1)  Ground the boat's mast, shrouds, stays, stanchions and other large metal hardware to a large underwater grounding plate.  This will give the lightning the easiest path through the boat and give the occupants the most protection.   

The advantages of this are that it does give the boat and occupants the most protection from a lightning strike.  However, it also does make it a far better target, so the chance of getting hit actually goes up a bit. 

2)  Don't ground the boat or do anything that would increase it's ability to conduct lightning.

This minimizes the boat's appearance as a target, but generally, if the boat is hit by lightning, it will be damaged to a far greater degree than a properly grounded and lightning bonded boat.  This sounds like what happened to the boat Fortis was describing... the multiple pinholes sound like the lightning sideflashing to get through the hull to the ground.

3)  Put the lightning dissapators on the mast and be done with it.

Generally, the lightning dissapators are patterned after the ones that protect things like radio towers...and IIRC, don't really function properly unless the boat is properly and well grounded.  However, I think that a it is a bit unrealistic to think that a small brush type dissapator can have any real effect on the several square miles of sky used as the source for a lightning strike... If you really think these things work, I got a bridge to sell you.

[CharlieJ]

And then we come to boats like ours, with wooden masts, and NO path down the mast to ground, so the upper shrouds become the only reasonable way to ground.

I've seen two boats involved with lightning strikes . One was a wooden masted vessel, with a mast far shorter than the two aluminum masts sitting on each side. the strike came to the mast head and blew it apart. Apparently water had gotten inside some glue joints and the bolt super heated it and destroyed the mast head. NO other damage to the boat- none. But note- that mast was at least 5 feet shorter then the metal one each side. None were grounded.

The other boat was an Irwin 37 ketch, sitting on a mooring. I SAW the bolt hit, about 15 feet to one side - a water strike . Didn't touch the boat at all. Fried every piece of electronics aboard and the boat was unattended at the time. NO damage to the boat itself.

I've been in some pretty serious thunderstorms, both in Texas and Florida  and the Chesapeake) both on boats with grounds in the water and on ungrounded boats and never been hit- yet! I think it's a roll of the dice, personally.

By the way- lots of offshore sailors are putting a spare hand held GPS and a portable VHF inside a metal can stored in the boat- sort of a small Farraday cage if you will, to protect sensitive electronics from stray shots.