What have you done to protect your boat from lightning strike?

[polecat]

I've researched this for several days and can find multiple references supporting absolutly anything I decide to do.   Not good.....  I won't ask what I should do - just interested in what has worked so far for you.  Also - what t-storm prep do you do - disconnect electronics? Use a metal box shield? What would you do to give yourself & your boat the best chance?
Thanks
jim

[Bill NH]

My Cape Dory 26D came from the factory with every shroud and stay grounded to an external ground plate with #8 stranded copper wire, as are the engine, fuel tank, fuel fill and mast step...  According to the builders, "While noone can predict how lightning will react when it hits a spar, we know from actoal experience that this system offers added protection."

However, I had the opportunity to confirm the value of grounding the mast on one of our previous boats, a 37' Searunner trimaran.  The mast was stepped in the center cockpit, and when lightning was in the area and we were at anchor I used to drape a chain around the base of the mast and let it hang down in the water in the centerboard trunk.  Without going into the details, once at anchor on Pamlico sound we took a direct hit from lightning.  There was no damage to the batteries or hull, though the chain actually jumped in the air at the hit.  Only damage was to electronic devices (alternator charge controller, GPS) due to the strong E-M field (the GPS was disconnected at the time!).  I fully attribure our minimal damage to the grounding chain.

But as you're finding, there's a great deal of conflicting info about lightning out there.  Best to try and avoid it if you can, and stay away from the metal stuff on board when you can't...

[Godot]

Lightening is weird stuff.  What follows is my take on it.  Not necessarily the truth.   

Conventional wisdom has it that lightning will more often strike taller objects as they are an easier path to ground than going through the air.  The thing is, I'm not sure how true it is, or rather, I don't know if it is true enough to base a lightning protection plan on.

The reason I say that is that this year (and presumably every year) there have been several severe lighting storms pass directly over my marina, and I have seen lightning strike the water within a few hundred feet of all those tall masts sticking up.   But I'm not aware of them ever hitting a mast.  My hypothesis is that while lightning will probably strike a taller, easier path to ground, it will only divert itself a very short distance to do so.  Instead of striking the bowsprit, for instance, it will strike the mast only a few yards away.

I've noticed the same thing while sailing myself in severe lightning storms.  Lots of wind.  Lots of lightning striking around the boat.  Lots of fear (and I mean LOTS!!! of fear) in the skipper.  But no strike on that 30 foot lightning rod sticking out of my boat.

Which is not to say that lightning isn't dangerous.  It is very dangerous.  Just that lightning doesn't seem specially inclined to do what you would expect it to do, which is seek out sailboat masts.

My mast is not grounded.  Lots of mast aren't grounded.  One common theory is that ungrounded mast are less likely to get hit at all.  My take is that the original path of a lightning bolt would have to be much closer before being attracted enough to divert to an ungrounded mast than to a grounded mast.  Maybe withing a couple dozen yards?  I suspect that wooden masts are even less likely to get struck (which tempts me to make a new wooden mast for my boat if I can't successfully straighten my currently bent aluminum mast).  I'm just guessing, of course.

The flip side is that if lightning does manage to strike, a boat with a fully grounded mast is less likely to experience serious damage. 

So what's a guy to do?

Given that there are so many theories about the best way to protect oneself from lightning, and most of them are contradictory, I have personally decided to take the path of least resistance (and least affect on my bank account) and go with what is already in place, which for me is nothing.  Someday I may build another boat.  When that happens I will have to make a decision.

[Norm]

Lightning!
We have had some drama this year around that very subject.  This year at BSC, a 25 footer was struck while members were sailing.  The helmsman suffered third degree burns and shock when a surge came up through the rudder, along the tiller, affecting the arm and torso of the driver.  Everyone is OK but shaken.

I observe that lightning seldom strikes sailboats at sea.  One never hears of buoys being struck.

Our boat is grounded.  We try to sail away from the storms that have lightning in them.  Tough in enclosed waters. 

[polecat]

Norm - Do you know how this 25' boat was set up?  Grounded? use thru hulls for a ground?  Were the gudgeons on the hit boat tied to the ground system?  What do you use for a ground? 
thanks
jim

[AdriftAtSea]

Norm—

Was that one of the Olson 25s???

[Norm]

Hello All:
The rudder is under the boat and has a stainless steel shaft attached to a wooden tiller.  The boat type is an Olsen 25.  I doubt the boat is grounded or bonded.  O25s were built to a pretty low price point.

I heard a story about a guy with a Morgan 44 in Florida who has been struck 4 times in the past five or so years.  Seems most strikes are at the dock or in the Intracoastal.  Any of you guys in the Intracoastal have insights?  Anecdotes?

Which brings up a point:  I sense that being close to shore is more of an issue than anything else.  I don't see a lot of direct ground to cloud strikes at sea.  Lots of cloud to cloud discharges.

Norm

[AdriftAtSea]

Florida has a pretty high number of lightning strikes, since they have more lightning storms than many other parts of the country.

I think Norm may have a good point... it does seem that off-shore lightning strikes are less common than ones at the dock or at anchor.  Of course, being at anchor means you've got a connection to the earth from your boat, especially if you're on an all-chain rode. :)

[polecat]

The Pearson Renegade that I'm (OK I'll go ahead and say it) rebuilding doesn't appear to have ever been hit by lightning in 40 years.  It is completely bonded like Bills CD26D.
It has lived most of it's life in severe thunderstorm heaven (Texas). Thats all good but I was planning on replacing the only three bonded proper seacocks & thruhulls with marelon.  Then I got to thinking about just what this bonding system was supposed to be grounded to.  And started investigating Lightning protection & asking questions.

This is what I've come to believe: There seems to be two main problems that we have in dealing with lightning 1) Your boat has to dissipate and conduct the energy thru itself to ground. 2) EMF

a) An ungrounded mast is less likely to be struck by lightning as it does not necessarily place a ground point closer to the lightning source

b) An ungrounded mast if struck is much more dangerous to humans than a grounded mast due to dangerous flash over.

c) The more good bonded paths to ground you have the safer your boat, due to less likelyhood of flashover.

d) It is possible for a well bonded boat to experience flashover  if there aren't enough paths to ground to dissipate this particular lightning bolts energy.

e) Removing all the bronze seacocks & replacing with Marelon would lessen the attachpoints to ground for the bonding circuit and flashover could come from any bonded point and humans are better conductors than air. You really don't want to be part of a plasma stream...

EMF (Electro Magnetic Force)
The only reference I've found for protecting electrical equipment was to keep a spare gps/vhf inside a sealed ferrous metal box.  By the time you think to disconnect your electronics - it's usually to late -- no need getting super zapped.

I plan on staying with Bronze electrically bonded to ground seacocks/thruhulls thruout the boat - even have to add 3 more - 2 for the cockpit drains and one for the sink drain.  For at anchor or in port use - will make 2 drop over the side 3' long copper tubes flattened - hook em up to the shrouds with a battery cable

And then again I could be wrong - your mileage may vary
jim