hit by lightning

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rbpfyo
Posts: 82
Joined: Sat Nov 15, 2014 7:58 am

hit by lightning

Post by rbpfyo »

apparently my boat was, years ago, and the foremast was replaced (39 Pilothouse here)
now every time I walk up to it in the marina, I have heart palpitations
my spars are the highest thing around
question:
how do you prevent a strike? or direct it harmlessly to earth/sea?
boat is new to me, and I'd like to make sure whatever system exists is in place and fully functional
I assume there's some kind of grounding strap from mast tip to underwater?
thanks for any info
Rolf in MA

rbpfyo
Posts: 82
Joined: Sat Nov 15, 2014 7:58 am

Re: hit by lightning

Post by rbpfyo »

bump
are we just assuming that carbon spars do not conduct electricity?
how about wet ones? or ones with wires running through them? or wet sails raised? with bronze fittings running in aluminum tracks, 55' into the heavens?
based on the fact that mine was already hit once (and the mast apparently split in many 'petals', like an exploding cigar in a cartoon), I am eager to do what I can to avoid another strike
thoughts? thanks
Rolf in MA

RonR
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Joined: Mon Jan 05, 2015 7:03 am

Re: hit by lightning

Post by RonR »

I have not much experience with carbon fiber masts, but from working with other carbon composites I can say that they do conduct electricity- the carbon does, anyway. It’s not hard to imagine the the heat generated by current passing through a CF mast would seriously compromise the integrity of the resin.

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folotp
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Re: hit by lightning

Post by folotp »

Hello Rolf,

Protecting the mast is relatively easy. You need to install a lightning rod at the mast head, connected to a down conductor that connects to suitably sized grounding plate at or as close as possible to the base of the mast. ABYC recommends a conductor of at least 6 gauge, 4 gauge better.

The main question I have regarding lightning protection, and maybe someone can help, is how do you protect a sleeper in the V-berth from side flashes if the forward mast is hit? A side flash is very common and is when the current coming down the conductor in the mast decides not to exit where you planned, on the grounding plate, but instead decides to jump sideways, possibly through someone, but very often through water tanks, and then through the hull to the surface of the water. Lighting prefers to exit at the water surface.

This web site has a wealth of information on marine lightning protection. I plan on retaining their consulting services latter this year to help on my lightning protection plan.

http://www.marinelightning.com/

Cheers!
Pierre-André Folot
s/v “Farfelu” - Freedom 39 PH 1983, hull #14
Sailing the Thousand Islands and Lake Ontario
Canada

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VeloFellow
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Re: hit by lightning

Post by VeloFellow »

In florida, I have been in a few thunderstorms already in Clave'. We do try to avoid. But they are near daily summer events. Whether sailing, anchored or at the dock, lightning is about. No hits yet. Interesting topic. There were 23 lightning deaths last year, least on record. 450000 smoking deaths, 250000sitting related deaths, 250000eating choice related deaths. Urbanization and mechanization thought to be reasons for most decrease. When Previous owner switched mizzen and main mast after repairing, not certain as to his choices. I will have to reassess when I pull the boat for next maintanance cycle.

In my 420 years, were let enter a cruising event on long Island sound. Started as a drifter when thunderstorm hit. Skipper and I felt all our hair rise, I got off the trapeze, there was a bright flash and near simultaneous sound, and the cruising class boat beside us was hit. Smoking metal/glass intersections, screaming crew ...then skipper bellows " If I was in heaven you wouldn't be screaming, if I were in hell I wouldn't be sailing...We are sailing! Quiet down and sail! We're still racing! "
We all made it home.

We'll see what the science suggest, but it looks pretty artsy. Also, are we a bit off the curve with our unstayed carbon masts. Not so many stats to guide our choices. If someone does hire an expert and gets an opinion, if they get hit and survive does it prove the system works or attracts lightning? To little data?
Mike
s/v Clave'
1981Freedom 28 #112
Currently sailing Tampa Bay
Buit by Fairways Marine Hamble England
cat ketch, centerboard , wishbone booms, tides track slides
yanmar 2ym15 2blade prop

rbpfyo
Posts: 82
Joined: Sat Nov 15, 2014 7:58 am

Re: hit by lightning

Post by rbpfyo »

would a grounding system attract lightning? I'm guessing yes
would it also help direct the hit it just attracted? I'm guessing yes
but would it also help direct a hit that was going to happen anyway, and lessen the damage to the rest of the boat? I'd guess yes on that too

apparently when a carbon-fiber mast takes a hit, it splits into many 'ribs', like an exploding cigar on a cartoon

also, best thing I've read so far said:
"lightning doesn't take one path of least resistance; it takes ALL the paths; which IS the path of least resistance"

so I'm guessing your vee-berth sleepers would be part of that circuit
just maybe not a big part, especially with a rod-to-ground

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folotp
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Re: hit by lightning

Post by folotp »

Carbon is good electrical conductor. The problem is that the resin is not, and also that the carbon fibres making the mast are not connected to each others. If hit by lightning without proper protection, the heat generated will damage the mast beyond repair and the mast will need to be replaced. The mast exploding like a cigar is an urban legend!

A properly protected mast may have a chance. It needs at least one lightning rod (research is pointing towards more than one), connected to a properly sized down conductor (ABYC says AWG #4 minimum, thought research is now pointing towards 1/0 or 2 AWG as a better size), connected to a proper exit point such as a non encapsulated keel. The Freedom 39 however has an encapsulated keel which cannot be used as an exit point. We thus need a grounding plate of at least 1 square feet (ABYC), more is better.

My mast down conductor (#8AWG) is currently connected to the engine, and thus grounded through the shaft. There are a number of problems with that. The 8 AWG conductor would melt, the 8 AWG jumper wire over the flexible shaft coupling would melt, and there is no telling what those huge currents going through the engine would do (most probably breaking something, leaving the engine unusable). And given I don't have a lightning rod, it is most probably the mast that would be used to carry the current down, leading to it's destruction. And the current would exit where it feels like, most probably via side-flashes, through the water tanks, and then through the hull near the water surface, leaving huge holes in the hull! This is, I believe, the OEM lightning protection on a F39PH, which is why I plan on upgrading it to the most recent NFPA standard for watercraft.

Disclaimer: I am not an expert. This is the current state of my understanding, based on research I have made. I plan on consulting with experts, but have not yet done so.
Pierre-André Folot
s/v “Farfelu” - Freedom 39 PH 1983, hull #14
Sailing the Thousand Islands and Lake Ontario
Canada

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1980raven
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Joined: Mon Feb 15, 2010 8:50 pm
Location: Warwick Cove, Rhode Island

Re: hit by lightning

Post by 1980raven »

I am no expert. While in the process of a 3 year refit of Raven. I read everything I could about LP. I went so far as taking a survey (with binoculars) of the 400 plus sailboats on moorings in Bristol Harbor, Bristol, RI and found that not many (less than 5%) had LP air terminal (lighting rod) at the top of their mast. I decided to do nothing and take my chances. Hope I made the right choice. Time will tell. Wish me luck!
Freedom 28 CK Hull# 14, centerboard, wrap around sails with WB booms
Narragansett Bay, RI

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