The Offshore Voyaging Reference Site

Carbon Fiber Masts and Lightning: Myths, Assurances And Risks

Let’s start with the myths:

  1. If a carbon fibre mast gets struck by lightning it is toast, end of story.
  2. If a carbon fibre mast gets struck by lightning, there is no way to tell if it has been damaged or not, so it must be junked.

These two statements are right up there with “drop a penny in the bilge of an aluminum boat and it will burn through in a week”; in other words, rubbish.

I can say this because I have personally seen a carbon fibre mast that was struck by lightning and then pronounced undamaged by a large and reputable mast manufacturer using ultra-sound. And before anyone says that the manufacturer can’t be trusted, do you think that any manufacturer in their right mind would pronounce a mast safe, with the attendant liability, if they were not sure of their methodology?

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More Articles From Carbon Fibre Spars:

  1. The Benefits Of Carbon Fibre Masts
  2. Carbon Fibre Masts, Amateur Boat Design
  3. Carbon Fiber Mast, Costs and Benefits
  4. Carbon Fiber Masts and Lightning: Myths, Assurances And Risks
  5. GMT Carbon Mast, Problems
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Andrew Dawson

John and Phyllis and others, I came accros your expreience with the new carbon mast almost by a happy accident and am delighted with your comments. I am replacing the old aluminium mast (with in mast furling gear on my contest 50 this winter) with a new carbon mast from Hall Spars Holland. The original Alu mast is structurally OK (we hope to sell it and the sail) but I strongly suspect it has been killing the boat’s performance, not so much the speed but the motion of the boat. She pitches and rolls in a seaway especially with a following sea to what I regard as an alarming degree. The mast is 22m high and weighs without the sail, radar etc 560 Kg, so that’s over half a tonne (!!) whereas the new carbon mast (profile much reduced because the new mast has slab reefing) weighs 200 kg, so much more benefit than you achieved.
Time will tell. We step the mast in February adn I will report back.


Hi John,

I have ordered a new sailboat (Luffe 37.09) built by a Danish boatyard with a carbon fibre mast and boom. Since the boat will be sailed in the Med initially they proposed that mast and boom must be varnished white above decks for decreasing heat issues caused by original black colour. Then they told me that the varnishing in white for that reason was a myth. Would you add some comments on that?

Andrew Dawson

Hi Rumen and John. , congratulations on investing in carbon, wish I had insisted on this when I bought the boat. I had a black carbon mast on my racing boat which was clear varnished and used in the UK. Four years later the varnish had peeled off and the thin carbon fibres were coming off making it hazardous to climb the mast and no doubt affecting the strength of the mast. So a good painting is essential in my opinion and yes, very definitely have it painted white. I keep my cruiser in the Med now and it is so hot that a UV absorbing black mast would be a nightmare structurally and otherwise. I cannot recall seeing a black mast at all in any marina in the Med.


Hi John and Andrew,

Thanks for your replies. The manufacturer, Southern Spars claim that clear varnish only is OK.



Thanks John,
I appreciate your point. I will go for the white varnish above deck.


andrew dawson

Talking to the Dutch Hall soars guys they have some carbon masts that need no varnish at all but I would still go white for the reasons John gave….

Markus Gamenius

Hi John

How did you protect the carbon mast against lighting? You say you use both a lightning rod and a static dissipater. I am a little confused, I thought that was the same thing. So I guess I am asking some stupid questions…..

The static dissipater is the “furry” thing on top of the mast. Is the rod the wire that goes from the dissipater to the keel? If so, what kind of lightning rod do you use? And is it glued to the inside of the mast?

Markus Gamenius

Hi John

I am very close to ordering my new mast. I think it will be a Hall mast.

They want to sell me a mast with a dissipater. They are telling me that they only use lightning rods for the really big boats, mast typical 45m high.

Did you order your mast with the lightning rod and the copper cable, ore did you mount it your self?


Markus Gamenius

Twin keels and lightning

My mast are stepped on deck, but is connected to a support under deck that is metal. The keel frame is also metal, but the boat is a twin-keeler, so I guess I have a problem. If the lighting is going down my mast, the support tube (under deck) and in to the keel frame I guess it will go strait out of the hul and in to the water? It would not take a 1meter stepp to the right ore left to pass through one (ore both) of the keels. What do you think?

P D Squire

In a lightning strike “the rigging does the ”heavy lifting””

Any idea how synthetic rigging would perform in comparison with steel?

Also, how much might the weight of a substantial lightning conductor undermine the weight advantage of synthetic over steel standing rigging.

Intriguing ain’t it.