Carbon fiber mast on a cruiser?

[maxingout]

When we were in Singapore at the start of Monsoon season, five cruising yachts were struck by lightning within one week. That got my attention, and settled the question as to whether I would have a carbon fiber mast.

We went through lots of impressive thunderstorms during our circumnavigation, and lightning is simply a fact of the cruising life.

If I had a coastal cruiser that was never far from civilization, then carbon would not be an issue. But for blue water cruising in remote areas, carbon does not work for me.

[billgewater]

Must confess, I have not seen the carbon fibre mast as it has been removed from the cat. This was a very big mast, probably close to 70 ft. But the marina gossip is that it has been declared a write off. I guess the mast would have cost in the vicinity of $200000 AUD.

However, if insurance companies don't distinguish between carbon and alloy masts, then maybe it doesn't really matter. Although I would be surprised at this ambivalence due to the phenomenal price difference.

There may well be installation and engineering conditions that are unique to carbon fibre rigs that were not addressed in the catamaran where this happened.

To me it seems that an alloy mast is less likely to be damaged by even massive currents except at small cross sectional areas such as, say, rigging screws. Carbon fibre just has very different electrical resistance properties.
Using Dyneema or other synthetics in the rigging also means fewer low impedance electrical pathways. Food for thought and possible caution.

Some years ago, i came across an article by a marine electrician who observed that electrical strikes were more relatively frequent on catamarans than for monohulls. His observation was that this may well have been due to the fact that with two saildrives or props. in the water, connected electrically to the ships earth then a greater electrical plane was present. Just his musings.
In Darwin some years ago, lightening hit a yacht in our marina. I was on my own deck nearby and nearly s..t myself. I went down to the hit yacht to see that the mast head light, the antennae and wind direction finder on the mast head had "vapourised". But what was interesting was the smoke coming out of the deck electrical anchor winch. I knew they had a problem.
Strangely, they got hit again a year or so later.

[daysgoneby]

Attainable Adventure Cruising has a section on carbon mast

https://www.morganscloud.com/series/carbon-fibre-mast/

[Stumble]

Bilgewater,

There is no actual evidence that carbon masts sustain more damage from lightning than aluminium, nor is there generally any insurance hit for insuring a carbon mast over aluminium (and there should be if there was a history of excess damage). Mast builders like Hall are pretty definitive that there is no reason to stress over it, and inspecting for damage after a lightning strike is pretty easy.

In short, despite a lot of reasonable concerns that were floated early in the days of carbon rigs, none of them have really been born out.

As for price... The difference really depends on the size of the mast. For small masts where shipping is a major portion of the cost of a new mast the difference can be negligable. So very large masts the total cost of a carbon mast can be less because of the advantages that come with lighter weight. The middle is complicated, in the ~40' range of boats the masts will generally be 30-50% more expensive.

But very technical masts made with ultra stiff carbon like what's used in AC boats can be orders of magnitude more expensive.

[Paul L]

I don't know if they charge any difference on their policies, but at least one insurer thinks CF and Wood masts do less well in lightning strikes.

Fortunately, the BoatUS Marine Insurance claim files have not shown that aluminum masts themselves get damaged; aluminum is a very good conductor and allows the strike free passage. However, wood and carbon fiber masts can get damaged since neither one is a good conductor.

This was discussed this forum awhile ago http://www.cruisersforum.com/forums/...ast-74224.html

[stillbuilding]

Not a difficult task to run a copper grounding strap from top of the CF mast down outside or thru interior of mast to hull. Takes a bit of googling but it is all out there from design, fabrication, connections etc. There are many excellent pics of good design. With this in place a CF mast and alloy mast are essentially identical.


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[TheThunderbird]

CF works well only on compression/tension along fibers

In order to limit slack, and flexibility, that which induces bending, that high compression tensile capability is mostly exploited. THIS linear stress minimizes cracking under slack bending (one word, Elasticity is Undesired with CF)

Not to say, that design and stress calculations on composite materials is quite empirical... (test, break, re-inforce where broken...)

Never bend CF !

Consequently..... (mech. Eng.) anyone may draw conclusions

[Stumble]

Originally Posted by TheThunderbird

CF works well only on compression/tension along fibers

In order to limit slack, and flexibility, that which induces bending, that high compression tensile capability is mostly exploited. THIS linear stress minimizes cracking under slack bending (one word, Elasticity is Undesired with CF)

Not to say, that design and stress calculations on composite materials is quite empirical... (test, break, re-inforce where broken...)

Never bend CF !

Consequently..... (mech. Eng.) anyone may draw conclusions

I don't know how many carbon masts you have dealt with, but every single one of the ones I have owned and sailed on we're designed to flex. I know all of the ones built by Hall Spar are as well. In fact I don't know of a single carbon mast that was designed to flex. Because part of what makes carbon masts so desirable is that the amount of flex can be designed in.

A heavy boat that's very stiff will carry a stiffer mast, while a lighter more tender boat will be designed to bend off as a gust hits and depower the boat. So the boat can automatically depower in gusts.

In the same way carbon battens are designed to bend off at a specific load in order to depower the sails predictably.

If CF could never be bent then you have an entire industry of fishing rods and golf clubs that will need to reevaluate their products.

[GoingWalkabout]

In my business we do various materials testing for our products. While not boat related at all the training in material science came in handy when I made a study of carbon fibre masts. Just as an aside I have done work on carbon nanotubes for rapid DNA sequencing but that again is something else.

My research has lead me to understand that carbon masts after taking a lightning hit can suffer substantial damage internally which is not visible externally. And when I say suffer internal damage I'm talking about it being so bad that if you were way offshore you would be in deep trouble.

I would never cross the Atlantic for instance in a vessel with a carbon fibre mast. Sailing where you can safely motor in is a different question. But for long distance ocean passage making knowing what I know I would never do it with a carbon mast. But this is only my opinion which is only based on theoretical analysis.

[tkeithlu]

What it means is that we don't have good data on carbon versus aluminum in a lightning strikes. There are too many variables and too few data points. I would not consider the consequences of a very unlikely (ergo, not enough data) lightning strike in your decision.

[GoingWalkabout]

Originally Posted by tkeithlu

What it means is that we don't have good data on carbon versus aluminum in a lightning strikes. There are too many variables and too few data points. I would not consider the consequences of a very unlikely (ergo, not enough data) lightning strike in your decision.

What is known is that carbon masts do suffer catastrophic damage when hit by lightning. What we also know is if they don't explode they can suffer internal structural damage that isn't visible from the outside.

Knowing what we do know it would be irresponsible sailing a used carbon masted sailboat long distance offshore. Especially if you have no idea if the stick has ever been hit before.

But go ahead, tell others to throw caution to the wind. After all your not convinced that there's nothing to worry about so what the heck, tell everyone else to go and use CF second hand mast.

As I said before, I for one would not travel an ocean with such a mast.

[Stumble]

What we actually know is that a carbon mast can, but is incredibly iunlikely to, suffer catastrophic damage from a lightning strike. Which is why every carbon mast on a voyaging boat has a lightning conductor to prevent exactly this type of damage. Further we know that when these conductors are in place the likelyhood of damage is remote approaching zero.

It is also relatively easy to inspect a carbon mast that has been hit with a rubber mallet and a little bit of time. If they are damaged the damage is easily identified by the change in the sound. Or in extreme instances by using ultrasound testing. Either of which are cheap and easy ways to test the mast.

Finally there is the reality that almost all large boats being built today intending to cross oceans are using carbon. None of which have a track record of loosing their masts because of lightning strikes. You are more likely to blow a thru hull out of your hull thanks to a lightning strike than you are loose a carbon mast because of one.

[TJ D]

We have a carbon mast. Love it. Way lighter than an alu stick, keeping the boat's CG lower, RM higher. We can carry more sail for a given amount of heel, rolling is reduced, and never mind the contention that you shouldn't bend carbon, it's very flexible when we want it to be. Crank on runner, depower main.

We have a Hall mast, by the way.

CF is not a new material for this application. Ours has sported a CF rig for 20 years.

Lightning, yes, it is more susceptible to damage than aluminum, but honestly, that's why we carry insurance. The bottom line is that if you get a direct hit on any boat, there is most likely going to be enough damage to other systems that you're not going to simply be able to just keep merrily cruising along because you have an aluminum mast anyway. It'll just be another item to repair. We do sail to remote places, by the way.

I wouldn't worry about it, as long as it's all thoroughly checked by a rigger who knows the material.

Remember, the same people who are resistant to new materials are pretty much the same people who a generation ago were against roller furling, refrigeration, etc, etc. Carbon is very well proven at this point. Lighting is another matter, but it's definitely not a given that it's trashed with a strike.

Good sailing, TJ

[Paul L]

Originally Posted by TJ D

We have a carbon mast. Love it. Way lighter than an alu stick, keeping the boat's CG lower, RM higher. We can carry more sail for a given amount of heel, rolling is reduced, and never mind the contention that you shouldn't bend carbon, it's very flexible when we want it to be. Crank on runner, depower main.

We have a Hall mast, by the way.

CF is not a new material for this application. Ours has sported a CF rig for 20 years.

Lightning, yes, it is more susceptible to damage than aluminum, but honestly, that's why we carry insurance. The bottom line is that if you get a direct hit on any boat, there is most likely going to be enough damage to other systems that you're not going to simply be able to just keep merrily cruising along because you have an aluminum mast anyway. It'll just be another item to repair. We do sail to remote places, by the way.

I wouldn't worry about it, as long as it's all thoroughly checked by a rigger who knows the material.

Remember, the same people who are resistant to new materials are pretty much the same people who a generation ago were against roller furling, refrigeration, etc, etc. Carbon is very well proven at this point. Lighting is another matter, but it's definitely not a given that it's trashed with a strike.

Good sailing, TJ

Rational middle of the road position that deals with the benefits, the risks and mitigating the risk with insurance.

[neilpride]

I'm a rigger and I can say CF is well proven and have lots of benefit in a cruising boat, just be sure the mast is built by a reputable sparmaker since I see lots of junk made in CF with the associated risk, driiling and taping CF is tough and add gear is a bit tricky ,anyway its a good material for the rig , just be sure you get a reputable rigging surveyor and if is sound, congratulations.....