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Old 05-07-2015, 21:17   #31
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Re: Is current carbon tech safe?

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Originally Posted by IdoraKeeper View Post
Very interesting. Thank you for the exposition. It is my understanding that there are also non autoclave structures in CF coming into use. Additionally there is the matter of electrical conductivity being different for carbon vs glass.
You are correct on both points. CF is highly conductive. But not so much when compounded with epoxy. Also the greater the temperature used in the making of the CF the greater the resultant electrical conductivity of the material. This is another very exciting field of applied research. Using graphene traces at nano level to draw a circuit that would otherwise have been drawn on a silicon wafer. It has been discovered that the graphene based circuited achieves exceptionally faster speeds compared to silicon. This also is very close to coming out of the labs into the real world and when it does it is going to blast past mores law. Monumental change is coming. This is what really excites me along with the dreams at night about my journeys into the far off oceans.
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Old 05-07-2015, 21:53   #32
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Re: Is current carbon tech safe?

Adding carbon as a protective shield is probably never going to happen. Wrong material for the job. For something like is what you want is the ability to take strong impacts over and over again. CF is absolutely the wrong material for this. A SS plate can take the abuse, and if it does get hit, worst case it will deform a little and could be pulled off and replaced.

Since it isn't subject to stress you don't even have to worry about corrosion much. If you really want to go high tech you could switch over to titanium, but I don't see much advantage to be honest. Other than a minimal weight savings and increased corrosion resistance.
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Old 05-07-2015, 22:20   #33
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Re: Is current carbon tech safe?

Everyone seems to have missed the biggest drawback to the use of carbon fiber in hull construction. Actually, it was very obliquely touched on in a previous post and that is the issue of its conductivity. A lightning strike will absolutely f__k up a cf hull (or mast) to the point of rendering it useless. The individual fibers will suffer varying degrees of destruction (vaporization) along the lightning's path and it isn't readily apparent from the outside.It is one thing to have an insulation breakdown and have a hole blown through fiberglas which can be seen and fixed. It is another altogether to have the internal structure of the material "rotted out" from plasma effects. Lightning suppression is tricky enough on a boat without giving it CF to play with.

Just my opinion, of course. Even if the price of CF were dirt cheap I wouldn't use it for a hull on a cruiser or live aboard. YMMV
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Old 05-07-2015, 22:45   #34
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Re: Is current carbon tech safe?

Regarding lightning, it's a good point. But, a direct lightning strike can wreak absolute havoc on any kind of boat, if not the hull, then all the systems, which can add up to nearly the cost of replacement of the vessel by the time one's done getting it all sorted.

But, the point is still a valid one. We cast a more wary eye toward that rumbling squall than we used to. I have considered doing the jumper cable from the cap shroud into the water scheme, but I really doubt that would do much. Probably if we had a severe strike, we would end up with an insurance claim for a constructive total loss. In our case, we are never without insurance, so it is less of an issue in our minds. I don't think that a CF boat is any more likely to sink as a direct result of a strike than a GRP one.

Anyway, you pays your money and you takes your chances in this life! We still love the material.... To each their own.

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Old 06-07-2015, 07:38   #35
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Re: Is current carbon tech safe?

I am convinced that lightning will do whatever it wants. Material choice doesn't change that. But since CF doesn't seem to have a higher lightening induced failure than fiberglass who cares. If you take a direct hit your boat is likely totaled, unless it isn't.
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Old 06-07-2015, 08:49   #36
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Re: Is current carbon tech safe?

I didn't say that a lightning hit on a CF hull boat would sink it. I said that there is almost no way of knowing what damage was done by the strike to the internal structure of the hull. It has everything to do with the vaporization (or lack thereof) of the individual conductive carbon fibers in the matrix. One cannot usually tell from looking with CF. I also said I would not use CF in a cruising or live aboard boat mainly for that reason. CF masts have the same issues. Strong, light, beautiful and conductive. Aluminum masts are conductive but they aren't made of a bundle of conductive fibers that can be selectively destroyed by lightning.

GRP, on the other hand, being an insulator, will definitely let you know when it has failed due to lightning. No guesswork, no expensive testing, just raggedy-assed holes.

As for lightning suppression techniques to use on a boat, there have been several excellent articles (and books) written on the subject. In essence one creates a faraday cage (electrical shield) to protect everything inside the cage and then give the charge a place to go (hint: a wire or plate in the water doesn't suffice). Side-flash discharge thru-hull electrodes about a foot above the water line around the boat properly tied into the faraday shield work very well. Properly bonding metal tanks and other metal items to the shield is a no-brainer.

A lightning caused EMP pulse event can still destroy electronics but a faraday shield will reduce the amplitude of the pulse and, just maybe, not destroy as much AND the shield can help keep an occupant from being fried. Again, YMMV.
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Old 06-07-2015, 18:55   #37
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Re: Is current carbon tech safe?

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All jokes aside. I really would like to know the actual composition of the carbon formula being used by the mast makers. As I noted before carbon has in intrinsic brittleness so I would like to understand what has been done to compensate or overcome this. Not being assured on this issue would steer me away from purchasing a boat with a carbon mast. Just because something is fashionable doesn't mean it its the best.
Carbon Fiber is pretty much carbon fiber. Probably most is made by the same manufacturer(s). The tech is the lay-up and matrix material and, as noted above, the curing oven & process.

Masts can be spun on mandrel or lay-up from pre-preg or hand lay-up. The orientation of the fibers is the most important mechanical contributor and has to be done right. The next most important feature in the process is the reinforcement density, that is, the fibers need to be compressed together so that the minimum resin matrix by volume results. This gives the highest Young's modulus, highest strength to weight ratio. Maximizing this can only be achieved using a vacuum bagging process or other compression molding process. Modern resins designed for this achieve their strength by heat curing at the right temperature. Pre-pregs only cure at elevated temperature. This is why the big boys hire NASA and the aircraft makers to make masts or high end hulls.

Consider also the modes of failure. An aluminum mast crumples and caves in at the spreaders. A carbon mast shatters, leaving not much. It can be dangerous as well. If you are in mid ocean, you might have enough aluminum spar to get home. If its carbon fiber, chances are slim. If you are not engaged in high end racing, I see no reason to mess with high tech. If you are into the tech you are not interested in shopping on price. Be prepared to look for the best from a known builder only.

One thing that is a totally unknown factor is the probability of lightning and what it might do to a carbon hull. Any data on this one? Carbon also offers some odd twists on galvanic coupling.
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Old 06-07-2015, 20:38   #38
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Re: Is current carbon tech safe?

Nicholson,

Almost all large boats (say >70') have switched to carbon masts. The price premium is becoming less, the masts can be made stronger, lighter, safer, and much easier to trim properly. For the same size a CF mast will be about 50% the weight, and much stronger. A properly engineered CF mast will also taper towards the top where loads are lower, and be larger at the bottom where they are higher. An extrusion has to be the same size from top to bottom, which obviously effects weight. Less obviously the weight savings at the top of the mast also increase the boats AVS, reduce roll period, reduce heel, increase heavy air performance, and light air performance.

Just as an example... On my boat if we had a CF mast instead of aluminium it would shave about 100lbs from the rig, for a RM increase of 2500ft-lbs. that's the equivilant of almost 500lbs hiked out on the rail all the time.

And again... There is no reason to believe that CF masts have an increased damage potential from lighting. Which is why there is no premium (other than replacement cost of course) to having a CF mast.
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Old 06-07-2015, 21:33   #39
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Re: Is current carbon tech safe?

Before I bought my now 27-year-old Freedom, I researched anything that could be found on failure of CF masts. I recall reading one instance of a Freedom being rolled -- the mast stayed intact -- but nothing about a direct hit from lightning. There have been problems on some of the masts related to the original layup resulting in unsightly spider lines, which can be corrected. There's no shortage of conjecture on the internet, but I feel completely confident in saying that CF masts fail as a small percentage compared to stayed rigs. When I lost my forestay in 24 knots on SF Bay, I just kept on sailing...not too many other boats can do the same. I am also seeing friends building CF booms for their boats so it's just a matter of time (probably another 10 years) before most boats are made with carbon masts and booms.

No offense, but the OP seems to have a lot of angst over nothing
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Old 07-07-2015, 00:42   #40
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Re: Is current carbon tech safe?

There is in fact evidence that carbon fiber is more conductive than aluminum. This a without dispute. From further analysis where even a small piece of carbon is exposed or is hit directly by lightning piercing through the epoxy bond then touching the carbon you will have an immediate conduction throughout all interconnected carbon causing disintegration. The composite used to bond the carbon fiber is important but from my understanding it has very low conductivity. This provides insulation for the encapsulated carbon however lightning can well pierce the compound and travel through the highly conductive carbon fibers. And yes this will destroy the mast.

I found this engineering observation from a 2009 posting on carbon masts on another site interesting.

"One of my friends did Mech eng in the uk where they have a vandergraph that can create lightening type sparks and tested carbon masts with a vendor.
They found if the mast was completely covered in epoxy and no carbon exposed, the mast usually survived BUT if the spark can get to a fibre it will burn it and move to the next and so on very quickly so you end up with a tube of epoxy and no carbon.
This was very plain on a section that was cut through with no crane and japped. They filmed it and you could see the spark jumping around.."


Another interesting comment by a boat engineer.

"Carbon fibre is now commonly used on wing masts, but the main problem with this material is that it reacts very badly to aluminium in salt water. This means the sail track etc should be made in carbon as well, which is tricky to do. A word of warning, if you do have a carbon mast paint it white, otherwise the epoxy will be degraded by UV within two years and your mast will break! Furthermore it is essential that you fit a good lightning protection system. A metal mast will probably survive a direct lightning hit, a carbon mast probably will not."

So I'm swinging back and forth between older aluminum masts and lighter and stiffer composite carbon fiber masts. I now realize that a cat is more than double the odds of being struck by lightening than a monohull. I also realize that you can take precautions and you should, but you can not defeat lightening if it chooses your boat. You need to be prepared to loose all of your electronics and if your lucky you don't have to deal with a hole in your boat or a complete dismasting.

So what is a person to do if they are planning like me to travel across oceans? First I am leaning against having a carbon mast. As one poster contributed a bent aluminum mast is better than a destroyed carbon mast. At least you could try and rig a sail from the remnants of the aluminum mast. Important if you are 1000 nm from land. Another thing I'm thinking about is to have a sexton and learn how to use it.

Some how I wished I never even thought about the structure and science of carbon masts.
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Old 07-07-2015, 03:28   #41
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Re: Is current carbon tech safe?

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Consider also the modes of failure. An aluminum mast crumples and caves in at the spreaders. A carbon mast shatters, leaving not much. It can be dangerous as well. If you are in mid ocean, you might have enough aluminum spar to get home. If its carbon fiber, chances are slim.
My brothers carbon mast on his 28 trimaran collapsed due to either a manufacturing fault, or previous damage (it was a cut down broken mast from a bigger mono). It broke very cleanly and was quickly repaired. He's still winning races with it. Also I think it as Yves Parlier (sp?) Who rebuilt his carbon wing mast at anchor in Stewart island during the vendee globe race. So it seems like you may have something useable left after a failure?



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Old 07-07-2015, 03:54   #42
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Re: Is current carbon tech safe?

Another brothers was aboard Hugo boss when her carbon mast dropped. http://www.thedailysail.com/offshore...gged-hugo-boss

Also interested to hear how the new composite aircraft cope with lightning?

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Old 07-07-2015, 05:06   #43
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Re: Is current carbon tech safe?

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... Also interested to hear how the new composite aircraft cope with lightning?
Typically composite aircraft have conductive material added to the composites for Lightning Strike Prevention, such as a copper mesh included in the layups. In most places the 787, for instance, uses a wire mesh, but in some extremities (wingtips, nacelles, tails) metal foils are used instead.

Lightning strike protection strategies for composite aircraft
Lightning strike protection strategies for composite aircraft : CompositesWorld
http://www.dexmet.com/1_pdf/LSP%20fo...20Aircraft.pdf
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Old 07-07-2015, 06:31   #44
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Re: Is current carbon tech safe?

Very interesting Gord, thanks for the links. Reassuring to know how much testing goes into aircraft.

I guess the ultimate carbon mast will end up with some of that paint on conductive bog or expanded mesh overlay.

Looking forward to the day carbon masts become affordable, so many benefits for anybody that enjoys a boat that sails well.

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Old 07-07-2015, 08:55   #45
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Re: Is current carbon tech safe?

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You are correct on both points. CF is highly conductive. But not so much when compounded with epoxy. Also the greater the temperature used in the making of the CF the greater the resultant electrical conductivity of the material. This is another very exciting field of applied research. Using graphene traces at nano level to draw a circuit that would otherwise have been drawn on a silicon wafer. It has been discovered that the graphene based circuited achieves exceptionally faster speeds compared to silicon. This also is very close to coming out of the labs into the real world and when it does it is going to blast past mores law. Monumental change is coming. This is what really excites me along with the dreams at night about my journeys into the far off oceans.
Interesting! It sounds about the same as vacuum tubes to transistors, or transistors to chips.
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