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Old 09-01-2012, 14:48   #16
pbr
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Re: Carbon or aluminium mast?

Carbon mast technology is far from new, and well proven. It has been quite reliable in the racing world where it is pushed to extremes a cruiser would never experience or attempt. It is superior to aluminum when it comes to weight for a given moment of inertia. This is why it is being used widely in the aviation industry now, and in the near future all commerical jets will be made of it exclusively. I think it is more than shortsighted to imply it should not be considered in a cruising boat. I can tell you from personal experience it can make a noticeable difference in pitch and roll when comparing two identical boats, all else being equal. Modulus of elasticity in the laminate allows carbon fiber freestanding masts to take tremendous amounts of bend without failure, no different than a modern carbon fiber high quality fishing pole. For me the only downside to consider is cost.
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Old 09-01-2012, 15:06   #17
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Re: Carbon or aluminium mast?

Nobody said it is a new technology. Tripping an open door. Point is dollars and make. Temperature is another item.
Alu got problems too, but: less costly and less harmful. Carbon mast are already used (not widely) in one off's (not production boats as far as I know) so the benefit is there as long as it stays together. The aviation industry is another chapter; when the first plane will come down with full carbon wings we will learn a little bit more of the physical properties. So far, the odds are 50/50.
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Old 09-01-2012, 15:10   #18
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Re: Carbon or aluminium mast?

Note that the OP has a catamaran. Seems to me that weight aloft is less of an issue in these boats than in a monohull, where the weight reduction can make useful improvements in performance, not just tiny increments.

And, he said nothing about unstayed rigs, which have a different set of issues and need to be integrated into the original design of a boat.

And on another point that was raised: while the carbon fibre itself isn't too susceptible to UV radiation, the epoxy matrix certainly is, and spars definitely need to be painted or otherwise protected.

The lightning issue certainly bears thought. I've seen alloy masts that were ruined by a direct lightning strike, but mostly they seem to survive this gross insult. I'd be quite interested in seeing some photos or other direct evidence of carbon masts that were struck... I can easily imagine total destruction from flash heating, but wonder if that really happens.

Cheers,

Jim
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Old 09-01-2012, 15:17   #19
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Re: Carbon or aluminium mast?

I doubt if the aviation industry is willing to bet their future and the lives of their passengers on a 50/50 proposition. Aluminum needs to be painted or annodized just as much as carbon needs to be painted for UV. Lot of production boats with numbers in the 1000's with carbon mast (Melges 24). I have been involved in the production and construction of over 100 catamarans and can tell you from personal experience weight aloft can make a noticeable difference when at sea. It may be more tangible in a monohull relative to righting moment, but cats like to pitch.
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Old 09-01-2012, 15:25   #20
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Re: Carbon or aluminium mast?

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Originally Posted by Jim Cate View Post
Note that the OP has a catamaran. Seems to me that weight aloft is less of an issue in these boats than in a monohull, where the weight reduction can make useful improvements in performance, not just tiny increments.

And, he said nothing about unstayed rigs, which have a different set of issues and need to be integrated into the original design of a boat.

And on another point that was raised: while the carbon fibre itself isn't too susceptible to UV radiation, the epoxy matrix certainly is, and spars definitely need to be painted or otherwise protected.

The lightning issue certainly bears thought. I've seen alloy masts that were ruined by a direct lightning strike, but mostly they seem to survive this gross insult. I'd be quite interested in seeing some photos or other direct evidence of carbon masts that were struck... I can easily imagine total destruction from flash heating, but wonder if that really happens.

Cheers,

Jim
if you really want to know whether lightning is an issue with carbon masts, ring up a big marine insurer and ask if they treat carbon rigs differently to standard ones.

my understanding is that carbon masts cost approx twice an aluminium one. on going costs of a carbon rig may well be lesser. resale may well be higher to offset the initial cost. aluminium masts are generally painted these days because of the environment issues surrounding anodizing - another high and ongoing going cost with alloy masts.
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Old 09-01-2012, 15:26   #21
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Re: Carbon or aluminium mast?

@ pbr - Well they do. Aluminium needs NOT to be painted nor anodised.

Melges is the very wiorst example: if any boat lacks cruising ability is is the Melges boat. I followed AA and know what the internal stratagem of the company is.

BTW no useful explanation on a cruiser' s forum. Please explain the factional benefits of a carbon mast.
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Old 09-01-2012, 15:30   #22
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Re: Carbon or aluminium mast?

as for carbon masts being more prone to damage from impact - whereas an alloy one would dent - i once hit a carbon Weta mast as hard as i could with a hammer - and sure it cracked, but the damage was very localised and the mast wouldve still been useable. whether it could have been repaired economically i couldnt say.

i would imagine that if we were talking 50/60/70ft masts, on that scale i think it would be very difficult to purposely damage the spar in the manner described above.
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Old 09-01-2012, 15:31   #23
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Re: Carbon or aluminium mast?

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@ pbr - Well they do. Aluminium needs NOT to be painted nor anodised.

Melges is the very wiorst example: if any boat lacks cruising ability is is the Melges boat. I followed AA and know what the internal stratagem of the company is.

BTW no useful explanation on a cruiser' s forum. Please explain the factional benefits of a carbon mast.
but most alloy spars are - because most like their boats looking purdy - and then you get the maintenance...
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Old 09-01-2012, 15:40   #24
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Re: Carbon or aluminium mast?

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There's a whole lot of good reasons why one should use a carbon mast (...)
Like what?

I think there is only one good reason: YOU GO RACING and your competitors already have one.

Possible downsides?

- the stick is too light,
- the stick is too custom,
- the stick is too expensive.

Probably some more.

b.
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Old 09-01-2012, 15:40   #25
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Re: Carbon or aluminium mast?

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@ pbr - Well they do. Aluminium needs NOT to be painted nor anodised.

Melges is the very wiorst example: if any boat lacks cruising ability is is the Melges boat. I followed AA and know what the internal stratagem of the company is.

BTW no useful explanation on a cruiser' s forum. Please explain the factional benefits of a carbon mast.
We are not comparing the cruisibility of a given boat design, we are comparing materials for mast construction. A racing design is the best test bed, since they are stressed far more than in a cruising environment. Even the size of the boat dosent matter when comparing the relative differences. It is true you can let aluminum go natural and pit, but I guess you could still build boats out of ferro cement too!

P.S. I dont think AA had anything to do with the design and engineering of aircraft at Boeing.
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Old 09-01-2012, 15:53   #26
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Re: Carbon or aluminium mast?

I am in the process of replacing the unstayed Al masts on my Sea Pearl with carbon fiber from Forte. My motivation is weight aloft and roll moment. Cost is 4x and weight is 1/2. I would not make the same mod on my trimaran because of cost and righting moment of the floats. In a tender boat like the Sea Pearl it should be an improvement worth the investment. Dave
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Old 09-01-2012, 15:57   #27
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Re: Carbon or aluminium mast?

G'Day again all,

This is getting interesting!

PBR: point taken about pitching moment in catamarans. No personal experience, so I will shut up about this!

But alloy masts don't NEED to be painted. It's mostly a cosmetic thing, and certainly improves the spars appearance, especially after a few years of exposure. And I don't think the same is true for carbon-epoxy composites, where UV exposure will break down the epoxy and weaken the structure.

Now, as to the insurance folks: Don't have easy access to that data, but don't think that it has much application to this discussion. To date, most carbon masts are on race boats, and the design parameters for racing spars of any materials are quite different than those for cruising. Further, they are far more likely to be stressed to their design limits in a racing situation. Finally, they are far more expensive to replace than alloy. All of these factors lead me to feel that insurance treatment would not reflect life expectancy of a carbon mast in a cruising application. As they become more common (if they ever do) this may become a useful data source.

So, getting back to the OP query, the downsides of a carbon spar that have been brought up are costs, possible lightning vulnerability, requirements for maintaining paint protection and possible corrosion issues (although I thought that that involved electrolytic corrosion of the spar, not the metal bits).

All in all, I'd not be unhappy to trade my bendy alloy spar for a conservative carbon one... anyone interested??

Cheers,

Jim
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Old 09-01-2012, 16:00   #28
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Re: Carbon or aluminium mast?

Weight is not the only advantage either, for a given moment of inertia, you can reduce rigging aloft required too, further reducing windage .
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Old 09-01-2012, 16:05   #29
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Re: Carbon or aluminium mast?

True Jim, but who wants to deal with the pitting and ugliness of an untreated aluminum spar? Lots of racing carbon spars are clearcoated and seem to hold up, but for a cruising spar Awlgrip or Awlcraft is the way to go, and I doubt you would ever have to touch it again, unlike aluminum, paint adhesion and potential corrosion is not an issue.
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Old 09-01-2012, 16:11   #30
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Re: Carbon or aluminium mast?

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True Jim, but who wants to deal with the pitting and ugliness of an untreated aluminum spar? Lots of racing carbon spars are clearcoated and seem to hold up, but for a cruising spar Awlgrip or Awlcraft is the way to go, and I doubt you would ever have to touch it again, unlike aluminum , paint adhesion and potential corrossion is not an issue.
Do you know anything about the UV absorption of the clearcoat that they use? Might be pretty good... And in truth, for many racing applications, longevity issues due to UV damage may vanish in the dust caused by the mast dying after a flubbed runner set!! Or whatever... but we cheapskate cruisers want something that will outlast us.

I'd still like one (carbon mast, that is).

Cheers,

Jim
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