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Old 09-01-2012, 16:26   #31
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Re: Carbon or aluminium mast?

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Originally Posted by maxingout View Post
I would not have it on a cruising boat because of lightning strkes. When I was in Singapore, five yachts were struck with lightning within a single week. I would hate being in a thunderstorm worrying about my mast being vaporized by a lightning strike.
Thats urban legend. My CF mast was struck 3 years ago no damage. Also CF is not prone to UV damage.
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Old 09-01-2012, 16:43   #32
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Re: Carbon or aluminium mast?

Aluminum.
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Old 09-01-2012, 16:46   #33
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Re: Carbon or aluminium mast?

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Originally Posted by SailFastTri View Post
Thats urban legend. My CF mast was struck 3 years ago no damage. Also CF is not prone to UV damage.
SFT,

Glad to hear about your successful survival of a lightning strike.

But, can you show us some support for the claim that carbon fibre is not prone to UV damage? All of the references I'm familiar with say that the epoxy matrix is indeed subject to UV and must be protected.

Cheers,

Jim
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Old 09-01-2012, 17:35   #34
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I bought a cheap pre-loved CF mast for my boat. I will add lightning protection but hope the roughing will handle most of the strike.
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Old 09-01-2012, 17:50   #35
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I bought a cheap pre-loved CF mast for my boat. I will add lightning protection but hope the roughing will handle most of the strike.
iPhones! Supposed to be "rigging will handle the strike".

Is it not accepted that the rigging does this? Not sure how relative conductivities would play out in the real world. Let you know in a year or so cos will be playing in lightning prone areas.

Cost of CF would surely have ruled it out for me except for the lucky purchase of this mast from a CF member. Cost me more to freight it than to buy.
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Old 09-01-2012, 18:19   #36
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Re: Carbon or aluminium mast?

UV is only a problem if the mast has no topcoat. The clearcoat may have UV inhibitors but I'd go for an opaque paint to kill UV penetration completely. You won't get the bragging panache of a clear coated spar but it should last indefinitely. An interesting aside. Heard of one guy who put a carbon spar on his boat and had it painted silver so it would look like an alloy stick. Others have had them painted so they look like a varnished wood spar.

A carbon spar is stronger and lighter than a comparable Aluminum Stick. Both excellent reasons to have one on a cruising boat. Especially since a typical cruising boat will have a lower ballast ratio than a racing boat counteracting the weight aloft. Carbon spars can be made to infinitely different specifications. A cruising spar should be made more robust and stronger than an equivalent sized Aluminum extrusion and still weigh quite a bit less. Carbon spars are just stronger, pound for pound than aluminum. Something that is a big plus for a cruising boat.

Racing spars are typically the minimum possible size for the expected load and often extremely undersize with runnners and multiple spreaders to make up for the light scantlings. Even given that, carbon sticks are stronger. The Antrim 27 was designed with an aluminum stick that seemed to last less than two years of hard racing before they pretzeled. The owners decided to switch to carbon and ended up with a lighter stick that had longevity.

Of course their is the problem of reality. Carbon sticks are more expensive than an aluminum extrusion by a significant number of boat units. For most cruisers, cost will dictate going with Aluminum.

There was a guy who put a carbon stick in a Bermuda 40 probably more than 10 years ago. Wonder if anyone knows of this boat and how the carbon mast has worked out for them. Of course, with a B40, cost probably wouldn't be an issue
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Old 09-01-2012, 18:29   #37
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Re: Carbon or aluminium mast?

How do you drill and tap a carbon mast? Suppose you need to change a steaming light or spinnaker pole guy or even add folding mast steps to assist mast climbing. Will the carbon mast hold a machine screw? I'm just wondering how that is done.
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Old 09-01-2012, 18:34   #38
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Re: Carbon or aluminium mast?

You can drill and tap if you have the wall thickness, if not then the thickness would need to be added to that local area. You can also bond and glass platforms for mounting winches etc. and then drill and tap.
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Old 09-01-2012, 19:06   #39
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Re: Carbon or aluminium mast?

Good. a chance to showcase my ignorance with some questions...
I thought of changing to PBO rigging but it wasn't just the expense that stopped me.
The motion of the older design alu stick boat is going to change w a carbon mast but I am not convinced it would be for the better particularly with a more traditional heavy displacement double ender like mine.

Wouldn't the motion be quicker... as would be the case with the pitch of a boat as you shift the eight out of the ends? If I understand this particular idea properly the reason one would tolerate this sort of faster pitching motion is for safety: the pitch is not as deep and returns quickly so the vessel does not stay long at a deeper angle thereby being exposed for long to a boarding sea... long enough to jepordize the vesel.

Now with a much lighter stick isn't the motion quicker therefore less comfortable? As I understand it a quicker righting moment is a great benefit for a racing boat and a lighter stick means that a safer, shallower righting"arc" for a more "tender" boat.

Sooo like all this sort of thing it's a trade-off right? In both cases (weight in the ends and/or weight aloft) a quicker shallower motion that can enhance safety at the cost of a slower more comfortable motion (a low priority for a race-boat).
But losing weight aloft and the monohull motion that results is a better trade-off for race boats because it means enhanced performance, especially 'round the buoys and most likely even greater safety in a roll.

Since my heavier boat is designed for comfort over speed I decided to forego the weight change aloft and will add foam to the stick as an extra safety precaution in the case of a roll.

Was that clear as mud or what...
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Old 09-01-2012, 19:35   #40
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Quote:
Originally Posted by Butler
Good. a chance to showcase my ignorance with some questions...
I thought of changing to PBO rigging but it wasn't just the expense that stopped me.
The motion of the older design alu stick boat is going to change w a carbon mast but I am not convinced it would be for the better particularly with a more traditional heavy displacement double ender like mine.

Wouldn't the motion be quicker... as would be the case with the pitch of a boat as you shift the eight out of the ends? If I understand this particular idea properly the reason one would tolerate this sort of faster pitching motion is for safety: the pitch is not as deep and returns quickly so the vessel does not stay long at a deeper angle thereby being exposed for long to a boarding sea... long enough to jepordize the vesel.

Now with a much lighter stick isn't the motion quicker therefore less comfortable? As I understand it a quicker righting moment is a great benefit for a racing boat and a lighter stick means that a safer, shallower righting"arc" for a more "tender" boat.

Sooo like all this sort of thing it's a trade-off right? In both cases (weight in the ends and/or weight aloft) a quicker shallower motion that can enhance safety at the cost of a slower more comfortable motion (a low priority for a race-boat).
But losing weight aloft and the monohull motion that results is a better trade-off for race boats because it means enhanced performance, especially 'round the buoys and most likely even greater safety in a roll.

Since my heavier boat is designed for comfort over speed I decided to forego the weight change aloft and will add foam to the stick as an extra safety precaution in the case of a roll.

Was that clear as mud or what...
Well, as mine is a medium displacement double ended hull too we are probably inappropriately diverting this multihull thread.

I processed your thoughts and anxieties and decided to give the CF a go thinking that my bigger boat will probably forgive this sort of tampering. Pretty much designed by eye anyway.

I reckon the saving in weight aloft is the primary consideration and lets me carry more sail on an admittedly less than gazelle-like design. May mean more reefing for heavy weather but better light air performance which is probably majority of sailing.

Quicker motion not likely to be big issue in this boat I reckon. Let you know soon.
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Old 09-01-2012, 19:53   #41
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Re: Carbon or aluminium mast?

The loads on a mast in general are compressive. Carbon excels in tensile strength, not the opposite way. Reason using carbon is saving weight: anything that can saved above the waterline can be used in the ballast. Which means more SA so the powernumbers might increase substantially.
Carbon comes in many (quality) strength grades. Just like the matrix materials.
The unique spec of a carbon mast is not only the weightfactor but also its stiffness. The stiffer the mast, the faster the boat will move.
Nonetheless I look at the racing bikes used in the "Tour the France". Absolute the best of the best materials. They collapse at any (unwanted) moment. Those racers say "Carbon is Carton" ......
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Old 09-01-2012, 20:29   #42
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Re: Carbon or aluminium mast?

What is the actual wieght differace between a carboon fiber mast and an aluminum mast of the same height for the same rig. Wire is not really that heavy, there is more concern with windage, though CF masts are alot bigger. I just replaced all my standing rigging and figured out how much my wire actually weighed ...on my boat 1/4" 7x19 316ss lowers, intermediates, cap shrouds,head stay, top stay, back stay= 295' at .11lbs/ft= 32.45lbs (plus spectra running back pennants). My mast is laminated Sitka spruce, basically a solid 47' (stepped on keel) cambered and tapered stick.
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Old 09-01-2012, 20:36   #43
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One big benefit is that you can put on a taller mast, and larger mainsail,, and have identical stability and heeling with more power due to lighter mast. It would probably take a naval engineer to figure out the balance point in terms of added rig, but you can add sail area if you calculate well.
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Old 09-01-2012, 20:53   #44
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Re: Carbon or aluminium mast?

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I never wen masts were impervious to lightning....just metal conducts electricity better.
But the shrouds/stays are metal and they are right up there at the top with the rest of the junk. Nothing against wood, just saying..........
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Old 09-01-2012, 21:17   #45
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Re: Carbon or aluminium mast?

Lightning was never an issue with me, I lie my wood masts for other reasons.

BTW sorry I didn't know this was a mulihull thread, I have a heavy disp. old school ocean cruising mono hulll
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