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Old 07-07-2015, 08:59   #46
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Re: Is current carbon tech safe?

Carbon fiber hulls have been around for at least 10 years that I know of. I would think that naval architects have a good sense of the strengths and weaknesses of the material by now....basically they have a good idea of the scantlings necessary to make a safe and reliable boat.
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Old 08-12-2015, 21:23   #47
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Re: Is current carbon tech safe?

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Carbon fiber hulls have been around for at least 10 years that I know of. I would think that naval architects have a good sense of the strengths and weaknesses of the material by now....basically they have a good idea of the scantlings necessary to make a safe and reliable boat.
Just because a carbon hulls are used doesn't allay my concerns regarding carbon fiber masts. Intrinsic brittleness along with conductivity and total destruction if hit by lightening.
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Old 09-12-2015, 01:43   #48
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Re: Is current carbon tech safe?

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Originally Posted by 44'cruisingcat View Post
So my plan to build my next boat from pencil leads is flawed?
pencils have been something else for quite some time!
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Old 09-12-2015, 01:45   #49
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Re: Is current carbon tech safe?

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Just because a carbon hulls are used doesn't allay my concerns regarding carbon fiber masts. Intrinsic brittleness along with conductivity and total destruction if hit by lightening.
i am 100% agreed with you, ive dealt with carbon fiber and i would prefer my boat or mast was not made of it ;]
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Old 09-12-2015, 10:49   #50
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Re: Is current carbon tech safe?

This silliness again....

Carbon rigs have been around for a very long time and during that time have an excellent safety record. Assuming they are properly designed a carbon stick will last forever.

This entire thread is an omage to someone who doesn't like a material for some weird personal reason, and has found some esoteric engineering reason he doesn't really understand to justify that dislike.

Carbon masts are no more likely to fail due to lightning strikes than aluminium masts are. I both cases they are likely to be destroyed unless well bonded.

And carbon masts are not brittle. Go actually look at any modern racing catamaran and watch how far they are bent to shape sails. Or a carbon fishing rod, or carbon battens, or pretty much anything made from carbon and designed to flex.
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Old 09-12-2015, 13:36   #51
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Re: Is current carbon tech safe?

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Is current carbon tech safe?
Well, that depends on what you mean by 'safe". If it means guaranteed to never fail no matter what, then of course it isn't safe.

But the same can be said for aluminium or timber masts, and for FRP, steel, Aluminium or timber hulls, and so on. They all have failure modes and can be poorly designed, fabricated or maintained to the point where they succumb to those modes.

As Greg says above... carbon rigs have been successfully used for years. Most of the few failures that I am aware of were i n race boats where design to the limits is normal, and driving past the limits is considered a good practice. If you intend to cruise like that, well, good luck!

Conservatism in cruising is laudable, but paranoid fears are crippling. A balance should be achievable, especially with experience.

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Old 09-12-2015, 13:54   #52
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Re: Is current carbon tech safe?

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Originally Posted by Stumble View Post
This silliness again....

Carbon rigs have been around for a very long time and during that time have an excellent safety record. Assuming they are properly designed a carbon stick will last forever.

This entire thread is an omage to someone who doesn't like a material for some weird personal reason, and has found some esoteric engineering reason he doesn't really understand to justify that dislike.

Carbon masts are no more likely to fail due to lightning strikes than aluminium masts are. I both cases they are likely to be destroyed unless well bonded.

And carbon masts are not brittle. Go actually look at any modern racing catamaran and watch how far they are bent to shape sails. Or a carbon fishing rod, or carbon battens, or pretty much anything made from carbon and designed to flex.
Well stated!
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Old 09-12-2015, 14:22   #53
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Re: Is current carbon tech safe?

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Originally Posted by Jim Cate View Post
Well, that depends on what you mean by 'safe". If it means guaranteed to never fail no matter what, then of course it isn't safe.

But the same can be said for aluminium or timber masts, and for FRP, steel, Aluminium or timber hulls, and so on. They all have failure modes and can be poorly designed, fabricated or maintained to the point where they succumb to those modes.

As Greg says above... carbon rigs have been successfully used for years. Most of the few failures that I am aware of were i n race boats where design to the limits is normal, and driving past the limits is considered a good practice. If you intend to cruise like that, well, good luck!

Conservatism in cruising is laudable, but paranoid fears are crippling. A balance should be achievable, especially with experience.

Jim
Hi Jim, I am over in Salt Pan Cove, will wave hello!

All the failures I have heard of are the result of extremes, either stress due to forces beyond the design, or specific damage.
The core problem is the main users of Carbon Fibre are those after the extreme strength and weight savings. Race cars (and boats) are built to the minimum strength thought necessary. They are built for that one race (or series) in the extreme cases and are expected to fail beyond that. Most GRP is built in a more forgiving manner, because the design is less specific to individual stresses. GRP, especially with chopped strand mat is a little vague, so gets more general strength. We use the carbon fibre when we think we understand the stresses and can engineer the item accordingly. Yes, it goes wrong occasionally, but we are getting better each time.
Damage causes stress lines, they can be designed for if properly predicted but such prediction is hard. The trick is therefore to add margins to allow for random stresses - without going mad and adding too much weight.
The other trick is - use a material that suits your needs, if you want durability under all conditions, then pick a more forgiving material. If you want the ultimate light weight high strength, predictable flexion but not especially forgiving to damage, then you have materials such as carbon fibre/epoxy.
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Old 09-12-2015, 15:21   #54
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Re: Is current carbon tech safe?

This summer I wrapped the CF spinnaker pole around the front beam of our Pdq 36 (don't ask). The pole did not shatter as much as I expected .The damage was contained to a reasonable area. It has now been repaired. The dagger boards are also carbon and have been used in very rough conditions fully deployed and have not failed. I wanted a carbon spar but even in 2003 the bare pole was 32000 $. If I could afford it I would go carbon all the way.
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Old 09-12-2015, 16:19   #55
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Re: Is current carbon tech safe?

Carbon, especially masts has been around for way more than 10 years. I used to race on a 2000 model year production boat with one that was struck by lightning. Expected damage to instruments, no damage to mast, it is still in one piece and in use 15 years later (did require new clear coat a year or so ago).

Also raced on a maxi that was all carbon, including mast. 5 spreader fractional rig. Almost too flexible!

Down side remains cost, not the reliability of the material.


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Old 09-12-2015, 21:34   #56
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Re: Is current carbon tech safe?

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Originally Posted by Djarraluda View Post
Hi Jim, I am over in Salt Pan Cove, will wave hello!

All the failures I have heard of are the result of extremes, either stress due to forces beyond the design, or specific damage.
The core problem is the main users of Carbon Fibre are those after the extreme strength and weight savings. Race cars (and boats) are built to the minimum strength thought necessary. They are built for that one race (or series) in the extreme cases and are expected to fail beyond that. Most GRP is built in a more forgiving manner, because the design is less specific to individual stresses. GRP, especially with chopped strand mat is a little vague, so gets more general strength. We use the carbon fibre when we think we understand the stresses and can engineer the item accordingly. Yes, it goes wrong occasionally, but we are getting better each time.
Damage causes stress lines, they can be designed for if properly predicted but such prediction is hard. The trick is therefore to add margins to allow for random stresses - without going mad and adding too much weight.
The other trick is - use a material that suits your needs, if you want durability under all conditions, then pick a more forgiving material. If you want the ultimate light weight high strength, predictable flexion but not especially forgiving to damage, then you have materials such as carbon fibre/epoxy.
If you want durability you still go with carbon fiber, you just use a different design than a boat that wants ultimate performance. If you increase the laminate stack thickness enough you can have a mast you could beat on with a sledge hammer without damage. It would weigh a lot, but it's certainly possible. 100' long wind turbine blades are made from carbon and routinely hit 2lb birds at 40mph with no damage, at least to the blades the birds turn into mist.

To clear up a little confusion, extra layers of CSM add little to the strength of a part. At best the extra thickness adds stiffness at the cost of a massive increase in weight. Modern design uses less carbon, more core, and has higher strength and stiffness.
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Old 09-12-2015, 21:50   #57
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Re: Is current carbon tech safe?

Sort of correct Greg, but...
It is the layers of CSM in a conventional lay-up that add thickness and as such, strength albeit at the expense of weight. Cores, which are the same as CSM in terms of width to the form but a lot lighter and cheaper - foam, balsa or ply or whatever add thickness and let the skins work together to give stiffness.
Impact strength is different to flexion and so forth.
Nowadays we practice Requirements Management. As we say to our clients, tell us your true requirements and let us discuss the options to achieve the performance outcomes. Other than that, you would be limiting the design unduly.
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Old 09-12-2015, 23:07   #58
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Re: Is current carbon tech safe?

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Hi Jim, I am over in Salt Pan Cove, will wave hello!
Why wave? Come by for a visit and a cuppa. We're anchored on the south side and will be around for a while yet.

Jim
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Old 10-12-2015, 00:17   #59
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Re: Is current carbon tech safe?

Sounds like I shouldn't worry so much. I appreciate everyone's contributions to answering my question. Thank you. What I now understand is that not all carbon materials are equal and that there are a lot of variations in the end compound that is loosely called carbon fiber. Makes anecdotal cases difficult to assess without knowing the actual structure of the material in question. Perhaps on the other hand I am being a little too paranoid. But thanks all.
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Old 10-12-2015, 13:35   #60
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Re: Is current carbon tech safe?

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Sort of correct Greg, but...
It is the layers of CSM in a conventional lay-up that add thickness and as such, strength albeit at the expense of weight.
CSM is not used to bulk up thickness (well, it shouldn't be, at least). The purpose of CSM in a layup is to help with print-through on the gelcoat side and to help with bonding between layers of the real structural glass (cloth, stitched fabric, roving, etc). In the first use, it should be only as thick as necessary. In the second use, it should be thin - for example, 18oz biaxial fabric will use a 0.75oz CSM between layers.

If it is being used to make a layup significantly thicker, then it is being used incorrectly and corners are being cut - or it is just a cheap, non-structural part.

Mark
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