Is current carbon tech safe?

[GoingWalkabout]

Originally Posted by zeehag

talk with bob perry about carbon fibre boat hulls.. he makin a gorgeus cruiser now.

Thanks Zeehag. I'll certainly check him out. His boat that is

[Stumble]

Originally Posted by GoingWalkabout

Good point colemj. Nonetheless it would be reassuring to understand the makeup of the carbon being used. As another poster said it is what is being used by Boing so this is giving me a high level of comfort. But does an aircraft wing receive the same level of direct force that a mast can encounter. Too bad there isn't a wind type tunnel to experiment and test different masts and setup configurations. Examine, understand and test is the scientific way. and then share your scientific observations with the broader world so as to contribute to further discovery.

1) a wing is just an unsupported column. It is exactly the same as a freedom unstated mast.

2) wind tunnel testing has been done on masts. On,y at the high end, but it's out there, and available if you want to have it done.

3) exact engineering specs on masts are available. Though unless you know what the numbers mean why bother. The material list is available generally to buyers, or qualified shoppers.

4) a lot of masts and other stuff has been built, tested, and broken. Development programs abound with this type of information. It isn't always generally available to the public, but then neither is Boeings internal engineering numbers.

Btw I keep using Boeing because when I was working for a titanium supply company we did a lot of work with them. And the same guy I talked with about titanium/carbon at Boeing was the guy I spoke with at a mast fabrication company.

[GoingWalkabout]

Originally Posted by Stumble

1) a wing is just an unsupported column. It is exactly the same as a freedom unstated mast.

2) wind tunnel testing has been done on masts. On,y at the high end, but it's out there, and available if you want to have it done.

3) exact engineering specs on masts are available. Though unless you know what the numbers mean why bother. The material list is available generally to buyers, or qualified shoppers.

4) a lot of masts and other stuff has been built, tested, and broken. Development programs abound with this type of information. It isn't always generally available to the public, but then neither is Boeings internal engineering numbers.

Btw I keep using Boeing because when I was working for a titanium supply company we did a lot of work with them. And the same guy I talked with about titanium/carbon at Boeing was the guy I spoke with at a mast fabrication company.

Thanks Greg. What I'm talking about is not the engineering information passed around within the industry between vendors and users. I'm talking about the details of the differing materials structures passed around by scientists and researches. A very different kind of analysis. Manufacturers give a birds eye view of their product. What I am interested in the pure scientific research. And I do understand that for some if not most, this kind of information is proprietary. But in the fields I deal in I deal with both basic information industry information while also pure academic and applied research data.

[Stumble]

Just to get started take a look at the Oak Ridge National Labratory and UTSI online research library. Both have huge repositories of CF research available, though some is behind paywalls.

Is there anything specific you are looking for.

[mstrebe]

Originally Posted by GoingWalkabout

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.

Firstly, carbon fiber has been in active development for decades and is probably the most engineered material in production use today. If you're uneasy about it because it's the defining ingredient in pencils, soda water, pollution, and humans, and some of those things aren't as stiff as a mast, you'll just have to keep learning about carbon until you decide you're figured it out. If the fact that most all modern race boats, race cars, and the 787 are made out of it isn't going to convince you, nobody on this forum will either.

Carbon is a particularly useful element because it is the lightest solid (non-gas) element which bonds exceptionally strongly to other elements. Because of its atomic structure, it likes to adhere to other atoms--lots of other atoms, including other carbon atoms.

Because of this quality, it comes in all kinds of molecular structures. Pure carbon can take the form of diamonds, the hardest of all common materials, or graphite which is essentially carbon dust. Coal is mostly carbon, as is charcoal. Living things are made primarily of carbon and water-- in fact, wood IS natural carbon fiber with lignin as its resin. The word resin that we use for epoxies actually comes from tree resin, which is essentially natural plastic.

Carbon fiber is made from a plastic precursor such as rayon or PAN which is "carbonized". Carbonization is the process of heating an object containing carbon to about 2,000 degrees in an oxygen-free environment, which drives off all the other molecules. Carbonized wood is charcoal. You can carbonize humans and put what's left in an urn. Anything that contains carbon can be carbonized.

What's cool about carbonizing threads made of plastics that are already 80% carbon is that what's left are pure carbon threads that are strongly bonded together: more strongly than any other kind of thread. Like trying to pull diamonds apart strong. They take these threads and weave them into yarns which are then woven into carbon cloths.

The problem with these threads is that they're only strong in the pull direction. Come at them from a 90 angle and they'll cleave easily--just like cutting a diamond.

That's where the epoxy comes in. When you wet out carbon fiber with epoxy, it glues the carbon threads into place so that they cannot move in relation to the rest of the fabric. Since it cannot move and does not stretch, it creates a super-strong material. If something won't stretch at all, you can't dent it. This makes carbon incredibly strong in deflection which is almost always what we want from a construction material. Carbon fiber won't stretch so it's very hard to puncture, but it can be punctured by something that can overcome all of the cleave strength of all the carbon it's impacting at once. Otherwise it'll bounce off.

The big with carbon fiber is that it's only strong in the direction of the threads. This is why you almost always see the "carbon look" weave of three sets of threads woven in 60 degree increments, because that creates strength in all directions for a panel. There are different weaves for different purposes, and it is critically important to choose the right weave for your application.

Another problem with carbon fiber comes from the fact that it's a composite material (carbon fiber and epoxy) and composites are extremely difficult to inspect for fatigue failures which can occur when a material is routinely flexed. The flexing can create de lamination of the epoxy that is impossible to detect, but which reduces the composites strength. The solution is to overbuild flexural components (like masts) so that they're strong enough to not bend much if at all, and then it's not a problem.

It's greatest asset however is its lightness. It's amazingly light for the same strength in deflection as metals, which is why it's showing up everywhere where it's cost makes sense.


Sent from my iPad using Cruisers Sailing Forum

[GoingWalkabout]

Thanks mstrebe and Stumble for your thoughtful contributions. I do understand a little about carbon materials having worked in Graphene nanotubes R&D for a very specific bio engineering application. It is the composite use of carbon with other materials that I was raising as a point of further research and understanding while at the same time having concerns with the structural issues of current carbon compounds as it relates in particular to brittleness. It is known that carbon rods as a structure are indeed brittle but this is mitigated by the composite material and as has been said the thatching into different directions the carbon composite material.

I have gone back and looked at carbon nanotubes structures and as I thought the case may well be they are indeed better then the carbon rod structure currently used in carbon composites.

The following I found very interesting. By the way just as an aside it is interesting to look at the material failures of other users of composite carbon in say the skate board and racing bike fields. Today's composite carbon does have its points of failure both in the theoretical and applied real life.

"
When people need a material that’s strong yet lightweight, they usually look to carbon fiber. In the near future, however, they may instead choose to go with composite materials made from stretched carbon nanotubes. These materials could theoretically offer the same strength as carbon fiber at one-tenth the weight, or the same weight at ten times the strength. Researchers from North Carolina State University have recently succeeded in creating such a composite.
According to the university, scientists have spent decades trying to achieve the four goals that must be met in order to create CNT (carbon nanotube) composites – the nanotubes must be long in order to effectively carry loads; they must be aligned in rows; there must be a high ratio of CNTs to the polymer or resin used to hold them together; and, in order for the material to bear weight evenly, the nanotubes must be as straight as possible.
NC State’s Dr. Yuntian Zhu, a professor of materials science and engineering, is reportedly the first person to come up with a method of meeting all of these requirements.
The process begins by growing an array of long, skinny carbon nanotubes out of a flat substrate. Because the nanotubes aren’t rigid, they tend to flop over and lean against one another. The CNTs at one end of the array are then pulled sideways, causing all the other nanotubes to topple over in the same direction. As a result, they end up all being aligned.
The aligned array is then wound onto a rotating spool, simultaneously being stretched and being sprayed with a polymer solution that keeps the nanotubes bound together. This respectively results in a straightening of the nanotubes, and a high CNT-to-polymer ratio.
The finished product is a ribbon-like material, several bonded layers of which could supposedly be used to build anything from bicycle frames to aircraft. Because of the CNT-stretching process, that material has 90 percent more tensile strength and is 100 percent stiffer than it would be otherwise. Additionally, its thermal conductivity is almost tripled, while its electrical conductivity is boosted by 50 percent.
A paper on the research conducted by Zhu's team was recently published in the journal Materials Research Letters.
Source: North Carolina State University"

[Cadence]

Sounds academic since affording a carbon fiber boat is for the well to do racing set.

[Djarraluda]

As stated, the makers have their materials and probably keep them secret.
Not being a materials scientist, but an engineer who respects such wizards, I am very aware of the old adage re Horses for Courses.
Carbon fibres are used within an engineered structure. As such, it needs to be designed! Tell your engineer how tight you want to tie that knot in the spar and how often you want to untie it - they will design a spar accordingly.
We can create flex, or not as necessary. We can create durability, or light weight.
Most carbon fibre boat structures are used for racing machines due to cost, but the consequential request for light weight means that durability is sacrificed. An example is that an America's Cup spar has a life of one series - any more and it is too heavy.

Engineering is the answer, but what was the actual question asked of the designer.
OK, just to show we are humble folks I will admit that we are not the sole font of all wisdom in the world, we work in collaboration with others to create the form etc.

[Stumble]

Also keep in mind that the price of CF is falling quickly. It's role as just something for the race boats is pretty quickly ending as the price for CF masts and even hulls is starting fall. Bob Perry mentioned the price premium for a 40' CF hull versus glass is about $40,000 right now. Obviously not nothing, but not close to what it used to cost.

For masts particularly I would guess in the next 10 years new aluminium masts are going to be almost eliminated. The price savings just isn't worth the extra weight.

[TJ D]

Now here's a topic that is also of great interest to me, since my boat is entirely carbon fiber, including the rig! It's all laminate, with different core materials depending on location on the boat, nomex on deck, baltek sides, and duracore below the waterline.

First off, the brittleness does not seem to be an issue provided the panel is constructed strongly enough to avoid flexing in the first place. In the case of my boat, when she was being built, panels were made up and sent to the lab for testing. Failure occurred at 54PSI. A further test of 400,000 cycles at 20 PSI (which is nearly triple the failure specification for DNV/ABS slamming standards for high speed offshore military craft, by the way), no degradation was found. This strength has been achieved in a boat which at 55' only weighs 24,000 lbs. D/L is 72. That's really the beauty of the material. One can build a boat which is extremely strong, but will still perform very well. That's where I see the material being so useful in a cruising boat.

I think that where folks might run into trouble is if they push the design close to the limit of how light such a boat can be built, as with any other material. Certainly carbon done right is absolutely a viable material.

One thing that was found during impact testing was that the Kevlar crash layer worked better on the INSIDE of the laminate, essentially acting as a last line of defense in the case of a collision with a submerged object. Kevlar on the outside of the carbon was found to be too brittle.

Regarding rigs, I think that the technology is totally proven. Our mast is stepped quite high to avoid any boom loading on the rig. The boom is attached to the vessel itself. This was in recognition that some carbon (but any material, really) rigs were failing at the first spreader due to boom loads interfering with column loading on the stick, so the solution was to get the boom off the mast. We've got a big carbon 'pod' on the deck, which seems to be a source of endless speculation to passersby, but that takes care of any perpendicular loading problems with the carbon.

Anyway, we're quite satisfied with the material. The rigidity took some getting used to, for sure, but once you get over being able to feel every little shudder, it's certainly an excellent way to go. The boat has been used in ocean passagemaking since built, so certainly she has had some proper real-world trials.

Good sailing, TJ

[thinwater]

Originally Posted by GoingWalkabout

"Graphite is a form of carbon. The carbon fibers are not homogeneous and contain a percentage of amorphous carbon and another percentage of graphite, depending of the process used. If the process used a precursor PAN (polyacrylnitril), and if the temperature is higher than 2500°C, the graphite increased.
The graphite fibers present a higher Young's modulus, but a lower strain at rupture, they are more brittle."

Some clarifications for non-engineers:

• The Young's Modulous is the elasticity; a higher YM is just another way of saying it is stiffer.
• Strain is the amount of stretch or bend, not the force applied. Force is called stress.

It is logical that a material with a high YM will have low strain at rupture (it is stiff and will not bend much). Brittleness, and the related parameter toughness, are related to the energy required to break something (not the stress). Toughness is proportional to stress x strain. Thus tough materials are often those that will bend far without breaking; it doesn't mean they are stronger, only that they absorbed more energy in the process. For example, a nylon rope perhaps 20-30 times tougher than a Dyneema rope of the same strength rating, depending on construction.

----

Another challenge with carbon, related to the stiffness, is that it can be difficult to combine with other materials. Because it is so stiff, it tends to carry all of the load (imagine a chain and a bungee trying to share a load), creating complex local stresses.

This may be one of those areas where racer tech is not cruiser tech. While their are certainly good cruiser applications for carbon fiber, it should not always be considered better, it should be considered different. I wonder if they will engineer boats with the same toughness as FRP, or just the same strength? There is a huge difference when groundings are considered. Cycles at a specific PSI do not answer this question; collisions and groundings are cycles at a specific energy absorption, which will require many times higher strength, if the boat cannot bend.

[IdoraKeeper]

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.

[GoingWalkabout]

Originally Posted by TJ D

Now here's a topic that is also of great interest to me, since my boat is entirely carbon fiber, including the rig! It's all laminate, with different core materials depending on location on the boat, nomex on deck, baltek sides, and duracore below the waterline.

First off, the brittleness does not seem to be an issue provided the panel is constructed strongly enough to avoid flexing in the first place. In the case of my boat, when she was being built, panels were made up and sent to the lab for testing. Failure occurred at 54PSI. A further test of 400,000 cycles at 20 PSI (which is nearly triple the failure specification for DNV/ABS slamming standards for high speed offshore military craft, by the way), no degradation was found. This strength has been achieved in a boat which at 55' only weighs 24,000 lbs. D/L is 72. That's really the beauty of the material. One can build a boat which is extremely strong, but will still perform very well. That's where I see the material being so useful in a cruising boat.

I think that where folks might run into trouble is if they push the design close to the limit of how light such a boat can be built, as with any other material. Certainly carbon done right is absolutely a viable material.

One thing that was found during impact testing was that the Kevlar crash layer worked better on the INSIDE of the laminate, essentially acting as a last line of defense in the case of a collision with a submerged object. Kevlar on the outside of the carbon was found to be too brittle.

Regarding rigs, I think that the technology is totally proven. Our mast is stepped quite high to avoid any boom loading on the rig. The boom is attached to the vessel itself. This was in recognition that some carbon (but any material, really) rigs were failing at the first spreader due to boom loads interfering with column loading on the stick, so the solution was to get the boom off the mast. We've got a big carbon 'pod' on the deck, which seems to be a source of endless speculation to passersby, but that takes care of any perpendicular loading problems with the carbon.

Anyway, we're quite satisfied with the material. The rigidity took some getting used to, for sure, but once you get over being able to feel every little shudder, it's certainly an excellent way to go. The boat has been used in ocean passagemaking since built, so certainly she has had some proper real-world trials.

Good sailing, TJ

Thanks TJ. Your real life experience is very much appreciated. What you have explained gels with what I understand theoretically. . Sorry for the pun.

[TJ D]

Walkabout,

My pleasure. We were also a little skeptical about going to carbon fiber. My last boats were one steel and two glass, so this was a big change for us. I think that's one of the reasons that the designer/builder spent the money on the lab testing of the panels, just to make sure that everything was kosher with the finished product.

For our part, the difference in sailing enjoyment between a very lightweight boat and a heavy one has been life-changing. I was actually getting pretty sick of passagemaking before we purchased our latest ride. Now, it's like being a kid all over again.

However, we would not have done it if we found that safety was in some way compromised. So, it wound up being a good choice for us. I would not have opted for an 'edge of the envelope' racing boat by any means. Honestly, I don't know how many carbon boats are out there which are being built to handle the realities of cruising life, but it does seem that some of the higher end builders have finally embraced the material. I know that Swan is using it extensively now, and they certainly are not ones to stick their necks out on unproven methods.

Are you considering a new build?

TJ

[GoingWalkabout]

Originally Posted by thinwater

Some clarifications for non-engineers:

• The Young's Modulous is the elasticity; a higher YM is just another way of saying it is stiffer.
• Strain is the amount of stretch or bend, not the force applied. Force is called stress.

It is logical that a material with a high YM will have low strain at rupture (it is stiff and will not bend much). Brittleness, and the related parameter toughness, are related to the energy required to break something (not the stress). Toughness is proportional to stress x strain. Thus tough materials are often those that will bend far without breaking; it doesn't mean they are stronger, only that they absorbed more energy in the process. For example, a nylon rope perhaps 20-30 times tougher than a Dyneema rope of the same strength rating, depending on construction.

----

Another challenge with carbon, related to the stiffness, is that it can be difficult to combine with other materials. Because it is so stiff, it tends to carry all of the load (imagine a chain and a bungee trying to share a load), creating complex local stresses.

This may be one of those areas where racer tech is not cruiser tech. While their are certainly good cruiser applications for carbon fiber, it should not always be considered better, it should be considered different. I wonder if they will engineer boats with the same toughness as FRP, or just the same strength? There is a huge difference when groundings are considered. Cycles at a specific PSI do not answer this question; collisions and groundings are cycles at a specific energy absorption, which will require many times higher strength, if the boat cannot bend.

Thinwater, I agree. Especially about racing tech not necessarily fitting with cruising tech needs. Somehow using all that tech to lighten the boat that I then go and put a huge kitchen fridge in doesn't really compute.

But what I am thinking of is CF being used in combination for specific purposes such as is already the case with masts. I'm perhaps a little on the paranoid side of the spectrum so I often think of better protecting those sharp edged bows as they slice through the water on my future catamaran. First line if defense I have decided is the new forward looking sonar along with a well set radar but adding say a high tech carbon material sleeve at bow like a suite of armor is what I am fantasizing about. I think I am going to have to wait for the next generation carbon materials that will be using carbon nano tubes rather than the current carbon nano rods. I understand nano tubes will give a thousand times more impact strength along with even more weight reduction. And such material is being developed now. Isn't life wonderful.