The battle of carbon and aluminium. Who's winning here?

Translation of an article from Yacht 7-8/2022.

The ropes beating against the jungle of aluminum masts often conjure up a fantastic symphony upon arrival at the marina, with the promise of wind and thus freedom of travel. You may have noticed that not every mast makes the same chiming sound. The composite or carbon ones just do not chime. Perhaps, that's a bit of a shame, from that perspective, but for many other reasons this technology has its proper justification.

Boats and their owners carrying such rigging are duly proud of this hi-tech equipment and the black colour, which is the natural colour of carbon-fiber, often draws attention to it. Ambitious 'aluminium' sailors sometimes try to mimic this phenomenon too, but only by the use of black paint on the masts and boom surfaces. I should also mention the fact that while black paint on the surfaces of anything on a boat looks confident and sexy, it is also quite impractical in terms of maintaining a reasonable surface temperature. After all, climbing a mast in a marina that has a surface temperature of well over eighty degrees at midday requires a bit of skill and appropriate clothing and shoes. Anyway, who cares, when you’re then leaving the marina, you’re suddenly king, the center of attention and you enjoy the respect. But the issue is not all that simple. If you opt for a carbon mast, the rest of the rigging needs to match. No stainless steel vents, but a lightweight carbon or performance fabric. All of this together brings with it a massive increase in performance, increased safety, but also higher costs.

Photos: all the weight is placed in the middle of the boat, making it easier to move the catamaran through the waves.

Performance and safety? Anything's possible!

So is it really worth investing into hi-tech lightweight technology? When designing the IC36, we wondered how to increase performance while keeping the feeling of good handling and actually have a positive impact on safety when sailing at speeds of above twenty knots. In fact, we occasionally get speeds of over twenty-five knots on the "clock" and at first glance such a task seems unmanageable. But at Independent catamaran we have succeeded in tackling that. We simply returned to the roots of the  design. Having the structural modernity with a tremendous amount of comfort and heavy amenities placed where it fits best in terms of space, and not having much regard for the dynamics of the vessel, can have fatal consequences on the smoothness of the ride and safety. Manufacturers often solve this issue by simply increasing the displacement, however, that leads to a sharp reduction of boat dynamics and speed. We did not want to accept this solution and so we’ve looked at the issue from the point of view of basic physics. And we came up with three rules that we have devoutly followed. We moved the center of gravity lower, made the powerful carbon "wing" mast shorter, and the lift force and the drag force of the sail was lowered to the waterline. We kept the overall dry weight of the boat low (an 11 x 6.2m catamaran weighs less than three tonnes) and everything heavy was placed close to the centre of gravity (the 48V batteries for the electric motors and the operating 12V batteries lie axially to the hulls under the mast, and the water tanks are in the main spar). So the bow and stern do not suffer from any unnecessary load and the boat does not suffer from a "pendulum effect", i.e. rocking. The other heavier objects are in the stern. These are the electric motors, which along with the saildrive weigh only 58 kilograms each. We have taken hydrodynamics and hydrostatics, the aspects that determine the behaviour of a boat in the water and specify its displacement, to the frontiers of current knowledge in the field. This was inspired by the world of ultimate racing, and we have created this comfortable racer/cruiser for families and sailors with sporting ambitions. The bows, for example, are designed to not fight the waves, but to go through them like a hot knife through butter and not hinder the boat's dynamic speed with unnecessary drag. You may recall at the 2020 Vendée Globe, where Alex Thompson, wearing a headlamp, repaired a cracked bow brace after repeatedly loading his foiling Imoca as the bow hit the waves causing the extreme dynamic deceleration of his boat, the Hugo Boss. We wanted to avoid that by using sharp bow bumps on the IC36. There is a lot that can be said and written about boats as you look at the design. Over time I have found that every little thing in the design makes a difference and affects its performance. And building a boat according to precise specifications can have fatal effects on the outcome. It's perfectionism that you must master and never waver from your goals. One of the other topics is rigging. We will explain the issue of rigging in more details below, while focusing on carbon technology. This is because I think that even after all these years, rather little is known about carbon-fiber and there is really nothing left to write about aluminium and stainless steel, as these materials have shown their capabilities over time. We will look at other aspects of the equipment in future articles.

Carbon versus aluminium

In terms of technical properties, the carbon mast has an advantage over the aluminium mast in several respects. It is at least 35 to 45 percent lighter and has a lower centre of gravity, which is a very important feature in terms of dynamics, knock effect and safety. It tends to be considerably stiffer, but at the same time retains some flexibility for handling overloading. It just won't chip, but if it does and there is damage, it's easier to repair than aluminum.

Photo: Light weight is the key to everything, after all.

Lighter, stiffer, more dynamic

So the aluminium mast is heavier, but that's not the only thing going on here. The thickness of the aluminium mast profile is uniform along its entire length. At the time of sizing the mast, the yard selects from predefined profiles available in the market, taking into account the "righting moment", or the sailboat's heeling effect, with a precise determination of the load on the burdened parts of the boat and the mast itself. The carbon mast is subject to many calculations, one of which is the identification of structural areas to be fitted with additional layers of fabric with the appropriate fibre direction exactly where such reinforcement is needed. On the other hand, the profile wall is made thinner where possible, so that the overall weight balance achieves greater savings and the centre of gravity shifts significantly lower towards the waterline. The stiffness and flexibility gives greater dynamism, and this is also reflected, for example, in the fact that when the wind gushes or the boat moves through the waves, the mast deforms in various places and then straightens back up to its original shape. And this gives the ability to keep the sail, as long as possible, in the set shape (trim) and to correct itself dynamically as quickly as possible even if the deformation is as little as possible. This generates the extra force that drives the boat forward faster. And it's not just about performance, it's also about safety. A boat that is unnecessarily affected by the inefficient design of the hardware setup area and a high center of gravity causes excess drag that negatively affects its speed and stability. Conversely, if we can avoid this with the use of appropriate equipment, we can increase the performance, and get the center of gravity as low as possible, this would mean the boat and its crew will feel comfortable even at double-digit speeds. Now let’s look at the centre of gravity itself. A specific feature of light masts is their low centre of gravity, which significantly modifies the stability of the yacht. The boat thus absorbs less load. And look out! In keel sailboats, the weight of the keel can also be reduced or the draft of the boat can be slightly reduced. A further weight reduction can then be achieved by using a carbon boom, where weight savings of up to 35 percent are again achieved compared to a duralumin boom. And if we add carbon or fabric rigging (the IC36 uses Dyneema DMX 20 for the backstay and a forestay with an anti-twist insert for reeling in the cutlass and a durable black wrap), we can achieve an incredible weight reduction of 70 to 75 percent compared to using stainless steel Nitronic rods or braided wire. The IC36, by the way, also uses textile ropes to reinforce any structural turnbuckles on the beam or bowsprit. For bowsprit, it gives us a significant weight reduction and a breaking load of 30 tons (breaking force), which is about nine times more than what is needed. But there's a reason for it here, and that is reliability under extreme loads.

Photos: carbon kiking from Pauger (left), carbon prepreg, machine pre-saturated fabric (right)

Photos: Examples of stainless steel fittings to carbon rigging

Other weight reduction options

There's carbon-fiber and carbon-fiber. Standard masts and spars are now made of commonly available carbon fiber. But it is possible to add additional trim from high modulus carbon prepreg and save an additional 10 to 15 percent weight. These are the best types of carbon-fiber cloth, pre-impregnated with resin, which must be cooled to minus 18 degrees Celsius before they are put into molds and subsequently undergo pressure forming in an autoclave and then cured. Another advantage is the option of using a smaller profile, which reduces not only the weight but also the aforementioned air resistance during the air wrapping and air rushes into the sails. Here we go again. This increases both stability and safety. Such a mast can be designed for any boat. With Pauger, we have started the development of our rigging in Hungary. And I have to say on behalf of Independent Catamaran that it was one of the best collaborations in the development of our model. The IC36, thus, "wears" a high modulus rotating mast of the highest quality and strength, which has already withstood winds of around 45 knots and the huge waves of the Bay of Lions and delivered to us, the much sought after, performance, strength and safety. Pauger also spent a lot of time with us during the development process, patiently looking for solutions to accommodate everything we needed to fit onto the IC36. To reduce tension in the gears, boom and the mast itself, we can fit stoppers, winches, sail halyard locks etc. to the mast. With Pauger, it's like the pit area of a racing stable, projections, measurements, stress tests. And suddenly the mast is up and towering on the IC36 as an expression of respected quality and performance. And it doesn't have to be "in black" at all, people stop and discuss various things at our boat, not excluding the white wing mast. Anyone (not just racers or big shipyards) considering replacing their existing rigging will find their solution at Pauger, and I find that unique yet affordable. That's because they will custom build your mast from a single piece using a one-off mold made on a five-axis CNC machine. This process is particularly suitable for multihulls with swing masts, such as on the Independent catamaran IC36. And when the design proves successful, the aluminium mold will be produced for a larger series production if the customer requires it.

Photos: lower part of the mast with stoppers and winches and a sleeve for turning

How is such a mast made?

Either a female or male mold is used. Pauger used an aluminium female mold split into two halves. The prepreg high modulus cloth format, inserts and reinforcing patches are formatted on a plotter and partly done by hand as per the desired design and exact schematics and then aligned with the help of a laser projector. In this way, the best symmetrical accuracy of the layers is achieved. Once the layers are placed, the molds are folded together. The entire system is placed in its length in an autoclave, i.e. in a pressurized chamber, and the layers are then compressed from the inside using inflatable bags with a pressure of five bar. Finally, the entire mold is placed in a giant oven and cured at 100-120 degrees Celsius. After removal from the mold, the mast is coated with a UV resistant durable acrylic paint.

Carbon "standing rigging"

One, generally, does not get bored with Pauger. When we develop a high-performance catamaran, we place superior demands on the result, the materials used and the manufacturing technology. With Pauger it is similar. They have been making carbon masts for over thirty years and have recently launched the C-ROD, high modulus carbon vents, masts and tensioners for furling or structural clamping. Believe it or not, C-ROD is a solid carbon-fiber rope with epoxy binding with various endings for different types of attachment. The carbon fibers are impregnated under a specific tensile stress and are instantly compressed and heat shrunk. The whole process is carried out in a continuous oven to ensure an infinite length of ropes. Now for the properties. Compared to stainless steel wire, C-ROD has twice the strength and stability per diameter. (Nitronic has a tensile strength of 1,550 MPa or 158 kp/mm2 and the Pauger Carbon rod has a strength of 3,000 MPa.) It can withstand 100,000 cycles of shock stress toward the limit. Stainless steel wire will only last 80,000 cycles under the same conditions and degrades over time. It is not true that it is brittle, the whole process is secured by effectively placing the wire rope in the terminal to prevent fraying and fiber distortion. The wrapless technique ensures that visual strength checking is absolutely simple. Should damage occur, it is simply visible at a glance. Which cannot be said for textile ropes with a protective sleeve. Pauger claims that the entire system is completely maintenance-free and boasts a higher breaking load strength, i.e. a failure force of 170 to 190 percent. Again, weight savings and lower air resistance, along with a significant extension of service lifespan compared to the stainless steel profile. This technology can replace your current one at the snap of a finger. In fact, they have compatible stainless steel or titanium end caps available. This system is also suitable for heavily loaded race boats and we look forward to putting it on the next IC36 or the upcoming IC48.

Photo: Mast, boom and sails as seen from the cockpit

The price of carbon-fiber rigging is higher, but still more economical than one might think

The initial investment is higher. But it's not an astronomical amount which a yachtsman couldn’t afford. That's more the myth than the fact. With a considerable extension of lifespan, almost no service requirements and the simplicity of visual inspection of the condition of the rigging, carbon-fiber simply has the edge. Once again, YES, carbon mast and C-ROD are easily 1.5 times more expensive in total than aluminum. But when we reduce the weight of material required to support the heavy rigging of stainless steel and aluminum, thus adding some carbon "lightness" in operation, and apply the long term sustainable surface treatment to reduce the overall wear and tear on the boat, I have to conclude that in the long run this comprehensive solution will pay off. The boat will pay you back by giving you an incredible feeling of sailing, it doesn't flap and moan in stronger winds, it rides comfortably. It doesn't "fight" so much with other physical phenomena such as hydrodynamic drag or the heeling effect and the resulting rocking. I'm aware that I'm a bit caught up in the pursuit of technology, but I'm convinced that what I'm writing here makes sense. Just think about it the right way and the result you get on almost any boat will put a big smile on your face. That's how we do it at the Independent. Every time we get something like this right and go that little bit further, the satisfaction we get for the hard work and investment we put in is huge. As a result, it will eventually give you numbers like IC36, speeds of over 25 knots without much risk. Once the wife of a German client was walking around the cockpit of the IC36 frantically and taking pictures of the display. When I asked her if she'd rather not sit down because we were going at speeds over 20 knots, she replied that she hadn’t even noticed that. At that moment we realized that what we had been waiting for, over five years, had happened. We knew we had built this boat right. That Jonah (IC's co-owner), in collaboration with me and the Vrtiška & Žák studio, who had devoted an incredible amount of energy to the project, had designed it correctly. There's not much we'll do differently on the next piece, maybe something cosmetic. In the end,it was our own perfectionism and desire to build an exceptional and progressive boat that has led us here to where we are. And then to say everything has already been invented.

Picture: The difference in wrapping around a fixed or rotating mast can be seen from this graphic.

Photo: The bowsprit is rated for a breaking moment of thirty tons, which is about nine times more than is needed.

From the bay on Palmižana Island Jaromír Popek

Photos: Libor Zhoř, Independent catamaran, Pauger, Daniel Guryča

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