From afar, Project Cedrus might not look that different from other foils on the market. But it is, thanks to unique architecture that allows for a range of manufacturing processes. Material and process are integral. The manufacturing processes you use for carbon fiber are very different from those used for metals or even other plastics. Furthermore, the process to make one foil will be very different from a process that you’d need to build 100,000 foils. The architecture of Project Cedrus incorporates the highly directional properties of carbon fiber, optimized for manufacturing processes now used in automotive and high-rate aerospace. While some companies may boast about using autoclaves to cure prepreg carbon fiber, this is really 40 year old technology. Modern epoxy resins can cure in seconds, have much lower viscosities, and allow for low pressure, single-sided tooling operations like stamping or oven curing. You can reap the benefits of this multiple ways, either by reducing cost, increasing rate, or testing prototypes that are more representative of your intended product. Project Cedrus benefits from all of them, thanks the the architecture below.
This was not the first iteration, and it won’t be the last. But it’s a big step in a new direction for the design and manufacturing of composite foils. The architecture is based around two open “hat” sections, bonded together at their flanges, which are then capped with non-structural leading and trailing edges. The benefits of non-structural edges are significant. A high value material like carbon or aluminum is displaced with a cheap plastic, which reduces weight and cost. The plastic edges can be 3D printed as in the case of my prototypes, or molded at high rates from soft thermoplastic polymers to improve safety and toughness. Non structural edges are very common on aircraft, just look out the window on takeoff or landing of your next flight to see the gap between the leading edge slats or trailing edge flaps. There’s not a lot of load in those components, their purpose is strictly aerodynamic. Soft edges are also less likely to lacerate your body, which is especially important in shark infested waters. Thermoplastic materials are also known for their toughness, meaning less time repairing small chips to your brittle epoxy mast and more time riding. While the first iteration edges are extruded from a fairly rigid grade of PVC, future versions could potentially be molded from a soft silicone material. The detrimental effects on performance, such as flutter, need to be evaluated before I can offer flexible edges as an option, but it’s something I will continue to work on as the first iteration is validated.
The open hat sections offer benefits of their own. It’s actually much cheaper to obtain a hollow structure using two open halves than to fabricate a single hollow monocoque structure using bladders or soft mandrels. It also makes it easier to integrate fittings, to permit the use of adapters that allow the mast to attach to various boards. Furthermore, the bonded flanges provide a nice indexing feature for the plastic edges, controlling position and improving joint strength. With open tooling, the layup and gauge can be easily altered to further optimize strength and stiffness as needed. Using this architecture and tooling, I was able to fabricate 4 different prototype masts, each with different strengths and stiffnesses. This would not be possible with a solid laminate structure, or with closed mold tooling.
The prototype masts don’t just have different decals. The “East Bay” mast has half the stiffness and strength of the “Coast,” which is still adequate for my wife. “Sherman” sits in the middle, with a nice compromise of weight and stiffness. The difference in weight is quite significant, although they all look the same. The architecture allows for easily modified length, layup, weight, and stiffness. Ultimately I see shorter surf foils, soft and lightweight strapless-optimized foils, and thicker laminates for those who like to boost, all using the same tooling and process. Not having to design and fabricate different molds for SUP, surf, or kite foils means that that I can reduce the costs of all of them. While we may think the foil market is big, it’s still way to small to absorb the costs of expensive steel molds and presses for slightly different products.