Upgrading a race car often involves addressing unforeseen issues, such as tire clearance problems. When larger tires and wheels on a friend’s Ralt R5 CSR Mazda race car caused rubbing against the existing bodywork, a less-than-ideal modification was initially implemented. This involved cutting into the fenders and bolting on spaced plates, which proved both unaesthetic and still prone to tire rub. To rectify this, the goal was to craft new fender sections that could be seamlessly integrated with the existing bodywork, avoiding the expense of a complete bodywork replacement. This project showcases a method to create custom Carbon Fiber Car Parts, specifically fender flares, using fiberglass molds and carbon fiber layup techniques. While the original modifications were made some years ago, and full photographic documentation wasn’t available, detailed illustrations help to clarify each step of this process.
The first step involved determining the desired fender line elevation. A template was created to guide the cutting of blue foam, a material chosen for its ease of shaping. The blue foam was then cut using a hot wire cutter to achieve the desired form. This foam shape was placed atop the existing fender to ensure a proper fit and visualize the new fender flare profile.
Once satisfied with the foam’s shape, it was securely taped to the fender using clear packing tape. This tape layer serves as a crucial barrier, preventing the polyester resin used in subsequent steps from dissolving the foam. To incorporate ventilation into the new fender design, wood molding strips were hot glued onto the taped foam, creating the framework for vents.
With the foam shape finalized and vents in place, a mold release wax was applied to the taped foam surface. This wax coating is essential for easy separation of the fiberglass mold from the foam pattern later in the process.
Next, fiberglass cloth was prepared by wetting it thoroughly with polyester resin. This resin-soaked cloth was then carefully applied over the waxed foam mold. For this stage, either woven fiberglass cloth or chopped strand mat (CSM) can be used. It’s important to note that if CSM is used, polyester resin is mandatory, as epoxy resin will not properly interact with the styrene binder in CSM, leading to unsatisfactory results. Polyester resin, however, effectively dissolves this binder, allowing the CSM to conform and harden correctly.
A useful technique for working with woven fiberglass cloth involves pre-cutting the cloth to match the pattern. Applying 3M Super77 spray adhesive to the pattern helps to temporarily secure the cloth in place, simplifying the resin wetting process. A short-bristled paintbrush is ideal for carefully wetting the woven cloth with resin, ensuring thorough saturation. When applying fiberglass in sections, it’s crucial to overlap each section by at least an inch to maintain structural integrity.
After the polyester resin cured and hardened, the fiberglass mold could be carefully removed from the underlying foam pattern. This fiberglass mold now serves as the negative form for creating the positive carbon fiber car part.
To prepare the fiberglass mold for carbon fiber molding, a mold release wax was applied to its inner surface. This step is crucial for ensuring clean separation of the finished carbon fiber part from the fiberglass mold.
The process of creating the carbon fiber car part begins by wetting out carbon cloth with resin, this time opting for epoxy resin, known for producing a significantly stiffer and stronger final product compared to polyester resin when used with carbon fiber. The resin-saturated carbon cloth is then carefully laid inside the prepared fiberglass mold. A short-bristled paintbrush, used with a “stippling” motion, is effective for ensuring the epoxy resin fully penetrates the carbon cloth as it’s positioned within the mold, eliminating air pockets and ensuring complete saturation.
To maximize the strength and rigidity of the carbon fiber car part, layers of carbon cloth are typically applied at alternating 45/90-degree orientations. This technique is vital because woven carbon cloth exhibits stiffness primarily along the direction of its fiber weave. By alternating the fiber direction in each layer, the resulting composite material gains strength in multiple directions, enhancing overall structural integrity.
While the epoxy resin is still in a partially cured, or “green,” state, excess carbon fiber material around the edges of the mold can be trimmed with scissors. This is considerably easier at this stage than after the resin has fully hardened, preventing jagged or uneven edges on the final carbon fiber car part.
Once the epoxy resin has completely cured, the finished carbon fiber car part can be removed from the fiberglass mold. The result is a precisely shaped, lightweight, and strong component ready for installation.
The final steps involved bonding the newly molded carbon fiber car part sections onto the existing race car bodywork. Body filler was then used to seamlessly blend the new carbon fiber fender flares into the original body lines, creating a smooth, integrated, and professional finish. This process not only resolved the tire clearance issues but also enhanced the vehicle’s aesthetics and potentially improved aerodynamic performance with the custom-designed fender flares, all achieved through the creation of bespoke carbon fiber car parts.
