After picking up Onewheels, we decided to build a custom carbon fiber fender. This was our first time working with carbon fiber and resin infusion, imperfections included.
Materials used
Carbon fiber fabric, chopped fiberglass mat, Total Boat 5:1 epoxy, modeling clay, water-based PVA film, nylon vacuum bagging film, silicone flow media, and a vacuum pump kit, among other supplies.
Creating the mold
- Prepare the original fender: clean with all-purpose cleaner and denatured alcohol
- Apply PVA release agent: several thin coats, 30 minutes drying time between
- Build mold walls: foam core board with seaming tape, hot-glued around the fender edges
- Seal gaps: modeling clay pressed into crevices for smooth transitions
- Apply PVA again: several thin coats over the mold structure
- Create the mold surface: a 2:1 epoxy layer with blue pigment (dye would have given better coverage than pigment)
- Add fiberglass reinforcement: three layers of hand-torn fiberglass mat soaked in epoxy
- Cure and finish: overnight cure, trim excess with scissors and a rotary tool, light sanding
Key learning: a two-part mold split lengthwise would have made demolding much easier.
Creating the carbon fiber fender
- Prepare the mold: clean with denatured alcohol, mask the edges
- Apply PVA release layers: several thin coats with proper drying time
- Brush on an epoxy base layer into the mold
- Add carbon fiber layers: three layers, adhesive spray between each
- Install breather materials: peel ply and flow media above the carbon fiber
- Set up vacuum bagging: T-fittings in spiral wrap along the mold edges, covered with vacuum bagging film sealed with tacky tape and large pleats to conform to curves, then holes cut for the fittings and resealed
- Connect the resin infusion system: one vacuum line to the pump, the other dipped into an epoxy bucket, with a catch bottle inline
- Cure overnight before demolding
Pro tip: have every vacuum fitting on hand before starting, since delays let epoxy pool and cure unevenly.
Demolding and finishing
After curing, we carefully removed the vacuum bag and used plastic pry bars to extract the fender from the mold, then sanded the edges and shaped it for a proper Onewheel fit.
Lessons learned
Plenty of imperfections in this first attempt, mostly from inexperience with the technique. For next time:
- Use slower-cure epoxy (5:1 ratio) for more working time with vacuum bagging
- Use dye instead of pigment for more uniform coloring
- Consider gel coat as an alternative to epoxy
- Skip the initial epoxy layer and let resin infusion handle saturation
- Pre-check every vacuum fitting and piece of hardware before starting
The finished fender proved custom carbon fiber parts are doable at home, with plenty of room to refine the process on the next build.