I was lucky enough to be gifted a frame from a friend. He leaned his bike against a sign and it fell on the curb shattering the top tube through.
I like to work with my hands and I like to learn new things so I looked into carbon repair.
I practiced first by buying some unidirectional fiber carbon tunes and sawing them in half. I practiced cutting cloth and patching them inside. I used a inner tube wrapped in silicone to clamp the cloth as it cured. I would use heat shrink tape wrapped around silicone paper on the outside and sand between layers to maintain the profile.
Fishing the carbon inside the frame was the most tedious part of the process. I applied two layers and brushed them in epoxy and slid them with my fingers until they were covered. I used an endoscopic camera to ensure they were in the right place. I used an inner tube clamp that.
After that I sanded down the finish and applied four wraps of fiber on the outside and sanded down between cloth applications.
Then I touched up the finish. If I wanted perfection I would have stripped the finish and repainted the whole thing but this being my first carbon repair, a whole respray would have been a lot of work if the frame failed to hold.
Reapplication of the matte black on the top portion of the top tube was simple enough. For the rest of it I sanded the frame up to 3000 grit and applied rustoleum gloss red enamel and polished it. It is extremely close to the red Trek used and while the touch up is not flawless, it is good enough for me especially because this bike was destined for a landfill.
I did an easy 20 miles and it holds. It is extremely stiff. I did a couple hard sprints and a steep climb and it holds like a champ. I plan to ride it more under controlled circumstances but I feel confident on the frame. And fortunately the area where it was fractured is not a high stress area.
by EmergencyMud4549