Finishing Up! - my Stumpjumper Carbon Frame Repair

(3rd in a series of 3)


Here is a quick look at the final steps in my carbon fiber frame repair job.

In the previous post, I explained how I epoxied 4 layers of carbon fiber cloth over the damaged area. After the final layer was fully cured, I started sanding things down again. Once the area was sufficiently smooth, I brushed on a final coat of epoxy and let that cure for 10 hours in my hot box (see previous post).

Once that final top coat of epoxy was cured, I started the sanding again: I used a little 80 grit, then 120 grit, then 220 grit, then 220 grit wet (pictured below), before finally buffing things out with some steel wool. It's pretty smooth and shiny at this point and my fingers are pretty sore.

Final wet sanding before the enamel clear coat

Next, several rattle-can coats of clear enamel. This stuff provides UV protection to the epoxy, which can yellow over time if exposed to UV. At this stage, I'm spraying beyond the repaired area onto the factory paint/finish, in order to help blend the areas together.

UV protection

After about 4 coats of enamel, it's time to polish so that the repaired area will have a shine similar to the factory finish. I rubbed this cheap stuff around for about 30 minutes before I thought things looked decent.

Polishing the finish; trying to blend it to the sheen of the original finish.

Comparo: the repaired stay is slightly 'fatter' (not much) and it's definitely stiffer feeling when gently applying pressure to the stays by hand.

Time to get it together!!!

My 3-year old got pretty worn out watching me build it back up. This was the most zen-like bike-building session I've ever experienced....since becoming a father.

Not your 'factory finish'.

I started by riding it around the yard, carefully watching and listening for issues. Then I eventually worked my way up to riding it down the concrete staircase in front of our house....expecting a spectacular crack & crash at any moment. So far so good....

The steed rides again!

I plan on carefully subjecting the rear triangle to more and more abuse at low speeds, until I'm confident enough to gradually work it up to race pace again!

Edit/update: I have now exposed the bike to several laps of normal aggressive riding on my local mtb trails and it's riding beautifully.