Mending A Carbon Frame

My spare bike has developed a hole in the downtube, the result of grit and abrasion over a prolonged period of time, during the race at Keilder last season. With the new season nearly upon us I would be needing the bike again shortly and so it was time to mend it.
I purchased a carbon repair kit and set to work.
The first stage was to have a practice run. For this I used a section of an old carbon steerer tube, in which I made a similar hole using an electric sander. This took longer than I thought, it must have taken something out of the ordinary to make the hole on the frame. The main thing I learnt from the experiment was that less is better as far as resins are concerned and that the right mix for this resin is crucial.

The hole I was dealing with was not very large but it had gone right through

As you can see the hole has nice smooth edges, and there is no impact damage. The damage is not structural and there is little or no danger of it spreading.

After abrading the immediate area I layered up the carbon and resin to fill the hole with a small overlap over the surrounding area. This was then wrapped in shrink tape and heated to compress the area.

Not pretty, but after 48 hours drying the repair is structurally complete.

The next step is to sand the repair, trying my best to blend it into the rest of the frame. Starting fairly rough, I worked up through through four grades of paper.

This was then rubbed down with a polishing compound.

Obviously the frame has a smooth cosmetic layer whereas the weave is still clearly visible on my repair.



And the finished article. Note also the rather lovely Mt Zoom titanium bottle cages, 25g each, ideal for those of us too ham-fisted to be trusted with carbon ones...