A Cervelo P4 came in recently with what can only be described as a poor attempt at repair. The top tube had cracked in an accident, someone had a go at repairing the damage by basically wrapping carbon fabric soaked with resin around the area, with no apparant compaction or pressure applied. This certainly doesn't meet the structural requirements and cosmetically looks quite ordinary as well. This is a $15000 bike!
I have seen quite a few "home made" repairs over the years, here is another one. This one is a Zipp 404 rim that was "repaired" at the braking surface with 5 min Epoxy! This stuff goes soft at about 70 deg C, so as soon as the brakes are used this epoxy goes soft and basically falls off. There are some basics that need to be adhered to, NO home fibreglass repair kits, NO 5 min epoxy, seek professional advice.