Q: How about some comments on fillers? Qcell takes forever to cure enough so it can be sanded.
A: If you want to use qcell mix as a filler, get some heat lamps or even a heat gun and warm it up to speed the cure. Note: I said WARM it up, don’t burn it up. Raising the temp up to no more than 150-180 degrees will allow you to sand it within an hour.
Note also that there is always a thin film of uncured resin on the surface exposed to the air that makes it appear that it hasn’t fully cured yet. Heat will cure that gummy layer that ruins sandpaper on the first pass.
Use caution with heat lamps. They will overheat and ruin a part in short order if to close to the surface. Used carefully and on non structural parts, it can speed the process considerably. Experiment first.
For other minor filling (less than 1/16″), Bondo works fine. It adheres to the fiberglass better than any epoxy, cures and can be worked in minutes and blends to a nice feather edge. No need to mess with resin, q-cell or mill-fiber mix in most areas.
Using qcell or resin/mill-fiber mix for anything but the biggest filling jobs is a waste of time in my opinion. I have not heard of any problems with bondo except perhaps filling large areas on the leading edge or sharp corners where strength and “bump” resistance is needed.