in the old forum, i've read conflicting opinions about epoxy over bondo. opinions? is it ok to use bondo then to glass and epoxy over it. i like what i have read about the workability of bondo over thickened epoxy. also, the cost of bondo is just right (compared to epoxy). my boat is going to be trailered mostly.
thanks for the response.
clint
Bondo is a polyester resin. Epoxy will bond to it provided it has a "tooth" and can make a mechanical bond. However, Bondo being polyester does not bond well to epoxy. Again a mechanical bond is what is created. Epoxy tends to have a very smooth surface and therefore must be roughed up for other materials to bond well with it once cured. So filling open weave on glass cloth with Bondo over epoxy resin doesn't work well. The weave of the cloth isn't rough enough to create a suitable surface for the Bondo to bond to. End result is that down the road it may flake off in areas taking any finish applied over it with it. This isn't just a potential, it is a probability rather than a possibility.
You can prepare your surfaces with Bondo and then apply Epoxy resin and glass. But you should then continue with epoxy and suitable fillers to make up a good fairing compound or flood coat the glass for a second coat to fill the weave of the cloth. Some will suggest using peel ply instead of a flood coat to give you a smooth surface. But you still have a minimal amount of epoxy resin and print thru will occur as the epoxy continues to shrink over the next few months to years. Better to build up a coating of epoxy over the glass and then finish that.
I recommend you read and consider using the techniques in the following article. They work and work well.
http://duckworksmagazine.com/05/columns/...6/free.htm