I was asked what products to use on a wind generator in the IRC channel. Since folks will be spending a good sum on magnets, wire, bearings, steel and wood, as well as a great deal of non-replaceable time, I feel one should use the proper products.
First of all, I think polyester resin is junk. It is so bad even low cost boats will not warranty the hulls if left in the water.
For potting magnets, Epoxy resin is the proper material. It actually bonds to things. It actually seals things damn near water proof.
For casting stators, many prefer vinyl ester resin. It has higher temperature tolerances than epoxy resin.
Be sure and use as much glass fiber as you can stuff into the stator if it doesn't interfere with the wire. Remember, the resin has little strength on its' won and relies on fillers such as glass, Kevlar and Carbon Fiber for strength. Be sure and keep temperatures in the proper range for the resins to harden.
Ron