It all depends on the material used and application. If you are heavy handed with the resin, then it will weigh more of course. An approximate estimate would be around 4oz per square yard of material when it's all said and done...glass/resin/paint. It will always be heavier than film covering of course. It's not as heavy as some people think though.

Check out some of the other posts by doing a search under "fiberglassing" or "fiberglass."