Damn, I really wish I could find the picture I had that would help you right now..I'll just make a new one so gimmie a min after this..
Anyway, What you want to do is use Insulation foam (the pink or blue stuff NOT THE WHITE STUFF!!) and get a 1" thick sheet. It will be enough. Then cut out 2 swords, get doweling, and sandwich it in like the pic I'm gonna post (just wait for the pic).
Glue the entire thing. I suggest liquid nails. This will give you tons of stricture without having to use fiberglass..Then bevel it. Then just use Gesso on the foam and use like 5 coats (that's what I did) then sand and paint..
Here's the pic: