Search for posts by Jack Sanderson. He made a post about some carbon fiber paddles being made. Almost all high dollar carbon fiber paddles have a foam core...but it's a special kind of foam. You can use google and do a search for carbon fiber tubes and find a few things. Also search for vacuum bagging. You should find some interesting stuff there. I've been fiddling with some wood cored fiberglass laminated paddles. Interesting. I'm learning a lot. Another thing that helped me was that I actually bought some high dollar double and single blade carbon fiber paddles. Oh yeah...that reminds me that some of the paddle manufacturors will sell carbon fiber shafts...and lengthlock devices...and two piece ferrules.