Here's the way we used to make fins for RC racing sailboats from carbon fiber. They're about the same dimension as a yak rudder, about 4" wide tapering to 2" and 20" long.
1. Cover a piece of mdf or particle board with plastice wrap.
2. Cut 5-7 rectangular pieces of carbon fiber (large enough area for the rudder).
3. layup the carbon fiber with epoxy on the plastic covered board.
4. Cover with another piece of plastic wrap and a second piece of board.
5. You now have a sandwich that needs to have the edges taped together so the top and bottom board don't move or slide.
6. NOW THE COOL PART. Park your car over a flat place in your driveway or garage. Position the sandwich under your car where you normally put your jack.
Position the jack between the car and the sandwich and extend the jack. You're now able to use the weight of the car to compress the layup into a high pressured, very stiff carbon fiber blade.
7. Remove the layup and cut and shape your carbon fiber into a rudder.