The first thing you'll need is 1/2" pvc pipe. Our launcher uses this size for the launch tube so your rocket will need to fit on it. It should be snug but not so snug the rocket has trouble coming off.
You want to roll the paper around the pipe and tape it. You'll end up with a nice hollow tube.
You will need to seal the top. Leave about a half inch of paper above the pvc and fold down the paper and tape over it. If you don't seal the top, the cone will blow off.
You'll now need to experiment with nose shapes, body size, paper weights, fin shapes and numbers. Remember you need to create three rockets that are
exactly identical except for one thing. For example, make three rockets that are the same in every way (size, shape, length, paper type, fin number, fin shape) except for the shape of the nose.