Last terms class project at my daughter's school was to design and build a Co2 powered rocket. The rocket dimensions were limited to 300mm long, 50mm thick, with a maximum 30mm fin protrusion. The rockets were attached to a 400m braided fishing line strung between two poles, and launched horizontally using a trigger device that punctured the 8g Co2 canisters. The time and distance the rockets covered were measured and recorded by the class.
So after reading these two references:
...the design above is what my daughter came up with. It features a parabolic nose cone, designed to place the centre of pressure well behind the centre of gravity, providing directional stability. The fins are tapered airfoils which improve control surface performance with minimal drag - which reduces overall drag, because the rocket is self stable. The tail was tapered inward to reduce drag during the glide phase after the propellent was exhausted.
Her rocket covered the full distance, and was equal fastest - flying unaided over the second half of the course after the line broke. The nose and tail were damaged on impact at the end of the course. (Sorry for the poor quality photos of the event, I had to photo them off the TV)
Print both halves and glue together with 5 minute epoxy. The hooks were made from 1.6mm stainless steel TIG welding rod. These need to be twisted and trimmed and glued in place so they are parallel with the centre line. The 8g CO2 canister is pressed into the rear.