A selection of water rocket parts. These are designed for s 1.25L soft drink bottle. I use a Kirks brand bottle (in Australia) as they have straight sides in the taper which make it easier to glue the fins.
I suggest printing in ABS as PLA will most likely break on impact. These rockets are not designed for a parachute.
There are 2 types of nose cones. I created the pointy one so that I can print it easier in Artinel, but you can use any other flexible material.
There are two types of fins; traditional fins and circular fins. I found that the circular fins work best, are easier to construct and are more durable. I haven't broken a circular fin yet.
The circular fins come in two parts. The mount is glued onto the bottle just above the taper and left to set. The fin is glued to the mount using thin wooden skewers. These work the best as they are a little flexible.
The rotator mount is a modified mount that makes the rocket rotate in flight for greater stability. The extra stability is not really necessary as the circular fins are quite stable. It's just a bit of fun.
If you get the length of the skewers right, and hence the position of the fin right, the rocket will tumble to the ground gently.
Here is my design for a parachute deployment system: http://www.thingiverse.com/thing:294758