[JamesBrown]

well this is going into my plans for rocketry this summer (I Am in charge of model rocketry at a summer camp) In the mornings we will be doing traditional Estes model rockets, and in the after noons we do what ever I happen to come up with (IE water/air pressure rockets, Baking soda/Vinegar rockets, giant water balloon catapults, basically what ever I want to do.

For this one, I like the idea of a rubber stopper, that is what we use (slightly modified) for the water rockets. The only problem is it may shoot out before you can get it set up to launch. The method we use for launch is gluing straws onto the bottle and putting two wire coat hangers into a piece of ply wood separated the same distance apart as the straws on the bottle and slide the straws onto the hangers. this gives you a (slightly) controlled launch, this is what I would recommend, if any one has any other questions (or ideas) for me feel free to let me know.