Water balloon ballista

[Not2B]

Originally Posted by Ryan M.

Accuracy is important, as we have to hit him for full credit.

Accuracy and repeatable I would assume. Imagine a dart board.

Someone who is accurate will get all around the bulls-eye, maybe some in the ring outside of that. Let's say within a 3 inchs of the bulls-eye.

Someone who is repeatable might aim for the bulls-eye, but always hit the 20. The zero in the 20. Let's say all within 0.1 inch of each other.

Some one who is accurate AND repeatable will hit the bulls-eye, and only the bulls-eye, everytime.

Repeatable might be more useful for this project, since you say a minimum of 20 yards, which leads me to think you can adjust the exact distance as necessary based on experimentation.

SO....... whatever you use.... make sure there is some way of measuring the input energy for every launch. Pull the rubber band back the same amount every time, use the same counterweight every time, place a stop to stop the catapult arm in the same spot everytime, whatever... Also try to keep the water ballon shape and size and weight consistant. (If under your control.)

And experiement.

(I make our students do a ping pong ball launch every year to learn about this kind of stuff. It's a good thing.)