How to get better distance with a catapult?

For a science project, we have to build a catapult that shoots 50 yards. We got ours to shoot 20. We have as much tension as we can physically use. Should we make the arm longer? I don't know what else to change.How to get better distance with a catapult?
You want the arm to be the ';right'; length for the amount of tension you are using, so it's hard to say if that would help or not. You could do some experimenting with arm length. You could also do some experimenting with a scale version; that may give you some insight. But you are only 40% of the way there, so it sounds like you will need to do multiple major improvements to achieve 50 yards.



Here are some suggestions:

1. Remove unnecessary weight from moving components (except any weight that may be helping you by acting as a counter balance)

2. Reduce friction if there is any

3. Change the trajectory of the projectile (you probably want just under 45 degrees)

4. Add more tension



You say that you can't add more tension. Why not? What's keeping you from doing it? Rules? Strength of materials? If rules aren't keeping you from it, I'm sure there's a way to get it done.



If you just aren't able to apply any more force, you probably want some sort of mechanical advantage to do it, like a crank, or lever, or something.



What variables do you have the freedom to change?How to get better distance with a catapult?
arm longer, but add more weight.
longer arm

ball bearings

45 degree release angle