Try Catapult Lab free in your browser, with nothing to install and no account. Build the craft-stick catapult most classes build, press the cup down and let go. Watch the throw in slow motion over a tape measure, beside the arc it would fly with no air. Change the stack, the bands, the cup or what you throw, one thing at a time, and find out why it went farther. Then print the build and test a real one.