This boat goes ahead by pushing air back, just like an airplane. The propeller must be twisted so that each blade is scooping up a bit of air and throwing it backward. If it throws air forward, the boat will go backward
These are really used in swamps! Generally it’s more efficient to push off water than air if you want to move a boat – see the next project. But when the water comes shallow and full of weeds, scum and gators, it’s better to have a smooth base on your boat, so as not to tangle the propeller.
Real airboats use propellers as large as airplane propellers, and wrapped in a protective cage to keep from sucking in and chopping up debris, birds, small people, etc. Some use airplane engines, and can go quite fast. It is a trick to steer or stop these things – remember, there is nothing but a flat bottom skimming along the surface of water. Steerage usually happens with vertical vanes directly behind the propeller. On this model, you can actually turn the Roach to change the direction of force
Things move forward as a reaction to an action directed backward.
The more air the propeller pushes back, the more force the boat will have to go forward
Water gives less friction than air for things to move, so boats can move with less force
How could you make it go faster?
How would this boat work differently if the propeller was under the water?
How could you modify this boat to work on snow?
Which works better a large (3 inch long) propeller, or a small (1 inch long) propeller?