For the propulsion of the hovercraft, the only way to go is a propeller, obviously. The propeller can be run by a fan belt
attatched a horizontal shaft motor, which you can usually buy as part of a used edger/weed wacker sort of thing (get these
from a used lawnmower place). Plan for this fan to take up quite a bit of space on your hovercraft, since you'll also have
to build a safety cage around the propeller.
As for the purchase of a propeller, you can usually scope one out around Ebay or part of a car radiator.
There are two types of drive for your propeller: direct drive and indirect. For our own hovercraft we chose to go with
indirect drive, so we'll start for some plans for an indirect driven propeller.
First, mount your motor to your plywood, or any kind of motor mount if you'd like to. You're gonna need a belt to run
between the motor and your propeller, and mount the fan high enough above the motor to keep the belt tight. MAKE SURE both
parts of this drive are mounted in tight so they don't move AT ALL during operation. The slightest budge can throw off the
belt and make the propeller inoperable.
The propeller needs to (obviously) be attatched to a sort of an axel that in turn has a belt drive on it.
Directly driven propellers are mounted straight onto the motors that run them. At this point, we don't know any efficient
way to create a direct driven propeller at home.