Step 6: Choosing what will power your airplane, Gravity?
Pro's: Cheaper than all types of powered airframes the same size, easy flight, most are two channel(elevator and rudder), large sizes means long flight times, rubber band launching, silent flight, clean.
Cons: limited flight times unless you can find thermals to ride, must land on soft surfaces most don't have landing gears, you have to run after it if you run out of thermals to ride.
Some sailplane's can be equipped with an electric motor with folding propeller to climb up for your glide down and provide some control on were you will land. All types of these airplanes are very light weight and and have large wingspans.