This is a rubber Band powered plane that is fully 3D printable. it is still a work in progress and yours may need a bit or tweaking before it flies properly.
i suggest printing with 1 perimeter and 5 top and bottom layers
The rubber band holder and elevator need to be printed at 95% of original size and the prop needs to be printed at 90%
Print the wings in Vase mode with 5 bottom layers.
Glue the two wings together and then glue them to the wing holder. you can then place the wings over the fuselage pieces and move it around to get your desired Center of Gravity. Glue it in place.
using two toothpicks, hook the rubber band into the propeller and holder. You can use multiple bands or one big one if need be.
The prop is printed flat in order for it to be printed easily. in order to bend the blades you need to lay it flat on your 80 degree heated print bed for five minutes to let it warm up. after 5 min you can take the prop off and bend the blades in an opposite direction to the other.
when inserting the prop into the holder i would advise sprinkling graphite powder (pencil lead) over the inner parts that will rub against the holder. this will allow it to move freely.
I would also print the propeller at 90% of its original size.