Hey Chrisb, yes the plane is made out of foam, 6mm insulating foam sheet for home constriction. Also known as Depron.
Had the same concern, breaking the prop when landing. The prop doesn't always stop in horizontal position but it never
broke or got damaged in the landing process. To be honest i never landed on concrete or tarmac or any other hard surface.
Guess if the prop is in any other position then horizontal it will turn as soon as it hits a object, further more the prop is
fasten with a rubber, this will also prevent damage...