Paper Mache ?
It's commonly called fiberglass and they are sanding it to smooth the airflow making the wing's airfoil more efficient and to specs.
At only 600 kg thats pretty light and has a good chance of flying looking at the size and length of the wings.
It looks along the lines of a powered glider which is exactly what the U2 Spy Plane used for high altitude reconnaissance until it was shot down over the USSR.
They're using a propeller based power plant and are flying it solely by radio control for initial testing which is pretty smart.
But the turbulence created by the prop wash mounted in the nose might effect his control surfaces...
I would have started with a scale model ....
But there is only one way in which to know for sure.....and presumably why they're testing this using Radio Control vs sitting in the cockpit to find out !!






