Great Tut. how to build it..
never thought about it to use the corrugated cardstock and glue normal cardboard over them..nice
Nomex Honeycomb, which is quite flexible till epoxy is applied is similar to cardboard and it's application in this case. In a helicopter blade, the Nomex Honeycomb material is doped with a proprietary epoxy resign and carbon fiber is applied over it. The rigidity of the Nomex Honeycomb applied with the tensile strength of the pre peg carbon fiber cloth makes for a very strong, stronger than ay metal, blade, yet flexible, once out of the autoclave, of course. I have seen Blackhawk Helicopter blades with multiple rounds threw the blades and the craft have landed safely. The picture below is of an S-76 blade.
That being said, a corrugated piece of soft cardboard doped up with a stiff glue or resin, can make, cut to shape first, could be a great basis for a strong part. The same cardboard unglued would be a moisture sponge. Glue of some sort is needed to seal it, resin, liquid crazy glue, would make it very stiff, though the health concern for a model part is kind of high. The part showing the cardboard interior looks very industrial!