xxx

Seriously consider filament winding the skin. Wind it bi-directional with a bias. This will result in a woven skin, however the bi-directional winding will assure that the blade is not given a bow (a twist to 0.5R then a reverse twist to the other end).

Thickness is 6 layers of 0.013" each = 0.078"

Bi-directional carbon cloth. 20/70/-70/-20. Some options are bi-directional carbon cloth. 0/90/ and bi-directional fiberglass cloth. The final layup may be dependent on minimizing twist forces while providing any necessary inplane rigidity, beyond that provided by the spar.

Fabric to be bi-directional S-glass, (or M-cloth, if needed, for better flexibility ~ if it can be found).

Might be an idea to see if carbon will provide the desired flexibility at 0º / 90º. If it will then its extra strength will improve the blades rigidity.

One or two layers of light S-glass might be laid up at 45º / 135º to hold the blade together, if they don't add too much stiffness.

Note that carbon may result in too much resistance to twisting and the skin will have to be fiberglass. Is there a bi-directional cloth of carbon and fiberglass where the glass could run spanwise and the carbon run chord wise?