In This Way You CAN mAKE PROPELLER BLADE.
Draw a shape as given
Join And extrude it upto certain height .It will Look Like Given Image
Draw A rectangle Bigger Than the last shape Drawn. And extrude it up to height greater than last object height.
Draw The Shape As given .And extrude it up to height of box.subtract it from the red box
Move the Remainig Box to the Firstly Extruded part and subtract it
Your Propeller blade is ready draw a cylinder and array the blade.