Hi everyone,
I've been trying to thicken this fan blade by 0.2 mm , but each time I get "thicken surface has failed". The blade does have a lot of sides due to its organic shape so I'm wondering if that's what causes the error. I've tried using stitch surfaces but that doesn't seem to work either. Is there something I'm missing? 
I thought more about your situation.
I'd use the imported geometry (radial near-parallel lines and end strings) as a source for making guide curves, then Loft or Boundary (I'm not sure which would be better) a new surface with a single face across the top, and repeat it for the bottom.
Then you'll have a single face surface body(ies) to select and thicken or offset.
...ditto!..
Paul, somehow I knew you could mock this up faster than I could attentively describe it in text. Thanks!
I just wasn't satisfied with my first answer which was unimaginative and frankly recoiling from the idea of selecting hundreds of tiny faces, so it's more useful to find real solutions.
Hello Tom,.. yeah, it would have to be re-engineered.. and/btw,.. NOT trying to get/steal points... just thought,.. ditto (idem).. that is,...
I had played around with it last night,..for some reason, I'm always curious about fan blade design?,.. got tired and hit the hay.. got up this morning and saw/read you're reply,...(immediately commented) ditto!,.. then opened last nights file... screen shot,,, attached.
Hey pal wich is the origin of this file? A Scan 3D a STL? You can't give thick because the geometry isn't fine, nor solid nor surface
Your Part has one Solid Body and no Surface Bodies.
Thicken works upon a Surface to make it a Solid. What you have is already a solid.
Perhaps you can select the faces on one side and see if that works. However, due to the intensity of imported polygons, you are talking about many many faces to select. I would not even attempt that personally unless someone has a way to select, for example, all visible faces from one side.
Other options include Offset Surface followed by Loft or Boundary or Filled Surface, then re-knit to a solid, but the same difficulty of selecting the faces would clearly apply.