are you sure your 2D-shape is not self-intersecting? Try this:

polygon(circle_(1, 20));

http://forum.openscad.org/file/n17269/cir.png

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Use this code instead:

function circle_(L=1, N) = [
for(j=[1,-1], i=[-1:1/N:1])  [jLi, jL/Fatnesscos(i*90)]
];

and look at your radius. You use 800, this has no effect. Try this:

module Blades(){
intersection(){
for(i=[0,120,240])
rotate([0,i,0]) sweep(C);
rotate([90,0,0]) cylinder(center=true, r=40, h=400);
}
}

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