Create one master blade and then edit>duplicate special options and select the "INSTANCE" checkbox and then make three copies rotated by 90 degrees.
Below you can see I created a simple blade shape and then applied a "duplicate special" with instance selected and made three copies rotated 90 degrees around the y-axis. I then applied a deformers > nonlinear bend to SELECTED VERTS of the original (master) blade and you can see that it affects the three instance copies of the blade.
NOTE: It's very important to note that instance copies are only affected by "component" level changes to the master. Components are verts, edges and faces. Since non-linear bend affects the blades at the vert level you can apply the NLB to the blade object.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram; 13-08-2012 at 06:44 PM.