It would be much more effective to use a shroud instead of moving the fan. A shroud should only cover half the fan blade, however- - - -put the back end of the shroud even with the support spider where the blades are attached.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!