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Old Aug 09, 2007, 06:32 AM
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Dr John
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Lake Placid, Florida
Joined Dec 2001
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Ducting for EDF's is calculated from FSA ( Fan Sweep Area ). This is the area of the inside of the fan shroud, minus the area of the fan hub/motor. Intake area should be 110-120% of FSA tapering smoothly to the front of the fan. Exit area should be 80-100% of the FSA. A larger exit will give better static thrust ( easier hand launch ) and a smaller exit will give more velocity ( better top speed ) As with anything else it is all a compromise for the characteristics you are looking for in any given design.

John
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