How important is intake area? Can scale intakes work? Is there a chart, or math someplace for any given fan assembly?

Are the new fans not requiring this much needed intake area as they once did?

This is my intake. See Photo of wood model.

Responses will be appreciated.

Charles

I'm no engineer, but there is a reason that many EDF jet have larger openings on the intake ducting, or on some, have cheater holes on the bottom or sides of the jet. Those intake openings you have on your model look small, even smaller than what would be scale to me. There is some science and engineering in airflow into intake ducting, flowing through the fan, and openings as the flow leaves the rear of the jet....

Think of it this way... Imagine trying to breath through a straw, and then imagine trying through a paper towel roll. I would think that if the hole is not big enough, then the motor would be pulling extra amps trying to "suck" in air through the ducting, just like you would have a hard time breathing through a straw.

Presuming your asking about an EDF set-up, the combined area of the intakes should be equal to the free swept area (the fan area minus the area of the spinner or hub).

out let is more important.it would not use more amps ,it would use less.{if intakes to small}-fan would stall or cavate.area is important.non turbulant air flow is a must.inlet must have a good, lip radius, to promote good flow. a big inlet with turbulant flow ,will cut flow in half.once in flight,the game changes. now you have some forced air to help.. 80 % fan area for exhaust size..RALPH

Ducted fans need inlets sized to approximately 95%-110% of the Fan Swept Area (FSA) with an exhaust outlet sized to approximately 75% 85% FSA. Choking down airflow at the exhaust, increases exhaust velocity. This in turn will increase top end speed of the aircraft. There is, however, a point of diminishing returns: choking down the exhaust too much will back pressure the fan resulting in degraded performance. Additionally, a larger outlet area will increase the static thrust of the system, but lower the top end speed of the aircraft.

For more information on the general rules of ducted fans, visit [link=http://www.jethangar.com/]Jet Hangar International[/link].

Typically, when using scale intakes on an EDF system, cheater holes are used to create sufficient thrust on take-off. My recommendation would be to create a cheater hole (or holes) in front of the DF and start there. Once you determine that the plane has sufficient take-off power, you can then start covering the cheater hole(s).

Good luck!