EDF Impellor without a duct?

[bobwalden]

Anyone know how an EDF impeller performs without a duct? I have several RC Car motors I could use but would give 25,000 to 50,000 RPM. Thought an un-ducted EDF impeller might do the job. Anyone ever measured such a thing?

[Beachsideflyer]

There’s a you tube video that explained propeller and ducted fan theory, check it out, but it’s my understanding that much of the thrust of an edf relies on the enclosed impeller to work properly.

[xviper]

I would think that a fan without the shroud would just be a multi-bladed, very small diameter propeller that would lose much of its air by being flung off the ends of each blade, rather than throwing it out the back.

[fhhuber]

The shroud mitigates blade tip losses. This would be a significant factor leading to overload of th motor taking a typical EDF motor and fan, running it with no tube.

xviper is also correct.

So you get less useful thrust for more power expended in the motor. (much lower efficiency)