sorta EDF inlet/exlt diameter?

[hardlock]

Well, not really an EDF, more a slowflyer motor with a tube shield around it. Any advantage to tapering the tube and if so in which direction would help thrust?

Ken

[hardlock]

bump

[vintage1]

I *think* - and its very hazy knowledge, that you get better low down grunt (thrust) from lots of air moving slowly rather than a litlle moving fast...so the effect of tapering the efflux duct OUT is to slow the air down, and privide better thrust at the expense of top speed PROVIDED that the taper is not so severe that the airflow breaks away from the wall. This also helps reduce back pressure on the fan.
I think the ideal ducting starts a little larger than the fan, and compresses into the fan, then down a little more to squeeze the airflow around the shaft and motor before widening up again in a smooth curve.

But you probably would do better in the jets forum because they have the practical experience that I totally lack. :D

[hardlock]

Thanks!