EDF inlets/outlets - RC Groups
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Jun 23, 2002, 07:27 AM
Registered User

EDF inlets/outlets


Help!@ I'am new to the ducted fan side of electrics and have a question. I'am helping build a scale F-117 and have a question about the outlet size for any fan. Question: Is there a reduction in performance/flow when you make the air outlet smaller then the inlet?? Also,is the thrust increased by "forcing" the air through a smaller opening?? Thanks for any input.
Gregg
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Jun 23, 2002, 10:24 AM
Purple power
gregg f's Avatar

Re: EDF inlets/outlets


Quote:
Originally posted by geeee
Help!@ I'am new to the ducted fan side of electrics and have a question. I'am helping build a scale F-117 and have a question about the outlet size for any fan. Question: Is there a reduction in performance/flow when you make the air outlet smaller then the inlet?? Also,is the thrust increased by "forcing" the air through a smaller opening?? Thanks for any input.
Gregg
generally thrust will be higher if the outlet is about the same size as the fan.efflux(speed of the air being moved) will increase with a smaller outlet, giving the plane more top speed.

which fan are you using?...........gregg
Jun 23, 2002, 12:25 PM
Flying Welder Pilot
Plane Crazy's Avatar
Haldor sent me this guideline a while ago.

Quote:
Quote from Daniel Schuebeler:


Intake and exhaust areas depend from the model you want to fly.
For "normal" models I would recommend 100% SFA on both sides, for the smaller and faster ones please use 90% SFA at the exhaust and 90-95% at the intake. For real speed jets use 85-90% at the exhaust and 90% at the intake.
I have gone as far as 80% SFA on the exhaust. Static thrust decreases as you neck down the exhaust, but the air speed increases.

Gordon
Jun 23, 2002, 06:53 PM
EDF Head
Haldor's Avatar
and SFA = Swept Fan Area. Thats the actual area the fanblades cover.
Jun 24, 2002, 07:58 AM
Registered User
Thanks to all for your input. In this project we are going to be using (2) Wattage 400 fan units with Dymond 480 motors on 8 CP-1700 cells.
We are looking at an AUW of about 48ozs. Not sure of the exact wing area by my partner says it will be about a 9-10ozs. wingloading. He's shooting for scale with the exception of the fan outlets,maybe.
My friend is planning on kitting this in the future so I'll keep this thread going and post pics and results. At present he is selling a smaller version of this plane for free-flight bungee launch for kids and scouts.
He built a larger version and it came off the bungee at about 100 ft and had a glide of about 35 secs. We where thinking slope ship but someone had the idea of electric using the new Wattage fans.
Construction is of a thin hard construction type paintable foam that will be beveled at all the joints and angles,no tape seams.
Construction starts after the 4th of July,should have somethng by August for show and tell. Again,thanks to all for the input.
Gregg
Jun 24, 2002, 11:55 AM
David Cairns
dcairns's Avatar

Turkey Feathers


Has anyone ever used turkey feathers on an EDF? I seem to recall seeing some for turbines. If they did not weigh much, it might give you the best of both worlds.