DF Inlet & Outlets How Big ? - RC Groups
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Apr 07, 2007, 10:54 PM
Registered User

DF Inlet & Outlets How Big ?

My buddy is currently making a fuse mold for a Folke-Wulf P.I. Now I have been flying electric and slope planes for years but I have never had any DF planes. The nacelle is 13" long and 3" around I was thinking about using the WeMotech 480 fan with an Astro 020. My question is how big does the inlet need to be and how big does the outlet need to be to make this fan efficient? I only have 3" around so maybe a different fan would be better? Second question were should the motor be placed should it be towards the front or rear or in the middle? The fuse length is 40" and the WS is 45" the WA is 315" squared. I am thinking of a RTF weight of 40 ounces which gives me a 18.3 ounce wing loading. According to the Astro flight website the 020 with the 480 fan on a 4 cell lipo puts out 492 watts at 35 amps at 36,000 rpm's.
Here is the link to the build thread.
Here are some pictures of the plane.
Last edited by RMD72377; Apr 08, 2007 at 12:25 AM. Reason: spelling error
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Apr 07, 2007, 11:31 PM
A-4 nut!!
skyhawk's Avatar
A rough rule of thumb would be 100% FSA for the intake and 80% FSA for the exhaust.

The motor and fan can be placed anywhere - It's placement is usually dictated by your C of G. IE you don't want it so far fwd or back as to require a whole heap of weight to balance the model.
Apr 08, 2007, 11:07 AM
EDF rules... :)
AirX's Avatar
FSA is defined as the area of the inside of the fan shroud less the area of the motor holder or spinner whichever is larger. That is a pretty neat project. Good luck.

Eric B.
Apr 08, 2007, 03:09 PM
smug in granny panties
monkamarm2000's Avatar
I dig it big time! would love one for small fan and park flyer.
Apr 09, 2007, 07:21 PM
Registered User
I have been doing some research online and here about motors and fans. My question is I have seen some thrust readings in ounces and some with the designation of N. Can someone define N and tell me what its value is.
Apr 09, 2007, 07:35 PM
smug in granny panties
monkamarm2000's Avatar
save this link, very handy!


Apr 09, 2007, 08:18 PM
EDF rules... :)
AirX's Avatar
1lb = 16oz = 454gram = 4.45N
1oz = 28.35gram, 1 gram = 0.0098 Newton
The Newton is the metric value used in physics for force calculations.
Apr 12, 2007, 07:18 PM
Registered User
A small problem has come up. My buddy has told me that the largest part of the nacelle is 2 5/8. I was going on fans based on 3" to remedy this problem we are going to lay up a fuse very heavy and do the rework on that then make a new mold better suited for EDF. This wont be to bad one mold for slope and one for powerd flight. So what fans would work best at 3" and putting out 40 ounces of thrust on 3 to 4 cell lipoly motor recomedations would be great as well. I am looking for a current draw between 30-40 amps.

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