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Old Apr 07, 2007, 09:54 PM
Registered User
USA, CA, La Mirada
Joined Feb 2004
415 Posts
Question
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.
http://www.rcgroups.com/forums/showthread.php?t=665191
Here are some pictures of the plane.
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Last edited by RMD72377; Apr 07, 2007 at 11:25 PM. Reason: spelling error
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Old Apr 07, 2007, 10:31 PM
A-4 nut!!
skyhawk's Avatar
Vancouver B.C.
Joined Apr 2002
4,647 Posts
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.
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Old Apr 08, 2007, 10:07 AM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
13,602 Posts
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.
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Old Apr 08, 2007, 02:09 PM
smug in granny panties
monkamarm2000's Avatar
NorCal Silicon Valley
Joined Aug 2002
11,779 Posts
I dig it big time! would love one for small fan and park flyer.
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Old Apr 09, 2007, 06:21 PM
Registered User
USA, CA, La Mirada
Joined Feb 2004
415 Posts
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.
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Old Apr 09, 2007, 06:35 PM
smug in granny panties
monkamarm2000's Avatar
NorCal Silicon Valley
Joined Aug 2002
11,779 Posts
save this link, very handy!

http://www.convert-me.com/en/convert/weight


Barry
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Old Apr 09, 2007, 07:18 PM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
13,602 Posts
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.
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Old Apr 12, 2007, 06:18 PM
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USA, CA, La Mirada
Joined Feb 2004
415 Posts
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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