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Aug 05, 2010, 01:41 PM
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Discussion

Any reason why a fan unit is not mounted all the way back?


If room and design allows why is the fan unit not mounted all they way back with using the fake ehxuast covers to cover and channel air. Or has any one tried using the MKII 400 pusher and the cone it has fo the exhaust tip? Trying to use some highber mAh battheris and out of room still tail heavy...
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Aug 05, 2010, 03:04 PM
Registered User
I don't think there's any reason why the fan jet motors are mounted midsection instead of way back in the tail other than the obvious balancing concerns. If you put it way back there, then you could end up with a very tail heavy condition, and most planes end up tail heavy anyway. So why put all that ballast in the nose if you can mount the motor midships and avoid all that? I think that's probably the main reason.
Aug 05, 2010, 03:13 PM
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unknown flyer's Avatar
Most fans don't do well with really long intakes either which you would have if the fan was all the way back.
Aug 05, 2010, 04:47 PM
Registered User
jdlilfan's Avatar
Also keep in mind the length of the wires and the gauge needed which adds weight and sometimes strain the planes electrical system. That is in regards to motor/fan placement.
Aug 05, 2010, 05:42 PM
You are a "go" for reentry
Maxthrottle's Avatar
Like jdlilfan said; you can loss what you gain by putting the battery so far away from the ESC. Max length on wires is 20cm either side. You can go more but your performance goes down or needs larger battery and ESC to push it. You can up the gauge which increases the weight also.
Not that it can't be done but talk to Claus. He's shown diagrams etc placing the EDF somewhere in the middle.
Last edited by Maxthrottle; Aug 05, 2010 at 05:48 PM.
Aug 05, 2010, 07:41 PM
SoCal, Year Round Flying!
bmiller's Avatar
CoG and wire lengths concerns aside, You can mount it where you like but an (optimal) exit length of 3-4 inches allows you to squeeze the exit smaller (typically 90%)and increase the efflux speed. Just like sticking your thumb over the end of a waterhose to increase its velocity.
Aug 05, 2010, 08:20 PM
Registered User
320pilot's Avatar
Here is a picture of the tail cone of an F-35 being sold by Nitro planes. looks like the brushless motor/fan are at the very rear of the tailpipe.

http://www.nitroplanes.com/93a35-f35...o-rtf-24g.html

C of G must be tricky.
Aug 06, 2010, 01:10 PM
You are a "go" for reentry
Maxthrottle's Avatar
Has this understanding changed much? https://www.rcgroups.com/forums/show...6#post10837456
He reps the Velocity fan so h may be able to help you with optimal.
Aug 06, 2010, 02:03 PM
Suspended Account
I was thinking furgther back to accomidate heavier batteries,

On the test stands if you use a cone to channel the exhuast 10 or 20% do you see a loss in thrust and a gain in velocity?

If this is a true statement then and I wanted plane that could do the alfa or cobra manuever I woild give up some speed but have a lot of tbhrust to achieve the beter than 1 to 1 ratio, plus if I got introuble I would. Have the extra thrust to save my azz easier. So I probably would do no chaneling?
Aug 06, 2010, 07:05 PM
Aka: Tom Jenkins
ApexAero's Avatar
Quote:
Originally Posted by 320pilot
Here is a picture of the tail cone of an F-35 being sold by Nitro planes. looks like the brushless motor/fan are at the very rear of the tailpipe.

http://www.nitroplanes.com/93a35-f35...o-rtf-24g.html

C of G must be tricky.
Naw man! 95mm from wing joint. I added a pound to mine and it flys well and really fast
Last edited by ApexAero; Aug 06, 2010 at 07:19 PM.
Aug 07, 2010, 02:19 AM
Foam bounces...
Turbs's Avatar
The shorter the discharge side of the fan, the more turbulent the air leaving the plane.


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