Shifting EDF forward? Air effeciency issues? - RC Groups
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Apr 30, 2012, 07:40 PM
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Shifting EDF forward? Air effeciency issues?

I'm setting up my starmax 90mm f-16 (luckily i found the EPO version).

The edf unit/motor i'm using is a heavy extremerc 90mm alloy combo that weighs 546grams!! Tested the CG w/the battery and it barely meets the stock CG and that's with the battery all the way forward. I pushed the edf forward from it's default positioning a few inches and then the CG was a bit better. I have yet to install the servos and ESC in the plane btw.

But would that affect the air efficiency in any way? Like lets just SAY that I had to move the unit to practically the center of the plane, would it limit a lot of the thrust in any way? Would it help to use a thrust tube? (kinda long though, probably like 17 inches!!)
(anything besides getting a heavier batt of course)

Left pic is stock placement and in the right pic the edf is shifted forward a little bit.
Last edited by RC_Bob; Apr 30, 2012 at 07:50 PM.
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Apr 30, 2012, 07:53 PM
deltas are cool
AIR SALLY's Avatar
that wont hurt but you got to have a thrust tube . seen guys asking this ques. alot . all DF need a tail pipe that fits tightly on to the fan shroud. it directs the air out the back of the plane.and it need to be centered at the aft opening ,or it will vector thrust (which you dont want )the size of the opening should be @80-85 % of the fans FSA.
Apr 30, 2012, 09:10 PM
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4stripes's Avatar
I have the same plane (in EPS) and am running a 500g Changesun 12 blade fan. I have no trouble balancing with a Zippy 6S 30C 5800mah battery.
Perhaps you might consider using a heavier battery to help with balance (instead of moving fan). The plus side is flight times over 5 minutes.
Cheers Eric

PS I added a thrust tube on mine (in the stock location) to squeeze it down to 75mm and add afterburner lights.
The afterburner lights were a waste of time but the thrust tube seemed to add some speed compared to without it.
May 01, 2012, 01:54 AM
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k thanks a bunch guys!!!
May 01, 2012, 11:16 AM
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Thomas Nelson's Avatar
Can I ask where you found the EPO version? How to you like it versus EPS - bead size ok? Paint not pealing off too easily?

May 01, 2012, 06:20 PM
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I got mine from here:

I've always favored EPO over EPS cuz it's SO much more tougher. The bead size is the usual large sized EPO spongy beads. And I've found that the paint stays on just as well as it does for EPS.
May 03, 2012, 02:18 PM
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Thomas Nelson's Avatar

Hey - I just realized I posted in your ad where you listed the original EDF/motor for sale. Sorry - didn't realize it was you!!
May 03, 2012, 02:59 PM
Registered User
yea i noticed! So the alloy edf combo im using is this one:

They've tested about 1900 watts but I'm expecting 2000-2200 watts cuz ima use Gens Ace 6s 5300mah 30C packs. They outa give an extra umph out of the unit. I'll let u know what my watt meter says.

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