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Old Nov 11, 2011, 12:30 AM
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RSteel's Avatar
Sacramento, Ca.
Joined Jul 2005
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First EDF build

After numerous Pusher jet, sailplane, and various foamy builds I finally got around to building an EDF jet. Man, there's alot more to this build type than I thought. Even though the build methods are relatively the same the concepts and math are a bit different. Oh yeah, and the real brain buster for me was, where to put all the electronics since the intake areas have to be clear

I started off with wanting to build a Habu/Bandit/F5 ect type aircraft I came across Jetset44s BVM Bandit design. Here's what I came up with. This is almost a 65% size build to barely accommodate a 55mm fan.

Wish I had taken more photos but here are some of the more non redundant ones. The pics below are prior to hooking up the servo arms and rods.

As you can see I completely chopped off the squared tail and formed a new cylindrical one around the motor and thrust tube. Of course I had to fill in the gaps and try and make the square edges morph into a round one. Pain in the butt...

Anyway, after finally talking myself into throwing it in the air, I maidened her on Weds, the 10th

Maiden Flight (4 min 28 sec)


Note: Dont stick your finger in the tail pipe during launch. Bad things can Happen !!

Luckily my buddy Dave was there to hit the trim buttons while I made passes and didnt have to look down or miss the trim. Thanks Dave

As I go through my notes and pics, I will add more to this thread. I have electronics, CG, Math, FSA and more pics to add. Plus alot of build tips I discovered along the way that I hope will be helpful to others.

As always, all comments are welcome ....Be kind
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Old Nov 11, 2011, 12:32 PM
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Sacramento, Ca.
Joined Jul 2005
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Because this was my first try at an EDF build, I went cheap. This of course cushions the blow when or if it turned into a smoking hole of foam during the maiden flight

Material : Blue Core
EDF Unit : AEO 55mm w/ 5250kv motor
Battery : 2200ma 20c
ESC : HobbyKing 40a Opto
BEC : 3a - 5a
Servos: Hitec 55s

Output advertised: 19oz @ 11v and 30A
Output test by me: 18.75 oz @ 11v and 37A

AUW: 18.8 oz

Keeping things simple again, I opted for an AET configuration.

Here is a video of the ship after all controls are connected and working.
Flight Control Check (0 min 31 sec)
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Last edited by RSteel; Nov 11, 2011 at 12:43 PM.
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Old Nov 11, 2011, 02:49 PM
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Sacramento, Ca.
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Originally, I had mounted the EDF Unit in the square body. But due to an unfortunate FOD incedent, I fragged the fan blades and had to cut a side to get the motor out.

Instead, of putting on a new side, I opted to cut the whole empenage sections out and form a new cylindrical shaped one in its place. This led to gaps needing to be filled by more foam and super lightweight filler. The tail section that was connected to the whole backbone area had to be cut out at the base, and re attached to the new upper.

For the motor configuration I used:

85% FSA
5in. Thrust tube.


I used the program Cone Layout to print the cone on a sheet of paper then transfered that to a thicker/harder school folder, putting the shiney side inside. I then covered the outside of the tube with fiberglass packing tape. Not the cross hatch type but the tape with the length wise run of glass imbedded.
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Old Nov 13, 2011, 12:00 PM
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Sacramento, Ca.
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Prior to installing the motor, I wanted to test the motor and thrust tube configuration without installing it in the ship using the box method or some other on wing method of thrust testing. I researched DIY edf test stands but most of them seemed to be way more complicated than I wanted.

All I needed was something to keep the motor stable with tube to measure thrust on a scale hence:

Hence a simple thrust test stand from plexiglass, screws and nuts.

The intake hole was cut to be slightly larger than the fan housing to accommodate good air flow. The unit is secured to the top and the whole thing is set on top of a scale. Zero the scale with the unit on top and apply power.

This setup is far from perfect but it got me the thrust numbers I needed to see to ensure I wasn't installing a faulty unit or a sickly unit just to be cut out of the aircraft once installed
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Old Nov 13, 2011, 01:11 PM
EDF Jet Jam 2015 , May 28-31
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
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Nice work! Welcome to the EDF design world
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Old Nov 13, 2011, 02:21 PM
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Sacramento, Ca.
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Thank you

I got a whole lot more to learn, but its still very cool. I did notice you have to stay in the power envelope during flight. No prop wash over the flight control surfaces to pull you out.
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Old Nov 13, 2011, 02:53 PM
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frank40's Avatar
Denmark
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Hi Rsteel

Thats a nice jet you are building, great job.
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Old Nov 21, 2011, 10:06 PM
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Sacramento, Ca.
Joined Jul 2005
323 Posts
Question, does the EDF unit increase in amperage when it is airborne? I just melted some chips right off the ESC hmmmm. Nose broke but thats the worst of it. Got EDF unit cut out and a new motor ready to go.

Ray
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Old Nov 21, 2011, 10:52 PM
EDF Jet Jam 2015 , May 28-31
Kevin Cox's Avatar
St. Louis Intl, Missouri, United States
Joined Jan 1997
6,882 Posts
Ahhh...the age old question

The general answer is no. But as the lipos warm-up they supply a bit more power which could in turn give you a slightly higher current draw.

Loose connections will cause heat and can de-solder itself.
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Old Nov 21, 2011, 11:36 PM
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United States, PA, Grove City
Joined Jan 2011
751 Posts
Running a P10 at 155W can cause the fets to desolder themselves also and slide clean off the board
Obviously one of those things one knows firsthand.
You get what you pay for with quality ESCs, as Fairchild fets are some of the few to slide off the board, before failing.
So the $64 question: Was it a Castle?

One good BEC killer is reducing throttle for final approach, at the end of a long flight with a poorly cooled ESC. The BEC is hotter than ever, and then the voltage rises as the throttle is suddenly dropped way down. Been there done that one also.
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Old Nov 24, 2011, 12:53 PM
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Sacramento, Ca.
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Well, nose is reattached and ready to go. I just tested the motor again and got 37A peak full throttle static. Gonna connect up my e-logger and do some dynamic readings.
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Old Nov 29, 2011, 06:58 PM
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builder bob's Avatar
United States, MA
Joined Oct 2011
602 Posts
looks good so far!i had the same building idea and am now building that plane! i have no experience with edf either. if you want i can tell you what I've found building mine. I'm trying to make it look like a Habu and you said at the top of the thread that's what you were thinking of, i can tell you what I'm doing to make it look like a habu. blue foam is fun! keep up the good work!
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Old Nov 29, 2011, 11:08 PM
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Sacramento, Ca.
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Thanks Bob, Although, I have finished the project and it flies quite well

Working out some motor issues right now with amprage.

Ray

Oh yeah, blu foam is fun. Gonna hafta do the next one in FG.
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Old Nov 30, 2011, 04:46 PM
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United States, MA
Joined Oct 2011
602 Posts
if you finished and the plane fly's good, no point in saying how to make it like a Habu. for fiber glassing, do you think that it would work to lay fiber glass on a foam plane then when it has hardened pull it off? i read that this works great for car parts but someone on this sight said it doesn't work at all. any ideas?
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Old Nov 30, 2011, 07:27 PM
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United States, MA
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you might like these paint scheams:
http://www.bvmjets.com/Pages/old%20events/bandiths.htm
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