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#1 northropn9m Oct 28, 2004 10:36 PM

Ho 229 Build
1 Attachment(s)
I have been posting pictures and answering questions about the building of an Horten Ho 229 in the thread "Northrop N9M Plans Available in Two Weeks." I thought I better start a new thread as I am adding more pictures of the build. For those of you that have not been following along, the specs of this Ho 229 are:

Version: Ho 229 V3
Imel Version No.: Im 6
Wingspan: 72"
Target Weight: 3.5 lbs
Propulsion: Two Electric Ducted Fans
Airfoil: Imel A004
Wing Twist: Imel-T002
Software Used:
CompuFoil 3D
TurboCAD 9.1
Maiden Flight Target: December 5, 2004

Complete coverage of the build can be found at http://www.bellimelgroup.com

I am two weeks into the build.

I am beginning to fit the engines to the wing. I have to cut some holes in the leading edge for the air intakes. For now I am working on the exhaust fit.

I am happy to answer questions, so feel free to fire away.


#2 DaveGherardini Oct 29, 2004 02:50 AM

Jeff, looks like your hard at it on this one. looks awsome too BTW.. I would sugest from your spec a min of 500 watts for target weight with edf's. Put alot of volts behind those edf's. without LG you wont need more than 400 watts for a fairly wide envelope, just my 2 cents. ..Dave G

#3 northropn9m Oct 29, 2004 08:14 AM

Ho 229 Build

Thanks so much for your input. Part of the testing program is attempting to understand how much voltage and thrust is required to fly. My 70" Northrop N9M weighing in at 3.1 lbs flies great on two Speed 400's, standard Zagi props and one 9.6 v 2400 mAh NiCad battery pack. The battery pack weighs almost 12 oz and it needs that weight in the nose to get the CG correct. I get about a little over a pound of thrust with this set up. The wing is optimized for efficency, low drag and high lift. Just throwing the wing with no power on results in glides of 75 to 150 yards depending on hard the wing is thrown and wind conditions.

You can see the video of the N9M flying at:



We'll start with throwing the wing into the wind to see how it glides and then we'll add power.

Thanks so much for comments.


#4 DaveGherardini Oct 29, 2004 12:11 PM

2 to 3 more cells
For can 400 motors i found that 2 or 3 more cells is needed when turning a fan to give simular thrust as props. Thats what i meant, Nothing to do with airframe. just fan thrust is way diff from props. i would think that a min 10 cells to get simular thrust to 8 cells turning props. But it would depend on the min climb rate you would be happy with. . ..dave

#5 northropn9m Oct 29, 2004 12:20 PM

Ho 229

Thanks so much for the advice. I was thinking I would need around 12 volts. That should give me around 11 oz of static thrust per fan. 9.6 volts is advertised at 9.8 oz static.

We'll see what I really get inside of the duct.

Thanks again. I appreciate your feedback.


#6 EngineerW Oct 29, 2004 01:43 PM

If your AUW is 3.5 lbs then you will need a minimum of .5 to 1 thrust to weight ratio (just a wild guess) to fly effectively which means you will need 1.75 pounds or 28oz of thrust total or 14 ounces from each fan. The GWS 75 5 blade with a speed 400 motor will get you around 9 ounces. You can of course pump more power into the fan but you risk cratering it. I would suggest asking the EDF forum how much power in watts you can safely push that fan with. You may have to go to a weomtec mini fan and a brushless motor to get the thrust levels you seek. Anyway, I am loving what you're doing keep it up!


#7 DaveGherardini Oct 29, 2004 07:23 PM

The 75's will handle 10 cells ok. Ive run one on a 36" wing with 10 500 nicads. performance was 2/3rd's of 5x5 prop on 8 cells with 6vdc can motor. i was very disapointed needles to say. that plane was around 20oz. I still think its going to come out lighter that your projected weight though. wich is always good unless excess balast needed to balance. But you can just keep adding a cell until your balanced and stay out of wot if your pulling to many amps. I think youll be fine. btw, i found a Air Classic's(magazine) at my dads the other day(11/01) with a write up on Northrops Avion. i never new about this plane. A flying wing with 2 tail booms and elevator just in case. Very cool.

#8 EngineerW Oct 29, 2004 08:23 PM

The questions is how much thrust can you get from the 75's given 10 cells. at 1.5 volts you get 15 volts so to get 100 watts/lb you need 300 watts you'll be drawing 20 Amps so you would need 10 amps/side so....at that rating the 75's produce around 8 oz static thrust so if you discount duct losses you would get around 1lb static thrust which would give you a TTW ratio of .3 to 1. Is that enough to fly the Horten??

I honestly don't know.

What does everyone think???

#9 northropn9m Oct 29, 2004 11:02 PM

Ho 229
Thanks for all the feedback on the fans. Much appreciated.


#10 WingMan33 Oct 30, 2004 08:45 PM

Northropn9m, No pointers but man you do nice Original work. love to read your posts and look at those projects. also Jeff Im a Hour and 1/2 from muncie Let me know if you throw away any prototypes Mike B.

#11 northropn9m Oct 30, 2004 09:08 PM

Ho 229 Build
2 Attachment(s)

If you are ever going to be in Muncie, please contact me because I'd love to have you over to the shop. There is always something on the building board, plus there are three places where we can fly within 5 minutes of my home.

I've got a 12 foot Northrop N9M we could take out for a flight.


#12 DaveGherardini Oct 30, 2004 10:16 PM

Hello Jeff, What kind of power sys is in that big dude? where was the show pic from? . , dave

#13 northropn9m Oct 30, 2004 10:30 PM

12 Foot Northrop N9M
2 Attachment(s)

It used two OS 46FX engines with custom cranks. One engine turns clockwise and the other counter clockwise. The engines are 17" in front of the trailing edge. The attached picture will give you an idea how the engine pod is mounted. The wing weighs 16 lbs and I get about 8 lbs of thrust out of both engines...way too much power....it flies easily on 1/3 throttle.

The engines are cooled using two electric ducted fans that can be turned on and off. This is a great feature to have during ground operations.

The show picture is from Toledo 2004. I hope to be at Toledo 2005 with a large Ho 229....but we gotta see how this prototype is going to perform first.


#14 DaveGherardini Oct 30, 2004 11:44 PM

very cool ship, i dont see any thing other than elevons for control surfaces. Dang i need to build one of those. Jeff, why did you choose to make a opposing turning props? just curious, im assuming your turning around 11x8's or in that area. ive built and flown several twin S400 of pusher's and puller's and never found any problem with torque. But i also regularly fly a 60 stick with a 91 for fun and i like the torque influnce with it.. I'm figureing its a scale thing but i probably wouldnt go to the trouble uless its a scale thing.. Any pics of inlet duct for edf when rtf? dave

#15 northropn9m Oct 31, 2004 07:36 AM

1 Attachment(s)

Thank you for your kind words. The airfoil and lift distribution, along with the differential set-up of the elevons eliminate the need for drag rudders. Elevons are all that is required. You can see of a flight video of the 1/2 scale prototype of this wing at: http://www.bellimelgroup.com/videos/figure_8.wmv You'll notice that it flies very smooth, even in 15 MPH winds and there is very little adverse yaw and dutch roll tendencies.

The two engines, turning in opposite directions help during the take-off roll. During the first portion of the roll when there is not enough air flowing over the wing to make the control surfaces effective, the engine torque is noticeable. The wing wants to turn to one side. In the air, engine torque is not noticeable. However, there are ways to counteract this torque on a single engine, pusher-prop wing. I learned through plenty of take-offs. So, two engines turning in opposite directions are not required. I've attached a picture of a single-engine pusher prop version.

Before building a big wing, I'd encourage any future wing driver to build a smaller version somewhere in the 60" to 80" range and get some stick time on it while they build the bigger one. Pure flying wings are unique and wing pilots need experience with orienting the wing profile in the air. I have over 200 flights on my electric Northrop N9M.

These wings attract ALOT of attention at the flying field. They are unique and no one else has one. When I fly one of my wings alone, someone will always show up because they have seen "something weird in the air" and then they want to talk to me about it. If I take it to the field and there are other pilots there, the wing becomes sort of a "noon-time show" because everyone wants to see the wing fly and then talk about it afterwards. Lots of questions. The wing is the center of attention at any field or fly in.

Thanks again for your questions.

Best regards,


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