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Nov 04, 2019, 06:21 PM
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Dantiel's Avatar
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Discussion

2xEDF flying wing


Hey foam guys,
i am planning a scratch build EDF foam flying wing jet with 2x 30mm EDF turbines, and about 60cm wingspan. A bit similar to HortenHo229, but different: less flat, lower aspect ratio and turbines more separate.

Its gonna be my first foamie and just noticed how easy it is to break EDF blades when i turned the motor on with 3S lipo it immediately breaks them.

But my question is wether it makes sense to independently control both turbines for steering? or should i rather control both in same channel? for the latter i'd probably use arduino and ppm receiver than normal 3ch pwm ? are there examples for how this control performs?
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Nov 04, 2019, 07:20 PM
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rajazo's Avatar
I have doubt about differential thrust on EDF, these turbines are great for speed but donít have much thrust, then reaction could be to slow.
How to make this configuration? It depends of your radio, goggles differential thrust and you get lot of options. For me the best configuration is using a Aux channel than copy the throttle channel , and then use the rudder channel mixed with throttle (engine 1) and aux (engine 2) .

Whatever option you choose to config differential thrust, remove the propellers before programming or you can suffer serious accident or damage
Nov 05, 2019, 04:27 AM
Registered User
60 cm wing span?

That's pretty small. Small airplanes built with "typical" materials usually have to be flown fast to stay airborne (easier to achieve low wing loading at larger scale).
EDF units have low thrust at low speed, so hand launching will be challenging.
Having said all that, it is achievable and I've seen some examples on this site - do a search for some tips.
Nov 05, 2019, 06:22 AM
Registered User

My experience


To answer your question.
I have a P38 with differential thrust, ailerons and elevator. Had it setup with AERT before aaaand there is no real difference.
If you just want stable flight with low weight I would go with Elevons and Throttle. 3 Ch.
You could also substitute the elevons for elevator and realized roll over diff. thrust. But that needs more mixing and more hardware.
I also think you could make this easier on yourself by building a larger plane.
(Short calculation: 0.6^2=0.36 / 0.8^2=0.64
So by going from 60 to 80cm wing span you reduce wingloading to just over the half. Slower plane=less catastrophic crashes.)
Last edited by JustAHuman; Nov 05, 2019 at 06:29 AM.
Nov 05, 2019, 09:33 AM
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Dantiel's Avatar
Thread OP
thanks for all your detailed answers and tips. @rajazo, nuteman and JustAHuman

I am trying to make this a scale plane because i am a fan of the tv series and the character. Hence for 80cm wingspan id have to use like 40mm edf? Or also just add more padding around it.. I attach image of the sketch. Currently i am trying to figure out how i am actually gonna build it with depporn 3mm and 5mm. Probably making a simple skeleton with ribs for fuselage and turbines and attach wings separate to carbonspars.

Based on your suggestions I will try to make the bigger airfoil and more the light as possible. I checked the sketch and its even got to be a bit narrower: 540mm..

When EDF is worse at slow speed does it mean it won't be able to hover?

currently my transmitter doesn't support mixing, that's why ill use arduino to make the mixing. I sopose the eventual weight is gonna be around 120-150g, and thrust of one EDF unit @7.4V is about ~100g? it is curious also because there isn't gonna be a rudder like elevons, only elevator and ailerons, which i am gonna put probably on the rudder control. And then use the differential throttle stick for making curves? Downside of the approach is that airlerons are then gonna be used only asymmetrical because elevator is elevator, but that should be OK stable? I have not too much experience with these

Also i am thinking of making it possible to attach optional landing gear for cement or for water.

EDIT: what about placement of EDF i see typically theirs placed at the end, is there a reason like less turbulent incoming airstream?
Last edited by Dantiel; Nov 05, 2019 at 09:38 AM.
Nov 05, 2019, 10:24 AM
Registered User

More thoughts


I would just "add" more padding, or even better just build the tunnels to the needed size. Bigger EDFs just make your model heavier again. Also, if you want, go for the 60mm wing span. All I wanted to say is, that in my experience bigger is easier to build and nicer to fly (until the model dings on every doorframe...)
I would go for a 80cm built with mostly 3mm depron.
Your control issues are funny. I thought about controlling a flying wing with just aileron and elevator control without mixing by just holding the TX diagonal back in the days as well... but lets be real.
We are building models. We invest time and money.
You will want a Radio that mixes and such at some time, so why not now. Alternativly you could get a V-tail Mixer. Small piece of Hardware for maybe 4 bucks. I think you will really want Elevons for this.
Cool motivation by the way. Looks like Toriyama just drew a Cartoon Horten GO.
I am making a Mosquito right now, also inspired by a Comic.
Nov 05, 2019, 11:25 AM
Registered User
Quote:
Originally Posted by Dantiel
When EDF is worse at slow speed does it mean it won't be able to hover?
Depends on your definition of "hover".
If you mean literally zero forward motion, almost certainly not.
If you mean very little forward motion, then that will depend on wing loading and how good a pilot you are (or how good a flight controller you've installed/configured)
Nov 08, 2019, 02:51 PM
Electric Coolhunter
Thomas B's Avatar
A better approach is to put the EDF units right at the inlets. This will help you reach a flyable CG without having to add weight at the front.

Right now, you have the fans behind where the CG will need to be located.

With a decent rounded inlet lip and a nice thrust tube behind the fana, you will get decent performance.
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Nov 08, 2019, 03:38 PM
Registered User
I have a similar project - not exactly a Horten but close.

I'm using 1" thick insulation foamboard from Homedepot and shaving it down rather than using depron. It can then be covered with a thin layer of carpenters glue for ridgidity. I'd even recommend layered dollar tree foam and shave that down over Depron just based on cost (and I've yet to find Depron)

60cm is only 24 inches, so you may even be slightly UNDER POWERED with 30mm fans. keep the weight as low as you can.

But mine is a 2x 70mm 6S monster


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