Quiet Bird EDF

Hogwerks

New member
Hello fellow 3D printed RC plane fanatics!

I am a real bonafide certified full scale aircraft conceptual designer having worked on kit planes, vintage planes, eVTOLs, and even in the legendary "Skunk Works". My real passion in aviation is aviation history. Particularly for the vast number of designs and concepts that engineers like me have busted their butt on but ultimately never made it into the limelight. It's sad to me that so much of aircraft design history has been largely forgotten and overshadowed. Folks, I am hear to tell you first-hand that design teams in places like the "Skunk Works" do not, in fact, get a wave of inspiration and suddenly create something like the F-22 or F-35. They are the end result of sometimes decades and sometimes thousands of different aircraft designs all done to explore the art of the possible and try new things in the pursuit of a winning design.
To honor my colleagues, my industry, and the art of aircraft design I wish to use 3D printed RC plane designs to educate the public on all the hidden hard werk in aerospace, all the sacrifices, all the design triumphs, and quiet victories....aaaand give the RC community a chance to experience some really unique designs and flight experiences based on REAL concepts....okay I MAY also do some SciFi vehicles (I'm looking at you Battle Star Galactica Viper)...

All that said, let me introduce y'all to my first design in work. This has been a labor of love and is about half way through prototyping so the render shown is just an early model. I give you, the Boeing "Quiet Bird".

Quiet Bird was an early 1960s Boeing Army observation concept that explored the art of possible with stealth technology. What is so amazing about this design is it was developed around a DECADE before the infamous Skunk Works "HAVE BLUE" stealth demonstrator, the daddy of the F-117 Nighthawk. It seems the F-117 and HAVE BLUE have overshadowed this adorable and radical little airplane design. So to honor those innovative Boeing engineers and drawn to its radical yet simple look I have embarked upon this 50mm EDF 3D printed design.

I am really excited to see how this may perform. It's obvious that the inlet and EDF performance will be affected but then again, this is what aircraft design is all about: tradeoffs and compromises and trying new things!

I am eager to get feedback from the many experienced RC builders on the form and see if anyone else would be interested in this.
 

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dap35

Elite member
Are you looking to hand launch this, or will it have landing gear? EDFs without enough static thrust can be hard to hand launch. I've had a number of designs that were a PITA to launch. A couple of years ago, I converted the X32 (another fine Boeing project) from a prop-jet to an EDF. It was unlaunchable (real word??) until I removed most of the belly and shed some weight and drag.
 

Hogwerks

New member
I'm assuming hand launch will be a bit sketchy with this bird due to poor thrust. I'm exploring either a simple catapult or a dolly.
 

dap35

Elite member
I second the use of an FC. I'm a big fan of the Aura 5 especially for hand launch. If you use FrSky RX's with stabilization, then you can create a similar launch mode that works pretty well.
 

Hogwerks

New member
Interesting. Did not even think of a FC...that gets the mental gears turning....When I get a bit closer to finishing the parts I am currently modeling I'll release more images of the design.
 

dap35

Elite member
Ooh, missed the EDF size. 50mm can be small. The thrust increases dramatically with a 64 or 70mm unit. Just be cautious with weight.
 

Hogwerks

New member
HA yeah guys I am definitely warry of the weight. Don't have a specific number yet other than I know the T/W wont be stellar. But I am not looking for acro anyways. I'm looking for casual pattern scale flying. Prints are underway so a weight is close...
What kind of thrust delta do y'all see when jumping from 50 to 64 or 70? Seems like 50mm is dying out.
I have a used 70mm from an eFlite F-16 on my bench and contemplating the next iteration being a 70mm with retracts. I settled on 50mm for cost and speed since I already had all of it handy and to find out how the rest of the airplane behaves...better to crash a little 30-36" span bird.

The inlet will be a big challenge which would have been the case with the real one. Many times airplanes like this were explored to identify technical risks and push the boundaries of state-of-the-art...which is a nice way of saying 50% of me says this wont work and 50% of says it will.

The Boeing official released drawings indicate there was a slot for something to do with the boundary layer at a tricky spot off the inlet. So I am adding ESC cooling intake and exhaust to, I think, replicate that intake feature and also function as a hidden "cheater" inlet for the fan. The ESC cooling will vent straight into the EDF inlet.

So okay I will keep a 70mm on the table...plus this with retracts would be super sweet...
 

dap35

Elite member
Because the swept area of the edf fan grows by the square of the radius, a small change in diameter helps a lot.

I did a quick look on rc-castle.com because they list specs:

50mm 4s : thrust 850gm / weight 74gm
64mm 4s : thrust 1100gm / weight 137gm
70mm 4s : thrust 1600gm / weight 185gm
The other challenge can be flight time (battery capacity). You will use a larger battery with an EDF than you would with a prop. I have a 70mm/4s Viggen. I started with a 2200mah battery, but then added a second in parallel (so effectively using a 4400maH ). Doing so also helpd with the low battery alerts everytime I throttled up.
 

Hogwerks

New member
Thanks for the thrust info dap!
Some more screen shots of things in work.
The wing printing is well underway. Tails are que'd up. Fuselage detail design is close (only showing what is done here). Have a few odds and ends to model yet like servo mounts.
What do y'all recommend for a catapult hook? I want to keep the exterior as clean as I ca stand especially in profile. I will be adding some bumpers under the wing to protect servo arms so another on centerline for the cat hook up is not the end of the world...but I am interested in more 'hidden' options.
Also curious if anyone else here has had this annoying problem with importing STEP files into PrusaSlicer. The wing root fillet gets broken up bad. Its just a circular fillet so I don't fully understand how that is not compatible with the STEP processing kernel in the slicer. I can do a simple side step of the problem: just do high res STLs and that's that. But I would like to understand if I should change something about how generate the original loft of the airplane.
 

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Hogwerks

New member
Airframe is all printed and assembled
Next the fun part, hooking up stuff!
Can't wait to hear this thing. With all the nasty flow the EDF should let out a horrendous shriek.
See if you can find the cooling/cheater air in/out!
 

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quorneng

Master member
Printing is not the lightest way of building an EDF but your design does look nice - except for those inlets!
A sunken inlet like that will effectively reduce both the static thrust and any dynamic pressure created by forward motion.
Many seem to think that a conventional inlet sticking out in the air flow creates drag. What you have to remember is that the air is being drawn into inlet at least as fast as the plane is flying so there is no aerodynamic drag. It is quite likely that at full speed the inlet air is being forced into the inlet so creating a bit of dynamic pressure which will raise the inlet pressure at the fan face. Not by much but every little helps.
For normal EDFs we are not taking super sonic airflow speed where the problems are of a completely different order.
To my mind cheat holes are just as aerodynamically bad. If required to achieve the required level of performance it signifies a poor inlet duct design.
I am not sure 50mm EDF are going out.
A scale Hawker Hunter with a 50mm QX 7 blade EDF and it only needs a 1500mAh 3s.
Complete2.JPG

A foam airframe although the whole duct is printed. The inlets are scale and there are no cheat holes.
Easy hand launch and belly land on grass.
The duct is made up of 8 single wall PLA pieces glued together. Unusually the fuselage is built up around the duct using 5mm XPS sheet.
FirstPlanks.JPG

The cockpit and nose is built as a separate unit and glued on once the fuselage is complete.
It flies pretty well. Certainly not rocket fast (scale speed?) but pretty manoeuvrable so able to keep close to the camera.
 

Hogwerks

New member
That Hunter looks good.

Yeah these inlets are the big question mark and something I am curious about. Who knows maybe those Boeing engineers back in 1962 knew something!
Perspective: this design was done a whole 15 years before the famous Skunk Works "HAVE BLUE" stealth demonstrator with literal screens over the inlets.
 

JetCrafts

Active member
Airframe is all printed and assembled
Next the fun part, hooking up stuff!
Can't wait to hear this thing. With all the nasty flow the EDF should let out a horrendous shriek.
See if you can find the cooling/cheater air in/out!
no offence but those inlets might starve the edf
 

FoamyDM

Building Fool-Flying Noob
Moderator
Did this bird ever Fly? I have been inspired to make a Foam Board version.
 

FoamyDM

Building Fool-Flying Noob
Moderator
Hello fellow 3D printed RC plane fanatics!

I am a real bonafide certified full scale aircraft conceptual designer having worked on kit planes, vintage planes, eVTOLs, and even in the legendary "Skunk Works". My real passion in aviation is aviation history. Particularly for the vast number of designs and concepts that engineers like me have busted their butt on but ultimately never made it into the limelight. It's sad to me that so much of aircraft design history has been largely forgotten and overshadowed. Folks, I am hear to tell you first-hand that design teams in places like the "Skunk Works" do not, in fact, get a wave of inspiration and suddenly create something like the F-22 or F-35. They are the end result of sometimes decades and sometimes thousands of different aircraft designs all done to explore the art of the possible and try new things in the pursuit of a winning design.
To honor my colleagues, my industry, and the art of aircraft design I wish to use 3D printed RC plane designs to educate the public on all the hidden hard werk in aerospace, all the sacrifices, all the design triumphs, and quiet victories....aaaand give the RC community a chance to experience some really unique designs and flight experiences based on REAL concepts....okay I MAY also do some SciFi vehicles (I'm looking at you Battle Star Galactica Viper)...

All that said, let me introduce y'all to my first design in work. This has been a labor of love and is about half way through prototyping so the render shown is just an early model. I give you, the Boeing "Quiet Bird".

Quiet Bird was an early 1960s Boeing Army observation concept that explored the art of possible with stealth technology. What is so amazing about this design is it was developed around a DECADE before the infamous Skunk Works "HAVE BLUE" stealth demonstrator, the daddy of the F-117 Nighthawk. It seems the F-117 and HAVE BLUE have overshadowed this adorable and radical little airplane design. So to honor those innovative Boeing engineers and drawn to its radical yet simple look I have embarked upon this 50mm EDF 3D printed design.

I am really excited to see how this may perform. It's obvious that the inlet and EDF performance will be affected but then again, this is what aircraft design is all about: tradeoffs and compromises and trying new things!

I am eager to get feedback from the many experienced RC builders on the form and see if anyone else would be interested in this.
Are you able to take that model and make a Flattened Skin File? (like it were a sheet metal part?