Could a sub250 EDF park flyer be a thing?

UCDWino

New member
Hey gang,

I’ve been thinking of designing a sub250 FPV park flyer for a while now, and have been playing with a variety of ideas in Cad and can never find something that ticks all the boxes. After getting my part107 recently I noticed that there are regs especially for flight over people that include references to prop guards. (Undoubtedly for intended multicopters in sure, but the regulation isn’t specific on that point). The intent here is to make something fun that is in zero way dangerous and complies with all the regs…. So I’m wondering if a sub250 EDF might be the combo we need for “anywhere” fpv fixed wing flying.

My question to you is: is this crazy?

I’m not necessarily looking to design something that is fast… I’m more interested in safety: finger safety on launch, and the ability to belly land without striking the prop, or heaven forbid, it gets flown into someone…. Maybe an EDF is the way to go?

Would be interested in your thoughts and even recommendations
 

quorneng

Master member
A EDF sub 250g park flyer is certainly possible. I built one in light weight foam and its scale too.
13Aug17.JPG

Not FPV but at 202g there is a bit of weight to spare.
As with all EDFs the problem is flight endurance as they are power hungry.
In general flight times with a prop are likely to be 3 times as long.

I would be very cautious at recommending a plane, especially a fast flying EDF, as suitable for "flying over people" as even if it might be with in the rules you could be pretty certain if there was any sort of incident involving the public the rules would be changed.
Even 250g at 30+ mph can cause an injury.
 

UCDWino

New member
Thanks for the response. What size fan is in that model?

For the rest of it, you really hit the nail on the head…. What I’m thinking I want is something that isn’t necessarily very fast, because yes, even small things moving quickly can get someone hurt. But my feeling is that it’s not the Edf that makes the model fast, it’s the fact that edfs are normally put into jet style frames with pretty high wing loading that HAVE to fly fast right?

Could you pair an Edf with a higher aspect wing and have something that is more efficient (airframe wise) that flies slower? Yes I know that a bigger wing also works against the idea of keeping it sub 250… But maybe there is a place where all these trade offs balance out?
 

JetCrafts

Active member
Thanks for the response. What size fan is in that model?

For the rest of it, you really hit the nail on the head…. What I’m thinking I want is something that isn’t necessarily very fast, because yes, even small things moving quickly can get someone hurt. But my feeling is that it’s not the Edf that makes the model fast, it’s the fact that edfs are normally put into jet style frames with pretty high wing loading that HAVE to fly fast right?

Could you pair an Edf with a higher aspect wing and have something that is more efficient (airframe wise) that flies slower? Yes I know that a bigger wing also works against the idea of keeping it sub 250… But maybe there is a place where all these trade offs balance out?
its possible u cld do 2 things

a , build a 250 g plane and put a prop guard like a ft might mini long ez with a prop guard( by prop guard i mean basically a 4-5 inch long tube around the 4-5 inch prop)(i suggested the long ez cause it has a rear mounted prop, just another thing for safety)

b . build a dc 2s edf rc plane (that,ll definitely be sub 250g)

c spend wayyyy too much time building a realy light weight frame for an internally mounted 4 or 5 inch prop or an edf(issue with edf is low flight times , which no one likes, the only upsides to them are speed , which u dont want so yah)


sry that was 3 😅
its really sweet youre doing this purely for the safety of people.
if u hv an edf then use it for somethingelse, my suggestion is just put a tube around a motor
 

UCDWino

New member
its possible u cld do 2 things

a , build a 250 g plane and put a prop guard like a ft might mini long ez with a prop guard( by prop guard i mean basically a 4-5 inch long tube around the 4-5 inch prop)(i suggested the long ez cause it has a rear mounted prop, just another thing for safety)

b . build a dc 2s edf rc plane (that,ll definitely be sub 250g)

c spend wayyyy too much time building a realy light weight frame for an internally mounted 4 or 5 inch prop or an edf(issue with edf is low flight times , which no one likes, the only upsides to them are speed , which u dont want so yah)


sry that was 3 😅
its really sweet youre doing this purely for the safety of people.
if u hv an edf then use it for somethingelse, my suggestion is just put a tube around a motor
Hmm.. I like the idea of the long EZ because that rear wing could serve as the attatchment point for the duct.

The hard thing still is landing.. I can see a guard getting ripped right off when you belly land… unless you have fixed gear…. Which might be good for slowing everything down anyway…

I guess a similar concept would be something like the bixler with an under-slung tail boom…. I don’t like the way those look…. But I’m also trying to be practical here.

And regards to my interest in safety… I think it’s in all of our best interest because it always the dummies who do something irresponsible who get our sport in trouble… right? Better to make something that is just inherently safe. I was testing out a mavic at my local park and had little kids chasing it as I was coming in to land…. Making something that can fly safely outside a RC club field needs to just be inherently safe.
 

Mr Man

Elite member
Hmm.. I like the idea of the long EZ because that rear wing could serve as the attatchment point for the duct.

The hard thing still is landing.. I can see a guard getting ripped right off when you belly land… unless you have fixed gear…. Which might be good for slowing everything down anyway…

I guess a similar concept would be something like the bixler with an under-slung tail boom…. I don’t like the way those look…. But I’m also trying to be practical here.

And regards to my interest in safety… I think it’s in all of our best interest because it always the dummies who do something irresponsible who get our sport in trouble… right? Better to make something that is just inherently safe. I was testing out a mavic at my local park and had little kids chasing it as I was coming in to land…. Making something that can fly safely outside a RC club field needs to just be inherently safe.
If you are interested in something like the Bixler (snickers) you could try the explorer.
 

Piotrsko

Master member
Hmm same issue with kids that I have with dogs at ElRancho park in Reno. Bowser runs up and chomps the plane to pieces, and the rangers get in my face for allowing it to happen and the dog owner acts all indignant. Dont fly there anymore is how I solve the issue.
 

L Edge

Master member
Hmm same issue with kids that I have with dogs at ElRancho park in Reno. Bowser runs up and chomps the plane to pieces, and the rangers get in my face for allowing it to happen and the dog owner acts all indignant. Dont fly there anymore is how I solve the issue.

Got one better. Go to public park with 11lb heli and flying. Man with unleashed dog comes to park and dog goes berserk every time I try to land. Think of the mess if he attacks heli and it makes the local paper. Guy still tries to get the dog leashed. Know my fuel will go out in about 2 minutes. Finally resolved the issue by going high, hit auto and lined up to land silently far side of park before dog knew where it was.
Score: Pilot 1, dog good. Your last sentence applies.
 

quorneng

Master member
UCDWino
It is a light weight AEO 40mm EDF that is rated for only a 2s. Its bell mouth was cut off before it was mounted in the fuselage..
AEO40mm.jpg

It generates about 200g thrust at full power so with a 202g all up weight it has a reasonable performance.
Built entirely from 2mm Depron the airframe is very light.
 

Mr Man

Elite member
UCDWino
It is a light weight AEO 40mm EDF that is rated for only a 2s. Its bell mouth was cut off before it was mounted in the fuselage..
View attachment 247060
It generates about 200g thrust at full power so with a 202g all up weight it has a reasonable performance.
Built entirely from 2mm Depron the airframe is very light.
Where did you get plans for it? Or none?
 

quorneng

Master member
It was scratch built from this 3 view from the internet.
3view.gif

It was tidied up a bit and printed to the correct size.
3viewDuct.jpg

From this a set of fuselage formers as well as the root and tip wing rib were created. All the rest was made up as I went along!
A bit of a labour of love and certainly not quick.
The Venom had permanent tip tanks but they could be jettisoned in an emergency. I managed to find a picture of one flying without them so mine is scale!
FB1no tanks.jpg

I understand the endurance on just the internal wing tanks was strictly limited.
.
 

UCDWino

New member
So... here is what Im thinking so far... just a component layout and starting sketches

Bullet shaped fuselage with the EDF in the back and the inlets for it being formed from the fairing of the back half of the component bay up front... squeeze the exhaust to a square outlet probably with a 3D printet part that also supports the V tail.

I had considered having just one inlet for the EDF on the top, so that if you belly land you arent sucking things into the lower port... It has to be a sharper angle if you do that, or I could stretch the fuse longer.. but at this point I dont know much about how close im going to be to the weight budget.

Servos for the tail up front passing the edf using pushrods, probaby on the outside of the craft. i picked a 40mm EDF based on the above. wingspan is currently 600mm.

All of this is just based on some dimensions of what people HAVE gotten away with doing as 250 gram builds like the nano goblin along with a little bit of "what i think looks good"... your critiques / ideas are very welcome
 

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L Edge

Master member
So... here is what Im thinking so far... just a component layout and starting sketches

Bullet shaped fuselage with the EDF in the back and the inlets for it being formed from the fairing of the back half of the component bay up front... squeeze the exhaust to a square outlet probably with a 3D printet part that also supports the V tail.

I had considered having just one inlet for the EDF on the top, so that if you belly land you arent sucking things into the lower port... It has to be a sharper angle if you do that, or I could stretch the fuse longer.. but at this point I dont know much about how close im going to be to the weight budget.

Servos for the tail up front passing the edf using pushrods, probaby on the outside of the craft. i picked a 40mm EDF based on the above. wingspan is currently 600mm.

All of this is just based on some dimensions of what people HAVE gotten away with doing as 250 gram builds like the nano goblin along with a little bit of "what i think looks good"... your critiques / ideas are very welcome

From the aspect of using a EDF, the inlet and outlet designs are the main factors for the max thrust. Simply put, it should be a smooth transition from one shape to another. Like your exhaust, you want to go from circular to a square outlet in that short distance?
(my F-117 had that problem to solve)

What is the weight of your battery, escape, receiver, EDF, and 4 servos?
FPV equipment is ?grams
 

telnar1236

Elite member
As others have said, it's definitely possible to build a small EDF, but it's probably not very suitable for FPV flying, especially over people. While EDFs can be built to fly slow, as a whole EDFs are more efficient and fly better when going faster. Best bet is not flying over people as others have mentioned.
 

telnar1236

Elite member
So... here is what Im thinking so far... just a component layout and starting sketches

Bullet shaped fuselage with the EDF in the back and the inlets for it being formed from the fairing of the back half of the component bay up front... squeeze the exhaust to a square outlet probably with a 3D printet part that also supports the V tail.

I had considered having just one inlet for the EDF on the top, so that if you belly land you arent sucking things into the lower port... It has to be a sharper angle if you do that, or I could stretch the fuse longer.. but at this point I dont know much about how close im going to be to the weight budget.

Servos for the tail up front passing the edf using pushrods, probaby on the outside of the craft. i picked a 40mm EDF based on the above. wingspan is currently 600mm.

All of this is just based on some dimensions of what people HAVE gotten away with doing as 250 gram builds like the nano goblin along with a little bit of "what i think looks good"... your critiques / ideas are very welcome
Looks good. I think you'll have trouble with CG with the wing that far forwards, but should be an easy fix. I suspect with those proportions you'll also have quite the high wing loading, so you may need to make it a bit bigger. What construction method are you considering?
 

UCDWino

New member
I definitely agree it’s best not to fly over people… I’m just looking at the regs and what the most strict interpretation of them could mean. Flying in a local park is going to be interpreted as “flying over people” at some point…. There is another part of the ordinance which has something to do with the potential impact force…

In any case, engineering is always a set of trade offs…. One thing I haven’t mentioned yet is that I want this to be a catapult launched FPV racer. So you can sit down, get under your goggles with a buddy doing the same (and a third friend spotting of course) and then have that third friend launch you both simultaneously. That way you can do real racing without having to try to try to sync up while already in flight.

(Having an EDF makes the catapult a LOT simpler)

The obvious (to me) place to do that is to do pylon racing at high school football fields…. Which are, again, not FRIA type fields…. Racing around designated trees at local parks is also likely… so hence the attempt to really try to nail the “design to satisfy all legal safety requirements”. Sub-250, enclosed props etc.

Regarding your question telnar, I’m think of a combination of water jet cut carbon plates for the fuse, carbon rods for spars and undecided for the wings. 3d printed peices for adapter blocks and to mount the camera and motor… It will be good dollar store old foam board to start with to be sure, but I had a gas-powered RC trainer when I was in high school 30 years ago…(ouch) that was made from Coroplast that was super durable… I’d love to return to that again someday… but there are design limitations with it…. So unknown for now.
 

UCDWino

New member
From the aspect of using a EDF, the inlet and outlet designs are the main factors for the max thrust. Simply put, it should be a smooth transition from one shape to another. Like your exhaust, you want to go from circular to a square outlet in that short distance?
(my F-117 had that problem to solve)

What is the weight of your battery, escape, receiver, EDF, and 4 servos?
FPV equipment is ?grams
The DJI o3 system is under 40 grams. That plus the 40mm fan, 4 servos, a flight controller and a receiver all sum up to 122g leaving 127 grams for the frame plus battery…. My thought is to try to design as efficient of a frame as possible and then pick a battery with the remaining weight budget…. Don’t know how that will turn out though…. Not until I try it at least.

It won’t be the end of the world to be a little over the weight at first and try to optimize…. I read The new 04 DJI unit is apparently going to have a “lite” variant which should bring the weight down even further… so while I don’t think this is going to be “easy”. I think it is probably “do-able”
 

UCDWino

New member
Related but seperate question for you guys.... I went to research how to design a thrust tube for the motor here and came across discussion saying that a thrust tube doesnt help.... Given that I have a weight limit im designing against, It might indeed nice to not to have to worry about adding a part downtstream of the EDF.... thoughts?