So, I'm trying to make a small (Simple) Early Fighter Jet kind of thing, any Tips?

[short_nathan]

Well, you may know me as the designer of the crappy Mini SR-71s, but I want to start some other designs, and the best thing I could think about making was a couple of small Korean War fighters, like the F-86 and MiG-15 (not warbirds because I can't stand looking at prop planes without props). I don't really want it to fly, I haven't flown jets yet, so I would build those planes as medium sized models, but I want it so if I want to make them RC, I don't have to do too much redesign. Any things I should know about, anyone?

 

[quorneng]

It rather depends on what you mean by small but the smaller you go weight (or rather wing loading) becomes an ever bigger issue to keep the reasonable flying characteristics.
If the plane has to go really fast to actually fly the smallest aerodynamic twist or blemish will have a dramatic effect making it hard for a human to control. The slower it needs to go to fly the more likely it will be "human controllable" and believe it or not it is more realistic as well.
Most seem keen on using the most powerful EDF they can squeeze in with a correspondingly big heavy battery. It is the thrust to weight ratio that counts and with a well thought out light weight construction it is amazing just how light is possible, particularly if you chose the right plane to model.
I note the F-86 used an axial compressor, thus small diameter, turbo jet hence a skinny fuselage. The Mig 15 used a version of the RR Nene which had a large diameter centrifugal compressor hence a fatter fuselage so more room for the EDF.

Not exactly small (40" span) but an example of light weight foam EDFs
Hawker Sea Hawk also used a RR Nene.

The fatter fuselage and straight wings allows a low power 55mm EDF.
Hawker Hunter F6 to the same scale. It used a RR Avon

The smaller diameter fuselage required a more powerful 10 blade 50mm EDF so a shorter duration using the same battery.
What size plane are you thinking of?

 

[L Edge]

My suggestion to you is to spend lots of time at RC sites such as RCGROUPS and others and review designs, building methods, tips in designing aircraft that you are interested in. You can educate yourself very quickly on what is the right direction to go. Also, watch the flight videos they produce and see what happens. To me, if they do not show the full flight, it didn't happen.

Second method, let's say you have a Freewing 12 bladed 60 EDF. Search the online stores for kinds of planes using that type EDF, and look at specs. You can glean thrust, take off weight, length, wide of wing, etc and usually get a video, so now the question is "Can a design, build, and fly something matching that criteria?" Do enough models and it should work out.

 

[short_nathan]

My suggestion to you is to spend lots of time at RC sites such as RCGROUPS and others and review designs, building methods, tips in designing aircraft that you are interested in. You can educate yourself very quickly on what is the right direction to go. Also, watch the flight videos they produce and see what happens. To me, if they do not show the full flight, it didn't happen.

Second method, let's say you have a Freewing 12 bladed 60 EDF. Search the online stores for kinds of planes using that type EDF, and look at specs. You can glean thrust, take off weight, length, wide of wing, etc and usually get a video, so now the question is "Can a design, build, and fly something matching that criteria?" Do enough models and it should work out.

Well, I have been considering a more boxy design to the jets, like the FT-22.

 

[short_nathan]

It rather depends on what you mean by small but the smaller you go weight (or rather wing loading) becomes an ever bigger issue to keep the reasonable flying characteristics.
If the plane has to go really fast to actually fly the smallest aerodynamic twist or blemish will have a dramatic effect making it hard for a human to control. The slower it needs to go to fly the more likely it will be "human controllable" and believe it or not it is more realistic as well.
Most seem keen on using the most powerful EDF they can squeeze in with a correspondingly big heavy battery. It is the thrust to weight ratio that counts and with a well thought out light weight construction it is amazing just how light is possible, particularly if you chose the right plane to model.
I note the F-86 used an axial compressor, thus small diameter, turbo jet hence a skinny fuselage. The Mig 15 used a version of the RR Nene which had a large diameter centrifugal compressor hence a fatter fuselage so more room for the EDF.

Not exactly small (40" span) but an example of light weight foam EDFs
Hawker Sea Hawk also used a RR Nene.
View attachment 247479
The fatter fuselage and straight wings allows a low power 55mm EDF.
Hawker Hunter F6 to the same scale. It used a RR Avon
View attachment 247480
The smaller diameter fuselage required a more powerful 10 blade 50mm EDF so a shorter duration using the same battery.
What size plane are you thinking of?

About a 40cm wingspan

 

[short_nathan]

Also, I messed with chatgpt a bit, and concluded that for learning to fly those swept wing jets, I should fly a straight wing fighter with only one engine. Any suggestions? Also, what could be a good EDF size?

 

[short_nathan]

Aaaaand, could one of these be my first jet, and what things should I take into consideration if I end up doing that?

 

[Brian B]

I like unusual and rare topics myself. I'd be all in with a classic jet fighter look like this XF-90. In the early days, this is what a jet looked like, even if the actual plane was a failure. It's a twin, but maybe with an outlet splitter....

Or for ultimate speed, this oddball. Argentina cruise missile from 1960. Simple and elegant as a foamboard, just add a canopy.

 

[Piotrsko]

Issue with DIY jets is calculating where the CG should be and building appropriate internal structure using a swept wing. Flies pretty much the same with no odd handling issue at stall if designed correctly. Suspect @quorneng know s all about this

 

[quorneng]

As a first EDF it will depend on what sort of RC planes you have flown and how good you are at it.
It is perfectly possible to make a prop plane that flies like an EDF so for some the first EDF is no different.
Ideally you want an EDF that will be similar to fly to what you are already used to. Avoid the temptation to build an exotic looking jet just because it has no prop! Speed makes a plane harder for a human to control and it also means that the results of any "unwanted contact with the ground" are much more serious too.

Perhaps you could tell us what planes you fly at the moment and from what sort of airfield as this will help set the boundaries of what is likely to be a suitable first ED.

My first EDF (built 13 yeas ago) was not actually an EDF but a relatively big light weight airframe with a 3" prop inside the hollow fuselage.
It certainly looked like a jet but with its light weight and generous wing area

It flew no faster than a basic trainer. I still have it.

 

[short_nathan]

Well, I have been thinking of a design that doesn't need that much speed, so it can flay as slow as possible while stilll being EDF.

 

[short_nathan]

Aaaaand I am on a tight budget, so getting it to be a prop plane would need some extra electronics. By the way, I have an FT-22 with some electronics, and I havent flown it yet, could the FT-22 help me with flying an EDF? Also, I am giong to build a simplified P-80, should that be more stable?

 

[Piotrsko]

The early turbofan jets were scabbed on a prop powered aircraft, the Brits even used a biplane (long funny story here). In theory, paying attention to the thrust lines and mounting, CG is important, but you should be able to mount an edf on anything that was prop powered. It WILL be ugly and inefficient. Key is thrust must be high enough to fly the plane.

You also know the ESC will power a motor and prop instead of a EDF?
Design is more important than what it is. Suggest making a trainer style for experiments as a shooting star has annoying quirks. Bet a slow stick would be fun edf powered.

 

[short_nathan]

The early turbofan jets were scabbed on a prop powered aircraft, the Brits even used a biplane (long funny story here). In theory, paying attention to the thrust lines and mounting, CG is important, but you should be able to mount an edf on anything that was prop powered. It WILL be ugly and inefficient. Key is thrust must be high enough to fly the plane.

You also know the ESC will power a motor and prop instead of a EDF?
Design is more important than what it is. Suggest making a trainer style for experiments as a shooting star has annoying quirks. Bet a slow stick would be fun edf powered.

Yeah, I have been trying my best to keep the design slow and stable: the wings, the boxy fuselage, the low weight and I will add the FT Aura Lite to see if it helps

 

[cyclone3350]

Have U looked at TheFopster's easy jet here on the forum's?

 

[L Edge]

@short_nathan


Actually, the F-22 is good if you aren't too heavy for an EDF. I started off simple and this is what I did.

In this case, you can put a short tube after the EDF or you can just mount the EDF with the 1/2 round hole in front of it and about 2-3 inch rectangular hole after it. Again, the secret to success is to find a design that has been designed for stress and yet lightweight.

According to the FT F-22 plans, it weighs 8.3 oz, what does your weigh?

Here's my F-22 with a thrust vectoring unit(so extra tube and weight) and it does good.

 

[short_nathan]

These are the Pre-RC plans I came up with, it turns out that the intakes are very hard to make, what could help?

 

[Mr Man]

These are the Pre-RC plans I came up with, it turns out that the intakes are very hard to make, what could help?

you could use posterboard.