Modular F-104 70mm EDF Jet development and testing

[telnar1236]

More and better footage, this time from takeoff all the way through landing. I had three successful flights today and even started to try out some basic aerobatics. It's no F-22, but it's decently maneuverable. I have the flight timer set to 3 minutes and come down with about 30% left, but for the footage decided to make the flight quicker so as not to make the person videoing for me wait too long.

I'll probably create a new thread for the F-104 to upload documentation and the STLs so anyone interested in building it doesn't have to dig through this thread some time this weekend while keeping this thread to document future work on the modular system.

 

[L Edge]

More and better footage, this time from takeoff all the way through landing. I had three successful flights today and even started to try out some basic aerobatics. It's no F-22, but it's decently maneuverable. I have the flight timer set to 3 minutes and come down with about 30% left, but for the footage decided to make the flight quicker so as not to make the person videoing for me wait too long.

I'll probably create a new thread for the F-104 to upload documentation and the STLs so anyone interested in building it doesn't have to dig through this thread some time this weekend while keeping this thread to document future work on the modular system.

Congrats!!!! Your opening a new area for EDF investigation on Flitetest.

Have you any thoughts on your next modular system model?

 

[telnar1236]

Congrats!!!! Your opening a new area for EDF investigation on Flitetest.

Have you any thoughts on your next modular system model?

Thanks! That's the hope. The next plane will certainly be the modular base jet/jet trainer. It's simpler to build, will be easier to fly, and can really take more advantage of the modularity than the F-104 with swappable wings and tails of different types. I didn't quite have time to finish it in time for this weekend, but weather cooperating, I'm hoping for next weekend. Then I want to jump back over to making props work with the system. But the design there is really up in the air and I would welcome any recommendations for a prop plane. The only constraint is that the fuselage must be roughly cylindrical since the connection system relies on that. I was thinking either a Corsair or Gee Bee maybe. After that, I haven't even planned since that will probably take at least another month or two, but I do want to eventually revisit the MiG 21 I gave up on a year ago, build something with a delta like a Mirage III, and build something with vectored thrust.

 

[telnar1236]

We've had a bit of warmer weather around here and on one of the more recent flights the ESC overheated and partially shut itself down. I had about half power available, and was able to land the plane mostly safely (and I could replace the broken bits easily because it is modular) but I am holding off on releasing files and on further test flights of both the F-104 and the modular trainer jet which has the same EDF fuselage section until I have designed in and tested better cooling, probably in the form of a NACA duct.

 

[telnar1236]

The weather hasn't been cooperating with additional test flights. However, I've been doing some ground tests with the new and improved EDF fuselage using a fan to try and simulate airflow and haven't had any problems with overheating. Since the fan produces a lot less airflow than the jet flying through the air, the problem is pretty clearly solved. Writing a manual takes longer than I would have thought, but hopefully it will be ready for release soon.

Also, while I've been waiting for the weather to improve, I drew up a design for a Gee Bee.

 

[telnar1236]

A couple more pictures of the new modular planes. The Gee Bee is coming together fast.

 

[telnar1236]

Test flew the Gee Bee and the modular trainer jet today (finally).

The modular trainer jet flies great and I hope to have flight video soon. It was a bit tail heavy on its maiden flight, but nothing I can't fix by moving the battery forward. The gear which was designed to be grass capable is fine on reasonably short grass but I did cartwheel the plane trying to put it down in taller grass. As far as flight characteristics, it's relatively docile and does everything slower than the F-104.

Unfortunately, the Gee Bee has problems. It has enough power to fly and is absolutely manageable in roll and yaw although the torque is pretty noticeable (as expected). However, it has a severe phugoid oscillation problem and I was only able to fly it for a couple hundred feet before losing control and crashing. I'm going to try to shift the CG a bit further forward (though I don't know how, it already had an ounce of extra weight in the nose) but if that doesn't fix it, the design might simply not work.

Finally, the F-104 initial release is still on its way. I didn't realize how long it takes to write and prepare a good manual.

 

[FlyerInStyle]

Test flew the Gee Bee and the modular trainer jet today (finally).
View attachment 242910
The modular trainer jet flies great and I hope to have flight video soon. It was a bit tail heavy on its maiden flight, but nothing I can't fix by moving the battery forward. The gear which was designed to be grass capable is fine on reasonably short grass but I did cartwheel the plane trying to put it down in taller grass. As far as flight characteristics, it's relatively docile and does everything slower than the F-104.

Unfortunately, the Gee Bee has problems. It has enough power to fly and is absolutely manageable in roll and yaw although the torque is pretty noticeable (as expected). However, it has a severe phugoid oscillation problem and I was only able to fly it for a couple hundred feet before losing control and crashing. I'm going to try to shift the CG a bit further forward (though I don't know how, it already had an ounce of extra weight in the nose) but if that doesn't fix it, the design might simply not work.

Finally, the F-104 initial release is still on its way. I didn't realize how long it takes to write and prepare a good manual.

any files? also pla or lwpla? I really like that geebee design

 

[telnar1236]

Thanks! Everything is normal PLA to make it easy to print. Files for the F-104 and jet trainer are definitely on their way, but the Gee Bee needs to fly before I make files for it available. I'm trying extending the nose by about an inch to shift the CG forwards, but after that I'm not sure I'll continue to pursue the design. Definitely open to suggestions

 

[telnar1236]

The modular F-104 is finally released!! STLs, G-code, and a full instruction manual are now available for anyone interested in building the plane! If anyone is interested in building it and runs into any issues, please reach out.

Plane - Modular F-104 70mm EDF Jet

This is the release of my modular F-104. It is designed to be 3D printed in PLA or ABS (optional for some parts). It is a 6-channel design and flies on a 4s 4000 mAh battery up to 80 mph. This release contains full STLs, G-code, and an...

forum.flitetest.com

I'm also dedicating this thread to the F-104 from now on, since that has been its main focus, and will be moving the modular trainer and modular Gee Bee - which I am renaming to the modular racer since the changes mean it's no longer as much of a Gee Bee- to new threads.

 

[FlyingWithRyan]

Test flew the Gee Bee and the modular trainer jet today (finally).
View attachment 242910
The modular trainer jet flies great and I hope to have flight video soon. It was a bit tail heavy on its maiden flight, but nothing I can't fix by moving the battery forward. The gear which was designed to be grass capable is fine on reasonably short grass but I did cartwheel the plane trying to put it down in taller grass. As far as flight characteristics, it's relatively docile and does everything slower than the F-104.

Unfortunately, the Gee Bee has problems. It has enough power to fly and is absolutely manageable in roll and yaw although the torque is pretty noticeable (as expected). However, it has a severe phugoid oscillation problem and I was only able to fly it for a couple hundred feet before losing control and crashing. I'm going to try to shift the CG a bit further forward (though I don't know how, it already had an ounce of extra weight in the nose) but if that doesn't fix it, the design might simply not work.

Finally, the F-104 initial release is still on its way. I didn't realize how long it takes to write and prepare a good manual.

if its a bit tail heavy you might try adding a bit of wing sweep to move your CP back might make it more stable with yaw too. However it would definitely mess with stall characteristics.

 

[telnar1236]

if its a bit tail heavy you might try adding a bit of wing sweep to move your CP back might make it more stable with yaw too. However it would definitely mess with stall characteristics.

Swept wing Gee Bee! But more seriously, that would be a possibility. I think I would have 3 concerns, though, before I tried that. First, it's just way easier to make the nose longer. Modeling a tube is much simpler in CAD and also shifts the CG forward relative to the COP. Second is looks. A swept wing Gee Bee could actually look kind of cool, but would be pretty obviously not scale. And finally, I would be worried about Dutch roll. Sweeping the wings would slightly improve yaw stability but would greatly increase roll stability which could make the airplane prone to unstable oscillations when paired with the dihedral on the wings. But if the longer nose doesn't help, I'll probably try it

 

[FlyingWithRyan]

Swept wing Gee Bee! But more seriously, that would be a possibility. I think I would have 3 concerns, though, before I tried that. First, it's just way easier to make the nose longer. Modeling a tube is much simpler in CAD and also shifts the CG forward relative to the COP. Second is looks. A swept wing Gee Bee could actually look kind of cool, but would be pretty obviously not scale. And finally, I would be worried about Dutch roll. Sweeping the wings would slightly improve yaw stability but would greatly increase roll stability which could make the airplane prone to unstable oscillations when paired with the dihedral on the wings. But if the longer nose doesn't help, I'll probably try it

Oh I thought you were talking about the 104

 

[Mastershake44]

Your Gee Bee is awesome looking! It looks like it would fly well as it sits.

 

[telnar1236]

Oh I thought you were talking about the 104

Ah, I see, the F-104 balances fine, fortunately. The good thing is that the T-tail already means that stall get interesting if the CG is too far aft, so swept wings wouldn't really hurt it much. The modular trainer was a bit tail heavy, but only by a bit less than half an inch. I was able to fix that by just moving the battery forward in the tray. However, I do plan to make swept wings for it anyway. One of the overall design goals for this plane is to make it easy to experiment with different configurations like swept vs. straight wings. And since I also want to experiment with forward swept wings, I designed an adjustable battery tray to make it easy to shift the CG around wherever I want to put it. And with the aft swept wings I'll need to design a different tail with the horizontal stab below the line of the wings to avoid dangerous stalls.

 

[telnar1236]

Your Gee Bee is awesome looking! It looks like it would fly well as it sits.

Thanks, I wish it flew as good as it looks
I have the stretched nose version put back together, so I hope it gets it stable enough. It doesn't look as weird as I expected and if anything makes it a bit more proportional than the normal Gee Bee. I hope to try and fly it tomorrow

 

[telnar1236]

When I was checking things on my F-104 in preparation for flying tomorrow, I noticed that the main gear wheels were sticking. When I took them apart, I saw that as the wheels rubbed against the gear strut, they had started sucking plastic from the strut into themselves. It's a problem I ran into with my 80mm F-104 and 8 ft. wingspan cargo plane, but I was expecting it to be less of an issue with the F-104 since it's less than half the weight of those planes and takes off slower and made use of a slightly different geometry. The good news is that it's an easy fix, just adding a metal washer between the wheel and strut completely eliminates the damaging wear. I also didn't notice it with the earlier PETG gear struts at all, so it's likely the lower coefficient of friction reduces the wear experienced if the gear are printed with that plastic

 

[L Edge]

@telnar1236
and other EDF users

Thought I would like to share with you. Let's say you would like to add some thrust to your EDF without going from say 3S to 4S which adds weight.
This I have been doing for about 14 years and it's improved it for my 5 bladed EDF. You might want to try it when you get your thrust unit going. The only way I checked it out was by hold it vert, and getting it to hover. Without fix, it hovered by throttle at 54% reading on tx. With fix, it hovered at 47% throttle on tx.
So it showed an improvement static thrust and dynamic improvement when flying(I measured by 2 sticks located 200 ft apart and did time). And is so simple to do.

Guarantee:

Theory first for you. There is inside the EDF a Pstatic and a Pdynamic pressure. Everybody looks at the exhaust and reduction size.
They neglect to look at the inlet. Did you know there is leakage between blades and blades that face the outer wall? Leakage from a 5 bladed can be reduced by going to 11-12 blades setup!!! That covers the front, now the other gap.
Many EDF's have a hell of a gap between blades and the wall. Come to the aid--Magic Tape- (not cheap regular tape)
What I did is remove the ED fan
Cleaned the wall of the EDG in the range of the blades with alcohol
Lay down a layer or 2 or 3 of magic tape making sure in is flat(not skewed) Take your time and have patience.

Install fan blade back on shaft and hand spin. If still clearance, apply power to motor and spin up slowly and then check if still has clearance.

Note: Retain housing while adding power and "do not squeeze EDF housing" or you will have shorter blades.

Thrust will improve due to Pstatic increasing due to gap being smaller.

Did it especially for my A-10, SR-71 and my Dark Star.

 

[Mr Man]

Nice! Thanks for the tip!

 

[telnar1236]

@telnar1236
and other EDF users

Thought I would like to share with you. Let's say you would like to add some thrust to your EDF without going from say 3S to 4S which adds weight.
This I have been doing for about 14 years and it's improved it for my 5 bladed EDF. You might want to try it when you get your thrust unit going. The only way I checked it out was by hold it vert, and getting it to hover. Without fix, it hovered by throttle at 54% reading on tx. With fix, it hovered at 47% throttle on tx.
So it showed an improvement static thrust and dynamic improvement when flying(I measured by 2 sticks located 200 ft apart and did time). And is so simple to do.

Guarantee:

Theory first for you. There is inside the EDF a Pstatic and a Pdynamic pressure. Everybody looks at the exhaust and reduction size.
They neglect to look at the inlet. Did you know there is leakage between blades and blades that face the outer wall? Leakage from a 5 bladed can be reduced by going to 11-12 blades setup!!! That covers the front, now the other gap.
Many EDF's have a hell of a gap between blades and the wall. Come to the aid--Magic Tape- (not cheap regular tape)
What I did is remove the ED fan
Cleaned the wall of the EDG in the range of the blades with alcohol
Lay down a layer or 2 or 3 of magic tape making sure in is flat(not skewed) Take your time and have patience.

Install fan blade back on shaft and hand spin. If still clearance, apply power to motor and spin up slowly and then check if still has clearance.

Note: Retain housing while adding power and "do not squeeze EDF housing" or you will have shorter blades.

Thrust will improve due to Pstatic increasing due to gap being smaller.

Did it especially for my A-10, SR-71 and my Dark Star.

I'll have to try that, be interesting to get exact numbers on how much it improves. I'm thinking of starting a thread with performance for all the EDFs I own as a resource for other designers and maybe soliciting contributions, so that could be something to add in there too. Do you think it will be able to give an extra 20% or is it smaller, more like 5-10%?