Official Freewing JAS 39 Gripen 80mm EDF Jet

[Airguardian]

SURPRISE!

Maiden flight with my second Gripen done, featuring a more scale-like, custom-designed, 3D printed and gapless tv nozzle! :D
Took me a while (over 1 year) from project start to first test, but so far so good... I'll copy paste what I wrote in the video description in case you want to know more about it:

The Gripen is back!!! Or rather... a new Gripen has joined the ranks!

After struggling with my former 8S-modded Gripen from Freewing for a long time, I decided I wanted to try getting a new airframe to make a lighter 6S build with Freewing's newer motorization, which seemed to deliver a lot more thrust with a reasonable power consumption.

My former Gripen could only make 2.5 to 3min flights with the Jetfan setup, so it was not as fun to fly as other jets. With that in mind, I ordered one anew, but kept in the box.

I obviously wanted to have a TV nozzle on the new one, but I didn't feel like paying another 100€ for it, more so considering that the FW nozzle butchered the duct efficiency, so I decided to try and fix it for myself, but in the meantime, the jet was waiting... it took me about a whole year to come up with the design, model it in CAD, prototype the basic working-concept idea, then adapt it for the Gripen, which meant modeling the entire aft-fuselage section as accurately as possible and optimizing for strength and weight... then finally printing it in PETG, painting it to match the new Gripen livery and finally getting to test fly it!

I've been pretty busy with other projects, so I kept dragging my feet, but now I have finally maidened the new 'Gripen 2.0' with my custom nozzle and you can see the results for yourself in the video!

I'll give more details in future videos, but for the time being, know that my nozzle design is a much more good-looking and scale-accurate approach than Freewing's one, using recessed servo installation so they don't protrude from the fuselage skin other than for the servo arms as well as featuring my own 'gapless TV nozzle' concept, that leaves no nasty holes affecting the aerodynamics of neither the inside of the duct, nor the exterior of it. And no, I didn't copy Freewing's idea, I started working on this before they made their revised 'V2' nozzle design which so far they've shown only for the AreS. The mechanics of how mine works aren't even the same.

My nozzle intentionally adds a lot of weight, to fix the inherent nose-heaviness nightmare of the model's design. On the current setup, I can manage to fly with a pretty neutral CG of 40mm aft of the wing marks with a 680g 6Ah 6S Lipo pushed all the way back without carving foam, but having removed the nose gear light, the lighting controller and the pilot figure. Still, this meant having the whole piece weigh about 340g.
I'm considering shaving some extra weight from it, but that would require reversing the nose landing gear position to be able to fly such a large pack at that CG, so I'm pondering whether it's worth the effort...

So far this new nozzle has survived 11 flights and over 7Gs repeatedly, so it's looking good!

At the moment I intend to test and debug potential problems with the current nozzle design, and if it survives my scrutiny and flying antiques, I will likely sell it. I still haven't decided whether I'll sell whole nozzles as add-ons or just the 3D printing files, we'll see. Feel free to speak your mind about it in the comments section!


These were flights 1st to 5th on 'Freja'.

Pilot: RC4ever
Ground video: Luis Ibáñez
Airfield: Club Pla de Vent
Music by Linkin Park (Check video chapters)

SPECS (Reflecting my setup):

Model Scale: 1/9th
Wingspan: 882mm
Length: 1613mm
Weight: 2300g (w/o batteries - aprox)
TOW: 3300g (aprox)
CG: 40mm-45mm aft of factory recommended position (molded into the wings)
Material: EPO
Motor: Freewing 3658-2150Kv Brushless Inrunner
EDF: Freewing 12-blade 80mm EDF
ESC: Freewing 100A w/ 5A UBEC
Servos: All stock except the TV nozzle, which is driven by a couple of PTK 9497MG-Ds
Landing Gear: Electronic retractable w/ aluminum trailing link struts
Receiver: Jeti Rex12A (user choice)
Gyro: Jeti Assist - Receiver integrated
Main battery pack:
HRB 6S 4000mAh
CNHL 6S 4500mAh LiHV
CNHL 6S 6000mAh LiHV

The jet is powered with the stock Freewing 6S 80mm 12 blade EDF with. This time, I didn't cover the cheater hole with a mosquito net to improve static thrust numbers, but I'll be sticking to paved runways to protect the fan. This setup is much less power hungry than my former 8S Jetfan setup, allowing me to fly 4 - 4.5min on 4Ah 6S packs, compared to the terrible 2.5 - 3min from the Jetfan setup. My current batteries aren't the most powerful out there, so I can likely still improve thrust, but I'm almost hovering the jet already, so it's an improvement all the same!

More setup details hopefully coming soon, when I finish fine tuning everything!

[Airguardian]

Yep, that was a fun one...

TL:DR, remember to physically check the force of the servos once installed, adding a bit of manual resistance to movement (without breaking anything ofc) to see that the servos are actually working as intended and not getting stuck. :p

[Chillibadger]

Nice!
...this reminds me I still need to finish assembling my custom, lossless, 3DP nozzle and test it on the Gripen too.

I watched your autopsy video about your Gripen and the crashes. It's ashame the nozzle caused those issues but does show you need to check the unobvious stuff that doesn't look broken too

[Airguardian]

Nice!
...this reminds me I still need to finish assembling my custom, lossless, 3DP nozzle and test it on the Gripen too.

[Chillibadger]

Yep, that's me. The RC4ever username was taken here I think, so... 🥲

I see nothing wrong with trying both setups. I still think no roll is better for this sort of airplane configuration, but you do you.

Mind that if you use stabilization on the canards too, and deactivate the roll mix, then the gyro will make the canards fight your inputs in the deactivated axis. Not good! ...There are workarounds, but it requires more programming, usually managed by using logical switches and dual gyro modes, if available.

I shall keep it simple, A3S4 is on order. Appears my TV is delayed motionrc end due to backorders but probably have 5 weeks waiting for the aircraft anyway.

[Airguardian]

So canards are just for pitch, does that work best as I see motion setup both? I'm also going to add TV. Are you RC4Ever on youtube?

Yep, that's me. The RC4ever username was taken here I think, so... 🥲

I see nothing wrong with trying both setups. I still think no roll is better for this sort of airplane configuration, but you do you.

Mind that if you use stabilization on the canards too, and deactivate the roll mix, then the gyro will make the canards fight your inputs in the deactivated axis. Not good! ...There are workarounds, but it requires more programming, usually managed by using logical switches and dual gyro modes, if available.

[Evan D]

I use 11 on mine but no gyro in them. I put steering on a separate channel.

[Chillibadger]

Stock works, go from there if you want.

thank you. I've ordered a SuperP noting that I need at least 9 channels. 10 if using thrust reverse and 12 if using gyro with gain.

Ail
Ele
Throttle
Rudder
Gear
Canard L
Canard R
Vector Ele
Vector Rudder

Reverse Thrust
Gyro
Gain

[Evan D]

Stock works, go from there if you want.

[Chillibadger]

Try it both ways, canards for both and then canards for just pitch. On my Gripens I have both as I prefer the way it flies with both.

thanks will give it a go. will put the aileron mix on a switch but leave the elevator mix permanent. Do you think the rates on the canards are ok matched to elevator movement or do I need to reduce it down a little?

[Evan D]

Try it both ways, canards for both and then canards for just pitch. On my Gripens I have both as I prefer the way it flies with both.

So canards are just for pitch, does that work best as I see motion setup both? I'm also going to add TV. Are you RC4Ever on youtube?

[Chillibadger]

A3Mini and A3S4 are my picks as far as HE gyros go. I wouldn't use the canards in roll, just pitch, like the full scale one does. You could add a second gyro to control the canards at a higher gyro gain for optimal performance. Not required, but nice to have.

So canards are just for pitch, does that work best as I see motion setup both? I'm also going to add TV. Are you RC4Ever on youtube?

[Airguardian]

A3Mini and A3S4 are my picks as far as HE gyros go. I wouldn't use the canards in roll, just pitch, like the full scale one does. You could add a second gyro to control the canards at a higher gyro gain for optimal performance. Not required, but nice to have.

[Chillibadger]

Got mine on order, what's the best Hobbyeagle gyro to use? Assuming I will set it to delta and use CH1 and CH2 only plus rudder. Canards won't be plugged into the gyro and I will have to mix those to work with pitch and roll? I'm not a spektrum user.

[Sherman889]

As I said absolutely it's safe.

Thank you

[Evan D]

As I said absolutely it's safe.

[Sherman889]

You'll have the same answers here as at RCG.

Are you saying the canards do not move with stick movement or that they are not being moves by the gyro stabilization? Probably safe either way. If you just don't have gyro movement, absolutely it's safe.

the canards move with the stick in both roll and pitch but do not move under gyro control-the elevons function properly when testing the gyro.

[Evan D]

You'll have the same answers here as at RCG.

Are you saying the canards do not move with stick movement or that they are not being moves by the gyro stabilization? Probably safe either way. If you just don't have gyro movement, absolutely it's safe.

I have a freezing J39 Gripen with a AR8360T and in gyro mode with as3x active only the elevens respond—no canard movement—is it safe to fly it this way?

[Sherman889]

I have a freezing J39 Gripen with a AR8360T and in gyro mode with as3x active only the elevens respond—no canard movement—is it safe to fly it this way?

[Evan D]

Duplicate??