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Official Freewing JAS 39 Gripen 80mm EDF Jet

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  • Very cool!

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    • That 90mm conversion looks cool be interesting to hear how it performs.
      I agree with Airguardian ducting / airflow seem to be one of the challenges with this truly awesome model. Yes it has quirks but honestly I have modded every jet I own for one reason or another. I with a few tweaks have it running with an enjoyable performance envelope. Cheers to all out there that are JAS39 Gripen pilots. It is a great jet!

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      • 3DP VT nozzle.

        Click image for larger version

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        • Awesome!!!

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          • Originally posted by TangoVector View Post
            Progress report on my FMS 90mm conversion.

            I'm going for a taper to approx 98% of Fan Swept Area at the rear for good static thrust, top speed isn't a priority. I have printed rings to give the tube correct size and shape. The tube in two parts is made of thick paper and will be lined with aircraft-grade extremely thin alu-tape for strength and some type of afterburner simulation, probably kallend s DIY version. Taper goes from 92mm to 81mm at the end, so a F-16 tail cone is on the way (yes I know, but it is close enough for me at this stage).I have opened up the cheater hole and will also add the F-16 side inlets on top as Mtpisgah99 suggested.

            A lot of foam has been removed and the tail carbon-rods are too narrow, but I will put in other reinforcements. I'm trying to get airflow as smooth as possible on both sides of the fan so I'm planning to print a more aerodynamic cover for the carbon spar in front of the fan.

            This is fun!
            what i did on my 90mm conversion, i added a clean 80mm duct fan inside between the two joint of main body and nozzle part to have strength and transition. however, it added too much tail weigh. i have to use bigger batt. 6k ma. minimum to get CG by the book. it got out of proportion everywhere but its fast and furious.

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            • Originally posted by Mtpisgah99 View Post

              what i did on my 90mm conversion, i added a clean 80mm duct fan inside between the two joint of main body and nozzle part to have strength and transition. however, it added too much tail weigh. i have to use bigger batt. 6k ma. minimum to get CG by the book. it got out of proportion everywhere but its fast and furious.
              any pic's

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              • Originally posted by Mtpisgah99 View Post
                i have to use bigger batt. 6k ma. minimum to get CG by the book. it got out of proportion everywhere but its fast and furious.
                Don't be too eager to get CG by the book. Factory recommended CG sucks big time. The jet can deal with much aft-shifted CGs and will fly better.

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                • Originally posted by Airguardian View Post

                  Don't be too eager to get CG by the book. Factory recommended CG sucks big time. The jet can deal with much aft-shifted CGs and will fly better.
                  i'm just too eager to find the neutral point .

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                  • Not sure if the search is broken but it ain't working for me... yes I'm logged in. Anyway, if this hasn't been posted before:
                    To Freewing/Alpha, Just some friendly feedback. FW should include the magnets on the doors for the Gripen. They are thin, non standard and difficult to source. They can't be that much. Turned a 5 min job into 30 from digging off the old ones. Dunno what would happen if I lost them.
                    https://www.motionrc.com/products/fr...main-gear-door
                    Thanks.

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                    • I don't know how often the main door pins break off but I've heard of it a couple of times. It happened on my maiden, on (or before) retraction after take-off. No, they did not hit anything. I will say the winds were 10-15 mph, but still...For those that have had this, is it just the front pins that break? If so, my theory is that the pins are pulled back while doors are out, exerting more stress on them through leverage. So I tack glued a small piece on plastic (between the back of the pin and the pocket) to keep the pins fully inserted. The jury is still out but after 4 more flights, no problems.

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                      • I've broken the front pin on the right main gear door twice on mine. I'm pretty sure it was due to a less than soft landing each time, but yes the front one is always the one that breaks.

                        If the doors weren't so inexpensive, I'd just drill a hole and replace the plastic pin, which breaks too easily with either carbon fiber rod or wood.

                        I don't think the gear could overcome magnets on the doors without stalling, but there might be a middle ground. I have trouble getting mine to close fully even with the retracts nice and tight; I'd hate even more if I couldn't get them to open as then damage would be assured.

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                        • Originally posted by Mizer67 View Post
                          I don't think the gear could overcome magnets on the doors without stalling, but there might be a middle ground. I have trouble getting mine to close fully even with the retracts nice and tight; I'd hate even more if I couldn't get them to open as then damage would be assured.
                          The stock doors feature magnets. ;)

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                          • Originally posted by Airguardian View Post

                            The stock doors feature magnets. ;)
                            Didn't realize that....thought it was just the latch mechanism holding them shut in flight

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                            • I have been flying mine on an FMS fan on 7s from the start with additional dorsal cheater vents. I thought I would try 6s and tape over the extra cheaters to see what the difference was, but decided there was no point to going backwards to a lower power system. I only got a few flights in before the flying weather got terrible, but used the downtime to repaint to a high visibility scheme and print stuff to hang on the wings. The waste heat fro the 3d printer helped to heat the house.

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                              • Hi guys - I'm flying turbine models but this edf is just SUPER !!!
                                Attached Files

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                                • Solved - Gear Doors Stay Open in Flight, Added Servos

                                  I found the problem to be air pressure in flight stalling retracts before fully closed, started after about 10 flights. I removed all the mechanical door links, springs, push rods, etc. and replaced them with added servos and links from EF2000 Eurofighter gear doors and a sequencer just for the servos to get max throw and added a 5 second down delay to the gear channel in the TX to allow the main doors to fully open. Now that the doors close reliably, my Gripen flights are back to normal fun and much better. See pics.
                                  Attached Files

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                                  • Originally posted by Mizer67 View Post
                                    If the doors weren't so inexpensive, I'd just drill a hole and replace the plastic pin, which breaks too easily with either carbon fiber rod or wood.
                                    I've done that to mine. CF pin.

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                                    • Originally posted by RCMC View Post
                                      Solved - Gear Doors Stay Open in Flight, Added Servos

                                      I found the problem to be air pressure in flight stalling retracts before fully closed, started after about 10 flights. I removed all the mechanical door links, springs, push rods, etc. and replaced them with added servos and links from EF2000 Eurofighter gear doors and a sequencer just for the servos to get max throw and added a 5 second down delay to the gear channel in the TX to allow the main doors to fully open. Now that the doors close reliably, my Gripen flights are back to normal fun and much better. See pics.
                                      Yeah, mine do that too and stall out before fully closing. I upped the BEC voltage to 5.5V without effect on the gear.

                                      My solution has been to take off, gain some speed, flip the gear switch then pull into the vertical. The reduction in speed as it climbs reduces the air pressure and allows the doors to close fully.

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                                      • My solution has been to take off, gain some speed, flip the gear switch then pull into the vertical. The reduction in speed as it climbs reduces the air pressure and allows the doors to close fully.

                                        Thats what I do also. seems to work well.

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                                        • This is nothing new. I had hoped this wasn't the case for the Gripen but I guess I'll have to deal with it. My FMS F7F was so bad, I had to do an inverted pass just to get the nose gear door to close. I've changed retract motors and still the same. Now, I just don't bother and let the door/wheel hang done a bit during flight. The FMS 1700mm Corsair is the same. They need to make stronger retracts.

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