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Official Freewing JAS 39 Gripen 80mm EDF Jet

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  • kallend
    replied
    Originally posted by ArmorBolt View Post

    You must have added at least 4 grams to the rear of the jet for CG 25mm behind the mark. Thanks.
    4g will move the CG about 0.5mm. You need more like 120g.

    "Kallend's Heavy Nozzle" for the Gripen can accommodate up to 60g of lead weights in addition to its own weight.

    The Gripen needs weight in the tail to achieve an acceptable CG position. This nozzle has accommodation for up to 60g of small lead weights, in addition to weighing over 60 grams itself. Print wide-side down, with supports. You will need to peel off the plastic outer of the stock nozzle, and trim back the foam to leave a stub 13mm long to which you glue the new nozzle. I suggest taping the join on the inside to ensure smooth airflow,


    I have a lighter one for the Gripen TV unit too.

    Replaces the cheap looking foam overlay on the vectored thrust nozzle. The foam overlay is glued on with a tacky glue and with care can be pulled off intact. This is a direct replacement. Be aware that it weighs some 30g more than the foam overlay, so be sure to check the CG of the model. I used 3% infill, 3 bottom layers and a 0.8mm thick wall. If you want more weight at the back use more infill and thicker walls.

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  • Airguardian
    replied
    Factory CG sucks, and many of us have pushed CG past 30-40mm behind the marks. And in order to achieve that, one usually needs to add over 130g of tail ballast, there's no way you'd do that with just 3g. I bet there's something else going on with your setup, what else have you done to the jet? Are you using exponentials? Definitely remove the roll from the canards. It's worse than worthless, it will mess up the wing's aerodynamics in high alpha. Are you using a gyro? was it on? how's it set up? Is the thrust vectoring nozzle installed?

    To me, it sounds like you had large throws with no expo and a bad trim. If the TV nozzle is installed, maybe the thrustline is off. Can't tell you much without giving us more info. A video of the maiden would be helpful.

    Leave a comment:


  • ArmorBolt
    replied
    Here's 130mm from MotionRC video..

    Click image for larger version

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  • ArmorBolt
    replied
    BTW, my instruction manual showed CG 122mm behind the rear canard. But there was a video from MotionRC by James I think showed 130mm behind the mark. Which one is accurate. Thanks.


    Thanks. Click image for larger version

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  • ArmorBolt
    replied
    Originally posted by kallend View Post

    Mine balances about 25mm behind the marks and has no tendency to behave in the manner described by ArmorBolt. It flies just fine with the CG there.
    You must have added at least 4 grams to the rear of the jet for CG 25mm behind the mark. Thanks.

    Leave a comment:


  • kallend
    replied
    Originally posted by Evan D View Post
    It will fly at the marks under the wings…
    Mine balances about 25mm behind the marks and has no tendency to behave in the manner described by ArmorBolt. It flies just fine with the CG there.

    Leave a comment:


  • Evan D
    replied
    It will fly at the marks under the wings…

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  • ArmorBolt
    replied
    After viewing this thread, it seems most move the CG back from 10mm - 25mm, I guess you all are advanced flyer or want to perform hi alpha. Just curious, does anyone or does this plane can fly normal level with the factory marking CG. I just want to take the bird up with CG factory, trim out for now.

    Leave a comment:


  • Evan D
    replied
    You’re balanced where I am and I have roll and pitch on canards… but I have TV on two of my Gripens and no TV on the third one. No gyro on any and I love how mine fly. Maybe move the balance up a bit and try again?

    Leave a comment:


  • ArmorBolt
    replied
    OMG, maiden nightmare for me..

    I added 3grams to the rear, and had my CG about 20mm after the mark and my maiden was almost disastrous. After takeoff ,the Gripen went almost vertical with half throttle, hanging 20 feet vertical from the ground. I had to punch the throttle full, and full elevator down to make it level out...the Gripen was flying but I had to compensate with much down elevator. After 2 loops, my buddy (an experience pilot) took the control and was able to land the plane. I had enable canard with my roll so everytime I try to roll, the plane almost tip stall.

    Any recommendation. SHould I just remove the excessive 3g weight and balance the CG at factory marking. That should fly normal, right? Does anyone on this thread able to fly the plane with factory CG marking. Or does everyone here fly it with 20-25mm behind the factory CG. Also should I just disable the canard for turn roll. Thanks.

    Leave a comment:


  • Evan D
    replied
    They changed after the plane was out for about four months. It’s frustrating because all three of mine are the lighter ones and when I bought decals they were the darker ones.

    Leave a comment:


  • Gravythe clown
    replied
    Got my fuse. Only need the steering are and I can get her back in the air.
    I bought the decal set to put on the fuse and watch up to the ones already on the wings and vert. To my surprise the new decals are Black, not faded grayish. So I ended up doing all the black decals. I will say the new black decals really make it pop.
    I thought at first maybe it was sun fade but after looking at the production images I realized, nope they came faded.

    Gravy
    Attached Files

    Leave a comment:


  • rms
    replied
    Got incredible high performance out of my Gripen with a 6s 2280kv motor.. Also the current got high... 180 amps...I was 100% sure my telemetry told me wrong....Got the current meassured of a freind...So I was wrong😉 The beeping is I set a alarm when getting under 19Volt, to save things...Try not to use more than a few second on full burst...Still on the stock FW 100 amp esc...
    Wanted som more of my worn Gripen...Had even to change the wheels, they where almost falling off.... Put a higher pitch fan earlier from FW, increased curre...

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  • Airguardian
    replied
    ^^

    Leave a comment:


  • WarbirdFan66
    replied
    Originally posted by kallend View Post

    Position lights on the IRIS missiles? Where have you seen that?

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    i love a good scale or semi scale looking model, but only to the point were i dont know which way im flying in the air when im liek 200m from field, and the Gripen (and i really like this plane) is not known for her outstanding visibily... so the lights are just there for better visibilty during cloudy days, and they are removable, so are the missles...it seemed like the easiest way to mount light with very visible range to the plane

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  • fetzer
    replied
    Question to Post nr. 2270

    Ist it worth to change to the power unit?

    Thanks Klaus

    Leave a comment:


  • fetzer
    replied
    Question to Post nr. 2271

    Ist it worth to change to the power unit?

    Thanks Klaus

    Leave a comment:


  • Evan D
    replied
    Artistic license added to help him tell the planes attitude and position. I think you can say that anyone that uses those LED lights isn't being scale.

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  • kallend
    replied
    Originally posted by WarbirdFan66 View Post
    I just finished the last stage of my Gripen rework, so here a few pictures. For the guys who wanna see more, i upload the build video in the next few day to my Youtube channel, blue skys
    Position lights on the IRIS missiles? Where have you seen that?

    Click image for larger version  Name:	top-image_web.jpg Views:	0 Size:	141.1 KB ID:	385255

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  • Evan D
    replied
    Yes. I have three Gripens and two (both with TV) have the new EDF unit and reversing 100A ESC. The third is stock, no TV.

    Leave a comment:

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