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Official Freewing JAS 39 Gripen 80mm EDF Jet
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First the book CG at Motion says 130mm but the marks on mine are at 122mm. This is not 122 from the canards but from the wing root. If you measured from the canard you are about 10mm aft of the 122 or 130. I am flying at 150mm from the wing root. 3g, are you really meaning 3g? 3g is almost nothing.
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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.
"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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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.
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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.
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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.
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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?
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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.
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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.
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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
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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...
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Originally posted by kallend View Post
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Question to Post nr. 2270
Ist it worth to change to the power unit?
Thanks Klaus
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Question to Post nr. 2271
Ist it worth to change to the power unit?
Thanks Klaus
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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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Originally posted by WarbirdFan66 View PostI 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
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