Official Freewing JAS 39 Gripen 80mm EDF Jet

[rms]

3D printed heavy nozzle can help with the CG. The one I posted can add up to an additional 60 to 120g of weight back there.

https://www.thingiverse.com/thing:4650359

That will help with the CG with bigger batteris. But I like to take weight out if possible.
I use a SLS 6s3500 505g that keep the CG ok. But would like to use bigger 5000 battery..

The front nose is 28g and the cockpit is 78g, Should be easy to take of half of that and even more in the front ;-)
It is also possible to put receiver+ other electronic in the middle in the bodyside wing root outside the duct, cutting out space for it. If cutting the servolead shorter 30-40g goes of.
This way we can remove approx 100g from the plane and CG goes backwards.
Was looking into putting battery further back but the fanduct is the limit, wheels are in the way.

[rms]

OK, but what does that do to the performance in flight? It surely adds a lot of drag.

This was only for testing purpose. But could not replicate the result the day after.
Had to take of all the wheel doors ( snowproblem). Did not find any big performance difference

[janmb]

Sounds good Rudy. I’m at 137 and think it feels a tad tail heavy, try 130 as you are and adjust from there. 130 feels more locked in.

137 is nowhere near actual tail heavy. It is not even neutral. But it is probably a little less nose heavy than you are used to.

CG should not be a means of making a model feel "locked in". Because it comes with a nice set of drawbacks

[rms]

137 is nowhere near actual tail heavy. It is not even neutral. But it is probably a little less nose heavy than you are used to.

CG should not be a means of making a model feel "locked in". Because it comes with a nice set of drawbacks

Sounds good :-)
Back in the days I fly pattern plane. Did put the CG 20-30mm behind the recommendation, so it rolled neutral, and fly inverted neutral. Everybody was arguing that this was not good. But the plane did fly incredible good. Did even put the fueltank as close to CG as possible. The OS Hanno 60 had a realy good pump... ;-)

I gess we cant get the Gripen to be neutral with out major reconstruction or putting a heavy motor in to it. I`m considdering to cut out material in the front...

[rms]

How is the FW Mirage flying compare to the Gripen?

I had a Jet hangar hobbies Mirage/ KFIR "some" 28 years ago... And still like the Kfir. Considering to by a Mirage and modify it to a Kfir.
Do any know if the Jet hangar Hobbies still is in business? Tryed to call an mail them.

[kallend]

How is the FW Mirage flying compare to the Gripen?

I had a Jet hangar hobbies Mirage/ KFIR "some" 28 years ago... And still like the Kfir. Considering to by a Mirage and modify it to a Kfir.
Do any know if the Jet hangar Hobbies still is in business? Tryed to call an mail them.

Mirage is a lot lighter, is faster, climbs and accelerates better. I don't notice the wing rocking on the Mirage either.

Gripen looks cooler, and is easier to land.

I like both of them.

[Gravythe clown]

Yep the mirage would go vertical on take off like a rocket. The guys at the field loved when I did it.
I also had no wing rock with her. She was one of my best fliers. But landings were a little hotter and those damn main doors. I used to always have a spear set of the doors, and when one broke I’d order another set.

I so wanted the Gripen to fly close the the Mirage. I think that’s why I’m so unimpressed now with the Gripen.

Gravy

[kallend]

Yep the mirage would go vertical on take off like a rocket. The guys at the field loved when I did it.
I also had no wing rock with her. She was one of my best fliers. But landings were a little hotter and those damn main doors. I used to always have a spear set of the doors, and when one broke I’d order another set.

I so wanted the Gripen to fly close the the Mirage. I think that’s why I’m so unimpressed now with the Gripen.

Gravy

if you have a 3D printer (or access to one) I can send you a STL file for Mirage doors.

[janmb]

How is the FW Mirage flying compare to the Gripen?

I had a Jet hangar hobbies Mirage/ KFIR "some" 28 years ago... And still like the Kfir. Considering to by a Mirage and modify it to a Kfir.
Do any know if the Jet hangar Hobbies still is in business? Tryed to call an mail them.

The Mirage is way more powerful in every way - but also a bit more limited in how much config you get to play around with (since no canards)

Loved it though - it's one of the few cases where they took a tiny model and put a relatively large power system in it.

[Evan D]

Simply put the Gripen and the Mirage are different. The tiny little sports car Mirage is a plane everyone should try at some point and then try it with more power and heavier and then go back. I have tried four or five different set ups in mine from the first low power 12b 6S to a JF/ HET 8S.

The Gripen just can't match that. But the Gripen has canards that makes it fun in it's own way.

In my opinion it really needs at least 2200W or so. 2700W gets it to the fun level and over 3000W is awesome. As I've said, in my opinion, 135mm is about the best balance once you do a few flights and the stock CG does work for the first flights.

This plane rocks if there's wind similar to the Mirage. No wind no rocking. BTW, I don't fly with AS3X or gyros.

Yep the mirage would go vertical on take off like a rocket. The guys at the field loved when I did it.
I also had no wing rock with her. She was one of my best fliers. But landings were a little hotter and those damn main doors. I used to always have a spear set of the doors, and when one broke I’d order another set.

I so wanted the Gripen to fly close the the Mirage. I think that’s why I’m so unimpressed now with the Gripen.

Gravy

[Captain Moron]

Bloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!

[Gary S.]

I am going to 8s on mine, but its fun to fly stock. True its not fast and must run with over 50% power most of the time which is unusual compared to my other edf's. It lands great looks awesome and is a worthy addition to any fleet, in my opinion. Also I have found and still testing, so no conclusion, that trimming the leading edge of the canards down a few mm seems to increase stability. (Jury still out on that one but so far so good).

[TangoVector]

The Mirage has an 80mm fan in a 70mm airframe and it appears that the Gripen has an 80mm fan in a 90mm airframe.

[Mizer67]

Bloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!

The Gripen in mostly stock form lands like a jet trainer. If you have the CG slightly aft of 130mm, it locks into a high alpha position on its own and all you need to do to land it is control your throttle slightly to get the right decent rate. Rollout is one of the shortest too.

I fly the Mirage a ton and it can't hold a candle to the Mirage in terms of performance. I was also hoping for more of a sports car feel also.

The Gripen is slower and like the Mirage, or Mig bleeds a lot of energy in turns and needs a lot of power to both maneuver and accelerate because it's so heavy.

I think somewhere out there there's a light, high voltage setup that strikes the balance between optimum CG, thrust and weight. Evan may already be close with his (I think) light batteries. When I find it this plane should be a lot of fun. I thought my 8S Jetfan setup flew poorly given the very nose heavy CG, even with 3500 watts on tap. Fixing the CG on mine with heavy batteries adds a lot of weight which creates a vicious circle.

Honestly, my opinion is this is a plane where its performance is primarily kneecapped by it's nose heavy CG. Fixing that requires lots of weight and that has all kinds of negative effects on an already heavy for the size plane.

We need a weight reduction program for the front of the plane as rms was indicating, then perhaps things will start moving in the right direction.

[rms]

Bloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!

The Gripen flys very good. I realy like how it flys. Its very predictable i slowflight high alpha. + good topspeed 180kmt level flight.
The Mirage is a smaler plane and now delivered with the same motor.
My Gripen is 2362gram with some telemetry+ battery. Was 2350g in ad. And the Mirage is advertised to 2200g+ bat.

[Evan D]

I really think 8S shines on this plane. The JF/ HET 1738 or 1865 just work well. The 1738 has a little less power but gets a easy 4:30 on 5000mAh while the 1865 gets you that vertical at 4:00. I really like the Hobby King Plush 120HV. Cheap, small, light, works perfect and good for 8S.

I prefer 6+2 for 8S and can't find any that I really like. The PowerHobby 5000mAh 100C 8S pack is the best I can find for this and is 765g and fits great flat on the battery tray or upright moved back a tad more. There may be a 4+4 option but I have very limited use for 4S 5000 packs.

I agree the #1 thing is weight and balance on this plane. We need a way to get rid of the tail weight we are putting in it. Going to lighter 3500-4000mAh 8s is NOT an option.

[TangoVector]

My Gripen is 2362gram with some telemetry+ battery. Was 2350g in ad. And the Mirage is advertised to 2200g+ bat.

The Mirage is 2200 flying weight, so a difference of at least 600g.

[kallend]

Bloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!

I don't think I wrote anything bad about the Gripen.

It would benefit from more power, but that doesn't make it bad.

[Airguardian]

Also I have found and still testing, so no conclusion, that trimming the leading edge of the canards down a few mm seems to increase stability.

I suggested as much even before getting the plane...

[Evan D]

100% right.

I don't think I wrote anything bad about the Gripen.

It would benefit from more power, but that doesn't make it bad.