Official Freewing JAS 39 Gripen 80mm EDF Jet

[RudyD54]

I finally got my Gripen out again this past weekend after installing thrust vectoring. I had been having a ton of issues with wing rock on my gripen since I got it and it seemed no matter what I did with the roll gain setting on the gyro, I couldn’t get it to calm down in anything above a 5-10 mph wind so I wasn’t really enjoying it or taking it out to the field much. Another pilot out at the field who was flying some larger turbines told me “It’s not your aileron gain, it’s your rudder. What you’re seeing is a Dutch roll. Up the gains for your rudder and you should see it stop.” Well guess what, I got the gain on my Spektrum receiver for the rudder up to 100 and it eliminated the rock almost entirely with no wagging at high speed even though it got really gusty later in the afternoon.

Some of you may already know this but I figured for anyone like myself who just couldn’t figure it out, it’d be good to post up.

I had a ton of fun wringing it out afterwards until my gear door got caught on some tall grass and ripped it halfway off on takeoff. Now THAT made for an interesting flight. I program SAFE on all my Spektrum receivers as a safety net just in case something goes wrong and I was really glad to have it at that point. All the drag from the gear door acting like an airbrake was pulling the plane into a yaw/roll and SAFE gave me enough time to figure out what was going on without having to worry about it taking a dirt nap.

[Airguardian]

There goes my first Gripen video showing hands on Tx, giving an idea of how I go about performing some maneuvers, have fun!

The video also clearly shows gyro operation on the canards, making it clear the canards often point down even when I pitch up, which is exactly how I want them to operate.
Except when they run out of authority and I pitch full-up, then the canards do indeed pitch full-up as they would normally.

Hope that makes it easier to understand for some.

[Airguardian]

Could also install the VT unit already and trim that instead. Plus it makes the jet much more interesting in post-stall! :)

[TangoVector]

I put some more flights on my 90mm Gripen today. I like it, but I flew it after six flights with my re-engined Su35 and it was just not that exciting... But with that being said, I have found that my thrust-line is a little off. Not much but just enough so that at full throttle and high alpha (70deg), I can't get the nose down, until I have some more speed. So I will adjust the tail with a small wedge on top of the fuselage-tail connection. I sort of knew this could happen so the tail is not glued on with too much glue.

I have a 90mm TV nozzle in a drawer, will probably be mounted this winter.

[T-CAT]

Awesome stuff T-CAT! :)

Flew my Gripen today, the first flight was short of savage.

The rest, we filmed some air to air scenes and had to batteries die on me. The first one I managed to land but the second one ended up as an off-field. No great damage but will have to replace the pitch nozzle arm, and the front gear tore off... so I will take the chance to install it in reverse to help CG go a bit more aft. :)

Thanks !

Awe, that’s always a bummer when a battery (or more) fails. That’s excellent news that there isn’t much damage though, and you’ll be back in the air shortly. I’m looking forward to the video .

[Airguardian]

Awesome stuff T-CAT! :)

Flew my Gripen today, the first flight was short of savage.

The rest, we filmed some air to air scenes and had to batteries die on me. The first one I managed to land but the second one ended up as an off-field. No great damage but will have to replace the pitch nozzle arm, and the front gear tore off... so I will take the chance to install it in reverse to help CG go a bit more aft. :)

[T-CAT]

Won't all that weight on the gears hurt the gears?

I’ll find out over time, but I can’t imagine too much load it being placed upon them while in the mounts. These main gear retract forward, so it hanging in the manner it is, they are likely more stable than if the main gear retracted rearward.

[Coconut]

Won't all that weight on the gears hurt the gears?

[T-CAT]

I’m running out of wall space, but had just enough space to fit this Gripen next to the Freewing F-14 as long as it was the opposite orientation. It fits like a glove. In the picture, it makes it appear that the left wing of the Gripen doesn’t clear the room door, but it does.

The miracle of 3D designing and printing makes it possible. I made wall hanger for the main wheels and then a top cover that uses a velcro strap (strap holders built into each printed half) to join both halves to encapsulate the main wheels in the holder. Hopefully it won’t fly off my wall now in small earthquakes, LOL. Unfortunately, I have to think of those aspects when hanging anything on the wall or ceiling, ha-ha.

I also finally got around to installing my wheel hubs caps for the Gripen (I put these hub caps on Thingiverse if anyone is interested), and painted some areas on it to better mimic the full scale.

[Evan D]

Curious as to where I have my CG in a few airplanes and wanting to mark in under the canopy I measured where I am with both my TV'ed on and non TV'ed as well as my new-ish EF 80mm F-16 and, while I was at it my Mig29.

Bothe Gripen are at 142mm gear up and 144mm gear down or 22mm aft of the book value. I feel it's a comfortable spot for me and how I fly them.

The F-16 is at 128mm, 33mm aft of it's book value.

The Mig is about 15-18mm aft of the marks under the wings.

Mostly depends on CG.

With forward CG, canards angled down will not work good enough, you'll end up requiring a lot of elevon trim to compensate which is not ideal... in that scenario, neutral canards will likely work better. But as CG moves aft (past 25-30mm) then the down trim really begins to shine.



Is that really so?
One would think EthOS should have a way to deal with that...
I don't use it myself but will ask a friend that does to see if I can help there.

[Steve Balaam]

Some small successes with my Trim issues. I can disable Trims by using a free Mix then selecting an Analogue Source for the required flying surface rather than just moving the stick to select, as I would in OpenTx. Unfortunately, you lose the ability to program multiple rates on a switch doing it this way. So I've elected to disable the Trims on the Vectored Thrust Unit and just have a single Rate, and have multiple Rates on the Canards and live with the fact I can't disable the Trims. Hopefully, a future update to the Ethos system will improve this issue. Now to figure out how to configure the Gyro Functions. I thank everybody who responded for the help & Advice.

[T-CAT]

Congratulations on the upcoming purchase(s) and have fun with it.

[Airguardian]

Thanks T-CAT, will keep in mind!

[Steve Balaam]

Hi Mshagg, I'm using an SR10Pro but stabilization is disabled at the moment, that's another problem to overcome. I'm using Free Mixes but have maybe got something wrong as I'm getting the Trim operational on the Canards in Pitch and the VT Unit in Trim & Yaw. Would you be kind enough to detail how you set up your mixes for me? I've probably done something stupid along the way.

[mshagg]

I've just set up my Gripen with the Vectoring Unit and Canards on a FRSKY X20S with the new Ethos operating system and 10 Channel Rx. I'm reluctant to test fly it as Ethos doesn't allow me to disable the Trim on my mixes so the Canards and Vectoring unit follow whatever trims I'm applying via the Tx trims which is not recommended . Could I ask if the Gripen can be flown on Elevons alone, I can then apply whatever Trims are required on the pushrods to center the Tx elevon trims before attempting flight with Canards and Vectoring? I've read through the Gripen posts and it's suggested for normal flight the leading edge of the canards should be set approx 5mm down from neutral, have I understood this correctly?

How do you have the mixing set up?
I have three thrust vectored jets set up on X20S/ethos now and haven't had any issues with control surface trim affecting the TV nozzles (using free mixes for each axis on the TV).

Unless you have the canards and TV nozzle slaved to the primary/stabilised pitch/roll on the (I assume) SR10, which might need some outside-the-box thinking.

[T-CAT]

So I hear... the plan is to be able to move into kero mid-term... and I am not trusting one of those birds to a Taranis and OTx, so I had to upgrade!

Ha-ha, 10-4. I updated my previous post with some extra info . Let me know if you ever need additional input on the brand and my experience with it.

[Airguardian]

So I hear... the plan is to be able to move into kero mid-term... and I am not trusting one of those birds to a Taranis and OTx, so I had to upgrade!

[T-CAT]

PS: My friend couldn't recall, on the EthOS trim thing, you'll have to do more digging.
I'm more of an OTx guy, and soon Jeti ;)

I have owned and used five brands of radio's (and multiple radio types within each brand), Airtronics, FrSky (using OpenTX for the OS), Spektrum, Jeti, and PowerBox, in that order and some at the same time as I kept multiple brands. They all had their pros and cons, like anything else. One thing is almost for sure, you'll likely be satisfied with Jeti as your next move. I really enjoy that system, the flexibility of programming is excellent and so is hardware and features within the ecosystem.

A few things to keep in mind when moving to Jeti:

- Look at the switch configuration on the transmitter you intend to purchase to see if it suits your preference, and if not, order other switches and switch nuts from Jeti that is the type you prefer (such as push momentary button vs lever momentary, 3-position vs. 2-position, etc.).
- Be mindful of which of their radios have al-la-cart feature sets or "modules" that can be purchased separately and activated for use. If you don't want certain features, than this may work out well because you can activate and pay for what you need/want. However, some of their radios are sold as full-featured and all modules are active, which I prefer for certain reasons. It depends what you're goals are with the radio and what you think you'll use. The new DS-16 G2 is a great radio and option, comes with all of its modules/features active, and will fulfill many peoples needs, or the DS-24 (although that's a bit older now and curious when they'll release a G2 of that).
- Consider getting their Locking Safety Switch. I use that switch as my "Throttle Cut", and it must be moved up to unlock it before moving it to the either direction, ON or OFF. This works great to eliminate accidentally activating or deactivating the switch (works great in my opinion for electric, fuel, etc. aircraft).
- Consider getting a Brotect HD-Clear screen protector for whichever Jeti radio you select. It fit great, easy to install, looks just like the glass (in my opinion), and has protected it very well. These have been excellent for me, and they usually come in a pack of two for this specific type. There is a vendor I've used in the past, www.protectionfilms24.com, that will likely ship to your area.

[Alpha]

Steve Balaam I agree with Kallend and Airguardian.

Let us know how it goes with your radio setup.

[Airguardian]

I agree with Kallend there. The only reason I see to disable canards is an academic one.

PS: My friend couldn't recall, on the EthOS trim thing, you'll have to do more digging.
I'm more of an OTx guy, and soon Jeti ;)