Official Freewing JAS 39 Gripen 80mm EDF Jet

[Reaper911]

Ordered one this morning @11am
Got shipping notice @1:52pm
FedEx picked up the package from Motion @2:04pm
Should be at my door next Monday (Canada).
End result .................. Didn't pre-order. Didn't get all worked up waiting for them to arrive at Motion. Didn't get all huffy because they were 5 days past the original ETA. The near perfect purchase. Oh wait! I guess I can still get all worked up and huffy because the VT nozzle is nowhere in sight. OK, "worked up" and "huffy" done with. I can wait till next spring for that. I'm good. GOOD JOB, MOTIONRC!

(Now, just waiting to see how badly FedEx is going to screw me over for fees to collect the duty and tax.)

Nice, that must have been one whopper of a shipping bill! Fedex will for sure rape you ;) Hey, its only money lol. Really unhappy they dropped APC logistics to Canada it was a great affordable service.

[Evan D]

My email was 12:08 but still says label created.

[TangoVector]

The point is to get the canards to behave more scale-like as 'flow-control devices'.
Also the canards can take more gain than the elevons without causing oscillations, since they are closer to CG.

Time for some canard-talk again...

I know about using the canards as flow control devices, but I do think that the Gripen is actually using its relatively large canards more actively in pitch control and not as "flow-control devices". This compared to Typhoon and Rafale where the Gripen is able to turn "cleaner" and faster compared to them or pure deltas like the M2000. Living in Sweden I've grown up with watching deltas perform at airshows, Draken - Double delta and Viggen - Delta with a non moving canard, and they always look like they are "sliding" in the pitch axis since the change of pitch angle comes from the elevons pushing the tail "down". The Gripen on the other hand has no such tendencies since the canards "lifts" the front instead.

Since the Gripen is FBW and uses all its different surfaces to achieve the desired outcome, the control-surfaces might sometimes move counterintuitive but the use of the canards have to my understanding more (only?) to do with pitch-control than main wing airflow-control. Since it is unstable, the canards will at some stages during a steep turn point in the "wrong" direction. This has to do with the control of pitch and not airflow control. The same on slow flybys with no flap selected. With flap selected, they actually point upwards, which makes sense since they are big enough to create lots of lift by their own.

Looking at videos of Gripens landing, the canards are always pointing up, which should not be the case if they were primary for flow-control.

https://www.youtube.com/watch?v=w3qjfeEHJ-U

No need for a long answer, I just think that on the Gripen, the most scale-like thing to do, is to have them do most of pitch and thereby actually point upwards during landing. This can be achieved with a flap selection of down elevon and up canard, but not much! I will be working with that and other canard-stuff when the season starts again in Sweden. Times like these I'm so happy that I'm in the OpenTX habitat

I'm just hoping that with 4000mah batteries and a TV unit I will not need too much lead at the rear to get the desired CG.

Great to see the Gripens start flying! Mine is at home but I'm not

Cheers!
/Tobias

[xviper]

Nice, that must have been one whopper of a shipping bill! Fedex will for sure rape you ;) Hey, its only money lol. Really unhappy they dropped APC logistics to Canada it was a great affordable service.

You know it! I was going to select USPS to save on brokerage on my end with Canada Post but then, the postal service tend to be a bit more rough on their parcels. I paid for the pre-paid brokerage with FedEx (a bit cheaper) but they still find a way to hose me. I did the same thing with my MiG 29 but FedEx ended up charging me 40 bucks just to collect the duty and tax. And here, I thought there was no duty on "hobby supplies". Not worth fighting them for it. Last thing I had delivered from Flex Innovations via UPS, they tried to collect the brokerage from me TWICE! Once online and again at my door. FedEx and UPS are highway robbers and they just love this pandemic when their business is up by XXX%.
Nevertheless, I could have waited for RC Castle to get this plane in but shipping costs from Hong Kong has gone up horribly this past year and they end up using DHL and DHL brokerage is even worse than the other two. Postal can take up to 3 months from Hong Kong.

[Reaper911]

You know it! I was going to select USPS to save on brokerage on my end with Canada Post but then, the postal service tend to be a bit more rough on their parcels. I paid for the pre-paid brokerage with FedEx (a bit cheaper) but they still find a way to hose me. I did the same thing with my MiG 29 but FedEx ended up charging me 40 bucks just to collect the duty and tax. And here, I thought there was no duty on "hobby supplies". Not worth fighting them for it. Last thing I had delivered from Flex Innovations via UPS, they tried to collect the brokerage from me TWICE! Once online and again at my door. FedEx and UPS are highway robbers and they just love this pandemic when their business is up by XXX%.
Nevertheless, I could have waited for RC Castle to get this plane in but shipping costs from Hong Kong has gone up horribly this past year and they end up using DHL and DHL brokerage is even worse than the other two. Postal can take up to 3 months from Hong Kong.

I'm fortunate there is a service that goes to border from Winnipeg and pickups up in Pembina ND. Free shipping from MRC to Pembina, ND and costs $70 cdn plus tax to get it to my door. Decent

[GWatts44]

Just received an email my Gripen will be here Saturday. I will wait for the TV to put it together. Hope they arrive soon.

[T-CAT]

Congrats guys. I’m looking forward to seeing the personal mods. to the aircraft. That’s always my favorite part of the new aircraft releases.

[kallend]

I hid some steel 'square pieces' that I was keeping for ballast purpose in the stock nozzle on the inside, carved a bit of foam, and epoxied them in.
This was not enough though so I also added a large steel rod in the vertical fin and a couple steel sheets in the fuselage foam right underneath the rudder.
Glued them in so they won't mess rudder operation if they came loose.



Thank you!



Yes to all.
I had to open up a canard servo and swap motor and potentiometer wires to reverse it so that this setup would work. I don't like servo reversers! :)

The GWS PG-03 gyro stabilizes the canards (I don't think that can be done with the S8R running elevon mixing?).
I like how this old gyro worked in my Eurofighter so I used one of my spares in this one too.

The point is to get the canards to behave more scale-like as 'flow-control devices'.
Also the canards can take more gain than the elevons without causing oscillations, since they are closer to CG.

Have you decided on a CG position yet?

Fedex says mine will arrive today. Afterburner is ready!

[kallend]

Now this is interesting: The printed manual that came with my kit shows the CG at 122mm while the current online manual has it at 130mm. Both manuals show the same (!) Version No. !

Would MRC please comment?

I checked my model, the moulded marking is at 122mm. Will we get free replacement wings with the revised CG marking? 😁

Hmmm. Those who've flown it already, what did you use?

[noradtux]

Hmmm. Those who've flown it already, what did you use?

Airguardian called the stock CG (122mm) overly nose heavy. So I am going for the 130mm mark.

[Radar-Guy]

A well known German pilot went to 137mm after starting with 122mm. 4500mAh Lipo, he added 80g tail ballast.

https://www.rc-network.de/threads/fr.../post-11861200

[janmb]

I'm just hoping that with 4000mah batteries and a TV unit I will not need too much lead at the rear to get the desired CG.

Tobias, I think that setup will balance well with fairly little if any extra weight at all, depending on how much the VT tail section adds compared to stock.

I built mine with 60g lead embedded in the vertical stab just to have a bit more freedom of choice, but VT should make up for some of that for sure.

[kallend]

A well known German pilot went to 137mm after starting with 122mm. 4500mAh Lipo, he added 80g tail ballast.

https://www.rc-network.de/threads/fr.../post-11861200

Thanks.

Although my stepson lives in Itzehoe, my German is so poor I used google translate. I'll start at 130mm and take it from there.

[kallend]

Big box arrived by FedEx from MRC an hour ago.

I'm off to fly the Eurofighter instead of opening the box. 10/10 for self-control

(but I did make an afterburner for it last night).

[Petronio]

I ended up with 105gr on the tail for a 135mm CG...I will take it from there given the german pilot has already tested it and Jandro also advised the stock CG is waaay front heavy. A pity...I hate having to add more weight for balancing :/.

[Airguardian]

Time for some canard-talk again...

I know about using the canards as flow control devices, but I do think that the Gripen is actually using its relatively large canards more actively in pitch control and not as "flow-control devices".

That's your opinion. It obviously does both, but the 'flow control' is not a marginal thing.

This compared to Typhoon and Rafale where the Gripen is able to turn "cleaner" and faster compared to them or pure deltas like the M2000.

That's questionable. I don't think the Gripen turns any cleaner, it just flies faster at airshows, which makes it 'look' as though it does fly cleaner, but you'd get the same from a Rafale or Eurofighter once they build up speed. This is often said about russian jets too, that they look and feel 'sluggish' when flying in the airshows. For the most part I attribute this to a conscious pilot decision to fly their jets in a particular low speed range.

Living in Sweden I've grown up with watching deltas perform at airshows, Draken - Double delta and Viggen - Delta with a non moving canard, and they always look like they are "sliding" in the pitch axis since the change of pitch angle comes from the elevons pushing the tail "down". The Gripen on the other hand has no such tendencies since the canards "lifts" the front instead.

Lucky you! But this is outright wrong, that's not how it works. The Gripen uses elevons just as the others, and they also push the tail down. The 'ass-drifting' you mention (which personally I think it is beautiful and something to hunt for to make these jets look scale!) has more to do with the speed at which the plane is flying and the aspect ratio of the wings. These deltas have short AR (not efficient at low speeds), which means they require higher angle of attack at lower speeds to keep the same lift, thus it gives that 'drifting-feel' because the jet flies in one trajectory while the nose points at another. Deltas do this more than other aircraft, but then again, you notice it mostly at lower speeds. Gripens purposefully fly faster at the shows for whatever reason, giving the impression that they don't drift as much. But they do.

And the canards on the Gripen, Rafale and Eurofighter are pretty sure always lifting nose up in sustained turn conditions, even when the canards appear to be pitched down. You can visually evaluate canard deflection on videos and judge angle of attack (positive/negative) from the vortices they form. Spoiler alert, they always keep positive AoA, even while pitched down. This is not magic, just a consequence of the geometry of such designs. You ideally want all surfaces on the jet to contribute to lift when possible (this is an advantage of this configuration) while traditional tailed aircraft need to produce down force on the stabs to move nose up (with exception of tail-heavy aircraft, which again can produce positive lift on tail surfaces).

Since the Gripen is FBW and uses all its different surfaces to achieve the desired outcome, the control-surfaces might sometimes move counterintuitive but the use of the canards have to my understanding more (only?) to do with pitch-control than main wing airflow-control.

Not at all. Both are equally important.
If their only purpose was to pitch the aircraft they wouldn't install them and stick to elevons. The fact they use canards is precisely to benefit from flow control first and foremost which helps optimize flight conditions throughout the entire flight envelope, at the cost of a bit of extra drag when not maneuvering and greater radar cross section. Canards have quite a few drawbacks so good reasons are needed to justify their use in spite of the drawbacks. Clearly it's not just for 'picth control' alone. ;)

Since it is unstable, the canards will at some stages during a steep turn point in the "wrong" direction. This has to do with the control of pitch and not airflow control.

That's wrong, yet again.
Yes, the 'tail-heavy' configuration of the fullscale Gripen implies that canards are better suited deflecting down on pitching maneuvers, but that's not just because of the CG placement. I mean you could technically also achieve the same (aircraft turning) by deflecting canards up instead of down and not use the elevons. Not a single one of this canarded delta jets does this in maneuvering flight for many reasons, the most important of them being flow control precisely. Deflecting canards up in such conditions will produce bad flight charateristics, worsen handling, increase drag and instability, etc, etc.

Notice you will never see canards being deflected up in sustastained turns. That's contrary to all that canards are meant to achieve for such a design.
When canards are deflected pitch-up for any long period, it is rather in forward level flight, to compensate pitch trim for the elevons acting as flaps.

The same on slow flybys with no flap selected. With flap selected, they actually point upwards, which makes sense since they are big enough to create lots of lift by their own.

Looking at videos of Gripens landing, the canards are always pointing up, which should not be the case if they were primary for flow-control.

Wrong that too. I already talked about this earlier in the thread but I guess you missed it.
The Gripen uses 'canards-pitch-up' to compensate the elevons acting as flaps. They do this pretty exclusively for landing so the jet can come in at a slower speed while keeping a good pilot view-clearance from the cockpit of the runway in front. Landing in super high alpha (which would be the alternative) is kinda tricky and probably not even possible due to the possibility of tail strikes. The Rafale and Eurofighter seem to have more clearance in this regard. Rafale uses a similar strategy as the Gripen, Eurofighter does not. Many ways to skin a cat, that is. But THIS is not done for normal flying, this configuration is made possible because of the FBW. Don't quite recommend doing that on the model. I will likely try it out myself but you are warned! In any case, this doesn't prove your point that the canards are there just to be 'front elevators'. ;)

No need for a long answer, I just think that on the Gripen, the most scale-like thing to do, is to have them do most of pitch and thereby actually point upwards during landing. This can be achieved with a flap selection of down elevon and up canard, but not much! I will be working with that and other canard-stuff when the season starts again in Sweden. Times like these I'm so happy that I'm in the OpenTX habitat

No need, maybe... but I gave it to you anyway because you are missing many important points on the use of canards on these jets.
Yes, canards pitch up on the Gripen for landing and even take-off but the rest of the time they work differently and so they do on the Rafale and Eurofighter.
Have fun!

[Airguardian]

TangoVector think of it like this... if you bare with me being a little bit more technical it may help your comprehension of canard use on the fullscale jet.

Plane has a global Center of Gravity (CG) and Center of Pressure (CP), which are the points where you could apply the sum of resulting forces acting on the aircraft due to gravity and aerodynamic effects respectively. In that sense, this 'global CP' accounts both for the wings and the canards as well as the fuselage and everything else.

In essence, the jet flies straight when CP and CG position coincide, the jet pitches up when CP goes forward of CG and pitches down when CP is aft of CG. This is straightforward, I hope there are no doubts to this point but please, by all means, do ask if you don't understand.

Now, with this in mind, you gotta picture the aircraft flying level with CP matching CG. As the jet increases angle of attack to pull nose up during a turn or loop (for example), CP gets ahead of CG and jet starts 'pitching up'... but the relation (distance) between CP and CG needs to be kept in check so the plane doesn't over-react. The huge surface of the canards is in great measure determining where that 'global' CP ends up being. Deflecting the canards a bit more or a bit less (not necessarily up and down from neutral line but just small AoA adjustments with respect to airflow) shifts CP forward or aft. So as these jets are unstable (CG very aft), when they pitch up by a certain amount (say 20º) they need to adjust canards (for example, -15º) so that the relation between CP and CG produce the desired turn rate. If jet AoA is 20º and canards are -15º, they are still producing positive lift, as they see an AoA of +5º... they are still lifting nose up while deflected 'down' (the counter-intuitive part), but in pitching -15º, they shifted CP backwards to keep turning conditions under control and not doing a 'cobra maneuver' so to speak.

And in doing so, the canards generate some beautiful and stable vortices that improve airflow over the wings, effectively making the whole wings see a smaller airflow angle of attack (which also boosts lift while reducing drag, among other things). This happens for small deflections of the canards with respect to the airflow. If instead of pitching -15º during a turn, you pitch them up, say, 10º with respect to the fuselage, their angle of attack becomes the sum of the jet's AoA plus canard deflection. In our example, 20º + 10º = 30º
At such a high AoA, the canard surface stalls and airflow detaches from them, making the whole wing 'eat' this bad airflow and the vortices formed, if any, are no longer any good.

That's one of the main reasons why I like to shift CG aft and use a gyro on canards (in these canarded deltas in particular), because that combination does 'almost-naturally' produce canard deflections very similar to those of the fullscale jet.

Hopefully this helps you visualize it in a different fashion that makes more sense. :)

Have you decided on a CG position yet?

Nope... couldn't fly these days, bad weather, will report as soon as I get more flights in but I'm likely not going to achieve my 'preferred' CG with current batteries so you may have to wait a bit for that.


Clearly 130mm is going to be better than 122mm. It felt pretty bad in my case.

[TangoVector]

Airguardian Thank you! Your response sent me on a google-spree to find more information. Found some interesting facts from the autopilot-design on the Saabaircraftindustry homepage, regarding the control surfaces and their functions, and learnt a lot about how it actually works from the people building the full scale version.

[Quickstop]

Wow! You’d think some people are getting paid by the word

[Airguardian]

Airguardian Thank you! Your response sent me on a google-spree to find more information. Found some interesting facts from the autopilot-design on the Saabaircraftindustry homepage, regarding the control surfaces and their functions, and learnt a lot about how it actually works from the people building the full scale version.

Awesome!
My work here is done then!
Really glad my posts produced that effect!
(Also, if you care to share some links I'd appreciate it!)