Official Freewing JAS 39 Gripen 80mm EDF Jet

[Airguardian]

It is hard to imagine an aircraft with a geometry that has none of that coupling, nor have I ever encountered one yet.

I'm curious as to how the Su-57 would react in that regard, since the way the vertical stabs are canted means they must geometrically generate a fair amount of 'opposite-roll' moment when applying yaw, potentially compensating part of the aerodynamically-coupled, yaw-induced roll. :)

[Evan D]

Flew 8 sets of batteries today dialing it in a bit better. Had a great time with it. Really a special airplane.

[janmb]

Perhaps you've not flown a competition level pattern plane.

I have.

In general you wouldn't notice it much there at all since F3A and similar are flown in the vertical only plane, so you don't do any yawing in wings level orientation at all anyway. But if you try, you will learn that these models follow the laws of physics too.

[kallend]

Obviously neither have I, but it is a matter of fairly basic physics causing this.

Forcing an aircraft to yaw means the inner wing flying slightly slower than the outer wing, which in turn means the inner wing generating less lift than the outer one. Which in turn means that the yaw you commanded also causes roll in the same direction.

It is hard to imagine an aircraft with a geometry that has none of that coupling, nor have I ever encountered one yet.

Perhaps you've not flown a competition level pattern plane.

[janmb]

Well, I haven't flown all aircraft, or even 99% of them, but I think that may be an overestimate based on my experience, both full size and model.

Obviously neither have I, but it is a matter of fairly basic physics causing this.

Forcing an aircraft to yaw means the inner wing flying slightly slower than the outer wing, which in turn means the inner wing generating less lift than the outer one. Which in turn means that the yaw you commanded also causes roll in the same direction.

It is hard to imagine an aircraft with a geometry that has none of that coupling, nor have I ever encountered one yet.

[kallend]

Originally posted by Evan D View Post

"And yaw really effects roll..."

As it does on 99% of all aircraft.

Well, I haven't flown all aircraft, or even 99% of them, but I think that may be an overestimate based on my experience, both full size and model.

[janmb]

As I’ve said before the new TV ball has a lot more authority than previous FW TVs.

Strongly doubt that. The ball itself, and the angles it can produce, is not significantly different from the older 70mm balls.

A perceived experience of this VT having more authority, if at all correct, is probably more down to the rest of the airframe than the VT unit itself.

And yaw really effects roll...

As it does on 99% of all aircraft.

[Evan D]

Before the TVs my Gripen was flying awesome. After I put them on it was still awesome. I did turn the pitch mix down a slight bit but it tracked perfect and had no change in pitch with or off throttle. The only down side was I was going through the battery much faster.

Later last week I went back and cut the nozzle foam and put on the plastic nozzle from the old rear fuselage. I also redid the centering of the TV servos and up’ed the yaw rate.

When I flew it Sunday it was horrible. Flew very nervous and would come out of a pitch flip tilted. Also it dove on throttle and pitched up off. A turn of the ball link fixed the pitch issue and moving the CG forward 3mm calmed the twitching.

Lookin at the TV on the bench maybe glueing the plastic nozzle may have changed the exit just a little. I re centered as best I could and have 8 sets of batteries for today.

Mo better. A tweak here a tweak there and pushed the battery back to the more tail heavy spot and all’s well. Surprisingly even one turn of the yaw ball link on the TV makes a lot of difference in feel. As I’ve said before the new TV ball has a lot more authority than previous FW TVs.

And yaw really effects roll...

[janmb]

I also installed a gyro and I'm finding it to be very sensitive to gain, meaning about the point the gain is high enough to stop the wings from rocking I run into problems at high speed because of too much gain! I'll get it sorted hopefully, or just put up with a bit of wing rock at a lower gain. Also it could really use a speed sensing gain adjustment. The gyro I put in here is overkill really (iGyro SAT) but it has a crazy amount of adjustment potential.

Unfortunately, conflict of interest for gain settings between high vs slow speed is pretty common, and very common for deltas. The rates/gains you need for really slow, high alpha stuff are simply so large that oscillation during normal/fast flight is unavoidable.

The only good solution to that is, as you are already thinking, is IAS input that automatically adjusts the gain. I believe the iGyro actually supports that internally.

For my part, I will be using a standalone IAS and program gain adjustment based on telemetry value from the radio.

[Husafreak]

I finally got some lighter batteries, ZEEE 4000, and it is fun to fly the Gripen with them! Initially I was only flying with 1 lb 12 oz Thunder Power 5000 packs all the way aft and 100g lead on the tail, 4 minute flights. The 4000 packs are much lighter and more fun to fly, losing 30 seconds of flight time is a worthy trade off IMHO, I may slide that 4000 all the way back and lose as much lead in the tail as possible, and regain even more performance. Honestly, I don't find it to be too bad as it is but lighter is better applies especially on this plane.
I also installed a gyro and I'm finding it to be very sensitive to gain, meaning about the point the gain is high enough to stop the wings from rocking I run into problems at high speed because of too much gain! I'll get it sorted hopefully, or just put up with a bit of wing rock at a lower gain. Also it could really use a speed sensing gain adjustment. The gyro I put in here is overkill really (iGyro SAT) but it has a crazy amount of adjustment potential. Some of these MRC EDF jets don't need gyros and some lock in completely with gyros but this one is a bit like my 90mm F-104, it may never be perfect.

[kallend]

Airguardian What I mean is like any man and machine interface, for lack of better terminology, the mind meld with the plane. And yes, maybe some level of feedback in the vortices displayed in the smoke. Maybe?

There's a feedback loop: plane - eyes- brain- hand (stick) - radio - control surfaces - plane (repeat).

The tighter and more accurate the feedback loop the better it "feels".

I have a few planes that "feel" really good, and others where the "feel" is rather sloppy.

[SanExup]

KevinMar Your Gripen looks badass!

[SanExup]

Airguardian What I mean is like any man and machine interface, for lack of better terminology, the mind meld with the plane. And yes, maybe some level of feedback in the vortices displayed in the smoke. Maybe?

[Airguardian]

The low level aerobatics, high speed passes, and high angle banking are the best. Just to get that visual cue, it probably adds to the feel of the inputs?

Thanks!
But what do you mean exactly by 'adding to the feel of the inputs'?
You mean as in the smoke helping to control better the jet?
To some degree, yes... you have more of a 'visual' idea in terms of angle of attack, efficiency of flying and how 'abrupt' the maneuvers or changes in trajectory are, and certainly can use that to fly more smoothly. :)

[TangoVector]

...will be flying Cessna 182's with rocket pods...

-Rocket pods!?! You will be lucky! We will be so poor that the air force will use drones, and not the fancy 5" type, nooo, it will be tiny whoops with little rocks on kamikaze-missions for us.

With a reference to Monty Python

[Mizer67]

Yeah I combed the internet for different pictures of 6002 and it's a dark blueish grey. It changes a lot depending on the light and maybe repaints. It looks a lot like Vallejo 71.304 in some pics, but much darker in ones like this

Agree. Lighting makes it challenging to get a match. I considered Vallejo 71.308 as well. Seemed a little too "purple" to me.

[Pogo]

Yeah I combed the internet for different pictures of 6002 and it's a dark blueish grey. It changes a lot depending on the light and maybe repaints. It looks a lot like Vallejo 71.304 in some pics, but much darker in ones like this

Yes, the lighting makes a huge difference. Such a great looking scheme though, whatever the lighting.
Tom

[Pogo]

Ha! I live in Southern California and fly at a field where it regularly gets above 100F or 37C in the summers 🤪

We get there sometimes too (feels like because of the humidity)- but yours is a dry heat, lol
Tom

[KevinMar]

The actual color isn't black, it's a more of a dark blue-grey. I used Vallejo 71.304 recently and that's a close match.

Probably not much better than black, but hoping the 71.304 doesn't popcorn in the FL summers also.

Yeah I combed the internet for different pictures of 6002 and it's a dark blueish grey. It changes a lot depending on the light and maybe repaints. It looks a lot like Vallejo 71.304 in some pics, but much darker in ones like this

[Mizer67]

I like that scheme a lot and you've rendered it beautifully! I considered it too but the black bits scared me off due to the popcorning. Where are you at- does it get hot?
Tom

The actual color isn't black, it's a more of a dark blue-grey. I used Vallejo 71.304 recently and that's a close match.

Probably not much better than black, but hoping the 71.304 doesn't popcorn in the FL summers also.