Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[Evan D]

Yes.

How reliable is your “reliable source”? From within the company? Just curious 🤨

[fredmdbud]

So we have two people in the company, Derek in CS and "reliable source", giving contradictory information.

If Derek's information is wrong, that's a black mark for the company for "officially" misrepresenting the facts.

For what it's worth, RC-Castle, another authorized Freewing distributor, has it "out-of-stock". When the 90mm Yak-130 was discontinued, it was tagged as "discontinued", not "out-of-stock".

Guess the rumor mill is daily grist some.

[Captain Moron]

Time will tell

[Levendis]

This one sat in a container for a long time. But it maidened today, and did so majestically.

Early batch. Changes to new freewing “23g” servos. 2.5mm turnbuckle pushrods on the stabs. third hole from the outside to reduce throw on aileron, elevator and flaps. Cg about 8mm rear of factory molded
sign. Jeti rex12 assist...on fairly high gains. Conventional aileron elev no TV no tailerons for now.

Gonna enjoy some formation flights hopefully by next week.

[Levendis]

[ColtPilot]

Fun jet to fly for sure.

[xviper]

I've had fun with mine but I can see where it was NO fun at all when theirs went SPLAAATT!

[GliderGuy]

I've had fun with mine but I can see where it was NO fun at all when theirs went SPLAAATT!

No kidding! However, those flying with the several modifications set forth in this forum and flight profile considerations are continuing to enjoy this awesome EDF.

Levendis....flying with the upgraded FW servos it is a strong suggestion you replace the flying stab servo wires with a larger gauge wire! Also, search on “ferrite” or “choke” or “RF choke” and read/learn and consider installing them. They “might” just prevent a crash. AVOID flying fast with the flaps down!

Below is a list of the mods I elected to employ...so far over 1,000 MiG flights made. But....I also know that it all works until it doesn’t.

MiG mods

• 20 AWG twisted wire to drive FFS servos
• RF chokes on ESC wires, throttle wire near RX, and one near each FFS servo and one on the SR-10 = 6 total
• MKS HV69 servos on FFS (higher torque and lower min operating voltage spec)
• Futaba SR-10 servo reverser...no reverse option for the HV69
• Aluminum foil shielding between ESCs and wiring channel above each ESC
• Cut a small hole ahead of each fan into the inside hollow of the fuselage to suck air from the cockpit and keep things cooler up front...it gets HOT here in the summertime
• Placed a small shim under the cockpit lid to provide an air inlet gap for the fans sucking cooling air into the fuselage hollow
• Added thin carbon sheeting (0.5 mm) to the bottom of the FFS fuselage support structure in the rear mainly to better secure the plastic box
• Beefed up the main gear plastic blocks’ attachment and make them more securely attached to the fuselage...they were working loose
• Bypassed the blue box for elevators. The receiver drives the SR-10, and the SR-10 drives the FFS servos
• Reflexed the flaps so they are about 2 mm up when retracted..many also do the ailerons to match
• Added an anti-collision flashing red LED to the top, a white LED in the rear tip of the fuselage, and an extra landing light on the other side of nose gear strut to prevent visual blanking by the nose gear plastic hardware

My CG is 8 mm aft of factory mark. Added weight to the fuselage rear underside.

-GG

[Shaun Evans]

Nope. If one moment arm is larger then the other ther servo will work harder no matter the force feom the air flow.

HUH??

[Shaun Evans]

If anyone is interested, it took 4 $.25 and 1 $.01 to statically balance the horizontal stab.

Hi

I don't know if this has already been discussed because I haven't finished the thread, but it's not always necessary (or wise) to static-balance a full-flying stab on the pivot unless you know the specifics of the design. If the designer of the airplane applies aero-physics knowledge and principles to the design, he might have put the pivot in a location to optimize aerodynamic balance. Maybe, maybe not, thus knowing how it was designed matters. There are model airplanes out there with full-flying stabs whose stabs are destabilized when you balance them on the pivot.

[kallend]

Hi

I don't know if this has already been discussed because I haven't finished the thread,. . . . . If the designer of the airplane applies aero-physics knowledge and principles to the design, he might have put the pivot in a location to optimize aerodynamic balance. Maybe, maybe not, . . . . .

The FFS are not aerodynamically balanced. In fact that, combined with the forward CG position, is the main reason the elevator servos have to work so hard. It has been discussed extensively.

[Airguardian]

Crazy flights with the MiG. Really pushing the jet to the very limit :p

[Dan McKeag]

Airguardian---where is your CG at now? And I stopped playing your videos when the wife is around because she then asks me why I cant fly like that----


Dan

[GliderGuy]

Crazy flights with the MiG. Really pushing the jet to the very limit :p

MiGnificent!

[Shaun Evans]

The FFS are not aerodynamically balanced. In fact that, combined with the forward CG position, is the main reason the elevator servos have to work so hard. It has been discussed extensively.

Hi,

Thanks. Good to know. Out of curiosity (and I'm still working on finishing the thread, so apologies if it's been answered already)..... how do we know that they're not aero-balanced? I mean, I realize it's a fair and safe assumption--but has anyone involved with the design actually confirmed this?

TIA

[GliderGuy]

Hi,

Thanks. Good to know. Out of curiosity (and I'm still working on finishing the thread, so apologies if it's been answered already)..... how do we know that they're not aero-balanced? I mean, I realize it's a fair and safe assumption--but has anyone involved with the design actually confirmed this?

TIA

Hi Shaun, You will see as you continue reading the posts that in regard to any statements beyond confirming that upgrade servos are being provided...MRC has remained quiet.

To address your specific comment, those who seem to have a good grasp on aerodynamics have shown that this is the case....center of pressure is aft of the pivot point for the MiG.

Keep reading....you will be educated when done.

-GG

[kallend]

Hi,

. . . .

. how do we know that they're not aero-balanced? I mean, I realize it's a fair and safe assumption--

By doing the analysis (it's very basic incompressible flow stuff).

but has anyone involved with the design actually confirmed this?

TIA

They're the people who caused the problems in the first place!

[Airguardian]

Yes, the stabs are not balanced, not mechanically (which you can easily test by holding them on the shaft unsupported: the TE falls down until the stab sits vertically.
And they aren't balanced aerodynamically either, and it's not just an assumption.
Some of us have calculated the position of the center of pressure (with obscure black magic and tricks of wizardry involving pentagrams and daemon summoning) and can confirm it's way aft of the hinge line ;)

Wait... what do you mean "you don't trust demons"?
¬¬

By doing the analysis (it's very basic incompressible flow stuff).

Incomprehensible flow you mean?

MiGnificent!

:')

Airguardian---where is your CG at now? And I stopped playing your videos when the wife is around because she then asks me why I cant fly like that----

Hahahahaha!
Thanks, loved your comment, made me laugh.


CG currently at 15-20mm behind factory marks but planning to move further aft once I install the VT nozzles.

Today we had perfect weather and went to the field to test out some mixes on the MiG.
As some pointed out (Think it was Evan D? Or someone else? Can't recall...) the roll with tailerons on isn't really axial on the MiG which for some things may come handy but for others it's a bit annoying so I added some differential to the stabs on my radio and wow, what a difference!

Jet rolls very axially now, I have it on a switch so I can easily toggle it on/off, but I'm guessing I'll just end up leaving it permanent. Gotta do more testing though. It made nailing flat spins easier too. My differential is set opposite to typical aileron differential. On ailerons you typically want the aileron going trailing edge up to move more than the one going TE down (to reduce adverse yaw among other things), but on the tailerons it is the opposite. The stab going TE down goes more down than the one going TE up when rolling, or rather, what the mix really does is to limit the amount of deflection on the stab going TE-up while leaving the other to deflect down normally. I tested 3 different 'weights': 0%, 20% and 40% (OpenTx mix). All worked well, probably the 40-mix was the better but need more testing to really settle my thoughts on it.

FWIW, I've seen fullscale jets doing this often too, so it's probably a scale move too.

[Shaun Evans]

Hi,

Still working my way through the thread, trying to get 'educated' as someone put it. Very cool and interesting stuff! I've already read a couple of posts that have made me go back and modify my build, so thanks! Seems there's a bit of 'common wisdom' and misinformation (charitably) regarding full-flying stabs, though. I worked directly with an Aeronautical Engineer (Ph.D.) on development with a couple of high-end RC jet models for almost 20 years, and full-flying stabs were a particular focus on one of them. Naturally, there are enough differences between our models and their full-scale counterparts, but some principles are the same. Namely, the fun-fact that if you go out in the world and try to find a full-scale production aircraft equipped with full-flying stabs where the stabs are balanced at the pivot, you would come up rather short since there simply aren't any. That's not coincidental. In the past when I've had this discussion, people bring up hydraulics (and a few other even sillier reasons) as the reason why not a single jet (or even GA aircraft) on earth has a full-flying stab balanced on the pivot, but the fact remains that it comes down to a 'relationship' between the C-of-P and the Center of Lift, then the CG on a stab. Someone mentioned C of P and I got the impression that he thought the C of P is supposed to be where the pivot is, and hopefully I misunderstood that.

A few years ago, we did an experiment with a couple of stabilators from two different makes of F-16. One of them had a stab designed by the engineer I mentioned, and the other was from an ARF whose design (including the airfoils and pivot locations) was basically just blown up from plastic model drawings. One of the questions was 'to static balance or not to', so we did some 'road tests' where we fixed the stab shafts to a length of metal tubing and held it out a car window and observed the behavior at different speeds. The metal tubing was set inside another tube so that it could freely rotate as the wind dictated. The results were surprising unless you already understood the science. The properly designed stab was not balanced on the pivot, but at a certain forward speed required very little effort to deflect it, as it was designed to do just that a la the full-scale. The 'That Looks About Right' stab required significantly more torque to deflect at the same speeds, and was extremely unstable when we simulated disconnecting the control linkage--static balanced or not. The properly designed one weathervaned rock solidly, straight into the wind at all speeds. At 105 m.p.h., it did take a lot of torque to deflect it, though.

All of this is esoteric and random, I know, but I thought some of you might be interested. I definitely wish these ARF manufacturers would save themselves some headaches (and us some money in crashed planes) to just hire an AE to vet some of this stuff. It seems it wouldn't cost any more to manufacture a foam stab that is designed to be aerodynamically balanced and stable at a given speed (the way that the stabs on full-size fighter jets are designed to be balanced at the plane's 'average' speed).

Anyway, back to the build....

[Airguardian]

Hard to tell since you don't mention names but, FWIW, I never said stabs were meant to be balanced on the CP.

This said, installing a stab so that the pivot line is very far from CP will obviously cause a lot of innecessary torque that the servo, servo linkage and servo assembly will have to deal with.