Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[RedAlert]

No but I can see me forgetting to raise them. If they correct the issue down the road I will revisit it.
JMO

I agree, it would be nice if they fixed this deficiency. But I wouldn’t deny myself this otherwise wonderful jet. Everyone at our field loves this Mig. I am going to maiden mine this Sunday.
problem or not, JMO anyone should have a flap alarm setup on their radio. I have mine setup on every jet. For years now.

Another solution, as suggested by some pilots, is to put gear and flaps on the same switch.

[Evan D]

GG, you show both upgraded extensions AND the MRC Y. Aren't they the same purpose?

Tomorrow is forecast to be light winds and good weather. I’ll be trying out the MiG’s new configuration which consists of:

- 20 AWG (0.5mm) twisted tail servo drive wires
- MRC supplied Y
- FFS servo control rod on inner servo arm hole
- CG 15 mm aft of wing mark / wheels down
— Since I am using Admiral Pro 6000, this required adding some weight to the tail area (not a lot)
- MRC upgrade servos (they have served me well so far)
- 4 mm of FFS trim removed / We’ll see where the trim ends up after the first flight
- 5 RF chokes (each ESC, each rear servo in the tail and one by the green ferrite ring)

Thanks for everyone’s inputs.

Until I upgrade TX/RX, this is about as far as I can “improve”.

Stay tuned.

-GG

[kallend]

Don't really even need any calculations to see that. It is so obvious/pronounced that anyone can eyeball that fact.

Not true. It is quite obvious that some could not see that.

[GliderGuy]

GG, you show both upgraded extensions AND the MRC Y. Aren't they the same purpose?

Hi Evan - MRC supplies a short (about 5 in) Y with the upgrade servos that is just long enough to reach to the 2 individual FFS drive wires that are about 70 cm in length.

I used these 2 stock wires as “pull” wires and threaded forward the twisted 0.5 mm x 80 cm (20 AWG) from each FFS servo. Then I connected each of these to the MRC-supplied Y then tossed the stock 70 mm servo wires onto my spares box.

So, other than the short Y to connect to the RX, the rest of the FFS drive is “new” “larger wire” “gold contacts” and “twisted”. I did not re-route as some have.

Here is the link....be sure to get the 80 cm length

https://www.hacker-motor-shop.com/Se...ge&rdebox=box1

Here’s a photo of the wire as I began tucking it under the rear battery box. Lots larger diameter than the stock wires. Will help keep the voltage level higher at each rear servo.


-GG

[Evan D]

That’s odd, the Y they gave was about 18” long from memory...maybe I’m mistaken but that’s my memory, I didn’t use it since I had already run better extensions.

[viper1gj]

I am working with my friend Keith (Yellowbird911) to make the Mig-29 a turbine conversion. We are both using the K-45G3 turbine. So far this has been a very easy conversion with a simple turbine mount between the engine nacelles and lots of room on top for all the extra stuff. Not much foam carving is needed. This is possible because we are using an external centerline tank as the main fuel tank. This external tank holds about 45 oz and will feed a 12-14oz header tank in the rear battery compartment and then feed the air trap tank and pump in the nose. Most fuel will be near the CG and its great not to have to carve foam to stuff all the fuel on the inside.

Keith has designed and 3D printed tanks for several foamy turbine conversions before. The process is to print the tank and then coat the inside and outside with epoxy resin. For the Mig-29 he designed a semi scale center line fuel tank from photos that also functions as a FOD shield for the rear undermounted turbine. The tank has anti slosh baffles.

My tank arrived today. At first look it look fits perfect and looks great and scale. Keith will be posting the CAD and 3D print files on Thingiverse so it can be downloaded and printed if desired. This conversion is still a work in progress and I will post a full build thread somewhere when it is complete. For now here are some photos of the 3D printed tank.

Gary

[HangarQueen]

If I may chime in here with a YT video that I just watched:

Elevator flutter, slow motion at 2:15

[janmb]

Not true. It is quite obvious that some could not see that.

Why would you make that assumption? I'm sure both alpha and freewing are perfectly aware of that fact

[kallend]

Why would you make that assumption? I'm sure both alpha and freewing are perfectly aware of that fact

So alpha and freewing are "anyone"?

It is so obvious/pronounced that anyone can eyeball that fact.

[GliderGuy]

If I may chime in here with a YT video that I just watched
Elevator flutter, slow motion at 2:15

Hi HQ - A good example of pushing designs beyond their limits. Something that those using fuel turbine power “may be” more likely to do than those using EDF power.

As we are continuing to sort out the MiG loss of control events....we may also be seeing design limitations coming into play. No flutter, yet. Al least none witnessed. The MiG seems to have an issue with the interplay between flaps and FFS at high speed....imposing significant anhedral of the FFS and loading of the FFS servos.

-GG

[PaulZ]

I mentioned about a week ago about a problem with the MiG. During flight condition with flaps deployed and higher throttle settings, with nose down attitude, the MiG loses elevator control. Please see my previous posts. I was able to reproduce the pitch control instability multiple times. Last Sunday, I had someone take close up burst photos during this maneuver. Unfortunately during my last try, I was not able to pull out of the shallow dive with up elevator input on my transmitter. The MiG was destroyed on impact. I have a picture, moments before impact, that demonstrates a structural problem with this plane. See below. Please note the anhedral configuration of the horizontal stabs. I’m convinced that this is contributing to the loss of elevator control. My advice, please do not fly your MiG with flaps deployed at higher throttle settings

Yup, this is most likely the issue. It makes total sense. Also look at most crash pictures, they have flaps fully deployed. Guys - don't do high speed dives with flaps down and you should have no issues! You shouldn't dive with flaps down anyway...

[Mizer67]

I think the more likely problem to fixing the issue is there are a combination of factors in play.

• Design of FFS that leads to higher required elevator forces
• CG that exacerbates the issue further
• Flap deployment that exacerbates the issue further
• Servos under-spec. for the loads necessary due to the above
• Design of FFS attachments/attachment points leads to flex, causing even higher servo load requirements
• Heat build up caused from the high loads placed on the under spec. servos
• Heat build up causing shut down of the servos, or over torque perhaps
• Stupid pilot tricks that add to servo loads

Not going to be a single fix that eliminates the issue entirely. Freewing's likely not going to change the molds either...that's big $ unless there's a quick milling operation that can address at least some of the issues.

[janmb]

So alpha and freewing are "anyone"?

No, but I assumed your claim that anyone being able to easily see this issue being false was aimed at the very fact that they still chose to design the model this way.

And yes, everyone and anyone *ought* to be able to easily see how imbalanced those surfaces are. Yes, I assumed a bit of intelligence. You might be right.

[kallend]

I think the more likely problem to fixing the issue is there are a combination of factors in play.

• Design of FFS that leads to higher required elevator forces
• CG that exacerbates the issue further
• Flap deployment that exacerbates the issue further
• Servos under-spec. for the loads necessary due to the above
• Design of FFS attachments/attachment points leads to flex, causing even higher servo load requirements
• Heat build up caused from the high loads placed on the under spec. servos
• Heat build up causing shut down of the servos, or over torque perhaps
• Stupid pilot tricks that add to servo loads

Not going to be a single fix that eliminates the issue entirely. Freewing's likely not going to change the molds either...that's big $ unless there's a quick milling operation that can address at least some of the issues.

Putting the FFS pivot axis close to the CP would eliminate most of the above issues. Reducing the loads reduces the servo currents, reduces the heating, reduces the flexing.

I determined the CP of a bunch of other EDF jets having FFS (from Freewing and others). None of them had a pivot axis so far from the CP (as a % of MAC), and none of them are experiencing issues like this MiG.

[Nickc2023]

Putting the FFS pivot axis close to the CP would eliminate most of the above issues. Reducing the loads reduces the servo currents, reduces the heating, reduces the flexing.

I determined the CP of a bunch of other EDF jets having FFS (from Freewing and others). None of them had a pivot axis so far from the CP (as a % of MAC), and none of them are experiencing issues like this MiG.

If this really is the main issue couldn't (shouldn't) motion/freewing sell a new ffs set with a redesigned pivot axis?

[DCORSAIR]

Wow, I love my Freewing jets but I am removing this one from my bucket list. Looks like I will go with the 90mm F-104 for my winter project.

Good idea if you ask me, your going to love the F-104, it was known to crash on the maiden as well but only from pilot error......

Set it up properly and enjoy, not for the faint of heart but a challenge to land at first, had two so far, sold them both because I lost my runway, it does not like windy conditions

[DCORSAIR]

The Mig remeinds me of the old Byron F-16 back in the days of DF, I had the early version and it used the long plastic Sullivan Golden rod for elevator control in the rear of the jet, it was fine for slow speed but failed and flexed at high speed, I was a new to jets and didn't know better that the Golden rod would flex and you would lose elevator authority, yes I crashed mine on maiden, a friend of mine rebuilt it and I flew it a bunch more as I learned to fly jets, I said all that to say this, I then installled an elevator servo in the rear, went to a short stronger 4-40 steel rod and the one thing that was very important on it, you had to balance the stabs, so you guys think something like this may be happening to the Mig, I see some who are mentioning the pivot point of the stabs is off, I also seen some who balanced the stabs as well, just thought I would jump in and give my 2 cents worth, I think the elevator servos just can't overcome the air flow and being not properly balanced, are over powering the servos and causing failure, no I'm not an engineer, I'm a truck driver.............

Maybe I will buy one and install some HV servos and balance the stabs and give it a try.......

[Helijet]

WoW DCORSAIR..we must be of the same era.. That is exactly what happened to my Byron Mig on its maiden in 1980!

cheers
dw

[AirHead]

Yup, this is most likely the issue. It makes total sense. Also look at most crash pictures, they have flaps fully deployed. Guys - don't do high speed dives with flaps down and you should have no issues! You shouldn't dive with flaps down anyway...

Hooray! Your comment and advice has got to be the most relevant and logical comment made on this entire thread....Unless there is some secret I don't know about, flaps are for take off and landing. Dive bombers use special flaps for dive bombing, but otherwise, it would be like a wing suit flier wearing a parachute during high speed flying....BTW: This has nothing to do with it, but I just twisted my ankle in the backyard working on my fence. I guess I'll be looking at this forum everyday, all day for the next couple of weeks. I promise not to make too many comments and maybe I can really learn something....

[kallend]

. . . but otherwise, it would be like a wing suit flier wearing a parachute during high speed flying.......

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