Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[fredmdbud]

"Hmmm... not quite.
In any case, extending the flaps will cause the stabs to produce more negative (pitch-up) lift.

Seems quite the contrary case with the ever-rehashed flaps-causing-pitch-down phenomenon.

Then again, why would would flaps be during high-alpha? After critical angle without the benefit of forward-edge flaps (aka slats), the boundary layer detaches, so the airflow is not "smooth" behind the wing and flap. Plus, at that attitude versus travel direction (ambient airflow), the stabilators would be clear of the flaps.



And at stall, why is there any reason to think the stabilators are aerodynamically effective, either? If there was any forward momentum, they would be a source of air resistance (brake) that should tend to pitch the nose down, especially if in the down-pitch position.

[paulrkytek]

Pity wind tunnels are a bit beyond my £400 limit

[fredmdbud]

Pity wind tunnels are a bit beyond my £400 limit

[GliderGuy]

Something to be mindful of….might warrant a periodic replacement. After well over 1000 flights, the nose gear pin that is internal to the main nose gear shaft and connects to the articulating knuckle snapped. You can’t see this small (about 3 mm dia) shaft unless you take the main shaft apart…or it snaps.

It was a smooth, main gear first, landing but when the nose came down, it kept going down. I thought initially that the servo had an issue. Nope!

I always fly off pavement, so the stress of non-pavement surfaces may cause this metal fatigue to happen sooner.

Replacement is easy…one screw and one Jesus clip. Or….replace the entire assembly.

The “take-away” is, have a spare nose gear assembly on hand.

Photos so you can see what broke. Lucky me….I had a spare nose wheel assembly.

-GG

First….the unbroken assembly:

Now…What broke;

[paulrkytek]

https://www.youtube.com/watch?v=wikjMVWvVhE I suspect this one is definitely beyond my 400 limit, but at least i 1/9th scale would ffit in this one

[fredmdbud]

https://www.youtube.com/watch?v=wikjMVWvVhE I suspect this one is definitely beyond my 400 limit, but at least i 1/9th scale would ffit in this one

Or even a 1/72 scale - just having the general planform should suit the purpose getting an idea of what is happening.

[Airguardian]

Something to be mindful of….might warrant a periodic replacement. After well over 1000 flights, the nose gear pin that is internal to the main nose gear shaft and connects to the articulating knuckle snapped.

Bloody hell... one thousand flights!
You are my hero!

Seems quite the contrary case with the ever-rehashed flaps-causing-pitch-down phenomenon.

How about you try and read (again but properly) what I wrote?

Hmmm... not quite.
In any case, extending the flaps will cause the stabs to produce more negative (pitch-up) lift.
If the nose pitches down when extending flaps, it is not because the stabs are being 'sucked up' but because the pitching moment contribution of the flaps is greater than that of the stabs for that particular condition.

I think I worded it quite clearly.
One thing is the pitching contribution of the wing, and another, that of the stabs.

Extending flaps affects both. Wing will try to ditch nose deeper, stabs will want to pull out of it harder. The net balance of the two added up can be either pitch up or down depending on the flight conditions (flap/stab trim, speed, AoA, CG).

[GliderGuy]

Bloody hell... one thousand flights!
You are my hero!

LOL - I made 30 more total yesterday and today. Love the MiG! Then I had to stop to repair the nose wheel assembly. UGH!

But, you are my hero for making the MiG perform!

-GG

[Airguardian]

I'm trying to get one of my Su airframes to 300... never got any model exceed 300 before!

[GliderGuy]

In case anyone is counting, and to show what a robust design the MiG is…

Roughly, as I do not log RC flights:

MiG was delivered on Sept 11, 2020…or 260 days ago.
Use 80% of the days are flyable = 208 days and that I flew on 80 % of those days = 166 days
On those 166 days, I flew at least 15 times each day = 2490 flights. Half are MiG flights = about 1,200 MiG flights.

One can argue to modify the percentages, but even so….still is a LOT of MiG flights. And…I usually get closer to 25 total flights a day vs 15. Maybe once a month I do about 40 total flights in a day beginning at sunrise! Such a pretty time of day to fly.

RC flying helped me keep my sanity during Covid isolation, for sure. And, my Ex doesn’t care what I do….LOL.

I guess I ended up being the MiG’s design torture tester.

-GG

[fredmdbud]

And how are those batteries holding up? That's 1,200 charge-discharge cycles ... over how many battery pairs?

[mshagg]

Living the dream GG!

[GliderGuy]

And how are those batteries holding up? That's 1,200 charge-discharge cycles ... over how many battery pairs?

Edited...Read #4738 below by Hugh...more/better data points on internal resistance.

Good question -

I baby my batteries. Backstory / Was using Admiral Carbon 5100s and had an internal cell connection failure almost put my F-4 in the ground. So, I reordered a set and was shipped Admiral Pro 6000 batteries by mistake. Still using these. My chargers can read internal cell resistance, and I check regularly.

DETAILS
————-
Starting Charge rate (max my chargers can do): 4.3 A at 100 W/channel
Flight time: timer set to 4 min
Mostly 75% power for 2.5 min with periodic full throttle acrobatics and speed runs
1.5 min throttle at 50% to reduce power consumption.
This profile consumes 3800 mAh to 4100 mAh or about 60% to 65% leaving plenty for aborted landings and resulting in shorter charge times (important for me…gotta spend less time charging).
No cool down period….slap them back on the charger post landing.
Voltage post flight is about 3.7 V to 3.8 V.
Using a set of 10 batteries
Charge time…about 50 min.

RESULTS
—————
Current set of 10 batteries has been flying since 04/2020.
All still fully charge, no laggers for cell voltage.
No swelling.
Internal cell resistances (per cell) currently read between 3.5 milli ohms to 8 milli ohms. I read that 7 to 12 milli ohms is OK and one should consider tossing the battery at 20 milli ohms per cell. These are holding up VERY WELL. Also, consider the AL37 and F-4 flights are harder on the battery used for those single-battery flights.
Resistance is read at full charge and room temp.

SUMMARY
—————
Drawing less out per flight and leaving more in the tank seems to be giving good life performance results. The "slower" charge rate also seems to help extend the life. Typically LiPos give 250 to 350 FULL cycles if drained to 3.3 V. I suggest not doing that. Baby them….leave more in the tank….they will live much longer!

Also, by the time the last battery is used, the first is ready to go again. I have 3 4-channel chargers. The EV-Peak CQ3 100 W/channel chargers are holding up well. My truck’s alternator pants! LOL

-GG

One note about the CQ3 chargers. Early models do NOT have the ability to measure cell resistance even though the manual and overviews say they do. The newer models can read internal cell resistance. I can’t find any model numbers on mine, but the old models have the AC plug located at the bottom of a side panel. The newer models with cell resistance readout have the AC plug at the top of the side panel. The readout is total resistance which must be divided by # cell count.

[mshagg]

If I'm the only one at the field I can be turning 4x6000mah around at 7A charge rates; 20 mins from storage to balanced 4.2v/cell.

...but if there's others present they get upset about me pulling the solar charging facilities down below 13v and setting off the low input voltage alarms on their chargers lol. Nice feature of the UP600 chargers is setting input voltage alarms to ~10v.

[GliderGuy]

If I'm the only one at the field I can be turning 4x6000mah around at 7A charge rates; 20 mins from storage to balanced 4.2v/cell.
.

The UP600 looks like a beast! Do they hold up well in the heat/hot weather?

-GG

[Airguardian]

Roughly, as I do not log RC flights:

I do log each flight, I think it's cool to be able to check the progress and accumulated flight hours, plus helps keeping track of battery life, aircraft past problems, etc.

RC flying helped me keep my sanity during Covid isolation, for sure.

You are not the only one, I am lucky my field is next to home or I would be a mindless babbling fleshbag at this point...

Bonus - Quality spam video:

[kallend]

The UP600 looks like a beast!

-GG

So it should at that price.

[Hugh Wiedman]

My chargers can read internal cell resistance, and I check regularly.

Internal cell resistances (per cell) currently read between 3.5 milli ohms to 8 milli ohms. I read that 7 to 12 milli ohms is OK and one should consider tossing the battery at 20 milli ohms per cell.
Resistance is read at full charge and room temp.

I have 3 4-channel chargers. The EV-Peak CQ3 100 W/channel chargers are holding up well. My truck’s alternator pants! LOL

Great Info GG! Couple of quick questions. I use 2 of the Prodigy610 Quad chargers, which are the exact same thing as your EV-Peak CQ3. Same manual, same specs, same functions and look and operate exactly the same, just a different paint job but both made by the same source. You say your charger reads internal cell resistance, mine doesn't, how does yours. Looked at several videos and technical descriptions of the EV-Peak on line and can't see that it checks individual cell IR. I have to use a Progressive IR meter to do that.

2nd question, I'm no battery guru but I've been testing various batteries for a few years now in search of the "Holy Grail" (an inexpensive, light weight battery with an actual High C). The only batteries that meet that are the SMC batteries, that have an actual C (according to that IR meter) of what is labeled. Virtually all others have been lucky to get to 50% C of what's labeled. The individual cell resistances are in the 1.7 to 2.0 milli ohm range for the SMC batteries. The lower the IR of course leads to the higher discharge (C) capacity. In the 6S 5000-8100 mah size of batteries, HRB's are in the 2.15 to 2.85 range, Roaring Tops in the 2.2 to 2.9 range and the Admiral 6000 Pro (out of 14 that I have) are in the 2.96 to 3.39 range and their 5000 is 3.5 to 4.4 milli ohms. Out of testing over 150 batteries of different manufacturers, mah and C's, 6 milli ohms is the highest I've found (in Venoms, E-Flight, and smaller 3-4S packs.

If you have a 6S 5-8000 mah pack with an individual cell in the 8 milli ohm range, I'd "deep six" it. I think the 7 to 12 range you read about may be only for something like a 4S 3000 25C battery. The 6S 5-6000 mah's should be below 3 milli ohms. Just my opinion though, I'm not the one getting 40-50 flights a day, so there's something to be said for practical application.

[GliderGuy]

Hi Hugh,
Congratulations...you re-discovered marketing hype.

Thanks for the extra data points and info. Good stuff!

In the last paragraph in post 4733 above, I noted this is the case (what you say). Unless yours is a newer model, it won't measure internal resistance...even though the mfg documentation says that it does.


CAUTION....I have no clue as to how accurate the internal resistance measurement circuitry is for the CQ3. Whatever I state and/or find out, it must be viewed as a battery-to-battery RELATIVE comparison...looking for deviants between my batteries. Only if I invest in a good quality internal resistance meter or set up a circuit to do this will we know that my true values are. The values I see MAY BE ALL WRONG!

I happened to order a "spare", and lucked out when I received a newer model that DOES measure internal resistance. The only difference I see is that on the older models, the AC plug connection is on the bottom of the side panel. The newer model has the AC plug located on the top of the side panel.

Now you have me thinking...Next time I charge them (raining today), I will record the total internal values and then do the divide by 6 and post them. My memory could be faulty. I've only been looking for any major changes in value and wanting to stay away from anything over 12 mΩ. So far, that's been the case. But, now you have piqued my curiosity for the "exact".

From memory, I recall that most are reading 23 mΩ total which is about 3.8 mΩ per cell. I think the maximum I have seen is 30 mΩ which is about 5 mΩ per cell. But...i'll re-check and see. I'm either remembering incorrectly the 8 mΩ reading I stated above, or...like you say "it is time to consider replacing" it.

When you get your hands on a CQ3 or Prodigy610 Quad that does measure internal resistance, that option shows up as you scroll through the menu options...quite obviously a selection option. If you don't see it, it ain't there...period. UGH! I just love marketing hype.

RESTATING CAUTION....I have no clue as to how accurate the internal resistance measurement circuitry is. Whatever I state and/or find out, it must be viewed as a battery-to-battery RELATIVE comparison...looking for deviants between my batteries. Only if I invest in a good quality internal resistance meter or set up a circuit to do this will we know that my true values are. The values I see MAY BE ALL WRONG!

-GG

I found the documentation...screen captures shown. I knew I wasn't dreaming. Also showing a photo of the front with Battery IR option showing. This option comes up right after the Battery Meter option as you scroll through the menu. Only one of my 3 CQ3 charges have this option.




https://manualzz.com/doc/36081657/%E...D--1---ev-peak

[Hugh Wiedman]

GliderGuy seeing is believing! Checked mine out and it definitely does not have the IR function. That's certainly a nice feature. Both of mine are a couple years old so they must be the "antique" versions, although my AC plug is on the top of the side panel and not on the bottom, so maybe your 3rd unit is the latest and greatest! Just my luck, I'm usually "a day late and a dollar short". Even so, these quad chargers definitely are nice units and save plenty of time.

As long as your total IR values for 6S 5000-8000 mah batteries are in the 15 to 25 milli ohm range, they should be acceptable for these high current draw EDF's, Since I fly off grass, any thing more and the take-off run is laboring.