Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[Airguardian]

You're responding to the guy who designed 13 different nozzles for the Avanti and 7 for the Vulcan.

Ok, I stand corrected!

[Evan D]

All three gear extend aft, so that's right. As I balance gear down at 5-10mm that means for those that do it gear up I'm at 11-17mm...

OK, so i did some accurate checks, no fingers involved. There's not a lot in it but on the recommended CG marks with gear up, as soon as i put the gear down the tail dropped. To balance it again without moving my batteries ended up with the CG about 6-7mm further to the rear. Surprised me a bit as i thought it would go the other way. Anyway, in the end as others have suggested just fly it & set it to your flying style.

[jasmith41]

and there you have it...

[kallend]

I do... but the exact amount should be tested... that would be quite a work... need to print several versions and try them all... a bit of a nuisance for whoever chooses to do it.

You're responding to the guy who designed 13 different nozzles for the Avanti and 7 for the Vulcan.

https://www.thingiverse.com/thing:4785745

[Airguardian]

Do you think 3DP fixed nozzles with modified thrustline (less "up") would be of any value in preventing alpha-lock with aft CG? Would be pretty easy to create.

I do... but the exact amount should be tested... that would be quite a work... need to print several versions and try them all... a bit of a nuisance for whoever chooses to do it.

[jasmith41]

CG? We don't need no stinking CG...🤣

[Dazza18]

OK, so i did some accurate checks, no fingers involved. There's not a lot in it but on the recommended CG marks with gear up, as soon as i put the gear down the tail dropped. To balance it again without moving my batteries ended up with the CG about 6-7mm further to the rear. Surprised me a bit as i thought it would go the other way. Anyway, in the end as others have suggested just fly it & set it to your flying style.

[kallend]

Well, these were the last flights we filmed before I added the VT nozzles...

I made these 3DP cosmetic overlays for the VT nozzles some time ago.

https://www.thingiverse.com/thing:4769774

Do you think 3DP fixed nozzles with modified thrustline (less "up") would be of any value in preventing alpha-lock with aft CG? Would be pretty easy to create.

[jetpltrich]

I fly mine at 17mm aft of wing marks. How accurate can my fat fingers be? +-1-3mm right? I don’t do high alpha just rolls and putts around. If you have it on a CG jig and select gear up the nose will go down due to the mains going forward. Personally, as long as you have the CG as others have suggested you’ll be fine.

Rich

[Evan D]

Since I do my checks gear down and 5-10 behind I wonder how that translates to gear up check?

[kallend]

Ok thanks, i'll start there and see where it goes. Did your final spot end up aft of the recommended CG.

If you search on "CG" in this thread and the RCG thread, you'll see that people are flying it with anywhere from the stock marks to 25mm behind the marks, with the median being around 12mm behind the marks.

With that variation, gear up or down wouldn't seem to make much difference.

[radfordc]

Ok thanks, i'll start there and see where it goes. Did your final spot end up aft of the recommended CG.

Yes, it flys better with the CG 10-15mm aft of the marks on the wing. I added about 50g of lead to the tail and also have two afterburner units. Flys really nice on 5000mah packs that weigh 750g each. Flys OK on 6000mah packs that weigh 850g each. Beware of high alpha maneuvers with the CG aft of the recommended marks.

[kallend]

Gear up gear down, you will notice a difference between the two re: CG.

Rich

I'm sure, but HOW MUCH does it move, and is it significant enough to worry about it?

[jetpltrich]

Gear up gear down, you will notice a difference between the two re: CG.

Rich

[Dazza18]

How much does it move as you raise and lower the gear, ad is that likely to have any noticeable effect on the flight characteristics?

I have only done the CG gear up & with two 6000 packs had no trouble getting in on the marks. This surprised me as i noticed many others had trouble getting there batterys back far enough to obtain the correct CG. I'll check tomorrow with gear down but my guess is it will change requiring me to slide the front pack back further, hence why i was asking it is done gear up or down.

[kallend]

Hi, new to this site & this is my first aircraft with retractable gear. Setting the CG, gear up or down ? Thanks

How much does it move as you raise and lower the gear, ad is that likely to have any noticeable effect on the flight characteristics?

[Dazza18]

Ok thanks, i'll start there and see where it goes. Did your final spot end up aft of the recommended CG.

[Evan D]

I do it gear down just to make it easy to check sitting there. But I determine what I want for a balance point by flying it and then seeing where it is setting on the ground on its gear. I then mark where that spot is under the canopy.

[Dazza18]

Hi, new to this site & this is my first aircraft with retractable gear. Setting the CG, gear up or down ? Thanks

[Airguardian]

Well, these were the last flights we filmed before I added the VT nozzles...