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Feb 21, 2019, 10:41 AM
Mian
Thread OP
Discussion

Mig 29, cg problem


Mig 29:
wing span 32.3"
Length 40"

unable to find its correct CG. please help.

in original PDF its wing is about 28.3" which i extended upto 2" from each side while kept the lenght same. now I have changed its battery place from every point top to botton from cg point but still unable to fly it.

power pack is:
40A esc
2212/6, 2200kv motor turnigy
2.2A Turnigy Battery
2 servos 9gram.

video Link:
Mig 29 CG problem (1 min 16 sec)
Last edited by mian558; Feb 22, 2019 at 02:40 AM. Reason: uploading video
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Feb 21, 2019, 12:20 PM
Build, crash...repeat
AleRRon's Avatar
I don’t know, but where is it right now and what does the plane do when you try to fly it? I think you’re supposed to have something like 1/3 of the wing surface area in front of the CG.
Feb 22, 2019, 02:40 AM
Mian
Thread OP
Quote:
Originally Posted by AleRRon
I don’t know, but where is it right now and what does the plane do when you try to fly it? I think you’re supposed to have something like 1/3 of the wing surface area in front of the CG.
Here it is:
Mig 29 CG problem (1 min 16 sec)
Feb 22, 2019, 08:08 PM
Build, crash...repeat
AleRRon's Avatar
It flies very tail heavy. Move the battery forward to move the CG 1 cm forward at a time and keep test flying until it flies level. But that plane needs speed to avoid stalling too.
Feb 23, 2019, 07:38 PM
Quad Erat Demonstrandum
scousethief's Avatar
I would add weight to the nose (plasticine, blutack, bolt, stone, whatever is handy ) until the plane flies level/how you want. This just saves you cutting any foam or making any unneeded alterations.

When you are happy mark the point were the plane balances. Remove the added weight and move the battery so that it balances the plane at the new CG.
Feb 28, 2019, 07:26 AM
Build, crash...repeat
AleRRon's Avatar
Mian558
Any progress on the proposed adjustments and flying results? We’re eager to hear
Mar 04, 2019, 03:38 AM
Mian
Thread OP
Quote:
Originally Posted by AleRRon
Mian558
Any progress on the proposed adjustments and flying results? We’re eager to hear
thanks for your interest. After changing its battery its movement remain same. now I am going to do two more changes. First making this area Static as i think back control surface area is more than the front wing. Secondly I'm removing these curvy spots which dont looks aerodynamics in this model. Hope it will work. For these changes your suggestion is always welcome. thanks

Mig 29 CG Problem (0 min 39 sec)
Mar 05, 2019, 06:09 PM
Kimbers Keeper.
BHOFM's Avatar
Leave the two curved parts as they are, that helps speed up the air off the prop.
Mar 05, 2019, 11:49 PM
Mian
Thread OP
Quote:
Originally Posted by BHOFM
Leave the two curved parts as they are, that helps speed up the air off the prop.
then why still there is no improvement?
Mar 07, 2019, 12:21 PM
Build, crash...repeat
AleRRon's Avatar
Mian
I looked closely at your pictures and it looks like you have one servo per side, controlling both the aileron and elevator, moving them together at the same time. Is that correct? If so, it'll never fly right. You can't control surfaces like that. You need separate servo controls for the ailerons and elevator.

Also, it looks like your control horns are far behind the hinge lines of the ailerons and elevators. That will probably also make it hard to control. The horns should be placed right at the hinges, like in the drawing below.
Mar 11, 2019, 02:33 AM
Mian
Thread OP
Quote:
Originally Posted by AleRRon
Mian
I looked closely at your pictures and it looks like you have one servo per side, controlling both the aileron and elevator, moving them together at the same time. Is that correct? If so, it'll never fly right. You can't control surfaces like that. You need separate servo controls for the ailerons and elevator.

Also, it looks like your control horns are far behind the hinge lines of the ailerons and elevators. That will probably also make it hard to control. The horns should be placed right at the hinges, like in the drawing below.
Please check this:
R/C Mig-29 ParkJet With Thrust Vectoring (3 min 51 sec)

Using 2 servos for both Aileron and Elevator. But I will definitely apply control horn changes. thanks for replying me.
Mar 11, 2019, 11:22 AM
Build, crash...repeat
AleRRon's Avatar
It may just be my ignorance about jet style aircraft, but it seems to me that in general you want to control the ailerons and elevator separately. But others may have seen or used your setup successfully, I don't really know.

Anyone want to chime in?
Mar 11, 2019, 12:55 PM
Kimbers Keeper.
BHOFM's Avatar
I have several delta tailed with ailerons that work together and fly fine, I have built several of
the Hobbyking SU that have one servo per side and use ailerons that work with the tail.


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