-Correx Mig-7 Scratch build- - Page 95 - RC Groups
 Nov 27, 2011, 02:37 AM Envies his own avatar David, where's your CG? If the CG is too far forward, you won't have enough elevator authority to carve through the top of the loop. When you fly inverted, does it require a fairly large amount of "down" elevator to maintain level flight? If so, that's another indication that your CG is too far forward. You might try moving your battery pack rearward and see if loops improve. --Rocky
 Nov 29, 2011, 06:14 AM Registered User Thanks for your reply. We have the cofg set as per the design instructions at 3-1/4" from the trailing edge. This seems to give us good penetration and the aircraft generally flies very good. but we will try shifting the weight backwards. But the CofG is a given point according to the shape of the airframe so moving it would cause bad flying , ballooning and stalling. We will try and see if we can do a loop!
Nov 29, 2011, 12:39 PM
No fuse too fat
Quote:
 Originally Posted by DAVID WILSON Thanks for your reply. We have the cofg set as per the design instructions at 3-1/4" from the trailing edge. This seems to give us good penetration and the aircraft generally flies very good. but we will try shifting the weight backwards. But the CofG is a given point according to the shape of the airframe so moving it would cause bad flying , ballooning and stalling. We will try and see if we can do a loop!
Using a fixed measurement is not totally reliable. If the angle of your wing roots is slightly off then when you put the wing halves together the planform of the finished wing might have a little more or less sweep than what is shown on the plans. That will change the point at which the CG crosses the root. You might try using a CG calculator to see where the CG really should be. The trick is you have to figure out how much sweep your finished wing actually has. What I do is line one LE up to the edge of my workbench, then measure to the tip at the other end, then divide that by 2. The measurement should be taken parallel to the root not 90* to the edge of the table.

Images

Nov 29, 2011, 12:52 PM
No fuse too fat
Quote:
 Originally Posted by DAVID WILSON We have been flying a mig 7 at waitpinga cliffs south aust. Flys very good in a moderate to strong wind. very manouverable just like a wwii fighter. barrel rolls are no problem but are you guys able to do loops? we lose a lot of altitude doing barrel rolls and turns, loops turn into stalls before going over the top. But a very strong fuselage and wing can handle lots of crashes which I am very good at.
I suppose the other thing that might cause this other than CG being off is that if you are flying a light plane in heavy wind, then it might be having trouble penetrating and any movement of the control surfaces causes even more drag. You could try loading it up a bit. If being too light is the issue then adding some weight will help it carry through loops better.
Nov 29, 2011, 07:36 PM
Building with TLAR precision
Quote:
 Originally Posted by DAVID WILSON Thanks for your reply. We have the cofg set as per the design instructions at 3-1/4" from the trailing edge. This seems to give us good penetration and the aircraft generally flies very good. but we will try shifting the weight backwards. But the CofG is a given point according to the shape of the airframe so moving it would cause bad flying , ballooning and stalling. We will try and see if we can do a loop!
The final placement of the CG has to be done in actual flight conditions, by a dive test or inverted flight. Generally, the CG on the plans make a good starting point.

Just my \$0.02

-= Dave
 Nov 29, 2011, 09:10 PM No fuse too fat ... Last edited by slopeiron; Nov 29, 2011 at 10:45 PM.
Nov 30, 2011, 01:38 PM
.....till the wind drops.
Quote:
 Originally Posted by Zenmaniac The final placement of the CG has to be done in actual flight conditions, by a dive test or inverted flight. Generally, the CG on the plans make a good starting point. Just my \$0.02 -= Dave
David,
I agree with all the advice given by all the guys above. I would then do as Dave says. Adjust your CG on the slope. The plan is a good starting point!!
 Dec 04, 2011, 01:59 AM scratch build everything I maidened my correx mig on friday. She rose beautifully and incredibly stable. Aileron authority was a little low, mainly due to my radio settings. Very nice to fly indeed.
 Dec 04, 2011, 05:27 AM .....till the wind drops. Nice Dudley!! Next year you must hook up with the guys in Morgans Bay. They are there now......I could'nt take two weekends off in a row! I am sure Markus will post some pics from their time there when he gets back.
Dec 04, 2011, 09:29 AM
Stirring the pot
Quote:
 Originally Posted by DudleyLeRoux I maidened my correx mig on friday. She rose beautifully and incredibly stable. Aileron authority was a little low, mainly due to my radio settings. Very nice to fly indeed.
All that without a V tail?

Comoon Dudley,
Let's see the 1st V-tail MIG!
Dec 05, 2011, 02:28 PM
.....till the wind drops.
I received these pics from Jean, from Brazil. It is a powered Mig, but because he built so well and it looks so great, I thought I'd post the pics here.
Well done!!
Very very pretty!!

Images

 Dec 06, 2011, 05:10 AM .....till the wind drops. Hey Bakkie, Post some pics from Hermanus!!............PLEASE!
 Dec 06, 2011, 05:56 AM ...missing the PE Slope Rebels hey Jean that is sharp man !
Dec 19, 2011, 06:44 AM
.....till the wind drops.
For those that don'nt cross-thread ....here are some pics from the last day at Hermanus 2011.

Images

Dec 22, 2011, 01:51 PM
Registered User
Howdy all, here's my mig. All 3mm (we can't get 2mm in NZ), 940g, 10x5 prop, 58mm spinner, KDA 22-20L 960kV, 30A ESC, 2200mAh, 4 channel, HXT900's all round, CG at the main spar. I chose to put the aileron servos outside because I was getting too much torque loss to the ailerons on the 1st wing I built (which didn't come out well anyway). I don't know if it was the 3mm not allowing enough flex, or the wire that's available here is too springy, probably both.
Maidened it last night very successfully. Stiff breeze but it just shrugged it off. What an amazing flyer, very stable and easy to fly.
Thanks to all here and elsewhere (especially Dave of course) for posting experiences, vids, stories and details which have all contributed to a great plane.

P.S. That Mig of marcus' above is beautiful! Best colour scheme yet.