F-16 7-blade rear CG and L-39 6-blade (stock motor)
Used the fine but windy weather yesterday to set up my F-16 and L-39, both airframe only kits from HK.
The F-16, with the heavier 7-blade rotor and 2610 Turnigy 3600kV motor in the rear, and only a 850mA 3s lipo in the rear copartment was VERY difficult to fly.
It was pure luck that I saved it on the first flight - see the video. That was 75mm CG or even further back. BTW fixed the ailerons, so it's tailerons only.
The first landing was great, though, so the F-16 clearly likes a rearward CG, but you have to set minimal elevator throws (and a servo with good centering would be necessary I guess).
Reduced throws further as shown in the video, and took a slightly heavier 1000mA 3s Nanotech 25C lipo, still in the (enlarged) rear compartment.
Now it flies fine, still sensitive on elevator, but it should be great for high alpha, I'll try that next time. Unfortunately my fan makes an awful noise when below half throttle, it's the rotor being pulled back by the motor magnets, and it's touching the motor screws.
Otherwise I really like the sound of the 7-blader, it's drawing a bit less than the stock setup, performance is noticeably below a good stock setup using the 6-blade HK fan as I could see just thereafter on the maiden of my L-39.
Fairly balanced, but the RPM make it a screamer compared to the 7-blade (4300kV motor vs 3600kV)
Really like the L-39, it's a great flyer but seldom mentioned in this thread. Got CG fine without lead, just using a 1000mA 3s lipo in front (a bit of foam cutting in the battery bay, and on the canopy latch foam).
PS: I try to get some cool air into my planes. Really easy with the F-16, just drilled holes at the four markings (whatever they are) on the F-16, and inserted small rubber hoses, see attached pics.